Jeff Mangum's Science and Technical References: Extragalactic

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TIP Last Update: JeffMangum - 27 September 2012

Starbursts and ULIRGs

(From Desai etal. (2008))

An important goal in extragalactic astronomy is to understand when, where, and how the stellar content of the universe formed. Based on rest-frame ultraviolet (UV) and optical measures, the star formation rate per comoving volume is approximately constant from z ~= 6 to z ~= 2 and then smoothly decreases by a factor of 10 until the present epoch (Gallego et al. 1995; Lilly et al. 1996; Madau et al. 1996; Connolly et al. 1997; Treyer et al. 1998; Flores et al. 1999; Steidel et al. 1999; Wilson et al. 2002; Giavalisco et al. 2004). There is also increasing evidence that galaxies with large stellar masses formed most of their stars earlier than lower mass galaxies (Tinsley 1968; Cowie et al. 1996; Heavens et al. 2004; Juneau et al. 2005).

Observations of the far-infrared background radiation with the Cosmic Background Explorer (Puget et al. 1996; Fixsen et al. 1998; Hauser et al. 1998; Dwek et al. 1998; Lagache et al. 1999; Lagache & Puget 2000; Finkbeiner et al. 2000) show that the infrared energy density is comparable to the combined UV, visible, and near-infrared energy density, indicating that half of the light originally emitted in the UV and optical has been intercepted by dust, reprocessed, and reemitted in the infrared (Gispert et al. 2000). What kinds of galaxies contribute to the infrared peak in the extragalactic background light? The earliest mid-infrared observations of extragalactic sources revealed a class of galaxies which emit the bulk of their luminosity in the infrared (Low & Kleinmann 1968; Kleinmann & Low 1970a, 1970b; Rieke & Low 1972). Early observations with the Infrared Astronomical Satellite (IRAS) showed that luminous infrared galaxies [LIRGs; ] and ultraluminous infrared galaxies (ULIRGs; ) do not contribute substantially to the total infrared emission in the local (z < 0.05) universe (Soifer & Neugebauer 1991).

However, there is strong evidence that infrared-bright populations become more significant at higher redshift. This evidence includes number counts obtained with IRAS (Hacking et al. 1987) and the Infrared Space Observatory (Oliver et al. 1997; Altieri et al. 1999; Aussel et al. 1999; Elbaz et al. 1999; Gruppioni et al. 2002; Metcalfe et al. 2003). Spectroscopic follow-up of these sources has directly confirmed the increasing significance of the infrared-bright population out to z ~ 0.3 (Kim et al. 1998; Serjeant et al. 2001), a redshift set by the sensitivity limits of the existing mid-infrared surveys. Progress in constraining the population of infrared-luminous galaxies at higher redshift has been made via surveys at submillimeter (e.g., Smail et al. 1997; Chapman et al. 2001; Blain et al. 2002) and radio (Cowie et al. 2004) wavelengths. These data provide further evidence of strong evolution in the infrared-luminous population, but the number of sources probed are small, and may suffer from selection biases. For instance, spectroscopy of submillimeter sources has relied on accurate positions obtained from radio counterparts, biasing spectroscopic samples to sources that are bright in both the submillimeter and the radio (Chapman et al. 2005). The sensitive Multiband Imaging Photometer for Spitzer (MIPS; Rieke et al. 2004; Werner et al. 2004) has allowed the detection of many faint infrared sources. Number counts at 24 determined by Spitzer observations confirm the strong evolution previously observed in the infrared-luminous population (Chary et al. 2004; Dole et al. 2004; Marleau et al. 2004; Papovich et al. 2004).

SMG Evolutionary Scenarios

(From Menedez-Delmestre etal. 2009, ApJ, 699, 667)

It is over a decade since the discovery of a population of high-redshift galaxies identified through their submillimeter (submm) emission (Smail et al. 1997; Barger et al. 1999; Eales et al. 1999; Bertoldi et al. 2000; Cowie et al. 2002; Scott et al. 2002; Borys et al. 2003; Webb et al. 2003; Coppin et al. 2005; Younger et al. 2007). Their submm selection suggests that these are strongly star-bursting systems. With implied star formation rates (SFRs) of ∼100–1000 M⊙ yr−1, these dust-enshrouded submm galaxies (hereafter, SMGs) may make a significant contribution to the global SFR density at z ~ 2–3 (Chapman et al. 2005, hereafter C05). The absorbing dust that makes them such prodigious submm emitters also makes them quite optically faint and renders follow-up studies at shorter wavelengths challenging. The study of SMGs has been facilitated by the detection of a large fraction of them as μJy radio sources (Ivison et al. 2002) and more recently through millimeter wave interferometry. This has allowed the subsequent measurement of their spectroscopic redshifts for fairly large samples (C05).

With a mean redshift of ⟨z⟩ ∼ 2.2, the redshift distribution of the radio-identified SMGs in C05 coincides with the globalnear-IR and X-ray studies. Near-IR spectroscopy by Swinbank et al. (2004) shows that broad Hα lines (FWHM >~ 1000 km s−1 ) are often present in these galaxies, while deep X-ray studies using the sensitive Chandra Deep Field-North (CDF-N) Survey suggest that at least ∼28%–50% of SMGs host an obscured AGN (Alexander et al. 2005). A number of SMGs that display no AGN signatures in the rest-frame optical (Swinbank et al. 2004) were classified as AGNs based on X-ray observations (Alexander et al. 2005). This is likely due to geometrical effects in which the broad-line region of the AGN remains hidden in the optical by intervening obscuring material. At high X-ray energies, direct X-ray emission is detectable through even very high column densities, allowing the direct detection of an AGN at very high obscurations. However, Alexander et al. (2005) find that the majority of AGNs in SMGs are more modestly obscured, with column densities of NH >~ 10^(23) cm−2 . A similar mix of AGNs and starburst activity is seen in local ultraluminous infrared galaxies (ULIRGs, with total IR luminosities LIR >~ 10^(12) L⊙; Soifer et al. 1987; Sanders et al. 1988), most of which have been shown to be composite AGN–starburst systems (e.g., Armus et al. 2007). The SMGs have IR luminosities which are comparable to ULIRGs at low redshift, prompting the question as to whether SMGs are high-redshift analogs of ULIRGs and hence whether we can learn about the physical processes within SMGs from studies of local ULIRGs (Tacconi et al. 2008).

The potential presence of luminous Compton-thick AGNs (NH >~ 10^(24) cm−2 ) in those SMGs with no X-ray AGN signature remains a significant caveat to these results. Furthermore, the samples of SMGs with the necessary ultradeep X-ray observations to reveal the presence of highly obscured AGNs are still small. Hence it is possible that a small fraction of luminous, but Compton thick, AGNs lurk within the SMG population (see Coppin et al. 2008). Rest-frame optical emission provides direct insight into the stellar emission and ionized gas of a galaxy, but suffers from obscuration due to intervening dust. At longer wavelengths, the mid-IR emission arising from the dust itself provides an indirect insight into the dust-enshrouded nature of SMGs and suffers from much less obscuration than the shorter, optical wavelengths. We therefore designed a program to follow up a large sample of 24 SMGs in the mid-IR using Spitzer’s Infrared Spectrograph (IRS; Houck et al. 2004) in an effort to answer the following questions for a large and representative sample of the SMG population: Are SMGs composite AGN–starburst systems? To what extent does AGN activity contribute to the total infrared output of these galaxies? Is there a spectrum of varying levels of AGN activity across the population? Are local ULIRGs good analogs for the mid-IR emission of SMGs?

The main components contributing to the mid-IR spectrum of a galaxy are: thermal dust continuum, emission from vibrational modes in polycyclic aromatic hydrocarbons (PAHs) and other atomic and molecular lines. The continuum emission at longer mid-IR wavelengths, λ >~ 12 μm, arises from emission by very small grains of dust (VSG; <~ 10 nm) found around obscured AGN or star-forming regions. This is often referred to as the VSG continuum, or the warm dust continuum (TDust >~ 250 K). At shorter wavelengths, λ <~ 6 μm, the continuum traces emission from dust heated to significantly hotter temperatures (TDust >~ 500 K) likely due to its close location near an AGN or possibly a hot, nuclear starburst region. This is what we refer to as the hot dust continuum. PAH molecules (<~ few nm) consist of chained benzene rings, associated hydrogen, and other trace elements, such as Si and Mg. The line emission in the mid-IR waveband is dominated by PAH molecules which are excited by the UV photons that are copiously available in star-forming regions. The main PAH emission features arise from the bending and stretching of skeletal C–C or peripheral C–H bonds and are observed at rest frame 6.2, 7.7, 8.6, 11.3, 12.7, and 17 μm (e.g., Draine & Li 2007). It has been shown locally that stronger PAH features are associated with regions of intense star formation (Helou 1999).

With the unprecedented sensitivity of Spitzer IRS, it has been possible to explore the mid-IR region of galaxies at high redshift down to continuum levels of S(24) μm >~ 0.1 mJy (e.g., Yan et al. 2005, 2007; Lutz et al. 2005, 2007; Desai et al. 2006; Rigopoulou et al. 2006; Teplitz et al. 2007; Siana et al. 2008). At lower redshifts, investigation of the mid-IR properties of local galaxies with IRS provides for a sample of detailed templates against which high-redshift sources can be compared (e.g., Spoon et al. 2004; Armus et al. 2004, 2006, 2007; Weedman et al. 2005; Brandl et al. 2006; Sturm et al. 2006; Desai et al. 2007). A wide range of mid-IR spectra has been uncovered for high-redshift sources, ranging from continuum-dominated spectra with no PAH features to PAH-dominated spectra (e.g., Weedman & Houck 2008). Between these two extremes, there is a myriad of composite spectra displaying a significant continuum with superposed PAH features (e.g., Yan et al. 2007).

We presented the Spitzer IRS results for the first five SMGs observed in the program in Menendez-Delmestre et al. (2007), which complemented earlier IRS results for two SMGs at z ∼ 2.8 presented by Lutz et al. (2005). Since then Valiante et al. (2007) and Pope et al. (2008) obtained IRS spectra of nine SMGs in blank field and cluster lens surveys and of 13 SMGs from the GOODS-North Field, respectively.

Summary of Cold Mode Accretion

(From Carilli, C. L. et al. 2010, ApJ, 714, 1407)

An alternative model, known as CMA, or stream fed galaxy formation, has recently been proposed to explain secular star formation (i.e., on timescales >10^8 yr) in more populous, normal star-forming galaxies at z ~ 2 (Dekel et al. 2009; Keres et al. 2009). In the CMA model, gas flows into galaxies from the intergalactic medium (IGM) along cool, dense filaments. The flow never shock-heats due to the rapid cooling time, but continuously streams onto the galaxy at close to the free-fall time. This gas forms a thick, turbulent, rotating disk which efficiently forms stars across the disk, punctuated by giant clouds of enhanced star formation on scales ~ few kpc. These star-forming regions then migrate to the galaxy center via dynamical friction and viscosity, forming compact stellar bulges (Genzel et al. 2006; Genzel et al. 2008; Bournaud et al. 2008a, 2008b; Elmegreen et al. 2009). The CMA process can lead to relatively steady and active (~100 Msun yr–1) star formation in galaxies over timescales approaching 1 Gyr. The process slows down dramatically as gas supply decreases, and the halo mass increases, generating a virial shock in the accreting gas. Subsequent dry mergers at lower redshift then lead to continued total mass buildup, and morphological evolution, but little subsequent star formation (Hopkins et al. 2009; Naab et al. 2009). Observations of intermediate redshift (z ~ 2), normal star-forming galaxies support the CMA model (Genzel et al. 2006, 2008; Daddi et al. 2008, 2009b, 2010a; Tacconi et al. 2010).

General Starburst, AGN, and ULIRG

  1. Dicken, D. etal. 2012, ApJ, 745, 172, "Spitzer Mid-IR Spectroscopy of Powerful 2 Jy and 3CRR Radio Galaxies. I. Evidence against a Strong Starburst-AGN Connection in Radio-loud AGN"
  2. Crocker, A. etal., 2012, MNRAS, 421, 1298, "The ATLAS-3D Project - XI. Dense Molecular Gas Properties of Co-Luminous Early-Type Galaxies"
    • Except for NGC1266 HCN and HCO+ is very weak in this galaxy sample.
  3. Kazandjian, M. V. etal., 2012, A&A, in press, "Diagnostics of the Molecular Component of PDRs with Mechanical Heating"
  4. Venemans, B. P. etal., 2012, ApJL, in press, "Detection of Atomic Carbon [CII] 158 micron and Dust Emission from a Z=7.1 Quasar Host Galaxy"
  5. Decarli, R. etal. 2012, ApJ, in press, "Ionized Nitrogen at High Redshift"
  6. Donoso, E. etal. 2012, ApJ, 748, 80, "Origin of 12 μm Emission across Galaxy Populations from WISE and SDSS Surveys
    • Find that most (~80%) of the 12 micron emission in star-forming (SF) galaxies is produced by stellar populations younger than 0.6 Gyr. In contrast, the 12 micron emission in weak active galactic nuclei is produced by older stars, with ages of ~1-3 Gyr.
    • Suggests a picture where galaxies form stars normally until an AGN (possibly after a starburst episode) starts to gradually quench the SF activity. We also find that 4.6-12 micron is a useful first-order indicator of SF activity in a galaxy when no other data are available.
    • Note that WISE is about 100 times more sensitive at 12 micron than IRAS.
    • Find that SF galaxies are forming stars at an approximately constant rate per unit mass for an IR output ranging over five orders of magnitude.
  7. Elitzur, M. 2012, ApJ, 747, L33, "On the Unification of Active Galactic Nuclei"
    • Basically throws into question the basic notion that the difference between type 1 and 2 is not just due to torus covering factor.
  8. Izotov, Y. I., Guseva, N. G., Fricke, K. J., and Henkel, C. 2011, A&A, 536, L7, "Star-Forming Galaxies with Hot Dust Emission in the Sloan Digital Sky Survey Discovered by the Wide-Field Infrared Survey Explorer (WISE)"
    • Hot dust in what appear to be starburst galaxies that have recently gone through a starburst episode.
  9. P. A. R. Ade, etal. 2011, A&A, 536, A13, "Planck Early Results: XIII. Statistical Properties of Extragalactic Radio Sources in the Planck Early Release Compact Source Catalogue"
    • Measure spectral index steepening, which is tentatively explained as due to electron ageing or by the transition to the optically thin regime.
  10. Koulouridis, E. etal. 2011, ApJ, in press, "The Activity of the Neighbors of AGN and Starburst Galaxies"
    • Close encounters activate a sequence where a normal galaxy becomes first a starburst, then a Sy2, and finally a Sy1.
    • The Neighbors of Sy2 galaxies are systematically more ionized than the neighbors of Sy1s, a fact that indicates differences in metalicity, stellar mass, and star formation history between the two samples.
  11. Papadopoulos, P. P. etal. 2011, ApJ, in press, "The Molecular Gas in Luminous Infrared Galaxies I: CO Lines, Extreme Physical Conditions, and Their Drivers"
    • Multi-transition CO analysis of n and Tk.
    • Claim high n(H2) >~ 10^5 cm^(-3) and Tk >~ 100 K.
    • Overstate usefulness of this analysis.
  12. Garcia-Burillo, S. etal. 2011, A&A, in press, "Star Formation Laws in Luminous Infrared Galaxies: New Observational Constraints on Models"
    • Use HCN 1-0 as a proxy for dense gas.
    • Find that efficiency of star formation in the dense molecular gas of extreme starbursts is a factor of 3-4 higher compared to normal galaxies.
  13. Whitaker, K. E. etal. 2011, ApJ, in press, "A Large Population of Massive Compact Post-Starburst Galaxies at Z > 1: Implications for the Size Evolution and Quenching Mechanism of Quiescent Galaxies"
    • The observed number densities of young and old quiescent galaxies at z>1 are consistent with a simple model in which all old quiescent galaxies were once identified as post-starburst galaxies. We find that the overall population of quiescent galaxies have smaller sizes and slightly more elongated shapes at higher redshift, in agreement with other recent studies. Interestingly, the most recently quenched galaxies at 1<z<2 are not larger, and possibly even smaller, than older galaxies at those redshifts. This result is inconsistent with the idea that the evolution of the average size of quiescent galaxies is largely driven by continuous transformations of larger, star-forming galaxies: in that case, the youngest quiescent galaxies would also be the largest. Instead, mergers or other mechanisms appear to be required to explain the size growth of quiescent galaxies from z=2 to the present.
  14. Izotov, Y. I. etal. 2011, A&A, 536, L7, "Star-Forming Galaxies with Hot Dust Emission in the Sloan Digital Sky Survey Discovered by the Wide-Field Infrared Survey Explorer (WISE)"
  15. Alonso-Herrero, A., 2012, ApJ, 744, 2, "Local Luminous Infrared Galaxies: II. Active Galactic Nucleus Activity from Spitzer/Infrared Spectrograph Spectra"
    • Bulk of IR luminosity in LIRGs due to SF, not AGN
  16. Beck, R. 2011, "Magnetic Fields and Gas Flows Around Circumnuclear Starbursts", To be published in 'The Central Kiloparsec in Galactic Nuclei - Astronomy at High Angular Resolution 2011', Journal of Physics Conf. Ser., IOP Publishing
  17. Rowlands, K. etal. 2011, MNRAS, in press, "Herschel-ATLAS/GAMA: Dusty Early-Type Galaxies and Passive Spirals"
    • Conclude that:
      • Early Type Galaxies (ETGs) detected by Herschel are atypical compared to optically-selected ETGs. Herschel-detected ETGs have significantly more dust.
      • Only a small fraction of ETGs detected by Herschel (24%) show starbursts.
      • About 31% show evidence for interaction.
      • Appears that dust in Herschel-detected ETGs cannot be solely from stellar sources, and a large contribution from dust formed in the ISM or external sources is required.
  18. Popesso, P. etal. 2011, A&A, 532, A145, "The Effect of Environment on Star Forming Galaxies at Redshift 1. First Insight from PACS"
    • Note that this is a paper about density of galaxies and not galaxy density.
  19. Kartaltepe, J. S. etal. 2011, ApJ, in press, "GOODS-Herschel & CANDELS: The Morphologies of Ultraluminous Infrared Galaxies at z~2"
    • Conclusions:
      • Visual morphological classifications of the ULIRG sample using high resolution NIR imaging indicate that they have roughly the same fractions of disks and spheroids as the z ∼ 2 comparison sample. However, there are significantly more ULIRGs clas- sified as irregular or interacting. Over 70% of the ULIRG sample is classified as a merger, interaction, or irregular, compared to 32% of the comparison sample.
      • At z ∼ 1, galaxy morphology is tightly correlated with LIR, as has been observed locally. The frac- tion of objects classified as disks declines systemat- ically with luminosity while the fraction of mergers and interactions increases. The morphologies of the z ∼ 2 ULIRGs have very similar fractions to objects at z ∼ 1 with comparable luminosity.
      • We identify 52 z ∼ 2 LIRGs and ULIRGs as star- bursts based on their elevated specific star for- mation rates relative to the main sequence. The morphologies of these starbursts are dominated by mergers and interactions (50%) while disks make up only 42%. Among these disks, many have irreg- ular morphologies. It is possible that the combi- nation of objects classified as both disks and either irregular or interactions represent early stage inter- actions and minor mergers. Taken together, up to 73% of starbursts could be interacting or merging at some level, with a significant contribution from minor mergers.
      • (U)LIRGs on the main sequence are dominated by non-interacting disks (57%) but a significant frac- tion are mergers or interactions (24%). These ob- jects are either at an early stage and have not yet reached the starburst phase or they lack the re- quired gas densities to become true starburst systems.
  20. Pierce, C. M., Ballantyne, D. R., and Ivison, R. J. 2011, ApJ, 742, 45, "Radio Stacking Reveals Evidence for Star Formation in the Host Galaxies of X-ray Selected Active Galactic Nuclei at z < 1"
  21. Rujopakarn, W. etal. 2011, ApJ, 726, 93, "Morphology and Size Differences Between Local and High-Redshift Luminous Infrared Galaxies"
    • Show that the star-forming regions in high-redshift LIRGs, ULIRGs, and SMGs have similar physical scales to those in local normal star-forming galaxies.
    • The intensely star-forming regions of local ULIRGs are significantly smaller than those in their high-redshift counterparts and hence diverge significantly from this correlation, indicating that the ULIRGs found locally are a different population from the high-redshift ULIRGs and SMGs.
  22. Walter, etal. 2011, ApJ, 730, 18, "A Survey of Atomic Carbon at High Redshift"
  23. Imanishi, M. etal. 2011, ApJ, 141, 156, [[]["Subaru and Gemini High Spatial Resolution Infrared 18 micron Imaging Observations of Nearby Luminous Infrared Galaxies"}
  24. Hopkins, P. F. 2011, MNRAS, in press, "Dynamical Delays Between Starburst and AGN Activity in Galaxy Nuclei"
  25. Sargsyan, L. etal. 2011, ApJ, 730, 19, "Infrared Spectra and Spectral Energy Distributions for Dusty Starbursts and Active Galactic Nuclei"
  26. Popesso, P. etal. 2011, A&A, in press, "The Evolution of the Star Formation Activity Per Halo Mass Up To Redshift ~ 1.6 as Seen By Herschel"
    • Measure the evolution of the total star formation rate per unit total halo mass from z = 0 to 2.5.
    • Find that this quantity evolves with z.
    • This quantity is also lower for higher mass systems.
    • Supports scenario whereby star formation quenching occurs earlier in galaxies embedded in clusters, then in groups, and finally in the field.
  27. Leroy, A. etal, 2011, ApJL, 739, L25, "Complex Radio Spectral Energy Distributions in Luminous and Ultraluminous Infrared Galaxies"
    • Derive spectral indices alpha simeq -0.67+-0.15, typical of nonthermal (synchrotron) emission from star-forming galaxies.
  28. Luo, B. etal. 2011, ApJ, 740, 37, "Revealing a Population of Heavily Obscured Active Galactic Nuclei at z ≈ 0.5-1 in the Chandra Deep Field-South"
  29. Bendo, G. J. etal., 2011, MNRAS, "Investigations of dust heating in M81, M83, and NGC 2403 with the Herschel Space Observatory"
    • Conclude that the dust emission at >250 micron originates predominantly from a component that is colder than the dust seen at <160 micron and that is relatively unaffected by star formation activity.
  30. Rodighiero, G. etal., 2011, ApJL, 739, L40, "The Lesser Role of Starbursts in Star Formation at z = 2"
    • Conclude that merger-driven starbursts play a relatively minor role in the formation of stars in galaxies, whereas they may represent a critical phase toward the quenching of star formation and morphological transformation in galaxies.
  31. Trippe, S. etal. 2011, A&A, 533, A97, "The Long-Term Millimeter Activity of Active Galactic Nuclei"
  32. Alonso-Herrero, A. etal. 2011, "Local Luminous Infrared Galaxies. II. AGN Activity from Spitzer/IRS Spectra"
    • Find that AGN account for only 5% of the total IR luminosity produced by local LIRGs.
  33. Magdis, G. E. etal. 2011, "GOODS-Herschel~: Gas-to-Dust Mass Ratios and CO-to-H_2 Conversion Factors in Normal and Starbursting Galaxies at High-z"
  34. Ferkinhoff, C. etal. 2011, [[]["First Detections of the [NII] 122 micron Line at High Redshift: Demonstrating the Utility of the Line for Studying Galaxies in the Early Universe"]]
  35. Bureau, M. etal. 2011, "Molecular Gas and Star Formation in Local Early-Type Galaxies", to appear in Proceedings of the IAU Symposium 277 "Tracing the Ancestry of Galaxies"
  36. Hanish, D. J. etal. 2010, ApJ, 725, 2029, "A Multiwavelength Study on the Fate of Ionizing Radiation in Local Starbursts"
    • Find that galaxy-to-galaxy variations in the SEDs is much larger than any systematic differences between starbursts and non-starbursts. For example, find no significant differences in the total absorption of ionizing radiation by dust, although the dust in starburst galaxies appears to be hotter than that of non-starburst galaxies.
  37. Lindberg, J. E. etal. 2011, A&A, 527, A150, "A Survey of HC3N in Extragalactic Sources. Is HC3N a Tracer of Activity in ULIRGs?"
    • Note that a majority (~60% or more) of the HC3N-luminous galaxies in the sample present OH mega- or strong kilomaser activity. A possible explanation is that both HC3N and OH megamasers need warm dust for their excitation. Alternatively, the dust that excites the OH megamaser offers protection against UV destruction of HC3N. A high silicate absorption strength is also found in several of the HC3N-luminous objects, which may help the HC3N to survive.
    • Also find that a high HC3N/HCN ratio is related to a high dust temperature and a low CII flux.
  38. Hopkins, P. F. 2011, MNRAS, submitted, "Dynamical Delays Between Starburst and AGN Activity in Galaxy Nuclei"
    • Find that strong AGN are not present until the stellar populations in the central <~10 − 100 pc are of order a few Myr old.
    • (Explanation between the observed delay between SFR and BHAR): There is a clear delay which is larger when the SFR is measured at larger radii; this arises for two reasons. First, angular momentum loss in gas from gravitational instabilities occurs via transfer to the stellar material, when the magnitude of a symmetries in the potential is sufficient to induce shocks and dissipation in the gas. In the limit of a pure gas system, there is no collisionless component to absorb the angular momentum, and so the leading-order angular momentum loss is reduced to second-order resonance effects (Kalnajs1971) or an effective (turbulent) viscosity (Gammie2001). To leading order, the efficiency of angular momentum exchange in some annulus scales as propto (1−fgas), where fgas = Mgas/(Mgas+M∗) is the local gas fraction in the disk (Hopkins & Quataert 2010a). In flows that "pile up” high fgas in ∼tdyn in simulations therefore tend to stall until fgas can be lowered (the longer gas exhaustion timescale).
  39. Imanishi, M. etal. 2011, AJ, 141, 156, "Subaru and Gemini High Spatial Resolution Infrared 18 μm Imaging Observations of Nearby Luminous Infrared Galaxies"
  40. Meijerink, R., Spaans, M., Loenen, A. F., and van der Werf, P. P. 2011, A&A, 525, A119, "Star Formation in Extreme Environments: The Effects of Cosmic Rays and Mechanical Heating"
    • Excellent model showing importance of mechanical heating.
    • Would have been nice to know how H2CO abundance behaves in these models (not included in their analysis).
  41. Costagliola, F. etal. 2011, A&A, 528, A30, "Molecules as Tracers of Galaxy Evolution: An EMIR Survey. I. Presentation of the Data and First Results"
    • Notable are the measurements of HCN and HNC in quite a few starbursts, including NGC660. Can use this ratio to characterize effects of mechanical heating on starburst.
  42. Meier, D. S., Turner, J. L., and Schinnerer, E. 2011, AJ, 142, A32, "Cyanoacetylene in IC 342: An Evolving Dense Gas Component with Starburst Age"
    • Note that they also measured H2CO 2(02)-1(01) (in their PdBI band).
  43. Hou, L. G., Han, J. L., Kong, M. Z., and Wu, X.-B. 2011, ApJ, 732, A72, "Stellar Populations of Ultraluminous Infrared Galaxies"
  44. Cracia-Carpio, J. etal. 2011, ApJ, 728, L7, "Far-infrared Line Deficits in Galaxies with Extreme L_{FIR}/M_{H_{2}} Ratios"
    • Find that galaxies with LFIR/MH2 greater than 80 Lsun/Msun tend to have lower line to FIR continuum ratios than galaxies with lower LFIR/MH2 values. These line deficits affect all the observed lines, independent of their origin in the ionized or neutral phase of the interstellar medium.
    • The average [Cii]/FIR ratio is approximately constant in galaxies with low infrared luminosities, but starts to decrease at LFIR
∼10^(11) Lsun. At the same time, the scatter in the ratio increases by almost a factor of two: some high-redshift galaxies do not show a [Cii] deficit, even if their far-infrared luminosities are higher than10^(12) Lsun, and the source with the lowest [Cii]/FIR ratio is NGC4418, a galaxy with LFIR ≃10^(11) Lsun.
    • In summary, their observations show that the line to FIR continuum ratio drops by a factor of 3 to10 above LFIR/MH2 ∼ 80 Lsun/Msun in all the far-infrared fine structure lines we have observed. This drop seems to be a universal feature of galaxies at different redshifts and with different optical activity classifications.
    • Assumed that Lfir is mostly due to star formation.
    • As U increases, the HII region is extended to higher Av into the cloud. As a result, a larger fraction of the UV photons are absorbed by the dust in the ionized region and reemitted in the form of infrared emission. The net effect is that the fraction of UV photons available to ionize and excite the gas is reduced at high U, decreasing the relative intensity of the fine structure lines compared to the FIR continuum (see also Voit 1992).
    • Their detection of a universal drop of the line to continuum ratio at about the same LFIR/MH2 value where Genzel etal. (2010) and Daddi etal. (2010) claim a transition to a more efficient star formation mode gives in turn credence to this interpretation.
  1. Magdis, G. E., Elbaz, D., Hwang, H. S., etal. 2011, "Towards a Complete Census of High-z ULIRGs with Herschel". To appear in proceedings of the conference "Galaxy Evolution: Infrared to Millimeter Wavelength Perspective" (Guilin, China, 2010)
    • Derive higher Td than that using submm dust.
    • Submillimeter appears to be biased toward cold dust.
    • This explains the Td ~ 30-40 K measured toward many starbursts using submillimeter and FIR dust?
  2. Riechers, D. A., etal. 2011, ApJ, 726, A50, "Dense Molecular Gas Excitation at High Redshift: Detection of HCO+ (J = 4 → 3) Emission in the Cloverleaf Quasar"
  3. Sturm, E. etal. 2011, ApJL, 733, L16, "Massive Molecular Outflows and Negative Feedback in ULIRGs Observed by Herschel-PACS"
    • Report detection of massive molecular outflows, traced by OH, in FIR spectra of ULIRGs obtained with Herschel-PACS as part of the SHINING key project.
    • The high OH outflow velocities may be the long-sought conclusive evidence of powerful mechanical feedback from vigorous star formation and/or accreting central BHs.
    • OH outflow velocity could be a very promising tool to distinguish AGN-driven outflows from starburst-driven outflows, with AGN-dominated outflows reaching much higher velocities.
    • Radio jets could in principal be driving the outflows they see. However, nearly all of the objects presented are radio quiet, so this energy source can safely be assumed to be negligible. Only in Mrk231 does a radio jet contribute to the NaI D outflow.
    • No spatial information from these measurements.
    • Should use EVLA to image these galaxies.
  4. Bayet, E., Williams, D. A., Hartquist, T. W., and Viti, S. 2011, MNRAS, 414, 1583, "Chemistry in Cosmic Ray Dominated Regions"
    • Model chemistry in extremely high CR energy density (up to 10,000 times larger than that in the MW) regions (like in starbursts and mergers).
    • Model does not include freeze-out of species on to grain mantles.
    • All calculations made for an assumed n(H2) = 10^4 cm^(-3).
    • Model calculations done for a range from CR ionization rates (zeta) from MW (2x10^(-17) sec^(-1)) to those suggested to be appropriate to compact starburst regions (Papadopoulos 2010; 10^(-12) sec^(-1)).
    • At the highest CR ionization rate, almost all of the chemistry is effectively suppressed.
    • NH3 has a large fractional abundance for lower ionization rates, but its abundance declines rapidly as the ionization rate increases.
    • HCO+ is essentially useless for CR ionization rates larger than 10^(-13) sec^(-1), as its is completely destroyed.
    • The results for the Av = 8 mag case are closely similar to those for Av = 20 mag.
    • Authors note at end a similar paper by Meijerink etal. (2011) which leads to largely similar results. These authors used a PDR model to explore the effect of extremely high CR ionization rates and mechanical heating on the chemistry of low and high density molecular clouds.
  5. Hsieh, P.-Y. etal. 2011, ApJ, 736, 129, "Physical Properties of the Circumnuclear Starburst Ring in the Barred Galaxy NGC 1097"
    • No real proof of claimed distinction between inner and outer cloud properties.
    • Note that this galaxy seems to have very high temperature (Tk ~ 100 K).
  6. Elbaz, D. etal. 2011, A&A, submitted, "GOODS-Herschel: An Infrared Main Sequence for Star-Forming Galaxies"
    • Present "IR8 measurement", which is the ratio of the total IR luminosity to rest-frame 8 micron luminosity, is a very accurate measure of the star formation in galaxies.
    • Find that, locally, galaxies with high total LIR are systematically in the starburst mode, while this is not the case in the distant universe where most (U)LIRGs form stars in the "normal" main sequence mode. This confusion between two modes of star formation is the cause of the so-called "mid-IR excess problem" found in galaxies at z > 1.5 by previous studies.
    • Related Papers:
      1. Sargsyan, L. etal. 2011, ApJ, 730, 19, "Infrared Spectra and Spectral Energy Distributions for Dusty Starbursts and Active Galactic Nuclei"
        • This method should be compared to IR8
      2. Petric, A. O. etal. 2011, ApJ, 730, 28, "Mid-Infrared Spectral Diagnostics of Luminous Infrared Galaxies"
        • This method should be compared to IR8
  7. Riechers, D. A. etal, 2011, ApJ, 730, A108, "Molecular Gas in Lensed z >2 Quasar Host Galaxies and the Star Formation Law for Galaxies with Luminous Active Galactic Nuclei"
  8. Riechers, D. A. etal, 2011, ApJ, 733, L11, " Imaging the Molecular Gas Properties of a Major Merger Driving the Evolution of a z = 2.5 Submillimeter Galaxy"
    • The morphology is consistent with that of an early-stage merger.
  9. Riechers, D. A., etal. 2011, ApJ, 733, L12, "Dynamical Structure of the Molecular Interstellar Medium in an Extremely Bright, Multiply Lensed z ~= 3 Submillimeter Galaxy Discovered with Herschel"
  10. Scott, K. S., etal, 2011, ApJ, 722, A29, "Redshift Determination and CO Line Excitation Modeling for the Multiply Lensed Galaxy HLSW-01"
  11. Oyabu, S. etal, 2011, A&A, 529, A122, "AKARI Detections of Hot Dust in Luminous Infrared Galaxies: Search for Dusty Active Galactic Nuclei"
    • Cannot distinguish AGN from multiple dusty star clusters with massive stars as cause of hot dust emission.
  12. Hou, L. G., Han, J. L., Kong, M. Z., and Wu, Xue-Bing 2011, ApJ, 732, A72, " Stellar Populations of Ultraluminous Infrared Galaxies"
  13. Krumholz, M., Leroy, A. K., McKee, C. F. 2011, ApJ, 731, A25, "Which Phase of the Interstellar Medium Correlates with the Star Formation Rate?"
  14. Willett, K. W., etal. 2011, ApJ, 730, A56, "Mid-Infrared Properties of OH Megamaser Host Galaxies. I. Spitzer IRS Low- and High-Resolution Spectroscopy"
  15. Willett, K. W., etal. 2011, ApJ, 730, A56, "Mid-Infrared Properties of OH Megamaser Host Galaxies. II. Analysis and Modeling of the Maser Environment"
    • Find that 10%-25% of the OHMs show evidence for the presence of an AGN, significantly lower than the estimated AGN fraction from previous optical and radio studies.
    • But what distinguishes an OHM galaxy from a garden-variety LIRG?
  16. Geach, J. E., etal. 2011, ApJ, 730, L19, "On the Evolution of the Molecular Gas Fraction of Star-Forming Galaxies"
    • Find evidence that the average molecular gas fraction has undergone strong evolution since z ~ 2, with fgas proportional to (1+z)^(~2+-0.5)
  17. Shi, Y., etal. 2011, ApJ, 733, A87, "Extended Schmidt Law: Role of Existing Stars in Current Star Formation"
  18. Wu, Y., etal. 2011, ApJ, 734, A40, "The Mid-infrared Luminosity Function at z < 0.3 from 5MUSES: Understanding the Star Formation/Active Galactic Nucleus Balance from a Spectroscopic View"
    • Confirm that AGN play more important roles energetically at high luminosities.
  19. Andrews, B. H. and Thompson, T. A. 2011, ApJ, 727, 97, "Assessing Radiation Pressure as a Feedback Mechanism in Star-forming Galaxies"
    • The linear L IR-L'HCN correlation is a natural prediction of radiation pressure regulated star formation.
    • Recent observations indicate that the most luminous GMCs in the Milky Way are disrupted by radiation pressure.
  20. Bouwens, R. J. etal. 2011, Nature, 469, 504, "A candidate redshift z~10 galaxy and rapid changes in that population at an age of 500Myr"
    • The detection of galaxies at very high redshift from deep imaging data depends on the absorption (by intervening neutral hydrogen) of much of the flux in the spectrum at wavelengths below the wavelength of Lyman α (121.6 nm).
    • In addition, our z ≈ 10 candidate is not detected in the IRAC data, as expected given the IRAC flux limits.
    • Thus our results reaffirm that the significant evolution seen in galaxies at lower redshift continues to z ≈ 10 (in contrast with other studies).
    • It is of great interest to estimate the ultraviolet luminosity density at z ≈ 7–10 where reionization most probably occurred, given its apparent completion at z ≈ 6 (ref. 23) and its onset at z ≈ 11 as deduced from Wilkinson Microwave Anisotropy Probe (WMAP) observations.
    • We find that the ultraviolet flux that is available from galaxies at z ≈ 10 is only ~ of what is needed for galaxies to be the reionizing source. Where are most of the ultraviolet photons coming from?
    • This is clearly an era when galaxies were evolving very rapidly. The star formation rate density increased by a factor of ~10 in less than 200 Myr, from z ≈ 10 to z ≈ 8.
  21. Kovacs, A. et al. 2010, ApJ, 717, 29, "Far-infrared Properties of Spitzer-selected Luminous Starbursts"
    • Nice dust model analysis. See specifically section 4.1 (Single-Temperature Dust Models).
    • Measure dust heated by SF, hence see extended sizes.
    • Our models provide an excellent fit to the 6 μm-2 mm measurements of local starbursts. We find characteristic single-component temperatures T1 sime 35.5 ± 2.2 K and integrated infrared (IR) luminosities around 1012.9 ± 0.1 Lsun for the SWIRE-selected sources. Molecular gas masses are estimated at sime4 × 1010 Msun, assuming κ850 μm = 0.15 m2 kg–1 and a submillimeter-selected galaxy (SMG)-like gas-to-dust mass ratio. The best-fit models imply gsim2 kpc emission scales.
    • Based on these galaxies we find that a power-law distribution of temperature components (dMd/dT vprop T–γ), with a low-temperature cutoff at Tc, are in excellent agreement with measurements (Figure 2)
    • Therefore, we expect γ ≈ 6.5-7.5 for sources embedded in a diffuse medium (e.g., star formation), and γ ≈ 4-5 if absorption happens inside a dense medium at a well-defined distance from the source (e.g., for a molecular ring surrounding an AGN).
    • Thus, we find that β = 1.53 ± 0.04 and γ = 7.22 ± 0.09 describe the local starburst best, producing close to the expected level of residual scatter based on the measurement and calibration uncertainties.
    • For the size of the emitting region (i.e., for setting dΩAD2A), we assume an average diameter of 3 kpc in our single-temperature fits. Such an extended starburst is unprecedented in the local universe, where the luminosities tend to originate from smaller kpc-scale molecular rings.
    • The FIR properties derived from the single-T fits are based on the MAMBO 1.2 mm measurement and our SHARC-2 350 μm data only. Shorter wavelength data (especially MIPS 24 μm) were not included in these fits because these trace higher-temperature components and aromatic features.
    • The implied scales, spanning kiloparsecs across, are in line with Farrah et al. (2008) and are a strong indication that dust heating is distributed, which in turn supports star formation as the primary power source.
    • The implied radiation-field distribution indices α gsim 2.0-2.35 further support star formation as the primary heating source behind the extreme luminosities.
    • We demonstrated that such models describe local starbursts extremely well, under a tightly constrained dust emissivity index β sime 1.5 and mass-temperature index γ sime 7.2. The γ values are consistent with what we expect for heating dominated by star formation.
    • We place the typical diameter of starburst activity in these SMGs above 1.2 kpc (with 95% confidence), and find a most likely value of 2 kpc.
  22. Carilli, C. L. et al. 2010, ApJ, 714, 1407, "Imaging the Molecular Gas in a Submillimeter Galaxy at z = 4.05: Cold Mode Accretion or a Major Merger?"
    • Note large spatial extent and ordered rotation in this object, suggesting that this is not a major merger, but rather a clumpy disk accreting gas rapidly in minor mergers or smoothly from the proto-intracluster medium. Suggests cold accretion feeding.
    • Note, though, that ordered motion does not necessary exclude merger as ordered rotation can be re-established quickly following a merger.
    • Notes past trend noted where increasing mass implies earlier and quicker star formation.
    • SMGs may be the starburst progenitors of massive early type galaxies.
    • The emerging scenario is that SMGs may be the starburst progenitors of massive early type galaxies.
    • A key question for the SMGs is: what drives the prolific star formation? Tacconi et al. (2006, 2008) argue, based on CO imaging of a sample of z ~ 2 SMGs, that SMGs are predominantly nuclear starbursts, with median sizes <0farcs5 (<4 kpc), "representing extreme, short-lived, maximum star-forming events in highly dissipative mergers of gas-rich galaxies." This conclusion is supported by VLBI imaging of the star-forming regions in two SMGs (Momjian et al. 2005, 2010). We return to this question below.
    • There are likely enough SMGs at z>3.5 to account for the known populations of old massive galaxies at z ~ 2 to 3.
    • Measurements imply a hyper-luminous infrared galaxy with a total IR luminosity (8-1000 μm) of LIR = 2.9 × 1013Lsun, and a dust temperature ~57 K (Daddi et al. 2009a).
    • Therefore, it appears that the GN20 volume has a very significant overdensity, indicating a proto-cluster environment at z ~ 4.05.
    • Note that they did not measure the entire line with their VLA observations.
    • The total velocity range covered is 670 km s–1, and the implied velocity-integrated line intensity is 0.22 ± 0.04 Jy km s–1, after correcting for the 25% of the line that falls outside the band.
    • No continuum emission is seen from GN20 in the off-line 23 GHz image to a 1σ limit of 30 μJy.
    • Imaging of the molecular gas, radio continuum, and rest-frame thermal dust continuum emission in GN20 are all consistent with the gas and star formation being distributed over a disk between 2.5 kpc and 4.5 kpc in radius.
    • For the lower excitation component, we constrain the source radius to be 4.5 kpc, based on the CO 2-1 imaging (Section 4.3). For this component, we derive a filling factor of 0.5, an H2 density of 300 cm–3, and a kinetic temperature of 30 K.
    • For the higher excitation component, we fix the source radius to be 2.5 kpc, based on the CO 6-5 observations (Section 4.3). We then derive a density of 6300 cm–3, a kinetic temperature of 45 K, and a filling factor of 0.13.
    • For example, Tacconi et al. (2006) find typical densities in SMGs at z ~ 2 to be >1000 cm–3. However, they base this conclusion on LVG fits to CO 3-2 and higher-order transitions. The diffuse component in GN20 only becomes dominant in the 2-1 and 1-0 transitions, i.e., the Tacconi et al. study is relevant to the compact component for the CO, but can say little about the full molecular gas reservoirs.
    • Using the gas mass and SFR, the gas consumption timescale (≡ gas mass/SFR) for GN20 is ~5 × 107 × (α/0.8) yr. The rotational time for the disk is also ~5 × 107 yr. Hence, the gas consumption timescale is comparable to the dynamical timescale in GN20. The z ~ 2 SMG sample of Tacconi et al. (2006) has comparable gas consumption timescales to GN20. This compares to the order-of-magnitude longer gas consumption timescales found for normal star-forming galaxies at z ~ 2 (Tacconi et al. 2010; Daddi et al. 2010a).
    • The entire ~10 kpc region of active star formation, as traced by the CO, FIR, and radio continuum, is completely obscured in the HSTI-band (rest-frame UV) image.
    • The following summarizes the physical conditions in GN20: The CO is lower excitation than seen in low-redshift nuclear starbursts and high-redshift quasar host galaxies, but it is higher than in nearby spiral galaxies and normal star-forming galaxies at z ~ 1.5. The CO emission from GN20 is consistent with a two-component model, consisting of a 4.5 kpc radius disk of lower density (300 cm–3), temperature (30 K), with a filling factor ~0.5, and a region of ~2.5 kpc radius with higher density (~6300 cm–3), higher temperature (45 K), and lower filling factor (~0.13). The mass is roughly equal in each component (assuming the same conversion factor). The gas depletion timescale is comparable to the rotational time of the galaxy ~5 × 107 × (α/0.8) yr. We note that Papadopoulos et al. (2010) have proposed that dust opacity in dense regions can also affect the observed line ratios for CO, when observing very high order transitions (e.g., CO 6-5). High-resolution imaging of the CO 6-5 is required to determine the spatial dependence of gas excitation in GN20.
    • Apparently GN20 is not the only "extended" SMG. In GN20, we see a more extended, lower excitation molecular gas distribution on a scale ~10 kpc, containing at least half the gas mass in the system. Interestingly, a number of other z ~ 2 SMGs have been observed in CO 1-0: the submillimeter-bright ERO J16450+4626 (Greve et al. 2003), SMM J13120+4242 (Hainline et al. 2006), and SMM J02399–0136 (Ivison et al. 2010). These galaxies show excess CO 1-0 emission relative to what is expected by extrapolating from higher-order transitions assuming constant brightness temperature, by factors of at least 2. Moreover, VLA imaging of J16450+4626 reveals extended CO 1-0 emission on a scale of ~10 kpc (Greve et al. 2003), while for J02399–0136 the CO 1-0 emission extends over 25 kpc (Ivison et al. 2010).
    • The following is a very nice summary of Cold Mode Accretion (CMA): An alternative model, known as CMA, or stream fed galaxy formation, has recently been proposed to explain secular star formation (i.e., on timescales >108 yr) in more populous, normal star-forming galaxies at z ~ 2 (Dekel et al. 2009; Keres et al. 2009). In the CMA model, gas flows into galaxies from the intergalactic medium (IGM) along cool, dense filaments. The flow never shock-heats due to the rapid cooling time, but continuously streams onto the galaxy at close to the free-fall time. This gas forms a thick, turbulent, rotating disk which efficiently forms stars across the disk, punctuated by giant clouds of enhanced star formation on scales ~ few kpc. These star-forming regions then migrate to the galaxy center via dynamical friction and viscosity, forming compact stellar bulges (Genzel et al. 2006; Genzel et al. 2008; Bournaud et al. 2008a, 2008b; Elmegreen et al. 2009). The CMA process can lead to relatively steady and active (~100 Msun yr–1) star formation in galaxies over timescales approaching 1 Gyr. The process slows down dramatically as gas supply decreases, and the halo mass increases, generating a virial shock in the accreting gas. Subsequent dry mergers at lower redshift then lead to continued total mass buildup, and morphological evolution, but little subsequent star formation (Hopkins et al. 2009; Naab et al. 2009). Observations of intermediate redshift (z ~ 2), normal star-forming galaxies support the CMA model (Genzel et al. 2006, 2008; Daddi et al. 2008, 2009b, 2010a; Tacconi et al. 2010).
    • The fact that the gas mass and the dynamical mass are comparable (within a factor 2 or so), argues against very strong lensing.
  23. Engel, H. et al. 2010, ApJ, 724, 233, "Most Submillimeter Galaxies are Major Mergers"
    • Point to Ivison etal (2002 and 2007) studies of the preponderance of radio doubles among SMGs. Likelihood that SMGs have companions within a few arcsec is significantly larger than would be expected by chance.
    • Two different theoretical approaches to reproduce the submillimeter galaxy population in simulations are currently being pursued. In semi-analytic models (e.g., Swinbank et al. 2008), the high submillimeter luminosities are achieved through bursts of star formation induced in gas-rich major mergers (although disk instabilities may also occur; Bower et al. 2006), whereas numerical simulations have also invoked “cold accretion flows.” uv In the latter, SMGs are assumed to be massive galaxies sitting at the centers of large potential wells, constantly forming stars at high rates sustained by smooth infall and accretion of gas-rich satellites (e.g., Dav ´
e et al. 2010).
    • Five of their systems consist of two spatially distinct galaxies, and the remaining seven have either disturbed morphologies typical of advanced, pre-coalescence mergers or are compact, dense galaxies which plausibly are late-stage, coalesced mergers.
    • All are major mergers (mass ratios of 1:3 or closer).
    • SMG size measurements (Gaussian FWHM) from radio and CO fluxes are both consistent with ~5 kpc diameters.
    • Several recent studies have found that star formation in SMGs is more extended than the kpc-scale central starburst found in local ULIRGs.
  1. Seymour etal. 2011, MNRAS (in press), "HerMES: SPIRE/Sub-millimetre Emission from Radio Selected AGN"
    • Note strong SF evolution with z.
    • Radio loud phase transient (short duty cycle).
  2. Aalto, S., Costagliola, F., van der Tak, F., and Meijerink, R. 2011, A&A, 527A, 69A, "H3O+ line emission from starbursts and AGNs"
    • High N(H3O+) suggests PDR and/or XDR, but does not quite reproduce high N observed.
    • Can also produce high N observed with high Tk and n(H2).
    • Since H3O+ formation requires H2O to exist in the gas phase, the H3O+ molecule acts as a natural filter to select hot (Tk > 100 K) molecular gas, and therefore traces more specific regions than molecules usually surveyed towards other galaxies.
  3. Casaola, V., Hunt, L. K., Combes, F., Garcia-Burillo, S., Boone, F., Eckart, A., Neri, R., and Schinnerer, E. 2010, A&A, 510, A52, "Molecular Gas in NUclei of GAlaxies (NUGA): XIII. The Interacting Seyfert 2/LINER Galaxy NGC5953"
    • CO imaging and HCN mapping of this late-merger galaxy.
  4. Martin, S., Martin-Pintado, J., Vitt, S. 2009, ApJ, 706, 1323, "Photodissociation Chemistry Footprints in the Starburst Galaxy NGC253"
  5. Juneau, S., Narayanan, D. T., Moustakas, J., Shirley, Y. L., Bussmann, R. S., Kennicutt Jr., R. C., and Vanden Bout, P. A. 2009, ApJ, 707, 1217, "Enhanced Dense Gas Fraction in Ultraluminous Infrared Galaxies"
    • Confirms Gao & Solomon relation between LIR and LHCN.
    • Results suggest that AGN reside in systems with higher dense gas fraction, and that chemistry or other effects associated with their hard radiation field (such as x-ray-driven chemical abundance effects) may not dominate (with NGC1068 being an exception).
    • Notes that Bussman etal, (2008) measured HCN 3-2 in the GS04 galaxy sample and found a SFR-HCN(3-2) index less than unity (0.72+-0.08).
    • Conclude that the GS04 results are valid and that HCN 1-0 is a good tracer of star formation in ULIRGs.
  6. Chung, A., Narayanan, G., Yun, M. S., Heyer, M., and Erickson, N. R. 2009, AJ, 138, 858, "The Redshift Search Receiver Observations of 12CO J=1-0 in 29 Ultraluminous Infrared Galaxies"
    • Extended sample of ULIRGs.
  7. Sargsyan, L. A. and Weedman, D. W. 2009, ApJ, 701, 1398, "Star Formation Rates for Starburst Galaxies from Ultraviolet, Infrared, and Radio Luminosities"
    • UV is a poor indicator of star formation in galaxies.
  8. Menendez-Delmestre, K., Blain, A. W., Smail, I., Alexander, D. M., Chapman, S. C., Armus, L., Frayer, D., Ivison, R. J., and Teplitz, H. 2009, ApJ, 699, 667, "Mid-Infrared Spectroscopy of Submillimeter Galaxies: Extended Star Formation in Massive High-redshift Galaxies"
    • Excellent introduction with very nice description of SMG evolutionary scenarios.
    • Find evidence for a more extended distribution of cool and warm dust in SMGs compared to the more compact emitting regions in local ULIRGs and starbursts. Together these results suggest that SMGs are not simple high-redshift analogs of nuclear starbursts or local ULIRGs, but instead they appear to have star formation which resembles that seen in less-extreme star-forming environments at z ~ 0 – suggesting their intense activity is distributed across a far larger region than the ~1 kpc nuclear bursts in local ULIRGs.
  9. Imanishi, M., Nakanishi, K., Tamura, Y., and Pen, C.-H. 2009, AJ, 137, 3581, "Nobeyama Millimeter Interferometric HCN(1-0) and HCO+(1-0) Observations of Further Luminous Infrared Galaxies"
    • Provide further support for the fact that the HCN(1-0)/HCO+(1-0) brightness temperature ratio can be used to observationally distinguish AGN-important and starburst-dominant galactic nuclei.
    • Note that lower-resolution HCN and HCO+ observations of LIRGs (i.e. Gao and Solomon) were done with relatively large beam sized (greater than 25 arcsec), so are not very sensitive to nuclear emission in these galaxies.
    • Also use IR spectral emission measurements to distinguish influence of AGN and starburst.
      • A normal starburst galaxy should always show strong PAH emission.
      • A pure AGN should always produce a PAH-free IR emission spectrum.
      • CO absorption features should show up in starburst-dominated LIRGs, but not AGN-dominated, since CO absorption is produced by stars older than 10^6 years, but not by AGN-heated hot dust emission.
  10. Devlin, M. J. etal. 2009, Nature, 458, 737, " Over half of the far-infrared background light comes from galaxies at z>=1.2"
    • Title says it all.
    • Used 250, 350, and 500 micron bolometer measurements of GOODS-South.
    • Dust spectrum analysis points to an extragalactic origin, since if there is no evolution in number density or luminosity in these source counts one expects them to behave like a Euclidean distribution with dN/dS proportional to S^(-2.5).
  11. Wilson, C. D. etal, 2009, ApJS, 178, 189, "Luminous Infrared Galaxies with the Submillimeter Array. I. Survey Overview and the Central Gas to Dust Ratio"
    • Excellent survey of nearby LIRGs.
    • Approximately 1 kpc spatial resolution in their sample, which include measurements of CO 3-2, CO 2-1, 13CO 2-1, and HCO+ 4-3.
    • Find HCN/HCO+ line ratio spatial variations in VV114 and Arp 299 which suggest that there are interesting physical and/or chemical variations in the gas properties in these early-stage mergers.
    • Find that 880 micron is more extended than CO 3-2, leading to a small fraction of 880 micron single dish flux recovered.
    • Find strong dependence of central gas-to-dust ratio on IR luminosity, but not on nuclear separation.
    • Find that the star formation rate, but not the star formation efficiency, increase with central gas surface density.
    • Survey includes:
      • IRAS 17208-0014
      • Mrk 231
      • Mrk 273
      • IRAS 10565+2448
      • UGC 5101
      • Arp 299
      • Arp 55
      • Arp 193
      • NGC 6240
      • VV114
      • NGC 5331
      • NGC 2623
      • NGC 5257/5258
      • NGC 1614
  12. Silverman, J. D. etal., 2009, ApJ, 695, 171, "The Environments of Active Galactic Nuclei within the zCOSMOS Density Field"
  13. Hainline, L. J. etal. 2009, ApJ, 699, 1610, "A Mid-Infrared Imaging Survey of Submillimeter-Selected Galaxies with the Spitzer Space Telescope"
  14. McQuinn, K. B. W. etal. 2009, ApJ, 695, 561, "The True Durations of Starbursts: Hubble Space Telescope Observations of Three Nearby Dwarf Starburst Galaxies"
  15. Lonsdale, C. J. etal. 2009, ApJ, 692, 422, "!MAMBO 1.2mm Observations of Luminous STarbursts at z ~ 2 in the Swire Fields"
  16. Rieke, G. H. etal. 2009, ApJ, 692, 556, "Determining Star Formation Rates for Infrared Galaxies"
  17. Reichard, T. A. etal. 2009, ApJ, 691, 1005, "The Lopsidedness of Present-Day Galaxies: Connections to the Formation of Stars, the Chemical Evolution of Galaxies, and the Growth of Black Holes"
  18. Lee, J. C. etal. 2009, ApJ, 692, 1305, "Dwarf Galaxy Starburst Statistics in the Local Volume"
  19. Haan, S. etal. 2009, ApJ, 692, 1623, "Dynamical Evolution of AGN Host Galaxies -- Gas In/Out Flow Rates in Seven NUGA Galaxies"
  20. Hernan-Caballero, A. etal. 2009, MNRAS, 395, 1695, "Mid-Infrared Spectroscopy of Infrared-Luminous Galaxies at z ~ 0.5-3"
  21. Tyler, K. D. etal. 2009, ApJ, 691, 1846, "Spitzer 70/160 micron Observations of High-Redshift ULIRGs and HyLIRGs in the Bootes Field"
  22. Gruppioni, C. etal. 2008, ApJ, 684, 136, "The Contribution of AGNs and Star-Forming Galaxies to the Mid-Infrared as Revealed by Their Spectral Energy Distributions"
  23. Di Matteo, P. etal. 2008, A&A, 492, 31, "On the Frequency, Intensity, and Duration of Starburst Episodes Triggered by Galaxy Interactions and Mergers"
  24. Martin, S., Martin-Pintado, J., and Mauersberger, R. 2009, ApJ, 694, 610 "HNCO Abundances in Galaxies: Tracing the Evolutionary State of Starbursts"
    • Measure HNCO/CS abundance ratios toward SBs which vary by nearly 2 orders-of-magnitude.
    • Variations in HNCO abundances suggestive of relationship to evolutionary stage of the SB, as it is:
      • Enhanced during the shock-dominated early phases of a SB galaxy and
      • Destroyed by strong UV fields during the later states of a SB.
  25. Veilleux, S. etal. 2009, ApJS, 182, 628, "Spitzer Quasar and ULIRG Evolution Study (QUEST). IV. Comparison of 1-Jy Ultraluminous Infrared Galaxies with Palomar-Green Quasars"
    • Main conclusions are:
      1. The average AGN contribution in ULIRGS is ~ 35% to 40%, in agreement with previous ISO studies.
      2. The largest AGN contributions are observed at the smallest nuclear separations and latest interaction classes.
      3. All ULIRGs in the sample fall into three distinct classes represented by the amount of extinction and the PAH EW.
      4. The scatter observed in various trends of AGN contribution, Eddington ratio, and dust obscuration with merger stage suggest that the standard evolution scenario from ULIRG to QSO requires revision.
  26. Iono, D. etal. 2009, ApJ, 695, 1537, "Luminous Infrared Galaxies with the Submillimeter Array. II. Comparing the CO 3-2 Sizes and Luminosities of Local and High-Redshift Luminous Infrared Galaxies"
    • Find that Lprime(CO3-2) is strongly correlated with LFIR with a slope of 0.93 over five orders of magnitude. This indicates that CO 3-2 is a very robust tracer of star formation.
    • The slope of the Lprime(CO3-2)/LFIR correlation is significantly steeper than the Lprime(CO1-0)/LFIR correlation (about 0.6) due to the fact that CO 1-0 has a much lower critical density. In other words, CO 3-2 does a better job of tracing high density (star forming) gas.
    • CO 3-2 source size measurements suggest that the brighter ULIRGs are systematically more compact than the less FIR bright LIRGs.
    • The CO 3-2 source sizes of the SMGs are on average an order of magnitude larger than the ULIRGs, and are comparable to the separation between the widely-separated LIRGs in the sample.
  27. Fernandes, R. C. etal. 2009, "The Starburst-AGN Disconnection", to appear in the proceedings of "The Starburst-AGN Connection" conference (2008)
    • Very nice analysis of LINER-type AGN which have traditionally not been included in studies of AGN properties.
    • Derived from the SDSS.
  28. Brand, K., Weedman, D. W., Desai, V., Le Floch, E., Armus, L., Dey, Arjun, Houch, J. R., Jannuzi, B. T., Smith, H. A., and Soifer, B. T. 2008, ApJ, 680, 119 "Spitzer Mid-Infrared Spectroscopy of Distant X-Ray Luminous Active Galactic Nuclei"
    • See PAH-dominated and PAH-free AGN in a sample of 16 optically-faint IR luminous galaxies.
    • Suggest that variance in PAH content indicative to dust content near AGN.
  29. Dasyra, K. M., Yan, L., Helou, G., Surace, J., Sajina, A., and Colbert, J. 2008, ApJ, 680, 232 "HST Nicmos Imaging of z ~ 2, 24 micron-Selected Ultraluminous Infrared Galaxies"
    • Sample includes ULIRGs with log(L) = 10-11 Lsun and a mean half-light radius equal to 2.66 kpc. This half-radius value is about half that of local ULIRGs (but surface brightness dimming might be the explanation for this difference).
    • 17 of the sample of 33 are involved in interactions.
    • Up to 1/5 of the sample could be minor mergers (mass fraction less than 3:1).
    • Only 2 of the sample galaxies are major mergers.
    • A non-neglegible fraction of the sources in their sample do not resemble local ULIRGs, which are produced by major mergers and form elliptical galaxies. However, it is unclear whether this result is characteristic of most z = 2 ULIRGs or whether it relates to their selection criteria.
    • Clear that several interaction types can be associated with a ULIRG at z = 2.
  30. Chapman, S. C., etal., 2008, ApJ, 689, 889 "Interferometric CO Observations of Submillimeter-Faint, Radio-Selected Starburst Galaxies at z ~ 2"
    • Characterization of Submillimeter-Faint Radio Galaxies (SFRGs).
    • Find that high-redshifted, dust-obscured galaxies, selected to be luminous in the radio but relatively faint at 850 micron, appear to represent a different population from the ultraluminous submillimeter-bright population. They may be star-forming galaxies with hotter dust temperatures, or they may have lower far-infrared luminosities and larger contributions from obscured active galactic nuclei (AGNs).
  31. Polletta, M. etal. 2008, A&A, in press "Obscured and Powerful AGN and Starburst Activities at z ~ 3.5"
    • Support radio feedback/star-formation-quenching aspect of AGN evolution.
  32. Weiss, A., Kovacs, A., Guesten, R., Menten, K. M., Schuller, F., Siringo, G., and Kreysa, E. 2008, A&A, 490, 77 "LABOCA Observations of Nearby Active Galaxies"
  33. Ao, Y., Weiss, A., Downes, D., Walter, F., Henkel, C., and Menten, K. M. 2008, A&A, in press, "The CO Line SED and Atomic Carbon in IRAS F10214+4724"
  34. Desai, V. etal. 2008, ApJ, 679, 1204 "Redshift Distribution of Extragalactic 24 micron Sources"
  35. Weedman, D. W. and Houck, J. R. 2008, ApJ, 686, 127 "The Most Luminous Starbursts in the Universe"
    • Table of 7.7 micron luminosities for starburst galaxies.
  36. Garcia-Burillo, S., Combes, F., Usero, A., and Gracia-Carpio, J. 2008, AHAR-2008 Conference "High-Resolution Molecular Line Observations of Active Galaxies"
    • Good review (though a bit biased toward author's own work).
  37. Sirocky, M. M., Levenson, N. A., Elitzur, H., Spoon, H. W. W., and Armus, L. 2008, ApJ, 678, 729 "Silicates in Ultraluminous Galaxies"
  38. Cao, Ch. Xia, X. Y., Wu, H., Mao, S., Hao, C. N., and Deng, Z. G. 2008, MNRAS, in press, "Mid-Infrared Spectroscopic Properties of Ultra-Luminous Infrared Quasars"
    • Correlate PAH EW with outflow velocity (as measured via H-beta blueshifted emission). Find that QSOs with higher outflow velocities have lower EWs, suggesting:
      • More energetic AGNs and central massive starbursts can drive faster outflows which then suppress or even quench star formation by heating-up or expelling the cold gas and dust in the QSO host, leading to a lower SFR, or
      • Higher velocity outflows are more efficient at ejecting dust cocoons of AGNs, leading to AGNs becoming the dominant source in comparison to starbursts.
    • IR QSOs are a distinct population from PG QSOs and ULIRGs.
    • Mid-IR properties of IR QSOs are intermediate between ULIRGs and optically-selected QSOs, possibly representing a transitional stage from ULIRG to QSO.
  39. Bastian, N. 2008, MNRAS, in press, "On the Star Formation Rate - Brightest Cluster Relation: Estimating the Peak SFR in Post-Merger Galaxies"
    • Show that trend between SFR and brightest cluster is due to the fact that brightest cluster is young (< 15 Myr), making brightest cluster a good indicator of SFR.
  40. Chapman, S. C., Neri, R., Bertoldi, F., Smail, I., Greve, T. R., Trethewey, D., Blain, A. W., Cox, P., Genzel, R., Ivison, R. J., Kovacs, A., Omont, A., and Swinbank, A. M. 2008, ApJ, in press, "Interferometric CO Observations of Submillimeter-Faint, Radio-Selected Starburst Galaxies at z ~ 2"
    • Study a "sample" of three radio-luminous but faint at 850 micron.
    • Suggest that these objects represent a separate population of either hot submillimeter galaxies or galaxies with large AGN influence.
    • Not at all convincing. Gas masses are only a factor of 4 low, which is well within the envelope of the CO luminosity to radio flux correlation defined by SMGs, ULIRGs, and other starburst galaxies.
  41. Bayet, E., Viti, S., Williams, D. A., and Rawlings, J. M. C. 2008, ApJ, 676, 978, "Molecular Tracers of High-Mass Star Formation in External Galaxies"
    • Use hot core models developed for Galactic hot cores to predict molecular abundances in external galaxies.
    • Find that H2CO is a good (linear) metallicity indicator.
  42. Higdon, J. L., Higdon, S. J. U., Willner, S. P., Brown, M. J. I., Stern, D., Le Floch, E., and Eisenhardt, P. 2008, ApJ, in press, "Radio and Infrared Selected Optically Invisible Sources in the Bootes NDWFS"
    • Compare optical and IR (Spitzer) properties of 16 optically-invisible MIPS 24 micron (OIMS) and 35 optically invisible radio (OIRS) sources.
    • Although OIMS, OIRS, and SMGs appear to be distinct populations, they appear to possess similar properties (at least as evidenced by their IR, optical, and radio emission.
  43. Satyapal, S., Vega, D., Dudik, R. P., Abel, N. P., and Heckman, T. 2008, ApJ, submitted, "Spitzer Uncovers Active Galactic Nuclei Missed by Optical Surveys in 7 Late-Type Galaxies"
    • Use evidence of measurable NeV (14 and/or 24 micron) emission as evidence for low-luminosity and/or embedded AGN.
    • Comparing to AGN models, find that when the fraction of the total luminosity due to the AGN is low, optical diagnostics are insensitive to the presence of the AGN. In this regime of parameter space, the mid-infrared diagnostics offer a powerful tool for uncovering AGN missed by optical spectroscopy.
  44. Boker, T., Falcon-Barroso, J., Schinnerer, E., Knapen, J. H., and Ryder, S. 2008, AJ, 135, 479, "A SINFONI View of Galaxy Centers: Morphology and Kinematics of Five Nuclear Star-Formation Rings"
    • Comparison of NIR spectral data cubes toward ring galaxies.
    • Compare intensities of Br-gamma and HeI lines, along with optical obscuration locations from optical images, to study star formation evolution along rings ("popcorn" versus "pearls-on-a-string" models). Find that 3 of the 5 galaxies studied have pearls-on-a-string morphology, while information from remaining 2 are incomplete but not inconsistent with either model.
  45. Narayanan, D., Cox, T. J., Shirley, Y., Dave, R., Hernquist, L., and Walker, C. K. 2008, ApJ, submitted, "Molecular Star Formation Rate Indicators in Galaxies"
    • Good overview of existing physics behind measured SFR-Lmol correlations.
    • Explain difference between SFR-Lmol correlation from low and high critical density transitions:
      • Lines with low critical densities (e.g. CO 1-0) are typically thermalized and trace the gas density faithfully. In these cases the SFR will be related to the line luminosity with an index similar to the Schmidt law index.
      • Lines with critical densities greater than the mean density of most of the emitting clouds (e.g. CO 3-2 and HCN 1-0) will exhibit significant emission driven by subthermally excited gas which owes its excitation to line trapping. The contribution to the total line luminosity from subthermally excited gas along the line of sight causes the line luminosity to increase with mean gas density superlinearly. Consequently, the SFR-Lmol index is less than the Schmidt law index.
  46. The Pierre Auger Collaboration, Science, 2007, 318, 938, "Correlation of the Highest-Energy Cosmic Rays with Nearby Extragalactic Objects"
    • Very interesting analysis of CRs with E > 10^(20) eV. Find that the sources of these "EeV" CRs are correlated with the positions of AGN.
    • Note that online version of article has high-resolution figures.
  47. Narayanan, D, etal. 2007, ApJ, submitted, "The Role of Galactic Winds on Molecular Gas Emission From Galaxy Mergers"
    • Models influence of outflows from SB and AGN on (U)LIRG evolution.
    • Uses Monte Carlo model to do radiative transfer.
    • SB and AGN feedback winds dominate.
    • Model CO morphology.
    • AGN-driven outflows are typically longer-lived than SB-driven outflows. This is due to the more efficient feedback of the AGN-driven winds.
  48. Brand, K. etal. 2007, ApJ, 673, 119, "Spitzer Mid-Infrared Spectroscopy of 70um-Selected Distant Luminous Infrared Galaxies"
    • An attempt to characterize (U)LIRGs by their MIR spectra.
    • Separates sources into PAH-dominated (SB-dominated) and Si-absorption-dominated (AGN-dominated) objects.
    • Conclude with the rather weak statement that Si-absorbed sources a deeply-embedded AGN, but that they cannot rule-out the possiblity that they are powered by deeply-embedded starbursts. This is basically the caution raised by Vega etal (2007) in their SED analysis.
  49. Vega, O., Clemens, M. S., Bressan, A., Granato, G. L., Silva, L., and Panuzzo, P. 2008, A&A, 484, 631, "Modeling the Spectral Energy Distribution of ULIRGs II: The Energetic Environment and the Dense Interstellar Medium"
    • Models of the radio through NIR SEDs of 30 (U)LIRGs.
    • Assesses possible contribution of the warm AGN component to the total SED or ULIRGs.
    • In all but one galaxy (IRAS 08572+3915) the starburst dominates the bolometric luminosity (infrared) emission from the sample galaxies, with a fractional contribution that is always larger than 80%.
    • About half of the galaxies are well-fit with a SB-only component.
    • In the MIR domain the emission is dominated by molecular cloud emission, but in (U)LIRGs this spectral region might be significantly affected by the presence of an AGN.
    • In characterizing the AGN versus SB contribution to the SEDs, they find that:
      • 15/30 objects can be fit with an almost pure SB because the total contribution to the AGN is < 1%, which is less than the accuracy of the model in all bands.
      • 10/30 require an AGN contribution to fit the spectra.
      • 5/30 require only a minimal AGN contribution.
      • 9/30 require an AGN contribution larger than 10%, and in most cases it is lower than 20%.
      • Only one galaxy (IRAS 08572+3915) appears to require a dominant AGN contribution (> 50%).
    • Neither MIR slope nor the PAH equivalent widths or relative fluxes provide a good estimate of the AGN contribution.
    • PAH equivalent widths and MIR spectral slopes overestimate the AGN fraction.
    • Two of the galaxies show variability at radio frequencies (UGC8058 and UGC8696). This variability may be an indication that the AGN actually powers sporadic emission which dominates at radio wavelengths.
    • There is evidence that the star formation in objects with an AGN decreases more rapidly than in pure starbursts. This could be caused by AGN feedback, either positively as a sudden enhancement of the SFR, or negatively by a more rapid decrease of the SFE.
    • Derive a relation between the IR luminosity and molecular gas mass with the same slope as that derived by G&S (2004) from observations of HCN emission.
    • Derive a constant of conversion between HCN luminosity and dense gas mass a factor of 2 smaller than G&S. Notable outliers from this correlation are those few objects with an energetically important AGN. After correcting their IR luminosity for the AGN contribution, they also fall on the LIR-to-Mdense correlation.
    • SFE decreases by about an order-of-magnitude as the SB evolves from its early phase to the more advanced phases.
  50. Clemens, M. S., Vega, O., Bressan, A., Granato, G. L., Silva, L., and Panuzzo, P. 2007, A&A, in press, "Modeling the Spectral Energy Distribution of ULIRGs I: The Radio Spectra"
    • Analysis of the 1.4 to 22.5 GHz spectral index version FIR emission.
    • Flattening observed at high and low frequencies. Also observe steepening at high frequencies. Explanations are:
      • Low frequencies: Free-free absorption.
      • High frequencies: Free-free emission.
      • Relativistic electron population "aging" can produce a steepening of the spectral slope at high frequencies.
    • Lack of correlation between the 1.4-8.4 GHz spectral index and q(8.4) (ration between FIR and 8.4 GHz radio flux) is evidence that source compactness plays an important role in defining the slope of the low frequency spectrum.
    • Most compact ULIRGs appear to be the warmest.
    • Source models are explored in paper II.
  51. Davies, R. I., Mueller Sanchez, F., Genzel, R., Tacconi, L. J., Hicks, E. K. S., Friedrich, S., and Sternberg, A. 2007, ApJ, 671, 1388, "A Close Look at Star Formation Around Active Galactic Nuclei"
    • Very nice model of the star formation near AGN.
    • NIR AO spectroscopy of 9 Seyfert galaxies.
    • Fit model (STARS) to stellar mass and light measurements.
    • Find that:
      • There is little or no ongoing star formation in sample objects. Coupled with the relatively young ages (10-300 Myr) this implies that star formation episodes are short-lived (< 10 Myr).
      • Disk galaxy scale heights are derived to be 5-20 pc.
      • Model results are similar to ULIRG models (Thompson), main difference being that starbursts occur near the AGN while ULIRG starbursts are more extended.
      • Starburst scenario:
        • High gas density leads to a high star formation rate, which produces a starburst that reaches the Eddington limit for a short time.
        • Because the efficiency is high, the starburst can only be active for a short time before fading.
        • The starburst is then dormant until the gas supply is replenished by inflow
      • Efficient fueling of a black hole is associated with a starburst that is at least 50-100 Myr old. This would explain why recent star formation is hard to detect close to AGN; the starburst has passed it most active and luminous phase and is in decline, while the AGN is in its most active phase (see their Figure 6).
      • The bright nuclear component has a half-width at half-maximum less than 50 pc (from stellar light spectral line profiles).
      • There is lots of evidence for a starburst in the last 10-300 Myr, but no indication of current starburst activity, implying a short timescale for the starburst (of order 10 Myr).
      • There appears to be a delay of at least 50-100 Myr between the onset of star formation and the onset of AGN activity. This seems to indicate that the starburst has a significant impact on the fueling of the central black hole. Winds from AGB stars ultimately dominate the total mass ejected by the starburst, which feeds the black hole and fuels the AGN.
  52. Yang, M., Greve, T. R., Dowell, C. D., and Borys, C. 2007, ApJ, 660, 1198, "350 Micron Observations of Ultraluminous Infrared Galaxies at Intermediate Redshifts"
    • 350 micron observations of 36 ultraluminous infrared galaxies (ULIRGs) at intermediate (0.089 <= z <= 0.926) using SHARCII.
    • Derive dust temperatures from grey body fits: Td = 42.8+-7.1 K, LFIR = 10^(12.2+-0.5) Lsolar, and Mdust = 10^(8.3+-0.3) Msolar.
    • Derive SFR = 10^(2.5+-0.5) Lsolar/yr, which is a factor of ~10^(3-4) larger than what is typically observed in normal quiescent galaxies, but comparable to the local ULIRG Arp220 (SFR ~= 320 Msolar/yr).
    • Argue that the somewhat higher Td's measured in this "local" sample, when compared to high-z SMGs, are possibly tied to the more compact spatial scales of the ongoing star formation in the local sample.
  53. Gracia-Carpio, J., Garcia-Burillo, S., Planesas, P., Fuente, A., and Usero, A. 2007, A&A, 479, 703, "Evidence on Enhanced Star Formation Efficiency in Luminous and Ultraluminous Infrared Galaxies"
    • Observational evidence that the LFIR/LHCN(1-0) ratio, taken as a proxy for the star formation efficiency in LIRGs and ULIRGs, is a factor of 2-3 higher in galaxies categorized as IR luminous (LFIR > 10^(11) Lsolar) compared to normal galaxies.
    • Observe change in LFIR-to-LHCN(1-0) correlation at LFIR ~= 10^(11) Lsolar. Using Schmidt-Kennicut law formalism (Sigma(SFR) propto Sigma(dense)^N) this change becomes a change to the power law from N ~ 0.80-0.95 for LFIR < 10^(11) Lsolar to N ~ 1.1-1.2 for LFIR > 10^(11) Lsolar.
    • Multi-line analysis further suggests that star formation efficiency of dense gas (SFE(dense)) may be up to an order of magnitude larger in extreme IR luminous galaxies than in normal galaxies.
    • Higher star formation efficiency might just be a reflection of higher average gas density in extreme IR luminous galaxies.
    • Results might also just be showing chemical affects (increasing HCN/HCO+) due to larger contribution due to AGN for extreme IR luminous galaxies.
    • Authors used an interesting way to correct LIR for AGN contribution using LFIR.
  54. Yamada, M., Wada, K., and Tomisaka, K. 2007, ApJ, 671, 73, "HCN to HCO+ Millimeter Line Diagnostics of AGN Molecular Tori: I. Radiative Transfer Modeling"
    • Hydrodynamic model simulation of HCN and HCO+ radiative transfer in AGN tori.
    • Find that high (>1) HCN-to-HCO+ J=1-0 line intensity ratios imply high HCN abundance (X(HCN) > 10*X(HCO+)).
    • Also note that PDR-dominated AGN naturally lead to HCN/HCO+ > 1, while XDR-dominated AGN natuarally lead to HCN/HCO+ < 1.
  55. Perez-Beaupuits, J. P., Aalto, S., and Gerebro, H. 2007, A&A, in press, "HNC, HCN, and CN in Seyfert Galaxies"
    • Present observations of NGC1068, NGC3079, NGC1365, NGC2623, and NGC7469.
    • Many of the galaxies show HCN/HNC line ratios with suggest low density emission sources (n <~ 10^5 cm^(-3)).
    • HCN/HNC ratios imply PDR chemistry domination, as opposed to XDR.
  56. Bouche, N. etal. 2007, ApJ, 671, 303, "Dynamical Properties of z~2 Star-Forming Galaxies and a Universal Star Formation Relation"
    • Reaffirms Schmidt-Kennicutt law relating gas surface density and star formation rate.
  57. Shirley, Y. L., Wu, J., Bussmann, R. S., and Wootten, A. 2007, to appear in the ASP Conference Series volume "Massive Star Formation: Observations Confront Theory", titled "The Properties of Dense Molecular Gas in the Milky Way and Galaxies"
    • Nice overview of the observational and theoretical state of the comparison between Lprime and M (i.e. measures of the star formation rate) in molecular cloud and galactic environments.
    • Notes superlinear (for > ncrit) and linear (for < ncrit) LIR to Lprime correlation.
    • Notes constant SFR/M correlations observed (including our H2CO study).
  58. Krips, M., Neri, R., Garcia-Burillo, S., Martin, S., Combes, F., Gracia-Carpio, J., & Eckart, A. 2007, ApJ, in press, "A Multi-Transition HCN and HCO+ Study of 12 Nearby Active Galaxies: AGN Versus SB Environments"
    • Nice comparison of AGN, SB and AGN+SB sources as evidenced by their HCN and HCO+ ratios. Find that:
      • HCN and HCO+ intensity ratios vary significantly between SB and AGN.
        • Higher-J transitions are stronger in SB-dominated sources.
        • HCO+/HCN is higher in SB-dominated sources.
      • Higher gas densities (10^(4-6.5) cm^(-3)), kinetic temperatures (20-120 K), and HCN abundances (Z(HCN) ~= (0.001-2)x10^(-8)) in SB-dominated objects.
      • Lower gas densities (<10^(4.5) cm^(-3)), kinetic temperatures (>40 K), and HCN abundances (Z(HCO+) ~= (0.1-10)x10^(-7)) in AGN-dominated objects.
      • The low HCO+/HCN abundance ratios found in AGN-dominated objects make it unlikely that non-collisional excitation plays a significant role in HCN and HCO+ emission in AGN.
      • The overabundance of HCN in AGN sources indicates that the correlation between SFR and HCN luminosity may be violated in the vicinity of an AGN.
  59. Darling, J. 2007, ApJ, in press, "A Dense Gas Trigger for OH Megamasers"
  60. Baan, W., Henkel, C., Loenen, A. F., Baudry, A., and Wiklind, T. 2008, A&A, 477, 747, "Dense Gas in Luminous Infrared Galaxies".
    • Very nice analysis of PDR/XDR contribution to starburst evolution.
    • Present a model which explains starburst evolution in terms of consumption of high-density gas.
    • OH MMs and other powerful ULIRGs are mostly characterized by PDR-dominance.
  61. Papovich etal. 2007, ApJ, 668, 45, "Spitzer Mid- to Far-Infrared Flux Densities of Distant Galaxies".
  62. Armus etal. 2007, ApJ, 656, 148-167, "Observations of Ultraluminous Infrared Galaxies with the Infrared Spectrograph on the Spitzer Space Telescope. II. The IRAS Bright Galaxy Sample". Find hot gas/dust components in several ULIRGs (some of which we have measured H2CO in).
  63. Papadopoulos, P. P. 2007, ApJ, 656, 792, "HCN Versus HCO+ as Dense Molecular Gas Mass Tracers in Luminous Infrared Galaxies". Basically points out the problems in using HCO+ and ground-state transitions of linear molecules for derivation of physical conditions.
  64. Hao, L. etal. 2007, ApJ, 655, L77, "The Distribution of Silicate Strength in Spitzer Spectra of AGNs and ULIRGs".
  65. Greve etal. 2006, ApJ, 132, 1938, "A Search for Dense Gas in Luminous Submillimeter Galaxies with the 100 m Green Bank Telescope".
  66. Riechers etal. 2006, ApJ, 650, 604, "CO(1-0) in Z >= 4 Quasar Host Galaxies: No Evidence for Extended Molecular Gas Reservoirs".
  67. Laurent etal. 2006, ApJ, 643, 38, "The Bolocam 1.1 mm Lockman Hole Galaxy Survey: SHARC II 350 Micron Photometry and Implications for Spectral Models, Dust Temperatures, and Redshift Estimation".
  68. Tacconi etal. 2006, ApJ, 640, 228, "High-Resolution Millimeter Imaging of Submillimeter Galaxies". Suggest that SMGs are scaled-up versions of local ULIRGs.
  69. Yun, M. S. & Carilli, C. L. 2002, ApJ, 568, 88, "Radio-to-Far-Infrared Spectral Energy Distribution and Photometric Redshifts for Dusty Starburst Galaxies". Relies on fitting template derived from measured SMGs to estimate distant SMG redshifts.
  70. Dunne etal. 2000, MNRAS, 315, 115, "The SCUBA Local Universe Galaxy Survey - I. First Measurements of the Submillimetre Luminosity and Dust Mass Functions".

Abell 851

  1. Oemler, A. Jr. etal. 2009, ApJ, 693, 152, "Abell 851 and the Role of Starbursts in Cluster Galaxy Evolution"


  1. Lisenfeld, U. etal. 2007, Submitted to Elsevier, "Molecular Gas in Arp94: Implications for Intergalactic Star Formation". Interesting analysis of the merger state of Arp94.


  1. Batejat, F., etal. 2011, ApJ, 740, 95, "Resolution of the Compact Radio Continuum Sources in Arp220"
    • The compact radio continuum sources in Arp220 mostly comprise a mixed population of SNe and SNRs.
    • The observed size boundary between SNe and SNRs is consistent with an ISM density of ~10^4 cm^{-3}.
    • Find more SNE/SNR in W nucleus than E nucleus.
    • Data are consistent with the relation L propto D^{-9/4}.
    • All six of the detected SNRs are resolved with diameter > 0.27 pc, while all of the SNe (except E14 which has a size of 0.30 pc) have sizes < 0.2 pc.
  2. Martin, S. etal. 2011, A&A, 527, A36, "The Submillimeter Array 1.3 mm Line Survey of Arp 220"
    • Suggest that the chemical composition of Arp220 shows no clear evidence of an AGN impact on the molecular gas, and that the molecular emission is indicative of a pure starburst-heated ISM. Evidence for this supposition, though, seems rather thin.
  3. Greve, T. R., Papadopoulos, P. P., Gao, Y., and Radford, S. J. E. 2009, ApJ, 692, 1432, "Molecular Gas in Extreme Star-Forming Environments: The Starbursts Arp 220 and NGC 6240 as Case Studies"
  4. Aalto, S., Wilner, D., Spaans, M., Wiedner, M. C., Sakamoto, K., Black, J. H., and Caldas, M. 2009, A&A, 493, 481, "High-Resolution HNC 3-2 SMA Observations of Arp 220"
    • Find maser-looking profile toward western nucleus and suggest two scenarios for pumping.
    • Collisional model a bit hard to understand given lack of collisional oddities in HCN.
  5. Downes, D. and Eckart, A. 2007, A&A, in press, "Black Hole in the West Nucleus of Arp 220".
    • PdBI 0.3 arcsec 230 GHz dust and CO 2-1 emission measurements.
    • Find Tb(1.3mm dust) = 90 K. Implies that 90K <= Tk <= 180K.
    • CO exists in a torus around the dust core.
    • Simple size/density/mass arguments point to necessity for a BH in the west nucleus core.
  6. Scoville, N. Z., Yun, M. S., & Bryant, P. M. 1997, ApJ, 484, 702, "Arcsecond Imaging of CO Emission in the Nucleus of Arp 220".


  1. Alonso-Herrero, A. etal. 2009, ApJ, 697, 660 "The Extreme Star Formation Activity of Arp 299 Revealed by Spitzer IRS Spectral Mapping"
    • May be a local example of a high-z ULIRG.


  1. Daddi, E., Dannerbauer, H., Krips, M., Walter, F., Dickinson, M., Elbaz, D., and Morrison, G. E. 2009, ApJ, 695, L176, "A CO Emission Line From the Optical and Near-IR Undetected Submillimeter Galaxy GN10"
    • Galaxy at z = 4.04 with no detectable starlight (invisible in the optical), no detectable dust continuum, but strong CO 4-3 emission.
    • Appears to be a highly-obscured (Av ~ 5-7.5 mag) SMG.


  1. Montero-Castagno, M., Herrnstein, R. M., & Ho, P. T. P. 2006, ApJ, 646, 919-928, "Hot Molecular Gas in the Nuclear Region of IC 342"
  2. Usero, A., Garcia-Burillo, S., Martin-Pintado, J., Fuente, A., & Neri, R. 2006, A&A, 448, 457, "Large-Scale Molecular Shocks in Galaxies: The SiO Interferometer Map of IC 342"

IRAS 04296+2923

  1. Meier, D. S., Turner, J. L., Beck, S. C., Gorjian, V., Tsai, C-W., and Van Dyk, S. D. 2010, AJ, 140, 1294, "First Views of a Nearby LIRG: Star Formation and Molecular Gas in IRAS 04296+2923"
    • Barred spiral located behind TMC (hence rarely studied).
    • Most intense CO emission is extended over a 15 arcsec (2 kpc) diameter region, but nuclear starburst appears to be confined to a size within 1-2 arcsec (150-250 pc) of the dynamical center.
    • Appear to be witnessing an early stage of starburst/bar inflow induced secular evolution in this object (otherwise the bulge would be much larger and the disk would be depleted of its gas).

IRAS 19254-7245 (Superantennae)

  1. Bendo, G. J., Clements, D. L., and Khan, S. A. 2009, MNRAS, in press, "Spectroscopically- and spatially-resolved optical line emission in the Superantennae (IRAS 19254-7245)"


  1. Carilli etal. 2007, ApJ, 666, L9-L12, "Detection of 1.6X10^(10) Msolar of Molecular Gas in the Host Galaxy of the z=5.77 SDSS Quasar J0927+2001". Excellent discussion of the properties of high-z galaxies and their possible evolution.


  1. Hitschfeld, M., Kramer, C., Schuster, K. F., Garcia-Burillo, S., and Stutzki, J. 2009, A&A, 495, 795, "A complete 12CO 2-1 map of M 51 with HERA. II. Total gas surface densities and gravitational stability"
  2. Schuster, K. F., Kramer, C., Hitschfeld, M., Garcia-Burillo, S., and Mookerjea, B. 2007, A&A, 461, 143, "A complete 12CO 2-1 map of M 51 with HERA. I. Radial averages of CO, H I, and radio continuum"
  3. Brunner, G., Sheth, K., Armus, L., Wolfire, M., Vogel, S., Schinnerer, E., Helou, G., Dufour, R., Smith, J.-D., and Dale, D. A. 2008, ApJ, 675, 316, "Warm Molecular Gas in M51: Mapping the Excitation Temperature and Mass of H2 with the Spitzer Infrared Spectrograph"
    • Strip-mapped H2 S(0) through S(5) pure rotational emission in M51.
    • Find warm (T=100-300 K) and hot (T=400-1000 K) gas associated with the spiral arms and nucleus. Likely tracing PDRs.


  1. Meier, D. S., Turner, J. L., and Hurt, R. L. 2007, ApJ, in press, "Nuclear Bar Catalyzed Star Formation: 13CO, C18O, and Molecular Gas Properties in the Nucleus of Maffei 2"
    • Find that HCN is more confined to galaxy center than CO.
    • Confirms double-bar structure in nucleus.
    • Derive only moderate densities and kinetic temperatures of ~10^3 and 20-30 K (but note that Henkel etal. 2000 derive Trot(NH3) = 85 K using NH3(4,4), suggesting the existence of a warm component).

Markarian 938

  1. Esquej, P. etal. 2012, MNRAS, in press, "The Starburst-AGN Connection in the Merger Galaxy Mrk 938: An Infrared and X-Ray View"
    • Gind that the AGN contribution to the total bolometric continuum emission is very small: 2(+2)(-1)%.


  1. Brouillet etal. 2005, A&A, 429, 153, "HCN and HCO+ Emission in the Disk of M31".


  1. Nikola, T. etal., 2012, ApJ, 749, L19, "Mid-IR FORCAST/SOFIA Observations of M82"
    • Find Td = 68 K, which is consistent with our Tk derived from NH3 (58+-19 K).
  2. Kamenetzky, J. etal. 2011, ApJ, 753, 70, "Herschel-SPIRE Imaging Spectroscopy of Molecular Gas in M82"
    • CO and 13CO J=4-3 to 13-12 RADEX excitation analysis using Bayesian statistical minimization to derive cool/warm component fits with:
      • Tk = 63 / 447 K
      • log(n(H2)) = 3.40 / 4.10 cm^(-3)
      • log(N(CO)) = 18.56 / 17.96 cm^(-2)
      • log(M(H2)) = 7.31 / 6.11 Msolar
    • No temperature or density gradients can be inferred from their map measurements, suggesting that the single-pointing (deep) spectrum they used to constrain their physical conditions is descriptive of the bulk properties of the galaxy.
    • Shocks and turbulent heating are likely required to explain the bright high-J emission.
    • Note that the tidal interaction with M81 was likely very effective in removing cold interstellar dust from the disk. More than two-thirds of teh extraplanar dust follows the tidal streams emanating from M82.
    • Noting the bright embedded continuum in M82 they ran models which included the ~100 Jy / 43 arcsec (Jy sr^(-1)) continuum and found that it makes no difference to models which included only the 2.73 CMB. This is due to the fact that at ~500 K collisions dominate over radiative excitation, so the additional continuum does nothing to the overall excitation of the molecule.
    • Derive 12CO/13CO = 35, consistent with previous results.
    • Noted that Rigopoulou etal. (2002) found that "warm" gas is generally around 1% to 10% of the total gas mass for starburst galaxies.
    • Map suggest that their SPIRE FTS measurements cannot resolve M82's structure.
    • Also suggest that the dust and gas are not coupled. (This seems odd)
    • Note that they used RADEX, which means that n(H2;LVG) = 1.6*n(H2;RADEX).
    • These results derive much lower densities, even for the cool (63 K) component, than that derived previously (i.e. by Loenen etal. 2010 and us!). Not clear to me why they derive significantly lower spatial density (log(n(H2)) ~ 3.4 cm^(-3)) than use (log(n(H2)) ~ 5.0 cm^(-3)).
    • Is it possible that the CO is optically thick, so that it is only seeing a lower density component, than that measured by less-abundant molecules (like H2CO)?
  3. Loenen, A. F. etal., 2010, A&A, 521, L2, "Excitation of the Molecular Gas in the Nuclear Region of M82"
  4. Weiss, A. etal., 2010, A&A, 521, L1, "HIFI Spectroscopy of Low-Level Water Transitions in M82"
    • Find that the (ionised) water absorption arises from a ~2000 pc2 region within the HIFI beam located about ~50 pc east of the dynamical centre of the galaxy. This region does not coincide with any of the known line emission peaks that have been identified in other molecular tracers, with the exception of HCO. Our data suggest that water and ionised water within this region have high (up to 75%) area-covering factors of the underlying continuum. This indicates that water is not associated with small, dense cores within the ISM of M 82 but arises from a more widespread diffuse gas component. This seems strange to me!
  5. Aladro, R. etal., 2011, A&A, "A lambda = 1.3 mm and 2 mm molecular line survey towards M82"
  6. Gandhi, P. etal. 2011, PASJ, 63, 505, "Diffraction-Limited Subaru Imaging of M82: Sharp Mid-Infrared View of the Starburst Core"
    • Evidence of two Tk components at 45 and 160 K.
  7. Lacki, B. C., Thompson, T. A., Quataert, E., Loeb, A., and Waxman, E. 2011, ApJ, 734, A107, "On the GeV and TeV Detections of the Starburst Galaxies M82 and NGC253"
    • Underestimate n by ~100, which results in an incorrect estimate for t_pi.
  8. Tsai, C.-W. etal. 2009, AJ, 137, 4655, "Locating the Youngest HII Regions in M82 with 7mm Continuum Maps"
  9. Leeuw, L. and Robson, E. I. 2009, AJ, 137, 517, "Submillimeter Continuum Properties of Cold Dust in the Inner Disk and Outflows of M 82".
    • Compare merged new and archival 350, 450, 750, and 850 micron images of M82 with CO 1-0 and 2-1 and optical imaging.
    • Show that the 850 micron emission is just as extended as CO 2-1, in contrast to previous suggestions of a less-extended dust emission distribution.
    • See differences in dust and gas morphology, which they attribute to variations in dust-to-gas ratios.
    • Note (as have earlier studies) that CO emission is a significant contributor to some of the continuum imaging measurements.


  1. Rupke, D. S. N. and Veilleux, S. 2011, ApJL, 729, L27, "Integral Field Spectroscopy of Massive, Kiloparsec-scale Outflows in the Infrared-luminous QSO Mrk 231"
  2. Gonzalez-Alfonso, E. etal. 2007, ApJ, in press, "High-Excitation OH and H2O Lines in Markarian 231: The Molecular Signatures of Compact Far-Infrared Continuum Sources"
  3. Papadopoulos, P. P., Isaak, K. G., and van der Werf, P. P. 2007, ApJ, 668, 815, "First CO J=6-5 and J=4-3 Detections in Local ULIRGs: The Dense Gas in Markarian 231 and its Cooling Budget"


  1. Heesen, V. etal. 2011, A&A, 535, A79, "Cosmic Rays and the Magnetic Field in the Nearby Starburst Galaxy NGC253 III: Helical Magnetic Fields in the Nuclear Outflow"
  2. Mitsuishi, I. etal. 2011, ApJ, 742, L31, "Fe K Line Complex in the Nuclear Region of NG253"
    • Hot gas measurement.
    • Emission distributed over 60 arcsec^2 around the nucleus, suggesting that the source of the hot gas emission is not a nuclear AGN.
  3. Davidge, T. J. 2011, ApJ, 725, 1342, "Shaken, Not Stirred: The Disrupted Disk of the Starburst Galaxy NGC 253"
    • Suggests that the disk of NGC253 was disrupted by a tidal encounter with a now defunct companion.
  4. Sakamoto, K., Mao, Rui-Qing, Matsushita, S., and Peck, A. B. 2011, ApJ, 735, A19, "Star-Forming Cloud Complexes in the Central Molecular Zone of NGC253"
    • Measure opticall-thick Tb ~ 50 K, which approximates Tk.
  5. Lacki, B. C., Thompson, T. A., Quataert, E., Loeb, A., and Waxman, E. 2011, ApJ, 734, A107, "On the GeV and TeV Detections of the Starburst Galaxies M82 and NGC253"
    • Underestimate n by ~100, which results in an incorrect estimate for t_pi.
  6. Brunthaler, A., Castangia, P., Tarchi, A., Henkel, C., Reid, M. J., Falcke, H., and Menten, K. M. 2009, A&A, 497, 103, "Evidence of a pure starburst nature of the nuclear region of NGC 253"
    • No compact 22 GHz continuum emission detected.
    • Water maser emission is not related to a possible low-luminosity AGN, but is almost certainly associated with star formation activity.
    • Maser emission exhibits significant variability on timescales of years.
    • Maser emission positionally associated with source TH4, which is not the central radio source (which is TH2). TH4 is possibly a SNR.
  7. Knudsen etal. 2007, ApJ, 666, 156, "New Insights on the Dense Molecular Gas in NGC253 as Traced by HCN and HCO+".
    • Very nice analysis of very good HCN and HCO+ images (OVRO and APEX) of NGC253.
    • HCN/HCO+ ratio measured to be 1.0 throughout.
    • Further analyze recent claims of a dependence of L(HCN)/L(HCO+) on LIR and find, if data from the literature is included, that there really is no trend (contrary to claim made by Gracia-Carpio etal. (2006)).
    • Also find that both molecules are subthermally excited, but optically thick. In this case, the constant abundance ratio implies that there are no strong abundance gradients across the starburst disk in NGC253.


  1. Kamenetzky, J. etal. 2011, ApJ, 731, 83, "The Dense Molecular Gas in the Circumnuclear Disk of NGC 1068"
    • Majority of line ratios measured are consistent with XDR models.
  2. Krips, M. etal. 2011, ApJ, 736, A37, "Submillimeter Array/Plateau de Bure Interferometer Multiple Line Observations of the Nearby Seyfert 2 Galaxy NGC 1068: Shock-related Gas Kinematics and Heating in the Central 100 pc?"
    • XDR versus high-Tk noted, but no conclusion reached?
    • Both high-Tk and XDR can explain high HCN and CO ratios.


  1. Hsieh, P.-Y. etal. 2012, ApJ, 747, 90, "Probing Circumnuclear Environments with the HCN (J=3-2) and HCO+ (J=3-2) Lines: Case of NGC1097"


  1. Sakamoto, K., Ho, P. T. P., Mao, R.-Q., Matsushita, S., and Peck, A. B. 2007, ApJ, 654, 782, "Detection of CO Hot Spots Associated with Young Clusters in the Southern Starburst Galaxy NGC 1365"
    • Very nice images of NGC1365 in 12CO, 13CO, and C18O 2-1 and 1.3mm continuum.
    • Identify several CO clumps which corresponding IR and radio continuum sources.
    • Clear evidence for bar dynamics in CO velocity structure.
    • Usual problems with clear interpretation of CO excitation conditions (i.e. it is not specific to a single set of physical conditions).


  1. Combes, F., etal. 2009, A&A, 503, 73, "Molecular Gas in NUclei of GAlaxies (NUGA). XII. The Head-On Collision in NGC 1961"


  1. Hunt, L. K., Combes, F., Garcia-Burillo, S., Schinnerer, E., Krips, M., Baker, A. J., Boone, F., Eckart, A., Leon, S., Neri, R., and Tacconi, L. J. 2008, A&A, in press, "Molecular Gas in NUclei of GAlaxies (NUGA) IX. The Decoupled Bars and Gas Inflow in NGC 2782"
    • PdBI+30m CO 1-0 and 2-1 images of NGC 2782, a barred-early-type-spiral with starburst.
    • Find clear evidence of gas inflow on a very small scale (few hundred pc), where they also find CO emission down to the spatial resolution of the measurements.
  2. Salter, C. J., Ghosh, T., Catinella, B., Lebron, M., Lerner, M. S., Minchin, R., and Momjian, E. 2008, AJ, 136, 389, "The Arecibo Arp220 Spectral Census. I. Discovery of the Pre-Biotic Molecule Methanimine and New CM-Wavelength Transitions of Other Molecules"
    • Detect Methanimine (CH2NH), vibrationally-excited HCN, either 18OH or formic acid (HCOOH), and possibly three transitions from OH not detected before.
    • Suggest that CH2NH is weak maser "like H2CO", but this is not convincing (based only on brightness temperature argument).


  1. Leon, S., Jeyakumar, S., Perez-Ramirez, D. Verdes-Montenegro, L., Lee, S. W., and Ocana Flaquer, B. 2008, A&A, 491, 703 "HCN(1-0) Enhancement in the Bar of NGC 2903"
    • Did not consider thermal bottleneck!


  1. Impellizzeri, C. M. V., Henkel, C., Roy, A. L., and Menten, K. M. 2008, A&A, 484, L43, 6.7 GHz methanol absorption toward the Seyfert 2 galaxy NGC 3079
    • Compare H2CO to NH3.
    • Suggest that CH3OH is absorbing the radio continuum from continuum sources A, B, and E.
    • One absorption feature is narrow at the systemic velocity of NGC3079, so may arise from gas not related to the nuclear environment of the galaxy.
    • Weaker blue-shifted component is wider and may trace outflowing gas.


  1. Casasola, V., Combes, F., Garcia-Burillo, S., Hunt, L. K., Leon, S., and Baker, A. J. 2008, A&A, 490, 61 "Molecular Gas in NUclei of GAlaxies (NUGA) X. The Seyfert 2 Galaxy NGC 3147

NGC4038/4039 (The Antennae)

  1. Herrera, C. N. etal. 2012, A&A, in press "ALMA CO and VLT/SINFONI H2 Observations of the Antennae Overlap Region: Mass and Energy Dissipation"


  1. Hermelo, I. etal. 2011, To appear in 'The Spectral Energy Distribution of Galaxies' Proceedings IAU Symposium No 284, 2011, "Modeling the Dust Spectral Energy Distribution of NGC 4214"


  1. Zastrow, J., Oey, M. S., Veilleux, S., McDonald, M., and Martin, C. L. 2011, ApJ, 741, L17, "An Ionization Cone in the Dwarf Starburst Galaxy NGC5253"


  1. Hagiwara, Y., Baan, W. A., and Kloeckner, H.-R. 2011, ApJ, 142, A17, "Very Long Baseline Interferometry Observations of NGC6240: Resolving the Double Nuclei and Radio Supernovae"
  2. Iono etal. 2007, ApJ, in press, "High Resolution Imaging of Warm and Dense Molecular Gas in the Nuclear Region of the Luminous Infrared Galaxy NGC6240". Very nice "tour-de-force" study of the nuclear region of NGC6240. Find dense gas (CO and HCO+) emission concentrated to the region between the two (AGN) nuclei. Also note that Mg/Mdust = 200-300 for local LIRGs/ULIRGs, 15-231 for high-z sources, and 100 for Galactic sources. Mg/Mdust = 147+-57 in NGC6240. Very high concentrations of gas relative to dust.


  1. Lindt-Krieg, E., Eckart, A., Neri, R., Krips, M., Pott, J.-U., Garcia-Burillo, S., and Combes, F. 2008, A&A, 479, 377, "Molecular Gas in NUclei of GAlaxies (NUGA) VIII. The Seyfert 2 NGC 6574"
    • PdBI+30m CO 1-0 and 2-1 images of NGC 6574.
    • Find clear evidence of gas inflow on a very small scale (few hundred pc), where they also find CO emission down to the spatial resolution of the measurements.
    • Given the lack of a starburst, this gas inflow must be relatively young.


  1. Murphy, E. J. etal. 2011, ApJ, 737, 67, "Calibrating Extinction-Free Star Formation Rate Diagnostics with 33 GHz Free-Free Emission in NGC6946".
    • Excellent general description of SFR indicators with analytical equations.
  2. Braine, J., Ferguson, A. M. N., Bertoldi, F., and Wilson, C. D. 2007, ApJL, accepted, "The Detection of Molecular Gas in the Outskirts of NGC6946".
    • Detection of CO 1-0 and 2-1 toward outer HII regions in NGC6946.
    • Also report non-detection of outer-galaxy CO in NGC1058.
  3. Levine, E. S., Helfer, T. T., Meijerink, R., and Blitz, L. 2007, ApJ, accepted, "The Dense Gas in the Central Kiloparsec of NGC6946".
    • HCN 1-0 images of NGC6946.


  1. van der Laan, T. P. R. etal. 2011, "Molecular gas in NUclei of GAlaxies (NUGA). XV. Molecular gas kinematics in the inner 3 kpc of NGC 6951"


  1. Nikola, T. etal. 2011, ApJ, 742, 88, "Mid-J CO Emission from NGC891: Microturbulent Molecular Shocks in Normal Star-Forming Galaxies"
    • Shock plus PDR model used to explain observations
    • Why can't high-J CO be due to high density warm gas?


  1. Weiss, etal. 2005, A&A, 440, L45, "Multiple CO Lines in SMM J16359+6612 - Further Evidence for a Merger". Nice analysis of the evidence for a merger in this high-Z object.


  1. Haan, S. etal. 2011, ApJS, 197, 27, "Spitzer IRS Spectral Mapping of the Toomre Sequence: Spatial Variations of PAH, Gas, and Dust Properties in Nearby Major Mergers"
    • Measure very high (Tk =~ 100-1000 K) temperatures.
    • H2 and hot gas not concentrated toward merger overlap regions (odd?).
  2. Robaina, A. R. etal. 2009, ApJ, 704, 324, "Less Than 10 Percent of Star Formation in z ~ 0.6 Massive Galaxies is Triggered by Major Interactions"
    • Major mergers in the local universe are not significant contributors to the SFR enhancement.
  3. Kuo, C.-Y., Lim, J., Tang, Y.-W., and Ho, P. T. P., 2008, ApJ, 679, 1047, "Prevalence of Tidal Interactions among Local Seyfert Galaxies"
    • Use VLA HI images to characterize merger signatures in Seyfert galaxies.
    • Find that about ~67%, and perhaps up to ~94%, of their sample show disturbed HI morphologies, suggestive of mergers.
  4. Tang, Y.-W., Kuo, C.-Y., Lim, J., and Ho, P. T. P., 2008, ApJ, 679, 1094, "Prevalence of Tidal Interactions among Local Seyfert Galaxies: The Control Experiment"
    • Control experiment for reference above.
    • Looked at 27 inactive galaxies in HI to see if they too show disturbed HI morphologies.
    • Find that only ~18% of their control sample show disturbed HI morphologies.

General Exgal

  1. Tacconi, L. J., etal. 2010, Nature, 463, 781, "High Molecular Gas Fractions in Normal Massive Star-Forming Galaxies in the Young Universe"
  2. Darling, J., & Zeiger, B. 2012, ApJL, 749, L33, "Fomaldehyde Silhouettes Against the Cosmic Microwave Background: A Mass-Limited, Distance-Independent, Extinction-Free Tracer of Star Formation Across the Epoch of Galaxy Evolution"
    • Contains comparison to Troscompt H2CO excitation rates.
  3. Ade, P. A. R. etal. 2011, A&A, 536, A15, "Planck Early Results. XV. Spectral Energy Distributions and Radio Continuum Spectra of Northern Extragalactic Radio Sources"
    • Detailed modeling of radio (synchrotron) portion of SED.
    • Flat synchrotron spectra due to hard initial energy distribution.
  4. Ade, P. A. R. etal. 2011, A&A, 536, A16, "Planck Early Results. XVI. The Planck View of Nearby Galaxies"
    • From analysis of Planck Early Release Compact Source Catalog (ERCSC).
    • Find significant amounts of cold (T < 20 K) dust. Conclude that this cold dust is a significant and largely unexplored component of many nearby galaxies.
  5. Skibba, R. A. etal. 2011, ApJ, 738, 89, "The Emission by Dust and Stars of Nearby Galaxies in the Herschel Kingfish Survey"
  6. van der Kruit, P. C. and Freeman, K. C., ARA&A, 49, 301, "Galaxy Disks"
  7. Carilli, C. L. 2011, 2011, 730, L30, "Intensity Mapping of Molecular Gas During Cosmic Reionization"
  8. Minamidani, T. etal. 2011, AJ, 141, A73, "Dense Clumps in Giant Molecular Clouds in the Large Magellanic Cloud: Density and Temperature Derived from 13CO(J = 3-2) Observations"
    • CRAP! No way one can derive density and temperature from 13CO 3-2.
  9. Carilli, C. L. etal. 2011, Review for the Astronomische Gesellschaft to appear in Astronomische Nachrichten, "Radio Studies of Galaxy Formation: Dense Gas History of the Universe"
  10. Zeiger, B. and Darling, J. 2010, ApJ, 709, 386, "Formaldehyde Anti-Inversion at z = 0.68 in the Gravitational Lens B0218+357"
  11. Willmer, C. N. A. etal. 2009, AJ, 138, 146, "Spitzer Observations of Cold Dust Galaxies"
    • Find that SLUGS galaxies (submillimeter survey with SCUBA) have a warm dust component with a median temperature of Tw = 54.7+-1.7 K and a colder one with Tc = 18.5+-1.1 K.
  12. Dressler, A. etal. 2009, ApJ, 699, L130, "Evolution of the Rate and Mode of Star Formation in Galaxies Since z = 0.7"
    • Find a precipitous decline in SFR since z = 1, in agreement with other studies, as well as corresponding rapid decline in the fraction of galaxies undergoing long-duration moderate-amplitude starbursts.
  13. Dobbs, C. L. and Pringle, J. E. 2009, MNRAS, 396, 1579, "A simple model for the relationship between star formation and surface density"
    • Use a simple model for the dependence of H2 fraction on total surface density to argue why neither total surface density nor the HI surface density are good indicators of star formation rate.
  14. Wilson, C. D. etal. 2009, ApJ, 693, 1736, "The James Clerk Maxwell Telescope Nearby Galaxies Legacy Survey. I. Star-Forming Molecular Gas in Virgo Cluster Spiral Galaxies"
  15. Dannerbauer, H. etal. 2009, ApJ, 698, L178, "Low Milky-Way-Like Molecular Gas Excitation of Massive Disk Galaxies at z ~ 1.5"
  16. Tacconi, L. J. etal. 2008, ApJ, 680, 246, "Submillimeter Galaxies at z ~ 2: Evidence for Major Mergers and Constraints on Lifetimes, IMF, and CO-H2 Conversion Factor"
  17. Manthey, E., Huttemeister, S., Aalto, S., Horellou, C., and Bjerkeli, P. 2008, A&A, 490, 975, "Stars and Gas in the Medusa Merger".
  18. Leroy, A. K. etal. 2009, ApJ, 137, 4670, "HERACLES: The HERA CO Line Extragalactic Survey".
  19. Henkel, C., Braatz, J. A., Menten, K. M., and Ott, J. 2008, A&A, 485, 451, "The Kinetic Temperature of a Molecular Cloud at Redshift 0.9: Ammonia in the Gravitational Lens PKS 1830-211".
  20. Sheth, K., etal. 2008, ApJ, 675, 1141, "Evolution of the Bar Fraction in COSMOS: Quantifying the Assembly of the Hubble Sequence".
    • Study bar fraction within 2157 luminous face-on spiral galaxies covering redshift 0.2 < z < 0.84.
    • Bar fraction drops from about 65% in the local universe to about 20% at z ~ 0.84.
    • Suggest that warm, merger-rich environment in early universe quenches bar formation at higher z.

Dwarf Galaxies

  1. Madden, S. C. etal. 2011, EAS Publications Series, Volume 52, 2011, pp.95-101, "The Illusive ISM of Dwarf Galaxies: Excess Submillimetre Emission & CO-Dark Molecular Gas".
    • Comparing drawf to normal galaxies:
      1. The abundance of PAHs relative to total dust mass is much lower
      2. Relatively warmer dust is often present over galaxy-wide scales, with a characteristically steeply rising mid-infrared (MIR) dust continuum and spectral energy distributions (SEDs) often peaking at shorter wavelengths - typically between 40 to 60 μm
      3. Excess emission at submm wave- lengths is often seen > 400 μm, which has been attributed in the past to large masses of cold dust
      4. CO detections are challenging, making it difficult to deter- mine the molecular gas reservoir 5) ionic gas is prevalent, as seen from the high galaxy-wide [NeIII]/[NeII] line ratios.
    • Depending on certain conditions including the AV and radiation field, the self-shielding capability of H2 can leave a potentially significant reservoir of H2 in the C+-emitting region (Roellig et al. 2006; Wolfire et al. 2010; Shetty et al. 2010). This is the CO-dark molecular gas and the [CII] traces this ”missing” molecular gas that is not probed by the CO. Assuming the [CII] is tracing this CO-dark H2, 10 to100 times more H2 has been proposed to be ’hidden’ in the C+-emitting regions in dwarf galaxies compared to that inferred by CO (e.g. Poglitsch et al. 1995; Madden et al. 1997).


  1. Zafar, T. etal, 2011, A&A, 532, A143, "The Extinction Curves of Star-Forming Regions from z=0.1 to 6.7 Using GRB Afterglow Spectroscopy"

-- JeffMangum - 28 Aug 2008
Topic revision: r58 - 2012-12-30, JeffMangum
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