February 16, 2005

from: C. Carilli to: J. Turner re: DRSP and ALMA rebaseline cc: A. Wootten, A. Blain, P. Cox, T. Wilson

Jean,

Below are some notes concerning some of the extragalactic DRSPs in the context of ALMA rebaseline plan (64 to 50 antennas). Andrew Blain and Pierre Cox are considering the rest of themes in 1.1 to 1.6. I have put my notes at the end of each DRSP, starting with phrase: 'Effect of Re-baseline:'.

Some general comments:

1. I have had some exchange with Mark Holdaway on the effect of decreasing number of antennas on calibration capabilities. I attached that as a separate file (I think you may have been on the cc list already). In summary, rebaseline does not preclude standard calibration schemes for ALMA.

2. Most programs can be 'fixed' with just increased integration time. But, there may be a limit to this due to the onset of systematic errors (eg. due to troposphere or electronics), ie. the noise may not continue to decrease like root time for very long integration times. These are impossible to predict or quantify at this stage, and in the end, may not ever be an issue, but I point out the possibility where relevant.

3. A few programs are dynamic range limited, in which case the collecting area is not the issue, but the uv coverage is. Again, hard to quantify without simulations, but again, I point out the possibility where relevant.

4. I have one variable source program (IDVs), in which case in may not be possible to simply increase the integration time.

That's all from me. See you in Garching.

cc

================================================================

1.1.5: Name -- Molecular line studies of submm galaxies -- constraining dust obscured galaxy formation Authors: C. Carilli

2. Science goal: The discovery of the IR background, and the SCUBA/MAMBO population of dusty, star forming galaxies at high redshift, has transformed our understanding of galaxy formation. It is now clear that a significant fraction (of order 50%) of star formation in the cosmos occurs in galaxies that are heavily obscured by dust, and that this fraction may rise with redshift, possibly corresponding to the formation of spheroidal galaxies in active starbursts. One highly uncertain aspect of the study of submm galaxies is their redshift distribution. Optical redshifts remain problematic for the majority of such sources, and can be misleading due to possible mis-identifications. We propose a three part program -- (1) a 'blind' search for CO emission from a representative sample of submm galaxies to constrain their redshift distribution, (2) high resolution imaging of a sub-sample to determine the gas distribution and dynamics on sub-kpc scales and (ii) a search for HCN emission to search for dense gas directly associated with star formation. A representative sample of sources will be chosen from standard (sub)mm continuum surveys with large single dishes or by ALMA itself.

Part 1: Redshift search -- I assume redshifts will be 'narrowed-down' via photometric techniques (optical and/or radio) to +/- 0.5 in dz, and that the typical source redshift is between 2 and 3. Using band 3 then requires 3 settings between 90 and 116 GHz to get the CO(3-2) line. This will take about 1hr per source (see below). A second search will then be required to look for higher/lower order transitions to confirm the redshift. This will take another hour. This second search will also give some indication of CO excitation conditions. I assume the characteristic line flux density is of order 1 mJy.

Part 2: High resolution CO imaging -- I assume the characteristic source size is >= 1 kpc (0.2"), and intrinsic brightness temperature >= few K.

Part 3: HCN emission is typically 10x fainter than CO. To get a 4 sigma detection will then take of order 10hrs/source.

3. Number of sources: 50

4. Coordinates:

4.1. Any

4.2. Moving target: no

4.3. Time critical: no

5. Spatial scales:

5.1. Angular resolution: small configuration preferred - (1) and (3) A configuration for (2)

5.2. Range of spatial scales/FOV:

5.3. Single dish: no

5.4. ACA: no

5.5. Subarrays: no

6. Frequencies:

6.1. Receiver band: Band 3 -- initial search, high res imaging, HCN search Band 6 -- 220 GHz follow-up for redshift verification

6.2. Lines and Frequencies CO, HCN at z=1 to 5, various transitions

6.3. Spectral Resolution (km/s) 100 km/s

6.4. Bandwidth or spectral coverage: 8 GHz (for search)

7. Continuum flux density:

7.1. Typical value: 1 mJy

7.2. Continuum peak value:

7.3. Required continuum rms:

7.4. Dynamic range in image:

8. Line intensity:

8.1. Typical value: 1 mJy -- CO(3-2), 0.1mJy -- HCN

8.2. Required rms per channel: 100 GHz -- 0.14 mJy (20min), 0.026mJy (10hrs)
                      1. GHz -- 0.2 mJy Imaging -- T_B = 0.25 K at 0.2" res in
1hr note: this corresponds to intrinsic T_B = 0.9 K (1sigma) at z=2.5 8.3. Spectral dynamic range:

9. Polarization: no

10. Integration time per setting: (1a) Search -- 1/3hr per setting x 3 settings x 50 srcs with band 3 = 50hr (1b) 1 hr/src for verification x 50 sources with band 3 or 6 = 50 hr (2) CO imaging -- 1hr/src x 20 srcs with band 3 = 20 hr (3) 10 hr/src for HCN search for 5 sources with band 3 = 50 hr

11. Total integration time for program: 170

********************************************************************** Effect of Re-Baseline: Going from 64 to 50 antennas

This science is not fundamentally disabled by decrease in number of antennas. Just the integration times will have to be increased by a factor 1.64, or we could decrease the number of sources by this factor. Note that for the HCN search we are already at 5 sources. In this case we would want to keep 5 sources and go to 82 hrs. For these sources the new integration time per source is 16hrs, which may lead to some issues concerning systematics for long integrations when searching for faint broad lines.

**********************************************************************

1.3.1: Single DRSP

Last modified: Saturday, 18-Oct-2003 14:59:35 CEST

1. Name of program and authors

Spectral line survey in high-z molecular absorption systems Wiklind T., Combes F.

  1. One short paragraph with science goal(s)

Molecular line absorption in front of a radio continuum sources is a very powerful technique to detect even small quantities of interstellar molecules in external galaxies. It is also complementary to the emission technique: it samples molecules in low excitation state, that would never have been detected in emission. For galaxies at large distances, molecular absorption lines offer the only way to observe rare molecular species. This has been proven through the detection of many molecular species (about 20) at redshifts z=0.25-0.89, using pre-ALMA instrumentation. The sensitivity is largely determined by the strength of the background continuum source, meaning that a large collecting area is the main issue (the sources themselves remain point sources even at high angular resolution). The completion of ALMA makes it possible to make a spectral line survey to an unprecedented level of the molecular interstellar medium in distant galaxies.

We propose to carry on a complete molecular line survey (using the available frequency bands) towards 3 remarkable sources at different redshifts, in order to probe the interstellar chemistry and its evolution. Many different molecular species, such as CCH, C3H2, HOC+, SiC, deuterated species etc. are expected to be detected. A complete spectral line survey will allow a detailed comparison of the interstellar chemistry of these three distant sources with that of the Milky Way ISM. In addition, the survey will include several molecular lines which for Milky Way gas are not possible to observe from the ground; such as the ground transition of LiH and water vapor, as well as the elusive molecular oxygen.

Noise rms limits have been chosen such that over most of the available frequencies, absorption lines with depth of <1% of the continuum flux can be detected at 5sigma. Over some frequency intervals and for the stronger sources, this limit is set as low as 0.15%. This corresponds to column densities of CO and HCO+ of 910E12 and 1E10, respectively. It is possible that the density of lines will be large, possibly limiting the detections of individual lines through confusion over certain frequency intervals.

We propose to do a systematic survey in the 4 priority bands Band 3: 86 GHz - 116 GHz Band 6: 211 GHz - 275 GHz Band 7: 275 GHz - 370 GHz Band 9: 602 GHz - 720 GHz for 3 absorption systems already observed with IRAM and SEST, and visible from Chajnantor: PKS1830-211 (z=0.89) PKS1413+135 (z=0.25) CenA (z=0)

  1. Number of sources (e.g., 1 deep field of 4'x4', 50 YSO's,
                    1. T Tauri stars with disks, ...; do NOT list individual sources or your "pet object", except in special cases like LMC, Cen A, HDFS)

    1. sources PKS1830-211, PKS1413+135 and CenA (note that PKS1830-211 gives two sight lines through the intervening galaxy, separated by ~6 kpc).

  1. Coordinates:

    1. 1. Rough RA and DEC (e.g., 30 sources in Taurus, 30 in Oph, 20 in Cha, 30 in Lupus)

1830-211, 1413+135, 1325-43

Indicate if there is significant clustering in a particular RA/DEC range

(e.g. if objects in one particular RA range take 90% of the time)

NO

    1. 2. Moving target: yes/no (e.g. comet, planet, ...)

NO

    1. 3. Time critical: yes/no (e.g. SN, GRB, ...)

NO

  1. Spatial scales:

    1. 1. Angular resolution (arcsec):

All three targets are point sources for which the angular resolution does not really matter.

    1. 2. Range of spatial scales/FOV (arcsec): (optional: indicate whether single-field, small mosaic, wide-field mosaic...)

Single field per source.

    1. 3. Single dish total power data: yes/no

NO

    1. 4. ACA: yes/no

NO

    1. 5. Subarrays: yes/no

NO

  1. Frequencies:

    1. 1. Receiver band: Band 3, 6, 7, or 9

Band 3, 6, 7 and 9

    1. 2. Lines and Frequencies (GHz): (approximate; do NOT go into detail of correlator set-up but indicate whether multi-line or single line; apply redshift correction yourself; for multi-line observations in a single band requiring different frequency settings, indicate e.g. "3 frequency settings in Band 7" without specifying each frequency (or give dummies: 340., 350., 360. GHz). For projects of high-z sources with a range of redshifts, specify e.g. "6 frequency settings in Band 3". Apply redshift correction yourself)

This is a line survey. We will cover the entire extent of each band falling within atmospheric windows of sufficient transparency.

    1. 3. Spectral resolution (km/s):

    1. - 3 km/s

    1. 4. Bandwidth or spectral coverage (km/s or GHz):

Band 3: 2x1 GHz = 2 GHz, 1024 channels, ~3 km/s (17 tunings for entire band) Band 6: 4x1 GHz = 4 GHz, 512 channels, ~2.5 km/s (18 tunings for entire band) Band 7: 8x1 GHz = 8 GHz, 256 channels, ~3.3 km/s (13 tunings for entire band) Band 9: 8x1 GHz = 8 GHz, 256 channels, ~1.8 km/s (16 tunings for entire band)

  1. Continuum flux density:

    1. 1. Typical value (Jy): (take average value of set of objects) (optional: provide range of fluxes for set of objects)

Variable radio sources, Minimum 0.2 Jy, average around 1 Jy Estimated continuum fluxes used in time calculations:

PKS1413 PKS1830 Cen A

Band 3: 0.2 2.0 6.0 Band 6: 0.1 1.0 3.0 Band 7: 0.05 0.5 2.0 Band 9: 0.02 0.2 1.0

    1. 2. Required continuum rms (Jy or K):

The continuum rms is defined as the limit in percentage of the source continuum flux where an absorption line can be detected at 5sigma. The values in parenthesis are the actual channel to channel noise rms:

PKS1413 PKS1830 Cen A

Band 3: 1 (0.4 mJy) 0.1 (0.4 mJy) 0.05 (0.6 mJy) Band 6: 3 (6.0 mJy) 0.5 (1.0 mJy) 0.15 (0.9 mJy) Band 7: 5 (0.5 mJy) 1 (1.0 mJy) 0.5 (2.0 mJy) Band 9: 50 (2.0 mJy) 15 (6.0 mJy) 5 (10.0 mJy)

    1. 3. Dynamic range within image: (from 7.1 and 7.2, but also indicate whether e.g. weak objects next to bright objects)

no imaging is needed.

  1. Line intensity:

    1. 1. Typical value (K or Jy): (take average value of set of objects) (optional: provide range of values for set of objects)

in average 0.02 Jy (but can be much lower)

    1. 2. Required rms per channel (K or Jy):

See 7.2

    1. 3. Spectral dynamic range:

100

  1. Polarization: yes/no (optional)

no

    1. 1. Required Stokes

total intensity only

    1. 2. Total polarized flux density (Jy)

N/A

    1. 3. Required polarization rms and/or dynamic range

N/A

    1. 4. Polarization fidelity

N/A

  1. Integration time for each observing mode/receiver setting (hr):

Below the integration time is given as hour (per tuning/total time). This done for each band and source. Note that PKS1413 will only be observed using band 3 and 6.

PKS1413 PKS1830 Cen A

Band 3: 1.4/24 1.0/17 0.5/9 Band 6: 1.5/27 1.2/22 1.0/18 Band 7: 5.2/0 1.3/17 0.3/13 Band 9: 8.4/0 1.0/16 0.5/8

  1. Total integration time for program (hr):

171 hours + over-head

  1. Comments on observing strategy (e.g. line surveys, Target of Opportunity, Sun, ...): (optional)

This is a molecular line line survey. The observations are self-calibrated using the central continuum source. The pointing accuracy needs to be than 5". Very good weather conditions are only required for high frequency observations.

A homogeneous sensitivity is necessary in order to allow a comparative abundances study of weak lines.

The estimated time can be decreased by lowering the target sensitivity or only choosing PKS1830-211 and Cen A as targets. However, given the uniqueness of this data set, we would prompt for a significant time allocation.

********************************************************************** Effect of Re-Baseline: Going from 64 to 50 antennas

Again, this science is not fundamentally disabled by decrease in number of antennas. Just the integration times will have to be increased by a factor 1.64. In this case we cannot decrease the number of sources. Since this is a line survey, the dynamic range issues for long integrations is not an issue (ie. the program assumes lots of shorter integrations). Since this is a line survey (lots of short integrations at different frequencies and/or different sources), systematics and/or dynamic range limits for long integrations are not an issue.

**********************************************************************

1.3.2: Single DRSP

Last modified: Saturday, 18-Oct-2003 15:01:23 CEST

  1. Name of program and authors

A deep search for new molecular absorption line systems Wiklind T., Combes F.

  1. One short paragraph with science goal(s)

Observations of molecular absorption lines offer the only way to obtain detailed information of the physical and chemical parameters of the molecular interstellar medium in distant galaxies. The sensitivity is essentially only given by the strength of the background continuum source, independent of the distance.

Four molecular absorption line systems at redshifts between z=0.25-0.89 have previously been detected using single dish telescope, and allowed a detailed study of the astrochemistry of these systems, including molecular species never before observed from the ground. In addition, since molecular absorption is biased towards diffuse and therefore excitationally cold gas, the observations have made it possible to measure the temperature of the Cosmic Microwave Background radiation at the redshift of the absorber.

In order to make a comparative study of the chemical and physical status of the molecular gas at earlier epochs it is necessary to increase the number of known systems. Molecular absorption line systems are rare, about 100 times less common than damped Lyman-alpha systems. They are also difficult to detect since continuum fluxes of the background sources are relatively weak at mm/submm wavelenghts. Also, the mere presence of obscuration means that redshift information is lacking. This was the case for one of the known absorption systems and it was detected by the technique of frequency scanning, looking for absorption of high-opacity molecules such as CO and HCO+ (actually, the line first detected in this case turned out to be a HNC(2-1) line). By observing the frequency range 86-116 and 226-260 GHz, the entire redshift space is covered for CO and HCO+ lines. These are the lines with the highest opacities.

In this project we propose a search for molecular absorption towards ~70 selected radio loud AGNs with mm continuum fluxes greater than 50mJy. The targets will be prioritized according to a few criteria which enhances the probability for the presence of obscuration; such as gravitational lensing (small impact parameter to the lens), suppressed soft X-ray flux, optically weak and indications of reddening. In order to circumvent the missing or uncertain redshift information, we will search for absorption over the entire redshift range using the technique of frequency scanning.

Noise rms limits have been chosen such that band 3, which covers z=0-0.34 and z>0.54,m absorption lines with depth of 5% of the continuum flux can be detected at 5sigma. In band 6, covering z=0.34-0.54, the limits have been set to 10% at 3sigma in order to enable a large number of sources to have complete redshift coverage. With the velocity resolution given below, these limits corresponds to column densities of CO and HCO+ of 710E14 and 8E11 cm-2, respectively.

  1. Number of sources (e.g., 1 deep field of 4'x4', 50 YSO's,
                    1. T Tauri stars with disks, ...; do NOT list individual sources or your "pet object", except in special cases like LMC, Cen A, HDFS)

    1. flat spectrum radio continuum sources

  1. Coordinates:

    1. 1. Rough RA and DEC (e.g., 30 sources in Taurus, 30 in Oph, 20 in Cha, 30 in Lupus)

Source list can be selected such that there is any desired spread in RA and DEC.

Indicate if there is significant clustering in a particular RA/DEC range

(e.g. if objects in one particular RA range take 90% of the time)

NO

    1. 2. Moving target: yes/no (e.g. comet, planet, ...)

NO

    1. 3. Time critical: yes/no (e.g. SN, GRB, ...)

NO

  1. Spatial scales:

    1. 1. Angular resolution (arcsec):

All targets are point sources for which the angular resolution does not really matter.

    1. 2. Range of spatial scales/FOV (arcsec): (optional: indicate whether single-field, small mosaic, wide-field mosaic...)

Single field per source.

    1. 3. Single dish total power data: yes/no

NO

    1. 4. ACA: yes/no

NO

    1. 5. Subarrays: yes/no

NO

  1. Frequencies:

    1. 1. Receiver band: Band 3, 6, 7, or 9

Band 3 and 6

    1. 2. Lines and Frequencies (GHz): (approximate; do NOT go into detail of correlator set-up but indicate whether multi-line or single line; apply redshift correction yourself; for multi-line observations in a single band requiring different frequency settings, indicate e.g. "3 frequency settings in Band 7" without specifying each frequency (or give dummies: 340., 350., 360. GHz). For projects of high-z sources with a range of redshifts, specify e.g. "6 frequency settings in Band 3". Apply redshift correction yourself)

The aim is redshifted CO and HCO+ lines. By using the entire frequency range of band 3 (86-116 GHz) and part of band 6 (226-260 GHz), the entire redshift range is covered.

    1. 3. Spectral resolution (km/s):

Band 3: ~6 km/s Band 6: ~5 km/s

    1. 4. Bandwidth or spectral coverage (km/s or GHz):

Band 3: 4x1 GHz = 4 GHz, 512 channels, ~6 km/s (9 tunings for entire band) Band 6: 8x1 GHz = 8 GHz, 256 channels, ~5 km/s (5 tunings for 226-260 GHz)

  1. Continuum flux density:

    1. 1. Typical value (Jy): (take average value of set of objects) (optional: provide range of fluxes for set of objects)

    1. sources with fluxes 50 - 100 mJy
    2. sources with fluxes 100 - 200 mJy
    3. sources with fluxes >200 mJy

    1. 2. Required continuum rms (Jy or K):

We aim at being able to detect an absorption at 5sigma at 5% of the continuum level in band 3 and at 10% and 3sigma in band 6. For a source with a background continuum of 100 mJy this corresponds to a 1sigma noise rms of 1 mJy.

The continuum rms is defined as the limit in percentage of the source continuum flux where an absorption line can be detected at 5sigma:

    1. 3. Dynamic range within image: (from 7.1 and 7.2, but also indicate whether e.g. weak objects next to bright objects)

no imaging is needed.

  1. Line intensity:

    1. 1. Typical value (K or Jy): (take average value of set of objects) (optional: provide range of values for set of objects)

See 7.2

    1. 2. Required rms per channel (K or Jy):

See 7.2

    1. 3. Spectral dynamic range:

100

  1. Polarization: yes/no (optional)

no

    1. 1. Required Stokes

total intensity only

    1. 2. Total polarized flux density (Jy)

N/A

    1. 3. Required polarization rms and/or dynamic range

N/A

    1. 4. Polarization fidelity

N/A

  1. Integration time for each observing mode/receiver setting (hr):

Below are integration times to reach a 5sigma rms of 5% of the background source continuum for band 3, and a 3sigma of 10% of the continuum in band 6. The targets are divided into approximately 10 sources with flux densities in the range 50-100 mJy, 30 sources with 100-200 mJy and 30 sources with 100-200 mJy.

Flux 50 mJy band 3: 0.9h/tuning, 9 tunings/source, ~9 hours/source band 6: 1.0h/tuning, 5 tunings/source, ~5 hours/source

Flux 100 mJy band 3: 0.2h/tuning, 9 tunings/source, ~1.8 hours/source band 6: 0.3h/tuning, 5 tunings/source, ~1.5 hours/source

Flux 200 mJy band 3: 0.06h/tuning, 9 tunings/source, ~0.5 hours/source band 6: 0.07h/tuning, 5 tunings/source, ~0.4 hours/source

Average total integration times :
        1. -100 mJy: 5 hours per source, total = 50 hours 100-200 mJy: 2 hours per source, total = 60 hours >200 mJy : 0.5 hours per source, total = 15 hours

  1. Total integration time for program (hr):

125 hours + over-head

  1. Comments on observing strategy (e.g. line surveys, Target of Opportunity, Sun, ...): (optional)

Targets will be radio loud AGNs with one or more of the following indications of possible obscuration along the line of sight (either intervening or intrinsic) (i) optically weak or blank field, (ii) indication of reddening, (iii) gravitationally lensed, (iv) suppressed soft X-ray flux, (v) observed galaxy along the line of sight.

The observations are self-calibrated using the background continuum source. The pointing accuracy needs to be than 5".

*************************************************************************

Effect of Re-Baseline: Going from 64 to 50 antennas

Again, this science is not fundamentally disabled by decrease in number of antennas. Just the integration times will have to be increased by a factor 1.64, or they could decrease the number of sources from 60 to 37. Again, since this is a line survey (lots of short integrations at different frequencies and/or different sources), systematics and/or dynamic range limits for long integrations are not an issue.

**********************************************************************

1.6.1: Name -- High resolution imaging of radio hot spots Authors: C. Carilli

2. Science goal: We will perform high resolution imaging at 100, 220, and 650 GHz of the radio hot spots, and jets, of the archtype powerful radio galaxies Cygnus A and Pictor A. These data, combined with VLA images at 8, 22, and 43 GHz, will provide the definitive test of particle acceleration and loss mechanisms in the hot spots (=terminal jet shocks) of powerful radio galaxies. The required sensitivities and dynamic ranges are extrapolated from existing 43 GHz images based on reasonable physical models for first order Fermi acceleration, and synchrotron radiative losses, at terminal jet shocks (Carilli et al. 1999, AJ 118, 2581; Perley et al. 1997, A&A, 328, 12). In particular, the 650 GHz imaging is in the critical range where an exponential cut-off is expected due to radiative losses during the finite shock crossing time of the electrons. These observations will delineate in detail the regions of most active particle acceleration, and can be used to determine hot spot magnetic field strengths and relativistic particle energy densities, independent of minimum energy assumptions. Observations of the inner jets will constrain particle acceleration processes along the jet, thought to occur in oblique (weak) shocks within the jets. Resolution must be matched to that of the VLA observations = 0.2".

3. Number of sources: 2

4. Coordinates:

4.1. 1957+4035, 0518-4548

4.2. Moving target: no

4.3. Time critical: no

5. Spatial scales:

5.1. Angular resolution: 0.2"

5.2. Range of spatial scales/FOV: 0.2" to 8"

5.3. Single dish: no

5.4. ACA: no

5.5. Subarrays: no

6. Frequencies:

6.1. Receiver band: Band 3 -- 100 GHz in Configuration A Band 6 -- 220 GHz in Configuration B/C Band 9 -- 650 GHz in Configuration D

6.2. Lines and Frequencies

6.3. Spectral Resolution (km/s)

6.4. Bandwidth or spectral coverage: standard continuum

7. Continuum flux density:

7.1. Typical value: >= 1 mJy/beam at 100 GHz >= 0.5 mJy/beam at 250 GHz >= 0.1 mJy/beam at 650 GHz

7.2. Continuum peak value: Hot spots: 45 mJy/bm at 100 GHz
            1. mJy/beam at 250 GHz
            2. mJy/beam at 650 GHz
    Cores
    0.5 to 1 Jy

7.3. Required continuum rms:
            1. 01 mJy/bm at 100 GHz
            2. 02 mJy/beam at 250 GHz
            3. 06 mJy/beam at 650 GHz

7.4. Dynamic range in image: 5000

8. Line intensity:

8.1. Typical value:

8.2. Required rms per channel:

8.3. Spectral dynamic range:

9. Polarization: yes

10. Integration time per setting: due to small PB, each track will cycle through 3 pointing positions = 2 hot spots + core. 1 track (+/- 2hr) at 100 x 2 sources 1 track (+/- 2hr) at 250 x 2 sources 2 track (+/- 2hr) at 650 x 2 sources

11. Total integration time for program: 32 hr

********************************************************************

Effect of Re-Baseline: Going from 64 to 50 antennas

These are likely dynamic range limited observations, and hence are not affected by the decreased collecting area. However, they could be disabled if we find that the dynamic range limitations are significantly reduced (ie. below 5e3) due to the worsened uv coverage.

**********************************************************************

1.6.2: Name -- High resolution imaging of X-ray hot spots in radio jets Authors: C. Carilli

2. Science goal: We will perform high resolution imaging at 100 and 350 GHz of the X-ray detected hot spots in the jets of the archtype jet sources M87 and 3C273. X-ray detected jet knots provide the most severe constraints on particle acceleration and emission mechanisms within radio jets, with radiative lifetimes that can be measured in years. The spectral properties of these hot spots are well constrained at cm, and optical to Xray wavelengths. The proposed observations will provide the key link between the cm and optical/Xray regime, and hence provide critical constraints on emission mechanisms (eg. synchrotron or inverse compton) for the Xrays, as well as constraints on particle acceleration mechanisms in the jets (see review by Harris 2003, astroph 0302097). Resolution must be matched to that of the Chandra and the VLA observations (0.5").

3. Number of sources: 2

4. Coordinates:

4.1. 1229+0203, 1230+1223

4.2. Moving target: no

4.3. Time critical: no

5. Spatial scales:

5.1. Angular resolution: 0.2"

5.2. Range of spatial scales/FOV: 0.5" to 15"

5.3. Single dish: no

5.4. ACA: no

5.5. Subarrays: no

6. Frequencies:

6.1. Receiver band: Band 3 -- 100 GHz in Configuration B Band 7 -- 350 GHz in Configuration D

6.2. Lines and Frequencies

6.3. Spectral Resolution (km/s)

6.4. Bandwidth or spectral coverage: standard continuum

7. Continuum flux density:

7.1. Typical value:

7.2. Continuum peak value:
Cores
5 to 10 Jy

7.3. Required continuum rms:
            1. mJy/bm at 100 GHz
            2. mJy/bm at 350 GHz

7.4. Dynamic range in image: 10000

8. Line intensity:

8.1. Typical value:

8.2. Required rms per channel:

8.3. Spectral dynamic range:

9. Polarization: yes

10. Integration time per setting: 1 track (+/- 2hr) at 100 x 2 sources 1 track (+/- 2hr) at 350 x 2 sources

11. Total integration time for program: 16 hr

********************************************************************

Effect of Re-Baseline: Going from 64 to 50 antennas

As above, these are likely dynamic range limited observations, and hence are not affected by the decreased collecting area. However, they could be disabled if we find that the dynamic range limitations are significantly reduced due to the worsened uv coverage. The dynamic range limitations in this case are even more stringent, and we need to do at least 1e4, or better in some sources.

**********************************************************************

1.6.3: Name -- The general relativistic shadow of Sgr A* Authors: C. Carilli

2. Science goal: We propose VLBI imaging at 220 GHz of Sgr A* using the 'Pacific array' (see note below). These observations will allow for reasonable imaging at 20 uas resolution, well matched to the scale of the expected general relativistic shadow of the SMBH in Sgr A* (Falcke et al.2000 528, L13). These observations will provide the final evidence for the existence of a SMBH at the Galactic center, provide a fundamental test of strong field GR, and are the most direct method for separating a Kerr (ie. spinning) from a Schwarzschild black hole. At a minimum, the sensitivity per baseline is adequate to perform model fitting on relatively short timescales (minutes), while the array itself has enough antennas to provide both closure amplitude and phases, and hence should be adequate for hybrid imaging of the GR shadow of Sgr A*. The existence of reasonable mm-VLBI calibrators (eg NRAO 530) in the vicinity of Sgr A* will allow for phase-referenced fringe fitting, although the source itself is strong enough, and the UV coverage dense enough, to allow for hybrid mapping as well. The source Sgr A* has been detected at 220 GHz on the PdBI -- Pico Veleta baseline (resolution = 300 uas) with a flux density of 2.0 Jy, and an upper limit to the size of order 100 uas (Krichbaum et al. 1998 335, L106). The proposed observations will have more than an order of magnitude better resolution, more than two orders of magnitude better sensitivity, and, again, enough antennas to perform proper imaging of Sgr A*.

3. Number of sources: 1

4. Coordinates:

4.1. 1742-2859

4.2. Moving target: no

4.3. Time critical: no

5. Spatial scales:

5.1. Angular resolution: 20uas

5.2. Range of spatial scales/FOV: 20 uas -- 100 uas

5.3. Single dish: no

5.4. ACA: no

5.5. Subarrays: no

6. Frequencies:

6.1. Receiver band: Band 6 -- 220 GHz in Configuration D or E, phased array

6.2. Lines and Frequencies

6.3. Spectral Resolution (km/s)

6.4. Bandwidth or spectral coverage: 1 GHz x 2pol (set by VLBI recorder)

7. Continuum flux density:

7.1. Typical value:

7.2. Continuum peak value: <= 2 Jy

7.3. Required continuum rms: ALMA - HHT baseline, 10 min rms = 0.7 mJy ALMA - LMT baseline, 10 min rms = 0.2 mJy

7.4. Dynamic range in image: 1e3

8. Line intensity:

8.1. Typical value:

8.2. Required rms per channel:

8.3. Spectral dynamic range:

9. Polarization: yes

10. Integration time per setting: 4 tracks of 4hrs each

11. Total integration time for program: 16 hr

Notes: The pacific array at 220 GHz consists of: ALMA, HHT, LMT, CARMA, and any of CSO/JCMT/SMA. We estimate mutual visibility of Sgr A* of about 4hrs. Note that an Atlantic array might also be considered, including PdBI, IRAM 30m.

**************************************************************************

Effect of Re-Baseline: Going from 64 to 50 antennas

The key to these observations will be to be able to perform calibration transfer and then hybrid imaging on-source, on fairly short timescales. ALMA provides the most sensitive element (by far) in the Pacific array, and hence anchors the whole project, enabling adequate (self-) calibration on short timescales. Decreasing the collecting area clearly impacts this, ie. by decreasing the minimum timescale for self calibration solutions by a factor 1.64. On these short timescales, the phase errors increase roughly linearly (powerlaw index=5/6) with calibration timescale, so a factor 1.64 could be alot in terms of residual rms phase noise. Is this completely debilitating? Unclear until we try, but it certainly doesn't help.

**********************************************************************

1.6.4: Name -- mm VLBI observations of core-jets Authors: C. Carilli

2. Science goal: We propose VLBI imaging using the Pacific array (see 1.6.3) at 220 GHz of a representative sample of radio jets in low redshift radio galaxies. These data will probe to scales of 20uas, corresponding to 50 Schwarzschild radii at the distance of M87 (17 Mpc). Observations of M87 suggest that these scales correspond to the fundamental regime where initial jet collimation occurs (Junor et al. 1999 Nature 401, 891). Hence these observations will provide a key test of jet formation models in radio galaxies.

3. Number of sources: 10

4. Coordinates:

4.1. Choose equatorial sources: Declination = 0 +/- 10deg

4.2. Moving target: no

4.3. Time critical: no

5. Spatial scales:

5.1. Angular resolution: 20uas

5.2. Range of spatial scales/FOV: 20 uas -- 200 uas

5.3. Single dish: no

5.4. ACA: no

5.5. Subarrays: no

6. Frequencies:

6.1. Receiver band: Band 6 -- 220 GHz in Configuration D or E, phased-array

6.2. Lines and Frequencies

6.3. Spectral Resolution (km/s)

6.4. Bandwidth or spectral coverage: 1 GHz x 2pol (set by VLBI recorder)

7. Continuum flux density:

7.1. Typical value:

7.2. Continuum peak value: typically of order 1 Jy

7.3. Required continuum rms: ALMA - HHT baseline, 10 min rms = 0.7 mJy ALMA - LMT baseline, 10 min rms = 0.2 mJy

7.4. Dynamic range in image: 1e3

8. Line intensity:

8.1. Typical value:

8.2. Required rms per channel:

8.3. Spectral dynamic range:

9. Polarization: yes

10. Integration time per setting: 10 sources at 5 hrs per source

11. Total integration time for program: 50 hr

*********************************************************************

Effect of Re-Baseline: Going from 64 to 50 antennas

These are likely dynamic range limited observations, and hence are not affected by the decreased collecting area. However, they could be disabled if we find that the dynamic range limitations are significantly reduced due to the worsened uv coverage. The dynamic range limitations in this case are about a few thousand.

**********************************************************************

1.6.5: Name -- Imaging the molecular gas in high redshift FIR-luminous QSOs Authors: C. Carilli

2. Science goal: We propose high resolution (0.2") imaging of the CO emission from high redshift (z=4 to 6.4) QSOs. Studies of high redshift QSOs have shown that about 30% of the sources are luminous FIR sources, corresponding to thermal emission from warm dust, with dust masses >= 1e8 M_sun (eg. Omont et al. 2003, A&A 398, 857; Carilli et al. 2002 ApJ 555, 625). In all cases studied with adequate sensitivity (and redshift accuracy), CO emission has also been detected, with typical line peak flux densities for the 5-4 transition (redshifted to band 3 of ALMA) >= 2 mJy. Various lines of argument suggest that the dominant dust heating mechanism is star formation, implying star formation rates of order 1e3 M_sun/year, although the AGN could also contribute to the dust heating. The coexistence of massive starbursts and major accretion events onto supermassive black holes, is consistent with the idea of coeval SMBH-galaxy formation at high redshift, as suggested by the close correlation between black hole mass and bulge mass seen in nearby spheroidal galaxies. Imaging the CO emission provides the only means of determining the dynamical mass of the host galaxy, and also provides information on the nature and physical conditions of the earliest galaxies. In particular, determining the distribution of the molecular gas and dust relative to the AGN could help to constrain the dust heating mechanism, as well as reveal complex/multiple sources, as might be expected in for hierarchical structure formation.

We will observe a representative sample of 5 sources using band 3 in A configuration (0.17" resolution). The typical sizes inferred for the CO emitting regions are between 0.2 and 2". Assuming a characteristic size of order 1" implies a typical expected surface brightness of about 0.1 mJy/beam for a 50 km/s channel.

3. Number of sources: 5

4. Coordinates:

4.1. Choose equatorial sources from SDSS/DPSS, selected as FIR-luminous QSOs from single-dish bolometer surveys (eg. next generation MAMBO/SCUBA), and detected in CO emission using LMT or GBT (or small configuration ALMA survey).

4.2. Moving target: no

4.3. Time critical: no

5. Spatial scales:

5.1. Angular resolution: 0.17"

5.2. Range of spatial scales/FOV: 0.17" to 4"

5.3. Single dish: no

5.4. ACA: no

5.5. Subarrays: no

6. Frequencies:

6.1. Receiver band: Band 3 -- 100 GHz in Configuration A

6.2. Lines and Frequencies

6.3. Spectral Resolution (km/s) 50 km/s

6.4. Bandwidth or spectral coverage: 8 GHz (for continuum sensitivity) with 512 spectral channels/polarization

7. Continuum flux density:

7.1. Typical value: 1 mJy

7.2. Continuum peak value:

7.3. Required continuum rms: 0.002 mJy/beam

7.4. Dynamic range in image:

8. Line intensity:

8.1. Typical value: 0.1 mJy/beam/channel

8.2. Required rms per channel: 0.035 mJy/beam/channel

8.3. Spectral dynamic range:

9. Polarization: no

10. Integration time per setting: 5 sources at 2x6 hrs per source

11. Total integration time for program: 60 hr

Notes: could be included in 1.1 or 1.5. A parallel program could be to search for CO emission from high z QSOs, but this could also be done with LMT/GBT. The unique aspect of ALMA is the high resolution imaging. For some sources it might be possible to do multiple transitions (eg. 5-4 and 6-5) within band 3 simultaneously, thereby allowing for study of excitation gradients.

**********************************************************************

Effect of Re-Baseline: Going from 64 to 50 antennas

This science is not fundamentally disabled by decrease in number of antennas. Just the integration times will have to be increased by a factor 1.64 (note we are already down to 5 sources, so decreasing number of sources is not an option). Also, the integration time per source would be 20hrs, and could raise concerns about systematics for long integrations when searching for faint broad lines.

**********************************************************************

1.6.6: Name -- mm VLBI imaging of IDVs Authors: C. Carilli

2. Science goal: We propose VLBI imaging using the Pacific array (see 1.6.3) at 220 GHz of a representative sample of IDVs (Intra-Day Variability). These data will probe to scales of 20uas, and test models for coherent emission mechanisms to explain the very high brightness temperatures inferred from the ISS (Maquart et al. 2000 ApJ 528, 623), thereby constraining physical conditions in the jet, and perhaps study aspects of the accretion disk via the induced Compton scattering mechanism(?).

3. Number of sources: 5

4. Coordinates:

4.1. Any

4.2. Moving target: no

4.3. Time critical: no

5. Spatial scales:

5.1. Angular resolution: 20uas

5.2. Range of spatial scales/FOV: 20 uas -- 200 uas

5.3. Single dish: no

5.4. ACA: no

5.5. Subarrays: no

6. Frequencies:

6.1. Receiver band: Band 6 -- 220 GHz in Configuration D or E, phased-array

6.2. Lines and Frequencies

6.3. Spectral Resolution (km/s)

6.4. Bandwidth or spectral coverage: 1 GHz x 2pol (set by VLBI recorder)

7. Continuum flux density:

7.1. Typical value:

7.2. Continuum peak value: <= 2 Jy

7.3. Required continuum rms: ALMA - HHT baseline, 10 min rms = 0.7 mJy ALMA - LMT baseline, 10 min rms = 0.2 mJy

7.4. Dynamic range in image: 1e3

8. Line intensity:

8.1. Typical value:

8.2. Required rms per channel:

8.3. Spectral dynamic range:

9. Polarization: yes

10. Integration time per setting: 5 sources at 5 hrs per source

11. Total integration time for program: 50 hr

****************************************************************

Effect of Re-Baseline: Going from 64 to 50 antennas

Integration times will have to be increased. A potential problem is that if we are trying to coordinate the VLBI imaging with the luminosity state of the IDV, then we do not have the luxury of adjusting the integration time.

**********************************************************************

1.6.7: Name -- Search for flat spectrum mm-loud AGN Authors: C. Carilli

2. Science goal: We will search for flat spectrum, mm-loud AGN. The search can be piggy-backed on the standard pre-observation calibrator searches using band 3 during normal observations. A follow-up snapshot survey (1 min/source) will then be done at 220 GHz of 1000 candidate sources, and at 22 GHz with VLA, to determine the cm to (sub)mm spectra of the sources. The search could reveal new population of faint blazars, IDVs, HFPs, and other types of known sources at more than 10 times deeper levels that is currently possible (and at higher frequencies; Corray et al. 1998 AJ 115, 1388; Dellacasa et al. 2001, A&A Supp), as well as possibly reveal new classes of sources, such as very young radio jets. These can then be studied further at X- and Gamma-rays, as well as using mm-VLBI, and standard monitoring programs.

3. Number of sources: 1000

4. Coordinates:

4.1. Any

4.2. Moving target: no

4.3. Time critical: no

5. Spatial scales:

5.1. Angular resolution: any (small configuration preferred at 220 GHz)

5.2. Range of spatial scales/FOV: any

5.3. Single dish: no

5.4. ACA: no

5.5. Subarrays: no

6. Frequencies:

6.1. Receiver band: Band 3 -- piggy-back on standard calibrator pre-observation search program Band 6 -- 220 GHz follow-up

6.2. Lines and Frequencies

6.3. Spectral Resolution (km/s)

6.4. Bandwidth or spectral coverage: full

7. Continuum flux density:

7.1. Typical value: 10 mJy

7.2. Continuum peak value:

7.3. Required continuum rms: 100 GHz -- standard sensitivity for calibrator search 220 GHz -- 0.1 mJy

7.4. Dynamic range in image: 1e3

8. Line intensity:

8.1. Typical value:

8.2. Required rms per channel:

8.3. Spectral dynamic range:

9. Polarization: yes

10. Integration time per setting: 1000 sources at 1min/source at 220 GHz

11. Total integration time for program: 20 hr

*********************************************************************** Effect of Re-Baseline: Going from 64 to 50 antennas

This science is not fundamentally disabled by decrease in number of antennas. Just the integration times will have to be increased by a factor 1.64, or we could decrease the number of sources by this factor.

**********************************************************************

'> Previously, I reviewed much of the Galaxies and Cosmology, in particular
'> the high z stuff. I'd be happy to go over these in context
'> of descope 1.1 to 1.6.
'> perhaps Dr. Blain would assist?
'>
'> in terms of decreasing number of antennas, a key point will be
'> calibration -- what are fast switching timescales and slew distances
'> that will be required given the lower instantaneous sensitivity?
'>
'> cc
'>

Fast Switching was originally concieved of with the MMA, 40 8m antennas. It basically worked. Going to 64 12m antennas actually didn't improve fast switching's efficiency by a great deal --

consider these numbers (derived from 64 x 8m antennas):

@ 345 GHz (with appropriate conditions given dynamic scheduling -- not the best, not the worst):

... for the "median" calibrator source, the time required to sufficiantly detect that calibrator at 90 GHz is 0.28 s; that calibrator is 80 mJy, and is located 1.4 deg away. The time required to MOVE (roundtrip) is about 3 s. SO, the phase errors we make and the efficiency that is lost due to cal time is dominated by the MOVE time.

(If we don't calibrate at 90 GHz, but 345 GHz, a simpler observing strategy, we need slightly more time on a more distant and somewhat fainter calibrator: 60 mJy, 2.2 deg away, 2x slew time is 3.7 s, and the integration time is 0.54 s -- we are still dominated by the move time.)

My interpretation: we have a LOT OF SLACK in the system -- we can live with a) the sky not having quite as many calibrators as the model suggests, or b) ALMA not being as sensitive as we hoped, or even c) not having as many antennas as we wanted, and the end result will be nearly as good as the 64x12 result. ie, I estimate the change in overall eficiency will be less than 1% -- going from 85% efficient, say, to 84.6% (these numbers are pure guesses).

ONLY if we are observing at 650 or 850 GHz and we are not calibrating at 90 GHz, but at the observing frequency, does the calibrator integration time become comparable to the slewing time to and from the calibrator. IN THIS SITUATION, reduction in antenna number will result in a modest increase in the integration time on the calibrator, which will be felt modestly in the final fast switching efficiency (perhaps 1%, perhaps more). HOWEVER, this is a really spongy mathematical system with many degrees of freedom (OK, we'll go just a little further out to find just a little bit brighter source and we'll integrate just a little bit longer, and we'll trade off that slight decrease in decorrelation efficiency by increasing the cycle time just a bit to increase the time efficiency.... you get the picture -- there are many dimensions to compensate when one of the assumptions sours a bit).

When we went to 64 x 12m antennas, fast switching did not drastically improve over 40 x 8m. Therefore, going to 50 x 12m won't drastically decrease our phase calibration ability.

My 2 cents: these calculations WILL be performed again, sooner or later; I actually had an error in the source counts code, which UNDERESTIMATED the number of sources; there will be other reasons to redo the calc. When enough reasons pile up, we'll redo the calcs using 50 x 12m and the other "improvements in our modelling of reality". Is now that time? I say no, what do you say?

-Mark

-- AlWootten - 21 Feb 2005
Topic revision: r1 - 2005-02-21, AlWootten
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