REU Observing Project 2009

TIP Last Update: JeffMangum - 25 June 2009

The CV+GB Summer Student observing time has been scheduled as follows:
  • 2009/07/05: 13:00 - 22:00 EDT (06:00 - 15:00 LST)
  • 2009/07/06: 03:30 - 07:00 EDT (20:30 - 00:00 LST)
  • 2009/07/06: 17:30 - 22:30 EDT (10:30 - 15:30 LST)

See the GBT Schedules Page for detailed scheduling information for the GBT.

ALERT! NOTE: The GBT Observing Project is coupled to the CV Summer Student Trip to GB. ALERT!


GBT Observing Resources

Use the following links to find information on how to observe with the GBT (and thus set up the observations for your projects below):


Sample Astrid Configuration Files


Projects

Extragalactic HI

  • Project Number: 09A-094
  • Scheduled: 2009/07/05 13:00-22:00 EDT
  • Project Leaders: Michael Lam, Brian Roper

Submitted by JimBraatz. This experiment is to measure Neutral Hydrogen (HI) profiles for a variety of galaxies in the nearby universe. Neutral Hydrogen is the "bread and butter" of radio astronomy. Using HI measurements, one can:
  1. measure the total hydrogen mass of the galaxy,
  2. measure the redshift and distance to the galaxy,
  3. get a measure of the rotation speed of the galaxy,
  4. determine whether the gas in the galaxy is symmetrically distributed, and
  5. more!

The details of the experiment can be designed by the students. Some ideas might be:
  • Select a representative sample of galaxies with various Hubble types and compare the hydrogen content of those galaxies. (i.e. Do SA galaxies have more HI than SB of comparable luminosity? How about E galaxies?)
  • Measure the redshift of a sample of galaxies using the HI line, and compare to optical redshifts. Is there a difference? Which is more accurate? Does it matter if the galaxy is an AGN?
  • Select a sample of galaxies with a range of inclinations. How does the profile change with inclination, and why?
  • How does the HI profile compare between isolated large disk galaxies, and interacting large disk galaxies?

    There are many possibilities. The students will have an opportunity to measure and compare basic galaxy properties. The observing modes and data processing techniques are thoroughly tested and well defined, and are also standard and instructive to understanding basic position-switched spectroscopy.

Resources:
  • The HI 21cm Line: A summary of how one can calculate HI column density from measurements of the HI 21cm line.
  • NED: NASA Extragalactic Database
  • T_REx.init: HI receiver and backend setup file
  • T_REx.astrid: HI observing script

  • SOURCES: (TBD)
  • LST RANGE: Any yielding a total of 5 hours of telescope time

ToDo Before the Extragalactic HI Observing Run

  1. Source positions (RA,Dec).
  2. Receiver and correlator configuration required.
  3. Antenna switching mode to be used.
  4. Determine what signal-to-noise you want to ultimately derive from your measurements and estimate what combination of integration time and bandwidth you will need given an assumed system temperature. HINT: Use the "radiometer equation".
  5. More...


Formaldehyde (H2CO) Emission Studies of Protostars

  • Project Number: 09A-094
  • Scheduled: 2009/07/05 20:00 - 22:30 EDT
  • Project Leaders:

Submitted by JeffMangum. Formaldehyde, H2CO, is a ubiquitous molecule in space as on Earth. Its structure provides a moderate dipole moment which in turn makes it a useful probe of moderately to highly dense regions. It also possesses lines at fairly low frequency, accessible with the GBT. Lines at 6 cm and 2 cm wavelength may be compared and used to estimate density, for example. However, owing again to the structure of the molecule and the specifics of interstellar conditions, the line is normally detected in absorption against the cosmic background radiation.

There are fewer than half a dozen places in the Universe where the line has been detected in emission:
  • Wadiak et al. (1985) found one region of emission in Ophiuchus. Wadiak et al. (1985) mapped this line in the other region in Ophiuchus where it occurs in emission, the B1 core, and found two rotating elongated structures, which may represent evolutionary phases of a cloud core as it creates and nurtures the young stars.
  • Another emission region is in Orion A-BN/KL. This line was mapped in continuum mode in the VLA-D configuration by Barvainis and Wootten (1986), who sought to place limits upon the polarization in the line. Weak emission at 2 cm is known to extend over a wide range in the OMC1 cloud (Bastien et al. 1985, map from Effelsberg antenna). Johnston, Wadiak, Rood and Wilson have mapped the formaldehyde distribution in the region 3' north of the dense core. The emission in the Effelsberg map is quite intense, with main beam brightness temperatures ranging from 0.2 K at the compact southern extreme of the map to 2K at BN/KL.

The L1689 protostellar core region has formed at least one star, and provides for us an opportunity to glimpse the next stage in the star formation process. If a disk is present, or a star of a solar mass or so, the gravitational velocity perturbations within 10" of the object should be as large as 1 km/s, easily detectable. If rotation is present, a dynamical mass estimate, which includes the central object, can be derived. The gas mass, from the line intensity, may be used to measure the gas in the rotating structure. In the mid-1980s, Mangum and Wootten used the 140ft telescope to discover 2cm H2CO emission near a dense portion of the Ophiuchus star-forming region. However, the large beam and low antenna efficiency of that telescope, coupled with the weakness of the emission conspired to prevent those estimable authors from figuring out exactly what the relation of the emission region was to any dense material and star formation in the vicinity.

The REU Mission: Using the better sensitivity and smaller beam of the GBT, discover the true location and extent of this rare region of 2 cm Formaldehyde emission and how it relates to star formation in the region.

Resources:

ToDo Before the Protostar Observing Run

  1. Source list positions (RA,Dec).
  2. Receiver and correlator setup to use.
  3. Determine what signal-to-noise you want to ultimately derive from your measurements and estimate what combination of integration time and spectral resolution you will need given an assumed system temperature. HINT: Use the "radiometer equation".
  4. Which flavour of "switching" are you going to use? HINT: You want to choose an observing mode that is both efficient and allows you to make the measurements the way you want (i.e. lets you obtain the spectral resolution and bandwidth you desire).
  5. Are you going to want to map the source? You will need to map a source if it is larger than the primary beam of the antenna at your observing frequency. Look at the data from last year and decide if you need to map the source, and if so which positions need to be measured.


Radio Recombination Line Emission in NGC7027 and DR 21

  • Project Number: 09A-094
  • Scheduled: 2009/07/06 03:30-07:00 EDT
  • Project Leaders:

Submitted by ToneyMinter. With this experiment you will measure the radio recombination line emission toward NGC7027 and DR 21. Radio recombination lines from hydrogen, helium and carbon are routinely observed. It should also be possible to see radio recombination lines from other elements such as sulfer, oxygen and nitrogen. These however have not been unambigously observed in an HII region before. With the sensitivity of the GBT and the high spectral resolution of the spectrometer, it may be possible to observe and resolve the radio recombination lines from these elements. Lines at L, S, C and X-band can be sampled for these observations. It will be a good exercise for the students to figure out the trade-offs of better velocity resolution at lower frequencies vs RFI and sensitivity, etc.

Comparing the line-widths of the observed radio recombination lines as the mass of the atoms change will allow the thermal and non-thermal (turbulent) components to be determined with high precision. It may also be possible to determine if pressure broadening of the lines is present. The thermal contribution of the line-width can then be converted into a temperature that can be compared to values determined from optical and radio continuum observations.

Resources:
  • The HI 21cm Line: A summary of how one can calculate HI column density from measurements of the HI 21cm line.
  • recomb.init: Recomb project receiver and backend setup file.
  • recomb.astrid: Recomb project observing script.

  • SOURCES: NGC 7027 and DR 21
  • LST RANGE: approximately 14 - 2 hours

ToDo Before the NGC7027 Observing Run

  1. Source positions (RA,Dec).
  2. Receiver and correlator configuration required.
  3. Antenna switching mode to be used.
  4. Determine what signal-to-noise you want to ultimately derive from your measurements and estimate what combination of integration time and bandwidth you will need given an assumed system temperature. HINT: Use the "radiometer equation".
  5. More...


OH Emission in a Comet

  • Project Number: 09A-094
  • Scheduled: 2009/07/05 13:00-22:00 EDT and 2009/07/06 17:30-22:30 EDT
  • Project Leaders: Missy Louie, Patrick McCauley

Submitted by AmyLovell. With this experiment you will measure the OH emission from two comets
  • C/2007 Q3 Siding Spring
    • On July 5, it will be 08h04m21s and dec -2d48m11s
    • By July 8 it will be up to 8h09m45s and -2d18m28s
    • If it is really 12th magnitude visually, its OH absorption intensity will be about 4.5 to 5 mJy
  • 88P/Howell
    • On July 7 it will be at 12h45m47s and -04d06m, moving less quickly than C/2007 Q3 Siding Spring
    • Should be something like 2-3 mJy, also in absorption

Both comets are pretty far from the Sun and Earth (detecting Siding Spring at 3 AU might be an NRAO record, or at least the most distant since Hale-BoppÂ…), so staring at the nucleus is the best practice, mapping will probably not yield anything.

Comets contain significant amount of water ice. The sun heats this water ice and it escapes from the comet as water vapor - forming the coma and tail of the comet with which we are so familiar. The radiation from the Sun then disassociates the water (H20) into a hydrogen (H) atom and a hydroxl molecule (OH). Radio emission from water vapor in a comets nucleus is difficult to measure. However, the radio emission from the hydroxyl molecule is easier to detect. By observing the amount of OH present, the rate at which the comet is loosing water can be determined.

Resources:
  • ohconfig.py.txt: OH observations receiver and spectrometer setup script
  • bor26ON.py.txt: Example (for Comet Borrelly) observing script
  • Ephemeris files for each comet are in /users/alovell/summer09 and are called:
    • howell_jul5
    • howell_jul67
    • 07q3jul5
    • 07q3jul67

  • SOURCES: C/2007 Q3 Siding Spring (08:09:45,-02:18:28 on 2008/07/05) and 88P/Howell (12:45:47, -04:06)
  • LST RANGE: (How much integration time needed?)

ToDo Before the Comet Observing Run

  1. Source positions (RA,Dec).
  2. Receiver and correlator configuration required.
  3. Antenna switching mode to be used.
  4. Determine what signal-to-noise you want to ultimately derive from your measurements and estimate what combination of integration time and bandwidth you will need given an assumed system temperature. HINT: Use the "radiometer equation".
  5. More...


-- JeffMangum - 2009-05-05
Topic revision: r8 - 2009-06-30, JeffMangum
This site is powered by FoswikiCopyright © by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding NRAO Public Wiki? Send feedback