Title  Excitation Conditions of Nuclear GMCs
Pi     E. Schinnerer
Time   75 hrs

1. Name of program and authors
1.5.5: Name -- Excitation Conditions of Nuclear GMCs
       Authors: E. Schinnerer, D.S. Meier


2. Science goals:

   Massive star formation as well as the presence of an active
   galactic nucleus (AGN) can impact the excitation conditions for CO
   line emission from the centers of galaxies. Therefore the derived
   molecular gas mass can be vastly overestimated, thus leading to
   wrong estimates about the star formation efficiency and the amount
   of gas available for future star formation events. Using multiple
   12co transitions (1-0, 2-1, 3-2, 4-3, 6-5) allows the direct
   measurement of the temperature and density of individual molecular
   cloud complexes as well as the more extended diffuse gas via Large
   Velocity Gradient (LVG) analysis. The comparison of properties
   between the GMCs and the diffuse gas will provide important insight
   into the life cycle of molecular gas in the centers of
   galaxies. The high angular resolution is essential to resolve the
   gas into individual GMCs (avoiding blending) as well as for the
   separation of the diffuse component from the GMCs. Finally this
   dataset will provide local gas excitation templates for high z
   galaxies, where it is these high excitation lines that lay within
   the ALMA bands

3. Number of sources: 5

4. Coordinates:

4.1. all over sky, in 5 - 20 Mpc distance

4.2. Moving target: no 

4.3. Time critical: no 


5. Spatial scales:

5.1. Angular resolution (arcsec): 0.2"

5.2. Range of spatial scales/FOV (arcsec): 0.2" - 20"

     single-field, small mosaic (at higher frequencies)

5.3. Required pointing accuracy: ` 0.5" (for pointing at high frequencies)


6. Observational setup

6.1. Single dish total power data: required

     Observing modes for single dish total power: 

     frequency switch; position switch;
     on-the-fly mapping;

6.2. Stand-alone ACA: required

6.3. Cross-correlation of 7m ACA and 12m baseline-ALMA antennas: 
     required

6.4. Subarrays of 12m baseline-ALMA antennas: no


7. Frequencies:

7.1. Receiver band: Band 3, 6, 7, 8, 9

7.2. Lines and Frequencies (GHz): 

     CO(1-0), CO(2-1), CO(3-2), CO(4-3), CO(6-5)

7.3. Spectral resolution (km/s): 5 km/s

7.4. Bandwidth or spectral coverage (km/s or GHz): ~ 1200 km/s


8. Continuum flux density:

8.1. Typical value (Jy):

8.2. Required continuum rms (Jy or K):

8.3. Dynamic range within image:

8.4. Calibration requirements: absolute      ( 1-3% / 5% / 10% / n/a )
                               repeatability ( 1-3% / 5% / 10% / n/a )
                               relative      ( 1-3% / 5% / 10% / n/a )


9. Line intensity:

9.1. Typical value (K or Jy): 10 mJy at 115 GHz (~ 300 mJy at 691 GHz)

9.2. Required rms per channel (K or Jy): 0.5 mJy at 115 GHz (6 mJy at 691 GHz)

9.3. Spectral dynamic range: 5 - 100

9.4. Calibration requirements: absolute      ( 1-3% )
                               repeatability ( 1-3% )
                               relative      ( 1-3% )


10. Polarization: no 


11. Integration time for each observing mode/receiver setting (hr):
    30min - 1hr per band per configuration per source

12. Total integration time for program (hr): 75 hr


13. Comments on observing strategy : 

    short spacing information is crucial to derive accurate line ratios
    
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Comments:

I don't understand why this project needs the 7m x 12m cross
correlations, but not standalone ACA. I would naively think that the
ACA beaselines (+ total power) would deal quite well with the shorter
spacings, while the few extra baselines we get by recording the 7m x
12m correlations would not increase the sensitivity by very large
amounts.

R.: It was my understanding that baselines between 7m antennas would be 
    included as well. I have added the requirement for ACA stand-along
    observations. I agree that the best sampling possible of the uv 
    plane is critical for this project.