Title  Structure of the ISM in irregular galaxies
Pi     C. Wilson
Time   180 hrs

1. Name: Structure of the ISM in irregular galaxies
	C. Wilson et al. 

2. One short paragraph with science goal(s)

The structure of the ISM in low metallicity dwarf galaxies. Are the
molecular clouds smaller as well as less luminous in CO? Do they have
small CO cores surrounded by larger H2 envelopes? Are the physical
properties (density, temperature) very different
from gas at solar metallicities? What is the dust to gas ratio at lower
metallicities? What effect does the presence of a starburst have on the
ISM structure at low metallicity?  Besides understanding nearby dwarf
galaxies, the answers to these questions could be important for
interpreting ALMA observations of high-redshift galaxies with reduced
metallicities. 


3. Number of sources 

   10, about half starburst and half non-starburst

4. Coordinates:

4.1. all over the sky (probably)

4.2. Moving target: no

4.3. Time critical: no 

CO J=1-0 imaging:
----------------

5. Spatial scales:

5.1. Angular resolution (arcsec): 0.4"  (20 pc at 10 Mpc)

5.2. Range of spatial scales/FOV (arcsec): single field (55")

5.3. Required pointing accuracy: 1"


6. Observational setup

6.1. Single dish total power data: required

     Observing modes for single dish total power: nutator or OTF

6.2. Stand-alone ACA: required

6.3. Cross-correlation of 7m ACA and 12m baseline-ALMA antennas: 
     no

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


7. Frequencies:

7.1. Receiver band: Band 3

7.2. Lines and Frequencies (GHz):
		CO 115.0 GHz (redshifted for 10 Mpc and Ho = 75)

7.3. Spectral resolution (km/s): 2 km/s

7.4. Bandwidth or spectral coverage (km/s or GHz): 300 km/s max


9. Line intensity:

9.1. Typical value (K or Jy): 1-4  K 

9.2. Required rms per channel (K or Jy): 0.25 K

9.3. Spectral dynamic range: 20

9.4. Calibration requirements: absolute      10%
                               repeatability 3%
                               relative      3%

10. Polarization:  no

11. Integration time for each observing mode/receiver setting (hr): 
		7.3 hr per galaxy

CO 3-2 imaging:
---------------

5. Spatial scales:

5.1. Angular resolution (arcsec): 1"

5.2. Range of spatial scales/FOV (arcsec): medium mosaic (19 fields)

5.3. Required pointing accuracy: 1"


6. Observational setup

6.1. Single dish total power data: required

     Observing modes for single dish total power: OTF

6.2. Stand-alone ACA: required

6.3. Cross-correlation of 7m ACA and 12m baseline-ALMA antennas: 
     no

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


7. Frequencies:

7.1. Receiver band: Band 7

7.2. Lines and Frequencies (GHz):
		CO 3-2 345 GHz (redshifted for 10 Mpc and Ho = 75)

7.3. Spectral resolution (km/s): 2 km/s

7.4. Bandwidth or spectral coverage (km/s or GHz): 300 km/s max


9. Line intensity:

9.1. Typical value (K or Jy): 0.5-2  K 

9.2. Required rms per channel (K or Jy): 0.1 K

9.3. Spectral dynamic range: 20

9.4. Calibration requirements: absolute      10%
                               repeatability 3%
                               relative      3%


10. Polarization:  no

11. Integration time for each observing mode/receiver setting (hr): 
	90 sec hr x 19 fields  = 0.5 hours per galaxy

13CO 1-0 imaging:
-----------------

5. Spatial scales:

5.1. Angular resolution (arcsec): 1"

5.2. Range of spatial scales/FOV (arcsec): single field

5.3. Required pointing accuracy: 1"


6. Observational setup

6.1. Single dish total power data: required

     Observing modes for single dish total power: nutator

6.2. Stand-alone ACA: required

6.3. Cross-correlation of 7m ACA and 12m baseline-ALMA antennas: 
     no

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


7. Frequencies:

7.1. Receiver band: Band 3

7.2. Lines and Frequencies (GHz):
		13CO 3-2 110 (redshifted for 10 Mpc and Ho = 75)

7.3. Spectral resolution (km/s): 2 km/s

7.4. Bandwidth or spectral coverage (km/s or GHz): 300 km/s max


9. Line intensity:

9.1. Typical value (K or Jy): 0.1-0.4  K 

9.2. Required rms per channel (K or Jy): 0.025 K

9.3. Spectral dynamic range: 20

9.4. Calibration requirements: absolute      10%
                               repeatability 3%
                               relative      3%


10. Polarization:  no

11. Integration time for each observing mode/receiver setting (hr): 
						10 hr per galaxy


12. Total integration time for program (hr): 10 x (7.3 + 10 + 0.5 ) = 
							180 hours

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

Have chosen 3 CO lines as a minimum estimate of what is needed to
constrain gas density and temperature in any way.

Will pick targets that are reasonably close, because gain
in resolution and sensitivity, but not so close that we have to mosaic
at 115 GHz. 10 Mpc seems like a reasonable estimate for a typical
distance. In some cases we might chose to image a piece of a galaxy
rather than the whole thing.

Get 110 GHz continuum sensitivity of 0.0025 mJy or 0.25 mK and
345 continuum sensitivity of 0.20 mJy or  2.1 mK for free. At 345 GHz,
this is equivalent to about 1e5 Msun (1 sigma) of gas and dust within 1" at
a distance of 10 pc (30 Msun/pc^2), so will only detect the biggest clouds.

Should also do 12CO J=1-0 simultaneously with 13CO J=1-0 
to get better sensitivity to large
extended structures; doesn't remove the need for higher resolution
12CO J=1-0 imaging in its own right ...

--------------------------------------------------
Review v2.0:
 
Structure of ISM in Irr galaxies
Wilson et al. 

Seems fine. Maybe 10 is rather more Irr galaxies than normal galaxies
covered in other proposals, but given the diversity of Irr galaxies,
and potential relevance to high-redshifts it's all justified. Maybe
covering a fraction of the targets contiguously rather than sampling
might yield more impressive early results (he speculated idly)?