[daip] NH3 Map units question

[Eric Greisen]

Glen Langston wrote:
> Hi Wayne
> 
> The Units are Tmb.  You've reminded me I need to
> send an email to the AIPS group to get them to fix
> the programs that are counting on Jy/Beam to make
> the measurement tools work.
> 
> We put Jy/beam in to get the measurements that use
> beam size to work correctly, but the actual units
> are Tmb/beam.
> 
> Glen
> 
> PS Eric, the single dish community often uses T main
> beam (Tmb) for certain measurements.   Many of the
> AIPS tools, like imstat  require Jy/Beam to compute
> the integrated intensities.   Our request is that
> for any images that have beam sizes provided and
> have BUNIT = '???/Beam' should have all beam size
> corrections applied for integrated intensities.
> 
> I've notices that we have to set NCOMP=1 to get
> the map to appear to be "cleaned",  This is OK,
> but does not seem to be logically required.
> 
> Thanks
> 
>> Hi Glen,
>>
>> We are working on hard on finishing the NH3 paper from our data last
>> spring and I have a question for you. In the data reduction we
>> selected TMB as the units for the map yet the headers say Jy/beam.
>> Which is the correct unit I should be using?

I have written to you before on this subject.  T (degrees K) is itself a 
brightness unit.  Dividing by beam area then does not make sense.  Jy is 
a flux density so it must be divided by an area - beam or pixel - to get 
a brightness unit.  Therefore I have no idea what you mean by Tmb/beam.

Eric Greisen