[mmaimcal] [Almasci_chile] Some thoughts on ALMA calibrator sources

[Stuartt Corder]

Hi all,

I think we are collecting enough information that we should call another 
amplitude calibration team meeting and discuss some of the details that 
people have provided along this thread.  I think the other thing to 
start talking about is how to *start* approaching this with ALMA.  I 
have recently developed a script that will do a dip, 
planet/asteroid/moon observation and then start through the list of 
quasars.  The current catalog has some structures (Al mentioned this 
earlier, sourceCatalog.py) for predicting flux at various bands 
(basically a spectral slope and 3 mm flux).  Of course this is all 
defaulted to flat spectrum at this point but the structure exists.  
However, the tools in sourceCat are designed for catalogs with <= a few 
hundred sources (i.e., they have rather unintelligent source searching 
routines..I can say this because I wrote them).  If we are really going 
to start fashioning a catalog of thousands, we need to have a separate 
catalog that includes some information (like last observed date) so we 
can add options to observe ones with dates older than X many days.  We 
also need some sorting routines because we will want to do parts of the 
sky (this isn't hard, someone needs to do it, the most likely candidate 
for that is me). 

Thanks for all the comments.  The ampcal team is supposed to do both 
these sorts of studies and commission the system for accurate 
measurement of the flux scales.  Right now I many of you are not on that 
team.  If you would like to be included (specifically Al, Satoki, and 
Anita since your involvement is both relevant and ALMA-centric) let me 
know and I'll put you on the team distribution.  Rudy, no worries on 
you, you are already on it.

Stuartt
> Dear Al and all,
>
> In case of SMA southern calibrator sources (which cannot be observed from
> NMA, OVRO, BIMA, or PdBI), we first collect the possible calibrator sources
> from the ATCA & VLA calibrator source catalogs (+ some VLBI calibrator
> sources).  If there are two frequency information, we estimated 230 GHz
> flux from those, but if not, we used typical spectra index (-0.8?  I
> forgot...), and estimated 230 GHz flux.  We then put some lower limit in
> estimated flux at 230 GHz (> 0.5 Jy?  Again I forgot...) and made a survey
> catalog, and then we actually observed.  If it was bright (>0.5 Jy?), we
> put the source in the official SMA catalog.  Some sources observed several
> times, but some only observed once at the survey.  So, it is not perfect,
> but the number of calibrator sources increased.
>
> Just my two cents.
>
> Cheers,
> Satoki
>
>
>
> Al Wootten :
>   
>> Hi folks
>>
>> It is a good time to consider this subject again.
>>
>> As we discussed at the Dec 09 Sci IPT meeting the SPT survey sources 
>> presented in:
>> http://arxiv.org/abs/0912.2338
>> support the predictions made in the numerous ALMA memos on the subject. 
>>   The area surveyed was very limited but of course this is a dynamic 
>> field with Planck and the SPT still exploring.
>>
>> I think sourceCatalog.py is a derivative of SMA and other catalogs but 
>> ALMA is reaching the point where it can contribute usefully to compendia.
>>
>> There was a plan at some point for a comprehensive EVLA/VLB/ALMA catalog 
>> but I do not know where that stands or whether ALMA needs an independent 
>> initiative.  Temporal measurements are critical--certain SBs run in 
>> March used calibrators which had worked well for the SMA but whose flux 
>> had faded to uselessness even for the more sensitive ALMA 3-antenna array.
>>
>> Clear skies,
>> Al
>>
>> Harvey Liszt wrote:
>>     
>>> Something to keep boredom at bay. Attached.
>>>
>>> H
>>>
>>>
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-- 
Stuartt Corder
Jansky Fellow
ALMA Commissioning Scientist
Av Apoquindo 3650 Piso 18 (mail)
Av Apoquindo 3946 Piso 19 (location)
Las Condes, Santiago, Chile
+56 2 467 6247 (work)
+56 7 887 7681 (cell)