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

[Al Wootten]

Count me in!

Al

Stuartt Corder wrote:
> 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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> 
>