[mmaimcal] [Almasci_chile] Some thoughts of ALMA calibrator sources
Bryan Butler
bbutler at nrao.edu
Fri May 14 11:22:57 EDT 2010
the flux densities of all of these sources will be variable, so you're
never going to be able to get away from that. predictions are probably
fine. we have provision in our source model for observations over time
(flux density, structure, etc.).
-bryan
Ruediger Kneissl wrote, On 5/10/10 16:57:
> Hi all,
>
> We should obviously discuss this in the meeting Stuartt is going to organise,
> but here just some thoughts from a conversation with Robert.
>
> Right now the catalogue is being used for interferometric pointing, baseline
> determination, etc. and for these purposes the number of sources is
> sufficient. The quality of the estimated fluxes is more important in order to
> optimize the observing efficiency. So simply adding sources with predicted
> fluxes would not be helpful.
>
> When for some early science (verification) projects we need close-by
> calibrators, we will need to search specifically those areas around the
> science targets, from all available catalogues. In the longer term, towards
> early science, we will need the network of sources around the sky to be
> efficient in our projects.
>
> I would suggest that we aim to get the Planck source candidate list around
> this summer (when the component separation and source extraction has matured),
> which will give us SEDs in 9 channels from 30 to 900 GHz to pre-select likely
> candidates. And we can use specifically ATNF and other catalogues to check
> compactness and improve the positional accuracy, if needed. At this point it
> would probably be worth spending the time to observe a larger number of
> sources with ALMA, also with more available antennas, to verify suitable
> calibrators.
>
> Ruediger
>
>
> On Mon, May 10, 2010 4:49 pm, Harvey Liszt wrote:
>> I of course can give you as many of the predicted-to-be-strong-at-100 GHz
> ATNF sources as you want, in the format of the existing .py script or
> whatever.
>> H.
>> -----------------------------
>>
>> On 5/10/10 4:39 PM, 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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>> --
>> Harvey S. Liszt work:+1 434.296.0344 fax 0278
> Scientist & Spectrum Manager home:+1 434.973.3744
>> National Radio Astronomy Observatory cell:+1 434.227.6356 (+41792953708)
> 520 Edgemont Road mailto:hliszt at nrao.edu
>> Charlottesville, VA 22903-2475 http://www.cv.nrao.edu/~hliszt
>>
>> "Be Kind To Radio Astronomy"
>> http://www.nrao.edu/~hliszt/RFI/
>>
>>
>>
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