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

Mon May 10 18:57:20 EDT 2010

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
>>>>> ------------------------------------------------------------------------
_______________________________________________
>>>>> mmaimcal mailing list
>>>>> mmaimcal at listmgr.cv.nrao.edu
>>>>> http://listmgr.cv.nrao.edu/mailman/listinfo/mmaimcal
>>>> _______________________________________________
>>>> Almasci_chile mailing list
>>>> Almasci_chile at lists.alma.cl
>>>> http://lists.alma.cl/mailman/listinfo/almasci_chile
>>> _______________________________________________
>>> Almasci_chile mailing list
>>> Almasci_chile at lists.alma.cl
>>> http://lists.alma.cl/mailman/listinfo/almasci_chile
>
>
> --
> 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/
>
>
> 
>
> _______________________________________________
> Almasci_chile mailing list
> Almasci_chile at lists.alma.cl
> http://lists.alma.cl/mailman/listinfo/almasci_chile
>