List of Observables for Observation Core components DM

[Francois Bonnarel]

Hi pat,
    We have checked your email with Mireille
   Modifications will be made to the document  by Mireille
Regards
François
Patrick Dowler a écrit :
> On Tuesday 07 September 2010 14:23:04 Mireille Louys wrote:
>   
>> please look at
>> http://www.ivoa.net/cgi-bin/twiki/bin/view/IVOA/ObsTap
>>     
>
> Comments from various astronomers in CADC:
>
> --
> You're missing "scaled counts".... You could argue that they are the same
> [as ADU] from a philosophic point of view, but to an astronomer, they mean 
> something different.
> --
>   
Ok
> The units of flux density are Jy, not Jy/Hz.
> So also flux surface brightness in your table should be named flux 
> density surface brightness.
>   
this was our mistake. Will be fixed
> --
> And, to make life more complex, most radio continuum measurements are
> actually phot.flux.sb, with the intensity integrated over a passband,
> that people scale into Jy units on the assumption that the emission does
> not vary much across the passband.  
>
>   
   A that was  the trick , two different quantities with the same unit ?
> For fields that do not include much extended emission, it is common to
> scale the image as a surface brightness in Jy per beam.  This is very
> handy when the fields include point sources whose flux can then be read
> directly from the peak "surface brightness", but is an abomination for
> extended sources whose spacially integrated fluxes must be scaled by the
> effective beam area.
>
>   
   And the "beam" is only for this dataset, isn't it? So actually it's a 
relative
quantity. Has the shape or the size of the beam  to be given somewhere ?
> Also, radio heterodyne observations are typically reported as antenna
> temperatures Ta* in K.  For spectra and datacubes, the assumption is
> implicitly made that the emission is extended spacially on the scale of
> the main beam, and is more broad-band then the frequency resolution.
>
>   
Will be added
> Again, for heterodyne observations of spectral lines, it is common to
> give "integrated intensities", in which the energy axis is reported in
> radial velocity units rather than frequency or wavelength, so the
> integrated intensity units are K km/s.
> --
>
>   
Will be added


-- 
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François   Bonnarel           Observatoire Astronomique de Strasbourg
CDS (Centre de données        11, rue de l'Université
astronomiques de Strasbourg)  F--67000 Strasbourg (France)

Tel: +33-(0)3 68 85 24 11     WWW: http://cdsweb.u-strasbg.fr/people/fb.html
Fax: +33-(0)3 68 85 24 25     E-mail: francois.bonnarel at astro.unistra.fr
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