IVOA/tvo stuff

[Herve Wozniak]

Hello Peter,

I was in Cambridge but not ADASS. I had like to participate to your 
discussion indeed. Anyway, just a few words about what you discussed 
during ADASS:

Le 30/09/2007 11:39, glemson écrivait :
...
>>> Ugo dicussed 3 levels of access:
>>> 1) low level data, the simulation data itself
>>> 2) certain sections or snapshots from the simulation (e.g. SNAP)
>>> 3) final products, this could be software telescope produced,
>>>    catalogs produced from a simulation etc.etc.
>>> #3 is the obvious thing to concentrate on. We doubt 2, but especially
>>> 1, is of interest to observers. Real power and visibility comes from
>>> well selected examples in #3.

I fully agree with you that #3 products (called Level 2 in SNAP, an 
effect of Fortran vs C array indices certainly ;-) !) are undoubtly most 
interesting for observers. Amongst these products, mock images (eg 
projection or slices), data cubes, etc., everything that looks like an 
image or a spectrum in fact, should be accessible via other SxAP IVOA 
protocols. That's why, up to now, SNAP did not dealt with this kind of 
products.

Catalogues produced by a simulation are considered as Level 1 (#2) 
products since they are generated directly from a raw simulation and 
shared generally the same structure (3D space objects) as the snapshots 
(eg catalogues of halos are lists of masses,x,y,z,vx,vy,vz n-uple as 
particles in a snapshot, but with additional properties). This level of 
data could be also interesting for an observer. IN fact, any product 
obtained after some transformation of Level 0 data but keeping the same 
spatial structure is Level 1 (the definition given in the draft document 
is however better that this one... but this is just to be short).

Finally, to produce Level 2 (#3) products, a service could have to 
access at lower level data, as raw data or catalogues. That's also what 
SNAP is designed for.

So, I think that both Levels 1 and 2 (or #2 and #3) are of interest for 
an observer.

Best regards,
Herve

-- 
_______________________________________________________________
Herve WOZNIAK      			
Centre de Recherche Astronomique de Lyon
UMR 5574 Université Lyon 1 - CNRS - ENS-Lyon
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http://www-obs.univ-lyon1.fr/labo/perso/herve.wozniak/