Re: [CATALOGUE] Source Catalogue DM

Pedro,

I append the mapping to the STC schema, with some additional comments. I'll be happy to answer questions.
Hope it elucidates things.

Cheers,

• Arnold

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Arnold H. Rots                                Chandra X-ray Science Center
Smithsonian Astrophysical Observatory                tel:  +1 617 496 7701
60 Garden Street, MS 67                              fax:  +1 617 495 7356
Cambridge, MA 02138                             arots-at-head.cfa.harvard.edu
USA                                     http://hea-www.harvard.edu/~arots/


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Source Catalog - STC Mapping

Following is a mapping of all elements from Pedro and Matteo's list that are present in stc:CatalogEntryLocation.

Some preliminaries:
stc:CatalogEntryLocation was designed with the following implementation in mind: The actual catalog data are presented as cells of a VOTable; the stc:CatalogEntryLocation element is present in the table header and its leafs, rather than containing actual data, are IDREFs that point to the Field that describes the column in the table, holding the actual data. However, there are clearly other ways of implementing things. The element can hold multiple coordinate systems to allow, for instance, combining equatorial and Galactic coordinates in one table; each AstroCoords element refers to a particualr AstroCoordsSystem through an IDREF attribute.

If distance is to be added, one may want to specify a 3-D Spherical coordinate system with unit "deg deg Mpc", or so. The spatial coordinate then becomes a vector of length 3, containing RA, Dec, and distance (or whatever spatial frame is selected). It does allow multiple reference frames (e.g., equatorial and Galactic). I am assuming that the reference position for all spatial coordinates (including distance) is the same and most likely the barycenter - though the reference position for redshift may be different.
Alternatively, one may want to put distance in an element with different reference frame, like Galactic coordinates.

Proper motions are spatial velocities. However, Doppler velocities fall in the Redshift category. The redshift frame in the AstroCoordSystem specifies whether it is z or Doppler velocity, the velocity definition used (optical, radio), and the reference origin (geocenter, barycenter, galactic center, LSR, etc.).

I would encourage you to add errors and I have included them in the mapping. Finally, if you use a single STC element to reference all catalog entries you may want to consider adding an AstroCoordArea element that descibes the volume in coordinate space covered by your catalog; I added those mappings, too.

Mapping to stc:CatalogEntryLocation
  (not showing attributes)

coordinates (say, RA & Dec)
  CatalogEntryLocation/AstroCoords/Position2D/Value2

errors on coordinates (say, an error circle)   CatalogEntryLocation/AstroCoords/Position2D/Error2Radius

distance
  CatalogEntryLocation/AstroCoords/Position1D/Value

error on distance
  CatalogEntryLocation/AstroCoords/Position1D/Error

proper motion (in RA and Dec)
  CatalogEntryLocation/AstroCoords/Velocity2D/Value2

errors on proper motion
  CatalogEntryLocation/AstroCoords/Velocity2D/Error2

frequency
  CatalogEntryLocation/AstroCoords/Spectral/Value

Doppler velocity
  CatalogEntryLocation/AstroCoords/Redshift/Value

error on Doppler velocity
  CatalogEntryLocation/AstroCoords/Redshift/Error

time of observation
  CatalogEntryLocation/AstroCoords/Time/TimeInstant/ISOTime   or: CatalogEntryLocation/AstroCoords/Time/TimeInstant/JDTime

major and minor axis
  CatalogEntryLocation/AstroCoords/Position2D/Size2PA/Size

position angle
  CatalogEntryLocation/AstroCoords/Position2D/Size2PA/PosAngle

catalog coverage:

  CatalogEntryLocation/AstroCoordArea/TimeInterval
  CatalogEntryLocation/AstroCoordArea/Region
  CatalogEntryLocation/AstroCoordArea/VelInterval
  CatalogEntryLocation/AstroCoordArea/SpectralInterval
  CatalogEntryLocation/AstroCoordArea/RedshiftInterval