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    Query a catalog in the NASA/IPAC Infrared Science Archive (IRSA)
    database by position or resolvable target name.


    Uses the IDL SOCKET command to provide a query of a catalog
    in the IRSA (http://irsa.ipac.caltech.edu/) database over the Web and
    return results in an IDL structure. If outfile is set, it saves
    the query as an IPAC table file. This can be slow for large query
    results, so only write a file if needed.

Calling Sequence

    info = query_irsa_cat(targetname_or_coords, [catalog=catalog,
    radius=radius, radunits=radunits, outfile=outfile,
    change_null=change_null, /DEBUG])


    TARGETNAME_OR_COORDS - Either a string giving a resolvable target
          name (with J2000 coordinates determined by NED or SIMBAD), or a
          2-element numeric vector giving the J2000 right ascension
          and declination, both in degrees.

Optional Input

    CATALOG - string giving the identifier of the IRSA catalog to be
          searched. The complete list of catalogs and identifier strings is available in
          XML format at:
          or as an IPAC Table (ascii) at:
          In the table, the identifier string is in the "catname" column.
          If this keyword is omitted, the program will query the 2MASS point
          source catalog.
          Examples of current IRSA catalogs include:
              'wise_allsky_4band_p3as_psd' - WISE All-Sky Source Catalog
              'fp_psc' - 2MASS Point Source Catalog
              'iraspsc' - IRAS Point Source Catalog v2.1 (PSC)
              'irasfsc' - IRAS Faint Source Catalog v2.0
              'cosmos_ib_phot' - COSMOS Intermediate and Broad Band Photometry Catalog 2008
              'akari_irc' - Akari/IRC Point Source Catalogue
    RADIUS - scalar input of the radius of the search. By default it
            has a value of 60 arcsec. IRSA
          catalogs have maximum allowable search radii. These are listed on the corresponding
          web interface page for the catalog search, or in the nph-scan return table in the
          "coneradius" column.
    RADUNITS - string giving the units of the radius. By default it is 'arcsec'.
    OUTFILE - if present, the search results are written to a file with this name.
    CHANGE_NULL - a numeric value (input as integer) to put in the structure if the table uses a string for nulls. Default is -9999.
    DEBUG - /DEBUG provides some additional output.


    info - Anonymous IDL structure containing information on the catalog. The structure
          tag names are taken from the catalog column names. If no objects were found in
          the catalog, the structure values will be empty or zero. If any input parameter
          (e.g. catalog name) is invalid, the structure will have no
          content fields other than info.CREATED.
          If the query fails or is invalid, the function returns a value of -1.


          (1) Plot a histogram of the J magnitudes of all 2MASS
              point sources within 10 arcminutes of the center of the
              globular cluster M13. Save the IPAC table.
            IDL> info = query_irsa_cat('m13',radius=10,radunits='arcmin',outfile='save.tbl')
            IDL> help,/struct,info
            IDL> plothist,info.j_m,xran=[10,20]
          (2) Find the position of the faintest IRAS 60 micron
              source within 1 degree of central position of the
              COSMOS survey (10h00m28.6s +02d12m21.0s in J2000)
            IDL> info = query_irsa_cat([150.11917,2.205833], catalog='irasfsc', radius=1, radunits='deg')
            IDL> help,/struct,info
            IDL> idx = where(info.fnu_60 eq min(info.fnu_60))
            IDL> print, (info.ra)[idx], (info.dec)[idx]

Procedures Used

    READ_IPAC_VAR comes with query_irsa_cat.pro
    WEBGET(), VALID_NUM from IDLastro


    The program writes an output IPAC table file only if the
    OUTFILE keyword is set.

Modification History

    Adapted from queryvizier.pro - H. Teplitz, IPAC September 2010
    Removed requirement of writing/reading IPAC table file -
      T. Brooke, IPAC May 2011
    Longer timeout for webget, added change_null - TYB June 2013

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