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  Query any catalog in the Vizier database by position


  Uses the IDL SOCKET command to provide a positional query of any catalog
  in the the Vizier (http://vizier.u-strasbg.fr/) database over the Web and
  return results in an IDL structure.

Calling Sequence

    info = QueryVizier(catalog, targetname_or_coords, [ dis
                        /ALLCOLUMNS, /CANADA, CONSTRAINT= ,/VERBOSE ])


      CATALOG - Scalar string giving the name of the VIZIER catalog to be
            searched. The complete list of catalog names is available at
            http://vizier.u-strasbg.fr/vizier/cats/U.htx .
            Popular VIZIER catalogs include
            'II/294' - Sloan SDSS photometric catalog Release 7 (2009)
            '2MASS-PSC' - 2MASS point source catalog (2003)
            'GSC2.3' - Version 2.3.2 of the HST Guide Star Catalog (2006)
            'USNO-B1' - Verson B1 of the US Naval Observatory catalog (2003)
            'NVSS' - NRAO VLA Sky Survey (1998)
            'B/DENIS/DENIS' - 2nd Deep Near Infrared Survey of southern Sky
            'I/259/TYC2' - Tycho-2 main catalog (2000)
            'I/311/HIP2' - Hipparcos main catalog, new reduction (2007)
          Note that some names will prompt a search of multiple catalogs
          and QUERYVIZIER will only return the result of the first search.
          Thus, setting catalog to "HIP2" will search all catalogs
          associated with the Hipparcos mission, and return results for the
          first catalog found. To specifically search the Hipparcos or
          Tycho main catalogs use the VIZIER catalog names listed above
      TARGETNAME_OR_COORDS - Either a scalar string giving a target name,
          (with J2000 coordinates determined by SIMBAD), or a 2-element
          numeric vector giving the J2000 right ascension in *degrees* and
          the target declination in degrees.
          If the targetname is set to 'NONE' then QUERYVIZIER will perform
          an all-sky search using the constraints given in the CONSTRAINT

Optional Input

    dis - scalar or 2-element vector. If one value is supplied then this
          is the search radius in arcminutes. If two values are supplied
          then this is the width (i.e., in longitude direction) and height
          of the search box. Default is a radius search with radius of
          5 arcminutes


  info - Anonymous IDL structure containing information on the catalog
          sources within the specified distance of the specified center. The
          structure tag names are identical with the VIZIER catalog column
          names, with the exception of an occasional underscore
          addition, if necessary to convert the column name to a valid
          structure tag. The VIZIER Web page should consulted for the
          column names and their meaning for each particular catalog..
          If the tagname is numeric and the catalog field is blank then either
          NaN (if floating) or -1 (if integer) is placed in the tag.
          If no sources are found within the specified radius, or an
          error occurs in the query then -1 is returned.

Optional Keywords

          /ALLCOLUMNS - if set, then all columns for the catalog are returned
                The default is to return a smaller VIZIER default set.
          /CANADA - By default, the query is sent to the main VIZIER site in
            Strasbourg, France. If /CANADA is set then the VIZIER site
            at the Canadian Astronomical Data Center (CADC) is used instead.
            Note that not all Vizier sites have the option to return
            tab-separated values (TSV) which is required by this program.
          CONSTRAINT - string giving additional nonpositional numeric
            constraints on the entries to be selected. For example, when
            in the GSC2.3 catalog, to only select sources with Rmag < 16 set
            Constraint = 'Rmag<16'. Multiple constraints can be
            separated by commas. Use '!=' for "not equal", '<=' for smaller
            or equal, ">=" for greater than or equal. See the complete list
            of operators at
            For this keyword only, **THE COLUMN NAME IS CASE SENSITIVE** and
            must be written exactly as displayed on the VIZIER Web page.
            Thus for the GSC2.3 catalog one must use 'Rmag' and not 'rmag' or
            'RMAG'. In addition, *DO NOT INCLUDE ANY BLANK SPACE* unless it
            is a necessary part of the query.
          /SILENT - If set, then no message will be displayed if no sources
                are found. Error messages are still displayed.
          /VERBOSE - If set then the query sent to the VIZIER site is
              displayed, along with the returned title(s) of found catalog(s)


          (1) Plot a histogram of the J magnitudes of all 2MASS point sources
          stars within 10 arcminutes of the center of the globular cluster M13
          IDL> info = queryvizier('2MASS-PSC','m13',10)
          IDL> plothist,info.jmag,xran=[10,20]
          (2) Find the brightest J mag GSC2.3 source within 3' of the
              J2000 position ra = 10:12:34, dec = -23:34:35
          IDL> str = queryvizier('GSC2.3',[ten(10,12,34)*15,ten(-23,34,35)],3)
          IDL> print,min(str.jmag,/NAN)
          (3) Find sources with V < 19 in the Magellanic Clouds Photometric
              Survey (Zaritsky+, 2002) within 5 arc minutes of the position
              00:47:34 -73:06:27
              Checking the VIZIER Web page we find that this catalog is
          IDL> catname = 'J/AJ/123/855/table1'
          IDL> ra = ten(0,47,34)*15 & dec = ten(-73,6,27)
          IDL> str = queryvizier(catname, [ra,dec], 5, constra='Vmag<19')
          (4) Perform an all-sky search of the Tycho-2 catalog for stars with
              BTmag = 13+/-0.1
        IDL> str = queryvizier('I/259/TYC2','NONE',constrain='BTmag=13+/-0.1')

Procedures Used


To Do

      (1) Allow specification of output sorting

Modification History

        Written by W. Landsman SSAI October 2003
        Give structure name returned by VIZIER not that given by user
                    W. Landsman February 2004
        Don't assume same format for all found sources W. L. March 2004
        Added CONSTRAINT keyword for non-positional constraints WL July 2004
        Remove use of EXECUTE() statement WL June 2005
        Make dis optional as advertised WL August 2005
        Update for change in Vizier output format WL February 2006
        Fix problem in Feb 2006 update when only 1 object found
                    WL/D.Apai March 2006
        Accept 'E' format for floating point. M. Perrin April 2006
        Added /ALLCOLUMNS option to return even more data. M. Perrin, May 2006
        Return anonymous structure W. Landsman May 2006
        Removed V6.0 notation to restore V5 compatibility W.Landsman July2006
        Accept target='NONE' for all-sky search, allow '+/-' constraints
                W. Landsman October 2006
        Use HTTP 1.0 protocol in call to webget.pro
        Use vector form of IDL_VALIDNAME if V6.4 or later W.L. Dec 2007
        Update Strasbourg Web address for target name W.L. 3 March 2008
        Also update Web address for coordinate search W.L. 7 March 2008
        Allow for 'D' specification format R. Gutermuth/W.L. June 2008
        Allow for possible lower-case returned formats W.L. July 2008
        Use STRCOMPRESS2()to remove blanks around operators in constraint
              string W.L. August 2008
        Added /SILENT keyword W.L. Jan 2009
        Avoid error if output columns but not data returned W.L. Mar 2010
        Ignore vector tags (e.g. SED spectra) W.L. April 2011
        Better checking when more than one catalog returned W.L. June 2012

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