GAL_UVW

     Calculate the Galactic space velocity (U,V,W) of star

     Calculates the Galactic space velocity U, V, W of star given its
     (1) coordinates, (2) proper motion, (3) distance (or parallax), and
     (4) radial velocity.

     GAL_UVW, U, V, W, [/LSR, RA=, DEC=, PMRA= ,PMDEC=, VRAD= , DISTANCE=
              PLX= ]

      U - Velocity (km/s) positive toward the Galactic *anti*center
      V - Velocity (km/s) positive in the direction of Galactic rotation
      W - Velocity (km/s) positive toward the North Galactic Pole

      User must supply a position, proper motion,radial velocity and distance
      (or parallax).    Either scalars or vectors can be supplied.
     (1) Position:
      RA - Right Ascension in *Degrees*
      Dec - Declination in *Degrees*
     (2) Proper Motion
      PMRA = Proper motion in RA in arc units (typically milli-arcseconds/yr)
      PMDEC = Proper motion in Declination (typically mas/yr)
     (3) Radial Velocity
      VRAD = radial velocity in km/s
     (4) Distance or Parallax
      DISTANCE - distance in parsecs
                 or
      PLX - parallax with same distance units as proper motion measurements
            typically milliarcseconds (mas)

      /LSR - If this keyword is set, then the output velocities will be
             corrected for the solar motion (U,V,W)_Sun = (-9,+12,+7)
             (Mihalas & Binney, 1981) to the local standard of rest

      (1) Compute the U,V,W coordinates for the halo star HD 6755.
          Use values from Hipparcos catalog, and correct to the LSR
      ra = ten(1,9,42.3)*15.    & dec = ten(61,32,49.5)
      pmra = 627.89  &  pmdec = 77.84         ;mas/yr
      dis = 144    &  vrad = -321.4
      gal_uvw,u,v,w,ra=ra,dec=dec,pmra=pmra,pmdec=pmdec,vrad=vrad,dis=dis,/lsr
          ===>  u=154  v = -493  w = 97        ;km/s
      (2) Use the Hipparcos Input and Output Catalog IDL databases (see
      http://idlastro.gsfc.nasa.gov/ftp/zdbase/) to obtain space velocities
      for all stars within 10 pc with radial velocities > 10 km/s
      dbopen,'hipparcos,hic'      ;Need Hipparcos output and input catalogs
      list = dbfind('plx>100,vrad>10')      ;Plx > 100 mas, Vrad > 10 km/s
      dbext,list,'pmra,pmdec,vrad,ra,dec,plx',pmra,pmdec,vrad,ra,dec,plx
      ra = ra*15.                 ;Need right ascension in degrees
      GAL_UVW,u,v,w,ra=ra,dec=dec,pmra=pmra,pmdec=pmdec,vrad=vrad,plx = plx
      forprint,u,v,w              ;Display results

      Follows the general outline of Johnson & Soderblom (1987, AJ, 93,864)
      except that U is positive outward toward the Galactic *anti*center, and
      the J2000 transformation matrix to Galactic coordinates is taken from
      the introduction to the Hipparcos catalog.

      Written, W. Landsman                       December   2000

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