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slalib/rvgalc.f

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+      REAL FUNCTION sla_RVGALC (R2000, D2000)
+*+
+*     - - - - - - -
+*      R V G A L C
+*     - - - - - - -
+*
+*  Velocity component in a given direction due to the rotation
+*  of the Galaxy (single precision)
+*
+*  Given:
+*     R2000,D2000   real    J2000.0 mean RA,Dec (radians)
+*
+*  Result:
+*     Component of dynamical LSR motion in direction R2000,D2000 (km/s)
+*
+*  Sign convention:
+*     The result is +ve when the dynamical LSR is receding from the
+*     given point on the sky.
+*
+*  Note:  The Local Standard of Rest used here is a point in the
+*         vicinity of the Sun which is in a circular orbit around
+*         the Galactic centre.  Sometimes called the "dynamical" LSR,
+*         it is not to be confused with a "kinematical" LSR, which
+*         is the mean standard of rest of star catalogues or stellar
+*         populations.
+*
+*  Reference:  The orbital speed of 220 km/s used here comes from
+*              Kerr & Lynden-Bell (1986), MNRAS, 221, p1023.
+*
+*  Called:
+*     sla_CS2C, sla_VDV
+*
+*  P.T.Wallace   Starlink   23 March 1994
+*
+*  Copyright (C) 1995 Rutherford Appleton Laboratory
+*
+*  License:
+*    This program is free software; you can redistribute it and/or modify
+*    it under the terms of the GNU General Public License as published by
+*    the Free Software Foundation; either version 2 of the License, or
+*    (at your option) any later version.
+*
+*    This program is distributed in the hope that it will be useful,
+*    but WITHOUT ANY WARRANTY; without even the implied warranty of
+*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+*    GNU General Public License for more details.
+*
+*    You should have received a copy of the GNU General Public License
+*    along with this program (see SLA_CONDITIONS); if not, write to the 
+*    Free Software Foundation, Inc., 59 Temple Place, Suite 330, 
+*    Boston, MA  02111-1307  USA
+*
+*-
+
+      IMPLICIT NONE
+
+      REAL R2000,D2000
+
+      REAL VA(3), VB(3)
+
+      REAL sla_VDV
+
+*
+*  LSR velocity due to Galactic rotation
+*
+*  Speed = 220 km/s
+*  Apex  = L2,B2  90deg, 0deg
+*        = RA,Dec  21 12 01.1  +48 19 47  J2000.0
+*
+*  This is expressed in the form of a J2000.0 x,y,z vector:
+*
+*      VA(1) = X = -SPEED*COS(RA)*COS(DEC)
+*      VA(2) = Y = -SPEED*SIN(RA)*COS(DEC)
+*      VA(3) = Z = -SPEED*SIN(DEC)
+
+      DATA VA / -108.70408, +97.86251, -164.33610 /
+
+
+
+*  Convert given J2000 RA,Dec to x,y,z
+      CALL sla_CS2C(R2000,D2000,VB)
+
+*  Compute dot product with LSR motion vector
+      sla_RVGALC=sla_VDV(VA,VB)
+
+      END