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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
*-
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
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