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/*
*+
* Name:
* palRvgalc
* Purpose:
* Velocity component in a given direction due to the rotation
* of the Galaxy.
* Language:
* Starlink ANSI C
* Type of Module:
* Library routine
* Invocation:
* double palRvgalc( double r2000, double d2000 )
* Arguments:
* r2000 = double (Given)
* J2000.0 mean RA (radians)
* d2000 = double (Given)
* J2000.0 mean Dec (radians)
* Returned Value:
* Component of dynamical LSR motion in direction R2000,D2000 (km/s).
* Description:
* This function returns the Component of dynamical LSR motion in
* the direction of R2000,D2000. The result is +ve when the dynamical
* LSR is receding from the given point on the sky.
*
* Notes:
* - 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.
* Authors:
* PTW: Pat Wallace (STFC)
* DSB: David Berry (JAC, Hawaii)
* {enter_new_authors_here}
* History:
* 2012-02-16 (DSB):
* Initial version.
* Adapted with permission from the Fortran SLALIB library.
* {enter_further_changes_here}
* Copyright:
* Copyright (C) 1995 Rutherford Appleton Laboratory
* Copyright (C) 2012 Science and Technology Facilities Council.
* All Rights Reserved.
* Licence:
* This program is free software: you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation, either
* version 3 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General
* License along with this program. If not, see
* <http://www.gnu.org/licenses/>.
* Bugs:
* {note_any_bugs_here}
*-
*/
#include "pal.h"
#include "pal1sofa.h"
double palRvgalc( double r2000, double d2000 ){
/* Local Variables: */
double vb[ 3 ];
/*
* 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)
*/
double va[ 3 ] = { -108.70408, +97.86251, -164.33610 };
/* Convert given J2000 RA,Dec to x,y,z. */
eraS2c( r2000, d2000, vb );
/* Compute dot product with LSR motion vector. */
return eraPdp( va, vb );
}
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