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