REAL FUNCTION sla_RVLSRD (R2000, D2000) *+ * - - - - - - - * R V L S R D * - - - - - - - * * Velocity component in a given direction due to the Sun's motion * with respect to the dynamical Local Standard of Rest. * * (single precision) * * Given: * R2000,D2000 r J2000.0 mean RA,Dec (radians) * * Result: * Component of "peculiar" solar motion in direction R2000,D2000 (km/s) * * Sign convention: * The result is +ve when the Sun is receding from the given point on * the sky. * * Note: The Local Standard of Rest used here is the "dynamical" LSR, * a point in the vicinity of the Sun which is in a circular * orbit around the Galactic centre. The Sun's motion with * respect to the dynamical LSR is called the "peculiar" solar * motion. * * There is another type of LSR, called a "kinematical" LSR. A * kinematical LSR is the mean standard of rest of specified star * catalogues or stellar populations, and several slightly * different kinematical LSRs are in use. The Sun's motion with * respect to an agreed kinematical LSR is known as the "standard" * solar motion. To obtain a radial velocity correction with * respect to an adopted kinematical LSR use the routine sla_RVLSRK. * * Reference: Delhaye (1965), in "Stars and Stellar Systems", vol 5, * p73. * * Called: * sla_CS2C, sla_VDV * * P.T.Wallace Starlink 9 March 1994 * * Copyright (C) 1995 Rutherford Appleton Laboratory *- IMPLICIT NONE REAL R2000,D2000 REAL VA(3), VB(3) REAL sla_VDV * * Peculiar solar motion from Delhaye 1965: in Galactic Cartesian * coordinates (+9,+12,+7) km/s. This corresponds to about 16.6 km/s * towards Galactic coordinates L2 = 53 deg, B2 = +25 deg, or RA,Dec * 17 49 58.7 +28 07 04 J2000. * * The solar motion is expressed here in the form of a J2000.0 * equatorial Cartesian 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 / +0.63823, +14.58542, -7.80116 / * Convert given J2000 RA,Dec to x,y,z CALL sla_CS2C(R2000,D2000,VB) * Compute dot product with solar motion vector sla_RVLSRD=sla_VDV(VA,VB) END