| 1 | /*
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| 2 | *+
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| 3 | * Name:
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| 4 | * palRvgalc
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| 5 |
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| 6 | * Purpose:
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| 7 | * Velocity component in a given direction due to the rotation
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| 8 | * of the Galaxy.
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| 9 |
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| 10 | * Language:
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| 11 | * Starlink ANSI C
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| 12 |
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| 13 | * Type of Module:
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| 14 | * Library routine
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| 15 |
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| 16 | * Invocation:
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| 17 | * double palRvgalc( double r2000, double d2000 )
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| 18 |
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| 19 | * Arguments:
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| 20 | * r2000 = double (Given)
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| 21 | * J2000.0 mean RA (radians)
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| 22 | * d2000 = double (Given)
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| 23 | * J2000.0 mean Dec (radians)
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| 24 |
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| 25 | * Returned Value:
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| 26 | * Component of dynamical LSR motion in direction R2000,D2000 (km/s).
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| 27 |
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| 28 | * Description:
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| 29 | * This function returns the Component of dynamical LSR motion in
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| 30 | * the direction of R2000,D2000. The result is +ve when the dynamical
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| 31 | * LSR is receding from the given point on the sky.
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| 32 | *
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| 33 | * Notes:
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| 34 | * - The Local Standard of Rest used here is a point in the
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| 35 | * vicinity of the Sun which is in a circular orbit around
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| 36 | * the Galactic centre. Sometimes called the "dynamical" LSR,
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| 37 | * it is not to be confused with a "kinematical" LSR, which
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| 38 | * is the mean standard of rest of star catalogues or stellar
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| 39 | * populations.
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| 40 | *
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| 41 | * Reference:
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| 42 | * - The orbital speed of 220 km/s used here comes from Kerr &
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| 43 | * Lynden-Bell (1986), MNRAS, 221, p1023.
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| 44 |
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| 45 | * Authors:
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| 46 | * PTW: Pat Wallace (STFC)
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| 47 | * DSB: David Berry (JAC, Hawaii)
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| 48 | * {enter_new_authors_here}
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| 49 |
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| 50 | * History:
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| 51 | * 2012-02-16 (DSB):
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| 52 | * Initial version.
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| 53 | * Adapted with permission from the Fortran SLALIB library.
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| 54 | * {enter_further_changes_here}
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| 55 |
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| 56 | * Copyright:
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| 57 | * Copyright (C) 1995 Rutherford Appleton Laboratory
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| 58 | * Copyright (C) 2012 Science and Technology Facilities Council.
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| 59 | * All Rights Reserved.
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| 60 |
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| 61 | * Licence:
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| 62 | * This program is free software: you can redistribute it and/or
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| 63 | * modify it under the terms of the GNU Lesser General Public
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| 64 | * License as published by the Free Software Foundation, either
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| 65 | * version 3 of the License, or (at your option) any later
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| 66 | * version.
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| 67 | *
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| 68 | * This program is distributed in the hope that it will be useful,
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| 69 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 70 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 71 | * GNU Lesser General Public License for more details.
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| 72 | *
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| 73 | * You should have received a copy of the GNU Lesser General
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| 74 | * License along with this program. If not, see
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| 75 | * <http://www.gnu.org/licenses/>.
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| 76 |
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| 77 | * Bugs:
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| 78 | * {note_any_bugs_here}
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| 79 | *-
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| 80 | */
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| 81 |
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| 82 | #include "pal.h"
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| 83 | #include "pal1sofa.h"
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| 84 |
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| 85 | double palRvgalc( double r2000, double d2000 ){
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| 86 |
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| 87 | /* Local Variables: */
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| 88 | double vb[ 3 ];
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| 89 |
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| 90 | /*
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| 91 | * LSR velocity due to Galactic rotation
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| 92 | *
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| 93 | * Speed = 220 km/s
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| 94 | * Apex = L2,B2 90deg, 0deg
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| 95 | * = RA,Dec 21 12 01.1 +48 19 47 J2000.0
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| 96 | *
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| 97 | * This is expressed in the form of a J2000.0 x,y,z vector:
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| 98 | *
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| 99 | * VA(1) = X = -SPEED*COS(RA)*COS(DEC)
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| 100 | * VA(2) = Y = -SPEED*SIN(RA)*COS(DEC)
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| 101 | * VA(3) = Z = -SPEED*SIN(DEC)
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| 102 | */
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| 103 |
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| 104 | double va[ 3 ] = { -108.70408, +97.86251, -164.33610 };
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| 105 |
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| 106 | /* Convert given J2000 RA,Dec to x,y,z. */
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| 107 | eraS2c( r2000, d2000, vb );
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| 108 |
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| 109 | /* Compute dot product with LSR motion vector. */
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| 110 | return eraPdp( va, vb );
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| 111 | }
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