FACT++  1.0
palRvgalc.c
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1 /*
2 *+
3 * Name:
4 * palRvgalc
5 
6 * Purpose:
7 * Velocity component in a given direction due to the rotation
8 * of the Galaxy.
9 
10 * Language:
11 * Starlink ANSI C
12 
13 * Type of Module:
14 * Library routine
15 
16 * Invocation:
17 * double palRvgalc( double r2000, double d2000 )
18 
19 * Arguments:
20 * r2000 = double (Given)
21 * J2000.0 mean RA (radians)
22 * d2000 = double (Given)
23 * J2000.0 mean Dec (radians)
24 
25 * Returned Value:
26 * Component of dynamical LSR motion in direction R2000,D2000 (km/s).
27 
28 * Description:
29 * This function returns the Component of dynamical LSR motion in
30 * the direction of R2000,D2000. The result is +ve when the dynamical
31 * LSR is receding from the given point on the sky.
32 *
33 * Notes:
34 * - The Local Standard of Rest used here is a point in the
35 * vicinity of the Sun which is in a circular orbit around
36 * the Galactic centre. Sometimes called the "dynamical" LSR,
37 * it is not to be confused with a "kinematical" LSR, which
38 * is the mean standard of rest of star catalogues or stellar
39 * populations.
40 *
41 * Reference:
42 * - The orbital speed of 220 km/s used here comes from Kerr &
43 * Lynden-Bell (1986), MNRAS, 221, p1023.
44 
45 * Authors:
46 * PTW: Pat Wallace (STFC)
47 * DSB: David Berry (JAC, Hawaii)
48 * {enter_new_authors_here}
49 
50 * History:
51 * 2012-02-16 (DSB):
52 * Initial version.
53 * Adapted with permission from the Fortran SLALIB library.
54 * {enter_further_changes_here}
55 
56 * Copyright:
57 * Copyright (C) 1995 Rutherford Appleton Laboratory
58 * Copyright (C) 2012 Science and Technology Facilities Council.
59 * All Rights Reserved.
60 
61 * Licence:
62 * This program is free software: you can redistribute it and/or
63 * modify it under the terms of the GNU Lesser General Public
64 * License as published by the Free Software Foundation, either
65 * version 3 of the License, or (at your option) any later
66 * version.
67 *
68 * This program is distributed in the hope that it will be useful,
69 * but WITHOUT ANY WARRANTY; without even the implied warranty of
70 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
71 * GNU Lesser General Public License for more details.
72 *
73 * You should have received a copy of the GNU Lesser General
74 * License along with this program. If not, see
75 * <http://www.gnu.org/licenses/>.
76 
77 * Bugs:
78 * {note_any_bugs_here}
79 *-
80 */
81 
82 #include "pal.h"
83 #include "pal1sofa.h"
84 
85 double palRvgalc( double r2000, double d2000 ){
86 
87 /* Local Variables: */
88  double vb[ 3 ];
89 
90 /*
91 * LSR velocity due to Galactic rotation
92 *
93 * Speed = 220 km/s
94 * Apex = L2,B2 90deg, 0deg
95 * = RA,Dec 21 12 01.1 +48 19 47 J2000.0
96 *
97 * This is expressed in the form of a J2000.0 x,y,z vector:
98 *
99 * VA(1) = X = -SPEED*COS(RA)*COS(DEC)
100 * VA(2) = Y = -SPEED*SIN(RA)*COS(DEC)
101 * VA(3) = Z = -SPEED*SIN(DEC)
102 */
103 
104  double va[ 3 ] = { -108.70408, +97.86251, -164.33610 };
105 
106 /* Convert given J2000 RA,Dec to x,y,z. */
107  eraS2c( r2000, d2000, vb );
108 
109 /* Compute dot product with LSR motion vector. */
110  return eraPdp( va, vb );
111 }
double eraPdp(double a[3], double b[3])
Definition: pdp.c:3
double palRvgalc(double r2000, double d2000)
Definition: palRvgalc.c:85
void eraS2c(double theta, double phi, double c[3])
Definition: s2c.c:3