glactc_pm: Convert between celestial and Galactic (or Supergalactic)...

In astrolibR: Astronomy Users Library

Description

Convert between celestial and Galactic (or Supergalactic) proper motion and coordinates

Usage

glactc_pm(ra, dec, mu_ra, mu_dec, year, gl, gb, mu_gl, mu_gb, j, degree=FALSE, 
fk4 = FALSE, supergalactic = FALSE, mustar=FALSE)

Arguments

ra	Right Ascension, in decimal hours (or decimal degrees if degree is set), scalar or vector
dec	declination, in decimal degrees, scalar or vector
mu_ra	Right Ascension proper motion, in any proper motion unit (angle/time), scalar or vector
mu_dec	declination proper motion, in any proper motion unit (angle/time), scalar or vector
year	equinox of ra and dec, scalar
gl	Galactic longitude, decimal degrees, scalar or vector
gb	Galactic latitude, decimal degrees, scalar or vector
mu_gl	Galactic longitude proper motion, in any proper motion unit (angle/time), scalar or vector
mu_gb	Galactic latitude proper motion, in any proper motion unit (angle/time), scalar or vector
j	integer indicator, direction of conversion 1: ra,dec,mu_ra,mu_dec –> gl,gb,mu_gl,mu_gb 2: gl,gb,mu_gl,mu_gb –> ra,dec,mu_ra,mu_dec
degree	if set, then the RA parameter (both input and output) is given in degrees rather than hours (default=FALSE)
fk4	if set, then the celestial (RA, Dec) coordinates are assumed to be input/output in the FK4 system. By default, coordinates are assumed to be in the FK5 system. (default=FALSE)
supergalactic	if set, the function returns SuperGalactic coordinates (see details). (default=FALSE)
mustar	see details (default=FALSE)

Details

If j=1, this function converts proper motion in equatorial coordinates (ra,dec) to proper motion in Galactic coordinates (gl, gb) or Supergalactic Coordinates (sgl,sgb). If j=2, the conversion is reversed from Galactic/Supergalactic coordinates to equatorial coordinates. The calculation includes precession on the coordinates, but does not take care of precession of the proper motions which is usually a very small effect.

For B1950 coordinates, set fk4=TRUE and year=1950.

If supergalactic=TRUE is set, Supergalactic coordinates are defined by de Vaucouleurs et al. (1976) to account for the local supercluster. The North pole in Supergalactic coordinates has Galactic coordinates l = 47.47, b = 6.32, and the origin is at Galactic coordinates l = 137.37, b = 0.00.

If mustar=TRUE is set, the input and output of mu_ra and mu_dec are the projections of mu in the ra or dec direction rather than the d(ra)/dt or d(mu)/dt. So mu_ra becomes mu_ra*cos(dec) and mu_gl becomes mu_gl*cos(gb).

Value

ra	Right Ascension, in decimal hours (or decimal degrees if degree is set), scalar or vector
dec	declination, in decimal degrees, scalar or vector
mu_ra	Right Ascension proper motion, in any proper motion unit (angle/time), scalar or vector
mu_dec	declination proper motion, in any proper motion unit (angle/time), scalar or vector
year	equinox of ra and dec, scalar
gl	Galactic longitude, decimal degrees, scalar or vector
gb	Galactic latitude, decimal degrees, scalar or vector
mu_gl	Galactic longitude proper motion, in any proper motion unit (angle/time), scalar or vector
mu_gb	Galactic latitude proper motion, in any proper motion unit (angle/time), scalar or vector

Author(s)

Written by Ed Shaya (Univ Maryland))2009.

R adaptation by Arnab Chakraborty June 2013

See Also

precess bprecess jprecess

Examples

# Find the SuperGalactic proper motion of M33 given its
#  equatorial proper motion mu* =(-29.2, 45.2) microas/yr.
#  Here the (*) indicates ra component is actual mu_ra*cos(dec) 
#	(Position: RA (J2000): 01 33 50.9, Dec (J2000): 30 39 35.8)
# Result: SGL = 328.46732 deg, SGB = -0.089896901 deg
#			mu_sgl = 35.02 microarcsecond/yr, mu_sgb = 38.09 microarcsecond/yr.

glactc_pm(ten(1,33,50.9), ten(30,39,35.8), -29.2, 45.2, 2000, 
     gl, gb, mu_gl, mu_gb, 1)

Example output

$gl
[1] 133.6103

$gb
[1] -31.33086

$mu_gl
[1] -38.97888

$mu_gb
[1] 39.60733

astrolibR documentation built on May 2, 2019, 3:26 a.m.