gal_uvw: Calculate the Galactic space velocity (U,V,W) of a star

In astrolibR: Astronomy Users Library

Description

Calculate the Galactic space velocity (U,V,W) of a star

Usage

gal_uvw(distance, lsr=F, ra, dec, pmra, pmdec, vrad, plx)

Arguments

distance	distance, scalar or vector, in parsecs
lsr	if =TRUE, then output velocities are corrected for solar motion
ra	Right Ascension, scalar or vector, in decimal degrees
dec	declination, scalar or vector, in decimal degrees
pmra	proper motion in R.A., scalar or vector, in milliarcseconds/yr
pmdec	proper motion in declination, scalar or vector, in milliarcseconds/yr
vrad	radial velocity, scalar or vector, in km/s
plx	parallax, scalar or vector, in milliarcseconds

Details

Calculates the Galactic space velocity U, V, W of star given its coordinates, proper motion, distance (or parallax), and radial velocity. ; The calculation follows the general outline of Johnson & Soderblom (1987) except that U is positive outward toward the Galactic anticenter, and the J2000 transformation matrix to Galactic coordinates is taken from the introduction to the Hipparcos catalog.

The distance parameter should be zero if parallax plx is provided. If the user has proper motion in R.A. given in seconds of time/yr, mu_alpha, then it should first be converted to seconds of time/yr using

pmra = 15*mu_alpha*cos(dec)

.

If lsr=TRUE, then output velocities are corrected to the local standard of rest (LSR) assuming a solar motion (U,V,W)_Sun = (-8.5, 13.38, 6.49) km/s, as given by Coskunoglu et al. 2011). Note that the value of the solar motion through the LSR remains poorly determined.

Value

U	velocity positive toward the Galactic anticenter, in km/s
V	velocity positive in the direction of Galactic rotation, in km/s
W	velocity positive toward the North Galactic Pole, in km/s

Author(s)

Written by W. Landsman, December 2000

R adaptation by Arnab Chakraborty (June 2013)

References

Coskunoglu, B., Ak, S., Bilir, S., et al. 2011, Local stellar kinematics from the RAVE data. I. Local standard of rest, Mon. Not. Royal Astron. Soc., 412, 1237-1245. http://adsabs.harvard.edu/abs/2011MNRAS.412.1237C

Johnson, D. R. H. and Soderblom, D. R., 1987, Calculating galactic space velocities and their uncertainties, with an application to the Ursa Major group, Astron. J., 93, 864-867. http://adsabs.harvard.edu/abs/1987AJ.....93..864J

Examples

#  Compute (U,V,W) for the halo star HD 6755 using measurments by the Hipparcos satellite
#  Result: u=141.2  v = -491.7  w = 93.9        ;km/s

gal_uvw(139, lsr=TRUE, ten(1,9,42.3)*15., ten(61,32,49.5), 628.42, 76.65, -321.4)

Example output

[1] -184.7924
$u
[1] 142.6795

$v
[1] -483.5498

$w
[1] 93.19753

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