gal_uvw {astrolibR} R Documentation

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

### 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)

[Package astrolibR version 0.1 Index]