Galactocentric Velocity Research Articles

Radial velocities of remote globular clusters - Stalking the missing mass

Measurements good to 25 km/s are presented of radial velocities of five remote galactic globular clusters, based on aperture-plate spectra of individual stars at 3.0 A resolution. Velocities with respect to the galactic rest-frame of two individual systems, Eridanus and Palomar 14, are large enough to suggest a total mass for the Galaxy of 1 trillion solar masses. A similar mass is inferred from the average of the galactocentric distance times velocity squared. 36 references.

The velocity of escape from the Galaxy in the solar neighbourhood

The expected properties of stars moving with extremely high velocities relative to the centre of the Galaxy are discussed. Although the kinematic behaviour of the fastest known subdwarfs is consistent with unbound orbits, observational upper limits on the numbers of faint giant stars in the general field strongly suggest that these subdwarfs are bound to the Galaxy. If this is the case, only a lower limit to the value of the velocity of escape in the solar neighbourhood can be obtained. After allowance for observational error, this lower limit is about 400 km s–1. Although all known subdwarfs are probably in bound orbits, there is evidence that the mode of origin of the peculiar velocities of subdwarfs with extremely large galactocentric velocities is different from that of other high-velocity stars.

HD 27507 - A STAR ESCAPING FROM OUR GALAXY?

ABSTRACT HD 27507 is a horizontal-branch star with a radial velocity of 348 km/s. Its galactocentric velocity (368 km/s) is very little affected by a possible error in the adopted circular velocity in the vicinity of the sun. Since it is very unlikely that a star with a galactocentric velocity within 10 km/s of the escape velocity is found, it can be concluded that the escape velocity is at least 378 + or - 20 km/s. The redetermination of the proper motion of HD 27507 can substantially reduce the margin of uncertainty.

The galactocentric circular velocity and corrections to the precession constant and the motion of the Equinox.

The galactocentric circular velocity and corrections to the precession constant and the motion of the Equinox.