Kinematics and Velocity Ellipsoid of Halo Red Giants

TL;DR

This study analyzes the kinematic properties of halo red giants using a large dataset to determine velocity ellipsoids and Oort constants, revealing insights into the Galaxy's rotational dynamics.

Contribution

It provides new measurements of Oort constants and velocity ellipsoids for halo red giants, based on extensive survey data and subsample analysis.

Findings

Oort constants A = 15.6 ± 1.6 km/s/kpc, B = -13.9 ± 1.8 km/s/kpc

Galactic rotational velocity approximately 221 km/s

Velocity ellipsoid parameters for halo red giants

Abstract

In the present paper, we aim to determine the kinematical properties, velocity ellipsoid, and Oort constants using a sample of halo red giants. The study is based mainly on the space and radial velocities of about 1583 red giant stars collected from the SEGUE-1 and SEGUE-2 surveys. We divided the sample into three subsamples, the inner halo, the outer halo and the stars near the galactic plane. The fitting of the radial velocity equation gives a the mean of Oort constants, A = 15.6 +- 1.6 km s-1 kpc-1 and B= -13.9 +- 1.8 km s-1 kpc-1, the angular velocity |A-B|= 29.5 +- 0.2 km s-1 kpc-1 implying a rotational velocity of 221.25 +- 26.66 km s-1 if we take the distance to the Galactic center as 7.5 kpc.