New Constraints on the Galactic Bar

Abstract

Previous work has related the Galactic Bar to structure in the local stellar velocity distribution. Here we show that the Bar also influences the spatial gradients of the velocity vector via the Oort constants. By numerical integration of test-particles we simulate measurements of the Oort C value in a gravitational potential including the Galactic Bar. We account for the observed trend that C is increasingly negative for stars with higher velocity dispersion. By comparing measurements of C with our simulations we improve on previous models of the Bar, estimating that the Bar pattern speed is Omega_b/Omega_0=1.87\pm0.04, where Omega_0 is the local circular frequency, and the Bar angle lies within 20<phi_0<45 deg. We find that the Galactic Bar affects measurements of the Oort constants A and B less than ~2 km/s/kpc for the hot stars.

4 pages, 2 figures, Accepted to ApJ Letters. Replaced with accepted version

References in corpus (4)

• Modelling the Galactic bar using OGLE-II Red Clump Giant Stars
• The Bulge Radial Velocity Assay (BRAVA): I. Techniques and a Rotation Curve
• Disentangling the Hercules stream
• The Effect of Spiral Structure on the Measurements of the Oort Constants

Cited by in corpus (5)

• Is the Milky Way ringing? The hunt for high velocity streams
• Microlensing constraints on the Galactic Bulge Initial Mass Function
• Constraining Spiral Structure Parameters through Galactic Pencil-beam and Large-scale Radial Velocity Surveys
• Shape and orientation of stellar velocity ellipsoids in spiral galaxies
• Peculiarities in the stellar velocity distribution of galaxies with a two-armed spiral structure