The bulge radial velocity assay: Techniques and a rotation curve

R. Michael Rich, David B. Reitzel, Christian D. Howard, Hongsheng Zhao

Research output: Contribution to journalArticlepeer-review

94 Citations (Scopus)

Abstract

We are undertaking a large-scale radial velocity survey of the Galactic bulge that uses M giant stars selected from the Two Micron All Sky Survey catalog as targets for the Cerro Tololo Inter-American Observatory 4 m Hydra multiobject spectrograph. The aim of this survey is to test dynamical models of the bulge and to quantify the importance, if any, of cold stellar streams in the bulge and its vicinity. Here we report on the kinematics of a strip of fields at -10 degrees < l < +10 degrees and b = 4 degrees. We construct a longitude-velocity plot for the bulge stars and the model data and find that, contrary to previous studies, the bulge does not rotate as a solid body. From -5 degrees < l < +5 degrees he rotation curve has a slope of roughly 100 km s(-1) kpc(-1) and flattens considerably at greater l, reaching a maximum rotation of 45 km s(-.) We compare our rotation curve and velocity dispersion profile to both the self-consistent model of Zhao and to N-body models; neither fits both our observed rotation curve and velocity dispersion profile. The high precision of our radial velocities (similar to 3 km s(-1)) yields an unexpected result: hints of cold kinematic features are seen in a number of the line-of-sight velocity distributions.

Original languageEnglish
Pages (from-to)L29-L32
Number of pages4
JournalAstrophysical Journal Letters
Volume658
Issue number1
DOIs
Publication statusPublished - 20 Mar 2007

Keywords

  • galaxy : bulge
  • Galaxy : kinematics and dynamics
  • stars : kinematics
  • stars : late-type
  • techniques : radial velocities
  • MICROLENSING OPTICAL DEPTH
  • GALACTIC BULGE
  • BAADES-WINDOW
  • M-GIANTS
  • K-GIANTS
  • DYNAMICAL MODEL
  • INNER GALAXY
  • KINEMATICS
  • STARS
  • BAR

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