Kinematics at the Edge of the Galactic Bulge: Evidence for Cylindrical Rotation

Christian howard, R. Michael Rich, Will Clarkson, Ryan Mallery, John Kormendy, Roberto De Propris, Annie robin, Roger Fux, David reitzel, HongSheng Zhao, Konrad Kuijken, Andreas Koch

Research output: Contribution to journalArticlepeer-review

81 Citations (Scopus)


We present new results from BRAVA, a large scale radial velocity survey of the Galactic bulge, using M giant stars selected from the Two Micron All Sky Survey catalogue as targets for the Cerro Tololo Inter-American Observatory 4m Hydra multi-object spectrograph. The purpose of this survey is to construct a new generation of self-consistent bar models that conform to these observations. We report the dynamics for fields at the edge of the Galactic bulge at latitudes b=-8 deg. and compare to the dynamics at b=-4 deg. We find that the rotation curve V(r) is the same at b=-8 deg. as at b=-4 deg. That is, the Galactic boxy bulge rotates cylindrically, as do boxy bulges of other galaxies. The summed line of sight velocity distribution at b=-8 deg. is Gaussian, and the binned longitude-velocity plot shows no evidence for either a (disk) population with cold dynamics or for a (classical bulge) population with hot dynamics. The observed kinematics are well modeled by an edge-on N-body bar, in agreement with published structural evidence. Our kinematic observations indicate that the Galactic bulge is a prototypical product of secular evolution in galaxy disks, in contrast with stellar population results that are most easily understood if major mergers were the dominant formation process.
Original languageEnglish
Pages (from-to)L153-L157
JournalAstrophysical Journal Letters
Issue number2
Publication statusPublished - 10 Sept 2009


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