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arXiv · 0908.1109

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

Christian D. Howard·R. Michael Rich·Will Clarkson·Ryan Mallery·John Kormendy·Roberto De Propris·Annie C. Robin·Roger Fux·David B. Reitzel·HongSheng Zhao·Konrad Kuijken·Andreas Koch
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Abstract

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.

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Christian D. Howard, R. Michael Rich, Will Clarkson, Ryan Mallery, John Kormendy, Roberto De Propris, Annie C. Robin, Roger Fux, David B. Reitzel, HongSheng Zhao, Konrad Kuijken, Andreas Koch. 2009-08-27. Kinematics at the Edge of the Galactic Bulge: Evidence for Cylindrical Rotation. https://doi.org/10.1088/0004-637x/702/2/l153

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