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Ionized gas dynamics in the inner 2 pc of Sgr A West

Published online by Cambridge University Press:  22 May 2014

John H. Lacy ,
Wesley T. Irons  and
Matthew J. Richter
John H. Lacy
Affiliation:
Department of Astronomy, University of Texas, Austin, TX, USA email: [email protected]
Wesley T. Irons
Affiliation:
Dept. of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, USA email: [email protected]
Matthew J. Richter
Affiliation:
Department of Physics, University of California, Davis, CA, USA email: [email protected]
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Abstract

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We present a data cube of the [NeII] (12.8 μm) emission from the inner 2 pc of Sgr A West with 1″ and 4 km s−1 resolution, and with substantially better SNR and velocity resolution than previous observations of the ionized gas. We compare the observations to two proposed models of the gas motions and distribution: flows along tidally stretched streamers, and more nearly circular motions with density wave compression. The density wave model provides a considerably better fit to the kinematics of the northern arm and western arc. Neither model fits the eastern arm and bar kinematics well.

To help understand the origin of the spiral pattern we calculated orbits in the potential of a black hole in a star cluster and find that the orbits naturally evolve to set up a one-armed spiral wave very similar to that observed, both spatially and kinematically. Magnetic or other perturbing forces may influence the formation of the spiral wave, but self gravity is not required. Because a density wave evolves on the orbit precession timescale, rather than the orbital timescale, a wave pattern should persist for several 105 yr. No net inward motion of the gas is required by the model. If there is inflow, it is much smaller than is suggested by the infalling streamer model.

Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 9 , Symposium S303: The Galactic Center: Feeding and Feedback in a Normal Galactic Nucleus , October 2013 , pp. 69 - 72
Copyright
Copyright © International Astronomical Union 2014 

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