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Published March 10, 2014 | Published + Submitted
Journal Article Open

Properties of the Remnant Clockwise Disk of Young Stars in the Galactic Center

Abstract

We present new kinematic measurements and modeling of a sample of 116 young stars in the central parsec of the Galaxy in order to investigate the properties of the young stellar disk. The measurements were derived from a combination of speckle and laser guide star adaptive optics imaging and integral field spectroscopy from the Keck telescopes. Compared to earlier disk studies, the most important kinematic measurement improvement is in the precision of the accelerations in the plane of the sky, which have a factor of six smaller uncertainties (σ ~ 10 μas yr^(–2)). We have also added the first radial velocity measurements for eight young stars, increasing the sample at the largest radii (6''-12'') by 25%. We derive the ensemble properties of the observed stars using Monte Carlo simulations of mock data. There is one highly significant kinematic feature (~20σ), corresponding to the well-known clockwise disk, and no significant feature is detected at the location of the previously claimed counterclockwise disk. The true disk fraction is estimated to be ~20%, a factor of ~2.5 lower than previous claims, suggesting that we may be observing the remnant of what used to be a more densely populated stellar disk. The similarity in the kinematic properties of the B stars and the O/WR stars suggests a common star formation event. The intrinsic eccentricity distribution of the disk stars is unimodal, with an average value of 〈e〉 = 0.27 ± 0.07, which we show can be achieved through dynamical relaxation in an initially circular disk with a moderately top-heavy mass function.

Additional Information

© 2014 The American Astronomical Society. Received 2013 June 17; accepted 2014 January 30; published 2014 February 24. Support for this work was provided by the NSF grant AST-0909218. The authors thank the referee for useful comments that helped improve the paper. We are also grateful to Eric Becklin for the many helpful discussions about the project and to Brad Hansen for suggestions on the disk simulations. We thank Richard Alexander for generously providing updated eccentricity values from dynamical evolution models of the GC young stars. We thank the staff of the Keck Observatory for their help in obtaining the observations. S.Y. thanks the Aspen Center for Physics and the organizers of the summer 2012 workshop, as well as Ann-Marie Madigan for insightful discussions. The W. M. Keck Observatory is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors also recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

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Published - 0004-637X_783_2_131.pdf

Submitted - 1401.7354v1.pdf

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August 22, 2023
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