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Galactic Center: Improved Relative Astrometry for Velocities, Accelerations, and Orbits near the Supermassive Black Hole

Jia, Siyao and Lu, Jessica R. and Sakai, S. and Gautam, A. K. and Do, T. and Hosek, M. W., Jr. and Service, M. and Ghez, A. M. and Gallego-Cano, E. and Schödel, R. and Hees, Aurelien and Morris, M. R. and Becklin, E. and Matthews, K. (2019) Galactic Center: Improved Relative Astrometry for Velocities, Accelerations, and Orbits near the Supermassive Black Hole. Astrophysical Journal, 873 (1). Art. No. 9. ISSN 1538-4357. doi:10.3847/1538-4357/ab01de.

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We present improved relative astrometry for stars within the central half parsec of our Galactic Center (GC) based on data obtained with the 10 m W. M. Keck Observatory from 1995 to 2017. The new methods used to improve the astrometric precision and accuracy include correcting for local astrometric distortions, applying a magnitude-dependent additive error, and more carefully removing instances of stellar confusion. Additionally, we adopt jackknife methods to calculate velocity and acceleration uncertainties. The resulting median proper motion uncertainty is 0.05 mas yr^(−1) for our complete sample of 1184 stars in the central 10'' (0.4 pc). We have detected 24 accelerating sources, 2.6 times more than the number of previously published accelerating sources, which extend out to 4'' (0.16 pc) from the black hole. Based on S0-2's orbit, our new astrometric analysis has reduced the systematic error of the supermassive black hole (SMBH) by a factor of 2. The linear drift in our astrometric reference frame is also reduced in the north–south direction by a factor of 4. We also find the first potential astrometric binary candidate S0-27 in the GC. These astrometric improvements provide a foundation for future studies of the origin and dynamics of the young stars around the SMBH, the structure and dynamics of the old nuclear star cluster, the SMBH's properties derived from orbits, and tests of general relativity in a strong gravitational field.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Jia, Siyao0000-0001-5341-0765
Lu, Jessica R.0000-0001-9611-0009
Sakai, S.0000-0001-5972-663X
Gautam, A. K.0000-0002-2836-117X
Do, T.0000-0001-9554-6062
Hosek, M. W., Jr.0000-0003-2874-1196
Ghez, A. M.0000-0003-3230-5055
Gallego-Cano, E.0000-0002-7452-1496
Hees, Aurelien0000-0002-2186-644X
Morris, M. R.0000-0002-6753-2066
Additional Information:© 2019 The American Astronomical Society. Received 2018 October 12; revised 2019 January 15; accepted 2019 January 23; published 2019 February 27. We thank the staff of the Keck Observatory, especially Randy Campbell, Jason Chin, Scott Dahm, Heather Hershey, Carolyn Jordan, Marc Kassis, Jim Lyke, Gary Puniwai, Julie Renaud-Kim, Luca Rizzi, Terry Stickel, Hien Tran, Peter Wizinowich, Carlos Alvarez, Greg Doppman, and current and former directors Hilton Lewis and Taft Armandroff for all their help in obtaining observations. We acknowledge support from the W. M. Keck Foundation, the Heising Simons Foundation, and the National Science Foundation (AST-1412615, AST-1518273). The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007–2013)/ERC grant agreement No. [614922]. 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 wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Facility: Keck II (NIRC2) - . Software: AstroPy (Astropy Collaboration 2013), Matplotlib (Hunter 2007), SciPy (Eric et al. 2001).
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Heising Simons FoundationUNSPECIFIED
European Research Council (ERC)614922
Subject Keywords:astrometry – Galaxy: center – proper motions – techniques: high angular resolution – infrared: stars – stars: black holes
Issue or Number:1
Record Number:CaltechAUTHORS:20190227-090306554
Persistent URL:
Official Citation:Siyao Jia et al 2019 ApJ 873 9
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:93290
Deposited By: Tony Diaz
Deposited On:27 Feb 2019 17:10
Last Modified:16 Nov 2021 16:56

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