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Correcting Velocity Dispersions of Dwarf Spheroidal Galaxies for Binary Orbital Motion

Minor, Quinn E. and Martinez, Greg and Bullock, James and Kaplinghat, Manoj and Trainor, Ryan (2010) Correcting Velocity Dispersions of Dwarf Spheroidal Galaxies for Binary Orbital Motion. Astrophysical Journal, 721 (2). pp. 1142-1157. ISSN 0004-637X.

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We show that the measured velocity dispersions of dwarf spheroidal galaxies from about 4 to 10 km s^(–1) are unlikely to be inflated by more than 30% due to the orbital motion of binary stars and demonstrate that the intrinsic velocity dispersions can be determined to within a few percent accuracy using two-epoch observations with 1-2 yr as the optimal time interval. The crucial observable is the threshold fraction—the fraction of stars that show velocity changes larger than a given threshold between measurements. The threshold fraction is tightly correlated with the dispersion introduced by binaries, independent of the underlying binary fraction and distribution of orbital parameters. We outline a simple procedure to correct the velocity dispersion to within a few percent accuracy by using the threshold fraction and provide fitting functions for this method. We also develop a methodology for constraining properties of binary populations from both single- and two-epoch velocity measurements by including the binary velocity distribution in a Bayesian analysis.

Item Type:Article
Related URLs:
URLURL TypeDescription
Martinez, Greg0000-0002-7476-2521
Bullock, James0000-0003-4298-5082
Trainor, Ryan0000-0002-6967-7322
Additional Information:© 2010 The American Astronomical Society. Received 2010 March 8; accepted 2010 June 4; published 2010 September 8. We thank Erik Tollerud for providing valuable feedback and many illuminating discussions throughout the course of this project. This work was supported in part by NSF grant AST- 0607746 and NASA grant NNX09AD09G.
Funding AgencyGrant Number
Subject Keywords:binaries: spectroscopic – galaxies: kinematics and dynamics
Issue or Number:2
Classification Code:PACS: 98.52.Wz; 98.62.Ve; 98.62.Dm; 98.62.Lv
Record Number:CaltechAUTHORS:20101022-094020218
Persistent URL:
Official Citation:Quinn E. Minor et al 2010 ApJ 721 1142. doi: 10.1088/0004-637X/721/2/1142
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:20481
Deposited By: Tony Diaz
Deposited On:12 Nov 2010 00:18
Last Modified:13 Nov 2019 19:45

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