期刊
ASTROPHYSICAL JOURNAL
卷 721, 期 2, 页码 1142-1157出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/721/2/1142
关键词
binaries: spectroscopic; galaxies: kinematics and dynamics
资金
- NSF [AST-0607746]
- NASA [NNX09AD09G]
- NASA [NNX09AD09G, 120339] Funding Source: Federal RePORTER
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.
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