2010/01/11 by Quinn E. Minor, Gregory D. Martinez, Greg Martinez +5 · 3 citations
Mathematics · Physics and Astronomy · #Angular momentum #Astronomy and Astrophysical Research #Astrophysics #Binary number #Binary star #Classical mechanics #Dispersion (optics) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Mathematics #Optics #Orbital elements #Orbital motion #Physics #Radial velocity #Stars #Stellar, planetary, and galactic studies #Velocity dispersion #astro-ph.CO #astro-ph.GA
paper · pdf · doi:10.1088/0004-637x/721/2/1142
arxiv created 2010/01/11 · openalex publication_date 2010/09/08 · arxiv updated 2015/05/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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.