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J/AJ/153/254 Velocities of RGB stars in the Leo II dwarf galaxy (Spencer+, 2017)

The binary fraction of stars in dwarf galaxies: the case of Leo II. Spencer M.E., Mateo M., Walker M.G., Olszewski E.W., McConnachie A.W., Kirby E.N., Koch A. <Astron. J., 153, 254 (2017)> =2017AJ....153..254S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Stars, giant ; Radial velocities Keywords: binaries: general - galaxies: dwarf - galaxies: individual (Leo II) - galaxies: kinematics and dynamics Abstract: We combine precision radial velocity data from four different published works of the stars in the Leo II dwarf spheroidal galaxy. This yields a data set that spans 19 years, has 14 different epochs of observation, and contains 372 unique red giant branch stars, 196 of which have repeat observations. Using this multi-epoch data set, we constrain the binary fraction for Leo II. We generate a suite of Monte Carlo simulations that test different binary fractions using Bayesian analysis and determine that the binary fraction for Leo II ranges from 0.30-0.10+0.09 to 0.34-0.11+0.11, depending on the distributions of binary orbital parameters assumed. This value is smaller than what has been found for the solar neighborhood (∼0.4-0.6) but falls within the wide range of values that have been inferred for other dwarf spheroidals (0.14-0.69). The distribution of orbital periods has the greatest impact on the binary fraction results. If the fraction we find in Leo II is present in low-mass ultra-faints, it can artificially inflate the velocity dispersion of those systems and cause them to appear more dark matter rich than in actuality. For a galaxy with an intrinsic dispersion of 1 km/s and an observational sample of 100 stars, the dispersion can be increased by a factor of 1.5-2 for Leo II-like binary fractions or by a factor of three for binary fractions on the higher end of what has been seen in other dwarf spheroidals. Description: We use radial velocity data from four studies. The first set comprises 31 red giant branch (RGB) stars with a median radial velocity error of 3 km/s (Vogt et al. 1995AJ....109..151V). It contains the first spectroscopic observations of RGB stars in Leo II, and remained the only kinematic data set for over a decade. The second study, by Koch et al. (2007, J/AJ/134/566, hereafter KK07), consists of radial velocities for 171 member stars. KK07 published average velocities taken during three epochs between 2003 and 2004. The third data set comes from Kirby et al. (2010, J/ApJS/191/352). They used Keck/DEIMOS to obtain medium resolution spectroscopy for the purpose of chemical abundance measurements, but also extracted radial velocities to help identify member stars. The fourth and final data set is published in Spencer et al. (2017, J/ApJ/836/202), which contains radial velocities for 175 member stars. Fifty of these have two or more observations, which were taken over the course of eight years with Hectochelle (Szentgyorgyi et al. 1998SPIE.3355..242S) on the Multiple Mirror Telescope. This data set contains five epochs between the years 2006 and 2013. Objects: ------------------------------------------------- RA (ICRS) DE Designation(s) ------------------------------------------------- 11 13 28.13 +22 09 10.1 Leo II = NAME Leo B ------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 66 596 Velocities of RGB stars in Leo II
See also: J/AJ/120/284 : Variables in Leo II dwarf spheroidal (Siegel+, 2000) J/MNRAS/360/185 : VI photometry of the Leo II galaxy (Bellazzini+, 2005) J/AJ/133/270 : Metallicities and ages in Leo II dSph (Koch+, 2007) J/AJ/134/566 : Leo II stellar kinematics (Koch+, 2007) J/MNRAS/378/318 : Chemical abundances in Leo I and II dSph (Bosler+, 2007) J/MNRAS/388/1185 : JHKs photometry of LeoII dSph giants (Gullieuszik+, 2008) J/ApJS/191/352 : Abundances in stars of Milky Way dwarf satellites (Kirby+, 2010) J/ApJ/741/100 : Proper motions of Leo II member stars (Lepine+, 2011) J/ApJ/836/202 : Kinematic study of the Leo II dwarf galaxy (Spencer+, 2017) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 6 A6 --- --- [LeoII-] 7- 9 I3 --- LeoII- [1/196] Stellar identifier (LeoII-NNN) 11 I1 --- Num [2/7] Number of observations 13- 14 I2 h RAh Hour of Right Ascension (J2000) 16- 17 I2 min RAm Minute of Right Ascension (J2000) 19- 23 F5.2 s RAs Second of Right Ascension (J2000) 24 A1 --- DE- Sign of the Declination (J2000) 25- 26 I2 deg DEd Degree of Declination (J2000) 28- 29 I2 arcmin DEm Arcminute of Declination (J2000) 31- 35 F5.2 arcsec DEs Arcsecond of Declination (J2000) 37- 45 F9.1 d HJD Heliocentric Julian Date 47- 52 F6.2 km/s RV [52.4/103.01] Radial velocity (1) 54- 58 F5.2 km/s e_RV [0.54/31.61] Uncertainty in RV 60- 66 A7 --- r_RV Reference for RV (2)
Note (1): Velocities after correcting for systematic offsets. Only stars with multi-epoch velocity measurements are included. Note (2): Reference as follows: Paper I = Spencer et al. (2017, J/ApJ/836/202); KK07 = Koch et al. (2007, J/AJ/134/566); KG10 = Kirby et al. (2010, J/ApJS/191/352); V95 = Vogt et al. (1995AJ....109..151V).
History: From electronic version of the journal References: Spencer et al. Paper I. 2017ApJ...836..202S, Cat. J/ApJ/836/202
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 15-May-2018
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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