J/AJ/139/59 Milky Way halo velocity dispersion profile (Brown+, 2010)
Velocity dispersion profile of the Milky Way halo. Brown W.R., Geller M.J., Kenyon S.J., Diaferio A. <Astron. J., 139, 59-67 (2010)> =2010AJ....139...59B
ADC_Keywords: Milky Way ; Stars, early-type ; Photometry, SDSS ; Radial velocities Keywords: Galaxy: halo - Galaxy: kinematics and dynamics Abstract: We present a spectroscopic sample of 910 distant halo stars from the Hypervelocity Star survey from which we derive the velocity dispersion profile of the Milky Way halo. The sample is a mix of 74% evolved horizontal branch stars and 26% blue stragglers. We estimate distances to the stars using observed colors, metallicities, and stellar evolution tracks. Our sample contains twice as many objects with R>50kpc as previous surveys. We compute the velocity dispersion profile in two ways: with a parametric method based on a Milky Way potential model and with a non-parametric method based on the caustic technique originally developed to measure galaxy cluster mass profiles. The resulting velocity dispersion profiles are remarkably consistent with those found by two independent surveys based on other stellar populations: the Milky Way halo exhibits a mean decline in radial velocity dispersion of -0.38±0.12km/s/kpc over 15<R<75kpc. This measurement is a useful basis for calculating the total mass and mass distribution of the Milky Way halo. Description: The HVS program is a radial velocity survey of stars selected with the colors of late-B-type stars. The radial velocity survey is now 93% complete over 7300deg2 of the SDSS DR6 imaging footprint. Here, we focus exclusively on the stars with late-B and early-A spectral types. The data set contains 910 stars: 571 stars from the original HVS survey (HyperVelocity star; Brown et al., 2007, Cat. J/ApJ/671/1708), 331 stars from the new HVS survey (Brown et al., 2009ApJ...690.1639B), and 8 BHB stars from the earliest sample (Brown et al., 2005ApJ...622L..33B). All photometry comes from SDSS Data Release 6. We obtained spectroscopic observations at the 6.5m MMT telescope with the Blue Channel Spectrograph. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 133 910 Velocity, SDSS photometry and absolute magnitudes of the HVS (HyperVelocity Star) program.
See also: J/ApJ/671/1708 : Hypervelocity stars. III (Brown+, 2007) http://www.sdss.org : SDSS Home Page Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 2 I2 h RAh Hour of Right Ascension (J2000) 4- 5 I2 min RAm Minute of Right Ascension (J2000) 7- 12 F6.3 s RAs Second of Right Ascension (J2000) 14 A1 --- DE- Sign of the Declination (J2000) 15- 16 I2 deg DEd Degree of Declination (J2000) 18- 19 I2 arcmin DEm Arcminute of Declination (J2000) 21- 25 F5.2 arcsec DEs Arcsecond of Declination (J2000) 27- 32 F6.3 mag g0mag Dereddened SDSS g band magnitude 34- 38 F5.3 mag e_g0mag The 1σ error in g0mag 40- 44 F5.3 mag (u-g)0 Dereddened SDSS (u-g) color 46- 50 F5.3 mag e_(u-g)0 The 1σ error in (u-g)0 52- 57 F6.3 mag (g-r)0 Dereddened SDSS (g-r) color 59- 63 F5.3 mag e_(g-r)0 The 1σ error in (g-r)0 65- 70 F6.1 km/s HRV Heliocentric radial velocity 72- 75 F4.1 km/s e_HRV The 1σ error in HRV 77- 83 F7.3 deg GLON Galactic longitude 85- 91 F7.3 deg GLAT Galactic latitude 93- 98 F6.1 km/s Vrf Velocity in the Galactocentric rest frame (1) 100-103 F4.2 mag gBHB Absolute g band magnitude for a BHB (2) 105-108 F4.2 mag e_gBHB The 1σ error in gBHB 110-113 F4.1 kpc RBHB Galactocentric distance if BHB 115-118 F4.2 mag gBS Absolute BS g band magnitude (3) 120-123 F4.2 mag e_gBS The 1σ error in gBS 125-128 F4.1 kpc RBS Galactocentric distance if BS 130-133 F4.2 --- fBHB Likelihood of being BHB (4)
Note (1): as defined in Equation 1: Vrf=HV+220sin(l)cos(b)+(10cos(l)cos(b)+5.2sin(l)cos(b)+2sin(b)) Note (2): absolute magnitude Mg of a blue horizontal branch star, derived from Dotter et al. (2008ApJS..178...89D) for [Fe/H]=-1.9. Note (3): absolute magnitude Mg of a blue straggler, derived from Girardi et al. (2004A&A...422..205G) for [Fe/H]=-1.9. Note (4): Based on stellar colors and spectra.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 24-Mar-2012
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