J/ApJ/813/89 Radial velocities of Milky Way inner halo stars (King+, 2015)
Stellar velocity dispersion and anisotropy of the Milky Way inner halo.
King III C., Brown W.R., Geller M.J., Kenyon S.J.
<Astrophys. J., 813, 89 (2015)>
=2015ApJ...813...89K 2015ApJ...813...89K (SIMBAD/NED BibCode)
ADC_Keywords: Radial velocities ; Stars, F-type ; Stars, halo ;
Photometry, SDSS ; Milky Way
Keywords: Galaxy: formation; Galaxy: fundamental parameters; Galaxy: halo;
Galaxy: kinematics and dynamics; Galaxy: structure;
stars: Population II
Abstract:
We measure the three components of velocity dispersion, σR,
σθ, σφ, for stars within 6<R<30kpc of the
Milky Way using a new radial velocity sample from the MMT telescope.
We combine our measurements with previously published data so that we
can more finely sample the stellar halo. We use a maximum likelihood
statistical method for estimating mean velocities, dispersions, and
covariances assuming only that velocities are normally distributed.
The alignment of the velocity ellipsoid is consistent with a
spherically symmetric gravitational potential. From the spherical
Jeans equation, the mass of the Milky Way is
M(R≤12kpc)=1.3x1011M☉ with an uncertainty of 40%. We also
find a region of discontinuity, 15≲R≲25kpc, where the estimated
velocity dispersions and anisotropies diverge from their anticipated
values, confirming the break observed by others. We argue that this
break in anisotropy is physically explained by coherent stellar
velocity structure in the halo, such as the Sgr stream. To
significantly improve our understanding of halo kinematics will
require combining radial velocities with future Gaia proper motions.
Description:
All observations with Hectospec on the 6.5m MMT telescope are made
with the 270line/mm grating, which provides a spectral resolution of
5Å over the spectral range 3700-9100Å. We acquired 3197 spectra
between 2004 April and 2005 July, the first year of Hectospec
operations, with a dedicated halo star observing program. We acquired
an additional 8143 spectra between 2009 January and 2015 July with a
parallel Hectospec observing program.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 69 6174 Hectospec F stars
--------------------------------------------------------------------------------
See also:
J/A+A/568/A7 : Model SDSS colors for halo stars (Allende Prieto+, 2014)
J/AJ/146/21 : LINEAR. II. Catalog of RR Lyrae stars (Sesar+, 2013)
J/ApJ/751/55 : MMT hypervelocity star survey. II. (Brown+, 2012)
J/ApJ/738/79 : SDSS-DR8 BHB stars in the Milky Way's halo (Xue+, 2011)
J/ApJ/731/4 : Galactic halo as seen by the CFHTLS (Sesar+, 2011)
J/AJ/139/59 : Milky Way halo velocity dispersion profile (Brown+, 2010)
J/MNRAS/398/1757 : RR Lyraes in SDSS stripe 82 (Watkins+, 2009)
J/ApJ/703/2177 : Metal-poor MS turnoff stars summary (Schlaufman+, 2009)
J/ApJ/684/1143 : BHB candidates in the Milky Way (Xue+, 2008)
J/AJ/136/2070 : SEGUE stellar parameter pipeline. III. (Allende Prieto+, 2008)
J/AJ/135/564 : Photometry and spectroscopy of BHB candidates (Brown+, 2008)
J/AJ/130/1097 : Century Survey Galactic Halo Project BHB stars (Brown+, 2005)
Byte-by-byte Description of file: table2.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 F6.1 km/s HRV [-515/448] Heliocentric radial velocity
34- 37 F4.1 km/s e_HRV [1/54] Uncertainty in HRV
39- 44 F6.3 mag rmag0 [14.9/21.2] SDSS DR10 de-reddened r-band
magnitude
46- 50 F5.3 mag e_rmag0 [0.008/4] Uncertainty in rmag
52- 56 F5.3 mag rMag [0.9/7] Absolute r band magnitude estimate
58- 62 F5.2 kpc R [5.5/68.2] Galactocentric radial distance (1)
64- 69 F6.2 kpc Z [-51.1/46.5] Galactocentric vertical distance (1)
--------------------------------------------------------------------------------
Note (1): Calculated assuming the Sun is at R=8kpc.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 15-Feb-2016