J/ApJ/731/119 BHB candidates in Sagittarius stream (Ruhland+, 2011)
The structure of the Sagittarius stellar stream as traced by blue horizontal
branch stars.
Ruhland C., Bell E.F., Rix H.-W., Xue X.-X.
<Astrophys. J., 731, 119 (2011)>
=2011ApJ...731..119R 2011ApJ...731..119R
ADC_Keywords: Stars, horizontal branch ; Radial velocities ; Photometry, SDSS ;
Abundances, [Fe/H]
Keywords: galaxies: dwarf - galaxies: interactions - Galaxy: halo -
Galaxy: stellar content
Abstract:
We use a sample of blue horizontal branch (BHB) stars from the Sloan
Digital Sky Survey Data Release 7 (Cat. II/294) to explore the
structure of the tidal tails from the Sagittarius Dwarf Galaxy. We use
a method yielding BHB star candidates with up to ∼70% purity from
photometry alone. The resulting sample has a distance precision of
roughly 5% and can probe distances in excess of 100kpc. Using this
sample, we identify a possible extension to the trailing arm at
distances of 60-80kpc from the Sun with an estimated significance of
at least 3.8σ. Current models predict that a distant "returning"
segment of the debris stream should exist, but place it substantially
closer to the Sun where no debris is observed in our data. Exploiting
the distance precision of our tracers, we estimate the mean
line-of-sight thickness of the leading arm to be ∼3kpc, and show that
the two "bifurcated" branches of the debris stream differ by only
1-2kpc in distance. With a spectroscopic very pure BHB star subsample,
we estimate the velocity dispersion in the leading arm, 37km/s, which
is in reasonable agreement with models of Sgr disruption. We finally
present a sample of high-probability Sgr BHB stars in the leading arm
of Sgr, selected to have distances and velocities consistent with Sgr
membership, to allow further study.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table5.dat 94 70 Sample selected for a high probability of
association with Sagittarius
--------------------------------------------------------------------------------
See also:
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
J/A+A/522/A88 : Photometric identification of BHB stars (Smith+, 2010)
J/ApJ/684/1143 : BHB candidates in the Milky Way (Xue+, 2008)
J/AJ/130/1097 : BHB stars in Century Survey Galactic Halo Project (Brown+,
2005)
J/AJ/127/899 : Blue HB stars in SDSS (Sirko+, 2004)
J/AJ/128/245 : M giant stars in the Sgr dwarf galaxy (Majewski+, 2004)
J/ApJ/588/824 : Velocities of blue stars near (l,b)=(198,-27) (Yanny+, 2003)
J/AJ/117/2308 : Spectroscopy of hot stars in the halo (Wilhelm+, 1999)
J/AJ/109/1086 : VI Photometry in M54 and Sgr Dwarf Galaxy (Sarajedini+ 1995)
J/AJ/108/1722 : Blue horizontal branch stars (Kinman+ 1994)
http://www.sdss.org/ : SDSS home page
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 F10.6 deg RAdeg Right ascension (J2000)
12- 22 F11.8 deg DEdeg Declination (J2000)
24- 32 F9.5 deg GLON Galactic longitude
34- 42 F9.6 deg GLAT Galactic latitude
44- 48 F5.2 mag gmag [17/20] SDSS-DR7 g-band magnitude
50- 53 F4.2 mag u-g u-g color index
55- 59 F5.2 mag g-r g-r color index
61- 64 F4.2 --- Pbhb [0/1] BHB probability
66- 70 F5.1 km/s HRV [-83/74] Heliocentric radial velocity (1)
72- 75 F4.1 km/s e_HRV [3/24] HRV uncertainty
77- 82 F6.1 km/s RVgal [-109/55] Radial velocity in the Galactic
standard of rest (1)
84- 88 F5.1 [Sun] Fe/H [-2.4/-1]?=-10 Metallicity
90- 94 F5.1 [Sun] e_Fe/H [0/1.1]?=-10 Fe/H uncertainty
--------------------------------------------------------------------------------
Note (1): Throughout the paper, the radial velocities are given in the
Galactic standard of rest, which are the heliocentric radial
velocities corrected for the Galactic rotation assuming a rotation
velocity of 220km/s for the local standard of rest and (+10.0, +5.2,
+7.2) km/s for the solar motion where the directions are defined as
pointing toward the Galactic center, in the direction of rotation and
toward the north Galactic Pole (see Xue et al. 2008, Cat.
J/ApJ/684/1143, for details).
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 23-May-2013