J/ApJ/697/207 Cold stellar stream orbit fit (Willett+, 2009)
An orbit fit for the Grillmair Dionatos cold stellar stream.
Willett B.A., Newberg H.J., Zhang H., Yanny B., Beers T.C.
<Astrophys. J., 697, 207-223 (2009)>
=2009ApJ...697..207W 2009ApJ...697..207W
ADC_Keywords: Abundances, [Fe/H] ; Radial velocities ; Surveys ; Stars, halo ;
Proper motions
Keywords: Galaxy: kinematics and dynamics - Galaxy: structure
Abstract:
We use velocity and metallicity information from Sloan Digital Sky
Survey and Sloan Extension for Galactic Understanding and Exploration
stellar spectroscopy to fit an orbit to the narrow 63° stellar
stream of Grillmair and Dionatos (GD; 2006ApJ...643L..17G 2006ApJ...643L..17G). The stars
in the stream have a retrograde orbit with eccentricity e=0.33
(perigalacticon of 14.4kpc and apogalacticon of 28.7kpc) and
inclination approximately i∼35°. In the region of the orbit which
is detected, it has a distance of about 7-11kpc from the Sun. Assuming
a standard disk plus bulge and logarithmic halo potential for the
Milky Way stars plus dark matter, the stream stars are moving with a
large space velocity of approximately 276km/s at perigalacticon. Using
this stream alone, we are unable to determine if the dark matter halo
is oblate or prolate. The metallicity of the stream is
[Fe/H]=-2.1±0.1. Observed proper motions for individual stream
members above the main sequence turnoff are consistent with the
derived orbit. None of the known globular clusters in the Milky Way
have positions, radial velocities, and metallicities that are
consistent with being the progenitor of the GD-1 stream.
Description:
In this work, we utilize newly available Sloan Extension for Galactic
Understanding and Exploration (SEGUE; see Yanny et al.
2009AJ....137.4377Y 2009AJ....137.4377Y) spectroscopy of stars identified along the
stream, that are available in the SDSS Data Release 7 (DR7), to
constrain the orbit of the stream and search for possible progenitors.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 123 48 Spectra of GD-1 stream candidates
--------------------------------------------------------------------------------
See also:
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
J/ApJ/692/1464 : Spectroscopy of Segue 1 (Geha+, 2009)
J/MNRAS/397/1748 : Spectroscopic study of Segue 2 (Belokurov+, 2009)
http://www.sdss.org/ : SDSS home page
http://segue.uchicago.edu/ : SEGUE home page
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Plate SDSS plate number
5 A1 --- --- [-]
6- 10 I5 --- MJD SDSS Modified Julian Date
11 A1 --- --- [-]
12- 14 I3 --- Fiber SDSS fiber number
16 I1 --- Reg Stream Detection Region Number
18- 27 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000)
29- 37 F9.6 deg DEdeg Declination in decimal degrees (J2000)
39- 45 F7.3 deg Glon Galactic longitude
47- 52 F6.3 deg Glat Galactic latitude
54- 59 F6.1 km/s Vgsr Galactic standard of rest velocity (1)
61- 64 F4.1 km/s e_Vgsr Error in Vgsr
66- 71 F6.1 km/s RV Heliocentric radial velocity
73- 78 F6.3 mag gmag Dereddened g band magnitude
80- 84 F5.3 mag u-g Dereddened (u-g) color index
86- 91 F6.3 mag g-r Dereddened (g-r) color index
93- 97 F5.2 [Sun] [Fe/H] Metallicity
99-102 F4.2 [Sun] e_[Fe/H] Error in [Fe/H]
104-107 F4.2 [cm/s2] log(g) Log of the surface gravity
109-112 F4.2 [cm/s2] e_log(g) Error in log(g)
114-117 F4.1 mas/yr pmGlon Proper motion along galactic longitude
119-123 F5.1 mas/yr pmGlat Proper motion along galactic latitude
--------------------------------------------------------------------------------
Note (1): Vgsr is computed from RV with the formula:
Vgsr = RV + 10.1 cos(b)cos(l) + 224 cos(b)sin(l)+ 6.7 sin(b),
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 18-May-2011