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J/ApJ/692/1464              Spectroscopy of Segue 1                (Geha+, 2009)

The least-luminous galaxy: spectroscopy of the Milky Way satellite Segue 1. Geha M., Willman B., Simon J.D., Strigari L.E., Kirby E.N., Law D.R., Strader J. <Astrophys. J., 692, 1464-1475 (2009)> =2009ApJ...692.1464G
ADC_Keywords: Galaxies, nearby ; Photometry, SDSS ; Radial velocities Keywords: galaxies: dwarf - galaxies: individual (Segue 1) - galaxies: kinematics and dynamics - Local Group Abstract: We present Keck/DEIMOS spectroscopy of Segue 1, an ultra-low-luminosity (MV=-1.5+0.6-0.8) Milky Way satellite companion. While the combined size and luminosity of Segue 1 are consistent with either a globular cluster or a dwarf galaxy, we present spectroscopic evidence that this object is a dark matter-dominated dwarf galaxy. We identify 24 stars as members of Segue 1 with a mean heliocentric recession velocity of 206±1.3km/s. Although Segue 1 spatially overlaps the leading arm of the Sagittarius stream, its velocity is 100km/s different from that predicted for recent Sagittarius tidal debris at this position. Using spectral synthesis modeling, we derive a metallicity for the single red giant branch star in our sample of [Fe/H]=-3.3±0.2dex. We conclude that Segue 1 is the least luminous of the ultra-faint galaxies recently discovered around the Milky Way, and is thus the least-luminous known galaxy. Description: Targets were selected for spectroscopy based on gri photometry of Segue 1 from the SDSS DR6 public database. One multislit mask was observed for Segue 1 using the Keck II 10m telescope and the DEIMOS spectrograph on the night of 2007 November 12. The mask was observed for a total of 5400s through the 1200 line/mm grating covering a wavelength region 6400-9100Å and the resulting spectral resolution is 1.37Å (FWHM). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 82 51 Keck/DEIMOS velocity measurements for stars in Segue 1 sample
See also: II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009) J/ApJS/191/352 : Abundances in stars of Milky Way dwarf satellites (Kirby+, 2010) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 21 A21 --- Mm Sample type (members/non-members) 23- 29 I07 --- ID SDSS-DR6 source identification (the last seven digits of "ObjId" identifying the object) 31- 32 I2 h RAh Hour of Right Ascension (J2000) 34- 35 I2 min RAm Minute of Right Ascension (J2000) 37- 40 F4.1 s RAs Second of Right Ascension (J2000) 42 A1 --- DE- Sign of the Declination (J2000) 43- 44 I2 deg DEd Degree of Declination (J2000) 46- 47 I2 arcmin DEm Arcminute of Declination (J2000) 49- 52 F4.1 arcsec DEs Arcsecond of Declination (J2000) 54- 57 F4.1 mag gmag SDSS-DR6 g band magnitude 59- 63 F5.2 mag g-r SDSS-DR6 (g-r) color index 65- 70 F6.1 km/s HRV Heliocentric radial velocity (1) 72- 75 F4.1 km/s e_HRV Error in HRV 77- 82 F6.1 km/s Vgsr Galactocentric velocity (1)
Note (1): Radial velocities were measured by cross-correlating the observed science spectra with a set of high signal-to-noise stellar templates. The method is the same as that described in Simon & Geha, 2007ApJ...670..313S. We apply both a telluric and heliocentric correction to all velocities. See section 2.3 for further details.
History: From electronic version of the journal References: Simon & Geha. The Kinematics of the Ultra-faint Milky Way Satellites: Solving the Missing Satellite Problem. 2007ApJ...670..313S
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 07-Mar-2011
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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