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J/ApJ/733/46           Velocity measurements in Segue 1           (Simon+, 2011)

A complete spectroscopic survey of the Milky Way satellite Segue 1: the darkest galaxy. Simon J.D., Geha M., Minor Q.E., Martinez G.D., Kirby E.N., Bullock J.S., Kaplinghat M., Strigari L.E., Willman B., Choi P.I., Tollerud E.J., Wolf J. <Astrophys. J., 733, 46 (2011)> =2011ApJ...733...46S
ADC_Keywords: Galaxies, nearby ; Stars, normal ; Radial velocities ; Equivalent widths ; Photometry, SDSS ; Spectroscopy Keywords: dark matter - galaxies: dwarf - galaxies: individual (Segue 1) - galaxies: kinematics and dynamics - Local Group Abstract: We present the results of a comprehensive Keck/DEIMOS spectroscopic survey of the ultra-faint Milky Way satellite galaxy Segue 1. We have obtained velocity measurements for 98.2% of the stars within 67pc (10', or 2.3 half-light radii) of the center of Segue 1 that have colors and magnitudes consistent with membership, down to a magnitude limit of r=21.7. Based on photometric, kinematic, and metallicity information, we identify 71 stars as probable Segue 1 members, including some as far out as 87pc. After correcting for the influence of binary stars using repeated velocity measurements, we determine a velocity dispersion of 3.7+1.4-1.1km/s. The mass within the half-light radius is 5.8+8.2-3.1x105M. The stellar kinematics of Segue 1 require very high mass-to-light ratios unless the system is far from dynamical equilibrium, even if the period distribution of unresolved binary stars is skewed toward implausibly short periods. With a total luminosity less than that of a single bright red giant and a V-band mass-to-light ratio of 3400M/L, Segue 1 is the darkest galaxy currently known. Description: We observed 12 new slit masks, including at least one slit placed on each of the 112 candidate member stars (plus repeat observations of 18 of the 24 members from Geha et al., 2009, Cat. J/ApJ/692/1464), with the DEIMOS spectrograph on the Keck II telescope. The observations took place on the nights of 2009 February 18, 26, and 27 and 2010 February 12 and 13. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3.dat 94 522 Velocity measurements in Segue 1
See also: II/306 : The SDSS Photometric Catalog, Release 8 (Adelman-McCarthy+, 2011) J/ApJ/723/1632 : Abundance spreads in Bootes I and Segue 1 (Norris+, 2010) J/ApJ/692/1464 : Spectroscopy of Segue 1 (Geha+, 2009) Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 4 A4 --- --- [SDSS] 5- 23 A19 --- SDSS SDSS-DR5 identification ( 25- 30 F6.1 km/s Vel [-180.2/394.9] Heliocentric velocity 32- 35 F4.1 km/s e_Vel [2.2/37.8] Uncertainty in Vel 37- 40 F4.1 0.1nm EW Weighted sum of CaT line equivalent widths (1) 42- 45 F4.1 0.1nm e_EW ?=-9.9 Uncertainty in EW (1) 47- 50 F4.1 arcmin Rad [0/17.8] Radial distance from Segue 1 52- 60 F9.3 d MJD [54416.5/55240.5] Modified Julian Date of observation 62- 66 F5.2 mag gmag ? SDSS-DR5 g band magnitude 68- 72 F5.2 mag rmag ? SDSS-DR5 r band magnitude 74- 78 F5.2 mag imag [13.22/22]? SDSS-DR5 i band magnitude 80 I1 --- Mm [0/1]? Member status (0=no, 1=member) (2) 82- 87 F6.3 --- EMpr [0/1]? Member probability from the EM (Expectation Maximization) algorithm (3) 89- 94 F6.3 --- Bpr [0/1]? Bayesian member probability (4)
Note (1): Where EW=0.5*EW8498+1.0*EW8542+0.6*EW8662. For a few stars our spectra did not cover any of the CaT lines, so we did not measure the EW (their velocities were determined with other features). These objects are listed with equivalent widths of -9.9. Note (2): According to the criteria established at the beginning of Section 3.1. 1 = member; 0 = non-member. Note (3): The algorithm is run on the subset of stars whose colors and magnitudes are consistent with membership, so photometric non-members are indicated by probability -9.999. Note (4): From the Bayesian approach. As with the EM algorithm, these calculations are run on the subset of stars whose colors and magnitudes are consistent with membership, so photometric non-members are indicated by probability -9.999.
History: From electronic version of the journal References: Martinez et al. Paper II. 2011ApJ...738...55M
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 06-Nov-2012
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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