2009ApJ...692.1464G


Query : 2009ApJ...692.1464G

2009ApJ...692.1464G - Astrophys. J., 692, 1464-1475 (2009/February-3)

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. and STRADER J.

Abstract (from CDS):

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±1.3 km/s. Although Segue 1 spatially overlaps the leading arm of the Sagittarius stream, its velocity is 100 km/s different from that predicted for recent Sagittarius tidal debris at this position. We measure an internal velocity dispersion of 4.3±1.2 km/s. Under the assumption that these stars are gravitationally bound and in dynamical equilibrium, we infer a total mass of 4.5+4.7–2.5 x105 M in the mass-follow-light case; using a two-component maximum-likelihood model, we determine a mass within 50 pc of 8.7+13–5.2x105 M. These imply mass-to-light (M/L) ratios of ln(M/LV) = 7.2+1.1–1.2 (M/LV= 1320+2680–940) and M/LV= 2440+1580–1775, respectively. The error distribution of the M/L is nearly lognormal, thus Segue 1 is dark matter-dominated at a high significance. Although we cannot rule out the possibility that Segue 1 has been tidally disrupted, we do not find kinematic evidence supporting tidal effects. Using spectral synthesis modeling, we derive a metallicity for the single red giant branch star in our sample of [Fe/H] = -3.3±0.2 dex. Finally, we discuss the prospects for detecting gamma rays from annihilation of dark matter particles and show that Segue 1 is the most promising satellite for indirect dark matter detection. 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.

Abstract Copyright:

Journal keyword(s): galaxies: dwarf - galaxies: individual: Segue 1 - galaxies: kinematics and dynamics - Local Group

VizieR on-line data: <Available at CDS (J/ApJ/692/1464): table2.dat>

Nomenclature: Table 2: [GWS2009] NNNNNNN N=51 among (Nos 1829185-3517219).

CDS comments: Table 2, col(1): NNNNNNN are the last 7 digits of SDSS DR6 objID.

Simbad objects: 61

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Number of rows : 61
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 NAME Sagittarius Stream St* 02 22 +00.0           ~ 777 0
2 SDSS J100634.81+155948.7 * 10 06 34.8183332376 +15 59 48.724762812           ~ 2 0
3 SDSS J100635.52+160221.0 * 10 06 35.5299355608 +16 02 21.085922724           ~ 3 0
4 SDSS J100636.24+160246.3 * 10 06 36.249 +16 02 46.30           ~ 2 0
5 SDSS J100637.79+160222.6 * 10 06 37.7895458832 +16 02 22.482198276           ~ 2 0
6 SDSS J100637.90+155934.4 * 10 06 37.903 +15 59 34.43           ~ 2 0
7 SDSS J100638.18+155951.1 * 10 06 38.188 +15 59 51.17           ~ 2 0
8 SDSS J100640.45+160238.1 * 10 06 40.457 +16 02 38.10           ~ 2 0
9 SDSS J100643.53+160239.9 * 10 06 43.5342675576 +16 02 39.930507348           ~ 2 0
10 SDSS J100644.54+160129.4 * 10 06 44.5493573664 +16 01 29.460554112           ~ 2 0
11 ATO J151.6857+15.9982 V* 10 06 44.5818268680 +15 59 53.898281988           ~ 5 0
12 [NWG2010] Seg1 183 RB? 10 06 49.0545614616 +16 03 48.767840100           ~ 3 0
13 SDSS J100649.63+160308.3 * 10 06 49.631 +16 03 08.31           ~ 2 0
14 SDSS J100650.82+160351.1 * 10 06 50.825 +16 03 51.20           ~ 3 0
15 SDSS J100651.04+160425.2 * 10 06 51.040 +16 04 25.29           ~ 2 0
16 [VGK2013] J100652.33+160235.8 RG* 10 06 52.3299126744 +16 02 35.876254164           ~ 10 0
17 SDSS J100655.44+160416.2 * 10 06 55.4437745184 +16 04 16.300155000           ~ 2 0
18 SDSS J100657.41+160300.0 * 10 06 57.417 +16 03 00.05           ~ 2 0
19 SDSS J100657.61+160230.0 * 10 06 57.619 +16 02 30.06           ~ 2 0
20 SDSS J100658.53+160059.9 * 10 06 58.5385857456 +16 00 59.974996536           ~ 2 0
21 SDSS J100659.76+160218.5 * 10 06 59.762 +16 02 18.50           ~ 2 0
22 SDSS J100701.33+160200.0 * 10 07 01.3403227200 +16 02 00.069876600           ~ 2 0
23 SDSS J100701.46+160304.3 * 10 07 01.467 +16 03 04.37           ~ 2 0
24 SDSS J100702.95+160136.3 * 10 07 02.955 +16 01 36.39           ~ 2 0
25 SDSS J100703.15+160335.0 * 10 07 03.150 +16 03 35.00           ~ 2 0
26 NAME Segue 1 G 10 07 03.2 +16 04 25     15.3     ~ 406 1
27 SDSS J100703.26+160234.4 * 10 07 03.2618819184 +16 02 34.455290712           ~ 2 0
28 SDSS J100703.31+160140.6 * 10 07 03.3126605160 +16 01 40.552897512           ~ 2 0
29 SDSS J100705.59+160422.0 * 10 07 05.5966912272 +16 04 22.079132652           ~ 3 0
30 SDSS J100706.74+160444.4 * 10 07 06.747 +16 04 44.46           ~ 2 0
31 [NWG2010] Seg1 95 * 10 07 07.6493872872 +16 02 43.281240324           ~ 4 0
32 SDSS J100708.91+160445.6 * 10 07 08.915 +16 04 45.61           ~ 2 0
33 SDSS J100713.68+160444.8 * 10 07 13.685 +16 04 44.81           ~ 3 0
34 SDSS J100713.97+160608.8 * 10 07 13.9707803208 +16 06 08.939982780           ~ 3 0
35 SDSS J100714.61+160302.5 * 10 07 14.6271099360 +16 03 02.386017216           ~ 2 0
36 SDSS J100714.78+160627.1 * 10 07 14.780 +16 06 27.12           ~ 2 0
37 SDSS J100714.94+160448.8 * 10 07 14.9430856608 +16 04 48.815460876           ~ 2 0
38 SDSS J100715.08+160708.1 * 10 07 15.082 +16 07 08.18           ~ 2 0
39 SDSS J100715.43+160735.0 * 10 07 15.4358089056 +16 07 35.226900984           ~ 2 0
40 SDSS J100715.71+160259.9 * 10 07 15.715 +16 02 59.98           ~ 2 0
41 SDSS J100716.25+160340.3 * 10 07 16.253 +16 03 40.31           ~ 2 0
42 [FLC2013] 300S-33 * 10 07 17.3644375368 +16 03 55.653274296           ~ 3 0
43 SDSS J100719.53+160804.8 * 10 07 19.5364589832 +16 08 04.912187280           ~ 3 0
44 SDSS J100720.52+160316.0 * 10 07 20.5318130040 +16 03 16.123044204           ~ 4 0
45 SDSS J100721.11+160334.5 * 10 07 21.1219431432 +16 03 34.586435592           ~ 3 0
46 SDSS J100724.07+160429.9 * 10 07 24.079 +16 04 29.95           ~ 2 0
47 SDSS J100725.12+160445.3 * 10 07 25.1245697352 +16 04 45.415936848           ~ 3 0
48 [NWG2010] Seg1 22 * 10 07 26.1893603520 +16 03 54.319996116           ~ 4 0
49 SDSS J100728.38+160741.1 * 10 07 28.381 +16 07 41.15           ~ 2 0
50 SDSS J100728.88+160446.6 * 10 07 28.884 +16 04 46.69           ~ 2 0
51 [GWS2009] 3517048 * 10 07 31.058 +16 04 19.51           ~ 1 0
52 SDSS J100732.47+160500.5 * 10 07 32.471 +16 05 00.53           ~ 3 0
53 SDSS J100734.28+160700.9 * 10 07 34.2877922856 +16 07 00.983894232           ~ 3 0
54 NAME Willman 1 G 10 49 21.0 +51 03 00     15.2     ~ 287 0
55 M 3 GlC 13 42 11.62 +28 22 38.2     6.39     ~ 2384 0
56 NAME Bootes II G 13 58 00.0 +12 51 00     15.4     ~ 215 0
57 NAME UMi Galaxy G 15 09 11.34 +67 12 51.7   13.60 10.6     ~ 1276 0
58 M 92 GlC 17 17 07.39 +43 08 09.4     6.52     ~ 2008 0
59 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 13192 0
60 NAME SDG G 18 55 03.1 -30 28 42   4.5 3.6     ~ 1990 2
61 NAME Local Group GrG ~ ~           ~ 7772 0

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2022.10.03-06:11:39

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