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Stellar kinematics and metallicities in the ultra-faint dwarf galaxy Reticulum II
- Source :
- Simon, J D, Drlica-Wagner, A, Li, T S, Nord, B, Geha, M, Bechtol, K, Balbinot, E, Buckley-Geer, E, Lin, H, Marshall, J, Santiago, B, Strigari, L, Wang, M, Wechsler, R H, Yanny, B, Abbott, T, Bauer, A H, Bernstein, G M, Bertin, E, Brooks, D, Burke, D L, Capozzi, D, Rosell, A C, Kind, M C, D'Andrea, C B, Da Costa, L N, DePoy, D L, Desai, S, Diehl, H T, Dodelson, S, Cunha, C E, Estrada, J, Evrard, A E, Neto, A F, Fernandez, E, Finley, D A, Flaugher, B, Frieman, J, Gaztanaga, E, Gerdes, D, Gruen, D, Gruendl, R A, Honscheid, K, James, D, Kent, S, Kuehn, K, Kuropatkin, N, Lahav, O, Maia, M A G, March, M & Dark Energy Survey Collaboration 2015, ' Stellar kinematics and metallicities in the ultra-faint dwarf galaxy reticulum II ', Astrophysical Journal, vol. 808, no. 1, 95 . https://doi.org/10.1088/0004-637X/808/1/95
- Publication Year :
- 2015
- Publisher :
- Institute of Physics, 2015.
-
Abstract
- We present Magellan/M2FS, VLT/GIRAFFE, and Gemini South/GMOS spectroscopy of the newly discovered Milky Way satellite Reticulum II. Based on the spectra of 25 Ret II member stars selected from Dark Energy Survey imaging, we measure a mean heliocentric velocity of 62.8 +/- 0.5 km/s and a velocity dispersion of 3.3 +/- 0.7 km/s. The mass-to-light ratio of Ret II within its half-light radius is 470 +/- 210 Msun/Lsun, demonstrating that it is a strongly dark matter-dominated system. Despite its spatial proximity to the Magellanic Clouds, the radial velocity of Ret II differs from that of the LMC and SMC by 199 and 83 km/s, respectively, suggesting that it is not gravitationally bound to the Magellanic system. The likely member stars of Ret II span 1.3 dex in metallicity, with a dispersion of 0.28 +/- 0.09 dex, and we identify several extremely metal-poor stars with [Fe/H] < -3. In combination with its luminosity, size, and ellipticity, these results confirm that Ret II is an ultra-faint dwarf galaxy. With a mean metallicity of [Fe/H] = -2.65 +/- 0.07, Ret II matches Segue~1 as the most metal-poor galaxy known. Although Ret II is the third-closest dwarf galaxy to the Milky Way, the line-of-sight integral of the dark matter density squared is log J = 18.8 +/- 0.6 Gev^2/cm^5 within 0.2 degrees, indicating that the predicted gamma-ray flux from dark matter annihilation in Ret II is lower than that of several other dwarf galaxies.<br />14 pages, 6 figures (4 in color), 2 tables. Accepted for publication in the Astrophysical Journal. Only minor changes from v1
- Subjects :
- individual (Reticulum II) [galaxies]
Stellar kinematics
Cosmology and Nongalactic Astrophysics (astro-ph.CO)
dwarf [galaxies]
Metallicity
Milky Way
Dark matter
FOS: Physical sciences
Astrophysics
01 natural sciences
dark matter
0103 physical sciences
010303 astronomy & astrophysics
STFC
Dwarf galaxy
QB
Physics
010308 nuclear & particles physics
RCUK
Velocity dispersion
Astronomy and Astrophysics
stellar content [galaxies]
Astrophysics - Astrophysics of Galaxies
Galaxy
Radial velocity
bundances [stars]
Space and Planetary Science
Astrophysics of Galaxies (astro-ph.GA)
Local Group
Astrophysics - Cosmology and Nongalactic Astrophysics
Subjects
Details
- Language :
- English
- ISSN :
- 0004637X
- Database :
- OpenAIRE
- Journal :
- Simon, J D, Drlica-Wagner, A, Li, T S, Nord, B, Geha, M, Bechtol, K, Balbinot, E, Buckley-Geer, E, Lin, H, Marshall, J, Santiago, B, Strigari, L, Wang, M, Wechsler, R H, Yanny, B, Abbott, T, Bauer, A H, Bernstein, G M, Bertin, E, Brooks, D, Burke, D L, Capozzi, D, Rosell, A C, Kind, M C, D'Andrea, C B, Da Costa, L N, DePoy, D L, Desai, S, Diehl, H T, Dodelson, S, Cunha, C E, Estrada, J, Evrard, A E, Neto, A F, Fernandez, E, Finley, D A, Flaugher, B, Frieman, J, Gaztanaga, E, Gerdes, D, Gruen, D, Gruendl, R A, Honscheid, K, James, D, Kent, S, Kuehn, K, Kuropatkin, N, Lahav, O, Maia, M A G, March, M & Dark Energy Survey Collaboration 2015, ' Stellar kinematics and metallicities in the ultra-faint dwarf galaxy reticulum II ', Astrophysical Journal, vol. 808, no. 1, 95 . https://doi.org/10.1088/0004-637X/808/1/95
- Accession number :
- edsair.doi.dedup.....3c811d9d1bed9113e93da76ffac347c7