期刊
ASTROPHYSICAL JOURNAL
卷 808, 期 1, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/808/1/95
关键词
dark matter; galaxies: dwarf; galaxies: individual (Reticulum II); galaxies: stellar content; Local Group; stars: abundances
资金
- National Science Foundation [AST-1108811, AST-1138766]
- PAPDRJ
- CAPES/FAPERJ
- CAPES [3171-13-2]
- NSF/MRI [AST-0923160]
- NSF [AST-1312967, AST-1313045]
- U.S. Department of Energy
- U.S. National Science Foundation
- Ministry of Science and Education of Spain
- Science and Technology Facilities Council of the United Kingdom
- Higher Education Funding Council for England
- National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign
- Kavli Institute of Cosmological Physics at the University of Chicago
- Center for Cosmology and Astro-Particle Physics at the Ohio State University
- Mitchell Institute for Fundamental Physics and Astronomy at Texas AM University
- Deutsche Forschungsgemeinschaft
- Financiadora de Estudos e Projetos
- Fundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro
- Conselho Nacional de Desenvolvimento Cientifico e Tecnologico
- Ministerio da Ciencia, Tecnologia e Inovacao
- Collaborating Institutions in the Dark Energy Survey
- MINECO [AYA2012-39559, ES2P2013-48274, FPA2013-47986]
- Centro de Excelencia Severo Ochoa [SEV-2012-0234]
- European Union
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1108811] Funding Source: National Science Foundation
- Direct For Mathematical & Physical Scien
- Division Of Physics [1125897] Funding Source: National Science Foundation
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1311924] Funding Source: National Science Foundation
- Science and Technology Facilities Council [ST/M003574/1, 1093560, ST/M007030/1, ST/I000976/1, ST/L006529/1, ST/H001581/1, ST/L000652/1, ST/N001087/1] Funding Source: researchfish
- STFC [ST/H001581/1, ST/I000976/1, ST/M003574/1, ST/L000652/1, ST/F001991/1, ST/L006529/1, ST/N001087/1, ST/I000879/1, ST/J001511/1, ST/M007030/1] Funding Source: UKRI
We present Magellan/M2FS, Very Large Telescope/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(-1) and a velocity dispersion of 3.3 +/- 0.7 km s(-1). The mass-to-light ratio of Ret II within its half-light radius is 470 +/- 210 M circle dot L circle dot, 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(-1), 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(10)(J) 18 +/- 80.6 GeV-2 cm(-5) within 0 degrees.2, indicating that the predicted gamma-ray flux from dark matter annihilation in Ret II is lower than that of several other dwarf galaxies.
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