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The Primeval Populations of the Ultra-faint Dwarf Galaxies

Brown, Thomas M. and Tumlinson, Jason and Geha, Marla and Kirby, Evan N. and VandenBerg, Don A. and Muñoz, Ricardo R. and Kalirai, Jason S. and Simon, Joshua D. and Avila, Roberto J. and Guhathakurta, Puragra and Renzini, Alvio and Ferguson, Henry C. (2012) The Primeval Populations of the Ultra-faint Dwarf Galaxies. Astrophysical Journal Letters, 753 (1). Art. No. L21. ISSN 2041-8205.

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We present new constraints on the star formation histories of the ultra-faint dwarf (UFD) galaxies, using deep photometry obtained with the Hubble Space Telescope (HST). A galaxy class recently discovered in the Sloan Digital Sky Survey, the UFDs appear to be an extension of the classical dwarf spheroidals to low luminosities, offering a new front in efforts to understand the missing satellite problem. They are the least luminous, most dark-matter-dominated, and least chemically evolved galaxies known. Our HST survey of six UFDs seeks to determine if these galaxies are true fossils from the early universe. We present here the preliminary analysis of three UFD galaxies: Hercules, Leo IV, and Ursa Major I. Classical dwarf spheroidals of the Local Group exhibit extended star formation histories, but these three Milky Way satellites are at least as old as the ancient globular cluster M92, with no evidence for intermediate-age populations. Their ages also appear to be synchronized to within ∼1 Gyr of each other, as might be expected if their star formation was truncated by a global event, such as reionization.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Brown, Thomas M.0000-0002-1793-9968
Tumlinson, Jason0000-0002-7982-412X
Geha, Marla0000-0002-7007-9725
Kirby, Evan N.0000-0001-6196-5162
Kalirai, Jason S.0000-0001-9690-4159
Guhathakurta, Puragra0000-0001-8867-4234
Renzini, Alvio0000-0002-7093-7355
Ferguson, Henry C.0000-0001-7113-2738
Additional Information:© 2012 The American Astronomical Society. Received 2012 April 20; accepted 2012 June 4; published 2012 June 15. Support for GO-12549 was provided by NASA through a grant from STScI, which is operated by AURA, Inc., under NASA contract NAS 5-26555. E. N. K. acknowledges support by NASA through Hubble Fellowship grant 51256.01 from STScI. A. R. acknowledges support from ASI via grant I/009/10/0. R. R. M. acknowledges support from the GEMINI-CONICYT Fund, allocated to the project No. 32080010. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at STScI, which is operated by AURA, Inc., under NASA contract NAS 5-26555.
Funding AgencyGrant Number
NASA Hubble FellowshipHF-51256.01
Agenzia Spaziale Italiana (ASI)I/009/10/0
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)N32080010
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Subject Keywords:galaxies: dwarf; galaxies: evolution; galaxies: formation; galaxies: photometry; galaxies: stellar content; Local Group
Issue or Number:1
Record Number:CaltechAUTHORS:20120723-151504481
Persistent URL:
Official Citation:The Primeval Populations of the Ultra-faint Dwarf Galaxies Thomas M. Brown et al. 2012 ApJ 753 L21
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:32655
Deposited By: Aucoeur Ngo
Deposited On:24 Jul 2012 14:34
Last Modified:15 Nov 2019 03:37

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