CaltechAUTHORS
Published July 1, 2012 | Version Accepted Version + Published
Journal Article Open

The Primeval Populations of the Ultra-faint Dwarf Galaxies

Creators

  • 1. ROR icon Space Telescope Science Institute
  • 2. ROR icon Yale University
  • 3. ROR icon California Institute of Technology
  • 4. ROR icon University of Victoria
  • 5. ROR icon University of Chile
  • 6. ROR icon Carnegie Observatories
  • 7. ROR icon University of California, Santa Cruz

Abstract

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.

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.

Attached Files

Published - Brown2012p18934Astrophys_J_Lett.pdf

Accepted Version - 1206.0941.pdf

Files

1206.0941.pdf

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Additional details

Identifiers

Eprint ID
32655
Resolver ID
CaltechAUTHORS:20120723-151504481

Related works

Describes
https://arxiv.org/abs/1206.0941 (URL)

Funding

NASA Hubble Fellowship
HF-51256.01
Agenzia Spaziale Italiana (ASI)
I/009/10/0
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)
N32080010
Istituto Nazionale di Astrofisica (INAF)

Dates

Created
2012-07-24
Created from EPrint's datestamp field
Updated
2021-11-09
Created from EPrint's last_modified field