Journal
ASTRONOMICAL JOURNAL
Volume 143, Issue 6, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0004-6256/143/6/133
Keywords
galaxies: dwarf; galaxies: evolution; galaxies: fundamental parameters; galaxies: star formation; radio lines: galaxies; surveys
Categories
Funding
- NASA [NAS5-98034, NNX07AJ12G, NNX08AL67G, NNX09AF79G]
- National Science Foundation [AST-0607007, AST-1107390]
- Brinson Foundation
- Alfred P. Sloan Foundation
- US Department of Energy
- Japanese Monbukagakusho
- Max Planck Society
- Higher Education Funding Council for England
- American Museum of Natural History
- Astrophysical Institute Potsdam
- University of Basel
- University of Cambridge
- Case Western Reserve University
- University of Chicago
- Drexel University
- Fermilab
- Institute for Advanced Study
- Japan Participation Group
- Johns Hopkins University
- Joint Institute for Nuclear Astrophysics
- Kavli Institute for Particle Astrophysics and Cosmology
- Korean Scientist Group
- Chinese Academy of Sciences (LAMOST)
- Los Alamos National Laboratory
- Max Planck Institute for Astronomy
- MPA
- New Mexico State University
- Ohio State University
- University of Pittsburgh
- University of Portsmouth
- Princeton University
- United States Naval Observatory
- University of Washington
- NASA [118656, NNX08AL67G, 99072, NNX09AF79G] Funding Source: Federal RePORTER
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We examine the global properties of the stellar and Hi components of 229 low H I mass dwarf galaxies extracted from the ALFALFA survey, including a complete sample of 176 galaxies with H I masses < 10(7.7) M-circle dot and Hi line widths < 80 km s(-1). Sloan Digital Sky Survey (SDSS) data are combined with photometric properties derived from Galaxy Evolution Explorer to derive stellar masses (M-*) and star formation rates (SFRs) by fitting their UV-optical spectral energy distributions (SEDs). In optical images, many of the ALFALFA dwarfs are faint and of low surface brightness; only 56% of those within the SDSS footprint have a counterpart in the SDSS spectroscopic survey. A large fraction of the dwarfs have high specific star formation rates (SSFRs), and estimates of their SFRs and M-* obtained by SED fitting are systematically smaller than ones derived via standard formulae assuming a constant SFR. The increased dispersion of the SSFR distribution at M-* less than or similar to 10(8) M-circle dot is driven by a set of dwarf galaxies that have low gas fractions and SSFRs; some of these are dE/dSphs in the Virgo Cluster. The imposition of an upper H I mass limit yields the selection of a sample with lower gas fractions for their M-* than found for the overall ALFALFA population. Many of the ALFALFA dwarfs, particularly the Virgo members, have H I depletion timescales shorter than a Hubble time. An examination of the dwarf galaxies within the full ALFALFA population in the context of global star formation (SF) laws is consistent with the general assumptions that gas-rich galaxies have lower SF efficiencies than do optically selected populations and that Hi disks are more extended than stellar ones.
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