期刊
ASTROPHYSICAL JOURNAL
卷 757, 期 1, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/757/1/85
关键词
galaxies: dwarf; galaxies: stellar content; methods: statistical
资金
- NSF [AST-0908752]
- Alfred P. Sloan Foundation
- NASA Astrophysics Data Analysis Program [08-ADP08-0072]
- National Aeronautics and Space Administration
We demonstrate that dwarf galaxies (10(7) < M-stellar < 10(9) M-circle dot, -12 > M-r > -18) with no active star formation are extremely rare (<0.06%) in the field. Our sample is based on the NASA-Sloan Atlas which is a reanalysis of the Sloan Digital Sky Survey Data Release 8. We examine the relative number of quenched versus star-forming dwarf galaxies, defining quenched galaxies as having no Ha emission (EWH alpha < 2 angstrom) and a strong 4000 angstrom break. The fraction of quenched dwarf galaxies decreases rapidly with increasing distance from a massive host, leveling off for distances beyond 1.5 Mpc. We define galaxies beyond 1.5 Mpc of a massive host galaxy to be in the field. We demonstrate that there is a stellar mass threshold of M-stellar < 1.0 x 10(9) M-circle dot below which quenched galaxies do not exist in the field. Below this threshold, we find that none of the 2951 field dwarf galaxies are quenched; all field dwarf galaxies show evidence for recent star formation. Correcting for volume effects, this corresponds to a 1 sigma upper limit on the quenched fraction of 0.06%. In more dense environments, quenched galaxies account for 23% of the dwarf population over the same stellar mass range. The majority of quenched dwarf galaxies (often classified as dwarf elliptical galaxies) are within 2 virial radii of a massive galaxy, and only a few percent of quenched dwarf galaxies exist beyond 4 virial radii. Thus, for galaxies with stellar mass less than 1.0 x 10(9)M(circle dot), ending star formation requires the presence of a more massive neighbor, providing a stringent constraint on models of star formation feedback.
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