Journal
ASTROPHYSICAL JOURNAL
Volume 779, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/779/2/102
Keywords
galaxies: abundances; galaxies: dwarf; galaxies: fundamental parameters; galaxies: irregular; Local Group
Categories
Funding
- Southern California Center for Galaxy Evolution
- University of California Office of Research
- NSF [AST-1009973, AST-10-10039]
- NSF grant [AST-0908139]
- UCSC's Science Internship Program (SIP)
- EU [267251 AstroFIt]
- Alfred P. Sloan Foundation
- National Science Foundation
- U.S. Department of Energy
- National Aeronautics and Space Administration
- Japanese Monbukagakusho
- Max Planck Society
- Higher Education Funding Council for England
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1010039] Funding Source: National Science Foundation
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We present spectroscopic metallicities of individual stars in seven gas-rich dwarf irregular galaxies (dIrrs), and we show that dIrrs obey the same mass-metallicity relation as the dwarf spheroidal (dSph) satellites of both the Milky Way and M31: Z(*) proportional to M-*(0.30 +/- 0.02). The uniformity of the relation is in contradiction to previous estimates of metallicity based on photometry. This relationship is roughly continuous with the stellar mass-stellar metallicity relation for galaxies as massive as M-* = 10(12) M-circle dot. Although the average metallicities of dwarf galaxies depend only on stellar mass, the shapes of their metallicity distributions depend on galaxy type. The metallicity distributions of dIrrs resemble simple, leaky box chemical evolution models, whereas dSphs require an additional parameter, such as gas accretion, to explain the shapes of their metallicity distributions. Furthermore, the metallicity distributions of the more luminous dSphs have sharp, metal-rich cut-offs that are consistent with the sudden truncation of star formation due to ram pressure stripping.
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