CHARACTERIZING THE STAR FORMATION OF THE LOW-MASS SHIELD GALAXIES FROM HUBBLE SPACE TELESCOPE IMAGING

The Survey of Hi in Extremely Low-mass Dwarfs is an on-going multi-wavelength program to characterize the gas, star formation, and evolution in gas-rich, very low-mass galaxies that populate the faint end of the galaxy luminosity function. The galaxies were selected from the first ∼10% of the Hi Are...

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Bibliographic Details
Published in:The Astrophysical journal 2015-03, Vol.802 (1), p.66
Main Authors: McQuinn, Kristen. B. W., Cannon, John M., Dolphin, Andrew E., Skillman, Evan D., Haynes, Martha P., Simones, Jacob E., Salzer, John J., Adams, Elizabeth A. K., Elson, Ed C., Giovanelli, Riccardo, Ott, Jürgen
Format: Article
Language:English
Subjects:
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BARYONS
COLOR
COMPARATIVE EVALUATIONS
CORRELATIONS
DIAGRAMS
DISTANCE
DWARF STARS
GALAXIES
GRAVITATIONAL INTERACTIONS
LIFETIME
LUMINOSITY
MASS
SPACE
STAR EVOLUTION
TELESCOPES
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Summary:The Survey of Hi in Extremely Low-mass Dwarfs is an on-going multi-wavelength program to characterize the gas, star formation, and evolution in gas-rich, very low-mass galaxies that populate the faint end of the galaxy luminosity function. The galaxies were selected from the first ∼10% of the Hi Arecibo Legacy Fast ALFA survey based on their low Hi mass and low baryonic mass. Here, we measure the star formation properties from optically resolved stellar populations for 12 galaxies using a color–magnitude diagram fitting technique. We derive lifetime average star formation rates (SFRs), recent SFRs, stellar masses, and gas fractions. Overall, the recent SFRs are comparable to the lifetime SFRs with mean birthrate parameter of 1.4, with a surprisingly narrow standard deviation of 0.7. Two galaxies are classified as dwarf transition galaxies (dTrans). These dTrans systems have star formation and gas properties consistent with the rest of the sample, in agreement with previous results that some dTrans galaxies may simply be low-luminosity dwarf irregulars. We do not find a correlation between the recent star formation activity and the distance to the nearest neighboring galaxy, suggesting that the star formation process is not driven by gravitational interactions, but regulated internally. Further, we find a broadening in the star formation and gas properties (i.e., specific SFRs, stellar masses, and gas fractions) compared to the generally tight correlation found in more massive galaxies. Overall, the star formation and gas properties indicate these very low-mass galaxies host a fluctuating, non-deterministic, and inefficient star formation process.
ISSN:1538-4357
0004-637X
1538-4357
DOI:10.1088/0004-637X/802/1/66