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Tuesday, 8th September at 11.00am at the JAC
Ji Hoon Kim
Seoul National University
"The episodic star formation history of low surface brightness galaxies"
ABSTRACT:
The star formation history of low surface brightness galaxies (LSBGs) are
interesting but poorly constrained. These objects tend to be rather blue,
contradicting the initial impression that they may simply be faded remnants of
higher surface brightness galaxies whose star formation has finished. With low
star formation rates and relatively large gas reservoirs, their
formation epochs and star formation histories are likely very unique.
Based on near-infrared broadband photometry and H-alpha photometry
of a large sample of low surface brightness galaxies, we find that the
current star formation rates of LSBGs generally are higher than their
past star formation rate, suggesting that the mean age of their
stellar population is relatively young. This may stem from either a
late epoch of formation or a sluggish evolution. In the latter case,
the star formation efficiency may be an increasing function of time,
perhaps due in part to the slow build-up of metals and dust.
Nevertheless, star formation remains sporadic and is generally not
well organized across the disk. We also find a strong correlation
between the ratio of the current to past average star formation rate and
the gas mass fraction. Galaxies with large reservoirs of gas have
relatively high current SFRs. There is a conspicuous absence of high
gas mass fraction, low SFR galaxies, suggesting that the observed
trend is not driven by bursts of star formation with short duty
cycles.
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