Ph.D. Dissertation Defense: Sukbum Hong, July 23

ISM and Star Formation in Dwarf Galaxies
Sukbum Hong
Monday, July 23, 2012
10: 00AM, Research Hall, Room 301

We present a study of 86 Kitt Peak International Spectroscopy Survey (KISS) dwarf galaxies using multi-wavelength observations from radio to ultraviolet and a pilot study 1066 Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) and Sloan Digital Sky Survey (SDSS) dwarf galaxies. First, we study the mid-infrared observations of 86 KISS dwarf galaxies in order to understand how the metallicity and the star formation affect on the mid-infrared color and luminosity. We find that the mid-infrared color is correlated with metallicity but not strongly with star formation rate. We build the 8.0 luminosity function and calculate the star formation rate density computed from 8.0, which is consistent with that from Hα emission. Second, we investigate the discrepancy on two star formation indicators using the ultraviolet observations of 86 KISS dwarf galaxies. We find that star formation history could affect lower star formation rate computed from emission that that from ultraviolet. Finally, we build a large dwarf galaxies sample using the combined ALFALFA and SDSS. The ALFALFA and SDSS dwarf galaxies tend to be bluer, high gas fraction and low star formation efficiency, which they are distinct from the ALFALFA and SDSS galaxies. We find 124 ALFALFA and SDSS dwarf galaxies in the green valley, 11 high gas fraction with red color, and 8 blue color with low gas fraction to compare these with 5 transition dwarf galaxies in Local Group. The ALFALFA and SDSS dwarf galaxies in the green valley are very similar to the transition dwarf galaxy in terms of their color and gas fraction. Thus, the evolution of dwarf galaxies might be similar to that of massive galaxies, which transform from blue cloud to red sequence.