| This thesis presents several studies of molecular gas in nearby dwarf irregular galaxies. These galaxies harbor environments distinct from those found in large spiral galaxies like the Milky Way. They therefore offer an opportunity to study the effect of environment on star formation. This thesis has four main parts: a survey studying how molecular gas content relates to other galaxy parameters; case studies of two very nearby dwarf galaxies, IC 10 and the SMC; and a detailed look at the methodology used to measure properties of giant molecular clouds (GMCs).; We searched nearby dwarf galaxies for CO emission, the most commonly used tracer of molecular gas. We increase the number of dwarfs with measured CO emission by 50% and find very little variation in the normalized CO content of a galaxy with mass down to about the mass of the Large Magellanic Cloud. Further, the molecular gas in dwarfs forms stars at about the same rate as molecular gas in large galaxies, as measured by the ratio of radio continuum emission to CO emission.; Local Group dwarf galaxies show much lower normalized CO contents than large spiral galaxies or the dwarfs that we detect. Selection effects may skew the results of these surveys towards dwarf starbursts. We conduct detailed case studies of two of the Local Group irregulars: (1) we map the entire CO content of IC 10, the nearest dwarf starburst galaxy, with the resolution to distinguish individual GMCs: and (2) we use data from the Spitzer Survey of the Small Magellanic Cloud to study the dust and molecular gas in the nearest low metallicity galaxy, the Small Magellanic Cloud. Studying the CO, we find little variation between the properties of GMCs in dwarf galaxies and those in large spirals. However, using the dust as a tracer of the molecular gas in the SMC, we find substantially more H 2 than we would predict from CO. In dwarf galaxies stars may form out of an environment similar to Galactic GMCs, the CO emitting regions, but there may be an abundance of CO-free H2 beyond these cores. |
