Constraining the Properties of the Metal-Poor ISM with Interferometric CO Observations of Low Metallicity Dwarf Galaxies


Metal deficient dwarf galaxies are critical test beds for theories about the structure of star forming clouds at low metallicity, the chemical evolution of the interstellar medium, and the conditions in the early Universe. I present new high-resolution interferometric observations of the CO J = 1 - 0 emission line in five nearby metal poor dwarf irregular galaxies taken with the CARMA array. The first half of this work considers four galaxies with very extreme metallicities (3-10% Solar), including Leo P, DDO 68, Sextans A, and Sextans B. While CO was not detected in any of these systems, we are able to derive very sensitive upper limits to their global CO luminosities, calculate molecular hydrogen masses using various CO-to-H2 conversion factors, and compare these results to chemical evolution models. The second half of this work consists of a case study on the interstellar medium of NGC 6822, a famous Local Group dwarf irregular galaxy at ~30% of Solar metallicity. CARMA resolves ten individual clouds of dense CO emission at ~10 pc linear scales in a central region of the galaxy. CO luminosities and derived H2 masses are presented for each cloud, and the cloud properties are compared to similar observations in the literature. I then leverage data at a myriad of wavelengths to draw spatial comparisons between the distributions of dense molecular gas, atomic gas, PAHs, and dust at various temperatures.

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