Bradley Warren (RSAA/ATNF)

The Nature of High HI Mass-to-Light Ratio Field Galaxies - Bradley Warren Colloquium

ATNF Marsfield Lecture Theatre

Abstract

I will discuss a multi-wavelength investigation of a sample of high HI
mass-to-light ratio (M_HI/L_B) dwarf galaxies selected from the HIPASS Bright
Galaxy Catalog (BGC) which we have done using the Australia Telescope Compact
Array and the ANU 2.3-m Telescope. Galaxies which still maintain large
quantities of unprocessed neutral hydrogen (HI) compared to their stellar
content are important for near field cosmology as they suggest the existence of
unevolved "dark" galaxies. Within these galaxies star formation may have been
impaired or halted, has lacked stimulation, or has only recently begun. If they
exist in sufficient numbers they may potentially account for the discrepancy
between the number of low mass dark matter halos predicted by recent CDM based
models and observations. The existence of some extreme M_HI/L_B galaxies can be
used to constrain galaxy models. I will discuss the global stellar and HI
properties, HI dynamics, star formation rates, and gas surface density
thresholds, looking at the correlations of HI mass-to-light ratio for our sample
galaxies with respect to luminosity, stellar density, and environment. From
this, can we explain why a few galaxies have retained their primordial gas
content while other galaxies have processed most of their gas into stars?