Tuesday Lunch (4/22): Linda Watson (CfA)

Star Formation in Nearby Late-Type Galaxies

Dr. Linda Watson (CfA)
CAS 500, 12:30 pm, April 22, 2014

Observational studies of star formation in nearby galaxies rely on high-quality data that trace the atomic and molecular interstellar medium (e.g., via HI and CO emission) and recently formed stars (e.g., via Halpha or FUV emission). These studies, as well as theoretical works, aim to determine which physical processes dictate the efficiency of converting gas into stars. I will describe two projects that address this goal by probing conditions where the typical relationship between gas density and star formation rate might break down. First, I will present results from a study of star formation in bulgeless disk galaxies that span the threshold circular velocity of 120 km/s (stellar mass ~ 10^10 M_sun), where Dalcanton et al. discovered a transition in dust structure, dust scale height, and disk stability. I will discuss whether the star formation efficiency in these galaxies is described by a global model of the interstellar medium or by a local model including only molecular cloud-scale physics. Second, I will present results on the connection between molecular gas and star formation in an HII region in the outer disk of an extended ultraviolet (XUV) disk galaxy. Outer disks offer the opportunity to study star formation in regions with low gas density, low molecular fraction, and where star formation rate tracers may be affected by aging, stochasticity, leakage of ionizing photons, and/or variation in the initial mass function.