Type: 
Colloquium
Date-Time: 
Monday, January 11, 2016 - 16:00 to 17:00
Location: 
WNGR116
Event Speaker: 
Alison Crocker (Reed College)
Local Contact: 
Davide Lazzati
Abstract: 

Prior to the past decade, early-type galaxies in the present-day Universe were considered to be “passively evolving” - no longer forming any new stars. However, surveys now show that a significant fraction (approximately one quarter) of early-type galaxies have molecular gas, the raw material for star formation. Are the properties of star formation and cool gas the same in these bulge-dominated galaxies as in the more commonly studied spiral, starburst and irregular star-forming galaxies? First I will show what a handful of these star-forming early-type galaxies look like in detail. The molecular gas in early-types is found to be in very central distributions, where the effects of shear, hydrostatic pressure and possible active galactic nuclei (AGN) will be maximal. But little is yet known about the state of molecular gas in these galaxies. I will present the results of a survey of 18 molecular-gas rich early-type galaxies from the Atlas3d sample in a variety of molecular transitions. This study reveals a wide range of average optical depths for the molecular gas, but a fairly constant dense gas fraction.  Secondly, many commonly used star formation indicators fail or are less reliable in early-type galaxies than in the spirals and starbursts against which they were calibrated. I will discuss the best ways we can trace star formation in these galaxies, including new work identifying young stars clusters using Hubble Space Telescope data. Finally, I will discuss whether the molecular gas in early-type galaxies may be less efficient at forming stars, despite the universal molecular gas-SFR relation observed for other galaxy types.