Time: 11:00 h
Author: Julianne Dalcanton
The Panchromatic Hubble Andromeda Treasury is an HST multicycle program to image the north east quadrant of M31 to deep limits in the UV, optical, and near-IR. The HST imaging has resolved the galaxy into over 150 million stars (comparable to ~1/2 the number of stars in SDSS), all with common distances and foreground extinctions. We have recently completed comparable imaging for the high-intensity star forming disk of M33. These surveys add M31 and M33 to the Milky Way and Magellanic Clouds as fundamental calibrators of stellar evolution and star-formation processes. I will briefly describe the survey strategy, data reduction, and key data products. I will then highlight work using the NIR stellar populations to constrain the large scale properties of the cold ISM, with 25 pc resolution. These new maps offer the highest resolution available in M31, and point to surprising challenges facing models of dust emission and new possibilities for the study of pressure as a driver of star formation efficiency.