| Description |
To explain the nature of galaxies in the present day universe, contemporary models of galaxy evolution require feedback to expel a substantial fraction of the gas and dust fueling stellar and black hole growth, thereby driving galaxies into quiescence. Post-starburst galaxies are systems found precisely in this phase -- after star formation has been abruptly halted. Due primarily to lack of sample and sensitivity, however, the dust and gas content of post-starbursts has remained essentially an unknown. Until recently very challenging to find and study, large samples of close to one thousand post-starbursts can now be selected using the combined power of SDSS and GALEX.We propose targeted follow-up of a sample of 33 post-starbursts, carefully selected to sample uniformly a wide range of precisely determined post-burst ages, from 50Myr to 1.5Gyr. To construct this sample, we have powerfully extended our unique UV/Optical selection using pre-release WISE full-sky photometry, which provides critical sampling of their mid-infrared SEDs. With PACS and SPIRE photometry extending SED coverage beyond the dust emission peak, and PACS spectroscopy in the dominant gas cooling lines CII and OI, we can begin to address the question of how and why galaxies stop forming stars and fade into quiescence.Herschel alone can provide the vital, unique information on the conditions and content of neutral gas and dust in galaxies during this crucial transitional phase in their evolution. Our program will 1) characterize the ISM content in these systems as a function of post-burst age, 2) search for clues identify their quenching mechanisms, 3) explore the form and behavior of dust in unique and extreme environments, and 4) test the laws governing star formation and the flow of energy through the ISM in a wholly new regime -- where gas and dust are plentiful, but where star-formation has recently and abruptly ceased. |
