| Description |
A popular scenario to explain the increase in number of quiescent, elliptical galaxies over cosmic time is one in which gas-rich major mergers lead to strong starbursts which exhaust fuel supplies and transform the morphology of galaxies from disks to spheroids. In this proposal we describe how PACS+SPIRE photometry can directly test this scenario. We present a unique sample of massive starburst-to-post-starburst galaxies in the local Universe (z<0.05), which have undergone a starburst between 10Myr and 1Gyr ago. The sample is drawn from a statistically complete sample of Sloan Digital Sky Survey (post-)starburst galaxies, i.e. they have experienced the same strength starburst. Together with CO molecular gas masses (already obtained), we will use the Herschel photometry to track the evolution of dust mass, dust temperature and dust-to-gas ratios for 1Gyr following the starburst. This will allow us to directly test (1) how star formation is quenched following a starburst: gas exhaustion, expulsion or change of gas state; (2) whether massive starburst galaxies are the progenitors of red-sequence galaxies. Additionally, we will use our accurate starburst ages to test whether supernovae or post-AGB stars contribute significantly to the enrichment of the interstellar medium (ISM) with dust. By combining with results from similar studies of local merger- or IR-selected galaxy samples we will calculate a duty-cycle for IR bright galaxies, crucial for understanding the selection of high-z galaxy samples. By combining our (post-)starburst galaxy sample defined upon the physical properties of starburst age and strength, with the diagnostic capabilities of CO and dust emission for probing the physical state of the ISM, this dataset will provide the best observational constraints to date on the merger+starburst evolutionary pathway from star-forming spiral to quiescent elliptical galaxy. |
