LeMMINGs Abstract
The two processes which dominate the appearance of our universe are star-formation and accretion. Star-formation (SF) is fundamental to the formation and evolution of galaxies whilst accretion provides a major power source in the universe, dominating the emission from distant quasars as well as from nearby X-ray binary systems. The feedback between these two processes is also crucial, e.g. in reconciling the observed galaxy luminosity function with the predictions from the standard hierarchical clustering models. Radio observations provide by far the best single diagnostic of these two processes, providing a direct view of SF even in dusty environments and allowing detection of AGN and measurement of their accretion rate at bolometric luminosities far below anything detectable at higher energies. A large, statistically complete, sample of galaxies such as we propose here, provides the perfect laboratory to study for the first time not only these two processes, but also to quantify how they interact in different types of galaxies. e-MERLIN is perfectly tuned to such studies as, even at low frequencies, its pc-scale resolution, coupled with spectral information, allows almost unambiguous discrimination of even faint AGN inside large SF regions. Specifically here we will carry out a complete census of SF and AGN activity as a function of galaxy mass, morphology and spectral type, black hole mass and luminosity. We will thus calibrate other SF indicators, e.g. IR and Hα luminosity, and constrain patterns in jet strength compared to merger histories. Additionally, we will determine whether ultra-luminous X-ray sources may come from intermediate mass black holes.The broad philosophy of this legacy programme will be to provide the definitive parsec-scale, μJy sensitivity radio images of a large sample of well-known galaxies in the nearby universe. As such this project will both address numerous key science questions regarding SF and activity in galaxies and is specifically designed to be a lasting Legacy data-set for the wider community, with the sample selected to maximize multi-wavelength coverage and consequently the amount of future legacy science achievable.