Kristen McQuinn (University of Texas, Austin)
Theories of galaxy evolution have been tested by our a growing knowledge of low-mass galaxies. Much of the progress has been made studying the closest of satellites whose histories are inextricably linked to their massive host galaxy. Finding isolated galaxies to populate the faint-end of the luminosity function outside our group environment means looking farther afield – a task which has proven unavoidably problematic due to the intrinsic faintness of the systems. One such galaxy, Leo P, has been discovered through the blind HI ALFALFA Survey. Located just outside the Local Group, observations have shown that Leo P is a gas-rich dwarf galaxy with active star formation, an underlying older stellar population, an extremely low oxygen abundance (3% solar), and a dynamical mass of only 2 x 10^7 Msun.
The physical properties of Leo P lie below many thresholds from theoretical predictions and allow us to address numerous questions about galaxy evolution at the faint-end of the luminosity function:
Does re-ionization alone quench star formation in low-mass halos? Do high-mass stars readily form at extremely low SFRs? How many metals can a low-mass galaxy retain? In the overlap mass range between dSph and dIrr, are there clues linking their formation or evolution?.
In this talk I will discuss the results on Leo P, focusing on the intersection between theory and observation at the faint-end of the luminosity function.