Aleks Diamond-Stanic, University of Wisconsin-Madison

Our understanding of galaxy evolution centers around questions of how gas gets into galaxies, how it participates in star formation and black hole growth, and how it is returned to its galactic surroundings via feedback. On a global scale, measurements of the baryon density and the stellar mass function indicate that only 5% of baryons have formed stars by the present day, and this suggests that feedback from massive stars and supermassive black holes must prevent gas from forming stars in both low-mass and high-mass dark matter halos. I will present observational results on the geometry and kinematics of outflowing and inflowing gas around galaxies, including measurements of ejective feedback that is capable of quenching star formation by removing the cold gas supply. These results have broader implications for how gas is consumed and expelled at the centers of massive galaxies and for the limits of feedback from stellar radiation and supernovae. I will also discuss prospects for characterizing the physical properties of gas in and around galaxies using multi-wavelength spectroscopy with existing and future facilities.

Katherine Alatalo, Carnegie Observatories

Modern day galaxies are found to be in a bimodal distribution, both in terms of their morphologies, and in terms of their colors, and these properties are inter-related. In color space, there is a genuine dearth of intermediate colored galaxies, which has been taken to mean that the transition a galaxy undergoes to transform must be rapid. I will discuss two such pathways galaxies take to rapidly transform from vibrant, blue spirals into quiescent, red elliptical and lenticulars, in particular, through the lens of the molecular gas. This includes the ways in which (1) AGN feedback (one of the proposed transformation mechanisms) and (2) constant harassment within compact groups can impact an environment that is rich in molecular gas, rendering it unable to form stars. I discuss new observations that have shown this phenomenon (as well as potential recipes to identify more of these objects), as well as the implications that these mechanisms have for galaxy evolution.

Aaron Parsons, University of California, Berkeley

Since it was first proposed nearly two decades ago, measuring 21cm emission from neutral hydrogen in our early universe has tantalized us as a powerful probe of both cosmology and astrophysics. While the science case for 21cm cosmology, particularly during the Epoch of Reionization, is well established, the technical path toward measuring this signal has been more problematic. PAPER has recently distanced itself from its competitors, applying major technical breakthroughs to set the first physically meaningful upper limits on 21cm emission during reionization, and improving those limits a year later to show the presence of significant early heating. Even as PAPER's final season is under analysis, we are re-tooling our array to become HERA. New 14-m dishes are replacing PAPER's smaller elements, giving HERA the sensitivity to drive beyond the detection phase of 21cm cosmology, into the exciting era of data-driven modeling. The results will revolutionize our understanding of galaxy and star formation and even improve upon CMB cosmology.