Predoctoral Projects, 2015

Project Title: Physical Conditions in Infrared-Luminous Galaxies

Project Advisor: Dr. Matthew L. N. Ashby

Background: The far-infrared regime reflects the processes responsible for heating dust, including both star formation and deeply embedded active galactic nuclei (AGNs). We are going to use the spectral energy distributions (SEDs) of a large set of star-forming galaxies to tease apart the different sources of energy that make them glow in the far-infrared. New data from the Herschel mission will be of particular use for this purpose, not just because of their use for constraining the thermal continuum emission, but also for their ability to detect two molecular species of special interest: H2O and OH. Scientific Questions: we hope to analyze the new and high-quality Herschel spectroscopy to better understand how physical conditions in infrared-luminous galaxies depend on star formation activity, stellar masses, merger stage, and other measureables. By examining these trends we will learn much about how star formation proceeds in the bright, nearby galaxies for which we have so much new data. One of our goals is to test the reality of the two-mode scheme commonly used to describe star formation (bursty and quiescent). Methodology: we will use a state-of-the art radiative transfer code to model multiple molecular transitions -- both line intensities and profiles -- over a wide range of species and excitation conditions. We believe that the galaxies can be organized broadly into groups that broadly share certain conditions, but this is far from being demonstrated. We anticipate proposing for followup observations with SOFIA.

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Clay Fellow Warren Brown