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   Research Interests:
Galaxy Feedback

Possibly the most important, but least well-understood, aspect of galaxy formation is the role of feedback on both the galaxy itself and its environs and neighbors. This feedback can take many aspects:

  • Winds and Metal Enrichment: The IGM is enriched with heavy elements via winds from star-forming galaxies. I am mostly concerned with studying observable consequences of these processes. For example, the images at the right show emission from the local universe in a UV doublet of OVI. Emission comes from warm (T~100,000 K), highly enriched gas - galactic winds and the centers of galaxy groups, for the most part. Observations of this line therefore provide information on the history of galactic winds. Absorption lines from similar transitions have already provided some information on the enrichment pattern; when these studies are extended to higher-redshift, they will tell us about the earliest IGM enrichment, which is crucial for understanding the first galaxies.

  • Photoheating: During reionization, the IGM is rapidly heated to T~10,000 K. The increased thermal pressure has important consequences for structure formation, because it prevents gsa from accreting onto galaxies as well as filaments and other gas clumps. The dynamical effects of this sudden heating, as well as its effects on the geometry of reionization, remain poorly understood.

  • Other Radiation Backgrounds: Before reionization, other radiation backgrounds can also affect the IGM and galaxy formation. X-rays heat the IGM, reducing clumping. Ultraviolet photons destroy molecular hydrogen, but X-rays catalyze its formation. The complicated net effects of these mechanisms must still be sorted out.