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Department of Astronomy pres.

Astronomy Colloquium Series Presents

Dr. Sean Johnson, Hubble Fellow and joint Carnegie-Princeton Fellow, Department of Astrophysical Sciences, Princeton University

Dr. Sean Johnson Dr. Sean Johnson
Dr. Sean Johnson
Galaxy feeding and feedback in emission and absorption across cosmic time

In modern models, galaxy growth is regulated by gas accretion from the intergalactic medium (IGM) and feedback from supernova and AGN driven winds. The low-density halo gas around galaxies known as the circum-galactic medium (CGM) is at the nexus of these baryon cycles and represents both a dominant reservoir for fueling future growth and a fossil record of past feedback. Advancing our physical understanding of galaxy evolution, therefore, requires observations of the gas cycles between the interstellar medium (ISM), CGM, and IGM in emission and absorption across cosmic time. I will review three recent/on-going surveys that provide unique insights into the gas flows in and around galaxies through the combination of multi-wavelength datasets from Hubble, Magellan, VLT, and Chandra/XMM. These surveys demonstrate that: (1)  Metal-enriched gas around low-redshift galaxies is predominantly confined to galaxy halos -- even in the shallow-potential wells of low-mass star-forming dwarfs. (2) Galaxy interactions play a key role in distributing gas from the ISM to the CGM while also likely triggering black hole growth. And (3) the putative hot wind component of AGN outflows is dynamically unimportant in a prototypical galactic-scale AGN superwind. Each of these results represents a surprising first glance from on-going surveys that will expand dramatically over the next five years and with the advent of new instrumentation on Magellan, JWST, and the E-ELT.

Please note: Should you require any reasonable accommodations to ensure equal access and opportunity related to this event please contact Stacy Tiburzi at 734-764-3440 or

Tea will be served beforehand from 3:00-3:30pm in Serpens.

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