The Obscured Universe

09/18/2020 - 3:30pm to 4:30pm
Speaker(s) / Presenter(s): 
Caitlin Casey (UT-Austin)
Although rare in the nearby Universe, galaxies with extraordinary star-formation rates (100-1000x the Milky Way at >100 Msun/year) represent the typical massive galaxy in the early Universe ~10 billion years ago.  These galaxies’ high star-formation rates are predominantly obscured by dust which re-radiates >95% of the energy from young stars in the (sub)millimeter/far-infrared, hence they are often called dusty star-forming galaxies (DSFGs).  Despite the fact that Earth’s atmosphere is largely opaque to the wavelengths of light where such systems are easily detected, we have successfully mapped (over the past twenty years) the contribution of such DSFGs to cosmic star-formation over an 11 billion year old history, where it appears they are factors of 1000x more common than they are locally and indeed appear to dominate. We still don’t know how prominent the population is at earlier times, when the formation of dust becomes a much more difficult problem to solve cosmologically, given the short period of time since the Big Bang.  I will discuss some unusual aspects of the observations of some of the early Universe’s most extreme galaxies, how they differ from “normal” galaxies that one might detect in, e.g., the Hubble Deep Field, and describe ways in which they push the boundary of our understanding of the astrophysics of galaxy formation.
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