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2018 Fall Science Colloquia

How Do Galaxies Evolve into the Forms They Have Today?

Presented by: Susan Kassin (Space Telescope Science Institute)
Category: Science Colloquia   Duration: 1 hour   Broadcast date: November 07, 2018
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Abstract: This talk will summarize my recent observations of disk and spheroidal galaxies, which challenge and enrich our pictures of how they form. I will show how the internal kinematics of star-forming galaxies, measured from Keck spectroscopy and Hubble images, evolve across a range of redshifts (0 to 2.5) and galaxy stellar masses. These observations demonstrate that Milky Way mass galaxy disks followed a tempestuous path to settling ino their currently well-ordered states. Star-forming galaxies at high redshifts are only just assembling. They are kinematically disordered and gradually settle over billions of years into ordered rotationally supported systems on the Hubble Sequence. Low mass galaxies today are kinematically disordered. They struggle to form disks if their masses are below 10^9.5 solar masses, a characteristic mass for disk formation. From measurements of the star-formation histories of spheroidal galaxies, we find that the timescales of spheroidal assembly and quenching evolve with time and galaxy mass. Their evolution is faster at higher redshift and higher mass. Finally, I will show how JWST spatially-resolved spectroscopy is poised to reveal the dynamical state of galaxies soon after reionization.

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Susan Kassin Tenure Presentation on Galaxy Evolution PowerPoint (.ppt)