CTC Seminar for 2023-10-11

Series: CTC Seminar
Date: Wednesday 11-Oct-2023
Time: 11:30-12:30 pm
Location: PSC 1136
Speaker: Viraj Pandya (Flatiron CCA)
Title: Galaxies Going Bananas: The Surprising 3D Geometry of High Redshift Dwarf Galaxies from JWST

Abstract I will present surprising observational results on the 3D geometry of high-redshift star-forming galaxies based on JWST-CEERS Early Release Science data. Using a novel differentiable Bayesian model with Hamiltonian Monte Carlo, I will show that there are many more flat, elongated dwarf galaxies than there are round, circular dwarf galaxies seen in projection in the early Universe. This puzzle can only be explained if ~50-80% of high-redshift dwarfs are not axisymmetric (oblate) disks or spheroids. Instead, they must be significantly flattened in two directions either as prolate ellipsoids (i.e., cigars) or as oval (triaxial, i.e., surfboard-shaped) disks. These findings imply that galactic disks settle not only in thickness but also from oval to more circular shapes with time. Both prolate and triaxial ellipsoids trace out a "banana" on the projected b/a-log(a) diagram with an excess of low b/a (edge-on) and deficit of high b/a (round) objects as observed. The stellar masses of these objects are such that they would be the progenitors of galaxies like the Milky Way, implying that our own Galaxy may have gone through a prolate/triaxial phase in its past. Exploratory comparisons of high-probability prolate and oblate candidates reveal that the two are remarkably similar in terms of many properties except for dust and kinematics, which may be the key to distinguishing between these two types of 3D geometry. I will rule out selection effects, consider follow-up prospects and discuss theoretical implications for both galaxy formation and cosmology.

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Past CTC Lunch seminars.
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