Astrophysics Brown Bag Lunch Talk 11/21/2022: Speakers: Akash Gupta (UCLA) And Keunho Kim (University Of Cincinnati)

Monday November 21, 2022 12:00 pm

In Person in Marlar and/or Virtual Brown Bag Lunch 
Monday November 14, 2022 at 12:00 Link Below
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Presentation in Marlar 37-252/37-272 for those wishing to attend in person

Akash Gupta, UCLA  at 12:05 (in person)

Unraveling the origin of super-Earths and sub-Neptunes

Abstract:   One of the most profound findings from NASA’s Kepler mission is the unexpected dearth of close-in exoplanets of sizes 1.5 to 2.0 Earth radii – known today as the radius valley. This valley divides the population of the most abundant class of planets yet known, those between the sizes of Earth and Neptune, into (1) super-Earths: small planets with Earth-like bulk compositions and (2) sub-Neptunes: large planets with hydrogen-rich atmospheres or ice-rich interiors. In this talk, I will present how atmospheric mass-loss driven by the cooling luminosity of a planet and its host star’s bolometric luminosity, i.e., the core-powered mass-loss mechanism, can explain the origin of this radius valley. I will describe the key physical processes that drive this mechanism, the unprecedented insights this theory gives into the exoplanets we are observing today and the testable predictions we make as a function of planet and host-star properties.

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Keunho Kim, University of Cincinnatti at 12:30 pm (in person)

How LyC photons escape from compact star-forming regions in the Sunburst galaxy

Abstract:  The escape mechanism of ionizing (LyC) photons from a galaxy’s star-forming regions to intergalactic space is crucial to understanding the reionization process of the early universe. We investigate the characteristics of a compact star-forming complex with leaking LyC photons in the gravitationally lensed Sunburst galaxy at z=2.4. This galaxy provides unique opportunities to probe the physics of LyC escape down to tens of parsecs by utilizing HST’s high angular resolution and the lensing magnification. We measure the key physical quantities of the leaking complex including UV slope, Lyá, Hâ, and oxygen ([O II] and [O III]) emission lines based on HST images. We find remarkably blue UV slopes (< -2.5) in the multiply magnified regions of the leaking complex, which is bluer than those of star-forming galaxies and non-leaking regions in the galaxy. I will discuss how LyC radiation escapes from a particular compact star-forming region within a galaxy and the implications on the localized escape mechanisms from star-forming galaxies.


Event Contact

Josh Borrow