Astrophysics Brown Bag Lunch Talk 10/31/2022: Speakers: Juliana García-Mejía (Harvard) And Eun-jin Shin (Seoul National University)

In Person in Marlar and/or Virtual Brown Bag Lunch 
Monday October 31, 2022 at 12:00 Link Below
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Presentation in Marlar 37-252/37-272 for those wishing to attend in person

Juliana Garcia-Mejia, Harvard University, Center for Astrophysics
at 12:05 (in person )

First Light Results from the Tierras Observatory, An Ultra-precise Time-series M-dwarf Photometer

Abstract: We have refashioned the 1.3m 2MASS telescope located at the F.L. Whipple Observatory atop Mount Hopkins, Arizona, into an ultra-precise time-series photometer: The Tierras Observatory. Tierras is designed to achieve a photometric precision of 250 ppm across an observing season. The design choices that enable this precision include a four-lens focal reducer and field-flattener to increase the field-of-view of the telescope from 0.19 deg to 0.50 deg on a side; a custom narrow (40 nm) bandpass filter centered around 863.5 nm to minimize precipitable water vapor errors known to limit ground-based photometry of M dwarfs; a deep-depletion 4k × 4k CCD with a quantum efficiency of 85% in our bandpass, operating in frame transfer mode; and, a fully automated observing mode. Tierras achieved first light in the fall of 2021, and in February 2022 we installed a new set of baffles to significantly reduce sky background. We will share recent light curves and summarize our current on-sky performance. Tierras is starting a three-year survey of M dwarf stars within 15 parsecs to detect new terrestrial planets that were too small or too cool to be found by TESS or previous ground-based efforts, and to monitor known exoplanets (both rocky and gaseous) to search for satellites or systems of circumstellar rings. Furthermore, a long term monitoring campaign will permit Tierras to determine M dwarf rotation periods, elucidating the process and timescale over which these stars lose their angular momentum.

Bio: Juliana García-Mejía is a final year graduate student at the CfA, as well as a Ford and NSF Fellow. Her research is focused on the development of novel astronomical instrumentation to enable the study of exoplanets, M dwarfs, and eventually the search for signs of life on other planets. She is the PI of The Tierras Observatory, a new 1.3m ultra-precise fully-automated photometric observatory located atop Mt. Hopkins, Arizona. She is also a co-investigator in the FIOS project, a Fabry-Perot instrument designed for use on the Giant Magellan Telescope to detect oxygen in exoplanet atmospheres. Juliana is invested in promoting equity and inclusion within Astronomy and STEM, with particular attention towards engaging young Latin-American students with the millenary question of whether life exists elsewhere in the Universe.

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Eun-jin Shin, Seoul National University at 12:30 pm (remote)

Star-formation variability as a probe for the baryon cycle within galaxies

Abstract: We present new results on the connection of the regulation of star formation and the cycling of baryons in-and-out and within galaxies. We use idealized numerical simulations of Milky Way-mass galaxies, in which we vary the stellar feedback strength and morphological setup (B/T ratio). Tracking individual gas parcels for 250 Myr, we analyze the gas cycle within the various galaxies and quantify how gas moves and oscillates through the different phases of the interstellar medium and forms stars. We then put forward how the variability of star formation can be used as a probe of the baryon cycle within galaxies by investigating the temporal and spatial power spectrum density (PSD) of the star formation history (SFH). We conclude that observations of the temporal and spatial PSD of the SFH enable us to shed new light onto the baryon cycle and the star-formation process.

Bio: I am a PhD candidate working in my fifth year with Ji-hoon Kim at Seoul National University. My research focuses on star formation and baryon cycles under various galactic circumstances, including isolated and merging galaxies. Participating in the AGORA code comparison project I investigated how the metallicity evolve in galaxies with different hydrodynamic simulation codes. Also, I’ve studied a formation scenario of dark matter-deficient galaxies and predicted the observational properties of collision-induced dark matter deficient galaxies.



Event Contact

Josh Borrow