2020
KICP Seminar: Weishuang Linda Xu (Harvard)
12:00–1:00 pm Zoom Room
Weishuang Linda Xu, Harvard, “Thermal Dark Sectors in the Early and Late Universe”
A&A Colloquium: Eric Agol (University of Washington)
3:30–4:30 pm Zoom - for link, please contact, Laticia Rebeles, lrebeles@oddjob.uchicago.edu
“Quantifying the nature of the TRAPPIST-1 planetary system”
Seven Earth-sized planets have been found to transit the
Jupiter-sized star TRAPPIST-1, located forty light years from
our Solar System. The planets appear to form a chain of orbital
resonances, attributed to orbital migration. Dynamical interactions
amongst the planets lead to transit-timing variations which we
measured with high precision using the Spitzer, Kepler, Hubble,
and ground-based telescopes over four years. Analysis of these
data yield a comprehensive picture of the architecture of the orbits
and interiors of these planets. The planets’ orbits are nearly circular
and coplanar, as expected from disk migration models. Their densities
show a pattern consistent with a single interior composition,
which is offset from the rocky planets in our Solar System.
I will present these and other results based on our transit-timing
and photodynamic analysis of this benchmark planetary system,
and discuss prospects for study of this system with the James
Webb Space Telescope.
A&A Colloquium: Gordan Krnjaic (Fermilab)
3:30–4:30 pm Zoom
From ALPs to WIMPZILLAS: Discovering Dark Matter In Novel Laboratories
Although the astrophysical evidence for the existence of dark matter is overwhelming, its microscopic properties remain elusive, despite decades of dedicated searches for the dominant weakly-interacting massive particle (WIMP) paradigm. In light of this experimental situation, there has recently been a surge of activity to broaden the search program by utilizing previously overlooked strategies, which leverage novel terrestrial and cosmic laboratories to probe dark matter beyond the WIMP framework. I will survey some of these ideas and present a road map towards greatly expanding our converge of well-motivated dark matter models that sample the full range of viable candidate masses.
Study Week/Thanksgiving Break
Through November 27, 2020
Graduate Admissions Information Session
11:00 am–4:30 pm Online
The Department of Astronomy and Astrophysics invites you to join us in a virtual workshop regarding the graduate admissions process. Registration Deadline: November 16, 2020.
Troubleshoot: Walking Through the Steps to Success
7:00–8:00 pm Zoom Room
Please join us tonight for the pilot program of our new Art/Science Connection outreach initiative: a conversation between UChicago scientists and the Arts+Public Life Artists-in-Residence. Hosted by KICP Director Rocky Kolb.
KICP Colloquium: Laurence Perreault Levasseur (U of Montreal)
3:30–4:30 pm Zoom Room (online)
Laurence Perreault Levasseur, U of Montreal, “Strong Gravitational Lensing and Machine Learning in the Era of Large Sky Surveys”
Tuesday Lunch Seminar: Ani Chiti (MIT), "An extended halo around an ancient dwarf galaxy"
12:00–1:00 pm Zoom
The Milky Way is surrounded by dozens of ultra-faint dwarf galaxies. These systems are the remnants of some of the earliest galaxies as suggested by their ancient (~13 Gyr) and chemically primitive stellar populations. In this talk, I will present the detection of extremely metal-poor stars ([Fe/H] < -3.0) out to 9 half-light radii in one such galaxy, Tucana II. This is the first detection of a population of stars outside the core region (~4 half-light radii) of any ultra-faint dwarf galaxy. These distant stars are, on average, more metal-poor than the central population (<[Fe/H]>=-3.0 vs. <[Fe/H]>=-2.6) and suppress the mean metallicity to <[Fe/H]> ~ -2.77. This difference is the first evidence of a metallicity gradient in an early galaxy remnant and suggests Tucana II, and perhaps other ultra-faints, plausibly were influenced by early, strong feedback episodes or a galactic merger. Such distant stars also imply that Tucana II harbors a massive, spatially extended dark matter halo (> 10^7 solar masses out to 1 kpc). Collectively, these results suggest that key factors needed for understanding early galaxy formation and chemical evolution lie in the outskirts of these small, relic galaxies and may have been missed by previous observational studies. I will thereby also present an upcoming photometric survey of all southern-hemisphere ultra-faint dwarf galaxies that will reveal any spatially extended stellar populations, which our results suggest is necessary to understand the early evolution of these relic systems.
KICP Seminar: Brittany Kamai (University of California Santa Cruz and Caltech)
12:00–1:00 pm Zoom Room
Brittany Kamai, University of California Santa Cruz and Caltech, “Envisioning and Creating the Future of Gravitational-wave Astrophysics”
A&A Colloquium: Tonia Venters (Goddard)
3:30–4:30 pm Zoom - for link, please contact, Laticia Rebeles, lrebeles@oddjob.uchicago.edu
“Multimessenger Astronomy with POEMMA”
Abstract: The highest energy cosmic rays are the messengers of the most extreme physics in the cosmos; however, efforts to identify their origins have thus far been thwarted by the fact that they don’t point back to their sources. On the other hand, interactions between ultra-high energy cosmic rays (UHECR) and the lower energy particles that they encounter either within their sources or over the course of their cosmic journey will give rise to high-energy neutrinos. The Probe of Extreme Multi-Messenger Astrophysics (POEMMA) is a space-based probe-class mission concept for measuring ultra-high energy cosmic rays (UHECRs) and detecting high-energy cosmic neutrinos via fluorescence and optical Cherenkov signals from their extensive air showers. Using a stereo configuration of two satellites, POEMMA will perform precision measurements for UHECRs above 20 EeV, providing a significant increase in statistics at the highest energies and exposure over the entire celestial sky. POEMMA will also search for Cherenkov signals from tau neutrinos above 20 PeV converting in the Earth near the limb. POEMMA’s design will also feature the capability to slew by as much as 90 degrees in 500 s, allowing for rapid response to target-of-opportunity alerts. We discuss the prospects for multimessenger astronomy with POEMMA, including cross-correlation UHECR anisotropy searches, the detection of the diffuse astrophysical neutrino flux at greater than PeV energies, and the search for high-energy neutrinos associated with transient astrophysical phenomena.