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TAP Colloquia on YouTube

TAP - University of Arizona

TAP - University of Arizona
YouTube Video VVVnalEtOEJOZVZrWklHUDlnMndTQkRRLjh1RUU1VWdKeVdj Talk Title: Origin of moons in the solar system and beyond Talk Abstract: The Apollo lunar samples reveal that Earth and the Moon have strikingly similar isotopic ratios, suggesting that these bodies may share the same source materials. This leads to the "standard" giant impact hypothesis, suggesting the Moon formed from a disk that was generated by an impact between Earth and a Mars-sized object. This disk would have had high temperature (~ 4000 K), and its silicate vapor mass fraction would have been ~ 20 wt %. However, impact simulations indicate that this model does not mix the two bodies well, making it challenging to explain the similarity. In contrast, recent studies suggest that more energetic impact models that produce higher vapor mass fractions (~ 80-90 wt%) could mix the two bodies, naturally solving the problem. However, these energetic models may have a challenge during the Moon accretion phase. Our analyses suggest that km-sized moonlets experience a strong gas drag from the vapor portion of the disk and fall onto Earth on a very short timescale. This problem could be avoided if large moonlets ( greater than 1000 km) form very quickly by the process called streaming instability. We investigate this possibility by conducting numerical simulations. We will discuss implications of this study for moons in the solar system and extrasolar systems (exomoons). We will also briefly describe our ongoing work on terrestrial craters (Vredefort and Sudbury impact basins) as well as shock experiments at the Laboratory of Laser Energetics at the University of Rochester. BIO: Miki comes to us from the University of Rochester where she is currently an Assistant Professor, Earth and Environmental Sciences with a secondary appointment in Physics and Astronomy and Laboratory for Laser Energetics. She was a Postdoctoral Fellow at the Carnegie Institution for Science and received her Ph.D. and M.Sc. in Planetary Science from the California Institute of Technology, an M.Sc. in Earth and Planetary Sciences from the Tokyo Institute of Technology, and participated in an Exchange Program in Astronomy and Astrophysics at the University of California, Santa Cruz.
Talk Title: Origin of moons in the solar system and beyond Talk Abstract: The Apollo lunar samples reveal that Earth and the Moon have strikingly similar isotopic ratios, suggesting that these bodies may share the same source materials. This leads to the "standard" giant impact hypothesis, suggesting the Moon formed from a disk that was generated by an impact between Earth and a Mars-sized object. This disk would have had high temperature (~ 4000 K), and its silicate vapor mass fraction would have been ~ 20 wt %. However, impact simulations indicate that this model does not mix the two bodies well, making it challenging to explain the similarity. In contrast, recent studies suggest that more energetic impact models that produce higher vapor mass fractions (~ 80-90 wt%) could mix the two bodies, naturally solving the problem. However, these energetic models may have a challenge during the Moon accretion phase. Our analyses suggest that km-sized moonlets experience a strong gas drag from the vapor portion of the disk and fall onto Earth on a very short timescale. This problem could be avoided if large moonlets ( greater than 1000 km) form very quickly by the process called streaming instability. We investigate this possibility by conducting numerical simulations. We will discuss implications of this study for moons in the solar system and extrasolar systems (exomoons). We will also briefly describe our ongoing work on terrestrial craters (Vredefort and Sudbury impact basins) as well as shock experiments at the Laboratory of Laser Energetics at the University of Rochester. BIO: Miki comes to us from the University of Rochester where she is currently an Assistant Professor, Earth and Environmental Sciences with a secondary appointment in Physics and Astronomy and Laboratory for Laser Energetics. She was a Postdoctoral Fellow at the Carnegie Institution for Science and received her Ph.D. and M.Sc. in Planetary Science from the California Institute of Technology, an M.Sc. in Earth and Planetary Sciences from the Tokyo Institute of Technology, and participated in an Exchange Program in Astronomy and Astrophysics at the University of California, Santa Cruz.
Title: Testing Galaxy Formation Models with Large-scale Surveys of the Milky Way Stellar Halo Abstract: While the vast majority of the light from our galaxy comes from the Galactic disk, the vast majority of the mass of the Milky Way (MW) is in its dark matter halo. Because we cannot directly observe the MW's dark matter halo, we must use luminous tracer populations (i.e., stars) to study the mass distribution indirectly. Fortunately, there are stars strewn throughout the MW's dark matter halo. We believe the MW built up its halo of dark matter over cosmic time by consuming smaller dwarf galaxies; the remnants of these dwarf galaxies make up the MW's stellar halo. Halo stars can therefore be used both to constrain the dark matter distribution of the MW as well as inform us about the dwarf galaxies in which they formed. I will present my ongoing theoretical and observational work using halo stars to map the dark matter distribution and disequilibrium in the MW, as well as study the faint, low-mass galaxies that were consumed by the MW during its formation. I will discuss the crucial roles of current and upcoming large-scale surveys of the MW halo (such as the Rubin Observatory Legacy Survey of Space and Time) for addressing fundamental questions in galaxy formation. Bio: Dr. Emily Cunningham is a NASA Hubble Fellow at Columbia University. She completed her Ph.D. in the Department of Astronomy & Astrophysics at UC Santa Cruz, working with Alis Deason, Raja Guhathakurta and Connie Rockosi. Before starting at Columbia this fall, she was a Flatiron Research Fellow at the Center for Computational Astrophysics, collaborating in the Dynamics Group and the Astronomical Data Group.
Talk Title: Revealing the origin of binary black holes with spin precession Abstract: In a binary black hole (BBH) system, spins misaligned with the orbital angular momentum L will generically induce both precession and nutation of L about the total angular momentum J. These phenomena modulate the phase and amplitude of the gravitational waves emitted as the binary inspirals to merger. We introduce a “taxonomy” of BBH spin precession that encompasses all the known phenomenology, then present five new phenomenological parameters that describe generic precession and constitute potential building blocks for future gravitational waveform models. These are the precession amplitude θL, the precession frequency ΩL, the nutation amplitude ΔθL, the nutation frequency ω, and the precession-frequency variation ΔΩL. We then introduce a simplified model of binary stellar evolution and BBH formation to predict the values of these parameters for astrophysical systems. In Scenario A [B] of our model, stable mass transfer occurs after Roche-lobe overflow (RLOF) of the more [less] massive star, while common-envelope evolution follows RLOF of the less [more] massive star. Each scenario is further divided into Pathways 1 and 2 depending on whether the core of the more massive star collapses before or after RLOF of the less massive star, respectively. These aspects of stellar evolution leave distinctive imprints on BBH precession and nutation. In particular, nutation is a smoking-gun signature that the BBHs inherited their spins from their Wolf-Rayet progenitors instead of acquiring them through accretion or tidal synchronization. Bio: Michael Kesden received his BA in Physics from Princeton University in 2000 and his Ph.D. in Physics from Caltech in 2005. After postdoctoral fellowships at the Canadian Institute for Theoretical Astrophysics at the University of Toronto, Caltech, and the NYU Center for Cosmology and Particle Physics, he joined the faculty of the University of Texas at Dallas, where he is currently an Associate Professor of Physics and Vice Speaker of the Faculty. His recent research focuses on black-hole spin affects stellar tidal disruption by supermassive black holes and the gravitational waves emitted by binary black holes. Dr. Kesden is also deeply interested in how technology can promote physics education and outreach. He helped develop STEPP (Scaffolded Training Environment for Problem Solving), a series of educational modules to help teach introductory physics and computational thinking, and VIGOR (Virtual Interaction with Gravitational waves to Observe Relativity), an interactive simulation of binary black holes and the gravitational waves they emit. His research is supported by NSF and NASA grants and was recognized by a 2015 Alfred P. Sloan Fellowship in Physics.
Title: Collisional formation and evolution of metal-rich planetary bodies Abstract: Astronomical observations reveal that dense, likely metal-rich planetary bodies ranging in size from asteroids to super-Earth exoplanets are relatively common in the galaxy. However, it is unclear how these bodies form and evolve. In this talk, I test the hypothesis that metal-rich bodies are the cores of differentiated proto-planets which lost their silicate mantles in giant impacts. Using numerical simulations of planet formation, I show that collisions become more efficient in eroding mantle materials as the mass of the colliding bodies decreases, in agreement with the high bulk densities observed for some asteroids in the solar system. This result supports the proposal that one of the largest and most accessible metal-rich asteroids, (16) Psyche, is the core of a differentiated planetesimal. If Psyche is indeed a planetary core, its surface may exhibit areas of different metal content, ranging from remnant mantle rocks to exposed core materials and (possibly) ferrovolcanic deposits. I provide evidence in support of this observational prediction by interpreting high-resolution temperature maps of Psyche collected using the Atacama Large Millimeter Array (ALMA) in Chile. These ALMA data give insights into how metal-rich bodies form and evolve and what the NASA Psyche mission, which will explore the asteroid in the coming years, may see when it reaches its destination. Bio: Dr. Saverio Cambioni (he/him) is the Crosby Distinguished Postdoctoral Fellow at the Department of Earth, Atmospheric, and Planetary Sciences at the Massachusetts Institute of Technology (MIT). He earned his Ph.D. in Planetary Sciences at the Lunar and Planetary Laboratory of the University of Arizona, with a thesis on the application of machine learning to planetary sciences. He also holds a B.Sc. and M.Sc. in Aerospace and Space Engineering from Sapienza, University of Rome. After a period of postdoctoral research at the California Institute of Technology at MIT, he is working on machine learning applied to the study of asteroid geophysics and the role of collisions in shaping the formation of terrestrial planets and asteroids.
TITLE: How fast is the Universe expanding and why? ABSTRACT: This is one of the most fundamental questions one can ask about cosmology. The answer, however, has sparked a debate about our very understanding of the Universe and its constituents. Cosmologists can determine how fast today’s universe is expanding using several different experimental techniques. Still, the answers don’t match, leading to one of the most intriguing discrepancies in cosmology today - the Hubble tension. This talk will familiarize you with the problem and its possible origins - systematic causes are largely ruled out, leaving the exciting possibility of new physics. As a theorist, Tanvi has worked extensively on the Hubble tension and on resolving it with the introduction of ‘early’ dark energy. Tanvi will present this work, challenges that lie ahead in finding the true underlying model of our Universe, and what we might learn about the dark 95% of the Universe - dark matter and dark energy through the exercise of resolving cosmic anomalies. BIO: Tanvi is currently a postdoc at CPC at UPenn, working with Bhuv Jain and his group and Mark Trodden and his students. Before that, she was in grad school at Johns Hopkins University, where she got her Ph.D. in 2019, working with Marc Kamionkowski. Tanvi’s research is largely phenomenological cosmology. Most of her work relates to the cosmic microwave background, but she’s also interested in weak lensing, intensity mapping, and supernovae, amongst other data sets. She’s been working the theory angle on the Hubble tension for years and came up with early dark energy (a solution to the tension) in 2016. She has worked to improve DEI in Physics and Astronomy and loves exchanging ideas about that. Besides work, Tanvi loves scuba diving whenever she can afford the money and baking whenever she can afford the calories.
Title: Advancements in fundamental physics with numerical relativity simulations of charged black holes. Abstract: Charge (electric, magnetic, or any U(1) charge) is a parameter often neglected in simulations of black holes. As a result, little is known about the dynamics of charged binaries. In this talk, Gabriele will highlight the importance of understanding the non-linear interaction of charged black holes for astrophysics and fundamental physics. He will show results from fully self-consistent general-relativistic simulations of merging black holes, touching upon the challenges faced in performing such calculations and the improvements that enabled successful long-term evolution. Gabriele will discuss the general features of quasi-circular inspirals and present constraints on the charge of astrophysical black holes and deviation from general relativity obtained from the gravitational-wave event GW150914. Bio: Gabriele is a Ph.D. candidate at the Astronomy Department of the University of Arizona and a NASA Future Investigator. He received his Bachelor's and Master's degrees in Physics from the University of Milan (Italy), specializing in theoretical physics. For the past five years, Gabriele has worked with Vasileios Paschalidis on various topics in gravitational physics. His research focuses on systems with extreme gravity, such as black holes and neutron stars. Gabriele's interests include binary black hole mergers, rotating neutron stars, accretion disks, dynamical-spacetime simulations, and high-performance computing. He develops and contributes to several open-source codes.
Title: Searching for Dark Matter Interactions throughout Cosmic History Abstract: Understanding the fundamental nature of dark matter is one of the major challenges facing today's physics community. There are dedicated efforts to search for dark matter interactions with the Standard Model of particle physics, but no concrete evidence of such interactions has been observed. In this talk, Dr. Boddy will demonstrate how cosmological and astrophysical observables provide complementary information to laboratory searches. She will describe the effects of dark matter scattering in the early Universe and show constraints using data from the cosmic microwave background and the abundance of Milky Way satellites. She will also discuss the impact on 21-cm observations. Bio: Dr. Kimberly Boddy is a professor of physics in the Weinberg Theory Group at UT Austin. She is a theoretical physicist with research interests spanning various topics in cosmology, astrophysics, and particle physics. Her interests include dark matter, direct and indirect detection, the cosmic microwave background, large-scale and small-scale structure formation, halo evolution, cosmic dawn and reionization, and gravitational waves. She received her S.B. in physics from the Massachusetts Institute of Technology and her Ph.D. in physics from the California Institute of Technology. She was a postdoctoral fellow at the University of Hawaii, Manoa, and Johns Hopkins University, where she was awarded a Provost's Postdoctoral Fellowship. She became a faculty member at UT Austin in 2020.
Title: Galactic Center Science with GRAVITY at the VLT Abstract: The GRAVITY instrument at the VLT offers an unprecedented view of the region around the supermassive black hole SgrA* at the center of the Milky Way. These observations have enabled precise measurements of stellar orbits around the black hole, including detection of the gravitational redshift and the relativistic precession of the periastron of the star S2. This high level of astrometric precision strengthens the case for a black hole at the galactic center and allows for tests of General Relativity in the strong-field regime. Moreover, the stability of the measured stellar orbits on a timescale of more than two decades constrains the presence of an intermediate-mass black hole. I will discuss the recent results from the GRAVITY observations of the galactic center and their implications for the environment of SgrA*. Bio: Dr. Baubock attended Boston University as an undergraduate before going to Arizona for my Ph.D., working with Dimitrios Psaltis and Feryal Özel on the relativistic effects of rotating neutron stars. From there, he went to Germany as a postdoc at the Max Planck Institut für Extraterrestrische Physik in Reinhard Genzel’s group. Since 2021 I’ve been at the University of Illinois working with Charles Gammie on black hole accretion and the EHT.
Title: Understanding Galaxy Evolution at the Lowest Masses Abstract: Low-mass galaxies challenge our picture of galaxy formation and are an intriguing laboratory for the study of star formation, feedback, and dark matter physics. She will present results from high resolution, cosmological simulations that contain many (isolated) dwarf galaxies [the MARVEL dwarfs] as well as satellite dwarf galaxies [the DC Justice League]. Together, they create the largest collection of high-resolution simulated dwarf galaxies to date and the first flagship suite to resolve ultra-faint dwarf galaxies in multiple environments. This sample spans a wide range of physical (stellar and halo mass) and evolutionary properties (merger history). Dr. Munshi will present results and predictions constraining both star formation and dark matter physics soon testable by telescopes like JWST, Rubin's LSST, and the Roman Space Telescope. Finally, she will present the results about ultra-diffuse galaxies (UDGs) and satellite distributions around Milky Way analogs from both zoom-in simulations and from a large sample of analogs drawn from the Romulus 25-Mpc volume simulation. She will discuss the role of the environment in addition to satellite quenching times and their mechanisms with an eye toward comparing with observations. BIO: Dr. Munshi is an assistant professor at the University of Oklahoma. She received her Ph.D. at the University of Washington in 2014 and most recently was a VIDA Fellow at Vanderbilt University. Her work focuses on utilizing hydrodynamic simulations to study galaxy formation - in particular, the formation and evolution of the smallest and dimmest galaxies - in an effort to constrain the nature of dark matter.
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