ASD Colloquium Series - Fall 2022
ASD Colloquium Series - Fall 2022
The Astrophysics Science Division colloquia occur on Tuesdays at 3:45 pm in a Hybrid format. For in person attendees, the colloquia will be held in building 34, room W150 (unless otherwise noted), with an opportunity to meet the speaker at 3:30 pm. Virtual attendees should use connection information in the calendar invites.
Schedules from past colloquium seasons are available.
Contact: Scott C. Noble
September |
|
|---|---|
| Sep 13 | No Colloquium |
| Sep 20 | The Proposed STAR-X MIDEX Mission: Studying The Fast, Furious and Forming Universe Dr. Ann Hornschemeier Cardiff (NASA GSFC) |
| Sep 27 | No Colloquium |
October |
|
| Oct 4 | Revealing the Star Formation History of Our Solar Neighborhood Catherine Zucker (Space Telescope Science Institute) |
| Oct 11 | No Colloquium - Indigenous People's Day Weekend |
| Oct 18 | No Colloquium - Postoned until April 4, 2023 |
| Oct 25 | No Colloquium |
November |
|
| Nov 1 | Searching for Gravitational Wave from Binary Mergers in LIGO and Virgo's 3rd and 4th Observing Runs Rebecca Ewing (Department of Physics, Penn State University) |
| Nov 8 | No Colloquium - Election Day |
| Nov 15 | Cosmology and astrophysics with the Atacama Cosmology Telescope, Simons Observatory, and CCAT-prime Eve Vavagiakis (Department of Physics, Cornell University) |
| Nov 22 | No Colloquium - Thanksgiving Week |
| Nov 29 | Special Time: 12:00-1:00 pm The Science Performance of JWST Jane Rigby (Observational Cosmology Lab, NASA GSFC) |
December |
|
| Dec 6 | New Phenomena in Ultralight Dark Matter Nathan Musoke (Department of Physics and Astronomy, University of New Hampshire) |
| Dec 13 | Special Location: B34, W305 Quasar Microlensing as a Powerful Tool David Pooley (Department of Physics and Astronomy, Trinity University) |
| Dec 20 | No Colloquium - Winter Holidays |
| Dec 27 | No Colloquium - Winter Holidays |
Preview the Spring 2023 season.
Abstract
STAR-X is a GSFC-led MIDEX mission that was proposed to NASA HQ in December 2021 and that was recently (August 2022) selected for competitive Phase A study. Comprising an X-ray Telescope (XRT) provided by GSFC and MIT, a UV Telescope (UVT) provided by the University of Colorado, and a spacecraft provided by Ball Aerospace, STAR-X is designed to conduct time-domain surveys and to respond rapidly to transient events discovered by other observatories such as LIGO, Rubin/LSST, Roman/WFIRST, and SKA. STAR-X is a timely response to Astro2020's recommendation for a space-based, sustaining time-domain and multi-messenger program. The science theme for the mission is “to study the fast, furious and forming Universe.” The “Fast” theme covers transients such as supernova shock breakouts, electromagnetic radiation from neutron star-neutron star mergers detected by ground-based gravitational wave detectors and stellar flares that affect exoplanet atmospheres. The “Furious” theme covers large and rapid amounts of accretion onto black holes, so as to understand rapid black hole growth at earlier times in our Universe, and involves study of Tidal Disruption Events of stars around black holes and time-domain reverberation studies of accretion disk geometry. The third pillar, “Forming”, concerns the growth of large scale structure in the Universe, covering the growth of massive galaxy clusters from their epoch of formation at z>3 to their ongoing growth from the filaments of the cosmic web at the current time. This talk will cover the mission architecture, performance, and the science case.
Abstract
Given its proximity, the solar neighborhood has long been considered a fundamental laboratory for understanding how stars form. However, until very recently, this understanding was largely based on static ''plane of the sky'' views, making it extraordinarily challenging to build a 3D physical picture of gas and young stars using 2D integrated quantities. In this talk, I will discuss how new 3D spatial and dynamical constraints from Gaia, in combination with new data science and visualization techniques, have transformed our understanding of star formation near the Sun. In particular, I will show how ''3D dust mapping'' has provided never-before-seen 3D spatial views of the interstellar medium: redefining the structure of the Local Arm of the Milky Way, giving rise to previously undiscovered superbubbles, and constraining the detailed morphologies of individual molecular clouds at 1 pc resolution. Combining 3D dust mapping with the 3D space motions of young stars, I will show how we can reconstruct the star formation history of the solar neighborhood over the past 20 Myr, and in doing so, explain the origin of all nearby star formation as being driven by the expansion of the Local Bubble. I will conclude by discussing new opportunities with Gaia DR3, as well as the implications of our results for the theory and simulation communities.
Abstract
SWhen Einstein predicted gravitational waves as a solution to the linearized field equations he never expected that they would be detectable in practice. We now know that compact binary coalescences, mergers of black holes and neutron stars, are powerful emitters of gravitational waves and almost 100 such signals have been observed to date. The field of gravitational wave detection has undergone tremendous growth in only a few years. In this talk I will discuss the principles of gravitational wave detection with matched filtering. I will then give a broad overview of some of the most exciting detections made by the LIGO/Virgo/KAGRA Collaboration in its first three observing runs. Finally, I will share some of my own work on testing the end-to-end gravitational wave detection system using simulated signals. This work allows for real time feedback on the accuracy of science outputs produced by gravitational wave search pipelines, which was never available in previous observing runs.
Abstract
Rapid developments in microwave instrumentation and low temperature detectors over the past decade have provided a wealth of arcminute-scale cosmic microwave background (CMB) data. These measurements help define our standard cosmological model and shed light on the evolution of the structures in our universe. I will present recent results from the Atacama Cosmology Telescope (ACT) and discuss how our high resolution CMB maps are at the frontier of SZ science. I will also discuss the status of first light instruments for the CCAT Observatory and the Simons Observatory. Along with new data from ACT, these experiments will provide unparalleled millimeter and submillimeter measurements that will test cosmological models and open new windows on galaxy evolution and fundamental physics.
Abstract
Now in science operations, JWST is the most powerful infrared telescope ever built. I will present the quantitative science performance of JWST, as measured during the grueling six month commissioning period, which demonstrates that JWST is fully capable of achieving the discoveries for which it was built. Almost across the board, JWST's science performance is better than expected. I will attempt to characterize both the breadth and the depth of the JWST science program, and will dwell on the power of coupling JWST to cosmic telescopes, also known as gravitational lenses, which is my own research focus and the subject of two Early Release Science programs. I'll fold in a few human stories from commissioning, on how we got this beast working, and celebrate the people --- ~20,000 people who built it, ~600 who commissioned it --- whose collective efforts have created a revolutionary observatory now in its first of many years of scientific discovery.
Abstract
In this talk, I will discuss ultralight dark matter (ULDM), an alternative to cold dark matter (CDM) that has attracted much recent attention. While ULDM's large scale structure is similar to CDM, it differs on small scales. I will introduce and motivate dark matter, then introduce ultralight dark matter and its unique signatures. I will finish by presenting two new explorations of structure formation in ULDM:
1. Self-interactions in ULDM affect the efficiency with which small dark matter halos are tidally stripped.
2. Rotation in ULDM can manifest as vortices. These vortices are generically unstable, but gravitational effects from supermassive black holes may cause them to persist indefinitely.
Abstract
X-ray observations of quadruply gravitationally lensed quasars have a unique power to address several fundamental astrophysical issues. I will give an overview of some aspects of gravitational lensing of quasars, including the strong gravitational lensing by an intervening galaxy and the further micro-lensing by stars in the lensing galaxy, and discuss how Chandra observations of quadruply gravitationally lensed quasars conclusively demonstrated that micro-lensing is occurring. Once established, microlensing was used as a tool, and Chandra observations were used to (1) place constraints on the sizes of quasar accretion disks, (2) determine how much of the lensing galaxies' matter content is in a smooth component and how much is composed of compact masses (e.g., stars, stellar remnants, primordial black holes, dark matter sub-halos, and planets), and (3) calibrate the fundamental plane, providing a measurement of the stellar mass-to-light ratio, a fundamental astronomical quantity and something nearly impossible to measure beyond the solar neighborhood through any other means. I will present results of new observations and discuss exciting possibilities for the future.