List of Past Astronomy Colloquia : 01-Jan-2023 to 01-Jun-2023

Date:   Wednesday 01-Feb-2023
Speaker:   Dr. Meredith MacGregor (Colorado University)
Title:  How to Form a Habitable Planet

Planets form from disks of dust and gas surrounding young stars. As they grow, these new planets inherit their chemical composition from the surrounding material and then sculpt it through gravitational interactions to form gaps and other asymmetric structures. In the last decade, the Atacama Large Millimeter/submillimeter Array (ALMA) has revolutionized our ability to study planet formation, allowing us to examine this process in high resolution. I will present highlights from ongoing work using ALMA and other facilities that explores how planetary systems form and evolve by (1) connecting disk structure to sculpting planets and (2) understanding the impact of stellar flares on planetary habitability. Together these results provide an exciting foundation to investigate the evolution of planetary systems as a whole through multi-wavelength observations. In the future, new facilities, specifically in the far-infrared, will help complete our understanding by tracing the chemistry of water and other volatiles critical for life.

Date:   Wednesday 08-Feb-2023
Speaker:   Dr. Shmuel Bialy (University of Maryland)
Title:  How do stars shape interstellar gas? cosmic rays -- supernova -- UV radiation

Stars form in interstellar clouds through gravitational collapse. Once the stars form, they begin injecting energy back into the interstellar medium, which regulates the next-generation star-formation process. In this talk, I will review key aspects of this feedback process, focusing on the interaction of supernovae, cosmic rays, and far-UV radiation with interstellar clouds. I will discuss our recent discovery of the "Per-Tau Shell", a gigantic 3D shell of gas and dust in the solar vicinity, that is actively forming new stars. This provides the first 3D observational evidence for the constructive aspect of supernovae, where instead of destroying clouds, supernovae promote cloud condensation and trigger the formation of a new generation of stars. Supernovae are also the dominant sites of acceleration of cosmic rays. I will discuss a new way of constraining the cosmic-ray interstellar spectrum at low energies (E

Date:   Wednesday 15-Feb-2023
Speaker:   Dr. Cecilla Chirenti (University of Maryland)
Title:  Finding hypermassive neutron stars, or The adventures of a theoretical physicist in gamma-ray data analysis

Gamma ray bursts (GRBs) are the most luminous electromagnetic events in the universe. Short GRBs, typically lasting less than 2 seconds, have already been associated with binary neutron star (BNS) mergers, which are also sources of gravitational waves (GWs). The ultimate fate of a BNS, after coalescence, is usually expected to be a black hole (BH) with 2-3 solar masses. However, numerical relativity simulations indicate the possible formation of a short-lived hypermassive neutron star (HMNS), lasting for tens to hundreds of milliseconds after the BNS merger and before gravitational collapse forms a BH. The HMNS is expected to emit GWs that will be detectable by third generation ground-based GW detectors in the 2030s. I will present results from a recent analysis that revealed evidence for HMNSs using gamma-ray observations obtained in the 1990s with the Compton Gamma Ray Observatory.

Date:   Wednesday 22-Feb-2023
Speaker:   Dr. Sultan Hassan (NYU)
Title:  Extracting all information from future surveys

Extracting the maximum amount of astrophysical and cosmological information remains a challenge in the current and future surveys. These include, for instance,the recently launched NASA’s James Webb Space Telescope (JWST), the Euclid, the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx), the Nancy Grace Roman Space Telescope (Roman), Square Kilometre Array (SKA), and many more. Due to the unprecedented sensitivity and large field of view, future surveys will enable detecting the majority of high redshift sources (quasars and galaxies) responsible for reionization on extremely large scales (> Gpc). Hence, a new generation of theoretical models and techniques is required to maximize the scientific return of these future surveys. In this talk, I will briefly discuss the key questions about the nature of reionization and the various different probes. I will also discuss uncertainties in our current theoretical models and the progress that has been made to answering these questions. I will then present some of my own contributions to improve modeling reionization using a combination of state-of-the-art simulations and machine learning techniques. I will conclude by summarizing my current and future research directions, research group philosophy, and vision to promote diversity, equity and inclusion at the University of Maryland.

Date:   Wednesday 01-Mar-2023
Speaker:   Dr. Ariadna Murguia-Berthier (Northwestern University)
Title:  The fate of the merger remnant in GW170817 and its imprint on the jet structure

On August 17, 2017, LIGO/Virgo detected the first gravitational waves from merging neutron stars. This event, known as GW170817 was accompanied by observations all over the electromagnetic spectrum. The peculiar gamma-ray burst that followed the merger in GW170817, is unlike any gamma-ray burst observed before. In order to explain the afterglow observations, there is a need for the jet launched after the merger to have structure, which is a natural consequence of the interaction of the jet with the ambient medium. In this talk, I will show special relativistic simulations of the interaction of the jet with several outflows launched during the merger and compare the simulations to the observation. I will then use the results in order to constrain key properties of the merger, such as the delay time between the merger and the collapse to a black hole.

Date:   Wednesday 08-Mar-2023
Speaker:   Dr. Alberto Bolatto
Title:  The Inner Workings of Starbursts

Starbursts are a rare phenomenon in the present day universe, but they represent perhaps the most common mode under which stars form and galaxies grow during the z~1-2 peak of cosmic star formation activity. This mode of star formation is not a simple scaling of what happens in typical molecular clouds, but represents a much more efficient manner of converting gas into stars likely through the formation of massive clusters. The resulting feedback in the form of galaxy-scale outflows is, together with AGN, thought to be one of the main forms of regulation of galaxy growth. I will show the analysis of recent, high resolution observations of three of the nearest starbursts: NGC253, NGC4945, and M82. I will first discuss the properties of their galactic molecular outflows, including our best constraints on the mass and outflow rate, and the properties of the molecular gas. Then I will focus on the results from high-resolution observations which reveal a dozen compact structures with properties corresponding to massive young star clusters and super star clusters (SSCs), most of which are so embedded that are invisible in optical and NIR observations. Finally, I will present the analysis of 0.5-pc resolution observations of NGC253 which reveal feedback and disruption on the scales of these clusters, I will discuss the properties of these "cluster-scale" outflows, and I will compare them to theoretical expectations.

Date:   Wednesday 15-Mar-2023
Speaker:   Dr. Carl Fields (Los Alamos National Lab)
Title:  The Next Generation of Stellar Astrophysics

Stars play a critical role throughout our Universe via galactic chemical evolution, compact object formation, and stellar feedback. Computational models of stars have progressed over the decades in concert with astrophysical observations to advance our understanding of stellar evolution and transient phenomena. These models have benefitted from new observational campaigns, nuclear physics experiments, and computational and technological advancements. However, despite these advancements, there are long-standing challenges among stellar models that require novel approaches. I will discuss my work leveraging one-dimensional (1 D) stellar models, 3D stellar convection simulations, and models of stellar transients to move us towards the next generation of stellar astrophysics. I will highlight my approach to connecting 1D stellar models to astrophysical observations and in leveraging constraints rom experimental nuclear physics data. Following this, I will discuss my novel approach to modeling late-time stellar convection and the implications for nucleosynthetic observables, mixing and transport in stellar interiors, and the properties of compact objects.Lastly, I highlight the need for novel approaches to modeling stellar transients to bring simulation results in agreement with observation. In particular, I will show that realistic progenitor models can alleviate long-standing challenges in the field and have an impact of the predicted multi- messenger signals relevant to current and next-generation neutrino and gravitational wave detectors.

Date:   Wednesday 22-Mar-2023
Speaker:   NO COLLOQUIUM
Title:  SPRING BREAK

Date:   Wednesday 29-Mar-2023
Speaker:   Dr. Moses Milazzo (Otherorb)
Title:  Leveraging Political Capital in Pursuit of More Inclusive Teams

As a mid-career planetary scientist, I have many options of how I spend my time and focus my energy. Some of that time is spent in pursuit of my passion for planetary remote sensing science. I have also found that I have a passion for helping improve access to science. I have found a rewarding career doing both direct science and spending more time building supportive programs so others can do science too. In particular, I focus on leveraging my privilege and political capital to help remove unnecessary barriers to entry and similarly unnecessary barriers to continuing in the field once entry has been gained. I will present some of my work, including challenges as well as successes, and finally some potential future work, including ways in which those of us with access can help open more doors.

Date:   Wednesday 05-Apr-2023
Speaker:   Dr. Chris Reynolds (Cambridge/University of Maryland)
Title:  The Science and Technology of the Advanced X-ray Imaging Satellite

The Advanced X-ray Imaging Satellite (AXIS) is a University of Maryland led response to NASA's call for Astrophysics Probe-class Explorer missions. Operating in the 0.3-12keV bandpass, AXIS will provide high-spatial resolution imaging (~1 arcsec) across a wide-field of view (24 arcmin diameter) with an order of magnitude more collecting area and sensitivity than our current capabilities (exemplified by the Chandra X-ray Observatory), while providing rapid response capabilities for transients sources. In this talk, I shall give an overview of the science of AXIS and the technology that makes it possible. AXIS will open new windows on the hot and dynamic Universe revealing the seeding mechanisms and early growth of supermassive black holes, the physics of feedback in galaxies, and the drivers behind explosive transients in the Universe. Launching in 2032, AXIS benefits from natural synergies with the Roman Space Telescope, the Rubin Observatory, ELTs, SKA, ALMA, ATHENA, and CTA. AXIS utilizes breakthroughs in the construction of lightweight X-ray optics from mono-crystalline silicon blocks, and developments in the fabrication of large format, low noise, high readout rate detectors allowing a robust and cost-effective design.

Date:   Wednesday 12-Apr-2023
Speaker:   Dr. Lily Zhao (Flatiron Institute)
Title:  Advancing Radial Velocity Precision Using Data Driven Approaches

Extreme precision radial velocity (EPRV) measurements will reveal low-mass planet compositions, more complete system architectures, better inform planet formation scenarios, and allow for interpretable atmospheric spectroscopy. Achieving this level of precision requires innovation at all levels, from the hardware through to the extracted pectra and the final derived RV measurements. I will give an overview f recent advances in the field that make use of the data itself to reveal ariations and construct data-appropriate models for correcting them. I will conclude by showing examples of the types of work these advancements have made possible.

Date:   Wednesday 19-Apr-2023
Speaker:   Prof. Vikram Ravi (Caltech)
Title:  The Deep Synoptic Array: fast radio burst probes of the unseen Universe

The origins of fast radio bursts (FRBs) at extragalactic distances remain shrouded in mystery. FRBs nonetheless form exquisite tracers of the contents and physical conditions of baryons along their sightlines. For example, FRBs are dispersed in intervening plasma columns, and these columns are typically dominated by gas around and in between galaxies. Much of the cosmic baryon content is locked in this hot (>10^6 K) and diffuse (<10^-3 cm^-3) phase, making it difficult to observe the processes whereby galaxies grow out of and impact their baryonic environments. he Deep Synoptic Array (DSA-110) radio telescope, nearing the end of construction at Caltech's Owens Valley Radio Observatory, is pinpointing FRBs to host galaxies at a world-leading rate. I will present the first results from a DSA-110 FRB sample. These results shed new light on the origins of FRBs, highlighting the roles of multiple progenitor channels. Certain DSA-110 discoveries also enable tantalizing measurements of the content of the Milky Way CGM, and the ICM of nearby massive galaxy clusters. I will conclude by introducing the upcoming DSA-2000 radio camera, which will transform our access to the radio sky. With unmatched survey speed for continuum, spectral-line and short-timescale emission in the 0.7-2GHz band, the DSA-2000 will address frontier questions on our cosmic history, and in multi-messenger and time-domain astrophysics.

Date:   Wednesday 26-Apr-2023
Speaker:   Dr. Richard Mushotzky (UMD)
Title:  A Journey of 50 years and a Few Gigaparsecs-How Recent X-ray Results Have Changed Our Understanding of AGN and a Peek at the Future

Since the dawn of x-ray astronomy 60 years ago, finding and studying active galaxies (accreting supermassive black holes) has been a prime area of study. I will very briefly summarize the events of the last 5 decades concentrating on my own research. Over the last decade a major change in our understanding of these objects have been enabled y the first sensitive hard (E> 10 keV) all sky x-ray surveys, followed up by detailed observations across the entire electromagnetic spectrum. I will briefly summarize some of a major changes in our understanding of the nature of the host galaxies, the relationship to star formation, black hole mass, AGN fueling, and the implications for the theoretically predicted effect of feedback at low redshifts. I will examine the next steps in our understanding, stressing the soon to be launched XRISM x-ray spectroscopy mission and discuss the more distant future, focusing on the AXIS x-ray probe concept.

Date:   Wednesday 03-May-2023
Speaker:   Dr. Chris White (Flatiron Institute)
Title:  Frontiers in Black Hole Accretion

Black holes, together with the matter falling into them, are important and fascinating objects whose study lies at the intersection of a number of subfields of astrophysics. With observational data continually increasing in quantity and quality, our theories are forced to tackle the more nuanced complexities of these systems. I will discuss how computational modeling has improved, and continues to improve, for example by considering misaligned angular momentum, statistical variability properties, and the effects of strong radiation fields.

Date:   Wednesday 10-May-2023
Speaker:   Dr. Belinda Wilkes (CFA)
Title:  X-ray Astronomy Comes of Age: the breadth and depth of Chandra and XMM-Newton Science

NASA’s Chandra and ESA’s XMM-Newton were both launched in 1999 and celebrated their 20 th anniversary in 2019. The (still continuing) longevity and unparalleled success of these complementary and collaborative free-flying satellites is a major success story for NASA and ESA, and for the astronomical community and our science. Multiple activities and publications celebrated these key milestones along with their ground-breaking contributions to so many diverse areas of our science. I will briefly describe their capabilities, the ways in which the missions collaborate and complement one another, and present highlights of some of the most important discoveries with emphasis on the second decade of operations.

This page was automatically generated on: 15-Aug-2023.