Event Type: Astrophysics Colloquium

Description coming soon.

Description coming soon.

Description coming soon.

A new view of the red and distant Universe from JWST/NIRSpec Abstract: In its three years of science operations, JWST has revolutionized our understanding of the early Universe. Arguably the most impressive leap forward has come from the NIRSpec instrument, providing a detailed view of the physical processes – star formation, feedback, and the growth

Pioneering Emission Mapping of the Circumgalactic Medium with Aspera: Mission Progress and Lessons Learned. For over half a century, observational astrophysics has sought to detect and map warm-hot phase ‘coronal’ gas in the circumgalactic medium (CGM), one of the most massive baryonic components of galaxies. Despite its importance to galaxy evolution, this gas phase remains

Thermonuclear X-ray Bursts: Probing Neutron Stars and a Double-Photospheric-Radius-Expansion Thermonuclear X-ray bursts observed from neutron stars originate from intermittent unstable nuclear burning of accreted matter on these stars. Such bursts, which significantly outshine the accretion-powered emission, are an excellent tool for probing the strong gravity and superdense matter, as well as for studying nuclear fusion,

History of the Intergalactic Medium Thermal History The thermal history of the intergalactic medium (IGM) is governed by the relatively simple physics of photoheating and cooling, and can be constrained using measurements from the Lyman-alpha forest. Over the past decade, these measurements have become much more precise. Unexpectedly, important theoretical advances have also emerged —

Title: Ergomagnetospheres, Ejection Disks and Wave Optics in M87 and SS433

Cosmic heavyweights: masses, host galaxies, and an origin story Abstract: Supermassive black holes (SMBHs) are ubiquitously found at the centers of massive galaxies near and far, and they likely played pivotal roles in shaping the co-evolution of galaxies and their central engines. Yet, the origins of SMBHs remain a mystery. Recent observational advancements have made significant

It Takes Two to Tango: Modeling Binary Stellar Populations in the Gravitational Wave Era Abstract: The field of astrophysics is in the midst of a golden age. Between the detection of gravitational waves from over a hundred merging compact objects, the commissioning of the James Webb Space Telescope which can see galaxies farther away and further

Using Tidal Disruption Events as Probes of Massive Black Hole Formation and Growth Over Cosmic Time The tidal disruption of a star that wanders too close to a central black hole is a unique probe of quiescent supermassive black holes lurking in the nuclei of galaxies. We have demonstrated the ability to discover and spectroscopically

What is JWST teaching us about the early Universe? The James Webb Space Telescope (JWST) is revolutionizing our understanding of the early universe, and in this talk I will explore how its observations fit — or don’t — within our cosmological and galaxy-formation models. First, I will discuss the unexpectedly high abundance of galaxies in

The Dynamical Evolution of Exoplanet Systems Over Billions of Years Exoplanet systems are expected to evolve with time as they age. In most cases though, the dynamical evolution of exoplanet systems over billion-year timescales are hard to directly observe. I’ll first describe the variety of ways that data from Gaia and/or the James Webb Space

Like most galaxies, the Milky Way harbors a supermassive black hole (SMBH) at its center, surrounded by a stellar cluster. In this densely populated environment, stars frequently collide and interact with one another. I will discuss the implications of these collisions and connect them to astrophysical puzzles observed at the very heart of our galaxy. Close

The x-ray sky in high definition: 25 years of astrophysics with the Chandra X-ray Observatory X-ray astronomy is a product of the space age. Possible only from viewing platforms above the atmosphere, the first celestial x-ray source other than the Sun was discovered just over sixty years ago. Following fresh on the heels of this

Probing the beginning of the universe with precision microwave polarimetry observations We are in an exhilarating era in which cosmological models are being tested by cutting-edge instruments that push the boundaries of theoretical predictions and technological innovation. Observations of polarized light from the cosmic microwave background (CMB) will enable us to detect, or constrain, the

JWST views of quasars and little red dots at cosmic dawn Quasars at cosmic dawn are powerful probes to the formation and growth of early supermassive black holes in the universe, their connections to high-redshift galaxy and structure formation, and the evolution of the intergalactic medium at the epoch of reionization. I will first review

Astronomy re-envisioned: investigating the physics of galaxy evolution with Machine Learning Interpretable machine learning (ML) techniques and artificial intelligence (AI) are revolutionizing our ability to study galaxy evolution and large-scale structure. Convolutional neural networks (CNNs) can now reliably predict galaxies’ physical properties, including cold gas content and metallicity, directly from three-color optical images. These models

Dynamics and energetic transients in galactic nuclei Centers of galaxies host a variety of dynamical processes, owing to the high density of stars and the presence of a central Supermassive Black Hole (SMBH). Orbital relaxation brings stellar objects into close encounters with the SMBH, driving a plethora of energetic phenomena. These include tidal disruption events,

Trustworthy Machine Learning for data-driven discovery Modern machine learning techniques have ushered in an era of data-driven astronomy.  Flexible new ML tools enable powerful data analysis strategies that were not feasible even a few years ago. This shift in our scientific approach requires us to ask an important question:  Can we trust the black box? 

Observing atmospheric evolution in extrasolar planets Atmospheric escape has driven the long-term evolution of most known planetary atmospheres, including terrestrial planet atmospheres in our Solar System. In this talk, I will discuss the wealth of information we can learn from studying atmospheric escape in extrasolar planets, focusing on three main observational efforts. I will first

Mapping out the colliding dark matter haloes of the Milky Way and LMC with stellar streams Stellar streams form as dwarf galaxies and globular clusters tidally disrupt around their host galaxy. To date, more than 100 streams have been detected around our Galaxy. In this talk, I will begin with an overview of how streams

“Two-Eyed Seeing”: uniting perspectives to drive innovation in galactic dynamics & major observatory design “Two-eyed seeing” was coined by Albert Marshall, a Mi’kmaq elder, to describe the depth of perspective gained when perceiving the world through both an Indigenous and western lens.  This talk describes a two-eyed seeing framework for both an approach to galactic

The Zwicky Transient Facility: concept to results The Zwicky Transient Facility (ZTF) is at present undertaking an ambitious survey of the dynamic optical night sky. It searches systematically for exploding stars, burping quasars, variable stars and moving objects.  ZTF is considered the pre-cursor of the Rubin Observatory’s Legacy Survey of Space & Time (LSST), the

Microlensing is uniquely capable of studying planets across a wide range of masses at a few AU from their host stars, At the lower masses, these planets are difficult to impossible to find with other techniques. I will discuss recent results in microlensing suggesting a turnover in the planet mass ratio function around 10^-4, i.e.

space, permanently transforming the Universe. Determining exactly when and how reionization occurred is therefore central to our efforts to understand these early sources, as well as the physics that governs the interaction between galaxies and their environments. I will describe what we know about reionization from the study of quasar absorption lines and other probes

The solar cycle causes the Sun to change on timescales that can affect life. The maxima of cycles are marked by an increased occurrence of sunspots that cause solar flares and coronal mass ejections that can cause potentially harmful geomagnetic storms. Despite the fact that the existence of the solar cycle has been known for

The CMB presents a unique probe of dark matter physics. Ultra-light axions of mass around 1e-22 eV are a promising dark matter candidate well motivated by high energy physics. The Simons Observatory (SO) is a new cosmic microwave background (CMB) experiment being built on Cerro Toco in Chile, due to begin observations in the early

Although thermonuclear (Type Ia) supernovae and neutron star mergers are some of the most important astrophysical events, our understanding of these explosions is vague.  I will present abundance measurements of elements across the periodic table (Mg, Fe, Ni, Ba, and others) that address the nature of both types of explosions.  The measurements are based on

Women and people of color are severely underrepresented in many STEM departments, especially in physical sciences and engineering. Professional societies and universities have issued reports full of recommendations. Which ones have worked? This talk will identify departments that are most successful in diversifying bachelor’s and doctoral degrees in STEM. Using data on student and faculty

With increasing cadence and areal coverage, optical transient surveys can probe fast and rare regions of transient parameter space. In particular, ~100 transients have been discovered whose properties (a fast rise to peak, and high peak luminosity) challenge our understanding of how energy is deposited and transported in stellar explosions. Here we present ZTF18abukavn (SN2018gep),

The Event Horizon Telescope recently revealed the first picture of the black-hole shadow in the center of the M87 galaxy. I will discuss the technological and theoretical advances during the last decade that led to this result. I will then focus on how this picture allows us to accurately measure the mass of the black

In the upcoming era of JWST and 30-meter class ground-based telescopes we will be forced to reckon with the full 3-D nature of extrasolar planets. Today, many current models treat exoplanet atmospheres in one dimension, as a vertically stratified global average — similar to 1-D models of stars and many solar system planets. Yet we

Our understanding of the dynamics of our Local Group of galaxies has changed dramatically over the past few years owing to significant advancements in astrometry and our theoretical understanding of galaxy structure. New surveys now enable us to map the 3D structure of our Milky Way and the dynamics of tracers of its dark matter

Exoplanet collection identified in the last 25 years ranges from massive and big planets like Jupiter to smaller denser and more compact objects similarly to Earth. Most of these planets are assembled in system orbiting close to their star. In that rich and stimulating landscape, this talk will describe two specific programs aiming to fill-in

Are we drowning in exoplanets, or have we barely begun to discover them?  What do we currently understand about the broad exoplanet population? With hundreds to thousands of new transit candidates coming from the TESS and Gaia missions, and major new populations to be discovered by WFIRST and direct imaging surveys, things are starting to

Nearly all galaxies appear to harbor a supermassive black hole. The origin and properties of initial black hole seeds that grow to produce the detected supermassive black hole population are unconstrained at present, as actively growing seeds are not directly observable near their birth epochs. Nevertheless, some unique signatures of seeding do survive and still

Testing the predictions of general relativity in the dynamical strong-field regime, in particular black holes and their dynamics, has only recently become possible with LIGO/Virgo observations of black hole mergers. I will review some of the tests that have been performed to date. However, one obstacle to extracting the most stringent constraints possible is the

Quadruply lensed quasars (“quads”) are used to study several important astronomical problems, one of which, the abundance of LIGO-mass primordial black holes, we discuss at some length. But quads are rare, with only one out of every 3000 quasars lensed into a quad. The alternative schemes used to identify them all have serious shortcomings of

Blueshifted ionized absorption features at near-relativistic velocities (v~0.1c or higher). known as ultra-fast outflows (UFOs), seem to be ubiquitously present in x-ray spectra of many AGN populations of different luminosity. Canonical AGN UFOs, typically detected in Fe K band, exhibit massive column (NH > 1e23 cm^-2), highly ionized ions (log \xi ~ 4 – 6)

The ever-increasing need for accurate prediction for complex non-linear processes leads to large scale dynamical systems whose simulations and analysis make overwhelming and unmanageable demands on computational resources. The evolution of the Universe is one of these complex processes that the computational cost of the traditional full-order numerical simulations is extremely prohibitive. In this talk, we