ASD Colloquium Series - Spring 2023
ASD Colloquium Series - Spring 2023
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.
Below is the list of scheduled talks for this period. Confirmed speakers are shown in bold face, while tentatively scheduled speakers are listed in normal face.
Schedules from past colloquium seasons are available.
Contact: Scott C. Noble
| January | |
|---|---|
| Jan 3 | No Colloquium - New Year's Week |
| Jan 10 | No Colloquium - Winter AAS Meeting |
| Jan 17 | No Colloquium - Martin Luther King Jr. Day Weekend |
| Jan 24 | Quantum Matter and Clock: From Emergent Phenomena to Fundamental Physics Jun Ye (JILA, National Institute of Standards and Technology and University of Colorado) |
| Jan 31 | Transforming a "Static" View of Galaxy Clusters into a Full Dynamic Picture Irina Zhuravleva (Department of Astronomy and Astrophysics, the University of Chicago) |
| February | |
| Feb 7 | Reconstructing Planet Formation Using Dynamical and Chemical Fossils Daniella C Bardalez Gagliuffi (Department of Physics & Astronomy, Amherst College) |
| Feb 14 | New Mission Concept: Compton Telescope with Coded Aperture Mask, and its Science Perspectives Alexander Moiseev (GECCO Collaboration, Astroparticle Physics Lab (661), NASA GSFC) |
| Feb 21 | No Colloquium - President's Day Weekend |
| Feb 28 | Open source software for probabilistic data analysis in astrophysics Dan Foreman-Mackey (Center for Computational Astrophysics, Flatiron Institute) |
| March | |
| Mar 7 | New Avenues for Multi-Messenger Discoveries in High Energy Astrophysics Rafael Martinez-Galarza (CfA, Harvard) |
| Mar 14 | Presence and Power of Active Galactic Nuclei in Post-Starburst Galaxies Lauranne Lanz (Department of Physics, The College of New Jersey) |
| Mar 21 | Special Location: B34, W305 Graceful Technical Writing Scott Thomas (Cambridge University Press & Assessment) |
| Mar 28 | Things in AGN Disks: Multimessenger Approaches to Understanding AGN Saavik Ford (American Museum of Natural History, CUNY Borough of Manhattan Community College) |
| April | |
| Apr 4 | Cosmology Bingo: CHIME results, Dark Energy, and Drones Laura Newburgh (Department of Physics, Yale University) |
| Apr 11 | Special Location: B34, W305 Observational Evidence for the Origin of High-energy Neutrinos in Parsec-scale Nuclei of Radio-bright Blazars Yuri Kovalev (MPIfR, Bonn) |
| Apr 18 | Neutrino Astronomy: From Dream to Reality Naoko Kurahashi Neilson (Department of Physics, Drexel University) |
| Apr 25 | Simulating galaxy formation across vast reaches of space and time: towards a new paradigm Rachel Somerville (Center for Computational Astrophysics, Flatiron Institute) |
| May | |
| May 2 | Black holes and revelations: unseen companions in stellar binaries Kareem El-Badry (Harvard-Smithsonian Center for Astrophysics) |
| May 9 | Special Location: B34, W305 Tracking the Merger History and Growth of Supermassive Black Holes Adi Foord (KIPAC, Stanford University) |
| May 16 | No Colloquium |
| May 23 | Special Location: B34, W305 Feedback in General, NGC 5195 in Particular Eric Schlegel (Univeristy of Texas, San Antonio) |
| May 30 | No Colloquium - Memorial Day Weekend |
| June | |
| June 06 | No Colloquium |
| June 16 | Special Day & Time: 3-4 PM GRBs and the ISM Andrew Blain (University of Leicester) |
| June 20 | The Gas Pixel Detectors onboard the Imaging X-Ray Polarimetry Explorer Luca Baldini (Istituto Nazionale di Fisica Nucleare - Sezione di Pisa) |
| June 27 | No Colloquium |
| July | |
| July 04 | No Colloquium - Fourth of July Weekend |
| July 11 | No Colloquium |
| July 17 | Special Day Artificial Intelligence and Machine Learning in Astronomy Ajit Kembhavi (Inter-University Centre for Astronomy and Astrophysics, Pune, India & Pune Knowledge Cluster) |
Abstract
Precise quantum state engineering, many-body physics, and innovative laser technology are revolutionizing the performance of atomic clocks and metrology, providing opportunities to explore emerging phenomena and probe fundamental physics. Recent advances include measurement of gravitation time dilation across a few hundred micrometers, and employment of quantum entanglement for clock comparison.
Abstract
By virtue of their large mass and deep gravitational potential well, galaxy clusters are filled with low-density but extremely hot weakly-magnetized plasma that emits X-rays. Many astrophysical processes, including feedback from supermassive black holes, mergers and large-scale structure evolution, are imprinted on this hot intracluster gas. Understanding these processes is crucial for, e.g., cosmological simulations that heavily depend on the assumptions built into their models, especially on small scales. The next fundamental frontier in the studies of galaxy clusters is measuring gas velocities and related microphysics. I will present some of our recent efforts toward understanding a full dynamic picture of the ICM, from cluster core regions to outskirts and from micro to macro scales. I will show observational constraints on transport properties of the ICM that are important for sustaining and dissipating gas motions, recent updates on feedback-driven gas motions, and high-resolution numerical studies of mergers-driven physics in cluster outskirts. I will finish my talk by reviewing near- (and more distant-) future X-ray missions and examples of the new science we will be able to explore.
Abstract
The dynamical and chemical signatures of a planetary system are independent fossil records of its past. Orbital parameters are vestiges of its formation and dynamical evolution, while chemical compositions of planets and hosts are fingerprints of the stellar nursery and the protoplanetary disk where they formed. In this talk, I will explain the cutting-edge techniques I am using to measure orbital parameters and compositions and how to leverage them to reconstruct the history of planetary systems at a population scale. Obtaining these measurements in a volume-limited sample will enable robust statistics to develop a probabilistic model of formation mechanisms, observationally constraining their transition from stellar binary to planetary formation for the first time. This analysis will lead to the identification of spectroscopic signatures of formation with next generation observatories as we take our first steps towards a comprehensive theory of star and planet formation to uncover our cosmic origins.
Abstract
The Galactic Explorer with a Coded Aperture Mask Compton Telescope (GECCO) is a novel Explorer-class concept for a next-generation telescope covering the poorly explored hard X-ray and soft gamma-ray energies. This concept builds upon the heritage of past and current missions, improving sensitivity and, very importantly, angular resolution. GECCO uses the combined Coded Aperture Mask and Compton telescope techniques to employ the benefits of both: superior angular resolution provided by the deployable Coded Aperture Mask, and good background rejection and wide field-of-view (FoV) provided by the Compton telescope. It is being developed at NASA/GSFC in collaboration with other US and foreign institutions. GECCO observations will extend arcminute angular resolution to high-energy images of the Galactic plane, combining the spectral capabilities of INTEGRAL/IBIS and the x-ray imaging of NuSTAR and eROSITA, and will make a bridge to the Fermi-LAT observations, enabling a broad potential for discoveries in the MeV γ-ray sky.
Abstract
Rigorous statistical methodology has been widely adopted across astrophysics, driven in large part by the availability of well-documented and user-friendly open source software. But, as datasets grow and research questions continue to get more ambitious, we need to continuously re-evaluate our tooling choices and learn from methodological developments across astrophysics and other disciplines. In this talk, I will give some examples of how and why open source tools developed for other purposes (like machine learning) can be used to accelerate and improve our data analysis workflows. I will, in particular, highlight some of my interdisciplinary work to develop computationally efficient and physically motivated methods for time domain astronomy, with specific applications to exoplanets and stellar variability, within modern high-performance model building frameworks. There are, however, some limitations to the broad application of these tools and ideas with astrophysics, so I will discuss some of the challenges and propose some possible approaches for tackling these issues.
Abstract
As high-energy datasets enter the era of big data, in particular in the context of multi-messenger astrophysics, we are starting a new chapter in observational X-ray astronomy: time-dependent flux variability of astronomical sources is revealing the nature of new, exotic types of event, such as pair-instability supernovae and neutron star mergers, lensing events, exotic planetary transits, as well as other, yet to be understood phenomena. These phenomena are typically observed over a broad range of wavelengths. Yet, while time-domain surveys at optical wavelengths have taken the lead to profit from vast observational programs (e.g. Vera Rubin), and from an even larger set of machine learning (ML) tools to pick up the exotic sources among millions of regular objects, the X-ray community is only now starting to delve into the synergies between data science and large data astronomical datasets for discovery. In this talk I will provide an overview of recent developments in data-driven, time-domain X-ray astronomy, and will attempt to provide an answer to the question “Which avenues of inquiry will be most ripe for discovery in the next few years?”. I will present a framework for the treatment of large X-ray datasets for the discovery of relevant transients, and present novel data representations for the event files that allow for their seamless discovery. I will show how these representations can be used in combination with ML architectures such as autoencoders, dimensionality reduction, and Graph Neural Networks to enable new science in the era of multi-messenger astrophysics. As a demonstration, I will share recent results on X-ray binary classification, and searches for fast X-ray transients in Chandra data.
Abstract
While active galactic nuclei (AGN) and their feedback are often invoked as a means by which galaxies can transition from actively star forming to quiescence, the importance of this activity and its frequency in driving the transition remains a major open question in galaxy evolution. Post-starburst galaxies, caught within a Gyr of star formation activity, provide an important laboratory for searching for signatures of AGN feedback. I will present our work using Chandra and XMM observations to constrain the frequency and luminosity of AGN in post-starburst galaxies. While a high fraction of our galaxy sample is detected at X-ray wavelengths, we typically have very few photons per source, with indications that the emission mechanism may vary from source to source. As such, we developed a forward-modeling methodology to constrain the properties of this emission even on the basis of only a handful of counts. I will discuss both the forward modeling methodology and the implication of the AGN luminosities on the role of AGN activity in post-starburst galaxies.
Abstract
As a scientist, communicating technical material is probably your greatest responsibility, but advice on how to write can be too prescriptive or too vague. "Avoid the passive voice." (Always?) "Don't end sentences with prepositions." (Why not?) I am an ex-astrophysicist who now works in English teaching and assessment. Using examples drawn from astronomy, I will show you how to identify common mistakes that make sentences and paragraphs difficult to understand, and share specific tips on how to convey your ideas cleanly. This talk is for everyone who writes or reads, especially if you've ever read a sentence and thought "That was confusing, but I can't say why."
Abstract
Active Galactic Nuclei (AGN) have been studied electromagnetically for decades, but many aspects of AGN remain uncertain to orders of magnitude, including their lifetimes, radial extent, and gas densities. Such uncertainties have important implications for many areas of astrophysics, including galactic evolution and LCDM models, due to the importance of AGN feedback in our models. However, LIGO-Virgo-KAGRA (LVK) have opened a new window in gravitational waves (GW), providing us a new probe of AGN disks—namely, stellar mass black holes that live at the midplane of AGN disks. I will discuss how we can use GW observations of merging binary black holes (BBH) from LVK to constrain parameters of AGN including their lifetimes. In addition, the recognition that there are 'things' in AGN disks opens up a wide range of new electromagnetic and possibly neutrino observing strategies. I will also look forward to the implications of these BBH mergers in AGN disks for both Rubin and the upcoming Laser Interferometric Space Array (LISA).
Abstract
Current cosmological measurements have left us with deep questions about our Universe: What caused the expansion of the Universe at the earliest times? How did structure form? What is Dark Energy and does it evolve with time? New experiments like CHIME are poised to address these questions through 3-dimensional maps of structure using the 21cm emission line from neutral hydrogen contained in abundance in galaxies. In this talk, I will describe recent results from the CHIME experiment that show a significant detection of neutral hydrogen in distant galaxies. I will discuss improvements we will need to make in future analyses, and how measurements of the instrument beams for telescopes using the 21cm emission of neutral hydrogen might be performed with drones.
Abstract
We present results from a joint analysis of VLBI and single-dish radio observations of a complete sample of active galactic nuclei and neutrino data from IceCube supplemented by ANTARES and Baikal-GVD. We report a 4sigma-significant observational evidence that high energy neutrinos are generated in radio-bright blazars and arrive preferentially during their flares. This means that AGN cores are capable of accelerating protons to relativistic energies. VLBI effectively selects active galaxies with jets whose electromagnetic and neutrino emission is strongly boosted towards an observer. We summarize new opportunities for multi-messenger studies to explore the nature of blazars as powerful proton accelerators for the current and planned facilities.
Abstract
The Universe has been studied using light since the dawn of astronomy, when starlight captured the human eye. The IceCube Neutrino Observatory, located at the geographic South Pole, observes the Universe in high-energy neutrinos. IceCube's discovery in 2013 of a diffuse celestial neutrino radiation started an era of neutrino astronomy. Since then, spectacular observations have been made identifying astronomical sources that emit such neutrinos. The state of neutrino astronomy and its place in multi-messenger astronomy will be reviewed.
Abstract
Upcoming experiments will map galaxies and gas across unprecedented volumes and probe further back into cosmic time than ever before, and have the potential to probe fundamental physics questions such as the nature of dark matter and dark energy, and the initial conditions of the Universe. But in order to extract the full scientific potential from these data, we need to understand how luminous tracers (stars and gas) are related to the underlying matter density field. Simulating galaxy formation from first principles is a huge computational challenge because of the vast range of scales and rich array of physics involved. All current large-volume simulations adopt ad-hoc phenomenological "sub-grid" recipes to treat critical physical processes such as star formation, stellar feedback, and black hole growth and feedback. I will review the current status of these simulations and highlight some of their successes, shortcomings, and challenges. I will then describe the philosophy and status of the SMAUG (Simulating Multiscale Astrophysics to Understand Galaxies) project, which aims to develop new, more physically grounded and predictive treatments of sub-grid processes in cosmological galaxy formation simulations, and present some of our recent results. I will highlight what we learn about galaxy formation and cosmology from the recent exciting detections of very early galaxies with JWST.
Abstract
The Milky Way contains of order 10^8 stellar-mass black holes (BHs). Yet, fewer than 100 BH candidates are known, and only about 20 are dynamically confirmed. Our view of the BH population has been shaped almost entirely by observations of X-ray binaries and gravitational wave sources, both of which represent an extremely rare outcome of binary evolution. I will discuss recent efforts to uncover the (potentially) much larger population of Galactic black holes in non-interacting binaries, focusing both on interpretation of genuine dormant BHs and on what can be learned about binary evolution from the menagerie of interacting binaries and stripped stars that have masqueraded as dormant BHs binaries.
Abstract
After decades of SMBH observations, the connection between AGN triggering and galaxy mergers remains incomplete, although AGN are likely key players in the evolution of massive galaxies. Theoretically, there are many reasons to expect a link between galaxy mergers and the accretion of material onto at least one of the central supermassive black holes. Yet, observationally, varied results have led to uncertainty in whether AGN triggering is dependent on environment. One of the best ways to analyze the possible ties between merger environments and SMBH activity is to study systems with unique observational flags of merger-driven SMBH growth -- or, systems of interacting AGN. I will present my work quantifying the dual AGN fraction at both high redshift, and as a function of redshift, via a large and uniform study of dual AGN in X-rays, up to z=3.5. By analyzing available data in wide and deep public Chandra surveys, the dual AGN fraction at both the high-redshift (2.5 < z < 3.5) and low-redshift (z < 0.03) regime can be better constrained. Pairing X-ray results with available multi-wavelength data (WISE, HST), we gain insight on how the X-ray activity of interacting AGN depends on their environments.
Abstract
Feedback is a general term to describe a process that is used to explain the relative lack of star formation in the nuclei of spiral galaxies as well as ellipticals among other effects. NGC 5195 in Messier 51 appears to be exhibiting behaviors that could be a different type of feedback, one more typically seen in supernova remnants. The presentation will attempt to lead the audience through both lines of thinking, presenting the data, and some challenges, along the way.
Abstract
The importance of the interstellar medium for controlling the processes of star-formation, AGN fueling and feedback is clear. However, even the best instruments struggle to resolve scales that match these processes even at moderate redshift. There are a variety of opportunities in looking at the interaction of intense GRB jets with the surrounding medium, and as data quality in both flux and timing improve, these effects might allow insight into the astrophysics of gas and dust on sub-pc scales.
Abstract
Successfully launched on December 9, 2021, the Imaging X-ray Polarimetry Explorer is a NASA small explorer mission developed in collaboration with the Italian Space Agency, and the first ever to provide space-resolved polarimetric capabilities in the 2-8 keV energy band. Now well into the second year of the mission, IXPE has detected non null linear polarization with high statistical significance for dozen of sources, both galactic and extra-galactic, across many different source classes. At the heart of the IXPE telescopes are three identical polarization-sensitive Gas Pixel Detectors (GPD). In this seminar we shall review the salient aspects of the IXPE GPD design and development, with emphasis on the technical challenges encountered during the ground tests and the lessons learned through the development of the mission.
Abstract
Machine Learning, Deep Learning and other Artificial Intelligence (AI) techniques have now become an integral part of development in every sphere of activity. The techniques are particularly important in astronomy, where powerful telescopes routinely generate vast quantities of data. In my talk I will describe some interesting applications of these a variety these techniques to various problems in astronomy including galaxy morphology, identification of very compact galaxies, determining the nature of the compact objects in Low-Mass X-ray Binaries etc. I will also mention some applications beyond astronomy.