Wine and Cheese Fall 2023

This page records the schedule, titles and abstracts of the JHU/STScI CAS Astrophysics Wine & Cheese Series in Fall 2023.

Wine and Cheese sessions with one speaker will have a 50 minute talk with 10 minutes for questions. Sessions with two speakers will have two 25 minute talks, each with 5 minutes for questions. Sessions in the Graduate Student Series will have three 15 minute talks, each with 5 minutes for questions.

11 September

Ferah Munshi (George Mason)

Understanding Galaxy Evolution at the Lowest Masses
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. I 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). I will present results and predictions constraining star formation, feedback and dark matter physics soon testable by telescopes like JWST, Rubin's LSST and the Roman Space Telescope. Finally, I will present results about 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. I will discuss the role of environment in addition to satellite quenching times and their mechanisms with an eye toward comparing with observations.

18 September

William Coulton (Flatiron Institute)

New Views of Galaxy Groups and Clusters with Precision CMB Secondary Measurements
High resolution cosmic microwave background (CMB) experiments provide a view of the Universe both at redshift ~1100, when the primary CMB was produced, and an integrated view of the Universe between then and now, through CMB secondary anisotropies. The CMB secondary anisotropies provide direct access to the integrated mass, electron density, electron pressure and electron temperature. In this talk, I will first present recent maps of CMB secondaries from the Atacama Cosmology Telescope collaboration. I will then show how upcoming experiments will be able to measure new observable signatures of galaxy groups, and how these can be used to inform our understanding of the thermodynamics of these objects.

25 September

Haowen Zhang (Arizona)

TRINITY: the Dark Matter Halo—Galaxy—Supermassive Black Hole (SMBH) Connection from z=0-10
Supermassive black holes (SMBHs) exist in many galaxies. Their growth is accompanied by strong energy output, which is capable of regulating host galaxy evolution. Understanding SMBH growth is thus critical for studying galaxy formation and evolution. However, it has been difficult to quantify SMBH growth in different galaxies and cosmic epochs. In this talk, I will present TRINITY, a new empirical technique to determine the typical SMBH mass and growth rate in different galaxies and dark matter halos from z=0-10. I will discuss how the galaxy—SMBH connection from TRINITY will help theoretical astronomers to create better simulations of galaxy evolution. In addition, I will show that the latest JWST-detected SMBHs match TRINITY’s predictions, in terms of their SMBH masses and growth rates.

Tony Chen (JHU)

The observed structure of the universe suggests that galaxy mergers and the co-evolution of their central supermassive black holes (SMBHs) are common throughout the cosmos. While the formation of binary SMBHs seems inevitable, direct observational evidence has been elusive. Active SMBHs, known as quasars, provide an excellent way to find and study distant dual SMBHs in electromagnetic waves. At kilo-parsec scales, large systematic searches of dual quasars at cosmic noon (z~2) are limited by the stringent angular resolution requirement in ground-based optical telescopes. I will introduce our recent efforts to find small-scale dual quasars. I will present a novel astrometric technique called Varstrometry, which enables the identification of unresolved dual quasars using all-sky surveys like Gaia. Using Varstrometry and observations from the Hubble Space Telescope, dozens of kpc dual quasar candidates were discovered. These kpc dual quasars are excellent samples to yield constraints on cosmological simulations and study the triggering of quasar activity due to galaxy mergers. In the end, I will summarize the talk with new exciting results and upcoming programs.

09 October

Alex Dittman (UMCP)

The Final Stages of Supermassive Black Hole Binary Mergers and their Multi-Messenger Signatures
Supermassive black hole binaries form in the aftermath of galaxy mergers, and the gas expected to abound in the centers of post-merger galaxies may both expedite the coalescence of these binaries and facilitate electromagnetic observations of these systems. I will illustrate how these systems evolve as gravitational waves begin to dominate their evolution, following their inspirals from hundreds of gravitational radii until merger. We find that binaries are likely to accrete throughout their time in the LISA band, but with unique signatures that may help localize these events, facilitating measurements of cosmological parameters and more precise constraints on binary constituent properties.

Jesse Bluem (GSFC)

Widespread Detection of Two Components in the Hot Circumgalactic Medium of the Milky Way
The Milky Way is surrounded by the circumgalactic medium (CGM), an extended reservoir of hot gas that has significant implications for the evolution of our Galaxy. The HaloSat all-sky survey was used to study the CGM's soft X-ray emission, finding evidence that at least two hot gas model components are required to produce the observed emission. The cooler component has a typical temperature of kT ~0.18 keV, while the hotter component has a typical temperature of kT ~0.7 keV. The emission measure in both components indicates that the CGM is clumpy.

16 October

Lauren Weiss (Notre Dame)

Planets, Patterns, and the Origin of Life
Exoplanet science is an explosive new field catalyzed by the discovery of over 5000 extrasolar planets via the NASA Kepler and TESS missions. With precise transit photometry and high resolution spectroscopy (including radial velocities), we are learning about diverse types of planets, their interior and atmospheric compositions, their orbital properties, the systems in which they reside, and how the planets form and change over time. In this talk, I will discuss unanticipated patterns that emerge nearly ubiquitously in hundreds of exoplanet systems. These patterns have reshaped our understanding of planet formation, with implications for the origins of Earth-like planets and life. Continued characterization of these patterns with ground and space-based telescopes will reveal what kinds of planetary systems are common, perhaps at last establishing whether the solar system itself is common or rare.

23 October

Ruchi Pandey (Astronomy & Astrophysics Division, Physical Research Laboratory, Ahmedabad, India)

Shock-Induced Dust Formation in Novae: A Phenomenological Study
Novae are fascinating objects which have enabled the direct observation of the various aspects of circumstellar dust formation on a frequent basis. Since the timescale of dust formation in novae typically ranges from 30 to 100 days following an outburst, these environments can serve as test beds for studying the formation and evolution of astrophysical dust. However, dust formation in the hostile environment of novae ejecta has been an open question for many decades. Several attempts have been made to understand the physical and chemical conditions required for this phenomenon and its relationship with the observable parameters. Numerous hypotheses have been developed in order to explain the mechanisms that underlie the process of dust formation. An intriguing proposition is put forth, suggesting the possibility of shock-induced dust formation in novae. A recent study of Nova V2891 Cyg by a team of astronomers at Physical Research Laboratory, India has provided, most likely, the first observational evidence of such a method of dust formation in novae ejecta. In this seminar, I will commence with a concise introduction to the phenomenon of dust formation in novae, highlighting its significance and the current gaps in understanding the same. Subsequently, I will shed insights into the phenomenological modelling of Nova V2891 Cyg and bring out its relevance in illustrating the origin of some observational signatures of shock-induced dust formation.

30 October

Yunyang Li (JHU)

Cosmology Large Angular Scale Surveyor (CLASS): Recent Progress and the 40 GHz Results
I will discuss the development and recent progress of the CLASS telescope (Cosmology Large Angular Scale Surveyor) with a highlight on its 40 GHz survey. CLASS is a four-frequency telescope array in the Atacama desert in northern Chile, observing the cosmic microwave background (CMB) polarization at 40, 90, and 150/220 GHz. By measuring the CMB E mode polarization on large angular scales (ell<30), CLASS will be able to constrain the optical depth toward the last scattering surface and improve upon the sum of the neutrino mass measurement. In this talk, I will focus on the data reduction pipeline development and the results from the 40 GHz maps. We present the 40 GHz polarization maps that cover 75\% of the sky from the ground, with signal recovery 75\% (45\%) at angular scales ell=20 (10). These maps show synchrotron power spectrum and frequency dependency consistent with the satellite measurements and with superior sensitivity in the range 10<ell<100. CLASS also places the tightest constraints on the astrophysical circular polarization background. This talk will conclude with an outlook on the future development of the CLASS experiment.

Suchetha Cooray (NAOJ)

A Comprehensive Understanding of the Light from Galaxies
I am developing an empirical galaxy formation model that self-consistently models the galaxy growth histories within the context of cosmological structure formation. Currently, these models requires calibrating on observationally inferred galaxy physical properties. However, the limited information in a single observed galaxy spectral energy distribution (SED) and therefore the inherent uncertainties in modeling mean that we at least have a ~0.35 dex uncertainty on those physical properties. The next-generation empirical galaxy formation model will forward model and directly match all the observed SEDs across cosmic time. The self-consistent evolution of the galaxy properties should reduce the uncertainty on galaxy properties down to ~0.15 dex level. I will discuss recent progress and some scientific questions we can start to answer with this approach. I will also discuss how generative models could be used to make inferences at the pixel level (field-level inference) for galaxies possible. Key outcomes include a fully physical, self-consistent picture of galaxy stellar masses, star formation histories, dust, and metallicity from z = 0 to 15; significantly reduced uncertainties on the galaxy-halos connection; and highly realistic mock catalogs and images for arbitrary current and future surveys that self-consistently match the latest observations.

06 November

Subo Dong (IAS)

Probing the Other Dark Universe with Microlensing
Gravitational microlensing is the only known method to discover dark objects ranging from isolated stellar-mass black holes (BHs) down to Earth-mass free-floating planets (FFPs). The recent success of interferometric resolution of microlensed images with VLTI opens up a new venue for discovering isolated stellar remnants. I discuss how the VLTI-GRAVITY(+) instrument can significantly advance such discoveries, potentially leading to measuring the mass function of isolated stellar-mass BHs. Ground-based surveys have found more than a dozen ultra-short microlensing events, with the intriguing implication that FFPs are a few times more common than planets bound to stars. I will discuss the prospect of future space-based microlensing surveys to discover and characterize a large sample of low-mass FFPs.

10 November

Tsvi Piran (HU)

Radio emission, Relativistic Jets and Ultra High Energy Cosmic Rays from Tidal Disruption Events
Sw 1644 was one of the most surprising tidal disruption events (TDEs). Its prompt emission in soft gamma-rays triggered Swift. Later on, this was followed by X-ray and Radio afterglows. The energy implied by the radio afterglow increased by a factor of 10 over a period of a few hundred days, ultimately reaching a few times 1052 erg. This is much higher than what was observed in other TDEs. The combination of initial gamma-rays and strong afterglow makes Sw 1644 the prototype of “jetted” TDEs. Other TDEs have shown radio emission that was much weaker and very different. Those are naturally explained as arising from the interaction of the unbound debris with the surrounding matter. Recently, several TDEs have shown a delayed radio emission that began a few years after the event. These led us to reconsider Sw 1644 and suggest that both Sw 1644 and the delayed emission events are relativistic jets viewed off-axis. This requires an initially relativistic jet with 1053 erg, making these events among the most energetic transient events. I will speculate on the origin of these events, as compared with regular TDEs that are significantly weaker, and on implications for other phenomena and in particular, to the origin of Ultra High Energy Cosmic Rays.

27 November

Anthony Remijan (NRAO)

A Brief History of Astrochemistry – Hunting for New Molecules in Space
For many, it was hard to comprehend that the search for the first molecules in space at radio frequencies in the late 1960's would lead to the wealth of interstellar molecules that we see today - a total that is well over 270 individually detected species and several factors more if all isotopologues and higher vibrational states are included. The prevailing attitude at the time was that the physical conditions in astronomical environments were too harsh to drive the formation of any molecules, let alone molecules more complex than simple diatomic hydrides. Yet, against all odds, the science of radio astrochemistry accelerated, especially after the early detections of water (H2O), ammonia (NH3) and formaldehyde (H2CO) between 1968 and 1969. This presentation will cover these first early detections with single dish telescopes, through the search, detection and subsequent non-detection of several molecules that are considered significantly biologically interesting and the concluding with future prospects of new molecule searches with new facilities (e.g. SKA and ngVLA) and new analysis techniques (e.g. machine learning, MCMC and matched filters). And finally, and if there is time, we will discuss the recent controversial detections (one in the radio and another in the IR) that have sparked discussions of their biological importance in space!

4 December

Manoj Puravankara (TIFR)

Investigating Protostellar Accretion and Outflow across the mass spectrum: First results the from the JWST Cycle 1 program
Protostars, although short-lived (< 0.5 Myr), play an important role in cosmic evolution. Within the dusty envelopes that shroud them, the complex, highly time dependent processes of infall, accretion and outflow shape the IMF, set the chemical initial conditions for planet formation, and may regulate star formation on cloud scales. The Investigating Protostellar Accretion (IPA) across the mass spectrum is a medium-sized cycle 1 GO program with the JWST that has obtained NIRSpec IFU and MIRI MRS observations of five deeply embedded protostars with luminosities ranging from 0.2 to 10000 L_sun and masses of 0.12 to 10 M_sun. From these observations, IPA has produced spectral images in the 2.9-28 micron range and a spatial resolution down to scales as small as 30 au. Our infrared spectral maps reveal previously unseen details of the interaction between accretion-driven jets and outflows and the innermost envelope of the protostars. Highly collimated jets that appear in ionic lines with velocities ~100 km/s are detected in all sources. Of particular interest is the discovery of a collimated jet in the lowest mass and luminosity source with a mass loss rate of ~10^-10 solar mass/year, indicating that it is in quiescent phase. Bright gas phase CO vibrational emission appear to arise from shocks in jets/winds and the innermost parts of the protostellar disks. The walls of cavities carved by the jets and (probably) winds are delineated in scattered light; interestingly, wide-angled outflows traced by molecular hydrogen show opening angles much smaller than that of the cavity walls, suggesting they are well inside the cavity. The composition and the spatial distribution of various ice species in the higher luminosity sources show evidence for thermal processing. I will present the first results from the IPA program and discuss their implications for our understanding of the formation and evolution of stars and planetary systems.