Wine and Cheese Fall 2025

This page records the schedule, titles and abstracts of the JHU/STScI CAS Astrophysics Wine & Cheese Series in Fall 2025.

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 5ish minutes for questions.(Since when have you ever seen a question session cut short if everyone is interested?)

25 August

John Silverman (IPMU)

Evolution of Supermassive Black Holes and their Host Galaxies at z > 6 with JWST
Clues on the formation of supermassive black holes may be found in the properties of their host galaxies and mass relations with cosmic time. We will present results from JWST programs based on the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) at z > 6. The detection of the host galaxies enables the first assessment of the intrinsic ratio between black hole mass and stellar mass with consideration of selection effects and measurement uncertainties. Furthermore, new results will be presented on the detection of lower mass black holes, which highlight a large population of undermassive black holes at z > 6 just beginning to be tapped by JWST.

08 September

Valerio De Luca (JHU)

Primordial Black Holes: a Gravitational Wave Quest
Primordial black holes are a fascinating family of black holes that may have formed in the early universe and are considered a potential candidate for the dark matter. After briefly reviewing their formation mechanism and evolution throughout cosmic history, we explore their detectability via gravitational waves. In particular, we focus on signals emitted both during their formation and from the merger of associated primordial binaries. Finally, we highlight potential smoking-gun signatures that could probe their existence in future gravitational wave observatories, such as the Einstein Telescope and LISA.

David Stark (JHU/STScI)

21cm Follow-up for the MaNGA Survey: Past Results and Future Directions
The HI-MaNGA survey is a large observing campaign using the 100m Green Bank Telescope to obtain 21cm measurements for galaxies in the SDSS-IV Mapping Nearby Galaxies at APO (MaNGA) survey. HI-MaNGA provides important constraints on the cold neutral atomic hydrogen gas, or HI, in the MaNGA sample. HI acts the fuel reservoir that sustains star formation over long timescales, so understanding the physical processes that influence it is critical to our understanding of galaxy evolution. I will describe the HI-MaNGA survey and its current status, as well as highlight some recent results using this data set. I will conclude with a description of future NSF-funded efforts to complete the survey, and use it to understand the wide diversity of HI depletion times in z~0 star forming galaxies. ~

15 September

Natalie Myers (JHU)

Tracing the Chemical Enrichment of the Milky Way using Star Clusters: Measurement and Analysis of Neutron Capture Elemental Abundances
The chemistry of stars in the Milky Way is a powerful tool for exploring the enrichment history of the Galaxy. With the all-sky spectroscopic surveys that are currently available to us, using chemistry as a means to study the evolution and history of the Milky Way and potentially characterize the ages of different stellar populations therein has flourished. Open clusters have long been used to determine ages of stars, helping to calibrate stellar evolution models and other methods of age dating stellar groups (e.g., gyrochronology and asteroseismology). In this work, we utilize the Open Cluster Chemical Abundances and Mapping (OCCAM) survey, which uses SDSS-IV/APOGEE to establish cluster membership and has already been used to study the chemical evolution of the Milky Way (Myers et al. 2022, Spoo et al. 2022). Using this infrared-based dataset as a foundation, we target stars with the Keck I and Magellan Baade telescopes to collect high-resolution (R > 50,000), high-S/N (>75 at 5500A), optical spectra for 56 stars in 18 open clusters. With these data, we derive abundances for 23 elements using BACCHUS, including 7 neutron capture abundances not measurable by APOGEE. Finally, we use these neutron capture abundances to characterize the distribution of these elements radially and chronologically in the Milky Way. We find that elements in the neutron-capture families exhibit significantly flatter gradients as compared to the lighter alpha and iron-peak elements. In addition, we find the abundance each of the elements exhibits large scatter and little mean variation through time. These results could indicate that the enrichers for the heavier elements are well-distributed throughout the Milky Way's thin disk, and that the ISM has stayed relatively well-mixed through time.

29 September

Sangeeta Malhotra (GSFC)

Cosmic Dawn: Gaps in Our Understanding
Wide area surveys from the ground going up to redshift 7, and sensitive JWST observations over smaller fields, both indicate that the reionization history of the universe is more complex than expected. I will discuss the gaps in our understanding of the reionization epoch, and what is needed from future missions such as Roman and HWO to understand our origins.

06 October

Joshua Hibbard (Colorado)

Forward to the Moon: Lunar radio telescopes and 21-cm Cosmology
The lunar farside provides an exceptionally radio-quiet environment for next-generation low-frequency cosmology, particularly measurements of the redshifted 21-cm line from the Cosmic Dawn and Dark Ages. This signal encodes the thermal and ionization history of the intergalactic medium, constrains the timing of the first luminous sources, and probes small-scale density fluctuations sensitive to dark matter and dark energy. Ground-based detection is precluded by anthropogenic interference, ionospheric opacity below ~40 MHz, and environmental variability. A radio telescope on the farside of the Moon, however, overcomes these difficulties. NASA’s first surface radio instrument, ROLSES, flew on the Odysseus CLPS lander in 2024, and despite a rocky landing, measured spectra from 2 kHz–30 MHz and detected terrestrial techno-signatures and placed soft constraints on the galactic background. Successor missions include LuSEE-Night (launch 2026), the first dedicated farside low-frequency telescope designed to access the unexplored Dark Ages band (1–50 MHz) with active EMI mitigation and orbital calibration, and ROLSES-2 (2028), an enhanced instrument with improved thermal tolerance, shielding, and full Stokes capability. These pathfinders will establish the technological and scientific foundation for future interferometric arrays capable of tomographic mapping of the early Universe, such as the NIAC-concept lunar interferometer arrays called Farview, or other large telescope concepts such as the Lunar Crater Radio Telescope.

13 October

Sanskriti Das (Stanford)

Where the Hot Universe Meets the Energetic Universe
The hot circumgalactic medium (CGM), a reservoir of missing baryons, metals, and energy, plays a key role in our understanding of galaxy evolution. However, extraordinary observational challenges make the hot CGM one of the least understood components of galaxies. Studying the hot CGM was not the objective of current X-ray or mm facilities during the design phase. However, as an excellent byproduct, observing the hot CGM has emerged as a promising field over the last two decades, coming at the forefront of priority science goals for the current and upcoming decades. I will discuss three snippets of our recent efforts to detect and characterize the hot CGM: 1) X-raying the Milky Way: Investigating thermal and chemical anomalies; 2) Is CGM detectable? Conducting deep searches in individual external galaxies using X-ray, and 3) Test for self-similarity: stacking thousands of galaxies in mm (Sunyaev-Zeldovich Effect). I will highlight how our findings provide insights into the impact of galactic feedback on the hot CGM, establish our confidence in leveraging current telescopes to inform theoretical simulations, and set a benchmark for designing experiments with next-generation X-ray and mm facilities.

20 October

Raphael Errani (CMU)

How Micro Galaxies Could Help Constrain the Properties of Dark Matter
Guided by the recent discovery of the faint Milky Way satellite UMa3/UnionsI, in this talk I will present the results of our controlled high-resolution simulations to discuss how ”micro galaxies” could be distinguished observationally from self-gravitating star clusters, and how such systems would help us to constrain both the properties of dark matter and the physical processes underlying the formation of the faintest of galaxies. Micro galaxies are a plausible prediction of Cold Dark Matter (CDM) cosmology: The centrally divergent density cusps of CDM subhaloes render them remarkably resilient to tides. Heavily stripped tidal remnants of the Milky Way accretion may survive even in the strong tidal field of the inner regions of our Galaxy. Some of these tidal remnants may have been sufficiently massive in the past to allow for star formation within their potential wells, giving rise to a population of micro galaxies: co-moving groups of stars, gravitationally supported by the dark matter subhalo which surrounds them.

27 October

Emily Witt (JHU)

The Juniper CubeSat Concept: A Mission to Observe CGM Kinematics in Nearby Galaxies
The circumgalactic media (CGM) of galaxies play a key role in the baryon cycle of galactic feedback. Ultraviolet (UV) radiation from the CGM in particular is crucial to understanding the flow of gas and metals into and out of galaxies, probing warm/hot gas in the CGM that forms the transition between hot gas that remains in the galaxy's halo and cooler gas that recycles into the galaxy, feeding star formation and evolution. To characterize this process, the Juniper 16U CubeSat mission concept has been under development at Johns Hopkins University and the University of Colorado. Juniper will conduct observations of the CGM of nearby galaxies in multiple far ultraviolet (FUV) bandpasses that include key metal lines such as O VI (103.5 nm), C II (133.5 nm), and C IV (154.9 nm). The instrument is enabled by an innovative dual-grating optical design, Xenon-enhanced Lithium Fluoride (XeLiF) thin film coatings being considered for use on Habitable Worlds Observatory, and a FUV-sensitive photon-counting MCP detector. The use of these technologies results in Juniper's unprecedented spectral resolution, permitting for the first time the detailed study of the kinematics of the warm/hot gas in the CGM and how the material moves and cycles through the galaxy.

Leah Jenks (JHU)

Inflation as a Particle Factory
Cosmological gravitational particle production (GPP) is the process by which particles are created due to the expansion of spacetime during inflation. In this talk I will give an overview of GPP and discuss two scenarios in which it leads to highly efficient particle production. First, I will show how GPP of scalar fields in Higgs inflation models leads to a characteristic peaked spectrum and enhanced particle number. Then I will discuss GPP of dark photons with non-minimal couplings to gravity, which similarly leads to an enhancement of the particle number, but also instabilities. Finally, I will comment on phenomenological implications of these scenarios for dark matter.