Astrophysics seminars

Zack Gelles examines how black-hole rotation twists magnetic fields near light cylinders, where plasma accelerates into inflows and outflows. Semi-analytic models and simulations connect this structure to polarization changes detectable with radio interferometry, offering constraints on black-hole spin and relativistic jets. Kritti Sharma presents fast radio bursts as probes of cosmic baryons. Dispersion measures and secure host redshifts constrain gas in galaxy groups and clusters, while correlations with large-scale structure and other tracers map matter along burst sight-lines. The talk considers how future burst surveys can measure baryonic feedback and its evolution alongside other cosmological observations. Online via Stanford KIPAC Zoom. Friday 25 September 2026, 10:40–11:30 PDT (America/Los_Angeles; UTC−7). Follow Join the zoom meeting on the event page. The organizer lists faculty, staff, members and students as the audience. This is one session with two speakers; individual talk start times are not supplied.

Paco Villaescusa surveys the growing role of numerical simulations and AI in cosmology. Quijote and Backlight explore how much information about the Universe can be recovered beyond conventional summary statistics, including nonlinear structure and higher-order relationships. CAMELS addresses uncertainty in galaxy formation and other astrophysical processes, while DREAMS examines dark-matter predictions in the presence of baryonic effects. The seminar then considers automated research workflows through Denario, a system that develops hypotheses, plans analyses, writes and executes code, and interprets results. It discusses possibilities opened by combining simulation libraries with coordinated AI systems, while framing these as research directions. The speaker is a computational cosmologist at the Flatiron Institute.

Lurdes Ondaro Mallea examines whether current models of the kinematic Sunyaev–Zeldovich signal accurately recover diffuse baryons and the strength of astrophysical feedback. The analysis uses hydrodynamic simulations to generate mock stacked measurements for realistic DESI-like galaxy samples, separating contributions from gas density, velocities and nonlinear astrophysics. It tests baryonic changes to density and velocity fields, satellite galaxies, nonlinear velocities and velocity reconstruction. Neglecting satellites can underestimate halo gas fractions at today's measurement precision; further corrections become significant for future datasets. The talk explains how including these effects can improve gas-distribution measurements and assessments of feedback. Online via Zoom. Monday 28 September 2026, 11:00–12:00 PDT (America/Los_Angeles; UTC−7). Follow Join the zoom meeting on the organizer's event page. Lurdes Ondaro Mallea is affiliated with Cambridge. Organized by the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), Stanford University. This listing advertises the verified remote option.

Jared Siegel presents measurements that address two limitations of weak-lensing cosmology: intrinsic galaxy alignments and baryonic feedback. More than two million DESI galaxies and four lensing surveys provide alignment measurements across colour, luminosity, stellar mass and redshift. Combining Sunyaev–Zel’dovich profiles, eROSITA gas fractions and galaxy–galaxy lensing then constrains how feedback redistributes matter in groups and clusters at redshifts between zero and one. The results indicate stronger gas expulsion beyond virial radii than many simulations predict, reducing small-scale matter power. Incorporating these empirical constraints into cosmic-shear analyses improves cosmological inference. Online via Stanford KIPAC Zoom. Friday 9 October 2026, 10:40–11:30 PDT (America/Los_Angeles; UTC−7). Follow Join the zoom meeting on the official event page. The organizer lists faculty, staff, members and students as the audience. This listing advertises remote attendance.

Marta Bryan explores what gas giants reveal about the formation and evolution of planetary systems. Their brightness and mass make them useful observational targets, and their gravitational influence can reshape the orbits and environments of smaller planets. The seminar combines several approaches. High-resolution spectroscopy of directly imaged planets measures rotation and obliquity, providing evidence about angular-momentum evolution. Radial-velocity searches for Jupiter-like companions to known inner planets probe how giant planets affect system architecture and inform the search for habitable worlds. The presentation also introduces observational work on planetary interiors and magnetic fields as further ways to test formation models.

Lyman Page introduces temperature variations and polarization in the cosmic microwave background for researchers outside cosmology, explaining how these measurements underpin the standard cosmological model. He then considers what that model leaves unresolved, especially whether gravitational waves originating in the early Universe are detectable. The talk reviews the Simons Observatory’s experimental search for those primordial signals and its role in addressing this question. Online via Zoom Events in the John Bahcall Colloquium, hosted by the Institute for Underground Science at SURF. The free series welcomes the scientific community across career stages. Wednesday 14 October, 09:00–10:00 MDT (America/Denver), equivalent to 15:00–16:00 UTC. Follow Register on the organizer page, then select this dated session in the Zoom Events registration list.