Astrophysics Colloquium schedule
Wednesdays, 3:30-4:30 pm
The Astronomy Colloquia Meetings are held in the P&A building, room 1-434. Zoom information sent in email.
The UCLA Department of Physics & Astronomy Astrophysics group established the Astrophysics Colloquium speaking series 20+ year ago. Throughout the academic year, distinguished speakers travel to UCLA to share their latest research. The department sponsors and organizes these events to encourage collaboration within the field. This exposure is critical for our graduate students particular. The content shared in these events broaden their academic horizons. Additionally, the colloquium provide opportunities for our students to network with other specialists and peers.
Can’t make these times? Watch the Astrophysics Colloquium recordings on our newly minted YouTube channel here! Big thanks to our to our donor and program alumnus, Robert J. Altizer '70 BA Astronomy & Astrophysics, for making this repository possible.
Help us continue this enriching speaking series by making a donation online here. Gifts to the Astronomy and Colloquium Fund offset event costs including those related to speaker travel. Support from our event attendees and donors is greatly appreciated. For check instructions or other giving related questions, please contact Madeleine Martin at mmartin@support.ucla.edu or (310) 882-3633.
Fall 2025
October 8, 2025
Pablo G. Pérez-González (Centro de Astrobiología, CSIC-INTA)
The rise of the galactic empire: probing the very first stages of galaxy formation with JWST
Abstract: I will present a multi-angle approach to understand when galaxies started forming in the Universe. One approach is directly probing the highest redshifts, specifically in our case, building galaxy samples and determining luminosity functions at z=8-25 based on the deepest JWST/NIRCam surveys (MIDIS+NGDEEP). The second approach involves studying the fossil record found in galaxies at different redshifts (we focus on 3<z<7) for which reliable star formation histories are determined with a 2-dimensional technique. I will discuss how our observational results compare with state-of-the-art galaxy formation simulations.
October 15, 2025
No colloquium
October 22, 2025
Jason Wang (Northwestern University)
New Frontiers in Exoplanet Imaging and Pathways to Habitable Worlds
Abstract: By spatially resolving faint planets from their bright host stars, we can directly image exoplanets and characterize them as individual worlds. Exoplanet imaging is limited by our ability to separate the signal of the planet from the bright glare of the star. I will discuss novel techniques that allow us to better image exoplanets and, if placed on the next generation of observatories, have the potential for us to study habitable worlds. First, I will present significant improvements to the sensitivity of JWST high-contrast imaging thanks to new data analysis algorithms that utilize techniques from computational imaging that better leverage our knowledge of physics. Next, I will discuss the Roman Space Telescope Coronagraph Instrument, which will demonstrate high-order wavefront control in space and potentially image a planet in reflected light for the first time. I will also discuss how we can use the additional properties of light to improve exoplanet imaging. The Keck Planet Imager and Characterizer (KPIC) combines high spatial and spectral resolution to allow us to spectrally resolve molecular absorption lines in the atmospheres of directly imaged planets. Long-baseline interferometry with VLTI/GRAVITY gives us the spatial resolution of a 140-meter telescope, enabling precise measurements of fundamental exoplanet properties. I will highlight recent science results from these instruments, summarize lessons learned in pioneering these techniques, and discuss their prospects for imaging habitable worlds on the next generation of observatories.
October 29, 2025
John Chisholm (UT, Austin)
A GLIMPSE of the faintest galaxies in the first billion years
The James Webb Space Telescope (JWST) has pushed the redshift frontier to within the first few hundred million years of cosmic history. The earliest galaxies it has uncovered are both brighter and more numerous than pre-JWST models predicted, with surprising abundance patterns that challenge our understanding of early galaxy formation and evolution. While these luminous systems have reshaped our view of the early universe, a vast population of fainter galaxies—hidden below traditional detection limits—holds crucial clues to how the first galaxies assembled and evolved.
In this talk, I present initial results from JWST’s GLIMPSE survey, a Cycle 2 ultra-deep imaging and spectroscopy program targeting Abell S1063, a massive foreground galaxy cluster. The combination of long integrations and gravitational magnification enables the detection of extraordinarily faint galaxies at the edge of the observable universe. I will discuss early findings on the faint-end number density, the diverse physical properties of faint galaxies, and their role in cosmic reionization. These observations offer an unprecedented glimpse into the faintest galaxies that populated the early cosmos.
November 5, 2025
No colloquium - AstroBash
November 12, 2025
Assaf Horesh (The Hebrew University of Jerusalem HUJI)
The Radio Awakens — A New Phenomenon in Tidal Disruption Events
Abstract: When a star is torn apart by a supermassive black hole, a tidal disruption event (TDE) unfolds, producing luminous flares across the electromagnetic spectrum. Radio observations, in particular, provide unique insights into the resulting outflows and the circumnuclear environment. In this talk, I will review what we have learned from radio studies of TDEs and present a newly discovered phenomenon — delayed radio flares, emerging months to years after the initial disruption. I will discuss possible physical origins, including accretion state transitions, delayed ejecta, and off-axis jets, and show evidence that such flares are relatively common. These results may open a new window into how black holes launch outflows.
November 19, 2025
Mor Rozner (University of Cambridge)
From Few-Body to Stellar Clusters: How Gas Reshapes Dynamical Evolution
Abstract: Gas-rich environments are ubiquitous across various scales, from protoplanetary discs to star clusters and galaxies. Dynamics in these environments are substantially different and give rise to unique astrophysical phenomena, while also enhancing the rates of well-studied ones. In this talk, I will demonstrate some of the unique processes in gas that alter the dynamics in several environments, including nuclear star clusters (NSCs), globular clusters (GCs), and star forming regions; if time allows, I will also discuss protoplanetary discs. I will discuss stellar distributions in gas-rich NSCs, their signatures, and implications for the rates of tidal disruption events (TDEs) and other transients in galactic nuclei. The behaviour of binaries in gas-rich environments also differs qualitatively from that in gas-free regions, leading to enhanced formation of hard binaries, preservation of fragile soft binaries, and even gas-assisted formation of binaries. The abundance of close binaries could potentially contribute to a unique gravitational wave channel in gas.
November 26, 2025
No colloquium - Thanksgiving week
December 3, 2025
Andreas Faisst (Caltech, California Institute of Technology)
Tracing Resolved Star Formation, Dust, and Gas through 12 Billion Years of Cosmic Time
Abstract: For obtaining a complete picture of galaxies, multi-wavelength observations are crucial to observe their stars, gas, dust, and chemical composition. With Hubble, JWST, and ALMA operating at the same time, we find ourselves in an era where we can jointly observe the UV, optical and infrared light. In my talk, I will present recent results obtained by the synergy of these observatories on the chemical and structural evolution of galaxies from the Epoch of Reionization to Cosmic Noon. I will introduce the contribution of three new programs with JWST (ALPINE NIRSpec/IFU program and MIRI/MRS PAH survey) and ALMA (CHAMPS 1.2mm survey) with which we will study the chemical compositions of z=4-6 galaxies, search for the most dust-obscured sources during the Epoch of Reionization, and measure for the first time spatially resolved PAH dust emission in z=1 galaxies. I conclude by highlighting the important future contributions to these topics by SPHEREx.