Colloquia AbstractsSUBJECT TO CHANGE! Be sure to check back often
Colloquia are not recorded.
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Caffe AP
Date: Friday 9 October 2026Time: 3pm - 4pm (ADT)Venue: AT 101
Illuminating the First Galaxies and the Epoch of Reionization: New Insights from JWST
Lily WhitlerCambridge
Date: Friday 16 October 2026Time: 3pm - 4pm (ADT)Venue: AT 101
In the first billion years of cosmic time, the earliest luminous sources -- stars and accreting black holes in galaxies -- formed and drove a global phase transition of hydrogen in the intergalactic medium known as the Epoch of Reionization. In recent years, JWST observations have shifted the paradigm of our understanding of these earliest galaxies, which played a key role in shaping the Universe as we know it today. In this talk, I will review a sampling of recent results probing the reionization process with observations of z≳8 galaxies. In particular, I will discuss the unexpectedly large abundance of luminous galaxies at unexpectedly high redshifts discovered by JWST, potentially pointing to previously unknown physical processes governing early star formation and a large population of galaxies driving the reionization process. I will then discuss these results in context with insights into the properties of ionized bubbles at z≳7 obtained from JWST spectroscopy of Lyman-alpha emission in reionization-era galaxies. I will particularly emphasize the power of simultaneously studying reionization and the properties of the earliest galaxies, and will discuss prospects and challenges for making the connection between galaxies and reionization with JWST and near-future facilities.
The World of Webb, the Cosmic Circle of Life, and Seeing through the Eyes of Einstein
Rogier WindhorstArizona State University
Inside the nucleus, inside the stars : Experimental constrains on X-ray Bursts and proton-rich nucleosynthesis with MUSIC
Eilens Lopez-SaavedraArgonne National Laboratory
Date: Friday 30 October 2026Time: 3pm - 4pm (ADT)Venue: AT 101
Understanding dense stellar environments with gravitational wave catalogs
Aditya VijaykumarCanadian Institute for Theoretical AstrophysicsChicago
Date: Friday 6 November 2026Time: 3pm - 4pm (AST)Venue: AT 101
Fall Break - No TalkFriday 13 November
Jason HesselsMcGill University
Date: Friday 20 November 2026Time: 3pm - 4pm (AST)Venue: AT 101
Monitoring Pluto’s Atmospheric Evolution via Stellar Occultation Data
Michael PersonMIT
Date: Friday 27 November 2026Time: 3pm - 4pm (AST)Venue: AT 101
A 3-dimensional holographic picture of the pion
Ruben SandapanAcadia University
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Evidence for the First Globular Cluster Stellar Stream beyond the Milky Way
Julie Kiel HolmCopenhagen
Date: Friday 2 October 2026Time: 3pm - 4pm (ADT)Venue: AT 101
Globular clusters can lose stars because of a galaxy’s gravity, creating stellar streams—long trails of stars that can reveal information about the galaxy’s dark matter and gravitational structure.
This talk presents evidence for what may be the first globular cluster stellar stream discovered outside the Milky Way, located in an ultra-diffuse galaxy. Researchers model the stream and use generative modelling to study the galaxy’s dark-matter halo.
The discovery is important because stellar streams are sensitive to dark-matter substructures. Future observations from the Euclid and Roman Space Telescopes are expected to find more extragalactic streams, providing new ways to study dark matter across different types of galaxies
SMHr-IL: A Tool for High-Resolution Integrated Light Spectroscopy
Charli SakariSan Francisco State University
Date: Friday 25 September 2026Time: 3pm - 4pm (ADT)Venue: AT 101
Integrated light (IL) spectroscopy provides a way to investigate the detailed chemical abundances of distant globular clusters through high-resolution spectroscopy. Detailed abundances of elements like Na, Mg, Ca, Ba, and Eu provide insight into the birth sites of these clusters, the assembly histories of the host galaxies, and the nature of multiple populations within the clusters. In this talk, I will discuss work we are doing at San Francisco State University to develop a new version of the code Spectroscopy Made Hard(er), or SMHr, for IL spectroscopic analysis. SMHr-IL enables automation and standardization of several steps of the analysis, while requiring user input during crucial steps such as line measurements. I will discuss the progress we have made so far and our goals for the future.
The Frisky Infancy of Galaxy Growth Revealed with JWST
Karina CaputiGroningen
Date: Friday 18 September 2026Time: 3pm - 4pm (ADT)Venue: AT 101
Low-mass galaxies (with stellar masses < 10^9 Msun) are fundamental to understand the first steps of galaxy growth. For many years, the study of dwarf galaxies in the local Universe has given us a glimpse of the conditions that would likely have applied to their analogues at early cosmic times. Now, thanks to the superb sensitivity of JWST, we can directly study in detail the properties of significant samples of low-mass sources up to the Epoch of Reionisation and beyond. In the first part of this talk I will briefly review some of the crucial aspects that we have learned about star-formation activity in low-mass galaxies in the first few billion years of cosmic time. I will particularly discuss the importance of burstiness and its effect on galaxy spectral lines and derived parameters. In the second part of the talk, I will present our study of the Pseudo-LRD-NOM, a highly magnified low-mass galaxies at z~6 with very special spectroscopic properties: a very high Balmer decrement and a complete lack of metal lines. I will argue that the simple spectrum of this source provides evidence for complex physical conditions which are similar to those of Little Red Dots (LRDs), suggesting that the Pseudo-LRD-NOM could be a precursor to one of them.
A Search for Narrow-line Seyfert 1 Galaxies/Narrow-line Type-1 Quasars at z > 2 with Subaru PFS
Ayumi TakahashiKanagawa University
Date: Friday 11 September 2026Time: 3.30pm - 4.30pm (ADT)Venue: SB 265
Most galaxies have supermassive black holes at their center. These black holes might have co-evolved with their host galaxies, interacting with each other across cosmic history. We can identify supermassive black holes as active galactic nuclei (AGN) and quasars, which are among the most consistently bright objects in the universe. Beyond redshift 6, quasars with black holes exceeding 1 billion solar masses have been found; these observational findings pose a challenge to our understanding of how black holes grew from their seeds within such a short timescale. We would like to keep track of this investigation. However, such massive black holes have already matured and lost the memory of their early growth. Meanwhile, theoretical models imply that black holes can only grow by a factor of a few under sub-Eddington accretion, and that super- or high-Eddington accretion is a key parameter for black hole growth. Low black hole mass, high-Eddington ratio sources would represent the missing piece in the black hole growth pathway. Narrow-line Seyfert 1 galaxies are known to be low-mass, high-Eddington accretion objects in the local universe, and they, along with their bright analogs (narrow-line Type-1 quasars; NLQ1s), may represent such a population at high redshift as well.
We therefore launched the NLS1/NLQ1 search project using the Subaru Prime Focus Spectrograph (PFS). PFS is a massively multiplexed fiber spectrograph installed at the prime focus of the 8.2-meter Subaru Telescope. This instrument covers optical and near-infrared wavelengths with ~2400 science fibers distributed over a 1.3 deg2 field of view. Since this class has traditionally been identified using the Hβ and [OIII] lines, statistical studies of NLS1s at z>2 remain largely unexplored due to the observational limitations of ground-based telescopes. To extend a comprehensive understanding of this population to the more distant universe, we searched for broad-line AGNs (quasars) whose rest-frame UV spectral shapes resemble those of local NLS1 galaxies, utilizing the Lyα line profile. As a result, four NLQ1s at 2.5 - 6.1 were identified, and this z~6 object is one of the most distant NLS1 candidates. This is the first science result from the PFS-SSP (Subaru Strategic Program) project. I will introduce the current status of Subaru/PFS and this NLS1/NLQ1 search project.
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