Description:

The groundbreaking detection of gravitational waves from merging black holes has forever changed how we observe the Universe. Upcoming detectors, like the Laser Interferometer Space Antenna (LISA), will unlock new opportunities by allowing us to detect mergers between stellar-mass black holes (tens of solar masses) and supermassive black holes (SMBHs, millions to billions of solar masses). These fascinating events, known as extreme-mass-ratio inspirals (EMRIs), provide a wealth of information about the dynamics near SMBHs. A key formation channel for EMRIs involves weak gravitational interactions—two-body kicks—from surrounding stars and compact objects that gradually alter the small black hole's orbit, eventually driving it into the SMBH. However, the picture changes when we consider the presence of SMBH companions, which can induce high orbital eccentricities, further enhancing EMRI formation. In this talk, I will show that combining these two processes is crucial for understanding the progenitors of EMRIs. Moreover, I will demonstrate that SMBH binaries create EMRIs more efficiently than either process alone, making it truly rain black holes!  This scenario results in a substantial stochastic gravitational wave background for future detectors like LISA. Finally, I will also discuss how this mechanism affects tidal disruption events and address the tantalizing question: Is it raining stars, too?

Speaker: Smadar Naoz, UCLA

Host: Fred Rasio

Description:

Supermassive black holes are ubiquitous in the nearby Universe. AGN feedback is thought to be a key mechanism that regulates the growth of supermassive black holes and their joint evolution with their host galaxies. How and when did these mysterious objects form? How did they grow quickly enough to power high-redshift quasars? I will summarize the demographics of supermassive and intermediate-mass black holes in the local Universe, their connection to  galaxies, and  recent discoveries made with the JWST that offer important, new insights on the earliest phases of black hole growth and their impact on galaxy evolution during the first billion years after the Big Bang.

Speaker: Luis Ho, Director, The Kavli Foundation

Host: Fred Rasio

Description:

JWST has shown us that the galaxy population in the high redshift Universe is richer and more complex than we had anticipated. Among the surprising findings is the presence of seemingly massive and very compact galaxies when the Universe was only ~600 Myr old. It has been suggested that they "break" the Universe, in the sense that they should not have been able to form this early. The talk will review these early studies and follow-up work, and try to differentiate between results that are firm and those that are still uncertain. One of the intriguing uncertainties is the role of black holes, both in the early phases of galaxy formation and in the interpretation of observations.

Speaker: Pieter van Dokkum, Yale University

Host: Allison Strom

Description:

CIERA Colloquia feature distinguished external visiting researchers, and are a regularly occurring colloquia series held throughout the Fall, Winter, and Spring academic quarters. Colloquium speakers are invited to spend several days at CIERA.

Description:

The Young Supernova Experiment (YSE) is an optical time-domain survey using the two Pan-STARRS and CTIO Blanco telescopes, and a myriad of spectroscopic follow-up facilities. Our survey is designed to obtain well-sampled griz light curves for thousands of transient events up to z ≈ 0.2 and tens of thousands of variable sources. This large sample of transients with four-band light curves will lay the foundation for the Vera C. Rubin Observatory and the Nancy Grace Roman Space Telescope, providing a well-calibrated low-redshift anchor of cosmologically useful SNe Ia to study the equation-of-state of dark energy and its evolution. But YSE is much more than a type Ia supernova cosmology experiment, and as the name suggests, YSE discovers transients as faint as ~21.5 mag in gri and ~20.5 mag in z with Pan-STARRS and 1.5 magnitudes deeper with DECam - depths that allow us to probe the earliest epochs of stellar explosions. YSE therefore also provides a critical training set, allowing the new NSF-Simons SkAI Institute to develop foundation models for forecasting, anomaly detection and much else for use with Rubin Observatory. I will provide a flavor for some of the many science cases that YSE enables, highlighting a few key results, and how YSE and SkAI together can enable on-the-fly inference for every transient discovered by Rubin Observatory, revolutionizing time-domain astrophysics.

Speaker: Gautham Narayan, Associate Professor, University of Illinois, Urbana-Champaign

Host: Tjitske Starkenburg