Tirso Marin Gilabert (Harvard CfA)

Viscous or Turbulent? Interpreting XRISM’s Coma Puzzle with High-Resolution Simulations

The evolution of galaxy clusters is strongly shaped by the physics of the intracluster medium (ICM), where processes such as turbulence, mixing, and alaxy–ICM interactions drive much of the cluster’s dynamical state. One key ingredient in this picture is viscosity, which regulates how efficiently turbulence cascades, how density fluctuations develop, and how magnetic fields evolve. Yet, despite its importance, the level of viscosity in the ICM remains uncertain.

In this talk, I will present results from high-resolution cosmological simulations that explicitly include viscosity, with a particular focus on the Coma cluster. I will show how viscosity affects the cluster morphology, turbulence, and ICM fluctuations compared to inviscid cases, and discuss how these signatures can be connected to observations. I will explore how simulations can help us interpret these results and provide indirect constraints on the effective viscosity of the ICM, particularly comparing with Coma observations. This study is expected to enhance our understanding of ICM dynamics
and contribute to our knowledge of galaxy cluster evolution.

Biography: Tirso Marín obtained his PhD from the Ludwig Maximilian University of Munich, working with Klaus Dolag on transport processes in cosmological simulations of galaxy clusters. He recently joined the CfA as a postdoc with John ZuHone, where he works on cluster merger simulations to understand how viscosity and other transport processes shape the intracluster medium.

Jakob Helton (Penn State University)

At the Break of Cosmic Dawn: JWST/MIRI Reveals the Detailed Physical Properties of JADES-GS-z14-0

JWST has discovered an early period of galaxy formation that was more vigorous than expected. As one of the best archetypes for this period of early galaxy formation, JADES-GS-z14-0 was spectroscopically confirmed at z > 14. Beyond its extreme redshift, this galaxy is remarkably luminous and reddened. It is spatially extended in the rest-frame ultraviolet and therefore dominated by stellar light at those wavelengths. Most notably, it was detected at 7.7 microns with JWST/MIRI, and the measured flux density is in excess above that measured with JWST/NIRCam. At this redshift, less than 300 million years after the Big Bang, the measured flux excess is caused by nebular emission from hydrogen and ionized oxygen. In this talk, I will present recently acquired follow-up observations consisting of the longest spectroscopic integration ever acquired by JWST/MIRI. By targeting the rest-frame optical emission lines and continuum, these observations will reveal important insights into the physical properties of JADES-GS-z14-0: gas-phase metallicity, electron density, and dust attenuation to better understand the interstellar medium, including the formation of the first heavy elements; ionizing photon production efficiency and ionization parameter to better understand the intrinsic ionizing spectrum; and the complete star formation history to better understand the stellar populations, including the formation of the first stars. By determining and constraining the physical properties of JADES-GS-z14-0, my observing program represents an important first step toward explaining the surprising abundance of luminous galaxies in the early Universe.
Bio: I am currently an Evolving Universe Postdoctoral Fellow at The Pennsylvania State University. I received an A.B. in astrophysical sciences from Princeton University along with an M.S. and Ph.D. in astronomy and astrophysics from the University of Arizona. I am one of the key members for two of JWST’s Instrument Science Teams — the Mid-Infrared Instrument (MIRI) and the Near Infrared Camera (NIRCam); I am also a key member of the JWST Advanced Deep Extragalactic Survey (JADES) as the working group lead for grism science.

Biography: Jakob is currently an Evolving Universe Postdoctoral Fellow at The Pennsylvania State University. He received an A.B. in astrophysical sciences with high honors from Princeton University in addition to an M.S. and Ph.D. in astronomy and astrophysics from the University of Arizona. Jakob spends his time studying (#1) high-redshift galaxies, (#2) high-redshift galaxy clusters, and (#3) the large-scale structure of the Universe. He is a key member of the James Webb Space Telescope (JWST) Advanced Deep Extragalactic Survey (JADES) in addition to the Mid-Infrared Instrument (MIRI) and Near Infrared Camera (NIRCam) Science Teams. His contributions to extragalactic astronomy have been featured in national and international press, and he has worked to share work and acquired knowledge with the broader community. In addition to his research, Jakob is also a visual artist, focusing on photography and painting.