Search Talks

Galaxy clusters assemble hierarchically, and their present-day dynamical state encodes information about cluster formation timescales and mass distribution. The diffuse intracluster light (ICL), a fossil record of tidal stripping and accretion, offers a complementary probe that is sensitive to a cluster’s assembly history. In this talk I will present recent works based on photometric surveys (Euclid, UNIONS, DESI Legacy, KiDS) and cosmological hydrodynamic simulations (e.g. IllustrisTNG, Hydrangea), addressing two questions: (i) how observational tracers (e.g. magnitude gaps, galaxy-stellar-mass ratios) can be used to identify cluster dynamical state and its imprint on cluster properties; and (ii) what the ICL fraction and morphology reveal about the underlying mass and the stage of assembly. If time allows, I will briefly describe ongoing work with the FLAMINGO simulations that connects high-redshift protoclusters to their descendant clusters using observational indicators of environment and assembly.

The Dark Energy Spectroscopic Instrument (DESI) is the largest galaxy redshift survey to date, aiming to catalog ~63 million galaxies over 17000 deg^2 of the sky by the end of 8 years of observation. The DR1 analyses were completed in 2024 with exciting new constraints on cosmological parameters within the standard LCDM model as well as extensions such as evolving dark energy. I will discuss the cosmological results from the DR1 fullshape and BAO analysis which was presented in the Fall of 2024 and the theory systematic tests/validation that went into it. I will then discuss the advantages of including cross correlations of DESI galaxies with CMB lensing and some key results from my joint analysis of 3D clustering with CMB lensing using the DESI DR1 galaxy sample and ACT DR6 and Planck PR4 lensing maps. In particular we find that just including galaxy-lensing cross-correlations on top of the fullshape and BAO analysis tightens amplitude constraints by ~30%. The second data release (DR2) spans three years of observation with analyses expected to be presented in Spring of 2026. I will briefly discuss the expected improvements in constraining power from DR2 and summarize the types of analyses that DESI will perform and their cosmological relevance.

The interstellar medium (ISM) plays an important role in sculpting the structure of our Galaxy: in addition to being the birthplaces of stars, ISM substructures have the capacity to significantly perturb stellar orbits. However, conventional stellar-dynamical studies often rely on idealized toy models or omit these gas “fluctuations” entirely, leaving their impact on the evolution of stellar systems poorly understood. In this talk, I will present a model for ISM fluctuations that is both theoretically tractable and easily incorporated into traditional N-body simulations, while retaining the essential features of a realistic ISM. The model is derived from a characterization of the ISM in the state-of-the-art TIGRESS magnetohydrodynamics simulations, which include self-consistent, first-principles gas microphysics and resolve scales down to 2 parsecs. I will then highlight several key differences between the dynamical effects of these realistic fluctuations and those assumed in prevailing models, focusing on orbital heating and radial migration in galactic disks. Finally, I will discuss the importance of accounting for the ISM’s influence in drawing robust conclusions about the Milky Way’s dynamical history and dark matter substructure.