Understanding the first galaxies

The James Webb Space Telescope has ushered in a new era for the study of the first galaxies. Yet, at the furthest epochs, the faintest but most abundant galaxies remain extremely difficult to constrain, motivating the search for indirect ways of determining their nature. One indirect probe of the first galaxies is Reionization. However, interpreting IGM observations (including upcoming high-redshift 21cm observations) requires a thorough theoretical investigation. At the same time, new observations of unexpectedly luminous high redshift (z>10) galaxies continue to challenge our theoretical models of galaxy formation. Some of these early galaxies are already quenched by z=7, which cosmological simulations fail to explain. In this talk, I will highlight various numerical projects that investigate these issues. First, I will show how simulations can help up better understand how the first galaxies reionize the Universe, and interpret the correlation between galaxy observations and the intergalactic medium. Second, I will explore the relationship between forming early massive black holes and quenching massive high-redshift galaxies, and how simulations could help us better appreciate observational biases in constraints on quenching.

Shedding light on the gaseous cosmic web : star formation patterns from cosmic filaments to clusters

The study of star formation patterns across large populations of galaxies is poised to open a new window into our understanding of structure formation in the Universe. In particular, it promises to expose the faint, gaseous components of the cosmic web, the complexity of which remains largely out of sight of observational programs. Indeed, from environmental quenching in clusters to dwarf galaxy rejuvenation in voids, there is no shortage of star formation patterns that suggest a strong connection between the underlying dynamics of cosmic gas and galaxy evolution. Once confined to largest cosmic filaments detected in spectroscopic surveys, these studies can now extend to the dwarf and faint galaxy regime with the advent of highly sensitive synoptic surveys like LSST and EUCLID, revealing smaller and smaller scales of the gaseous cosmic web. In this talk, I will review existing evidence for the web-star formation connection across vastly different scales of the cosmic web. After a review of what is known for large spectroscopic cosmic filaments, I will discuss the pervasiveness of hydrodynamic anisotropies inherited from cosmic filaments down to the heart of populated clusters and Milky-Way mass halos. I will show how, in simulations, these affect satellite galaxies' gas reservoirs and ultimately star formation, and how z=0 features in the satellite distributions of Milky-Way like galaxies can already provide insights onto complex evolutionary aspects of the cosmic web on smaller scales. I will then review emerging evidence of star formation patterns correlated on cosmic scales in the local Universe and detail how this may be understood within the context of multiscale filament dynamics. Eventually, I will discuss avenues for further exploration with EUCLID and LSST.