Rieko Momose, Carnegie Observatories
The relationship between IGM and galaxy as probes of the cosmic web
Mapping the large-scale matter density distributions, known as the cosmic web, in observations is essential in Astronomy studies, such as determining cosmological parameters, identifying overdensities (e.g., protoclusters), and understanding the link between galaxy evolution and the cosmic web. The observational probe of the cosmic web is the large-scale distribution of galaxies and the intergalactic medium (IGM). As galaxies and IGM trace the same dark matter, one would expect spatial correlations between them. However, their distributions and relationships in the real universe are not well known. This project studied the spatial connection between galaxies and the IGM through cross-correlation analysis using the Lyα forest tomography data, CLAMATO, and several galaxy catalogs at z = 2 in the archive. We also investigated the dependence of the IGM-galaxy connection on galaxy types. In this talk, I will show similarities and differences in the cross-correlation function among galaxy types, particularly focusing on [OIII] emitting galaxies, Lyα emitting galaxies, and active galactic nuclei (AGN), which are well-used tracers of the cosmic web and protocluster. I will also discuss the impact of IGM opacity on the observability of galaxies.

Christian Aganze, UCSD
Prospects for Detecting Gaps in Globular Cluster Stellar Streams in M31 and Other External Galaxies with the Nancy Grace Roman Space Telescope
Stellar streams form through the tidal disruption of satellite galaxies or globular clusters orbiting a host galaxy. Globular cluster streams are of special interest because as thin streams they can exhibit gap-like features that can be formed through interactions with dark matter subhalos. These gaps thus provide constraints for dark matter models: different prescriptions for the dark matter particle predict different subhalo mass functions. However, the currently known globular cluster streams and stream gaps are limited to the Milky Way. With its large field of view (0.28 sq. deg.), deep imaging sensitivity, and high resolution, the Nancy Grace Roman Space Telescope presents a unique opportunity to significantly increase the number of observed globular cluster streams and gaps. In this talk, I will present a first exploration of the prospects for detecting gaps in streams in M31 and other nearby galaxies. Using a Pal 5-like stream, we model an encounter with a dark matter subhalo with a relative speed of 50 km/s, and we generate mock observations of this encounter together with background stars in M31 and foreground stellar Milky Way fields. We assess Roman’s ability to detect gaps out to 10 Mpc both by visual inspection and by using a recently-developed gap-finding tool (Contardo et al. 2022). We conclude that gaps from subhalos of masses > 5 x 10^6 solar masses are detectable within a 2-3 Mpc volume for exposure times between 1000s and 1 hour. The compilation of a large sample of these gaps in external galaxies will open up a new era of statistical analyses of gap characteristics in thin stellar streams and help constrain dark matter models.