Speaker: Boryana Hadzhiyska (Harvard University)
Forward modeling in the era of cosmological surveys
Upcoming cosmological surveys will measure the large-scale distribution of galaxies at the subpercent level. In order to extract unbiased cosmological data while retaining valuable small-scale information, we need highly accurate models of the connection between galaxies and (dark) matter. While cosmological hydrodynamical simulations are too small and computationally expensive to directly use in the analysis of galaxy observations, they provide a detailed probe of the galaxy-halo link. We show that the simplest galaxy-halo model, the mass-only halo occupation distribution (HOD), fails to capture the galaxy clustering at the15% level, which is well beyond the 1% requirement set by current and future experiments. We develop augmented models which reproduce multiple galaxy distribution statistics by the hydro simulation. We develop a pipeline for applying these models to observational data and show that in their crudest form, they manage to alleviate existing tensions (e.g., Lensing is low).
Speaker: Geert Raaijmakers (University of Amsterdam)
Unraveling neutron star interiors with multimessenger observables
"One of the unsolved fundamental questions of modern astrophysics is the behavior of matter at extreme densities and pressures, as found in the core of neutron stars. Over the past few years great progress has been made thanks to the dedicated X-ray timing telescope Neutron Star Interior Composition Explorer (NICER), accurately measuring for the first time the mass and radius of a neutron star. I will explain how these measurements are made and how we can use them to constrain the neutron star interior, combining them with the first groundbreaking gravitational wave detections of merging neutron stars. Finally I will discuss how multimessenger detections of gravitational wave events with electromagnetic counterparts can play a crucial role in constraining dense matter behavior over the next few years."
