lease join us for the CCAPP seminar next Tuesday, October 13th at 11:30 am. We will have two talks, given by Chun-Hao To (Stanford), and Kishalay De (Caltech).
Speaker: Chun-Hao To (Stanford)
Title: Cosmological constraints from a joint analysis of cluster abundances, galaxy correlations, and weak gravitational lensing in Dark Energy Survey
Abstract: Three cosmic tracer fields are measured from imaging surveys: galaxy density, weak gravitation lensing shear, and cluster density. The joint analysis of the auto and cross-correlations of the first two fields often referred to as the 3x2pt analysis, has become a popular and competitive cosmological test of the standard cosmological model. The abundances and spatial distributions of galaxy clusters, which are associated with the highest peaks in the matter density field, provide another powerful probe of cosmic structure formation and evolution; thus, the combination of cluster abundances and 3x2pt analysis is expected to yield precise cosmological constraints. In this talk, I will describe a novel multi-probe cluster cosmology analysis, which focuses exclusively on large scales. This new cluster cosmology analysis yields competitive cosmological constraints while being robust against several systematics. I will then present cosmological constraints from the first joint analysis of cluster abundances and auto/cross-correlations of all three cosmic tracer fields measured from the first year of the Dark Energy Survey (DESY1). The talk will be concluded by a discussion on the implication of the result, potential improvements, and expected constraining powers in the up-coming DESY3 analysis and future wide imaging surveys.
Speaker: Kishalay De (Caltech)
Title: The faintest thermonuclear supernovae and the explosive fates of helium accreting white dwarfs
Abstract: Accreting white dwarfs with He-rich companions are crucial for several key issues in modern astrophysics. While they have also been long proposed as progenitors of Type Ia supernovae from sub-Chandrasekhar mass white dwarfs, observations of the majority of Type Ia supernovae appear inconsistent with explosive He shell burning scenarios -- except for the faintest and fastest thermonuclear supernovae that have been difficult to systematically uncover in time-domain surveys. In this talk, I will present results from a systematic search for these elusive thermonuclear transients with the largest volume-limited sample of supernovae constructed till date using the Zwicky Transient Facility optical time-domain survey. I will discuss observational evidence that suggests that He shell explosions are realized in nature over a broad range of white dwarf core and shell masses -- ranging from peculiar Type Ia supernovae to the faintest class of 'Ca-rich' transients. Together, a systematic exploration of these unique explosions opens up a completely new window into the explosive fates of He-accreting white dwarfs and progenitors of Type Ia supernovae.
