We will have AstroParticle Lunch 11:30 AM (EDT) in Price Place and on Zoom.
We are excited to welcome two guests from The Chinese University of Hong Kong, Rui Hu and Wangzheng Zhang, who will join us on Zoom to discuss their recent papers. The titles and abstracts of the papers are below:
Speaker: Rui Hu
Title: Impact of light sterile neutrinos on cosmological large-scale structure
Abstract: Sterile neutrinos with masses on the eV scale are promising candidates to account for the origin of neutrino mass and the reactor neutrino anomalies. The mixing between sterile and active neutrinos in the early universe could result in a large abundance of relic sterile neutrinos, which depends on not only their physical mass but also their degree of thermalization, characterized by the extra effective number of relativistic degrees of freedom ΔNeff. Using neutrino-involved N-body simulations, we investigate the effects of sterile neutrinos on the matter power spectrum, halo pairwise velocity, and halo mass and velocity functions. We find that the presence of sterile neutrinos suppress the matter power spectrum and halo mass and velocity functions, but enhance the halo pairwise velocity. We also provide fitting formulae to quantify these effects.
Speaker: Wangzheng Zhang
Title: Measuring the Hubble constant through the galaxy pairwise peculiar velocity
Abstract: The Hubble constant H0, the current expansion rate of the universe, is one of the most important parameters in cosmology. The cosmic expansion regulates the mutually approaching motion of a pair of celestial objects due to their gravity. Therefore, the mean pairwise peculiar velocity of celestial objects, which quantifies their relative motion, is sensitive to both H0 and the dimensionless total matter density Ωm. Based on this, using the Cosmicflows-4 data, we measured H0 for the first time via the galaxy pairwise velocity in the nonlinear and quasi-linear range. Our results yield H0=75.5±1.4 km s−1 Mpc−1 and Ωm=0.311+0.029−0.028 . The uncertainties of H0 and Ωm can be improved to around 0.6% and 2%, respectively, if the statistical errors become negligible in the future.