Neutron-Star Common-Envelope Evolution: The Interplay of Strong Gravity, Nuclear Microphysics, and Macroscopic Astrophysics

In order for double neutron stars (NSs) that form in isolation to merge within the age of the Universe, binaries need to survive two supernova explosions and one or more common-envelope phases. As a NS undergoes common-envelope evolution, it accretes from the surrounding stellar plasma and gravitational drag drives its orbital inspiral. Because NSs have extremely strong gravitational fields, they have a considerable amount of binding energy. I will discuss how the nuclear equation of state affects the NS binding energy and thus its accretion-fed growth during common-envelope inspiral. I will then discuss how these effects tie into the population properties of NS binaries and the cosmic double NS merger rate. 

By Miguel Holgado

Fundamental plane of BOSS galaxies.

Fundamental plane (FP) of elliptical galaxies, a relation between the size, luminosity and velocity dispersion of galaxies, has potential to be a predictor of intrinsic galaxy sizes, resulting in  important cosmological applications including measurements of galaxy distances, weak gravitational lensing and galaxy velocities. In this talk, I will present results from our recent work performing detailed tests on FP using data from SDSS BOSS galaxy survey. I will show that the FP is strongly correlated with galaxy properties, including luminosity, redshift and the local environment of galaxy, which can potentially bias the cosmological measurements. I will also show the comparison with the intrinsic alignment of galaxy shapes (IA) and the model which predicts that FP correlations with environment may be sourced by the combination of projection effects and IA, which can also bias the redshift space distortion measurements using these galaxies. We find no significant evidence in support of the model and of the impact of IA on the redshift space distortion measurements as tested using the FP.

By Sukhdeep Singh

Hosted by CMU.