Sumit Sarbadhicary

Title: Using populations of supernova remnants in Local Group galaxies as SN surveys.

Abstract:             

Supernova remnants (SNRs) in Local Group galaxies offer unique insights into the origin of different types of supernovae. In order to take full advantage of these insights, one must understand the intrinsic and environmental diversity of SNRs in the context of their host galaxies. We introduce a semi-analytic model that reproduces the statistical properties of an SNR population, taking into account the detection limits of radio surveys, the range of SN kinetic energies, the measured ISM and stellar mass distribution in the galaxy from multi-wavelength images and the current understanding of electron acceleration and field amplification in SNR shocks from first-principle kinetic simulations. Applying our model to the SNR population in M33, we reproduce their radio luminosity function with a SN rate of  3.2 x 10^-3 SN per year and an electron acceleration efficiency ~ 4 x 10^-3. Within these constraints, we predict that the radio visibility of 70% of M33 SNRs will be decided by their Sedov-Taylor lifetimes, and correlated with the measured ISM column density, while the remaining 30% will have visibility times decided by the detection limit of the radio survey. Our observational constraints on the visibility time of SNRs will allow us to use SNR catalogs as ’SN surveys’ to calculate SN rates and delay time distributions in the Local Group.

Antonio Villarreal

Title: Halo Definition and Environmental Effects
Abstract:
In recent years it has becoming increasingly clear that the properties of dark matter halos are tied to the environments they live in. This development provides a challenge for standard halo model implementations. We look to see if we can remove this dependence on environment through a straightforward change of how a dark matter halo is defined. We test for the removal of environmental effects using clustering statistics after redefinition of the dark matter halos. We find that environmental effects can be potentially removed through this method for certain mass ranges and properties at large scales. This method of halo definition should allow application of halo models within certain limits in the future, while also giving us insight as to the limits of these standard implementations for future work