APEC Seminar (Astronomy - Particle Physics - Experimental Physics - Cosmology)

Speaker: Petr Baklanov (ITEP Moscow)
Title: Type II-P supernovae as primary distance indicators in cosmology
Date (JST): Thu, Jan 14, 2016, 13:30 - 14:30
Place: Seminar Room A
Abstract: I will review briefly primary distance indicators for cosmology, and
in particular the Expanding Photosphere Method (EPM) for supernova
distance measurements. The EPM allows us to directly determine the
distance up to hundreds Megaparsecs and the EPM-distance does not
depend on any steps of the cosmological distance ladder.

The EPM suggests that the supernova photospheric flux can be expressed
via a simple formula involving an important correction factor. The
theoretical modelling of SN IIP by Eastman(1996) and Dessart(2005) has
revealed the correlation between the correction factor for EPM and the
color temperature of a supernova. The best-fit polynomials of the
correlation are in qualitative agreement in both papers, however, the
values of the correction factor are systematically larger for Dessart
approximation, than for Eastman approximation. That is why, the
EPM-distance difference can reach up to 50% for the same object!

I will discuss the dependence of the correction factor on the
parameters of supernovae. Using the self-consistent numerical
simulations with our radiation hydrodynamics code STELLA we have
obtained diagrams of dependence of the correction factor on the color
temperature from the initial phase of explosion up to the nebular
stage. Our approach to the numerical simulations differs radically
from Dessart methods, nevertheless, at the phase of free expansion our
best-fit polynomials are surprisingly close to the ones obtained from
Dessart modelling.

This result is an additional argument for a ``long'' scale of the
EPM-distances. It can be used for direct distance determination to SN
IIP using relatively simple measurements.