Cosmology Seminar: Matthieu Roman

Matthieu Roman is a Postdoctoral fellow in LPNHE, Paris

Local environment of SNLS5 supernovae

Type Ia supernovae (SNe Ia) have proved to be a successful probe of dark energy thanks to their property of standardizable candle allowing us to construct a supernova Hubble diagram. All supernovae-based cosmological analyses rely on a standardization procedure that account for two measured parameters corresponding to the color and the decline rate of the event light-curve. This two-parameter empirical standardization does not entirely capture the physical processes at play. Indeed, there remains about 0.1 magnitude intrinsic luminosity variation after corrections are applied, leaving plenty of room for a third variable correlating to Hubble diagram residuals. In fact, progenitor physics triggering the supernova explosion is still poorly understood, but one can expect that global or local supernova environment plays a role in the event luminosity. If not treated properly, and with increasing statistics, the evolution of the average environment with redshift could bias cosmological parameters estimation. Numerous independent studies have shown that host galaxy stellar masses significantly correlate with light-curve standardization parameters and it has been established that Hubble diagram residuals correlate to global properties of the host galaxy. I present a consistent set of measurements of the properties of the global and local environments of type Ia SNe in the largest spectroscopic sample to date. Our sample includes the full Supernova Legacy Survey data (SNLS) as well as the SDSS data and a number of well-measured low-redshift supernovae. While the analysis is still blinded regarding the cosmology, preliminary results can be obtained which cast a new light on the environmental dependence of supernova luminosity.

Organizer

Benjamin Racine
Published Dec. 8, 2015 3:20 PM - Last modified Dec. 11, 2015 2:47 PM