Speaker:
Ryan Foley
Institution:
Harvard-Smithsonian Ctr., for Astro.
Date:
Thursday, March 15, 2012
Time:
4:00 pm
Location:
NS2 1201
ABSTRACT:
Type Ia supernovae (SNe Ia) are the best cosmological yard sticks available. Measurements of nearby and distant SNe Ia led to the discovery of the accelerating universe (and the 2011 Nobel prize in physics) and currently provide the best constraints on the nature of dark energy. SNe Ia are precise distance indicators because of a relationship between their peak brightness and light-curve width, making SNe Ia "standardizable candles." However, we have assumed that SNe Ia with a given light-curve width all have the same intrinsic color. Knowing the intrinsic color of a SN is necessary to determine how much the SN has been reddened by interstellar dust, and thus its true distance. We have recently discovered a new relationship between the intrinsic color of a SN and its ejecta velocity. This effect can be explained by additional line blanketing in the blue for the higher-velocity objects. Velocity information provides a way to correct the observed color, making SNe Ia "standardizable crayons." Measuring the ejecta velocity of SNe Ia both improves distance estimates for SNe Ia and reduces potential systematic biases. We discuss the implications of this result, including how using this information will improve our understanding of SN Ia physics, SN progenitors, and measurements of cosmological parameters.
Host:
James Bullock