Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)

Graduate Group

Physics & Astronomy

First Advisor

Masao Sako


For 70 years, the physics community operated under the assumption that the expansion of

the Universe must be slowing due to gravitational attraction. Then, in 1998, two teams of

scientists used Type Ia supernovae to discover that cosmic expansion was actually acceler-

ating due to a mysterious “dark energy.” As a result, Type Ia supernovae have become the

most cosmologically important transient events in the last 20 years, with a large amount

of effort going into their discovery as well as understanding their progenitor systems.

One such probe for understanding Type Ia supernovae is to use rate measurements to de-

termine the time delay between star formation and supernova explosion. For the last 30

years, the discovery of individual Type Ia supernova events has been accelerating. How-

ever, those discoveries were happening in time-domain surveys that probed only a portion

of the redshift range where expansion was impacted by dark energy. The Dark Energy

Survey (DES) is the first project in the “next generation” of time-domain surveys that will

discovery thousands of Type Ia supernovae out to a redshift of 1.2 (where dark energy be-

comes subdominant) and DES will have better systematic uncertainties over that redshift

range than any survey to date. In order to gauge the discovery effectiveness of this survey,

we will use the first season’s 469 photometrically typed supernovee and compare it with

simulations in order to update the full survey Type Ia projections from 3500 to 2250. We

will then use 165 of the 469 supernovae out to a redshift of 0.6 to measure the supernovae

rate both as a function of comoving volume and of the star formation rate as it evolves with redshift. We find the most statistically significant prompt fraction of any survey to

date (with a 3.9σ prompt fraction detection). We will also reinforce the already existing

tension in the measurement of the delayed fraction between high (z > 1.2) and low red-

shift rate measurements, where we find no significant evidence of a delayed fraction at all

in our photometric sample.

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