# Fitting and Phenomenology in Type Ia Supernova Cosmology: Generalized Likelihood Analyses for Multiple Evolving Populations and Observations of Near-Infrared Lightcurves including Host Galaxy Properties

Ponder, Kara A. (2017) Fitting and Phenomenology in Type Ia Supernova Cosmology: Generalized Likelihood Analyses for Multiple Evolving Populations and Observations of Near-Infrared Lightcurves including Host Galaxy Properties. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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## Abstract

In the late 1990s, Type Ia supernovae (SNeIa) led to the discovery that the Universe is expanding at an accelerating rate due to dark energy.
Since then, many different tracers of acceleration have been used to characterize dark energy, but the source of cosmic acceleration has remained a mystery.
To better understand dark energy, future surveys such as the ground-based Large Synoptic Survey Telescope and the space-based Wide-Field Infrared Survey Telescope will collect thousands of SNeIa to use as a primary dark energy probe.
These large surveys will be systematics limited, which makes it imperative for our insight regarding systematics to dramatically increase over the next decade for SNeIa to continue to contribute to precision cosmology.
I approach this problem by improving statistical methods in the likelihood analysis and collecting near infrared (NIR) SNeIa with their host galaxies to improve the nearby data set and search for additional systematics.

Using more statistically robust methods to account for systematics within the likelihood function can increase accuracy in cosmological parameters with a minimal precision loss.
Though a sample of at least 10,000 SNeIa is necessary to confirm multiple populations of SNeIa, the bias in cosmology is $\sim2~\sigma$ with only 2,500 SNeIa.
This work focused on an example systematic (host galaxy correlations), but it can be generalized for any systematic that can be represented by a distribution of multiple Gaussians.

The SweetSpot survey gathered 114 low-redshift, NIR SNeIa that will act as a crucial anchor sample for the future high redshift surveys.
NIR observations are not as affected by dust contamination, which may lead to increased understanding of systematics seen in optical wavelengths.
We obtained spatially resolved spectra for 32 SweetSpot host galaxies to test for local host galaxy correlations.
For the first time, we probe global host galaxy correlations with NIR brightnesses from the current literature sample of SNeIa with host galaxy data from publicly available catalogs.
We find inconclusive evidence that more massive galaxies host SNeIa that are brighter in the NIR than SNeIa hosted in less massive galaxies.

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## Details

Item Type: University of Pittsburgh ETD
Status: Unpublished
Creators/Authors:
Ponder, Kara A.kap146@pitt.edukap1460000-0002-8207-3304
ETD Committee:
Committee ChairWood-Vasey, W. Michaelwmwv@pitt.eduwmwv
Committee CoChairZentner, Andrewzentner@pitt.eduzentner
Committee MemberJeffrey, Newmanjanewman@pitt.edujanewman
Committee MemberFreitas, Ayresafreitas@pitt.eduafreitas
Committee MemberMandelbaum, Rachelrmandelb@andrew.cmu.edu
Date: 28 September 2017
Date Type: Publication
Defense Date: 19 July 2017
Approval Date: 28 September 2017
Submission Date: 27 June 2017
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 253
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Physics
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Supernovae, Cosmology, Statistical Methods
Date Deposited: 28 Sep 2017 23:02