|
|
Type of Document Dissertation Author Gallagher, Joseph Stever Author's Email Address jgallag3@nd.edu URN etd-12132007-104459 Title The Impact of Host Galaxy Environment on the Photometric Properties of Type Ia Supernovae Degree Doctor of Philosophy Department Physics Advisory Committee
Advisor Name Title Mario Borelli Committee Chair Anthony Hyder Committee Member Grant Mathews Committee Member Peter M. Garnavich Committee Member Terrence Rettig Committee Member Keywords
- Cosmology
- Supernovae
- Galaxies
Date of Defense 2007-11-30 Availability unrestricted Abstract For more than a decade observations and analyses of type Ia supernova (SNe Ia) explosions haveresulted in profound insights into the nature of our universe. However, in spite of the
amazing discoveries, the list of fundamental things that we still do not understand about
SNe Ia is quite long. We attempt to address a few of these questions through an analysis
of the galaxies in which they are hosted. We study the effect of environment on the
properties of SNe Ia by analyzing the integrated spectra of a sample of local SN Ia host
galaxies. We deduce from the spectra the metallicity, current star formation rate, and star
formation history of the host and compare these to the supernova decline rates, an indicator
of their peak magnitude. Our results indicate a statistically insignificant correlation in the
direction that higher metallicity spiral galaxies host fainter type Ia supernovae. However, we
present qualitative evidence suggesting progenitor age is more likely to be the source of
variability in supernova peak luminosities than is metallicity. Additionally, we compare the
host properties to the difference between the derived supernova distance and the distance
determined from the best-fit Hubble law. From this we investigate possible uncorrected
systematic effects inherent in the calibration of type Ia supernova luminosities using light
curve fitting techniques. A tenuous correlation is observed between the supernova Hubble
residuals and host galaxy metallicities. However, further host galaxy observations will be needed to
refine the significance of this result. Furthermore, we characterize the environmental property
distributions for type Ia supernova host galaxies through a comparison with two larger,
more general distributions of field galaxies using Kolmogorov-Smirnov tests. Distribution
discrepancies are presented and used to place a lower limit of ~ 2.0 Gyrs on the SN Ia
characteristic delay time. In addition, we present a host galaxy study focused solely on the
environmental properties of early type host galaxies. Our narrow focus allows for the
simultaneous measurement of both global age and metallicity, further allowing for a direct
identification of possible dependences between both SN peak magnitude and Hubble Residual
on host galaxy age and metallicity. We find evidence for either or both age and metallicity
effecting the peak V-band magnitudes of SNe Ia, and we discuss the difficulty in differentiating
between a real correlation and one arising from the degeneracy of age and metallicity. We
also find an ~ 2 sigma detection of a trend between early type host galaxy metallicity
and Hubble Residual. Moreover, we compare the early type host galaxy age and metallicity
distributions to corresponding distributions of elliptical galaxies from SDSS via KS-tests
and make predictions on the relative SN Ia rate based on a detailed comparison between the
age distributions of the Ia hosts and SDSS galaxies. Finally, we present an analysis of the
star formation rate distribution of high-z ESSENCE SN Ia host galaxies through a global
comparison to the low-z sample of host galaxies and a sample of high-z field galaxies.
Files
Filename Size Approximate Download Time (Hours:Minutes:Seconds)
28.8 Modem 56K Modem ISDN (64 Kb) ISDN (128 Kb) Higher-speed Access GallagherJ122007.pdf 3.27 Mb 00:15:09 00:07:47 00:06:49 00:03:24 00:00:17