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Author ORCID Identifier

N/A

AccessType

Open Access Dissertation

Document Type

dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Astronomy

Year Degree Awarded

2017

Month Degree Awarded

September

First Advisor

D. Calzetti

Second Advisor

A. Pocar

Third Advisor

A. Pope

Fourth Advisor

M. Yun

Subject Categories

External Galaxies

Abstract

Star formation rates (SFRs) are among the fundamental properties used to characterize galaxies during their evolution across cosmic times. In the first part of this dissertation, we calibrate continuous, monochromatic SFR indicators over the mid-infrared wavelength range of 6-70 micron. We use a sample of 58 local star-forming galaxies for which there is a rich suite of multi-wavelength photometry and spectroscopy from the ultraviolet through far-infrared. Our results indicate that our mid-infrared SFR indicators are applicable to galaxies over a large range of distances, proving their robustness. We have made the calibrations and diagnostics publicly available to achieve the broadest possible user base. Our tests have shown that these calibrations will be key for unraveling galaxy evolution in the era of the James Webb Space Telescope. As a second part of the dissertation, we characterize the effects of dust in star-forming galaxies, with the goal of providing tools to remove dust effects from galaxies and therefore enable robust derivation of SFRs and other physical parameters. Towards this goal, we utilize a sample of ~10,000 local star-forming galaxies and obtain an estimate of their average attenuation. We compare our results with others in the literature, specifically the attenuation curve derived in the past for strongly star-forming galaxies (called ``starburst" galaxies). Our average attenuation curve is slightly lower in the far-ultraviolet than starburst galaxies, by ~15%, but appears similar at longer wavelengths. We also derive the attenuation curve for subpopulations of our sample, separated according to various physical properties. We find over the range of properties spanned, only inclination has noticeable influence on the shape of the average attenuation curve. The attenuation curves are found to be slightly shallower at UV wavelengths with increasing galaxy inclination, and the most edge-on cases show evidence for a weakened 2175-Angstrom feature with a bump strength of 17-26% that of the Milky Way. Given the relatively small differences among subpopulations, we conclude that a single curve is reasonable for applications seeking to broadly characterize large samples of galaxies in the local Universe. However, applications to individual galaxies would yield large uncertainties and is not recommended.

DOI

https://doi.org/10.7275/10659070.0

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