Swift/UVOT Observations of Star Formation and Dust Attenuation in both Local and High Redshift Galaxies

Open Access
Author:
Hagen, Lea May
Graduate Program:
Astronomy and Astrophysics
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
June 28, 2017
Committee Members:
  • Caryl Ann Gronwall, Dissertation Advisor
  • Caryl Ann Gronwall, Committee Chair
  • Michael Hiram Siegel, Committee Member
  • Robin Bruce Ciardullo, Committee Member
  • Sarah Elizabeth Shandera, Outside Member
  • John Andrew Nousek, Committee Member
Keywords:
  • star formation
  • dust
  • Swift
  • ultraviolet
  • UVOT
  • galaxies
  • astronomy
  • Small Magellanic Cloud
  • M33
  • M31
Abstract:
The Swift Ultraviolet/Optical Telescope (UVOT) is uniquely suited to study star formation and dust extinction in both nearby and distant galaxies. I present results from the Small Magellanic Cloud, M33, and M31, for which I have unprecedented observations in three near-UV bands from 1700A to 3000A at 2.5" resolution. I combine the UV imaging with archival optical and infrared data to model the spectral energy distributions (SEDs) of individual regions of each galaxy, simultaneously fitting for the wavelength dependence of dust attenuation, total dust, stellar mass, and age. I have created the first-ever maps of the UV dust extinction curve, which show previously-unconfirmed spatial variation: both the slope and 2175A bump vary considerably over the face of the three galaxies. I use these maps to probe the the origin of the extinction curve variation and find correlations with physical properties -- including specific star formation rate (SFR), temperature, and presence of polycyclic aromatic hydrocarbons -- in some, but not all, of the galaxies. I then use UVOT observations of higher redshift galaxies (0.2 < z < 1.2) to derive the evolution of the SFR density. Since the SFR is calculated from the dust-corrected UV luminosities of each galaxy, the adopted dust extinction curve has a significant impact on the SFR density over time. I conclude by discussing an in-progress UVOT survey of over 400 galaxies in the local volume (D < 11 Mpc) and how modeling their SEDs will enable a more thorough understanding of UV dust attenuation.