# Star Formation in Interacting Dwarf Galaxies

Liss, Sandra, Astronomy - Graduate School of Arts and Sciences, University of Virginia
Johnson, Kelsey, As-Astronomy, University of Virginia
Abstract:

Merging galaxies in the nearby universe can provide an ideal local analog of the early universe. Though mergers are less common today, they were prevalent at higher redshift where the increased number density of galaxies led to frequent and prolonged galaxy interactions. However, although the majority of mergers at all redshifts are expected to occur between low mass galaxies, such interactions are poorly understood and largely overlooked in comparison to interactions between massive galaxies. The TiNy Titans (TNT) survey, designed to address this gap in knowledge, is a combined multi-wavelength observational and theoretical campaign aimed at investigating the role that dwarf galaxy interactions play in the larger picture of galaxy evolution.

Stars are one of the fundamental components that make up all galaxies, and their formation is ubiquitous throughout cosmic time. Consequently, some of the most pressing open questions related to dwarf-dwarf interactions concern how stars form in these systems. Understanding how these stars form, especially in the early universe, is a necessary foundation for topics ranging from planet formation to galaxy evolution. In this thesis, we examine the ongoing star formation in the TNT interacting dwarf galaxies in unprecedented detail.

In Chapter 2, we present the ultraviolet through mid-infrared spectral energy distributions (SEDs) of the TNT sample. In addition to allowing us to compare multiwavelength tracers of SFRs, these SEDs are used to quantify the `typical' SED of interacting dwarf-dwarf interactions. We present trends in the SEDs as a function of pair properties, galaxy properties, and tidal index. We then compare the interacting dwarf SEDs to other star-forming galaxies in order to contextualize their role in galaxy formation and evolution.

In Chapter 3, we discuss the total amount, distribution, and packaging (diffuse vs. clumped) of star forming regions within the TNT interacting dwarfs based on narrowband H$\alpha$ imaging from the Gemini North Telescope. We present a quantitative analysis of the star formation morphology and discuss the impact of galaxy properties and environment on the magnitude and clustering of star formation in these low mass dwarf galaxies.

In Chapter 4, we examine an important subset of the TNT interacting dwarf sample -- groups of three or more low mass interacting galaxies isolated from massive galaxies. We have identified the first such candidate groups that are both (1) compact in physical and velocity space, and (2) isolated from massive galaxies. We find that the evolution of these low mass groups is markedly different from that of compact groups of massive galaxies. We present these data as well as a discussion of the cosmological context and role of the groups in high redshift galaxy formation.

Degree:
PHD (Doctor of Philosophy)
Keywords:
dwarf galaxies, star formation, galaxy interactions, observational astronomy