Comparison of Normal and Ultra-Diffuse Gas Rich Galaxies

Faculty Sponsor

Luke Leisman


Arts and Sciences



Presentation Type

Poster Presentation

Symposium Date

Spring 5-3-2018


The goal of this project is to better understand star formation in a strange new class of galaxies called ultra-diffuse galaxies (UDGs), which are galaxies with very low stellar densities (i.e. only a few stars per unit area) compared to typical galaxies. I have specifically aimed to determine if UDGs that have the fuel to form stars (i.e. HI) have different properties from “normal” galaxies that also have the fuel to form stars. By doing this, I uncover differences that explain why their stars are so diffuse, and eliminate hypotheses that predict observable differences. The steps of this project each involve a comparison between galaxies in one galactic characteristic. I compare the color of galaxies, followed by the presence of a neighbor galaxy and whether or not the presence of neighbor galaxies affects color. Finally, the rotation of UDGs is compared to normal galaxies. The results from each of these parts better constrain the properties of UDGs containing atomic hydrogen - the fuel for star formation. Radio wavelength observations, which give us information about the atomic hydrogen, will primarily be taken from the ALFALFA survey, which has taken electromagnetic spectra of tens of thousands of individual galaxies with the Arecibo Observatory. Visible light images and data was obtained from the publicly available Sloan Digital Sky Survey. The approximate sample sizes for this project is between 70 and 250 ultra-diffuse galaxies (depending on how low in stellar density we will define a diffuse galaxy to be) compared to 10,000 other non-ultra-diffuse “normal” galaxies (the 10,000 least diffuse we can find).

Biographical Information about Author(s)

I am Andrew Webb and am from Asheville, North Carolina. I have always been interested in astronomy and space. Since high school, I was a part of an astronomy club and made trips to tops of mountains to look at stars. I will be graduating this May with a Bachelor's degree in Physics, and plan to pursue a career in environmental science and sustainability.

This document is currently not available here.