Who We Are

Current Group Members

Trisha Ashley

Dr Trisha Ashley is a postdoctoral fellow at STScI. She is an expert on gas in early type galaxies and the enigmatic class of active galaxies known as blue compact dwarfs. Her latest project involves studying the giant Fermi Bubbles at the Galactic Center using ultraviolet absorption lines. She obtained her undergraduate degree at Bryn Mawr college, and her PhD at Florida International University, where she completed her thesis on atomic gas in the LITTLE THINGS sample of blue compact dwarf galaxies. She held a postdoctoral position through the Bay Area Environmetal Research Institute, followed by a NASA Postdoctoral Program (NPP) fellowship both held at NASA-Ames. She joined STScI in 2018. See her personal website for more information.

Francie Cashman

Dr Francie Cashman is a postdoctoral fellow at STScI. She is studying the interstellar medium near the Galactic Center using ultraviolet absorption line spectroscopy. Francie received her undergraduate degree in Physics from the College of Charleston and her PhD in Physics from the University of South Carolina. Her PhD thesis explored gravitationally lensed quasar absorption line systems, as well as provided a comprehensive survey of the atomic data commonly used in absorption line studies of the interstellar, circumgalactic, and intergalactic medium.

Andrew Fox

Dr Andy Fox is an ESA-AURA astronomer at STScI. He's interested in all aspects of gas in the Galactic halo, including its origin, fate, chemistry, physical properties, and role in galaxy evolution. More generally his research covers the interstellar, circumgalactic, and intergalactic media that together harbor most of the baryons in the Universe. He obtained his undergraduate degree at University College London in England and his PhD at the University of Wisconsin-Madison, where he completed a thesis on the origins of highly ionized gas in high-velocity clouds. He then held a Marie Curie postdoctoral fellowship at the Institut d'Astrophysique de Paris (IAP) in France, followed by an ESO Fellowship at the European Southern Observatory in Chile with a year spent at the Institute of Astronomy in Cambridge, England. For more information see his personal website and STScI directory entry.

David French

Dr David French is a postdoctoral fellow at STScI. He studies the intergalactic and circumgalactic medium and their connection to galaxies, galaxy rotation curves, and the Milky Way halo. He is currently using novel techniques to probe the diffuse hydrogen in the Galactic halo using Lyman series absorption lines in the far-ultraviolet with data from NASA's Far-Ultraviolet Spectroscopic Explorer (FUSE). He completed his undergraduate studies at Carleton College and then obtained his Masters and PhD from the University of Wisconsin-Madison. His PhD thesis work concerned the galaxy-intergalactic medium connection in the local Universe.

Jason Tumlinson

Dr Jason Tumlinson is a full Astronomer at STScI. He has worked as an observational and theoretical astronomer spanning multiple areas of astrophysics since beginning his PhD studies in 1998. As an observer he is the PI of the COS-Halos project, a 277-orbit program with Hubble's Cosmic Origins Spectrograph that has made several significant discoveries about the nature of the gaseous Circumgalactic Medium (CGM) that helps to form and feed galaxies. This program has generated a number of high-impact publications, including the most cited paper based on COS data (Tumlinson et al. 2011). As a theorist, he was among the first to publish realistic stellar evolution models and ionizing photon outputs for primordial stars. For more information see his personal website and STScI directory entry.

Former Group Members

Camellia Magness

Camellia Magness is a Research and Instrument Analyst working for the COS instrument team at STScI. She's passionate about studying the vast unknowns of the universe, but also working on calibration and tools to aid other researchers pursue better astronomy. She is currently working on developing a Python tool for measuring the apparent optical depth of absorption features as part of a greater project studying the Fermi Bubbles. She completed her Bachelor's degree at the University of Washington, where she worked with COS data from the COS-Halos survey studying the Intergalactic Medium and Circumgalactic Medium. She then held a research position at NASA's Goddard Space Flight Center working with Integral Field Unit data from the Multi Unit Spectroscopic Explorer (MUSE), looking at Active Galactic Nuclei to study galaxy kinematics, before joining the COS team at STScI in 2017.

Elaine Frazer

Elaine Frazer is a Research and Instrument Analyst working for the Cosmic Origins Spectrograph (COS)instrument team at STScI. She's working on a research project to explore the kinematics of the Magellanic Stream, and to look for spatial variation in the Stream's kinematic and phase structure. This project is looking for evidence that an energetic flare at the Galactic Center ionized the Stream. This involves using new Python tools to conduct Voigt profile fitting analyses to a large sample of COS spectra of sightlines passing through the Stream. She completed her bachelor's degree at Indiana University and her master's degree at the University of North Carolina at Chapel Hill, where she studied the formation and evolution of compact elliptical galaxies with the RESOLVE survey collaboration. Previous works can be found on her ORCID (https://orcid.org/0000-0001-9352-9023).


We work with many other collaborators including Blair Savage, Bart Wakker, and Elena d'Onghia in Wisconsin, Rongmon Bordoloi at North Carolina State, Philipp Richter in Potsdam, Chris Howk and Nicolas Lehner at Notre Dame, Kat Barger and Drew Ciampa at TCU, Molly Peeples at STScI, Tanveer Karim at Harvard, Jay Lockman at Green Bank, Joss Bland-Hawthorn in Sydney, and Ed Jenkins at Princeton, among others.

We are part of the Low Density Universe community at STScI and we have close research overlap with the COS-Halos, ISM@ST, and FOGGIE research groups.