Who We Are

Current Group Members

Andrew Fox (Group Leader)

Dr Andy Fox is an ESA-AURA astronomer at STScI. He's interested in all aspects of 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. He has been a member of the science staff at STScI since 2011. For more information see his personal website and STScI directory entry.

David French

Dr David French is a Senior Staff Scientist in the Cosmic Origins Spectrograph (COS) team 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 is also studying "beam smearing" effects that arise from combining UV absorption and radio emission spectra. These effects impact metallicity measurements in the Galactic halo. 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.

Avery Kim

Dr. Doyeon (Avery) Kim is a joint postdoctoral fellow in the ISM* and Milky Way Halo groups at STScI. Her research focuses on understanding the multi-phase, multi-scale interactions of gas and dust in and around galaxies, and how these processes shape a galaxy. Avery completed her undergraduate degrees in Physics and Astronomy at the University of California, Berkeley, and received her Ph.D. in Astronomy from Columbia University. Her PhD thesis explored multi-scale interactions in the gaseous media of galaxies using data-driven techniques. See her personal website for more information.

Sapna Mishra

Dr. Sapna Mishra is a postdoctoral fellow in the Milky Way Halo group at STScI. She is currently studying the cool gaseous halo of the Large Magellanic Cloud using UV absorption-line spectroscopy, and using the LMC halo as way to probe the Milky Way-LMC interaction. She also works on measuring the distance to the Magellanic Stream using optical spectroscopy of background stars at different distances. Sapna completed her Ph.D. at ARIES in India, where she studied the environment of active galaxies via radiative outflows and kinetic jets using photometry and spectroscopy. She then worked as a postdoc at IUCAA in Pune, India, where she focused on the characterization of the diffuse cool and warm gas in and around galaxy clusters using quasar absorption-line spectroscopy. She joined STScI in fall 2023. For more information see her personal website.

Ravi Sankrit

Dr. Ravi Sankrit is an STScI Scientist in the HST Cosmic Origins Spectrograph (COS) team. His research interests include the study of supernova remnants, superbubbles, and the diffuse interstellar medium. He completed his undergraduate studies at St. Stephen's College in Delhi, India, and obtained his PhD from Arizona State University. His doctoral thesis work involved shock and photoionization modeling to study the emission morphology and ionization structure seen in high angular resolution HST/WFPC2 images of the Crab Nebula (M1) and the Eagle Nebula (M16). He has since then been part of the FUSE team at the Johns Hopkins University, the SPEAR/FIMS team at the Space Sciences Laboratory (UC Berkeley) and at the SOFIA Science Center (NASA Ames) before moving to STScI. For details about his research see his ADS publication record.

Debopam Som

Dr Debopam Som is a Senior Staff Scientist at STScI. He studies the intergalactic and circumgalactic medium and their connection to galaxy evolution, and the Milky Way halo. He completed his undergraduate studies and a MSc (Physics) degree in India and obtained his PhD (Physics and Astronomy) from the University of South Carolina. His PhD thesis work concerned the study of the circumgalactic medium at high-redshift focusing on UV/optical spectroscopic study of sub-damped Lyman-alpha quasar absorption systems. He has held postdoctoral research positions at the Laboratoire d’Astrophysique de Marseille and the Ohio State University prior to joining STScI. In addition to space and ground based UVOIR spectroscopy and imaging, Dr. Som is experienced in MOS surveys through his work in building WEAVE and DESI surveys and is a member of the ULLYSES core implementation team.

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.

Alexander You

Zhibin (Alexander) You is an undergraduate at Johns Hopkins University. He’s interested in the origin, evolution, and properties of galaxies. He is currently studying the physical properties of neutral and low-ionization gas in the Milky Way halo by using Voigt profile fittings of CaII and NaI absorption lines in the spectra of background targets. He joined Milky Way Halo group in Spring 2025.

Former Group Members

Trisha Ashley

Dr Trisha Ashley was a postdoctoral fellow at STScI from 2018 to 2023. She is an expert on gas in early type galaxies, the enigmatic class of active galaxies known as blue compact dwarfs, and the giant Fermi Bubbles at the Galactic Center. 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.

Francie Cashman

Dr Francie Cashman is an assistant professor of physics at Presbyterian College in South Carolina. She is an expert in laboratory astrophysics, the interstellar medium, and 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. She was a postdoc at STScI before starting her faculty position.

Elaine Frazer

Elaine Frazer is a Senior Staff Scientist working for the Cosmic Origins Spectrograph (COS) instrument team at STScI. In the Milky Way Halo group she completed 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 looked 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).

Dhanesh Krishnarao (DK)

Dr Dhanesh Krishnarao (DK) is a faculty member at Colorado College. He is an expert on diffuse ionized gas in the Milky Way and nearby galaxies and seeks to bridge together a Galactic and extragalactic perspective to better understand the physics of diffuse gas in galaxies. DK received his undergraduate degree in both Physics and Mathematics from American University and his PhD in Astronomy from the University of Wisconsin-Madison. His PhD thesis saught to connect structures in galaxies with the physical processes that determined the local and global conditions around such structures. DK is the a member of the Wisconsin H-Alpha Mapper (WHAM) team and a member of the Interstellar Institute. More information can be found on his personal website, www.astronomy.dk.

Camellia Magness

Camellia Magness was formerly 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. In the Milky Way Halo group she developed a Python tool for measuring the apparent optical depth of absorption features as part of a larger 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.

Christian Soto

Christian Soto is a Program Coordinator (Science Operations Analyst) in the Operations Planning Branch at STScI. Prior to arriving at the institute in the Summer of 2020, Christian worked at the Kitt Peak National Observatory in Tucson, AZ as a Telescope Operator. Christian received his BS degree in Physics and Astronomy from the University of Florida and his MS degree in Computer Engineering from the University of Arizona. He is pursuing a MS in Space Systems Engineering from The Johns Hopkins University. His research experience includes work on binary stars, exo-planets, extragalactic evolution and AGN. With the Milky Way Halo Research Group, Christian will be working on the low-velocity absorption from hot gas in the Fermi Bubbles.

Collaborators

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.