Andrew J. Fox

ESA/AURA Astronomer
Space Telescope Science Institute

Milky Way Halo Research Group


Andrew Fox is an ESA/AURA astronomer at the Space Telescope Science Institute (STScI) in Baltimore, Maryland, where he serves as the Branch Deputy for the Instrument and Science Support Branch (ISSB) and the chair of the Telescope Time Review Board (TTRB). STScI is the scientific home of the Hubble Space Telescope and the James Webb Space Telescope. Andrew leads the Milky Way Halo Research Group, which focuses on understanding our own galaxy by using multi-wavelength spectroscopy to measure the flows of baryons between the Galactic disk and halo. Before joining STScI, he worked at the Institute of Astronomy (IoA) in Cambridge, the European Southern Observatory (ESO) in Chile, and the Institut d'Astrophysique de Paris (IAP), and he was a student at the University of Wisconsin-Madison and University College London (UCL). More information can be found on his STScI Directory Entry .

Click here for my ADS record

Click for my Resume (pdf) and Publications (pdf)

Recent work

Gas Accretion book

In 2017 Romeel Dave and I edited a book on Gas Accretion onto Galaxies, published by Springer. This is a contributed volume with 15 chapters written by 15 authors reviewing the inflow of gas onto galaxies. Find the chapters here.

Galactic Center Outflow

I'm the Principal Investigator of two HST program totaling 70 orbits to study the Galactic Center region in UV absorption. Our results dicussing the absorption-line properties of the biconical outflow at the center of the Milky Way are described in a series of papers in the Astrophysical Journal.

Magellanic Stream

The Magellanic Stream is a giant tidal tail of gas stipped out the Magellanic Clouds and now orbiting the Milky Way. See the Annual Reviews of Astronomy & Astrophysics article I wrote with Elena D'Onghia on this extraordinary stream or the press releases described below.

Press Releases

Fermi Bubbles

The Galactic nuclear wind is feeding the giant Fermi Bubbles with new material. Our Galactic Center program has led to two NASA press releases, one in 2015 on the discovery of the wind in UV absorption and one in 2017on the northern sky survey.

Magellanic Stream

This enormous tail of gas trailing the Magellanic Clouds holds clues to the formation of the Milky Way Galaxy and the Magellanic Clouds. We explore its origin using chemical composition analyses with Hubble and the Green Bank Telescope. See our 2013 NASA Press Release.

Smith Cloud

The enigmatic Smith Cloud is a massive infalling gas cloud close to impacting the Galactic disk. Its origin is unknown. We used Hubble to measure its chemical compostion and probe its source. See our 2016 NASA press release.

Seyfert Flare

The titanic explosion that created the Fermi Bubbles also produced an ionization cone that appears to have heated the Magellanic Stream, causing elevated H-alpha emission and UV ionization ratios. This story was announced by the ASTRO-3D center in Sydney and featured on BBC News.

Galactic Inflow & Outflow

Using observations from the Cosmic Origins Spectrograph (COS) on Hubble we measured the rates at which the Milky Way is gaining and losing mass, finding an excess of inflow. This story was covered by NASA, and Universe Today.

Leading Arm

The Leading Arm is a series of gas clouds connecting the Magellanic Clouds to the Milky Way. We measured its chemical composition and found it is spatially variable, providing new clues on its origin. These results were featured in a 2018 NASA press release.

Research Interests

Interstellar, circumgalactic, and intergalactic gas
High-velocity clouds (HVCs) and the Magellanic System
Quasar absorption line systems
Fermi Bubbles, galaxy inflows and outflows
Photoionization modeling of diffuse plasmas
Galaxy formation and evolution

Group Members


Trisha Ashley (postdoc)
David French (postdoc)
Elaine Frazer (staff scientist)
Camellia Magness (analyst)


Rongmon Bordoloi (now faculty at NC State)
Svea Hernandez (now postdoc at STScI)
Stephen Lucas (UCL)
Corbin Taylor (now at UMD)
Nimisha Kumari (now at IoA, Cambridge)
Jacqueline Antwi-Danso (now at Texas A&M)
Tanveer Karim (now at Harvard)

More information is on our group webpage.


Space Telescope Science Institute
3700 San Martin Drive, Baltimore, MD 21218
Office: +1 410 338 5083
Email: afox[at]