I am an assistant research scientist at Johns Hopkins University working with Molly Peeples, Jason Tumlinson, and the rest of the fantastic FOGGIE team. I use cosmological simulations to study galaxies that are difficult to study with telescopes: the small, the dim, and the diffuse. I am a member of The N-Body Shop Collaboration, and many of the simulations that I use are run with N-body+SPH code Gasoline or its newer cousin, ChaNGa. However, I am also using the FOGGIE simulations, which are run with Enzo, to study stellar halos.

Dwarf Galaxies

Stream of gas from merging galaxies (lower right) strikes dwarf galaxy (center; virial radius indicated by white circle), reigniting star formation
Stream of gas from merging galaxies (lower right) strikes dwarf galaxy (center; virial radius indicated by white circle), causing neutral hydrogen (HI) to build up and eventually reigniting star formation. Click for larger version of gif.

I investigate dwarf galaxies that are initially quenched by reionization, but which resume star formation at least 2 Gyr later. In zoom-in simulations run with Gasoline, star formation is restarted in these galaxies when they are struck by a stream of gas, typically either thrown off during a nearby merger (as in the above gif) or simply hanging off of a neighboring galaxy. If the ram pressure exerted by the stream is within the right range, some of the gas in the halo of the dwarf is compressed onto its disk, forming neutral hydrogen (HI) and, eventually, stars. I am interested in how the gas within dwarf galaxies evolves and, in particular, the role that environment plays in shaping their gas accretion and star formation histories.

Ultra-Diffuse Galaxies

Two galaxies merge, producing a single galaxy that is disky and diffuse
Formation of a field ultra-diffuse galaxy in the Romulus25 cosmological simulation. An early merger causes star formation in the galaxy to relocate to its outskirts, reducing its central surface brightness and increasing its size. Click for a full version of the movie with gas.

Ultra-diffuse galaxies (UDGs) are galaxies that are both exceptionally large (reff > 1.5 kpc) and exceptionally low surface brightness (μ 0 > 24 mag/arcsec2). Although originally discovered in clusters, they have also been observed in the field, which suggests that it is not purely the violence of the cluster environment that creates them. However, it turns out that a galaxy that is isolated now didn't necessarily spend its entire life alone. The field UDGs that form within the Romulus25 cosmological simulation are primarily the products of relatively early major mergers that caused their star formation to move outward. I am interested in the properties and origins of these galaxies and other members of the low surface brightness galaxy family.

Stellar Halos

A Milky Way analog in the FOGGIE simulation suite. The orange-blue image shows gas density, which fades into a mock UVI image of the galaxy that highlights its stars and dust. The surface brightness limits drop until the full stellar halo is visible. Click here to see a video of the full formation of this galaxy.

While most of a galaxy's stars live in its disk, observations have revealed that our own Milky Way and many galaxies both like and unlike it are surrounded by a diffuse (and very low surface brightness!) halo of stars that can extend hundreds of kpc beyond the disk. The majority of the stars that make up stellar halos were actually formed in dwarf galaxies that fell into the gravitational potential of a more massive neighbor and were torn apart by tidal forces. However, dynamical times are long in the stellar halo, so the structures (e.g., streams, shells) that these galaxies form as they shed their stars persist for billions of years . This means that we can use stellar halos to learn about dwarf galaxies that were destroyed long ago. The upcoming Nancy Grace Roman Space Telescope, which is an infrared telescope with a field-of-view equivalent to roughly 100 Hubbles, will be a perfect instrument for studying stellar halos. I am using the FOGGIE simulations to figure out how we can optimize observations to learn about the ancient dwarfs that make up the stellar halos of our nearest massive neighbors.


(11) Figuring Out Gas & Galaxies in Enzo (FOGGIE) VII: The (Dis)Assembly of Stellar Halos
Wright, A.C., Tumlinson, J., Peeples, M.S., O'Shea, B.W., Lochhaas, C., Corlies, L., Smith, B.D., Binh, N., Augustin, R., & Simons, R.C., 2023, submitted to ApJ, arXiv:2309.10039

(10) Figuring Out Gas & Galaxies in Enzo (FOGGIE) VI: The Circumgalactic Medium of L* Galaxies is Supported in an Emergent, Non-Hydrostatic Equilibrium
Lochhaas, C., Tumlinson, J., Peeples, M.S., O'Shea, B.W., Werk, J.K., Simons, R.C., Juno, J., Kopenhafer, C.E., Augustin, R., Wright, A.C., Acharyya, A., & Smith, B.D., 2023, ApJ, 948(1):43, arXiv:2206.09925

(9) What's in a Name? Quantifying the Interplay between Definition, Orientation and Shape of UDGs using the Romulus Simulations
Van Nest, J.D., Munshi, F., Wright, A.C., Tremmel, M., Brooks, A.M., Nagai, D. & Quinn, T., 2021, ApJ, 926(1):92, arXiv:2108.12985

(8) Star Formation Histories from SEDs and CMDs Agree: Evidence for Synchronized Star Formation in Local Volume Dwarf Galaxies over the Past 3 Gyr
Olsen, C., Gawiser, E., Iyer, K., McQuinn, K.B.W., Johnson, B.D., Telford, G., Wright, A.C., Broussard, A., & Kurczynski, P., 2021, ApJ, 913(1):45, arXiv:2104.06514

(7) An Excess of Globular Clusters in UDGs Formed Through Tidal Heating
Carleton, T., Guo, Y., Munshi, F., Tremmel, M., & Wright, A., 2021, MNRAS, 502(1):398, arXiv:2008.11205

(6) The Formation of Isolated Ultra-Diffuse Galaxies in Romulus25
Wright, A.C., Tremmel, M., Brooks, A., Munshi, F., Nagai, D., Sharma, R.S., & Quinn, T.R., 2021, MNRAS, 502(4):5370, arXiv:2005.07634

(5) Black Hole Growth and Feedback in Isolated Romulus25 Dwarf Galaxies
Sharma, R.S., Brooks, A., Somerville, R.S., Tremmel, M., Bellovary, J., Wright, A.C., & Quinn, T.R., 2020, ApJ, 897(1):103, arXiv:1912.06646

(4) The Formation of Ultra-Diffuse Galaxies in the RomulusC Galaxy Cluster Simulation
Tremmel, M., Wright, A.C., Brooks, A.M., Munshi, F., Nagai, D., & Quinn, T.R., 2020, MNRAS, 497(3):2786, arXiv:1908.05684

(3) Reignition of Star Formation in Dwarf Galaxies
Wright, A.C., Brooks, A.M., Weisz, D.R., & Christensen, C.R., 2019, MNRAS, 482(1):1176, arXiv:1802.03019

(2) Simulating Radiative Magnetohydrodynamical Flows with AstroBEAR: Implementation and Applications of Non-equilibrium Cooling
Hansen, E., Hartigan, P., Frank, A., Wright, A., & Raymond, J., 2018, MNRAS, 481(3):3098, arXiv:1809.02207

(1) A New Diagnostic of Magnetic Field Strengths in Radiatively Cooled Shocks
Hartigan, P. & Wright, A., 2015, ApJ, 811(1):12, arXiv:1508:05409

See my papers on ADS

About Me

Demonstrating how smoke rings are made for a second grade class
Demonstrating how smoke rings are made for a class of second graders in Newark

I received my B.S. in Astrophysics from Rice University in 2014 and my Ph.D. in Physics & Astronomy from Rutgers University in 2020. While at Rutgers, I served on the Graduate Student Organization (GSO) and the Graduate Student Life Committee, helped to organize visits for prospective students, and participated in K-12 outreach. At Hopkins, I am active in the Women in Physics group and help to organize outreach events like Astro Scholars. In my spare time, I enjoy reading, baking, going for runs, and the occasional bit of recreational coding.

Feel free to send me an email at acwright*at*!