My thesis work was in Professor Elena D'Onghia's group, where I studied gravitational interactions between dwarf galaxies. Much of professor D'Onghia's work focuses on dynamics of disks like our Milky Way. One of the issues is how spiral arms form, and you can play with an interactive version of her results here.

You can also check out our group's Github page to see publicly available code.

My thesis work focused on interactions between small galaxies. I use computation models to understand how these small systems grow, interact, and ultimately build larger systems like the Milky Way. In particular, I focus on Magellanic spirals - galaxies that, like the Large Magellanic Cloud, have misplaced bars, single spiral arms, or irregular features. I have written papers on how these galaxies interact, how they can contribute gas to our own galaxy in the form of cold gas streams, and how the satellite population may be different around them.


Google Scholar -- ADS

Pardy, S. A.; D'Onghia, E.; Fox, A. ApJ accepted-- Models of Tidally Induced Gas Filaments in the Magellanic Stream

Bustard, C.; Pardy, S. A.; D'Onghia, E.; Zweibel, E. G.; Gallagher, J. S. III. ApJ submitted-- The Fate of Supernova-Heated Gas in Star-Forming Regions of the LMC: Lessons for Galaxy Formation?

Bridge, J. S.; Hayes, M.; Melinder, J.; Östlin, G.; Gronwall, C.; Ciardullo, R.; Atek, H.; Cannon, J. M.; Gronke, M.; Guaita, L.; Hagen, A.; Herenz, E. C.; Kunth, D.; Laursen, P.; Mas-Hesse, J. M.; Pardy, S. A.; ApJ accepted -- The Lyman Alpha Reference Sample. VIII. Characterizing Lyman-Alpha Scattering in Nearby Galaxies

Chen, B.; D'Onghia, E.; Pardy, S.; Pasquali, A.; Motta, C. B.; Hanlon, B.; Grebel, E. K. ApJ submitted -- Chemo-Dynamical Clustering applied to APOGEE data: Re-Discovering Globular Clusters

Pardy, S. A.; Cannon, J.M.; Östlin, G.; Hayes, M.; Bergvall, N. AJ, 152, 178 -- Detection of HI in Emission in the Lyman Alpha Emitting Galaxy Haro 11

Pardy, S. A.; D'onghia, E.; Athanassoula, E.; Wilcots, E. M.; Sheth, K., 2016 ApJ, 827, 149 -- Tidally-Induced Offset Disks in Magellanic Spiral Galaxies

Herenz, E.C.; Gruyters, P.; Orlitova, I.; Hayes, M.; Östlin, G.; Cannon, J. M.; Roth, M. M.; Bik, A.; Pardy, S.; Otí-Floranes, H.; Mas-Hesse, J. M.; Adamo A., Atek, H.; Duval, F.; Guaita, L.; Kunth, D.; Laursen, P.; Melinder, J.; Puschnig, J.; Rivera-Thorsen, T. E.; Schaerer, D.; Verhamme, A., 2016 A&A, 587A, 78 -- The Lyman alpha reference sample. VII. Spatially resolved Hα kinematics

de Swardt, B.; Sheth, K; Kim, T.; Pardy, S., D'Onghia, E.; Wilcots, E.; Hinz, J; Munõz-Mateos, J.-C.; Regan, M. W.; Athanassoula, E.; Bosma, A.; Buta, R. J.; Comerón, S.; Gadotti, D. A.; de Paz, A. G.; Jarrett, T. H.; Elmegreen, D. M.; Elmegreen, B. G.; Knapen, J. H.; Laine, J.; Laurikainen, E.; Ho, L. C.; Madore, B. F.; Meidt, S.; Menéndez-Delmestre, K.; Peng, C. Y.; Salo, H.; Schinnerer, E.; Zaritsky, D., 2015 ApJ, 808, 90 -- The Off-center Bar in the Late-type Galaxy NGC 3906

Guaita, L.; Melinder, J.; Hayes, M.; Östlin, G.; Gonzalez, J. E.; Micheva, G.; Adamo, A.; Mas-Hesse, J. M.; Sandberg, A.; Otí-Floranes, H.; Schaerer, D.; Verhamme, A.; Freeland, E.; Orlitová, I.; Laursen, P.; Cannon, J. M.; Duval, F.; Rivera-Thorsen, T.; Herenz, E. C.; Kunth, D.; Atek, H.; Puschnig, J.; Gruyters, P.; Pardy, S. A., A&A, 576, A51 -- The Lyman alpha reference sample: IV. Morphology at low and high redshift

Östlin, G.; Hayes, M.; Duval, F.; Sandberg, A.; Rivera-Thorsen, T.; Marquart, T.; Orlitova, I.; Adamo, A.; Melinder, J.; Guaita, L,; Atek, H.; Cannon, J. M.; Gruyters, P.; Herenz, E. C.; Kunth, D.; Laursen, P.; Mas-Hesse, J. M.; Micheva, G.; Pardy, S. A.; Oti-Floranes, H. ; Roth, M. M.; Schaerer, D.; Verhamme, A. 2014 ApJ, 797, 11 -- The Lyman-alpha Reference Sample: I. Survey outline and first results for Markarian 259

Pardy, S. A.; Cannon, J. M.; Östlin, G.; Hayes, M.; Rivera-Thorsen, T.; Sandberg, A.; Adamo, A.; Freeland, E.; Christian Herenz; E., Guaita, L.; Kunth, D.; Laursen, P.; Mas-Hesse, J. M.; Melinder, J.; Orlitova, I.; Oti-Floranes, H.; Puschnig, J.; Schaerer, D.; Verhamme, A., 2014 ApJ, 794, 101 -- The Lyman Alpha Reference Sample: III. Properties of the Neutral ISM from GBT and VLA Observations

Bernstein-Cooper, E. Z., Cannon, J. M., Elson, E. C.,Warren, S.R., Chengalur, J., Skillman, E.D., Adams, E. A. K., Bolatto, A.B., Giovanelli, R., Haynes, M. P., McQuinn, K.B.W., Pardy, S.A, Rhode, K. L., Salzer, J.J., 2014, AJ, 148, 35 -- ALFALFA Discovery of the Nearby Gas-rich Dwarf Galaxy Leo P. V. Neutral Gas Dynamics and Kinematics

Hayes, M.; Östlin, G.; Duval, F.; Sandberg, A; Guaita, L; Melinder, J; Adamo, A; Schaerer, D; Verhamme, A; Orlitov‡, I; Mas-Hesse, J. M; Cannon, J. M.; Atek, H.; Kunth, D.; Laursen, P.; Ot’-Floranes, H.; Pardy, S.; Rivera-Thorsen, T.; Herenz, E. C.; 2014, ApJ, 782, 6 -- The Lyman alpha Reference Sample: II. HST imaging results, integrated properties and trends

Cannon, J. M.; Bernstein-Cooper, E. Z.; Cave, I. M.; Harris, J. B.; Marshall, M. V.; Moen, J. M.; Moody, S. J.; O'Leary, E. M.; Pardy, S. A.; Thomann, C. M.; 2012, AJ, 144, 82 -- The Neutral Gas Dynamics of the Nearby Magellanic Irregular Galaxy UGCA 105


Multiple Filaments in the Magellanic Stream

Some of my current work focuses on the interaction between the Large and Small Magellanic Clouds. My simulations explore how this interaction formed the complex and extensive stream of HI gas seen around the Clouds.

Paper: arxiv/1802.01600


The present day distribution of gas in the Magellanic Stream from one of our simulations and in the HI gas of Nidever et al. 2010.

Explore the data here.

Asymmetries in Magellanic Galaxies

As part of my thesis project, I examined the role of interactions in causing the asymmetries in Magellanic Galaxies. We discovered that tidally induced asymmetric-disks can masquerade as offset bars in Magellanic Galaxies.

We use a custom version of the GalIC code to simulate isolated galaxies and evolve encounters with Gadget 3.

Paper: arxiv/1602.07689


A simulation of a recently disrupted galaxy modeled after the LMC. The colors represent surface density of stars.

Explore the data here.

Chemical Tagging

Understanding where stars are born is a fundamental problem for astrophysics. This project used detailed chemical data from the APOGEE survey of more than 100,000 stars in the Milky Way to determine if there were statistically significant groups of stars that may have been born together.

Paper: arxiv/1709.03987


Stars from known globular clusters in chemical space.

Explore the data here.

Tidal Streams as a Probe of Dark Matter

As a 2014 fellow at the International Summer Institute for Modeling in Astrophysics, I worked with Andreas Küpper on modeling the tidal stream of NGC 5466. Tidal streams act as unique probes of the dark matter halo of their environments. This work, along with new data from Jay Strader, will place strong contraints on the shape and total mass of the Milky Way. We use a Markov chain Monte Carlo to probe parameter space, where the likelihood function is drawn in real time from very efficient restricted N-Body simulations of the globular cluster in our test potential.


A model of the Milky Way with our best fit stream model for NGC 5466 in red.


The Lyman Alpha Reference Sample (LARS) is a large Hubble project and international collaboration testing the escape of Lyman Alpha photons from distant galaxies.

LARS utilizes almost the entire electromagnetic spectrum: from UV and optical spectra that reveal intense star formation, to radio observations that probe the neutral hydrogen and molecular gas content. The survey started with 14 galaxies and 28 more have now been added through e(xtended)LARS. We have conducted HI observations using the GBT, VLA, and GMRT of all 14 LARS galaxies and many of the 28 eLARS.

In 2014, we released the results for the first 14 galaxies. A few years later we added to this by carrying out similar measurements on a strange galaxy (Haro 11) that emits lots of Lyman Alpha and Lyman Continuum emission.

Papers: arxiv/1408.6275 and arxiv/1609.04020


HI contours on DSS image of interacting galaxies LARS 03 (Arp 238).