Sarah Pearson

Graduate Student, Columbia University

Welcome to my homepage! I am a fifth year graduate student in the
Department of Astronomy at Columbia University


Here you can find a list of my refereed and submitted publications. You can also look me up on ADS, arXiv and google scholar.


Curriculum Vitae

I received my B.S. in Physics at the University of Copenhagen in 2012.

I'm currently a graduate student at Columbia University, where I am pursuing a Ph.D. advised by Kathryn V. Johnston, Mary E. Putman and Gurtina Besla.



I am interested in what we can learn about dark matter and galactic properties by studying tidal debris in our own and external galaxies. To investigate this, I use a combination of observations and simulations of Milky Way stellar tidal streams and dwarf galaxy interactions. I have previously done work on the morphology, explosive origin and ionization state of supernova remnants.


Pal 5 and the Galactic Bar

Our own Galaxy, the Milky Way, hosts a so-called Galactic bar, which is a collection of billions of stars coherently rotating in the plane of our Galaxy. In a recent paper, we showed that the Galactic bar, can punch holes in the Palomar 5 stellar stream (see panel "d"), providing an explaination for why the leading arm of Palomar 5 appears to be a lot shorter than the trailing arm as seen in Pan-STARRS (panel "a"), which have otherwise been predicted to be of similar lengths. From our current understanding of our Universe, the Milky Way should be filled with dark matter subhalos of various sizes. One proposed method to detect the subhalos, is to search for them through disturbances in the stellar structure of stellar streams, as the subhalos should create holes if they pass through or close by the stellar streams. However, the Galactic bar can create holes of very similar appearance to those created by subhalos and we caution that one should not necessarily interpret the holes in stellar streams as evidence of the existence of these dark matter subhalos. Additionally, the fact that the Galactic bar can punch holes that grow and have locations along stellar streams dependent on the Galactic bar orientation, mass and pattern speed, provides an intriguing methodology for studying our own Milky Way’s Galactic bar in more detail.



I modeled the dynamical evoltuion of the Milky Way globular cluster, Pal 5, and used the morphology of its stellar tidal stream to rule out a triaxial shape of the dark matter halo in the inner parts of our Galaxy. The Pal 5 stream formed large, two-dimensional "fans" when evolved in a triaxial halo, which is incosistant with observations. The stream properties were easily reproduced in a mildly oblate potential.

Dwarf-Dwarf Interactions

We studied resolved HI maps of a sample of 10 interacting dwarf irregular galaxy pairs at various interacting stages and in various environments within the Local Universe. We found that mutual interactions between the pairs can "park" (but not unbind) gas at large distances, and that only a nearby, massive galaxy prevents the gas from being re-accreted and ultimately removes the gas from the systems.

Modeling dwarf interactions

We use a hybrid of N-body and test particle simulations (Identikit: Barnes & Hibbard 2009) to investigate: how much gas is moved to the outskirts through tidal pre-processing and on what timescales does the gas fall back to the dwarfs? We do this by modeling a subset of the Pearson et al. (2016) pairs, which are pre-infall an alogs of the Magellanic Clouds. This will help us understand the baryon cyle of dwarf galaxy interactions.




Department of Astronomy, Columbia University
Pupin Physics Lab, Office 1414
550 West 120th Street
New York, NY 10027