Sarah Pearson

Graduate Student, Columbia University


I am a Danish computational astrophysicist currently finishing my PhD in the
Department of Astronomy at Columbia University
where I study galactic dynamics, stellar streams and interacting dwarf galaxies.

Publications

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

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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.

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Research

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.

Models

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.

Streams

Stream-Fanning

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.
Stream-Fanning

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.
Idkit

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 in dwarf-dwarf interactions and on what timescales gas falls back to the dwarfs? We do this by modeling NGC 4490/85 which are included in the Pearson et al. (2016) sample of dwarf pairs. The pair is a pre-infall analog of the Magellanic Clouds.

Outreach

Motivated by my passion for teaching, outreach and storytelling, in 2017 I launched the outreach initiative "Space with Sarah" with producer, Brett Van Deusen, sharing knowledge of our Universe through short videos on YouTube. The topics are selected based on the most frequently asked astronomy related questions I receive from non-astronomers in my everyday life. The video topics include questions such as "When will the Sun turn off?", "How can we explode a star into a black hole?" and "How can galaxies collide in an expanding Universe?". The target audience is young adults and all videos have Danish and English subtitles. The channel has >90,000 views and you can subscribe here>>


The four main goals with the Space with Sarah outreach program are:
1) To share knowledge on our Universe with a broad audience.
2) To make science more accessible to the public (explain how we know what we know).
3) To inspire young, new scientists and break the stereotype of "who is a scientist".
4) To increase the visibility of women in science (and of female scientists who communicate on YouTube).

Streams

Instagram

Using associated social media accounts (@spacewsarah), I document my everyday life as a computational astrophysicist with goals of breaking “who is a scientist”-stereotypes and hopefully inspiring young women to pursue science and tech careers.
Stream-Fanning

Danish astronomy blog

I started a collaboration with the Danish engineering magazine Ingeniøren in 2018 with the goal of sharing knowledge with Danes on astronomy, physics and science through blog posts accompanied by the Space with Sarah videos with Danish subtitles.
Idkit

Popular science articles

My recent article for the Danish Physics & Astronomy magazine KVANT made it onto their April 2018 cover. In the article I discuss my Nature Astronomy paper on Stellar streams & the Galactic bar and explain how the Milky Way's bar can punch holes in stellar streams.


Other recent outreach-related activities

  • Live national TV interview on the 2017 total solar eclipse with Erica Hill on HLN (link works from US only)
  • Collaboration video with Fraser Cain from Universe Today on "Dark Matter Galaxies".
  • Video interview with the Columbia U. Cool Worlds YouTube channel run by Prof. D. Kipping.
  • Interview with the Columbia Graduate School of Arts & Sciences.
  • NASA Space Apps NYC talk on exoplanets during the NASA space apps challange 2017.
  • Collaboration video with Dr. J. Davenport who has his own astronomy video-log on YouTube.
  • Columbia "giving day" video interview for the Columbia Graduate School of Arts & Sciences giving day 2017.
  • University of Copenhagen article about my recent Danish Women in Physics Prize 2017.

  • The most recent "Space with Sarah" video

    In the latest video I explain what research I work on and answer questions from season 1 of the show.

    Contact

    Email (professional/outreach requests):

    spearson@astro.columbia.edu / spacewsarah@gmail.com

    Address:

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

    Twitter:

    @spacewsarah