Sabrina Marbut Appel

About Me

As of September 2024, I am an NSF Astronomy and Astrophysics Postdoctoral Fellow, hosted at the American Museum of Natural History. As an NSF Fellow, I am working on understanding star cluster formation and evolution using simulations, with a focus on the role of protostellar jet feedback. I use the simulation framework Torch, which bridges MHD, N-body, and stellar evolution codes through AMUSE.

I completed my PhD thesis in the summer of 2024 at Rutgers University. While at Rutgers, I worked with Prof. Blakesley Burkhart on understanding and developing analytic models of star formation. My graduate work focused on comparing simulations of star-forming regions to analytic models of star formation and included analyzing existing simulation data, running new simulations, and working on code development.

You can read more about my current and past research under the research tab or take a look at my CV here.

In addition to my research, I am dedicated to making the field of astronomy a welcoming and supportive community. During my time as a graduate student at Rutgers, I was significantly involved with the Rutgers Minorities in Physics and Astronomy (MiPA) group at Rutgers, including serving as an officer of the group for multiple years. As a graudate student, I also served as a TA for multiple undergraduate courses. I have mentored undergraduate researchers as both a graduate student and a postdoc.

You can read about my service and outreach work here and about my current and previous teaching and mentoring work here.

I graduated with a B.A. in Physics from Reed College in May 2017 where I also took extensive coursework in English literature. I grew up in Salem, Oregon and recieved an International Baccalaureate (IB) diploma from South Salem High School in 2013. I was raised around horses and I love the mountains! I have been dancing (including ballet and Irish dance) for most of my life. In my free time, I love to play the flute and knit, and I am a voracious reader, especially of science fiction and fantasy.

How to contact me:

You can email me at sappel at amnh.org. If for some reason that is unsuccessful, you can also reach me at sabrina.m.appel at gmail.com.

My ORCID is here: https://orcid.org/0000-0002-6593-3800

And you can find me on github as SabrinaAppel:
• GitHub

Research

My research is focused on understanding star formation at the scale of individual molecular clouds, using numerical simulations and analytical models. I am particularly interested in understanding the role of stellar feedback. Indeed, much of my work so far has focused on the impact of protostellar jet feedback. My work includes analyzing existing simulation data, running new simulations, and code development for star formation simulations. A complete list of the papers that I am on can be found here: ADS Library

Protostellar Jets in Torch

Over the last several years, I have developed a new module for implementing protostellar jet feedback in Torch. Torch is a numerical framework that is optimized for simulating the formation of star clusters from the initial collapse of dense gas through gas expulsion and late stage cluster evolution (Wall et al.2019, 2020). Previous work with Torch has included various modes of stellar feedback, but not protostellar jets (e.g.,Cournoyer-Cloutier et al. 2023). By developing a new module to include protostellar jets, I can use Torch to explore the role of protostellar jets in star cluster formation and evolution. The implementation of my new protostellar jets module -- and initial results from cluster simulations including jets are described in Appel et a. 2025.

Modeling Star Formation

I am also interested in using analytical models, such as the density probability distribution function (PDF), to understand how star formation is influenced by various physical processes. In particular, my work uses the density PDF and measures of the gas dynamics to study simulations of star-forming regions that include different physical processes, including self-gravity, supersonic turbulence, magnetic fields, and protostellar jet feedback.

The following plots show a series of projection plots from the simulations used in our 2022 paper (Appel et al. 2022), which explores the density PDF of simulations that progressively include more physical processes.

We explored the gas dynamics of simulations of star-forming regions in our 2023 paper (Appel et al. 2023). We measured the expansion and compression rates of the gas to explore the role of different physical processes, including protostellar jets, in setting the gas dynamics in star-forming regions.

Publications

A complete list of the papers that I am on can be found here: ADS Library

Selected First and Second Author Papers

† - indicates an undergraduate student mentee

Appel, S. M., Burkhart, B., Mac Low, M.-M., Andersson, E. P., Cournoyer-Cloutier, C., Lewis, S., McMillan, S. L. W., Polak, B., Portegies Zwart, S., Tran, A., & Wilhelm, M. J. C., "Protostellar Jets in Star Cluster Formation and Evolution: I. Implementation and Initial Results", 2025, arXiv e-prints, arXiv:2509.15311, doi:10.48550/arXiv.2509.15311

† Kiihne, A., Appel, S. M., Burkhart, B., Semenov, V. A., Federrath, C., "Fitting Probability Distribution Functions in Turbulent Star-Forming Molecular Clouds", 2025, ApJ, 979, 89, doi:10.3847/1538-4357/ad99d5

Appel, S. M., Burkhart, B., Semenov, V. A., Federrath, C., Rosen, A. L., Tan, J. C., "What Sets the Star Formation Rate of Molecular Clouds? The Density Distribution as a Fingerprint of Compression and Expansion Rates", 2023, ApJ, 954, 93, doi: 10.3847/1538-4357/ace897

Appel, S. M., Burkhart, B., Semenov, V. A., Federrath, C., Rosen, A. L., "The Effects of Magnetic Fields and Outflow Feedback on the Shape and Evolution of the Density Probability Distribution Function in Turbulent Star-forming Clouds", 2022, ApJ, 927, 75, doi: 10.3847/1538-4357/ac4be3

My PhD Thesis

Appel, S. M., "Exploring the effect of protostellar feedback on star formation and molecular cloud dynamics", 2024, Rutgers University, doi:10.7282/t3-p3kg-dk21

Service & Outreach

Contributing to the development of a welcoming and supportive community in the field of Physics and Astronomy is a lasting priority for me. This goal informs my teaching, mentoring, and outreach activities.

While I was a graduate student at Rutgers University, I was significantly involved in the Rutgers Minorities in Physics and Astronomy (MiPA) group, including serving as the Graduate Chair, President, and Past President at various points. MiPA is dedicated to furthering the interests of and developing a sense of community among members of the Rutgers Physics and Astronomy department who are underrepresented or historically marginalized in Physics and Astronomy. As a leader of MiPA, I helped to draft and implement a Charter and Code of Conduct for MiPA. I also founded the Equity and Inclusion Journal Club. Over my time with MiPA, I led or helped organize various events and initiatives.

For more about my service and outreach roles, please take a look at my CV.

Teaching & Mentoring

I believe teaching and mentoring are incredibly important and I find working with students to be deeply rewarding. As a graduate student, I served as a TA for several undergraduate courses of various levels. For instance, in the fall of 2022, I was a TA for an undergraduate Computational Astrophysics course where I helped juniors and seniors progress from the basics of coding in python to running astrophysical simulations. As an undergraduate student, I was a TA for an introductory Physics lab for three years.

Research Mentees

In addition, I have mentored two undergraduate research students.

Fred Javier was an AMNH Physical Sciences REU Student during the Summer of 2025. He is working with Prof. Mordecai-Mark Mac Low and me on a project investigating the density PDFs of simulated (with Torch) star-forming clouds with and without protostellar jets.

Avery Kiihne was a Rutgers undergraduate student (now graduated!!) and worked with Prof. Blakesley Burkhart and me on a research project investigating fitting methods for simulated column density PDFs. You can find their first paper here!

For more about my previous teaching and tutoring experiences, please take a look at my CV.

CV

My CV can be found here. I will do my best to update it regularly.

Disclaimer

Sabrina M. Appel is supported by the National Science Foundation under Award No. 2401740. This website includes material based on work supported by the National Science Foundation under this Award. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author (Sabrina M. Appel) and do not necessarily reflect the views of the National Science Foundation.

Contact

• GitHub

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