Sabrina Marbut Appel

CV

My CV can be found here. I do my best to update it regularly. A complete list of the papers that I am a co-author on can be found in this SciX Library.

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 mentoring philosophy and research mentees here, and about my teaching philosophy and experience 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 in this SciX 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

Teaching

Teaching Philosophy

Teaching is a foundational part of developing future generations of scientists, making it one of our most important roles as professional scientists. Indeed, teaching and mentoring are fundamentally intertwined and so there is a lot of overlap between my teaching and mentoring philosophies. My teaching philosophy shares a foundation with my mentoring philosophy and is guided by the dual principles of respect and joy: respect for the student, the material, and the community; and sharing with students my joy in the study of science, in learning new things, and in the collaborative process of research. My approach to teaching centers around ensuring that every student is given an equal opportunity to succeed in their academic goals, whether that is in an individual course, in pursuit of their degree, or in developing long-term career goals. My goal in every teaching moment is to respect the individual goals of my students and to share my knowledge and enjoyment of physics and astronomy with them, whether this is their only STEM course or one of many.

In practice, this means:

• Recognizing individuality: My teaching goals mean respecting each student as an independent learner with their own background, goals, and needs. This also means celebrating each student successes, but also supporting them through adversity. Respecting the different goals of students also translates into course design: for example, the goals of an upper-level major course should focus on developing the skills needed for professional scientists, while the goals of an intro course for non-majors should focus on giving students a positive experience with STEM that will encourage them to be life-long learners of science.
• High expectations paired with robust support: Respect for students as independent learners means pairing high expectations for each student with sufficient support and compassion to help them meet those expectations.
• Committing to accessibility: Respect for students as individuals also means committing to prioritizing accessibility and striving to make the course, the classroom, or the research environment accessible to every student. This includes adapting to formal accommodations, adjusting expectations when needed, or prioritizing accessible course design, such as including material in multiple formats and multiple modes of assessments. I prioritize clear communication of expectations and of evaluation strategies.
• Learning from education research: I strive to learn from education researchers to find ways to improve my teaching, including by finding ways to help students develop a scientific identity and incorporating active learning strategies. Active learning strategies are important for ensuring that each student has a chance to engage with material in a way that encourages enthusiasm and genuine engagement.
• Prioritizing interactions with students: These principles of respect and joy also translate into prioritizing interactions with students, including questions and discussion. I encourage questions from students and strive to answer every question thoughtfully. I make a point of admitting when I do not know the answer to a question to show that it is okay to not know things sometimes, while explaining how I would go about finding the answer.
• Sharing my enthusiasm: I find that teaching is most successful when I can spark true enthusiasm in my students. I find great joy in the study of astronomy and physics, and sharing my enjoyment of the material and the process of science with students is a foundational goal for me every time I walk into a classroom or student meeting.

As I note in my mentoring philosophy, no matter our career stage, we are all learning and continuously growing our professional skills. For me, this includes always seeking ways to be a better teacher and mentor. And so, while this statement reflects my teaching philosophy as of September 2026, I fully expect that my philosophy will develop with time. Thus, this statement may be updated at any time.

Many thanks to everyone whose conversation and ideas contributed to me refining my ideas! If you are inspired by this statement and wish to incorporate elements of it in your own work, that’s wonderful! If you do use a direct quote, please include appropriate credit, such as a citation to this statement.

Teaching Experience

As an NSF Astronomy & Astrophysics Postdoctoral Fellow I am working on a project to develop high school curriculum materials that introduce students to the basic ideas of computational astrophysics. These materials will introduce students to the fact that coding is a tool for science and that science can be studied with computers. I am collaborating with experienced educators at the Gottesman Center for Teaching and Learning on this project.

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.

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

Mentoring

Mentoring Philosophy

I consider mentoring to be one of the most important professional commitments of any professional scientist. Mentoring is crucial for developing future scientists and for maintaining a welcoming, supportive, and vibrant scientific community. Thus, my mentoring philosophy is guided by the dual principles of respect and joy. I believe that every mentoring interaction should be guided by respect for the unique needs, perspectives, and backgrounds of my mentees and myself, and by the goal of fostering true enjoyment of the study of science and of the field of astrophysics. Developing and maintaining a supportive community that enables the development of independent, successful scientists requires proactive and ongoing work.

In practice, this translates to a few key principles:

• Honesty and respect: Responsible and honest conduct of research is always a must.  But more than that, research is a human endeavor.  I strive to be honest about my own strengths, weaknesses, and boundaries, and will respect those of my mentees. I will encourage my mentees to do the same. I always respect my mentees as capable and independent scientists.
• Advocacy: As a mentor, one of my key roles is to advocate for my mentees. This means advertising their work alongside my own, helping them make relevant professional connections (including with other potential mentors), and championing their needs. This also means working with them to understand their unique career goals, supporting their progress towards achieving those goals, and helping them to develop their identity as a scientist. Moreover, science is collaborative. This means that the successes of my mentees contribute to my own success and vice versa. Therefore, I share responsibility for helping my mentees succeed in their goals. None of us are in this alone!
• Clear and effective communication: Effective mentoring must be founded on clear, effective, and timely communication. This includes clearly communicating boundaries with respect to work hours and communication methods. This also includes establishing a mentoring agreement at the start of any long-term mentoring relationship.
• Transparency: Respect for the needs and goals of my mentees makes transparency crucial. This means clearly establishing expectations early on, as well as clearly and promptly communicating any changes to expectations, goals, or boundaries. This includes establishing a mentoring agreement at the start of any long-term mentoring relationship; communicating clearly about meeting frequency, expected hours, and communication methods; and honest evaluation of mentor and mentee progress.
• Adaptability, flexibility, and compassion: Every mentee has unique needs, strengths, and goals. And sometimes things change unexpectedly. Part of showing respect for my mentees and for myself is committing to adapting to the needs and long-term goals of each mentee. This can mean adjusting project goals and expectations to fit each student’s goals and skills, adjusting communications methods as needed, and approaching unexpected developments with compassion and patience. This overlaps with the next principle:
• We are both human: I commit to always having compassion for, and patience in the face of, unexpected professional and personal challenges. And I will always strive to share my joy in the study of astrophysics with mentees and to celebrate their successes. In addition, valuing our shared humanity means that any time I communicate with students, evaluate student work, or write reference letters, I will use my own words and will not use generative AI.
• Peer mentoring and informal mentoring are important: In addition to formal mentoring relationships established with research mentees or in a classroom setting, I value the opportunities I have to be an effective and supportive mentor in any setting or for any duration. I always strive to make time to support my peers and colleagues of any career stage with the same care I show any mentee.

I end this statement with the observation that, no matter our career stage, we are all learning and continuously growing our professional skills. For me, this includes always seeking ways to be a better mentor. And so, while this statement reflects my mentoring philosophy as of September 2026, I fully expect that my philosophy will develop with time. Thus, this statement may be updated at any time.

This statement was inspired in part by Project BUILD and discussions with colleagues. Many thanks to everyone whose conversation and ideas contributed to me refining my ideas! If you are inspired by this statement and wish to incorporate elements of it in your own work, that’s wonderful! If you do use a direct quote, please include appropriate credit, such as a citation to this statement.

Research Mentees

Over the years, I have mentored four undergraduate research students.

Edwin Lliguicota was an AstroComNYC student at AMNH during the Summer of 2026. He worked with me to explore the formation of runaway stars in star clusters simulated with Torch. He is now an undergraduate student at Cornell University.

Donglin Wu is a Yale undergraduate student and was a summer research student at AMNH during the Summer of 2026. He is working with Prof. Mordecai-Mark Mac Low, Dr. Brooke Polak, and me on the escape of UV radiation from star clusters simulated with Torch.

Fred Javier was an AMNH Physical Sciences REU Student during the Summer of 2025 and returned as a summer research student again in the Summer of 2026. He is working with Prof. Mordecai-Mark Mac Low and me on a project investigating the temperature and density PDFs, and temperature-density phase space, of star-forming clouds with and without protostellar jets that were simulated with Torch.

For more about my previous mentoring experiences, please take a look at my CV.

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.

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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