Theoretical Astrophysicist · Carnegie Observatories

Andrew Benson

I am a Staff Scientist at the Carnegie Observatories. My research is focused on understanding the nature of dark matter and the process of galaxy formation — combining analytic models, numerical simulations, and large astronomical surveys.

Email ADS Library GitHub ORCID

Research focus

What I work on

Three threads tie my research together: building a coherent theoretical model of galaxy formation; constraining the microphysics of dark matter; and designing the synthetic universes that next-generation surveys need to interpret their data.

Galaxy formation

The Galacticus model

An open-source semi-analytic model of galaxy formation used to interpret observations across cosmic time.

Dark matter

Constraining dark matter microphysics

Using halo substructure, gravitational lensing, and dwarf galaxies to test warm, self-interacting, and other non-CDM models.

Surveys

Synthetic skies for next-gen surveys

Building galaxy mocks for the Roman GRS Project Infrastructure Team and the NASA Open Universe initiative.

Recent work

Selected recent papers

These cards are rebuilt automatically from my NASA ADS library on a weekly schedule. Summaries and figures are generated from the paper itself.

The Astrophysical Journal 2026

Testing Warm Dark Matter with Kinematics of the Smallest Galaxies

Delos, M. Sten, A. Benson, et al.

Every dark matter halo forms with a dense spike at its center, and if dark matter is "warm" enough to erase small-scale structure those spikes are heavy enough to speed up the stars in the smallest galaxies — yet the stars in Tucana V and Triangulum II move far too slowly to match. Taken together, the three faintest Milky Way satellites rule out dark matter particles lighter than 5.8 keV at 95% confidence, a limit that better velocity measurements or the discovery of more such galaxies could sharpen considerably.

ADS · arXiv · DOI

The Astrophysical Journal Letters 2026

Warm, Not Fuzzy: Generalized Ultralight Dark Matter Limits from Milky Way Satellites

Nadler, Ethan O., A. Benson, et al.

Ultralight dark matter produced with structure on small scales behaves less like the "fuzzy" dark matter usually assumed and more like warm dark matter, with an additional wave-interference effect that adds small-scale structure back in. Matching this against the observed population of Milky Way satellite galaxies sets a new lower limit on the particle mass that depends on the scale at which the field's structure peaks.

ADS · arXiv · DOI

arXiv e-prints 2026

A Unified Halo Mass Function Across Dark Matter Models from High-Resolution Multi-Scale Simulations

Benson, Andrew J. et al.

This research presents a highly precise model for the dark matter halo mass function, applicable across various dark matter theories and effective over a vast range of halo masses. The model's accuracy and ability to account for environmental influences make it essential for future dark matter studies and data analysis.

ADS · arXiv · DOI

arXiv e-prints 2026

Mixed Dark Matter: Limits from the Milky Way Satellite Galaxies

Crumrine, Wendy, A. Benson, et al.

This study establishes new constraints on mixed dark matter models using data from Milky Way satellite galaxies, revealing how the presence of different dark matter components affects the formation of small-scale structures. The findings indicate that as the fraction of non-standard dark matter increases, the constraints on its properties weaken, highlighting the need for future surveys to refine these limits further.

ADS · arXiv · DOI

arXiv e-prints 2026

The free-streaming length of dark matter from JWST observations of 28 strong gravitational lenses

Gilman, D., A. Benson, et al.

This study uses observations from the James Webb Space Telescope to measure the properties of dark matter halos in 28 strong gravitational lens systems, providing significant constraints on the free-streaming length of dark matter. The results support the cold dark matter model by ruling out deviations on large scales and establishing lower limits on the mass of thermal relic dark matter particles.

ADS · arXiv · DOI

Physical Review D 2026

Calibrating the self-interacting dark matter gravothermal catastrophe with N-body simulations

Mace, Charlie, A. Benson, et al.

Dark matter halos that interact with themselves eventually undergo a runaway collapse of their inner regions, a process usually modelled by treating the dark matter as a heat-conducting fluid with one free parameter that different studies have set differently. A suite of N-body simulations shows that this parameter does not depend on halo mass, concentration, or interaction strength, allowing fast and consistent predictions without running new simulations.

ADS · arXiv · DOI

See all recent papers →

Open source

Galacticus

Most of my modeling work happens inside Galacticus, an open-source semi-analytic model of galaxy formation that I wrote and continue to develop. It's used by groups around the world to study dark matter, galaxy evolution, and forecast observations for upcoming surveys. See the full software stack →