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 Supplement Series 2026

A Graph-based Neural-network Surrogate Model for an Accelerating Semianalytical Model of Galaxy Formation and Evolution

Li, Xuejie, A. Benson, et al.

A neural network that works directly on the branching histories of dark matter halos reproduces the galaxy properties predicted by a full semi-analytic model — stellar mass, luminosity, rotation, gas metal content, and star formation rate — over the first twelve billion years of cosmic time, matching stellar masses to within 0.19 to 0.28 dex. A single such surrogate holds up across different model parameter choices and halo histories, offering a fast stand-in when exploring the parameter space of galaxy formation models.

ADS · arXiv · DOI

The Astrophysical Journal 2026

Correlation between Baryonic Process and Galaxy Assembly Bias

Xiao, Zilan, A. Benson, et al.

For galaxies picked by their mass in stars, the extra clustering that depends on more than the mass of their dark matter halos tracks most closely how gas cools and how stars blow gas back out, regardless of how common the galaxies are. For galaxies picked by how fast they form stars, the most closely linked process shifts from star formation itself to gas cooling as the sample includes more common galaxies.

ADS · arXiv · DOI

arXiv e-prints 2026

Emulator-Assisted Calibration of a Semi-Analytic Galaxy Formation Model for the Roman Galaxy Redshift Survey

Robertson, Andrew, A. Benson, et al.

Fast statistical stand-ins for the Galacticus galaxy formation model make it practical to calibrate it against several sets of observations at once — galaxy masses, sizes, star formation rates, metallicities, central black hole masses, and hydrogen line emission — which breaks degeneracies that fits to any single dataset leave unresolved and exposes where observations pull in different directions. The calibrated model reproduces the abundance and evolution of hydrogen-line-emitting galaxies, making it suitable for building mock catalogues for the Roman Galaxy Redshift Survey.

ADS · arXiv · DOI

The Open Journal of Astrophysics 2026

The Curious Case of Centaurus A: On the Subject of the Quenched satellites

Weerasooriya, Sachi, A. Benson, et al.

Models calibrated to the Milky Way overpredict the number of bright satellite galaxies within 150 kpc of Centaurus A by a factor of four, and chance alone cannot account for the shortfall. The missing satellites occupy the same region as Centaurus A's kiloparsec-scale radio lobes, and heating driven by the host's central black hole can suppress star formation in them enough to explain the deficit.

ADS · arXiv · DOI

The Open Journal of Astrophysics 2026

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

Benson, Andrew et al.

A single fitting formula, calibrated against both large cosmological volumes and high-resolution zoom-in simulations, reproduces the abundance of dark matter halos to about 12% over ten orders of magnitude in mass and across dark matter models including thermal relics, axions, and dark-sector interactions, with departures of 40 to 50% in a few mass ranges. Extended with a simple treatment of surroundings, it also captures how the local density of the universe shifts the number of halos.

ADS · arXiv · DOI

Physical Review Letters 2026

Free-Streaming Length of Dark Matter from JWST Observations of 28 Strong Gravitational Lenses

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

The pattern of distortions in 28 quadruply imaged quasars observed by JWST shows that dark matter still clumps on scales below about 10^7 solar masses, limiting the distance its particles stream before structure forms to under 6 to 7 kpc and requiring a thermal relic particle heavier than about 7 keV. Assuming dark matter is cold instead, the mass held in small clumps around elliptical lens galaxies is measured directly, confirming a central prediction of the standard picture.

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 →