Staff Members

Andrew Benson

Andrew Benson is a Staff Scientist at the Carnegie Observatories. His research program is focused on understanding the nature of dark matter and the process of galaxy formation, with a particular emphasis on formulating a coherent picture of the many different aspects of these problems. He has developed a model of dark matter and galaxy formation physics, Galacticus, which is available to the community as an open source project. The approach blends both analytic understanding and significant number-crunching that utilizes both in-house and external compute clusters.

Ana Bonaca

Ana Bonaca is Staff Member at Carnegie Observatories. Her specialty is stellar dynamics and her research aims to uncover the structure and evolution of our galaxy, the Milky Way, especially the dark matter halo that surrounds it. In her research, she uses space- and ground-based telescopes to measure the motions of stars, and constructs numerical experiments to discover how dark matter affected them.

Juna Kollmeier - Founding Director

Juna Kollmeier is the Founding Director of CTAC and the Director of SDSS-V, an unprecedented panoptic spectroscopic survey that will yield optical and infrared spectra of over 6 million objects. Her research is primary focused on the emergence of structure in the universe. She combines cosmological hydrodynamic simulations and analytic theory to figure out how the tiny fluctuations in density that were present when the universe was only 300,000 years old, become the galaxies and black holes that we see now, after 14 billion years of cosmic evolution.

Anthony Piro

Anthony Piro is interested in a wide range of topics in theoretical astrophysics, including compact objects, astrophysical explosions, accretion flows, and stellar dynamics. His expertise is in nuclear physics, thermodynamics, condensed matter physics, General Relativity, and fluid and magnetohydrodynamics. He uses this background to predict new observational phenomena, as well as to understand the key underlying physical mechanisms responsible for current observations. He uses a combination of analytic and simple numerical models to build physical intuition for complex phenomena.

Current Postdocs

Mike Grudić

Mike Grudić is a NASA Hubble Fellow working in theoretical and computational astrophysics. His research mainly uses numerical hydrodynamics simulations to study star formation and the interstellar medium on a range of scales, and is particularly interested in understanding how feedback processes can regulate the formation of individual stars, star clusters, and entire galaxies. He is also interested in developing new numerical algorithms and software tools for running, analyzing, and visualizing astrophysical simulations in general.

James Johnson

James Johnson is a CTAC postdoctoral fellow broadly interested in galaxy evolution and the origin of the elements. Most of his work is centered on applying theoretical models of galactic chemical evolution to spectroscopic elemental abundance measurements of resolved stars in the Milky Way and nearby dwarf galaxies. Lately, he is particularly interested in what can be learned from these comparisons regarding how different elements are made in stars. James also dedicates a portion of his time to developing astrophysical software tools for broader use by the community.

Stacy Kim

Stacy Kim is a Nashman/CTAC postdoctoral fellow involved in the search for the particle identity of dark matter.  She runs high-resolution, cosmological hydrodynamical simulations of the smallest and most dark matter dominated objects in the universe---dwarf galaxies---as a part of the EDGE Collaboration, and in particular leads the effort to run them with alternative dark matter physics.  Informed by these simulations, she builds models to understand how dwarf galaxies' formation and evolution are affected by their dark matter content.  She uses these models to determine the signatures that different dark matter particles leave on large populations of dwarf galaxies, and test if they can be detected by current and upcoming surveys

Brenna Mockler

Ethan Nadler

Ethan Nadler is a joint postdoctoral fellow at the Carnegie Observatories and USC. His research combines cosmological simulations, particle theory, and observations of the smallest galaxies and cosmic structures to understand the microphysical properties of dark matter. He also works at the interface of data and dark matter theory with collaborations including the Dark Energy Survey, Dark Energy Science Collaboration, and Satellites Around Galactic Analogs Survey.

Nondh Panithanpaisal

Nondh Panithanpaisal is a joint postdoctoral fellow at the Carnegie Observatories and Caltech. His research focuses on disrupted star clusters known as stellar streams. Using state-of-the-art cosmological baryonic simulations of Milky Way-mass galaxies, he identifies and studies dwarf galaxy streams to constrain the nature of dark matter. At Carnegie, his research aims to develop numerical simulations that include globular cluster streams, which can be used to indicate the presence of substructures within the Galaxy.

Abigail Polin

Abigail Polin is a postdoctoral fellow joint between the Carnegie Observatories and Caltech. She is interested in supernovae and other astrophysical transients.  She models these events using hydrodynamical and radiative transport simulations, and makes testable predictions that are compared to light curves and spectra of observed supernovae. She is also heavily involved in the interpretation of observed transients, especially sub-Chandrasekhar Type Ia supernovae and Calcium-rich transients.

Mattias Raives

Mattias Raives uses MHD simulations to study the explosion mechanism of core-collapse supernovae and the evolution of magnetocentrifugal winds, particularly those of newly born, highly magnetized neutron stars.

Raives obtained his PhD in 2021 from The Ohio State University.

Natalie “Nicole” Sanchez

Natalie “Nicole” Sanchez is a National Science Foundation MPS-Ascend Postdoctoral Fellow at Carnegie Observatories and Caltech. She is a member of the N-Body Shop collaboration and the GM Galaxies team, and she uses cosmological simulations of galaxies to better understand galaxy evolution. Nicole is particularly interested in understanding the mechanisms which drive the metal enrichment of the circumgalactic medium, especially the effects of supermassive black hole feedback. 

David Vartanyan

David Vartanyan is a Hubble Einstein fellow working on the next generation of core-collapse supernovae simulations from bounce to breakout. His interests lie between high-energy astrophysics and high-performance computing. He is interested in deriving remnant properties, including mass distributions and ejecta abundances, from first-principle driven simulations that can reproduce the gamut of supernovae observations. 

Sachi Weerasooriya

Sachi Weerasooriya is a postdoc at Carnegie Observatories working with Andrew Benson. She is interested in galaxy formation and evolution, specifically using Semi-Analytic models. She works on modeling galaxies for future surveys with a focus on accurate modeling of emission lines and calibrating models. She is also interested in dwarf galaxies and impact of major mergers on stellar streams.


Niusha Ahvazi

Niusha Ahvazi is a graduate student at the University of California Riverside and works with Andrew Benson as a UCR-Carnegie Fellow. Her research interests include galaxy formation and evolution, particularly dwarf galaxies in cluster and group environments. She uses N-body/hydrodynamical simulations and semi-analytical models to understand the effects of dark matter physics on the properties of dwarf galaxies.

Annastasia Haynie

Annastasia Haynie is a graduate student at University of Southern California and works at the Carnegie Observatories as a USC-Carnegie Fellow. She is broadly interested in astrophysical explosions and works with Anthony Piro on numerically modeling the shock breakout signal of core-collapse supernovae. At USC, she is also a part of Vera Gluscevic's Cosmolab group, the President of the Women in Physics organization, Vice President of the Graduate Association for Students in Physics, and the Physics Department Liaison for the Women in Science and Engineering organization.

Paul Menker

Paul Menker is a graduate student at the University of Southern California and USC-Carnegie. He works under Andrew Benson, and is broadly interested in the formation of the dark matter halos we observe today.  To this end, he works with ensembles of plausible early universes, and attempts to reconcile these possibilities with observational data. At USC, he is also a member of the High-Energy Theory group, and the Graduate Association for Students in Physics.

Dimple Sarnaaik

Dimple Sarnaaik is a graduate student at the University of Southern California. She works with Andrew Benson on the formation history of dark matter through N-body simulations and analytic modeling. Simultaneously, she is working with Kris Pardo at USC on probing properties of dark matter through its gravitational effects and astrometry. She is also the President of the Graduate Association of Students in Physics at USC and is passionate about science communication.

Armen Tokadjian

Armen Tokadjian is a third year graduate student at the University of Southern California and works with Anthony Piro as a USC-Carnegie Fellow. His research is focused on the dynamics of star-planet-moon systems and the influence of tides on their evolution. He is especially interested in prospects for the habitability of extrasolar worlds.

Yu Zhao

Yu Zhao is a graduate student at the University of Southern California and works with Andrew Benson as a USC-Carnegie Fellow. She is interested in understanding the nature of dark matter and the epoch of reionization with numerical simulations and models.


Kyle Kremer (Einstein Fellow at Caltech)


Former Postdocs

TJ Cox (2009-12) now Data Scientist at Voxer

Selma de Mink (2013-14) now Associate Professor in Astrophysics at Harvard University

Andrew Wetzel (2013-17) now Assistant Professor of Physics at the University of California, Davis

Stephanie Tonnesen (2014-17) now Associate Research Scientist at the Center for Computational Astrophysics at the Flatiron Institute

Jennifer van Saders (2014-17) now Assistant Professor at the Institute for Astronomy at University of Hawaii

Yu Lu (2015-18) now Senior Data Scientist at Lam Research Corporation

Stefano Pasetto (2016-2018) now Research Scientist at Moffitt Cancer Center and Research Institute

Yuan-Sen Ting (2017-2021) now Associate Professor at Australian National Univeristy

Coral Wheeler (2020) now Assistant Professor in the Department of Physics and Astronomy at Cal Poly Pomona

Lina Necib (2020-21) now Assistant Professor in the Department of Physics at MIT

Andrew Emerick (2020-2021) now Senior Data Scientist at Metromile

Lauren Anderson (2019-2021) now Data Science and Visualization Engineer at Heliogen

Xiaolong Du (2018-2022) now Postdoctoral scholar at UCLA

Fangzhou Jiang (2019-2023) now Assistant Professor at KIAA

Ylva Götberg (2019-2023) now Faculty at the Institute of Science and Technology Austria

Shengqi Yang (2021-2024) now Director's Postdoctoral Fellow at Los Alamos National Laboratory