Hellman Fellowship


The Hellman Fellows Program has selected me as a 2019 Hellman Fellow, for my proposed research program: Using stars as gravitational antennae to measure dark matter. The Hellman Fellows Program supports the research of assistant professors, and this fellowship grant will help support the work of our group to use our Latte FIRE simulations to develop new dynamical models to measure the nature of dark matter, by using streams of stars as ‘gravitational antennae’ for interactions with dark-matter subhalos, thus translating dark-matter theories directly into measurable predictions for stellar dynamics.


Scialog Fellowship and Heising-Simons grant

The Research Corporation, with support of the Heising-Simons Foundation and the Kavli Foundation, once again has selected me to be a Scialog Fellow. I was delighted again to join 50 fellows at the 2019 Scialog conference on Time Domain Astrophysics in Tuscon, Arizona, during which we discussed exciting applications of data from NASA’s TESS satellite, ESA’s Gaia satellite, and the Zwicky Transient Facility.

I am excited that the Heising-Simons Foundation selected the grant that Keith Hawkins, Jennifer van Saders, and I submitted during this meeting: Aging Gracefully: Stellar Ages Across the HR Diagram and Their Implications for Galactic Archaeology. With this seed funding, our goal is two-fold:

  1. Use the Latte FIRE-2 Milky Way-like simulations as a testbed to quantify the observational precision in stellar ages that we require for specific Milky Way studies.
  2. Compile a unified framework for combining/comparing different ways of measuring stellar ages in an easy-to-use Baysian framework.

    I am excited to work with Keith and Jen on this project over the next year!

Sierra Chapman graduates with Highest Honors

Sierra Chapman

Sierra Chapman, who has been pursuing research with our group as part of her Honor’s Thesis, graduates with her bachelor’s degree in physics. Moreover, for her excellent work on her Honors Thesis, in which she predicts the population of low-mass dark-matter subhalos that orbit close to the Milky Way, she earned Highest Honors. Sierra will continue to work with us over the summer to translate her thesis work into a paper to submit for publication. Congratulations Sierra!

first student-led paper from our group: radial distribution of satellite galaxies

Radial distribution of satellite galaxies around MW-mass hosts in the FIRE simulations, as compared with the MW and M31

Excited to announce the first student-led paper from our group, led by PhD student Jenna Samuel: A profile in FIRE: resolving the radial distributions of satellite dwarf galaxies in the Local Group with simulations. Jenna examined the radial distribution of satellite galaxies around MW/M31-mass hosts in our FIRE simulations, which she showed are consistent with the Local Group. The satellites of MW-like galaxies from the SAGA survey have 2D radial profiles that are similar to our simulations too. Interestingly, more massive host galaxies have fewer satellites at small distances, which is caused by tidal destruction from the central galaxy. Jenna also quantified the destruction of subhalos by comparing our baryonic simulations to their dark matter-only versions, finding 10x destruction within the inner 20 kpc. Finally, Jenna applied approximations of observational completeness in the LG to our simulations, predicting that there may be 2-10 satellites with stellar mass > 10^5 Msun to be discovered around the MW, and 6-9 around M31. Congratulations to Jenna for such a good first paper!

Frontera supercomputer: 106 million core-hour allocation

The National Science Foundation (NSF) has awarded our FIRE collaboration an allocation of 106 million core-hours on the Texas Advanced Computing Center‘s new Frontera Supercomputer, which debuted as 5th most powerful supercomputer in the world. With this allocation, we plan to push forward on a range of large simulation projects, including our FIREbox large-volume simulation and a suite of simulations including alternative dark matter models. Congratulations to the whole FIRE collaboration!

synthetic Gaia surveys of the Latte simulations

synthetic Gaia DR2-like surveys from the Latte suite of FIRE-2 cosmological simulations of Milky Way-mass galaxies

We are excited to announce the release of our synthetic Gaia DR2-like surveys from our Latte suite of FIRE-2 cosmological simulations of Milky Way-mass galaxies. We generated 9 synthetic surveys from 3 different simulations, using 3 solar viewpoints per simulation.  Along with these synthetic surveys, we also released full simulation snapshots at z = 0, including all particle data, from the 3 Latte simulations. All data is available at , and the paper that describes our methods is Sanderson et al 2018.

Congratulations to Robyn Sanderson for leading this ambitious effort, including developing our new Ananke framework for generating synthetic surveys from baryonic simulations. Thanks to Kacper Kowalik and Matt Turk for tremendous help in hosting this data via the awesome .

We hope that these cosmological synthetic Gaia DR2-like surveys will provide useful tools to the scientific community in interpreting the amazing data of the Milky Way from the Gaia satellite mission.

NASA Astrophysics Theory Program (ATP) grant: modeling the Milky Way

NASA’s Astrophysics Theory Program (ATP) has awarded our team

a grant for Modeling Galactic Archaeology of the Milky WayKudos in particular to Robyn Sanderson, who led a significant component of our science case. Our primary goal with this grant is to turn our Latte suite of FIRE-2 simulations of Milky Way-like galaxies into synthetic star catalogs and mock surveys of the Milky Way, and make these datasets publically available, to provide theoretical predictions and tools for the many surveys of the Milky Way, including the Gaia satellite.

James Webb Space Telescope (JWST) Early Release Science program: resolved stellar populations


The James Webb Space Telescope (JWST) announced its first competitive observing allocations for the Cycle 1 Early Release Science (ERS) program, and the allocation committee has awarded our team, led by Dan Weisz, 27 hours for The Resolved Stellar Populations Early Release Science Program. While much focus of JWST for galaxy science has emphasized high-redshift distant galaxies, JWST also promises significant advancements in observations of resolved stellar populations in nearby low-mass (dwarf) galaxies and star clusters, to understand their star formation histories, stellar initial mass functions, dust extinction, and (combined with HST) proper motions. Congratulations to Dan and the whole team!