Matthew G. Walker
Astrophysics & Cosmology
Wean Hall 8408
Education & Professional Experience
Ph.D.: University of Michigan (2007)
American Astronomical Society
Honors and Awards:
Martin and Beate Block Award, Aspen Center for Physics (2013)
Hubble Post-doctoral Fellowship (2010)
Assistant Professor, Carnegie Mellon University, 2013–
Post-doctoral Research: Harvard University, 2010–13
Post-doctoral Research: University of Cambridge (U.K.), 2007–10
I study the astrophysical properties of dark matter, thus far via optical imaging, spectroscopy and dynamical modeling of the 'dwarf' galaxies that surround the Milky Way and neighboring Andromeda. The dwarf galaxies include the oldest, smallest and 'darkest' (i.e., composed almost entirely of dark matter) galaxies known, and currently represent the smallest physical scales (sizes of ≈ 100 light years, speeds of a few kilometers per second, masses of ≈ 100,000 Suns) that are associated empirically with dark matter. If dark matter is made from some kind of new fundamental particle, then the manner in which dark matter can form 'clumps' at such small scales can help to decide among various ideas about the properties of that particle. By measuring the spatial distribution of dark matter in dwarf galaxies, I aim to help figure out what the dark matter actually is. Thus my research has wandered into the intersection of dynamics, cosmology and particle physics.
For this work I use some of the world's largest optical telescopes, including the 6.5-meter Magellan telescopes at Las Campanas Observatory in Chile, the 6.5-meter MMT at Mt. Hopkins, Arizona, and the 8.2-meter Very Large Telescope at Cerro Paranal in Chile. I am also a member of the Sloan Digital Sky Survey IV collaboration.
Night sky at the Magellan telescopes of Las Campanas Observatory, Chile.
(Photography and video editing by Mike Padilla, @mrpadillaphotography).
Gabriel Torrealba et al., The hidden giant: discovery of an enormous Galactic dwarf satellite in Gaia DR2, MNRAS 488, 2743 (2019)
R. Errani, J. Peñarrubia, M.G. Walker, Systematics in virial mass estimators for pressure-supported systems, MNRAS 481, 5073 (2018)
Meghin E. Spencer et al., The Binary Fraction of Stars in Dwarf Galaxies: The Cases of Draco and Ursa Minor, Astronomical J. 156, 257 (2018)
J.I. Read, M.G. Walker, P. Steger, The case for a cold dark matter cusp in Draco, MNRAS, 481, 860 (2018)
S.E. Koposov, M.G. Walker, V. Belokurov, et al., Snake in the Clouds: a new nearby dwarf galaxy in the Magellanic bridge, MNRAS 479, 5343 (2018)
J.I. Read, M.G. Walker, P. Steger, Dark Matter Heats up in Dwarf Galaxies, MNRAS 484, 1401 (2019)
Anirudh Chiti et al., Detection of a Population of Carbon-enhanced Metal-poor Stars in the Sculptor Dwarf Spheroidal Galaxy, Astrophys. J. 856, 142 (2018)
Carles Badenes et al., Stellar Multiplicity Meets Stellar Evolution and Metallicity: The APOGEE View, Astrophys. J. 854, 147 (2018)
Christian I. Johnson et al., Exploring the Chemical Composition and Double Horizontal Branch of the Bulge Globular Cluster NGC 6569, Astronomical J. 155, 71 (2018)
Evan Tucker et al., Magellan/M2FS Spectroscopy of Galaxy Clusters: Stellar Population Model and Application to Abell 267, Astronomical J. 154, 3 (2017)
Nelson Caldwell et al., Crater 2: An Extremely Cold Dark Matter Halo, Astrophys. J. 839, 1 (2017)
Alex Geringer-Sameth et al., Indication of Gamma-Ray Emission from the Newly Discovered Dwarf Galaxy Reticulum II, Phys. Rev. Lett. 115, 81101 (2015)