The Milky Way’s satellites help reveal link between dark matter halos and galaxy formation

A simulation of the formation of dark matter structures from the early universe until today. Gravity makes dark matter clump into dense halos, indicated by bright patches, where galaxies form. Image Credit: Ralf Kaehler/SLAC National Accelerator Laboratory

Over the past five years, the Dark Energy Survey, a DOE-funded project led by Fermilab, has revolutionized our view of small satellite galaxies. DES discovered a large number of tiny galaxies close to the Milky Way’s largest satellites, the Magellanic Clouds, suggesting that multiple galaxies may have been captured by the Milky Way at the same time. In this recent analysis (resulting in two articles published in Astrophysical Journal), the DES group has combined observations from DES with those from the Pan-STARRS survey to cover 75% of the sky and confirm this hypothesis. In order to understand the sensitivity of these searches, the Fermilab group tested the algorithms ability to detect simulated galaxies injected into the survey data. The results of this search were then interpreted in the context of cosmological simulations to understand the connection between dark matter halos and the galaxies that reside in them. Analysis of the DES and Pan-STARRS data was led by Wilson Fellow Alex Drlica-Wagner and involved former Lederman Fellow Ting Li, Fermilab Scientist Brian Yanny, and many other collaborators from DES.

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