Are the ultra-faint dwarf galaxies just cusps?

Adi Zolotov, David W. Hogg, Beth Willman

    Research output: Contribution to journalArticlepeer-review


    We develop a technique to investigate the possibility that some of the recently discovered ultra-faint dwarf satellites of the Milky Way might be cusp caustics rather than gravitationally self-bound systems. Such cusps can form when a stream of stars folds, creating a region where the projected two-dimensional surface density is enhanced. In this work, we construct a Poisson maximum likelihood test to compare the cusp and exponential models of any substructure on an equal footing. We apply the test to the Hercules dwarf (d ∼ 113 kpc, MV ∼-6.2, e ∼ 0.67). The flattened exponential model is strongly favored over the cusp model in the case of Hercules, ruling out at high confidence that Hercules is a cusp catastrophe. This test can be applied to any of the Milky Way dwarfs, and more generally to the entire stellar halo population, to search for the cusp catastrophes that might be expected in an accreted stellar halo.

    Original languageEnglish (US)
    JournalAstrophysical Journal Letters
    Issue number1 PART II
    StatePublished - Jan 20 2011


    • Galaxies: dwarf
    • Galaxy: halo

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science


    Dive into the research topics of 'Are the ultra-faint dwarf galaxies just cusps?'. Together they form a unique fingerprint.

    Cite this