2020/09/23 by Akos Bogdan, Ákos Bogdán
Physics and Astronomy · #Astronomy and Astrophysical Research #Dark Matter and Cosmic Phenomena #Dark galaxy #Dark matter #Dwarf galaxy #Dwarf spheroidal galaxy #Galaxies: Formation, Evolution, Phenomena #Galaxy #Milky Way #astro-ph.GA #astro-ph.HE
paper · pdf · doi:10.3847/2041-8213/abb886
5 pages, 1 figure, 2 tables, accepted for publication in The Astrophysical Journal Letters, some typos fixed
openalex created_date 2020/09/21 · arxiv created 2020/09/23 · openalex publication_date 2020/09/28 · arxiv updated 2020/10/07 · openalex updated_date 2026/08/06
Abstract Due to the peculiar properties of ultra-diffuse galaxies (UDGs), understanding their origin presents a major challenge. Previous X-ray studies demonstrated that the bulk of UDGs lack substantial X-ray emission, implying that they reside in low-mass dark matter halos. This result, in concert with other observational and theoretical studies, pointed out that most UDGs belong to the class of dwarf galaxies. However, a subset of UDGs is believed to host a large population of globular clusters (GCs), which is indicative of massive dark matter halos. This, in turn, hints that some UDGs may be failed L ⋆ galaxies. In this work, I present Chandra and XMM-Newton observations of two archetypal UDGs, Dragonfly 44 and DF X1, and I constrain their dark matter halo mass based on the X-ray emission originating from hot gaseous emission and from the population of low-mass X-ray binaries residing in GCs. Both Dragonfly 44 and DF X1 remain undetected in X-rays. The upper limits on the X-ray emission exclude the possibility that these galaxies reside in massive ( M vir ≳ 5 × 10 11 M ⊙ ) dark matter halos, suggesting that they are not failed L ⋆ galaxies. These results demonstrate that even these iconic UDGs resemble to dwarf galaxies with M vir ≲ 10 11 M ⊙ , implying that UDGs represent a single galaxy population.