Extensive Globular Cluster Systems Associated with Ultra Diffuse Galaxies in the Coma Cluster

Journal Article · Thu Jul 20 04:00:00 EDT 2017 · Astrophysical Journal Letters

DOI:https://doi.org/10.3847/2041-8213/AA7CA2· OSTI ID:22872579

Van Dokkum, Pieter; Danieli, Shany; Merritt, Allison; Mowla, Lamiya ^[1]; Abraham, Roberto; Lokhorst, Deborah; Zhang, Jielai ^[2]; Romanowsky, Aaron J.; Brodie, Jean ^[3]; Conroy, Charlie ^[4]

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1. Astronomy Department, Yale University, New Haven, CT 06511 (United States)
2. Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada)
3. University of California Observatories, 1156 High Street, Santa Cruz, CA 95064 (United States)
4. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA (United States)

We present Hubble Space Telescope (HST) imaging of two ultra diffuse galaxies (UDGs) with measured stellar velocity dispersions in the Coma cluster. The galaxies, Dragonfly 44 and DFX1, have effective radii of 4.7 kpc and 3.5 kpc and velocity dispersions of 47{sub −6}{sup +8} km s{sup −1} and 30{sub −7}{sup +7} km s{sup −1}, respectively. Both galaxies are associated with a striking number of compact objects, tentatively identified as globular clusters: N{sub gc}=74±18 for Dragonfly 44 and N{sub gc}=62±17 for DFX1. The number of globular clusters is much higher than expected from the luminosities of the galaxies but is consistent with expectations from the empirical relation between dynamical mass and globular cluster count defined by other galaxies. Combining our data with previous HST observations of Coma UDGs we find that UDGs have a factor of 6.9{sub −2.4}{sup +1.0} more globular clusters than other galaxies of the same luminosity, in contrast to a recent study of a similar sample by Amorisco et al., but consistent with earlier results for individual galaxies. The Harris et al. relation between globular cluster count and dark matter halo mass implies a median halo mass of M{sub halo}∼1.5×10{sup 11} M{sub ⊙} for the sixteen Coma UDGs that have been observed with HST so far, with the largest and brightest having M{sub halo}∼5×10{sup 11} M{sub ⊙}.

• OSTI ID: 22872579
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 844; ISSN 2041-8205
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
DISPERSIONS
GALAXIES
GALAXY CLUSTERS
LUMINOSITY
MASS
NONLUMINOUS MATTER
TELESCOPES