Spectroscopy of Ultra-diffuse Galaxies in the Coma Cluster

Jennifer Kadowaki, Dennis Zaritsky, R. L. Donnerstein

Research output: Contribution to journalArticlepeer-review

49 Scopus citations


We present spectra of five ultra-diffuse galaxies (UDGs) in the vicinity of the Coma cluster obtained with the Multi-object Double Spectrograph on the Large Binocular Telescope. We confirm four of these as members of the cluster, quintupling the number of spectroscopically confirmed systems. Like the previously confirmed large (projected half-light radius >4.6 kpc) UDG, DF44, the systems we targeted all have projected half-light radii . As such, we spectroscopically confirm a population of physically large UDGs in the Coma cluster. The remaining UDG is located in the field, about 45 Mpc behind the cluster. We observe Balmer and Ca ii H and K absorption lines in all of our UDG spectra. By comparing the stacked UDG spectrum against stellar population synthesis models, we conclude that, on average, these UDGs are composed of metal-poor stars ([Fe/H] ≲ -1.5). We also discover the first UDG with [O ii] and [O iii] emission lines within a clustered environment, demonstrating that not all cluster UDGs are devoid of gas and sources of ionizing radiation.

Original languageEnglish (US)
Article numberL21
JournalAstrophysical Journal Letters
Issue number2
StatePublished - Apr 1 2017


  • galaxies: distances and redshifts
  • galaxies: general
  • galaxies: stellar content

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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