AffiliationUniv Arizona, Steward Observ
Univ Arizona, Dept Astron
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PublisherIOP PUBLISHING LTD
CitationSpectroscopy of Ultra-diffuse Galaxies in the Coma Cluster 2017, 838 (2):L21 The Astrophysical Journal
Rights© 2017. The American Astronomical Society. All rights reserved.
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AbstractWe 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 > 2.9 kpc. 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] less than or similar to -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.
VersionFinal published version
SponsorsNSF [AST-9987045]; NSF Telescope System Instrumentation Program (TSIP); Ohio Board of Regents and the Ohio State University Office of Research