paper

Spectroscopy of Ultra-diffuse Galaxies in the Coma Cluster

arXiv:1703.02042 · doi:10.3847/2041-8213/aa653d

Abstract

We present spectra of 5 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 4 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 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 Mpc behind the cluster. We observe Balmer and Ca II H \& 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] ). We also discover the first UDG with [OII] and [OIII] emission lines within a clustered environment, demonstrating that not all cluster UDGs are devoid of gas and sources of ionizing radiation.

5 pages, 4 figures

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