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Discovery of an Ultra-Diffuse Galaxy in the Pisces-Perseus Supercluster
The Astronomical Journal (2016)
  • David Martínez-Delgado, Universität Heidelberg
  • Ronald Läsker, Max-Planck-Institut für Astronomie
  • Margarita Sharina, Russian Academy of Sciences
  • Elisa Toloba, University of California Observatories
  • Jürgen Fliri, Instituto de Astrofísica de Canarias
  • Rachael Beaton, The Observatories of the Carnegie Institutions for Science
  • David Valls-Gabaud, Observatoire de Paris
  • Igor D. Karachentsev, Russian Academy of Sciences
  • Taylor S. Chonis, University of Texas at Austin
  • Eva K. Grebel, Universität Heidelberg
  • Duncan A. Forbes, Swinburne University of Technology
  • Aaron J. Romanowsky, San Jose State University
  • J. Gallego-Laborda, Fosca Nit Observatory
  • Karel Teuwen, Remote Observatories Southern Alpes
  • M. A. Gómez-Flechoso, Universidad Complutense de Madrid
  • Jie Wang, Chinese Academy of Sciences
  • Puragra Guhathakurta, University of California Observatories
  • Serafim Kaisin, Russian Academy of Sciences
  • Nhung Ho, Yale University
We report the discovery of DGSAT I, an ultra-diffuse, quenched galaxy located 10fdg4 in projection from the Andromeda galaxy (M31). This low-surface brightness galaxy (μV = 24.8 mag arcsec−2), found with a small amateur telescope, appears unresolved in sub-arcsecond archival Subaru/Suprime-Cam images, and hence has been missed by optical surveys relying on resolved star counts, in spite of its relatively large effective radius (Re(V) = 12'') and proximity (15') to the well-known dwarf spheroidal galaxy And II. Its red color (V − I = 1.0), shallow Sérsic index (nV = 0.68), and the absence of detectable Hα emission are typical properties of dwarf spheroidal galaxies and suggest that it is mainly composed of old stars. Initially interpreted as an interesting case of an isolated dwarf spheroidal galaxy in the local universe, our radial velocity measurement obtained with the BTA 6 m telescope (Vh = 5450 ± 40 km s−1) shows that this system is an M31-background galaxy associated with the filament of the Pisces-Perseus supercluster. At the distance of this cluster (~78 Mpc), DGSAT I would have an Re ~ 4.7 kpc and MV ~ −16.3. Its properties resemble those of the ultra-diffuse galaxies (UDGs) recently discovered in the Coma cluster. DGSAT I is the first case of these rare UDGs found in this galaxy cluster. Unlike the UDGs associated with the Coma and Virgo clusters, DGSAT I is found in a much lower density environment, which provides a fresh constraint on the formation mechanisms for this intriguing class of galaxy.
  • galaxies: clusters: general,
  • galaxies: evolution,
  • galaxies: formation,
  • galaxies: photometry
Publication Date
March 24, 2016
Publisher Statement
This article was originally published in The Astronomical Journal, volume 151, issue 96. © 2016. The American Astronomical Society. All rights reserved.

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Citation Information
David Martínez-Delgado, Ronald Läsker, Margarita Sharina, Elisa Toloba, et al.. "Discovery of an Ultra-Diffuse Galaxy in the Pisces-Perseus Supercluster" The Astronomical Journal Vol. 151 Iss. 4 (2016) ISSN: 1538-3881
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