DISCOVERY OF AN ULTRA-DIFFUSE GALAXY IN THE PISCES-PERSEUS SUPERCLUSTER

Journal Article · Fri Apr 15 00:00:00 EDT 2016 · Astronomical Journal (Online)

DOI:https://doi.org/10.3847/0004-6256/151/4/96· OSTI ID:22519972

Martínez-Delgado, David; Grebel, Eva K. ^[1]; Läsker, Ronald ^[2]; Sharina, Margarita; Karachentsev, Igor D. ^[3]; Toloba, Elisa; Romanowsky, Aaron J. ^[4]; Fliri, Jürgen ^[5]; Beaton, Rachael ^[6]; Valls-Gabaud, David ^[7]; Chonis, Taylor S. ^[8]; Forbes, Duncan A. ^[9]; Gallego-Laborda, J. ^[10]; Teuwen, Karel ^[11]; Gómez-Flechoso, M. A. ^[12]; others, and

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1. Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12–14, D-69120 Heidelberg (Germany)
2. Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany)
3. Special Astrophysical Observatory, Russian Academy of Sciences (Russian Federation)
4. University of California Observatories, 1156 High Street, Santa Cruz, CA 95064 (United States)
5. Instituto de Astrofísica de Canarias, Vía Láctea s/n, E-38200 La Laguna, Tenerife (Spain)
6. The Observatories of the Carnegie Institutions for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
7. LERMA, CNRS UMR 8112, Observatoire de Paris, 61 Avenue de l’Observatoire, F-75014 Paris (France)
8. Department of Astronomy, University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712 (United States)
9. Center for Astrophysics and Supercomputing, Swinburne University, Hawthorn VIC 3122 (Australia)
10. Fosca Nit Observatory, Montsec Astronomical Park, Ager (Spain)
11. Remote Observatories Southern Alpes, Verclause (France)
12. Departamento de Matemática Aplicada (Biomatemática), Universidad Complutense de Madrid, E-28040 Madrid (Spain)

We report the discovery of DGSAT I, an ultra-diffuse, quenched galaxy located 10.°4 in projection from the Andromeda galaxy (M31). This low-surface brightness galaxy (μ{sub V} = 24.8 mag arcsec{sup −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 (R{sub e}(V) = 12″) and proximity (15′) to the well-known dwarf spheroidal galaxy And II. Its red color (V − I = 1.0), shallow Sérsic index (n{sub V} = 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 (V{sub h} = 5450 ± 40 km s{sup −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 R{sub e} ∼ 4.7 kpc and M{sub V} ∼ −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.

• OSTI ID: 22519972
• Journal Information: Astronomical Journal (Online), Vol. 151, Issue 4; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
BRIGHTNESS
GALACTIC EVOLUTION
GALAXIES
GALAXY CLUSTERS
LIMITING VALUES
PHOTOMETRY
RADIAL VELOCITY
STARS
SURFACES
TELESCOPES
UNIVERSE