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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 358777.0, MPI für Astronomie / Publikationen_mpia
The elongated structure of the Hercules Dwarf Spheroidal Galaxy from deep Large Binocular Telescope imaging
Authors:Coleman, M. G.; de Jong, J. T. A.; Martin, N. F.; Rix, H.-W.; Sand, D. J.; Bell, E. F.; Pogge, R. W.; Thompson, D. J.; Hippelein, H.; Giallongo, E.; Ragazzoni, R.; DiPaola, A.; Farinato, J.; Smareglia, R.; Testa, V.; Bechtold, J.; Hill, J. M.; Garnavich, P. M.; Green, R. F.
Date of Publication (YYYY-MM-DD):2007
Title of Journal:The Astrophysical Journal
Start Page:L43
End Page:L46
Audience:Not Specified
Abstract / Description:We present a deep, wide-field photometric survey of the newly discovered Hercules dwarf spheroidal galaxy (dSph), based on data from the Large Binocular Telescope. Images in B, V, and r were obtained with the Large Binocular Camera covering a 23'×23' field of view to a magnitude of ~25.5 (5 sigma). This permitted the construction of color-magnitude diagrams that reach approximately 1.5 mag below the Hercules main-sequence turnoff. Three-filter photometry allowed us to preferentially select probable Hercules member stars and to examine the structure of this system at a previously unattained level. We find that the Hercules dwarf is highly elongated (3:1), considerably more so than any other dSph satellite of the Milky Way, except the disrupting Sagittarius dwarf. Although we cannot rule out that the unusual structure is intrinsic to Hercules as an equilibrium system, our results suggest tidal disruption as a likely cause of this highly elliptical structure. Given the relatively large galactocentric distance of this system (132+/-12 kpc), signs of tidal disruption would require the Hercules dwarf to be on a highly eccentric orbit around the Milky Way. Based on data acquired using the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the US, Italy, and Germany. LBT Corporation partners are the University of Arizona, on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; Ohio State University; and the Research Corporation, on behalf of the University of Notre Dame, the University of Minnesota, and the University of Virginia.
Free Keywords:galaxies: individual (Hercules dwarf spheroidal galaxy); Galaxies: Kinematics and Dynamics
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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