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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 358782.0, MPI für Astronomie / Publikationen_mpia
Strangers in the night: discovery of a dwarf spheroidal galaxy on its first Local Group infall
Authors:Chapman, S. C.; Peñarrubia, J.; Ibata, R.; McConnachie, A.; Martin, N.; Irwin, M.; Blain, A.; Lewis, G. F.; Letarte, B.; Lo, K.; Ludlow, A.; O'Neil, K.
Date of Publication (YYYY-MM-DD):2007
Title of Journal:The Astrophysical Journal
Start Page:L79
End Page:L82
Audience:Not Specified
Abstract / Description:We present spectroscopic observations of the And XII dwarf spheroidal galaxy using DEIMOS/Keck II, showing it to be moving rapidly through the Local Group (-556 km s-1 heliocentric velocity, -281 km s-1 relative to Andromeda), falling into the Local Group from ~115 kpc beyond Andromeda's nucleus. And XII therefore represents a dwarf galaxy plausibly falling into the Local Group for the first time and never having experienced a dense galactic environment. From Green Bank Telescope observations, a limit on the H I gas mass of <3×103 Msolar suggests that And XII's gas could have been removed prior to experiencing the tides of the Local Group galaxies. Orbit models suggest that the dwarf is close to the escape velocity of M31 for published mass models. And XII is our best direct evidence for the late infall of satellite galaxies, a prediction of cosmological simulations.
Free Keywords:Galaxies: Evolution; galaxies: individual (Andromeda) -Galaxies: Spiral; Galaxies: Local Group
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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