Kinematics and simulations of the stellar stream in the halo of the Umbrella Galaxy

Foster, C. and Lux, H. and Romanowsky, A.J. and Martínez-Delgado, D. and Zibetti, S. and Arnold, J.A. and Brodie, J.P. and Ciardullo, R. and GaBany, R.J. and Merrifield, Michael R. and Singh, N. and Strader, J. (2014) Kinematics and simulations of the stellar stream in the halo of the Umbrella Galaxy. Monthly Notices of the Royal Astronomical Society, 442 (4). pp. 3544-3564. ISSN 1365-2966

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We study the dynamics of faint stellar substructures around the Umbrella Galaxy, NGC 4651, which hosts a dramatic system of streams and shells formed through the tidal disruption of a nucleated dwarf elliptical galaxy. We elucidate the basic characteristics of the system (colours, luminosities, stellar masses) using multiband Subaru/Suprime-Cam images. The implied stellar mass ratio of the ongoing merger event is ∼1:50. We identify candidate kinematic tracers (globular clusters, planetary nebulae, H ii regions) and follow up a subset with Keck/DEIMOS (DEep Imaging Multi-object Spectrograph) spectroscopy to obtain velocities. We find that 15 of the tracers are likely associated with halo substructures, including the probable stream progenitor nucleus. These objects delineate a kinematically cold feature in position–velocity phase space. We model the stream using single test particle orbits, plus a rescaled pre-existing N-body simulation. We infer a very eccentric orbit with a period of ∼0.35 Gyr and turning points at ∼2–4 and ∼40 kpc, implying a recent passage of the satellite through the disc, which may have provoked the visible disturbances in the host galaxy. This work confirms that the kinematics of low surface brightness substructures can be recovered and modelled using discrete tracers – a breakthrough that opens up a fresh avenue for unravelling the detailed physics of minor merging.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2014 Royal Astronomical Society Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Keywords: Galaxies Individual, NGC 4651, Galaxies Interactions, Galaxies kinematics and dynamics
Schools/Departments: University of Nottingham UK Campus > Faculty of Science > School of Physics and Astronomy
Identification Number:
Depositing User: Merrifield, Michael
Date Deposited: 09 Sep 2016 08:15
Last Modified: 22 Oct 2016 14:24

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