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

Foster, C.; Lux, H.; Romanowsky, A. J.; Mart�nez-Delgado, D.; Zibetti, S.; Arnold, J. A.; Brodie, J. P.; Ciardullo, R.; GaBany, R. J.; Merrifield, Michael R.; Singh, N.; Strader, J.

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


C. Foster

H. Lux

A. J. Romanowsky

D. Mart�nez-Delgado

S. Zibetti

J. A. Arnold

J. P. Brodie

R. Ciardullo

R. J. GaBany

Michael R. Merrifield

N. Singh

J. Strader


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.

Journal Article Type Article
Acceptance Date May 28, 2014
Online Publication Date Jul 2, 2014
Publication Date Aug 21, 2014
Deposit Date Sep 9, 2016
Publicly Available Date Sep 9, 2016
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 442
Issue 4
Pages 3544-3564
Keywords Galaxies Individual, NGC 4651, Galaxies Interactions, Galaxies kinematics and dynamics
Public URL
Publisher URL
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.


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