Journal Article

Signatures of minor mergers in Milky Way like disc kinematics: ringing revisited

Facundo A. Gómez, Ivan Minchev, Álvaro Villalobos, Brian W. O’Shea and Mary E. K. Williams

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 419, issue 3, pages 2163-2172
Published in print January 2012 | ISSN: 0035-8711
Published online January 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.19867.x
Signatures of minor mergers in Milky Way like disc kinematics: ringing revisited

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By means of N-body simulations, we study the response of a galactic disc to a minor merger event. We find that non-self-gravitating, spiral-like features are induced in the thick disc. As we have shown in a previous work, this ‘ringing’ also leaves an imprint in velocity space (the uv plane) in small spatial regions, such as the solar neighbourhood. As the disc relaxes after the event, clumps in the uv plane get closer with time, allowing us to estimate the time of impact. In addition to confirming the possibility of this diagnostic, here we show that in a more realistic scenario, the infall trajectory of the perturber gives rise to an azimuthal dependence of the structure in phase space. We also find that the space defined by the energy and angular momentum of stars is a better choice than velocity space, as clumps remain visible even in large local volumes. This makes their observational detection much easier since one need not be restricted to a small spatial volume. We show that information about the time of impact, the mass of the perturber and its trajectory is stored in the kinematics of disc stars.

Keywords: methods: analytical; methods: numerical; galaxies: formation; galaxies: kinematics and dynamics

Journal Article.  6604 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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