Astronomy and Astrophysics – Astrophysics – Galaxy Astrophysics
Scientific paper
2011-05-21
Astronomy and Astrophysics
Astrophysics
Galaxy Astrophysics
10 pages, 10 figures; MNRAS accepted. Revised to reflect final version
Scientific paper
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 u-v plane) in small spatial regions, such as the solar neighbourhood. As the disc relaxes after the event, clumps in the u-v 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 in-fall 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.
Gómez Facundo A.
Minchev Ivan
O'Shea Brian W.
Villalobos Álvaro
Williams Mary E. K.
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