Effects of galaxy–satellite interactions on bar formation

¹ Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstr. 12-14, 69120 Heidelberg, Germany
e-mail: just@ari.uni-heidelberg.de
² Institute of Astronomy, Russian Academy of Sciences, 48 Pyatnitskya St., 119017 Moscow, Russia
³ Main Astronomical Observatory, National Academy of Sciences of Ukraine, MAO/NASU, 27 Akad. Zabolotnoho St. 03680 Kyiv, Ukraine
⁴ National Astronomical Observatories and Key Laboratory of Computational Astrophysics, Chinese Academy of Sciences, NAOC/CAS, 20A Datun Rd., Chaoyang District, Beijing 100012, PR China

Received: 7 November 2016
Accepted: 9 March 2017

Abstract

Aims. We aim to show how encounters with low-mass satellite galaxies may alter the bar formation in a Milky Way-like disc galaxy.

Methods. We use high-resolution N-body simulations of a disc galaxy prone to mild bar instability. For realistic initial conditions of satellites, we take advantage of cosmological simulations of Milky Way-like dark matter haloes.

Results. The satellites may have a significant impact on the time of bar formation. Some runs with satellites demonstrate a delay, while others show an advancement in bar formation compared to the isolated run, with such time differences reaching ~1 Gyr. Meanwhile, the final bar configuration, including its very appearance and the bar characteristics such as the pattern speed and the exponential growth rate of its amplitude are independent of the number of encounters and their orbits. The contribution of satellites with masses below 10⁹M_⊙ is insignificant, unless their pericentre distances are small. We suggest that the encounters act indirectly via inducing perturbations across the disc that evolve to delayed waves in the central part and interfere with an emerging seed bar. The predicted effect for the present-day host galaxy is expected to be even more significant at redshifts z ≳ 0.5.