Volume 575, March 2015
|Number of page(s)||9|
|Published online||12 February 2015|
Building gas rings and rejuvenating S0 galaxies through minor mergers
INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio
2 Dipartimento di Fisica e Astronomia Galileo Galilei, University of Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
Received: 11 November 2014
Accepted: 19 December 2014
We investigate the effects of minor mergers between an S0 galaxy and a gas-rich satellite galaxy, by means of N-body/smoothed particle hydrodynamics simulations. The satellite galaxy is initially on a nearly parabolic orbit and undergoes several periapsis passages before being completely stripped. In most simulations, a portion of the stripped gas forms a warm dense gas ring in the S0 galaxy, with a radius of ~6–13 kpc and a mass of ~107M⊙. The ring is generally short-lived (≲3 Gyr) if it forms from prograde encounters, while it can live for more than 6 Gyr if it is born from counter-rotating or non-coplanar interactions. The gas ring keeps memory of the initial orbit of the satellite galaxy: it is corotating (counter-rotating) with the stars of the disc of the S0 galaxy, if it originates from prograde (retrograde) satellite orbits. Furthermore, the ring is coplanar with the disc of the S0 galaxy only if the satellite’s orbit was coplanar, while it lies on a plane that is inclined with respect to the disc of the S0 galaxy by the same inclination angle as the orbital plane of the satellite galaxy. The fact that we form polar rings as long-lived and as massive as co-planar rings suggests that rings can form in S0 galaxies even without strong bar resonances. Star formation up to 0.01 M⊙ yr-1 occurs for >6 Gyr in the central parts of the S0 galaxy as a consequence of the interaction. We discuss the implications of our simulations for the rejuvenation of S0 galaxies in the local Universe.
Key words: galaxies: interactions / methods: numerical / galaxies: kinematics and dynamics / galaxies: star formation / galaxies: ISM
© ESO, 2015
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