Issue |
A&A
Volume 567, July 2014
|
|
---|---|---|
Article Number | A17 | |
Number of page(s) | 11 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/201423656 | |
Published online | 04 July 2014 |
Long-time evolution of gas-free disk galaxies in binary systems
1
Coordenação de Astronomia e Astrofísica, Observatório
Nacional, Rua General José Cristino
77, São Cristóvão, CEP
20921–400
Rio de Janeiro
RJ
Brazil
e-mail: chan@on.br
2
Divisão Serviço da Hora, Observatório Nacional,
Rua General José Cristino 77, São
Cristóvão, CEP
20921–400
Rio de Janeiro, RJ, Brazil
e-mail: selma@on.br
Received:
17
February
2014
Accepted:
13
May
2014
We present the results of several detailed numerical N-body simulations of the dynamical interactions of two equal-mass disk galaxies. Both galaxies are embedded in spherical halos of dark matter and contain central bulges. Our analysis of the dynamical evolution of the binary system focuses on the morphological evolution of the stellar distribution of the disks. The satellite galaxy has coplanar or polar disk orientation in relation to the disk of the primary galaxy and their initial orbits are prograde eccentric (e = 0.1, e = 0.4 or e = 0.7). Both galaxies have mass and size similar to the Milky Way. We show that the merger of the two disk galaxies, depending on the relative orientation of the disks, can yield either a disk or lenticular remnant, instead of an elliptical one. These are the first reported simulations that show the formation of S0-like galaxies from protracted binary galaxy interactions. Additionally, we demonstrate that the time to merger increases linearly with the initial apocentric distance between the galaxies, and decreases with the initial orbital eccentricity. We also show that the tidal forces of the disks excite transient m = 1 and m = 2 wave modes, that is, lopsidedness, spiral arms, and bars. However, after the merging of the disks, these larger instabilities fade completely, and the remnant is thicker and more extended than the original disks. The maximum relative amplitude of these waves is at most about 15 times higher than the control case. The m = 2 wave mode is generated mainly by tidal interaction in the outer region of the disks. The m = 1 wave mode depends mostly on the interaction of the inner part of the disks, producing an off-centering effect of the wave mode center relative to the center of mass of the disk. These characteristics produce a time lag among the maximum formation of these two wave modes. Finally, the disk settles down quickly after the merger, in less than one outer disk rotation period.
Key words: galaxies: spiral / galaxies: evolution / galaxies: interactions / galaxies: kinematics and dynamics / galaxies: structure
© ESO, 2014
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