Rotation curve bifurcations as indicators of close recent galaxy encounters

¹ Consejo Nacional de Investigaciones Científicas y Técnicas, CONICET, Argentina e-mail: supe@iafe.uba.ar
² Instituto de Astronomía y Física del Espacio, Casilla de Correos 67, Suc. 28, 1428 Buenos Aires, Argentina e-mail: patricia@iafe.uba.ar
³ GEPI, Observatoire de Paris, CNRS, Université Paris Diderot, Place Jules Janssen, 92190 Meudon, France e-mail: isaura.fuentes@obspm.fr
⁴ Universidade de São Paulo, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Departamento de Astronomia, Rua do Matão 1226, Cidade Universitária 05508-900 São Paulo SP, Brazil e-mail: oliveira@astro.iag.usp.br

Received: 19 July 2007
Accepted: 31 March 2008

Abstract

Context. Rotation curves of interacting galaxies often show that velocities are either rising or falling in the direction of the companion galaxy.

Aims. We seek to reproduce and analyse these features in the rotation curves of simulated equal-mass galaxies suffering a one-to-one encounter as possible indicators of close encounters.

Methods. Using simulations of major mergers in 3D, we study the time evolution of these asymmetries in a pair of galaxies during the first passage.

Results. Our main results are: (a) the rotation curve asymmetries appear right at pericentre of the first passage, (b) the significant disturbed rotation velocities occur within a small time interval, of , and, therefore, the presence of bifurcation in the velocity curve could be used as an indicator of the pericentre occurrence. These results are in qualitative agreement with previous findings for minor mergers and flybys.