Tracing kinematic (mis)alignments in CALIFA merging galaxies

Stellar and ionized gas kinematic orientations at every merger stage^⋆

¹ Instituto de Astrofísica de Canarias (IAC), 38205 La Laguna, Tenerife, Spain
e-mail: jkbb@iac.es
² Depto. Astrofísica, Universidad de La Laguna (ULL), 38206, La Laguna, Tenerife, Spain
³ Max-Planck-Institut für Astronomie, 69117 Heidelberg, Germany
⁴ Kapteyn Astronomical Institute, University of Groningnen, Landleven 12, 9747 AD Groningen, The Netherlands
⁵ School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, KY16 9SS, UK
⁶ Instituto de Astronomía, Universidad Nacional Autonóma de Mexico, A.P. 70-264, 04510 México, D.F., Mexico
⁷ Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía s/n, Aptdo. 3004, 18080 Granada, Spain
⁸ Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
⁹ GEPI Observatoire de Paris, CNRS, Université Paris Diderot, Place Jules Janssen, 92190 Meudon, France
¹⁰ University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
¹¹ European Southern Observatory (ESO), Karl-Schwarzschild-Str. 2, 85748 Garching b. Muenchen, Germany
¹² Instituto de Cosmologia, Relatividade e Astrofísica ICRA, Centro Brasileiro de Pesquisas Físicas, Rua Dr.Xavier Sigaud 150, CEP 22290-180 Rio de Janeiro, RJ, Brazil
¹³ Estación Experimental de Zonas Aridas (CSIC), Ctra. de Sacramento s/n, La Cañada, Almería, Spain
¹⁴ CEI Campus Moncloa, UCM-UPM, Departamento de Astrofísica y CC. de la Atmósfera, Facultad de CC. Físicas, Universidad Complutense de Madrid, Avda. Complutense s/n, 28040 Madrid, Spain
¹⁵ Astronomical Institute of the Ruhr-University Bochum, Universitätsstr. 150, 44580 Bochum, Germany
¹⁶ RUB Research Department “Plasmas with Complex Interactions”, Universitätsstr. 150, 44580 Bochum, Germany
¹⁷ Sydney Institute for Astronomy, School of Physics A28, University of Sydney, NSW 2006, Australia
¹⁸ Department of Physics & Astronomy, University of Missouri-Kansas City, 5110 Rockhill Road, Kansas City, MO, USA

Received: 6 September 2014
Accepted: 15 May 2015

Abstract

We present spatially resolved stellar and/or ionized gas kinematic properties for a sample of 103 interacting galaxies, tracing all merger stages: close companions, pairs with morphological signatures of interaction, and coalesced merger remnants. In order to distinguish kinematic properties caused by a merger event from those driven by internal processes, we compare our galaxies with a control sample of 80 non-interacting galaxies. We measure for both the stellar and the ionized gas components the major (projected) kinematic position angles (PA_kin, approaching and receding) directly from the velocity distributions with no assumptions on the internal motions. This method also allow us to derive the deviations of the kinematic PAs from a straight line (δPA_kin). We find that around half of the interacting objects show morpho-kinematic PA misalignments that cannot be found in the control sample. In particular, we observe those misalignments in galaxies with morphological signatures of interaction. On the other hand, thelevel of alignment between the approaching and receding sides for both samples is similar, with most of the galaxies displaying small misalignments. Radial deviations of the kinematic PA orientation from a straight line in the stellar component measured by δPA_kin are large for both samples. However, for a large fraction of interacting galaxies the ionized gas δPA_kin is larger than the typical values derived from isolated galaxies (48%), indicating that this parameter is a good indicator to trace the impact of interaction and mergers in the internal motions of galaxies. By comparing the stellar and ionized gas kinematic PA, we find that 42% (28/66) of the interacting galaxies have misalignments larger than 16°, compared to 10% from the control sample. Our results show the impact of interactions in the motion of stellar and ionized gas as well as the wide the variety of their spatially resolved kinematic distributions. This study also provides a local Universe benchmark for kinematic studies in merging galaxies at high redshift.