Gas and stellar dynamics in Stephan’s Quintet

Mapping the kinematics in a closely interacting compact galaxy group^⋆

¹ Max-Planck Institut für Radioastronomie (MPIfR), Auf dem Hügel 69, 53121 Bonn, Germany
² I.Physikalisches Institut, Universität zu Köln, Zülpicherstrasse 77, 50939 Köln, Germany
e-mail: yttergren@ph1.uni-koeln.de
³ Regionales Rechenzentrum (RRZK), Universität zu Köln, Weyertal 121, 50931 Köln, Germany
⁴ Department of Space, Earth and Environment, Chalmers University of Technology, 412 96, Gothenburg, Sweden

Received: 21 December 2020
Accepted: 8 September 2021

Abstract

In nearby compact galaxy groups we can study the complex processes of galaxy interactions at high resolution and obtain a window into a time in the history of the Universe when the galaxies were closely spaced and the intergalactic medium was awash with gas. Stephan’s Quintet is a nearby compact galaxy group and a perfect laboratory for studying the process of galaxy evolution through galaxy harassment and interaction. By analysing the kinematics of Stephan’s Quintet we aim to provide an increased understanding of the group, the history of the interactions, their cause and effect, and the details regarding the physical processes occurring as galaxies interact. Ionised gas and stellar kinematics have been studied using data from the Large Binocular Telescope, while the molecular gas kinematics have been obtained from CO observations using the IRAM 30m telescope. Large areas of the group have been mapped and analysed. We obtain a total ionised gas mass in the regions chosen for closer analysis of 20.1 ± 0.2 ⋅ 10¹⁰ M_⊙ and a total H₂ gas mass of 21 ± 2 ⋅ 10⁹ M_⊙ in the observed area (spectra integrated over the velocity range covering Stephan’s Quintet), while the star-forming clouds show an impressive complexity, with gas congregations at multiple velocities at many locations throughout the group. We map the large-scale nuclear wind in NGC7319 and its decoupled gas and stellar disk. With our high resolution data we can, for the first time, reveal the Seyfert 1 nature of NGC7319 and fit the narrow-line region and broad-line region of the Hα line. While the ¹²CO (1 − 0) map shows significant emission in the area in or near NGC7319, the bridge, and the star-forming ridge, the ¹²CO (2 − 1) emission shows a prevalence to the star-forming ridge, an area south of the NGC7318 pair, and shows an extension towards NGC7317 – connecting NGC7317 to the centre of the group, indicating a previous interaction. NGC7317 may also be a prime candidate for studies of the process of galaxy harassment. Furthermore, we connect the kinematical structures in Stephan’s Quintet to the history of the group and the ongoing interaction with NGC7318B. Through our extensive observations of Stephan’s Quintet we trace and present the kinematics and evolution of the complex processes and structures occurring in this nearby interactive group.