Double, double, toil, and trouble: The tails, bubbles, and knots of the local compact obscured nucleus galaxy NGC 4418
Journal article, 2024
Context. Compact obscured nuclei (CONs) are an extremely obscured (NH2>1025 cm-2) class of galaxy nuclei thought to exist in 20-40 per cent of nearby (ultra-)luminous infrared galaxies While they have been proposed to represent a key phase of the active galactic nucleus (AGN) feedback cycle, the nature of these CONs -what powers them, their dynamics, and their impact on the host galaxy -remains unknown. Aims. This work analyses the galaxy-scale optical properties of the local CON NGC 4418 (z=0.00727). The key aims of the study are to understand the impact of nuclear outflows on the host galaxy and infer the power source of its CON. Through the mapping of the galaxy spectra and kinematics, we seek to identify new structures in NGC 4418 to ultimately reveal more about the CON's history, its impact on the host, and, more generally, the role CONs play in galaxy evolution. Methods. We present new, targeted integral field unit observations of the galaxy with the Multi-Unit Spectroscopic Explorer (MUSE). For the first time, we mapped the ionised and neutral gas components of the galaxy, along with their dynamical structure, to reveal several previously unknown features of the galaxy. Results. We confirm the presence of a previously postulated, blueshifted outflow along the minor axis of NGC 4418. We find this outflow to be decelerating and, for the first time, show it to extend in both directions from the nucleus. We report the discovery of two further outflow structures: a redshifted southern outflow connected to a tail of ionised gas surrounding the galaxy and a blueshifted bubble to the north. In addition to these features, we find the [OIII] emission reveals the presence of knots across the galaxy, which are consistent with regions of the galaxy that have been photoionised by an AGN. Conclusions. We identify several new features in NGC 4418, including a bubble structure, a reddened outflow, and [OIII] knot structures throughout the galaxy. We additionally confirm the presence of a bilateral blueshifted outflow along the minor axis. Based on the properties of these features, we conclude that the CON in NGC 4418 is most likely powered by AGN activity.
Galaxies: nuclei
Galaxies: active
Galaxies: evolution
Author
Clare Wethers
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Susanne Aalto
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
G. Privon
University of Virginia
University of Florida
National Radio Astronomy Observatory
F. Stanley
Institut de Radioastronomie Millimétrique (IRAM)
J. S. Gallagher III
University of Wisconsin Madison
Mark Gorski
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Sabine König
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Kyoko Onishi
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Mamiko Sato
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Chentao Yang
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
R. J. Beswick
University of Manchester
Loreto Barcos-Munoz
University of Virginia
F. Combes
Paris Observatory
T. Diaz-Santos
Foundation for Research and Technology-Hellas (FORTH)
A. S. Evans
University of Virginia
National Radio Astronomy Observatory
I. García-Bernete
University of Oxford
C. Henkel
King Abdulaziz University
Max Planck Society
M. Imanishi
National Astronomical Observatory of Japan
S. Martin
Atacama Large Millimeter-submillimeter Array (ALMA)
European Southern Observatory Santiago
Sebastien Muller
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Y. Nishimura
University of Tokyo
C. Ricci
Diego Portales University
Beijing University of Technology
D. Rigopoulou
National Radio Astronomy Observatory
Serena Viti
Leiden University
University College London (UCL)
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 683 A27Exploring the Hidden Dusty Nuclei of Galaxies (HIDDeN)
European Research Council (ERC) (789410), 2018-10-01 -- 2023-09-30.
Subject Categories
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
DOI
10.1051/0004-6361/202347207