Star formation in a massive spiral galaxy with a radio-AGN

¹ Université de la Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Bd de l’Observatoire, CS 34229, 06304 Nice cedex 4, France
e-mail: marie.drevet-mulard@oca.eu
² Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Pune 411007, India
³ University of Tsukuba, Center for Computational Sciences, Tennodai 1-1-1, 305-0006 Tsukuba, Ibaraki, Japan
⁴ Research School of Astronomy and Astrophysics, The Australian National University, Canberra, ACT 2611, Australia
⁵ Max-Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁶ Observatoire de Paris, LERMA, Collège de France, CNRS, PSL University, Sorbonne University, Paris, France
⁷ Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109, USA
⁸ Department of Astronomy, California Institute of Technology, 1216 E California Blvd., Pasadena, CA 91125, USA
⁹ Department of Physics & Electronics, CHRIST (Deemed to be University), Hosur Road, Bengaluru 560029, India

Received: 10 October 2022
Accepted: 17 February 2023

Abstract

We present an analysis of new VLT/MUSE optical imaging spectroscopic data of 2MASX J23453268–0449256 (J2345–0449), a nearby (z = 0.0755) massive (M_stellar  =  4 ×  10¹¹ M_⊙) spiral galaxy. This is a particularly interesting source for a study of active galactic nucleus (AGN) feedback since it hosts two pairs of bright, giant radio jets and a massive, luminous X-ray halo, but it has no massive bulge. The galaxy has a 24 kpc wide ring of molecular gas, and a source-averaged star formation rate that is factors 30 to 70 lower than expected from the Kennicutt-Schmidt law. With MUSE, we have analyzed the stellar continuum and bright optical line emission and have constrained the spatially resolved past and present star formation on scales of approximately 1 kpc. More than 93% of the stellar mass formed ≥10 Gyrs ago including in the disk. Optical emission from the AGN is very faint and contributes 2% of the continuum around the nucleus at most. Most line emission is predominantly excited by shocks and old stellar populations except in 13 young star-forming regions that formed ≤11 Myrs ago, of which only seven are associated with the molecular ring (the others are at larger radii). They avoid a region of high electron densities aligned with the radio source, and form stars at efficiencies that are comparable to those in normal spiral galaxies. We discuss the implications of our findings for the regulation of star formation in galaxies through AGN feedback in the absence of competing mechanisms related to the presence of a massive stellar bulge, such as morphological quenching.