Letter to the Editor

Low-power jet–interstellar medium interaction in NGC 7319 revealed by JWST/MIRI MRS

¹ Centro de Astrobiología (CSIC-INTA), Ctra de Torrejón a Ajalvir, km 4, 28850 Torrejón de Ardoz, Madrid, Spain
² Observatorio Astronómico Nacional (OAN-IGN)-Observatorio de Madrid, Alfonso XII, 3, 28014 Madrid, Spain
e-mail: miguel.pereira@oan.es
³ Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH, UK
⁴ Telespazio UK for the European Space Agency, ESAC, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Spain
⁵ Centro de Astrobiología (CSIC-INTA), ESAC Campus, 28692 Villanueva de la Cañada, Madrid, Spain
⁶ Departamento de Física de la Tierra y Astrofísica, Fac. de CC Físicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
⁷ Instituto de Física de Partículas y del Cosmos IPARCOS, Fac. CC Físicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
⁸ Department of Physics & Astronomy, University of Southampton, Hampshire, SO17 1BJ Southampton, UK
⁹ Instituto de Astrofísica de Canarias, Calle Vía Láctea, s/n, 38205 La Laguna, Tenerife, Spain
¹⁰ Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
¹¹ School of Mathematics, Statistics and Physics, Newcastle University, NE1 7RU Newcastle upon Tyne, UK

Received: 9 August 2022
Accepted: 13 September 2022

Abstract

We present JWST/MIRI MRS spectroscopy of NGC 7319, the largest galaxy in the Stephan’s Quintet, observed as part of the Early Release Observations (ERO). NGC 7319 hosts a type 2 active galactic nucleus (AGN) and a low-power radio jet (L_1.4 GHz = 3.3 × 10²² W Hz⁻¹) with two asymmetric radio hotspots at 430 pc (N2) and 1.5 kpc (S2) projected distances from the unresolved radio core. The MRS data suggest that the molecular material in the disk of the galaxy decelerates the jet and causes this length asymmetry. We find enhanced emission from warm and hot H₂ (T_w = 330 ± 40 K, T_h = 900 ± 60 K) and ionized gas at the intersection between the jet axis and dust lanes in the disk. This emission is coincident with the radio hotspot N2, the hotspot closer to the core, suggesting that the jet–interstellar medium (ISM) interaction decelerates the jet. Conversely, the mid-infrared emission at the more distant hotspot is fainter, more highly ionized, and with lower H₂ excitation, suggesting a more diffuse atomic environment where the jet can progress to farther distances. At the N2 radio hotspot, the ionized gas mass (M_ion = (2.4–12)×10⁵ M_⊙) is comparable to that of the warm H₂, but the former is more turbulent (σ_ion ∼ 300 vs. σ_H2 ∼ 150 km s⁻¹), so the mechanical energy of the ionized gas is ∼1.3–10 times higher. From these estimates, we find that only < 1% of the jet energy remains as mechanical energy in these two ISM phases at N2. We also find extended (r >  0.3–1.5 kpc) high-ionization emission ([Mg V], [Ne VI], and [Ne V]) close to the radio hotspots. This initial analysis of NGC 7319 shows the potential of MIRI/MRS to investigate the AGN feedback mechanisms due to radio jets and their radiation field in the, often heavily dust-enshrouded, central regions of galaxies. Understanding these mechanisms is an essential ingredient in the development of cosmological simulations of galaxy evolution.