Jet collimation in a spiral-hosted AGN: a parabolic jet profile in 0313-192

TL;DR

This study investigates the jet structure of the spiral-hosted AGN 0313-192, revealing a parabolic-to-conical transition in jet shape that suggests magnetic and ram pressure confinement mechanisms, challenging traditional views on jet formation in disk galaxies.

Contribution

It provides detailed observational evidence of jet collimation in a spiral galaxy AGN, highlighting alternative confinement mechanisms beyond dense ambient gas.

Findings

Jet exhibits a parabolic profile up to 610 pc

Transition from parabolic to conical shape occurs beyond SMBH sphere of influence

Jet collimation may be driven by magnetic and ram pressure, not external gas

Abstract

Double-lobed radio sources associated with active galactic nuclei (DRAGNs) are typically found in elliptical galaxies, while supermassive black holes (SMBHs) in disk galaxies rarely produce powerful kpc-scale jets. However, the growing number of spiral- and disk-hosted DRAGNs challenges this classical dichotomy. We present a study of the jet collimation profile for one such source, 0313-192, using VLBA and VLA data, tracing the jet morphology across nearly five orders of magnitude in scale -- from $\sim$ pc to $\sim100$ kpc (projected). We find that the jet exhibits a parabolic expansion up to $\sim 610$ pc ($\sim 7.9 \times 10^6$ Schwarzschild radii), followed by a transition to a nearly conical shape, assuming kpc-scale emission primarily originates from the jet rather than the lobe. This structural evolution closely resembles those in AGNs hosted by elliptical galaxies and provides an explanation for how the jet in this system could extend to large distances by magnetohydrodynamic collimation and acceleration. However, this collimation break occurs beyond the sphere of gravitational influence of the SMBH ($\sim7.3\times10^{5} R_{S}$), and no extended X-ray halos or dense molecular gas structures are detected to provide the necessary external pressure. Therefore we suggest that jet confinement in 0313-192 is mediated by contributions from non-thermal components, such as ram and magnetic pressure from magnetized disk winds. These mechanisms may enable jet collimation even in the absence of dense ambient gas. Our results highlight how large-scale jets can arise in disk galaxies under rare conditions and demonstrate the need to broaden studies of AGN jet formation beyond traditional models.