Serendipitous discovery of a spiral host in a 2 Mpc double-double lobed radio galaxy

TL;DR

This paper reports the discovery of a giant double-double radio galaxy hosted by a spiral galaxy, challenging the common belief that such large radio structures only occur in elliptical galaxies, and demonstrates recurrent jet activity in a disk galaxy.

Contribution

It presents the first detailed analysis of a 2 Mpc double-double radio galaxy with a spiral host, showing that disk galaxies can produce extremely large-scale radio jets.

Findings

Confirmed recurrent jet activity in a spiral galaxy

Established the galaxy as the largest known spiral-host radio galaxy

Identified only three spiral-host DDRGs, including this one

Abstract

We present the serendipitous discovery of a double-double radio galaxy (DDRG) with a projected linear size exceeding 2 Mpc, hosted by a spiral galaxy. This unique combination of a giant radio structure and a spiral host challenges the prevailing view that such extreme radio sources reside only in elliptical galaxies. Using high-resolution optical imaging from the DESI Legacy Imaging Survey (DR10), we confirm a spiral-arm feature and a disk-component in the surface brightness profile fitting for the host galaxy (LEDA 896325) having a black hole of mass 2.4 $\times$ 10$^8$ $\rm M_{\odot}$. Radio observations from RACS and GLEAM reveal two distinct pairs of radio lobes. Using the multi-frequency analysis of radio data, we obtained the spectral index distribution and estimate the spectral ages of the outer and inner radio lobes to be approximately 120 and 35 Myr, respectively. Our results confirm recurrent jet activity in this disk galaxy and establish it as the largest known radio galaxy in a spiral host, and its double-double structure makes it the largest of only three such spiral-host DDRGs, demonstrating that disk galaxies can indeed launch extremely large-scale radio jets.