A candidate polar-ring galaxy in the Subaru Deep Field

TL;DR

This paper reports the discovery and analysis of a candidate polar-ring galaxy in the Subaru Deep Field, revealing a complex structure formed by a recent galaxy merger involving an early-type galaxy and a gas-rich dwarf.

Contribution

It presents the identification and detailed photometric analysis of a new polar-ring galaxy candidate with evidence of ongoing merger activity.

Findings

The galaxy has a >5 Gyr old central early-type core.

The presence of a tilted inner ring at ~25 degrees.

Detection of faint stellar features indicating recent merger activity.

Abstract

We discuss the properties of an object in the Subaru Deep Field (SDF) classified as a galaxy in on-line data bases and revealed on the Subaru images as a genuine polar-ring galaxy (PRG) candidate. We analyse available photometric data and conclude that this object consists of a >5 Gyr old early-type central body surrounded by a faint, narrow inner ring tilted at a ~25 deg angle relative to the polar axis of the host galaxy. The halo surrounding the main stellar body exhibits a diversity of spatially extended stellar features of low surface brightness, including a faint asymmetric stellar cloud and two prominent loops. These faint features, together with the unperturbed morphology of the central host, are clear signs of a recent coalescence of two highly unequal mass galaxies, most likely a pre-existing early-type galaxy and a close-by gas-rich dwarf galaxy. The presumed stellar remnants observed near the edges of the ring, including possibly the surviving captured companion itself, indicate that the merger is still taking place.