Photometry of Polar-Ring Galaxies

TL;DR

This study presents photometric measurements of seven polar-ring galaxies, revealing diverse colors and evidence of recent star formation, with some rings potentially being over a billion years old and stable.

Contribution

First detailed photometric analysis of multiple polar-ring galaxies, providing insights into their ages, star formation activity, and stability.

Findings

Rings exhibit a wide range of B-R colors from 0.6 to 1.7.

Presence of bright HII regions indicates recent star formation.

Some rings, like PRC B-20, are at least 1.2 Gyr old and likely stable.

Abstract

We have obtained photometry in B and R for seven confirmed or probable polar-ring galaxies from the Polar-Ring Catalog of Whitmore et al. (1990). The rings show a range of colors from B-R \approx 0.6 to B-R \approx 1.7. The bluest rings have bright HII regions, which are direct evidence for recent star formation. The minimum age of the reddest ring, that in PRC B-20, is somewhat uncertain because of a lack of knowledge of the internal reddening and metallicity, but appears to be at least 1.2 Gyr. As such, this ring is likely to be stable for at least several rotation periods. This ring is an excellent candidate for future studies that might better determine if it is truly old.