A new catalogue of polar-ring galaxies selected from the SDSS

TL;DR

This paper introduces a new catalogue of polar-ring galaxy candidates from SDSS data, significantly expanding the known sample and providing a basis for future detailed and statistical studies of these unique galaxies.

Contribution

The authors present a new, large catalogue of polar-ring galaxy candidates derived from Galaxy Zoo classifications and SDSS imaging, including spectroscopic confirmation of several objects.

Findings

Confirmed polar rings in five galaxies through spectroscopy

Catalogue includes 70 high-confidence PRG candidates

Identified face-on polar ring candidates

Abstract

(Abridged) Galaxies with polar rings (PRGs) are a unique class of extragalactic objects allowing to investigate a wide range of problems, linked with the formation and evolution of galaxies, and to study the properties of their dark haloes. The progress in the study of PRGs is constrained by a small number of known objects of this type. Up to date, we can only attribute about two dozens of kinematically-confirmed galaxies to this class, mostly from Whitmore et al. (1990) catalogue. We present a new catalogue of PRGs based on the results of the original Galaxy Zoo project. Based on the preliminary classification of the Galaxy Zoo, we viewed more than 40000 images of the Sloan Digital Sky Survey (SDSS) and selected 275 galaxies, included in our catalogue. Our Sloan-based Polar Ring Catalog (SPRC) contains 70 galaxies that we classified as "the best candidates", among which we expect to have a very high proportion of true PRGs, and 115 good PRG candidates. 53 galaxies are classified as PRG related objects.We identified 37 galaxies that have their presumed polar rings seen almost face-on. The SPRC objects are on the average fainter and located further away than the galaxies from the catalog by Whitmore et al., although our catalogue does include dozens of new nearby candidate PRGs. The new catalogue significantly increases the number of genuine PRG candidates, and may serve as a good basis both for the further detailed study of individual galaxies, and for the statistical analysis of PRGs as a separate class of objects. We performed spectroscopic observations of six galaxies from the SPRC at the 6-m telescope. The existence of polar rings was confirmed in five galaxies, and one object appeared to be a projection of a pair of galaxies. Adding the literature data, we can already classify 10 galaxies from our catalogue to the kinematically-confirmed PRGs.