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New Polar Ring Galaxies

Russian version

    Galaxies with polar rings (PRGs) are a unique class of extragalactic objects, consisting of a ring or disk of gas, stars and dust orbiting in a plane nearly perpendicular to the disk of a central galaxy. Is is believed that the formation of PRGs is in most cases caused by galaxy mergers with the corresponding direction of angular momentum, the accretion by the host galaxy of the companion's matter, or gas filaments from the intergalactic medium. The progress that has been made in the study of PRGs has been constrained by the small number of known objects of this type. Any definite conclusions about their origin, evolution, characteristics of their dark halos are of limited importance due to absence of enough statistics and of good homogeneous data sets. At present, there are only about two dozen kinematically confirmed galaxies in this PRG class, mostly from the Whitmore et al. (1990) catalogue, based on photographic images.
    We create a new catalogue, significantly increasing the number of known candidate PRGs. The catalog is based on the results of Galaxy Zoo project, under which the volunteers performed a visual classification of nearly a million galaxies from the Sloan Digital Sky Survey (SDSS). Based on the preliminary classifications of the Galaxy Zoo, we viewed more than 40 000 images of the SDSS and selected 275 galaxies to include in our catalogue (Fig.1).
    The first spectral observations of six new candidates at the 6-m telescope with SCORPIO focal reducer confirmed the existence of polar rings in five galaxies (Fig.2), and one object appeared to be a projection of a pair of interacting galaxies.
Moiseev A.V., Smirnova K.I., Smirnova A.A., Reshetnikov V.P.
2011, MNRAS, accepted; arXiv:1107.1966v1 [astro-ph.CO]

Contact - Alexei Moiseev

Fig.1. Examples of object from our catalogue SPRC (=SDSS-based Polar Ring Catalogue). A colour combination of images in g, r, i is provided by the SDSS server.

Fig.2. The contours of SDSS images of the galaxy SPRC-14 (right). The positions of the spectrograph slit are indicated. Left: the distribution of the line-of-sight velocities of gas and stars in the corresponding sections. The dotted line marks the centre of the galaxy and the value of systemic velocity. The thick coloured lines schematically mark the kinematic components, rotating in different planes: blue lines for the central galaxy and yellow lines for the polar ring.