Radio Galaxy Zoo Talk

The Abundance of X-Shaped Radio Sources I. VLA Survey of 52 Sources With Off-Axis Distortions

  • JeanTate by JeanTate

    Roberts+ (2015), arXiv:1503.02017:

    Cheung (2007) identified a sample of 100 candidate X-shaped radio galaxies using the NRAO FIRST survey; these are small-axial-ratio extended radio sources with off-axis emission. Here we present radio images of 52 of these sources that have been made from archival Very Large Array data with resolution of about 1 arcsec. Fifty-one of the 52 were observed at 1.4 GHz, seven were observed at 1.4 GHz and 5 GHz, and one was observed only at 5 GHz. We also present overlays of the SDSS red images for 41 of the sources, and DSS II overlays for the remainder. Optical counterparts have been identified for most sources, but there remain a few empty fields.
    Our higher resolution VLA images along with FIRST survey images of the sources in the sample reveal that extended extragalactic radio sources with small axial ratios are largely (60%) cases of double radio sources with twin lobes that have off-axis extensions, usually with inversion-symmetric structure. The available radio images indicate that at most 20% sources might be genuine X-shaped radio sources that could have formed by a restarting of beams in a new direction following an interruption and axis flip. The remaining 20% are in neither of these categories. The implications of this result for the gravitational wave background are discussed in Roberts, Saripalli, and Subrahmanyan (2015).

    I wonder how many of these we have come across, here in RGZ?

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  • rad_astronomer by rad_astronomer scientist

    Hi Jean, not sure, although it should be straight forward to compare that catalogue to the sources we've already flagged as X or S shaped in RGZ? I also need to have a look at how they visually classify a confirmed genuine X-shaped source and what they look like in FIRST compared to the ones found in RGZ.

    Posted

  • JeanTate by JeanTate in response to rad_astronomer's comment.

    Hi rad_astronomer,

    It should be fairly straight-forward, 'simply' match the (RA, Dec) for the RGZ objects with the relevant hashtag/in the relevant Collection with the 52 in Roberts+ (2015) (or Cheung 2007's 100). You'd have to set the search radius as big as (angular) size of the largest RGZ object, because it's not clear (to me anyway) what/how you decide the location of an X/S source is, and whether the method(s) is (are) always consistent, and the same as that of Cheung (2007).

    I also need to have a look at how they visually classify a confirmed genuine X-shaped source and what they look like in FIRST compared to the ones found in RGZ.

    Yeah, that occured to me too, when reading Roberts+ (2015); perhaps "X-shaped" is a little like beauty (in the eye of the beholder)? 😛

    Posted