Title:	What Are "X-Shaped" radio sources telling Us? II. properties of a sample of 87
Authors:	Saripalli, Lakshmi Roberts, David H
Keywords:	radio continuum galaxies
Issue Date:	Jan-2018
Publisher:	IOP Sciences for The American Astronomical Society
Citation:	Astrophysical Journal, 2018, Vol. 852, p48
Abstract:	In an earlier paper, we presented Jansky Very Large Array multi-frequency, multi-array continuum imaging of a unique sample of low-axial ratio radio galaxies. In this paper, the second in the series, we examine the images to learn the phenomenology of how the off-axis emission relates to the main radio source. Inversion-symmetric offset emission appears to be bimodal and to originate from one of two strategic locations: outer ends of radio lobes (outer-deviation) or from inner ends (inner-deviation). The latter sources are almost always associated with edge-brightened sources. With S- and Z-shaped sources being a subset of outer-deviation sources, this class lends itself naturally to explanations involving black hole axis precession. Our data allow us to present a plausible model for the more enigmatic inner-deviation sources with impressive wings; as for outer-deviation sources these too require black hole axis shifts, although they also require plasma backflows into relic channels. Evolution in morphology over time relates the variety in structures in inner-deviation sources including XRGs. With features such as non-collinearities, central inner-S "spine," corresponding lobe emission peaks, double and protruding hotspots not uncommon, black hole axis precession, drifts, or flips could be active in a significant fraction of radio sources with prominent off-axis emission. At least 4% of radio galaxies appear to undergo black hole axis rotation. Quasars offer a key signature for recognizing rotating axes. With a rich haul of sources that have likely undergone axis rotation, our work shows the usefulness of low-axial ratio sources in pursuing searches for binary supermassive black holes.
Description:	Open Access
URI:	http://hdl.handle.net/2289/6872
ISSN:	0004-637X 1538-4357-(Online)
Alternative Location:	http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:1710.01652 http://arxiv.org/abs/1710.01652 http://dx.doi.org/10.3847/1538-4357/aa9c4b
Copyright:	2018 American Astronomical Society
Appears in Collections:	Research Papers (A&A)

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