Extended Catalog of Winged or X-shaped Radio Sources from the FIRST Survey

Abstract

We present a catalog of 290 "winged" or X-shaped radio galaxies (XRGs) extracted from the latest (2014 December 17) data release of the "Very Large Array Faint Images of the Radio Sky at Twenty centimeter." We have combined these radio images with their counterparts in the TIFR GMRT sky survey at 150 MHz, in an attempt to identify any low surface brightness radio emission present in these sources. This has enabled us to assemble a sample of 106 "strong" XRG candidates and 184 "probable" XRG candidates whose XRG designation needs to be verified by further observations. The present sample of 290 XRG candidates is almost twice as large as the number of XRGs currently known. Twenty-five of our 290 XRG candidates (9 "strong" and 16 "probable") are identified as quasars. Doublepeaked narrow emission lines are seen in the optical spectra of three of the XRG candidates (two "strong" and one "probable"). Nearly 90% of the sample is located in the FR II domain of the Owen-Ledlow diagram. A few of the strong XRG candidates have a rather flat radio spectrum (spectral index α flatter than −0.3) between 150 MHz and 1.4 GHz, or between 1.4 and 5 GHz. Since this is not expected for lobe-dominated extragalactic radio sources (like nearly all known XRGs), these sources are particularly suited for follow-up radio imaging and near-simultaneous measurement of the radio spectrum.

X-shaped Radio Galaxies: Optical Properties, Large-scale Environment, and Relationship to Radio Structure

“…Our starting point is the sample of 106 strong XRG candidates, extracted from the compilation of 290 winged radio galaxies published recently by some of us (Yang et al 2019). In brief, we extended the catalog of 100 XRGs with radio major axis, θ major ≥ 15 arcsec (Cheung 2007) to smaller angular sizes, i.e., considering sources with θ major down to 10 arcsec.…”

“…1. INTRODUCTION X-shaped radio galaxies (XRGs) constitute a small but significant fraction (up to ∼ 3 -10%) of radio galaxies (Leahy & Williams 1984;Leahy & Parma 1992;Yang et al 2019). They exhibit two misaligned pairs of radio lobes with the fainter pair (called 'radio wings') being edge-darkened and the brighter pair (called 'primary' or 'active' lobes) being usually edgebrightened, like the classical (FRII) double radio sources (Leahy & Williams 1984;Capetti et al 2017).…”

“…It needs to be appreciated that the afore-mentioned observational clues are still based on rather small samples, namely 11 XRGs found in the 3CR catalog (Leahy & Parma 1992) and 100 XRG candidates identified in a systematic search based on the FIRST survey (Cheung 2007). Recently, we have expanded the sample by preparing a new catalog of 290 XRG candidates, primarily based on of 1.4 GHz FIRST and the TIFR GMRT sky survey (TGSS) made at 150 MHz (Yang et al 2019). This latest catalog of XRG candidates is an extension to smaller angular sizes of the XRG search undertaken by Cheung (2007), which led to a catalog of 100 XRG candidates, nearly ∼ 75% of which were confirmed as bona-fide XRGs, in follow-up VLA observations (Roberts et al 2018).…”

Multiwavelength Follow-up of FRB180309

“…J2124-3358 is very similar in complexity to the X-, S-, and Z-shaped sources studied by Cheung (2007) 2019). This appears to be an uncataloged example of such galaxies, as a cross-check of published lists of X-shaped sources, Cheung (2007), Proctor (2011), andYang et al (2019) did not include this object. While the object was detected as a 7.7 mJy beam −1 radio source in the 1.4 GHz NVSS survey (Condon et al 1998), the ∼45″ NVSS resolution caused the survey to detect this object as a point source.…”

Morphological classification of compact and extended radio galaxies using convolutional neural networks and data augmentation techniques

“…Detailed discussion on FR dichotomy can be found in Saripalli (2012). While the majority of radio sources population is comprised of FRI and FRII morphologies, more morphological subclasses have been identified such as Narrow-Angle Tail sources (NAT, ; Giacintucci & Venturi (2009)), Wide-Angle Tail sources (WAT, ; Giacintucci & Venturi (2009)), Double-Double Radio Galaxies (DDRG; Schoenmakers et al 2001;Saikia et al 2006), X-shaped radio galaxies (XRG, Leahy & Parma (1992); Cheung (2007); Yang et al (2019); Bhukta et al (2020)), ring like radio galaxies (Proctor 2011), and Hybrid Morphology Radio Sources (HYMORS;Gopal-Krishna & Wiita 2000;Banfield et al 2015;Kapińska et al 2017). Classification of radio galaxies into different morphologies provides information on the formation and evolution of galaxies, and also allows us to understand their cosmic environment (Helfand et al 2015).…”