2019/10/31 by Ravi Joshi, Gopal Krishna, Gopal-Krishna +10
Physics and Astronomy · #Astronomy and Astrophysical Research #Elliptical galaxy #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy cluster #Peculiar galaxy #Population #Radio Astronomy Observations and Technology #Radio galaxy #Radio spectrum #Stars #X-shaped radio galaxy #astro-ph.GA #astro-ph.HE
paper · pdf · doi:10.3847/1538-4357/ab536f
17 Pages, 9 Figures, 3 Tables (Accepted for the Publications in ApJ main Journal)
arxiv created 2019/10/31 · openalex created_date 2019/11/22 · openalex publication_date 2019/12/20 · arxiv updated 2020/01/08 · openalex updated_date 2026/08/06
Abstract In pursuit of clues to the origin of “winged” or X-shaped radio galaxies (XRGs) we investigate the parent galaxies of a large sample of 106 XRGs for optical–radio axes alignment, interstellar medium, black hole mass, and large-scale environment. For 41 of the XRGs it was possible to determine the optical major axis and the primary radio axis and the strong tendency for the two axes to be fairly close is confirmed. However, several counter-examples were also found and these could challenge the widely discussed backflow diversion model for the origin of the radio wings. Comparison with a well-defined large sample of normal FR II radio galaxies has revealed that: (i) XRGs possess slightly less massive central black holes than the normal radio galaxies (average masses being log M BH ∼ 8.81 M ⊙ and 9.07 M ⊙ , respectively); (ii) a much higher fraction of XRGs (∼80%) exhibits red mid-IR colors ( W2 − W3 > 1.5), indicating a population of young stars and/or an enhanced dust mass, probably due to relatively recent galaxy merger(s). A comparison of the large-scale environment (i.e., within ∼1 Mpc) shows that both XRGs and FRII radio galaxies inhabit similarly poor galaxy clustering environments (medium richness being 8.94 and 11.87, respectively). Overall, the origin of XRGs seems difficult to reconcile with a single dominant physical mechanism and competing mechanisms seem prevalent.