Local alignments of parsec-scale AGN radiojets

Abstract

Context. Coherence in the characteristics of neighboring sources in the 2D and 3D space may suggest the existence of large-scale cosmic structures that are useful for cosmological studies. Numerous works have been conducted to detect such features in global scales as well as in confined areas of the sky. However, their results are often contradictory and their interpretation remains controversial. Aims. We investigate the potential alignment of parsec-scale radio jets in localized regions of the coordinate-redshift space. Methods. We used data from the Astrogeo VLBI FITS image database to deduce jet directions of radio sources. We performed the search for statistical alignments between nearby sources and explore the impact of instrumental biases. Results. We unveil four regions for which the alignment between jet directions deviates from randomness at a significance level of more than 5σ. We find that this effect is unlikely to be due to instrumental systematics. Intriguingly, their locations coincide with other known large-scale cosmic structures or regions of alignment. Conclusions. If the alignments found here are the result of physical processes, the discovered regions may designate some of the largest structures known to date.

Correlated orientations of the axes of large quasar groups on Gpc scales

“…Several studies report that radio jets are aligned over large scales (Taylor & Jagannathan 2016;Contigiani et al 2017;Mandarakas et al 2021), supporting the intrinsic alignment explanation independently of polarisation measurements. (The work by Mandarakas et al (2021) appears to supersede earlier work by the same group, Blinov et al (2020), in which no alignment was found.)…”

“…Several studies report that radio jets are aligned over large scales (Taylor & Jagannathan 2016;Contigiani et al 2017;Mandarakas et al 2021), supporting the intrinsic alignment explanation independently of polarisation measurements. (The work by Mandarakas et al (2021) appears to supersede earlier work by the same group, Blinov et al (2020), in which no alignment was found.) The potential correspondence of the QJARs (quasar jet alignment regions) from Mandarakas et al (2021) with other large-scale structures such as the regions of correlated polarisations is a notable feature.…”

“…(The work by Mandarakas et al (2021) appears to supersede earlier work by the same group, Blinov et al (2020), in which no alignment was found.) The potential correspondence of the QJARs (quasar jet alignment regions) from Mandarakas et al (2021) with other large-scale structures such as the regions of correlated polarisations is a notable feature. In general, the corroboration of very large structures by independent tracers can provide compelling support.…”

A mechanism to explain Galaxy alignment over a range of scales

“…A signal of alignment of radio polarizations has also been observed on smaller scales of order 100 Mpc (Tiwari & Jain 2013;Pelgrims & Hutsemékers 2015). Mandarakas et al (2021) claim to find four regions of radio galaxy axis alignment on distance scale of order ≈ 400 Mpc at a significance level of more than 5σ. Furthermore several studies have claimed alignment of radio galaxy axis on distance scales of order 20 to 60 Mpc (Taylor & Jagannathan 2016;Contigiani et al 2017;Panwar et al 2020).…”

Correlated orientations of the axes of large quasar groups on Gpc scales

“…Several studies report that radio jets are aligned o v er large scales (Taylor & Jagannathan 2016 ;Contigiani et al 2017 ;Mandarakas et al 2021 ), supporting the intrinsic alignment explanation independently of polarization measurements. [The work by Mandarakas et al ( 2021 ) appears to supersede earlier work by the same group, Blinov et al ( 2020 ), in which no alignment was found.]…”