Alignment in the orientation of LOFAR radio sources
| Autor: | Martin J. Hardcastle, Kenneth Duncan, Wendy L. Williams, Timothy W. Shimwell, E. Osinga, R. J. van Weeren, Cyril Tasse, George K. Miley, A. P. Mechev, H. J. A. Röttgering |
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| Přispěvatelé: | Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS) |
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Active galactic nucleus
Cosmology and Nongalactic Astrophysics (astro-ph.CO) Radio galaxy media_common.quotation_subject FOS: Physical sciences Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics 01 natural sciences 0103 physical sciences 010303 astronomy & astrophysics Astrophysics::Galaxy Astrophysics galaxies: statistics Photometric redshift media_common radio continuum: galaxies [PHYS]Physics [physics] Physics 010308 nuclear & particles physics Orientation (computer vision) Astronomy and Astrophysics LOFAR galaxies: jets Polarization (waves) Astrophysics - Astrophysics of Galaxies Redshift Space and Planetary Science Sky Astrophysics of Galaxies (astro-ph.GA) large-scale structure of Universe [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] Astrophysics - Cosmology and Nongalactic Astrophysics |
| Zdroj: | Astronomy and Astrophysics-A&A Astronomy and Astrophysics-A&A, EDP Sciences, 2020, 642, pp.A70. ⟨10.1051/0004-6361/202037680⟩ |
| ISSN: | 0004-6361 |
| Popis: | Various studies have laid claim to finding an alignment of the polarization vectors or radio jets of active galactic nuclei (AGN) over large distances, but these results have proven controversial and so far, there is no clear explanation for this observed alignment. To investigate this case further, we tested the hypothesis that the position angles of radio galaxies are randomly oriented in the sky by using data from the Low-Frequency Array (LOFAR) Two-metre Sky Survey (LoTSS). A sample of 7,555 double-lobed radio galaxies was extracted from the list of 318,520 radio sources in the first data release of LoTSS at 150 MHz. We performed statistical tests for uniformity of the two-dimensional (2D) orientations for the complete 7,555 source sample. We also tested the orientation uniformity in three dimensions (3D) for the 4,212 source sub-sample with photometric or spectroscopic redshifts. Our sample shows a significant deviation from uniformity (p-value < $10^{-5}$) in the 2D analysis at angular scales of about four degrees, mainly caused by sources with the largest flux densities. No significant alignment was found in the 3D analysis. Although the 3D analysis has access to fewer sources and suffers from uncertainties in the photometric redshift, the lack of alignment in 3D points towards the cause of the observed effect being unknown systematics or biases that predominantly affect the brightest sources, although this has yet to be demonstrated irrefutably and should be the subject of subsequent studies. 10 pages, 13 figures. Accepted for publication in Astronomy & Astrophysics |
| Databáze: | OpenAIRE |
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