J/MNRAS/511/4159 Study of LQGs with SDSS-DR7-QSO data (Friday+, 2022)
Correlated orientations of the axes of large quasar groups on Gpc scales.
Friday T., Clowes R.G., Williger G.M.
<Mon. Not. R. Astron. Soc. 511, 4159-4178 (2022)>
=2022MNRAS.511.4159F 2022MNRAS.511.4159F (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Surveys ; Positional data ; Active gal. nuclei ;
Galaxies, group ; Polarization ; Redshifts ; Spectroscopy ;
Optical
Keywords: methods: statistical - surveys; quasars: general -
large-scale structure of Universe - cosmology: observations
Abstract:
Correlated orientations of quasar optical and radio polarization, and
of radio jets, have been reported on Gpc scales, possibly arising from
intrinsic alignment of spin axes. Optical quasar polarization appears
to be preferentially either aligned or orthogonal to the host
large-scale structure, specifically large quasar groups (LQGs). Using
a sample of 71 LQGs at redshifts 1.0 ≤ z ≤ 1.8, we investigate
whether LQGs themselves exhibit correlated orientation. We find that
LQG position angles (PAs) are unlikely to be drawn from a uniform
distribution (p-values 0.008 ≲ p ≲ 0.07). The LQG PA distribution is
bimodal, with median modes at θ{bar} 45 ± 2°,
136 ± 2°, remarkably close to the mean angles of quasar radio
polarization reported in two regions coincident with our LQG sample.
We quantify the degree of alignment in the PA data, and find that LQGs
are aligned and orthogonal across very large scales. The maximum
significance is ~= 0.8 per cent (2.4σ) at typical angular
(proper) separations of ∼30° (1.6 Gpc). If the LQG orientation
correlation is real, it represents large-scale structure alignment
over scales larger than those predicted by cosmological simulations
and at least an order of magnitude larger than any so far observed,
with the exception of quasar- polarization/radio-jet alignment. We
conclude that LQG alignment helps explain
quasar-polarization/radio-jet alignment, but raises challenging
questions about the origin of the LQG correlation and the assumptions
of the concordance cosmological model.
Description:
In this paper we investigate for the first time whether LQGs exhibit
coherent orientation, and whether this can explain the reported
alignments of quasar polarization from Hutsemekers
(1998A&A...332..410H 1998A&A...332..410H, Cat. J/A+A/332/410 ) to Pelgrims
(2019A&A...622A.145P 2019A&A...622A.145P). This examines scales larger than those so far
analysed, and potentially offers corroborating evidence for, and
enhancement of, the intrinsic alignment interpretation of the results
from many quasar polarization studies (e.g. Hutsemekers & Lamy
2001A&A...367..381H 2001A&A...367..381H; Jain et al. 2004MNRAS.347..394J 2004MNRAS.347..394J; Cabanac et al.
2005ASPC..343..498C 2005ASPC..343..498C; Tiwari & Jain 2013IJMPD..2250089T; Pelgrims &
Cudell 2014MNRAS.442.1239P 2014MNRAS.442.1239P; Pelgrims & Hutsemekers
2015MNRAS.450.4161P 2015MNRAS.450.4161P). If true, it would represent large-scale
structure alignments over ~> Gpc scales, larger than those predicted
by cosmological simulations and larger than any so far observed, (i.e
see section Introcduction).
As explained in the section 2, our LQG sample is taken from the work
of Clowes et al. (2012MNRAS.419..556C 2012MNRAS.419..556C, 2013MNRAS.429.2910C 2013MNRAS.429.2910C). The LQGs
were detected using quasars from the SDSS (York et al.
2000AJ....120.1579Y 2000AJ....120.1579Y), specifically Quasar Redshift Survey Data Release
7 (DR7QSO; Schneider et al. 2010AJ....139.2360S 2010AJ....139.2360S, Cat. VII/260). The
DR7QSO catalogue of 105783 quasars covers a region of ∼9380 deg2,
with its main contiguous area of ∼7600 deg2 in the north Galactic
cap (NGC). Clowes et al. (2012MNRAS.419..556C 2012MNRAS.419..556C, 2013MNRAS.429.2910C 2013MNRAS.429.2910C)
restrict their quasar sample to low-redshift (z ≤ 2) quasars with
apparent magnitude i ≤ 19.1 in order to achieve an approximately
spatially uniform sample (Vanden Berk et al. 2005AJ....129.2047V 2005AJ....129.2047V;
Richards et al. 2006AJ....131.2766R 2006AJ....131.2766R, Cat. J/AJ/131/2766).
Next, we determine group orientations, compute parallel transport
vectors, mock LQGs catalogues and thus perform statisitcal analysis of
LQG position angles computed from mock LQGs (i.e see section 2.3, 2.4
and 3 fro methods). As presented in the section 4 Results, both the 2D
and 3D approaches results are presented in the tablec1.dat regrouping
peer LQG the number of members, mean position and redshift,
statistical parameters (w71,γh), position angles
(PA2D,PA3D) and enclosing ellipsoid axes lengths (a,b,c). We
identify 71 LQGs of => 20 quasars and detection significance =>
2.8σ, (i.e appendix C).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablec1.dat 60 71 The 71 large quasar groups LQGs parameters
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See also:
VII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010)
VII/289 : SDSS quasar catalog, sixteenth data release (DR16Q)
(Lyke+, 2020)
J/A+A/332/410 : Quasar polarization (Hutsemekers 1998)
J/AJ/131/2766 : Quasar luminosity function from SDSS-DR3 (Richards+, 2006)
J/A+A/441/915 : Alignments of quasar polarization vectors (Hutsemekers+, 2005)
Byte-by-byte Description of file: tablec1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Nmemb The number of members belonging to the large
quasar group (m)
4- 8 F5.1 deg RAdeg Mean right ascension of the member quasars
(J2000) (α{bar})
10- 13 F4.1 deg DEdeg Mean declination of the member quasars (J2000)
(δ{bar})
15- 18 F4.2 --- z Mean redshift of the member quasars (z{bar})
20- 23 F4.2 --- w71 The normalized goodness-of-fit weight w is
scaled by w71 = w * 71 for clarity, and to
distinguish those LQGs weighted higher
(w71 > 1) or lower (w71 < 1) than the mean
w{bar} (w71)
25- 29 F5.1 deg PA2D Position angle computed from the 2D approach
(θ2D)
31- 34 F4.1 deg HWCI2D Half-width confidence interval HWCI γh
computed from the 2D approach (γh2D)
36- 40 F5.1 deg PA3D Position angle computed from the 3D approach
(θ3D)
42- 45 F4.1 deg HWCI3D Half-width confidence interval HWCI γh
computed from the 3D approach (γh3D)
47- 50 F4.2 --- a Ratio of LQG enclosing ellipsoid axe, major
axis a dimensionless length from the 3D
approach from Appendix C Figure C2 (a)
52- 55 F4.2 --- b Ratio of LQG enclosing ellipsoid axe,
intermediate axis b dimensionless length from
the 3D approach from Appendix C Figure C2 (b)
57- 60 F4.2 --- c Ratio of LQG enclosing ellipsoid axe, minor
axis c dimensionless length from the 3D
approach from Appendix C Figure C2 (c)
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 28-Jan-2025