J/A+A/691/A35 Optical polarimetry of 152 AGN (Blinov+, 2024)
Polarization of active galactic nuclei with significant VLBI-Gaia displacements.
Blinov D., Arshinova A.
<Astron. Astrophys. 691, A35 (2024)>
=2024A&A...691A..35B 2024A&A...691A..35B (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, radio ; Galaxies, optical ; Polarization
Keywords: polarization - techniques: interferometric - astrometry -
quasars: general
Abstract:
Numerous studies have reported significant displacements in the
coordinates of active galactic nuclei (AGN) between measurements using
the Very Long Baseline Interferometry (VLBI) technique and those
obtained by the Gaia space observatory. There is consensus that these
discrepancies do indeed manifest astrometrically resolved
sub-components of AGN rather than random measurement noise. Among
other evidence, it has been reported that AGN with VLBI-to-Gaia
displacements (VGD) pointing downstream their parsec-scale radio jets
exhibit higher optical polarization compared to sources with the
opposite (upstream) VGD orientation.We aim to verify the previously
reported connection between optical polarization and VGD-jet angle
using a larger dataset of polarimetric measurements and updated Gaia
DR3 positions. We also seek further evidence supporting the disc-jet
dichotomy as an explanation of such a connection by using mm-wave
polarization and multi-band optical polarization measurements. We
performed optical polarimetric observations of 152 AGN using three
telescopes. These data are complemented by other publicly available
polarimetric measurements of AGN. We cross-matched public astrometric
data from VLBI and Gaia experiments, obtain corresponding positional
displacements, and combined this catalog with the polarimetric and jet
directions data. AGN with downstream VGD are confirmed to have
significantly higher optical fractional polarization than the upstream
sample. At the same time, the mm-wavelength polarization of the two
samples shows very similar distributions. Our results support the
hypothesis that the VLBI-to-Gaia displacements pointing down the radio
jet are likely caused by a component in the jet emitting highly
polarized synchrotron radiation and dominating in the overall optical
emission. The upstream-oriented VGD are likely to be produced by the
low-polarized emission of the central engine sub-components, which
dominate in the optical.
Description:
The polarimetric parameters of 152 AGN are presented. Observations
were conducted using imaging polarimetry mode with three instruments:
FORS2/VLT, CAFOS/CAHA, and the RoboPol 1.3-m telescope at the Skinakas
Observatory. FORS2 observations are single-epoch measurements taken in
the R_SPECIAL+76 band between November 2019 and March 2020 (program
ID: 0104.B-0351). RoboPol and CAFOS (program ID: OPTICON 2019B/029)
observed some sources quasi-simultaneously in the Cousins-R and
SDSS-g' bands. A few sources were observed over multiple epochs with
RoboPol; in these cases, the weighted average polarization parameters
are provided. The polarization parameters are corrected for the
instrumental polarization.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 30 152 Coordinates of the sample sources
table1.dat 88 139 R-band polarization measurements with
FORS2 and RoboPol
table2.dat 174 39 Quasi-simultaneous R- and g'-band measurements
with CAFOS and RoboPol
--------------------------------------------------------------------------------
See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
J/A+A/644/A159 : The third realization of the ICRF, ICRF3 (Charlot+, 2020)
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Source name
12- 20 F9.5 deg RAdeg Right ascension (J2000) (1)
22- 30 F9.5 deg DEdeg Declination (J2000) (1)
--------------------------------------------------------------------------------
Note (1): Coordinates of all sources except J2225+2247 are rounded values from
Gaia DR3 (Cat. I/355, gaiadr3). Coordinates of J2225+2247 are from the
Pan-STARRS release 1 (Cat. II/349, ps1)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name AGN J2000 name (JHHMM+DDMM)
13 I1 --- Nobs Number of observing epochs
16- 22 F7.4 --- q Relative Stokes parameter Q/I or its weighted
average if Nobs>1
25- 30 F6.4 --- e_q Uncertainty of q or its weighted average
33- 39 F7.4 --- u Relative Stokes parameter U/I or its weighted
average if Nobs>1
42- 47 F6.4 --- e_u Uncertainty of u or its weighted average
50- 54 F5.2 % PD Fractional polarization
58- 61 F4.2 % e_PD Uncertainty of PD
64- 69 F6.2 deg PA [] Position Angle of the polarization plane
72- 76 F5.2 deg e_PA Uncertainty of PA
82- 88 A7 --- Inst Instrument
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name AGN J2000 name (JHHMM+DDMM)
13- 25 F13.5 d gJD Julian Date of the g'-band observation
28- 34 F7.4 --- gq Relative Stokes parameter Q/I in the g'-band
37- 42 F6.4 --- e_gq Uncertainty of gq
45- 51 F7.4 --- gu Relative Stokes parameter U/I in the g'-band
54- 59 F6.4 --- e_gu Uncertainty of gu
62- 65 F4.1 % gPD Fractional polarization in the g'-band
70- 72 F3.1 % e_gPD Uncertainty of gPD
75- 79 F5.1 deg gPA Position Angle of the polarization plane
in the g'-band
83- 86 F4.1 deg e_gPA Uncertainty of gPA
89-101 F13.5 d RJD Julian Date of the R-band observation
104-110 F7.4 --- Rq Relative Stokes parameter Q/I in the R-band
113-118 F6.4 --- e_Rq Uncertainty of Rq
121-127 F7.4 --- Ru Relative Stokes parameter U/I in the R-band
130-135 F6.4 --- e_Ru Uncertainty of Ru
138-141 F4.1 % RPD Fractional polarization in the R-band
146-148 F3.1 % e_RPD Uncertainty of RPD
151-155 F5.1 deg RPA Position Angle of the polarization plane
in the R-band
159-162 F4.1 deg e_RPA Uncertainty of RPA
168-174 A7 --- Inst Instrument
--------------------------------------------------------------------------------
Acknowledgements:
From Dmitry Blinov, blinov(at)ia.forth.gr
(End) Dmitry Blinov [IA/FORTH, Greece], Patricia Vannier [CDS] 26-Sep-2024