J/A+A/693/A100 ELAIS-N1 LOFAR deep field polarized sources (Piras+, 2025)
LOFAR Deep Fields: Probing the sub-mJy regime of polarized extragalactic
sources in ELAIS-N1. II. Analysis.
Piras S., Horellou C., Conway J.E., Thomasson M., Shimwell T.W.,
O'Sullivan S.P., Carretti E., Vacca V., Bonafede A., Prandoni I.
<Astron. Astrophys. 693, A100 (2025)>
=2025A&A...693A.100P 2025A&A...693A.100P (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, radio ; Polarization
Keywords: polarization - methods: data analysis - methods: observational -
galaxies: individual: ELAIS-N1
Abstract:
Deep polarization surveys at low radio frequencies are key to cosmic
magnetism studies: Larger catalogs of polarized extragalactic sources
and increased precision on Faraday rotation measures (RMs) make it
possible to probe the magneto-ionic medium along the lines of sight of
the sources and to construct denser RM grids. In a first paper, we
presented a search for polarized sources in deep observations of the
25-square-degree area of the European Large Area ISO Survey-North 1
(ELAIS-N1) field with the LOw Frequency ARray (LOFAR) at
114.9-177.4MHz.
In this paper, we investigate the properties of the polarized radio
galaxies and use the catalog to produce an RM grid of the field.
After identifying the host galaxies and collecting redshift
information, we characterized the radio galaxies in terms of their
radio morphologies, rest-frame radio luminosities, and linear sizes.
We calculated residual rotation measures (RRMs) by removing the
Galactic RM and studied the variation in the RRMs with redshift and
degree of polarization. We produced an RRM grid of the field and
compared the positions of the polarized sources with those of galaxy
clusters and superclusters.
The radio galaxies show a variety of morphologies, including diffuse
emission; Fanaroff Riley type II sources make up about half of the
sample. Using available multiband catalogs, we found redshifts for the
hosts of all polarized sources in the range of 0.06 to 1.9. Polarized
emission is detected mainly from large radio galaxies. The RRM values
have a median close to zero, and they appear to be independent of
redshift and degree of polarization. The sources in the lines of sight
of clusters of galaxies and of a supercluster are indistinguishable in
their polarization and RRM properties from the population of sources
that are not behind these structures.
Description:
Catalog of 33 polarized components in the ELAIS-N1 LOFAR deep field,
detected after stacking 19 8-hour observing epochs.
Objects:
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RA (2000) DE Designation(s)
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16 11 00 +55 00 00 ELAIS-N1 = ELAIS N1
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 216 33 Catalog of 33 polarized components in the
ELAIS-N1 LOFAR deep field
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See also:
J/A+A/648/A2 : LOFAR Two-metre Sky Survey Deep Fields DR1 (Sabater+, 2021)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Source Catalog identification number in
Piras et al. (2024A&A...687A.267P 2024A&A...687A.267P) Paper I
6- 28 A23 --- LOFAR Name of associated total-intensity radio
component in the Sabater et al.
(2021A&A...648A...2S 2021A&A...648A...2S, Cat. J/A+A/648/A2)
catalog, ILT_JHHMMSS.ss+DDMMSS.s
30- 37 F8.4 deg RAdeg Right Ascension of polarized source (J2000)
39- 45 F7.4 deg DEdeg Declination of polarized source (J2000)
47- 54 E8.4 Jy/beam Ppol Polarized intensity
56- 65 E10.5 Jy/beam Ipol Stokes I intensity in the image of Sabater
et al. (2021A&A...648A...2S 2021A&A...648A...2S) at the pixel
of the polarized source
67- 71 F5.2 % Degpol Degree of polarization calculated using the
full-precision values of Ppol and Ipol
74- 78 A5 --- PolInfo Flag to indicate whether the source is
listed as polarized in other catalogs (1)
80- 86 F7.3 rad/m2 RM Rotation measure of polarized source
88- 92 F5.3 rad/m2 e_RM Rotation measure error
94- 98 F5.2 rad/m2 GRM Galactic rotation measure at the
location of the polarized sources
100-103 F4.2 rad/m2 e_GRM GGalactic rotation measure error
105-110 F6.2 rad/m2 RRM Residual rotation measure of
polarized source
112-115 F4.2 rad/m2 e_RRM Residual rotation measure error
117-140 A24 --- HostName Name of the polarized source host galaxy
142-149 F8.4 deg RAHdeg Right Ascension of the host galaxy (J2000)
151-157 F7.4 deg DEHdeg Declination of the host galaxy (J2000)
159-165 F7.5 --- z Redshift of the host galaxy
167-173 E7.1 --- e_z ?=- Redshift error
175 A1 --- zType [sp] Redshift type,
s = spectroscopic, p = photometric
177-185 A9 --- r_z References for redshift (2)
187-189 I3 arcsec Angsize Angular size of the radio galaxy
191-194 I4 kpc Linsize Projected linear size of the radio galaxy
196-201 F6.4 Jy Flux Flux density in Stokes I integrated over
the radio galaxy
203-207 F5.2 [W/Hz] logLum Decimal log of rest-frame luminosity
at 146MHz (W/Hz)
209-211 A3 --- HostClass Host classification (3)
213-216 A4 --- Morph Radio morphology classification
at 146MHz (4)
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Note (1): Flag as follows:
1 = the source is listed as polarized at 1.4GHz in the DRAO ELAIS-N1
catalog (Grant et al.. 2010ApJ...714.1689G 2010ApJ...714.1689G)
2 = the source is listed in the NVSS RM catalog
(Taylor et al., 2009ApJ...702.1230T 2009ApJ...702.1230T)
3 = the source is listed as polarized at 150MHz and 20" resolution in the
LOFAR work of Herrera Ruiz et al. (2021A&A...648A..12H 2021A&A...648A..12H)
Note (2): spectroscopic or photometric redshifts were taken from the following
references:
1 = Ahumada et al., 2020ApJS..249....3A 2020ApJS..249....3A (SDSS DR16, z_spec)
2 = DESI Collaboration, 2023, (DESI EDR, z_spec, 2024AJ....168...58D 2024AJ....168...58D)
3 = Richards et al., 2009ApJS..180...67R 2009ApJS..180...67R
(SDSS DR6, z_phot, Cat. J/ApJS/180/67)
4 = Beck et al., 2021MNRAS.500.1633B 2021MNRAS.500.1633B (Pan-STARRS, z_phot)
5 = Zou et al., 2022RAA....22f5001Z 2022RAA....22f5001Z (DESI DR9, z_phot)
6 = Duncan et al., 2022MNRAS.512.3662D 2022MNRAS.512.3662D (DESI-LS8, z_phot, Cat. VII/292)
7 = Duncan et al., 2021A&A...648A...4D 2021A&A...648A...4D
(LoTSS Deep Fields, z_phot, Cat. J/A+A/648/A4)
8 = Wen & Han, 2021MNRAS.500.1003W 2021MNRAS.500.1003W
(HSC-SSP/unWISE, z_phot, Cat. J/MNRAS/500/1003)
9 = Zou et al., 2022RAA....22f5001Z 2022RAA....22f5001Z (DESI DR9, z_phot)
10 = Falco et al., 1998ApJ...494...47F 1998ApJ...494...47F (z_spect)
Note (3): Host classification as follows:
QSO = Quasi-Stellar Object
Bl = blazar
G = galaxy
Note (4): Radio morphology classification as follows:
C = compact
OE = other extended
FRI = FRI radio galaxy
FRII = FRII radio galaxy
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Acknowledgements:
Sara Piras,
References:
Oiras et al., Paper I 2024A&A...687A.267P 2024A&A...687A.267P
(End) Patricia Vannier [CDS] 03-Dec-2024