J/A+A/672/A163 Properties of the 2060 giant radio galaxies (Oei+, 2023)
Measuring the giant radio galaxy length distribution with the LoTSS.
Oei M.S.S.L., van Weeren R.J., Gast A.R.D.J.G.I.B., Botteon A.,
Hardcastle M.J., Dabhade P., Shimwell T.W., Roettgering H.J.A., Drabent A.
<Astron. Astrophys. 672, A163 (2023)>
=2023A&A...672A.163O 2023A&A...672A.163O (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Radio sources ; Redshifts ; Morphology
Keywords: galaxies: active - galaxies: jets -
galaxies: kinematics and dynamics - radio continuum: galaxies -
intergalactic medium
Abstract:
Context: Many massive galaxies launch jets from the accretion disk of
their central black hole, but only ∼103 instances are known in which
the associated outflows form giant radio galaxies (GRGs, or giants):
luminous structures of megaparsec extent that consist of atomic
nuclei, relativistic electrons, and magnetic fields. Large samples are
imperative to understanding the enigmatic growth of giants, and recent
systematic searches in homogeneous surveys constitute a promising
development. For the first time, it is possible to perform meaningful
precision statistics with GRG lengths, but a framework to do so is
missing.
Aims: We measured the intrinsic GRG length distribution by combining a
novel statistical framework with a LOFAR Two-metre Sky Survey (LoTSS)
DR2 sample of freshly discovered giants. In turn, this allowed us to
answer an array of questions on giants. For example, we can now assess
how rare a 5Mpc giant is compared to one of 1Mpc, and how much larger
- given a projected length - the corresponding intrinsic length is
expected to be. Notably, we can now also infer the GRG number density
in the Local Universe.
Methods: We assumed the intrinsic GRG length distribution to be
Paretian (i.e. of power-law form) with tail index ξ, and predicted
the observed distribution by modelling projection and selection
effects. To infer ξ, we also systematically searched the LoTSS DR2
for hitherto unknown giants and compiled the largest catalogue of
giants to date.
Results: We show that if intrinsic GRG lengths are Pareto distributed
with index ξ, then projected GRG lengths are also Pareto
distributed with index ξ. Selection effects induce curvature in the
observed projected GRG length distribution: angular length selection
flattens it towards the lower end, while surface brightness selection
steepens it towards the higher end. We explicitly derived a GRG's
posterior over intrinsic lengths given its projected length, laying
bare the ξ dependence. We also discovered 2060 giants within the
LoTSS DR2; our sample more than doubles the known population.
Spectacular discoveries include the largest, second-largest, and
fourth-largest GRG known (lp=5.1Mpc, lp=5.0Mpc, and lp=4.8Mpc), the
largest GRG known hosted by a spiral galaxy (lp=2.5Mpc), and the
largest secure GRG known beyond redshift 1 (lp=3.9Mpc). We increase
the number of known giants whose angular length exceeds that of the
Moon from 10 to 23; among the discoveries is the angularly largest
known radio galaxy in the Northern Sky, which is also the angularly
largest known GRG (φ=2° Combining theory and data, we
determined that intrinsic GRG lengths are well described by a Pareto
distribution, and measured the index ξ=-3.5±0.5. This implies
that, given its projected length, a GRG's intrinsic length is expected
to be just 15% larger. Finally, we determined the comoving number
density of giants in the Local Universe to be nGRG=5±2
(100Mpc)-3.
Conclusions: We developed a practical mathematical framework that
elucidates the statistics of giant radio galaxy lengths. Through a
LoTSS DR2 search, we also discovered 2060 new giants. By combining
both advances, we determined that intrinsic GRG lengths are well
described by a Pareto distribution with index ξ=-3.5±0.5, and
that giants are truly rare in a cosmological sense: most clusters and
filaments of the Cosmic Web are not currently home to a giant. Thus,
our work yields new observational constraints for analytical models
and simulations featuring radio galaxy growth.
Description:
Properties of the 2060 giant radio galaxies ('GRGs' or 'giants')
discovered during the LOFAR Two-metre Sky Survey (LoTSS) DR2 pipeline
products search described in the paper.
The giants are ranked by projected proper length, with the largest at
the top. The first 50 rows of this dataset are given in Table 2 of the
paper.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablef1.dat 121 2060 Properties of the 2060 giant radio galaxies
('GRGs' or 'giants') discovered during the
LOFAR Two-metre Sky Survey (LoTSS) DR2
pipeline products search
tablef1.fits 2880 86 fits version of tablef1
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See also:
J/A+A/659/A1 : LOFAR Two-metre Sky Survey (LoTSS) DR2 (Shimwell+, 2022)
Byte-by-byte Description of file: tablef1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 I1 --- HNC? [0/1] Flag indicating whether the claimed
host galaxy is just the nearest candidate
(1) or is identified with high certainty
(0) (ishostnearest_candidate)
3- 21 A19 --- SDSS-DR12 Host galaxy Sloan Digital Sky Survey (SDSS)
DR12 name (hostnameSDSS_DR12) (2)
23- 33 F11.7 deg RAdeg Host galaxy right ascension J2000, derived
from SDSS DR12 or Pan-STARRS
(rightascensionJ2000_(deg))
35- 44 F10.7 deg DEdeg Host galaxy declination J2000, derived from
SDSS DR12 or Pan-STARRS
(declinationJ2000(deg))
46- 52 F7.5 --- z Host galaxy cosmological redshift estimate,
derived from SDSS DR12, Gaia DR3,
GLADE 2.4, and DESI DR9 (redshift) (1)
54- 61 F8.5 --- e_z ?=-1 Host galaxy cosmological redshift
uncertainty, derived from SDSS DR12,
Gaia DR3, GLADE 2.4, and DESI DR9
(redshift_error) (1)
63 I1 --- zsp? [0/1] Flag indicating whether the
cosmological redshift estimate is inferred
through spectroscopy (1) or through
photometry (2) (isredshiftspectroscopic)
65- 69 F5.1 arcmin LengthAng Giant radio galaxy angular length (or less
accurately called 'angular size') in LoTSS
DR2 pipeline products (angular_length) (3)
71- 75 F5.3 Mpc LengthMpc Giant radio galaxy proper (rather than
comoving) length estimate, projected onto
the celestial sphere
(projectedproperlength)
77- 81 F5.3 Mpc e_LengthMpc Giant radio galaxy proper (rather than
comoving) length uncertainty, projected
onto the celestial sphere
(projectedproperlength_error)
83- 90 F8.5 10+11Msun M* ?=-1 Host galaxy stellar mass estimate
(stellar_mass) (4)
92-100 F9.6 10+11Msun e_M* ?=-1 Host galaxy stellar mass uncertainty
(stellarmasserror) (4)
102-108 F7.3 10+9Msun MSMBH ?=-1 Host galaxy supermassive black hole
mass estimate derived from SDSS DR12
(SMBH_mass)
110-117 F8.4 10+9Msun e_MSMBH ?=-1 Host galaxy supermassive black hole
mass uncertainty derived from SDSS DR12
(SMBHmasserror)
119 I1 --- SpCl? [0/1] flag indicating whether the host
galaxy's AGN has an SDSS spectral class
label available
(isspectralclass_available)
121 I1 --- HostQSO? [0/1] Flag indicating whether the host
galaxy's AGN is a quasar (only meaningful
when 'isspectralclass_available' is
True) (ishostquasar)
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Note (1): In cases where only a set of candidates containing the host galaxy
could be established beyond reasonable doubt, we list the properties of the
lowest-redshift candidate. In this way, the provided projected proper length
bounds the actual projected proper length from below. We note that this
lowest-redshift candidate is often, but not always, also the most probable
host.
Note (2): Lying outside of the coverage, some GRG host galaxies have no
SDSS DR12 name.
Note (3): The projected proper length columns assume the Planck Collaboration
VI (2020A&A...641A...6P 2020A&A...641A...6P) cosmology. We propagate both cosmological redshift
and angular length uncertainties.
Note (4): derived from Chang et al. (2015ApJS..219....8C 2015ApJS..219....8C, Cat. J/ApJS/219/8)
and Salim et al. (2018ApJ...859...11S 2018ApJ...859...11S) .
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Acknowledgements:
Martijn Simon Soen Liong Oei, oei(at)strw.leidenuniv.nl
(End) Patricia Vannier [CDS] 24-Jan-2023