J/A+A/658/A8 Resolved jet of 3C 273 at 150 MHz (Harwood+, 2022)
The resolved jet of 3C 273 at 150 MHz.
Sub-arcsecond imaging with the LOFAR international baselines.
Harwood J.J., Mooney S., Morabito L.K., Quinn J., Sweijen F.,
Groeneveld C., Bonnassieux E., Kappes A., Moldon J.
<Astron. Astrophys. 658, A8 (2022)>
=2022A&A...658A...8H 2022A&A...658A...8H (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Active gal. nuclei ; Radio sources
Keywords: galaxies: active - galaxies: jets - galaxies: individual: 3C 273 -
radiation mechanisms: non-thermal - radio continuum: galaxies
Abstract:
Since its discovery in 1963, 3C 273 has become one of the most widely
studied quasars with investigations spanning the electromagnetic
spectrum. While much has therefore been discovered about this
historically notable source, its low-frequency emission is far less
well understood. Observations in the MHz regime have traditionally
lacked the resolution required to explore small-scale structures, such
as knots and diffuse jet emission, that are key to understanding the
processes that result in the observed emission. Advances in the
processing of LOFAR international baseline data have now removed this
limitation, providing the opportunity to explore this key area for the
first time.
In this paper we use the first sub-arcsecond images of 3C 273 at MHz
frequencies to investigate the morphology of the compact jet
structures and the processes that result in the observed spectrum. We
will determine the jet's kinetic power, place constraints on the bulk
speed and inclination angle of the jets, and look for evidence of the
elusive counterjet at 150MHz.
Using the full complement of LOFAR's international stations (German,
Poland, France, UK, Sweden), we produce 0.31x0.21 arcsec images of
3C 273 at 150MHz. Using ancillary data at GHz frequencies, we fit
free-free absorption (FFA) and synchrotron self-absorption (SSA)
models to each region in order to determine their validity in
explaining the observed spectra.
The images presented display for the first time that robust,
high-fidelity imaging of low-declination complex sources is now
possible with the LOFAR international baselines. We show that the main
small-scale structures of 3C 273 match those seen at higher
frequencies, with a tenuous detection of an extension to the outer
lobe. We find that FFA and SSA models are able to describe the
spectrum of the knots and, while differentiating between model types
requires further observations, conclude that absorption is present in
the observed emission. We determine the kinetic power of the jet to be
in the range of 3.5x1043-1.5x1044erg/s which agrees with estimates
made using higher frequency observations. We derive lower limits for
the bulk speed and Lorentz factor of beta>0.55 and Gamma>1.2
respectively. The counter-jet remains undetected at 150MHz, placing a
limit on the peak brightness of Scj150<40mJy/beam.
Description:
The quasar 3C 273 was observed during LOFAR cycle 8 using 24 core
stations, 14 remote stations, and 12 international stations (six
stations in Germany, three in Poland, and one in each in France, the
UK, and Sweden). The observations were made using a four hour track
when 3C 273 was highest in the sky. This is particularly desirable
when using LOFAR due to the source's low declination (+02°),
where increased ionospheric decorrelation of the signal increases the
difficulty in achieving a robust calibration of the source.
Objects:
----------------------------------------------------
RA (2000) DE Designation(s)
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12 29 06.70 +02 03 08.6 3C 273 = QSO J1229+0203
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 29 8 Flux densities and spectral index values
table3.dat 42 9 Free-free and synchrotron self-absorption model
fitting values
list.dat 117 1 Information on fits image
fits/* . 1 FITS image
listimg.dat 127 16 List of png images
img/* . 16 Individual png images
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See also:
J/MNRAS/392/1181 : BV(RI)c photometry of 3C 273 (Dai+, 2009)
J/ApJS/213/26 : Optical light curves of PHL1811 and 3C273 (Fan+, 2014)
J/A+A/576/A122 : 3C 273 high energy spectrum (Esposito+, 2015)
J/A+A/601/A35 : High-fidelity VLA imaging of 3C273 (Perley+, 2017)
J/ApJS/229/21 : VRI monitoring of the QSO 3C 273 in 2005-2016 (Xiong+, 2017)
J/A+A/604/A111 : 22GHz image of 3C 273 (Bruni+, 2017)
J/ApJ/876/49 : 10yr reverberation mapping campaign for 3C273 (Zhang+, 2019)
J/ApJ/880/155 : RI photometry of blazars S5 0716+714 and 3C 273 (Liu+, 2019)
J/A+A/636/A62 : Light curves of 3C273 during 2015-2019 (Kim+, 2020)
J/AJ/159/259 : Opt-NIR light curve of 3C 273 (Sobrino Figaredo+, 2020)
J/ApJ/897/18 : Swift UVOT observation of radio quasar 3C 273 (Li+, 2020)
J/A+A/658/A2 : LOFAR Long-Baseline Calibrator Survey. II. (Jackson+, 2022)
J/A+A/658/A4 : LOFAR imaging of Arp299 at 150MHz (Ramirez-Olivencia, 2022)
J/A+A/658/A5 : Hercules A LOFAR and JVLA images (Timmerman+, 2022)
J/A+A/658/A6 : 3C293 high and low resolution maps (Kukreti+, 2022)
J/A+A/658/A10 : 3C295 LOFAR, MERLIN and VLA images (Bonnassieux+, 2022)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Feature Jet structure label
7 A1 --- l_S150 Limit flag on S150
8- 13 F6.3 Jy S150 Flux density at 150MHz
14- 19 F6.3 Jy e_S150 ? Flux density at 150MHz uncertainty
21- 24 F4.2 --- alpha ? Spectral index between 150MHz and 8330MHz,
alpha1508330
26- 29 F4.2 --- e_alpha ? Spectral index uncertainty
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Feature Jet structure label
7 A1 --- l_taunu0 Limit flag on taunu0
8- 13 F6.3 --- taunu0 FFA optical depth at a reference of 150MHz
15- 18 F4.2 --- e_taunu0 ? taunu0 uncertainty
20- 23 F4.2 --- alphaFFA Free-free absorption index (±0.03)
25 A1 --- l_nup Limit flag on nup
26- 31 F6.2 MHz nup Frequency at which the region becomes
optically think for the SSA model
33- 37 F5.2 MHz e_nup ? nup uncertainty
39- 42 F4.2 --- alphaSSA Synchrotron-self absorption index (±0.03)
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 50 A21 "datime" Obs.date Observation date
52- 58 F7.3 MHz Freq Observed frequency
60- 64 I5 Kibyte size Size of FITS file
66- 98 A33 --- FileName Name of FITS file, in subdirectory fits
100-117 A18 --- Title Title of the FITS file
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Byte-by-byte Description of file: listimg.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 33 A33 --- FileName Name of the png image, in subdirectory img
35-127 A93 --- Title Title of the file, in subdirectory img
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Acknowledgements:
Jeremy Harwood, jeremy.harwood(at)physics.org
References:
Morabito et al., Paper I 2022A&A...658A...1M 2022A&A...658A...1M
Jackson et al., Paper II 2022A&A...658A...2J 2022A&A...658A...2J, Cat. J/A+A/658/A2
Sweijen et al., Paper III 2022A&A...658A...3S 2022A&A...658A...3S
Ramirez-Olivencia et al., Paper IV 2022A&A...658A...4R 2022A&A...658A...4R, Cat, J/A+A/658/A4
Timmerman et al., Paper V 2022A&A...658A...5T 2022A&A...658A...5T, Cat, J/A+A/658/A5
Kukreti et al., Paper VI 2022A&A...658A...6K 2022A&A...658A...6K, Cat, J/A+A/658/A6
Badole et al., Paper VII 2022A&A...658A...7B 2022A&A...658A...7B
Groeneveld et al., Paper IX 2022A&A...658A...9G 2022A&A...658A...9G
Bonnassieux et al., Paper X 2022A&A...658A..10B 2022A&A...658A..10B, Cat. J/A+A/658/A10
(End) Patricia Vannier [CDS] 17-Jan-2022