J/A+A/690/A321 1.7GHz images of 9 faint radio quasars (Krezinger+, 2024)
Revealing faint compact radio jets at redshifts above 5 with very long
baseline interferometry.
Krezinger M., Baldini G., Giroletti M., Sbarrato T., Ghisellini G.,
Giovannini G., An T., Gabanyi K.E., Frey S.
<Astron. Astrophys. 690, A321 (2024)>
=2024A&A...690A.321K 2024A&A...690A.321K (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; QSOs ; Radio sources
Keywords: techniques: high angular resolution - techniques: interferometric -
galaxies: high-redshift - galaxies: jets - quasars: general -
quasars: supermassive black holes
Abstract:
Over the past two decades, our knowledge of the high-redshift (z>5)
radio quasars has expanded, thanks to dedicated high-resolution very
long baseline interferometry (VLBI) observations. Distant quasars
provide unique information about the formation and evolution of the
first galaxies and supermassive black holes in the Universe. Powerful
relativistic jets are likely to have played an essential role in these
processes. However, the sample of VLBI-observed radio quasars is still
too small to allow meaningful statistical conclusions.
We extend the list of the VLBI observed radio quasars to investigate
how the source structure and physical parameters are related to radio
loudness.
We assembled a sample of ten faint radio quasars located at 5<z<6 with
their radio-loudness indices spanning between 0.9-76. We observed the
selected targets with the European VLBI Network (EVN) at 1.7GHz. The
milliarcsecond-scale resolution of VLBI at this frequency allowed us
to probe the compact innermost parts of radio-emitting relativistic
jets. In addition to the single-band VLBI observations, we collected
single-dish and low-resolution radio interferometric data to
investigate the spectral properties and variability of our sources.
The detection rate of this high-redshift, low-flux-density sample is
90%, with only one target (J0306+1853) remaining undetected. The other
nine sources appear core-dominated and show a single, faint and
compact radio core on this angular scale. The derived radio powers are
typical of Fanaroff-Riley II radio galaxies and quasars. By extending
our sample with other VLBI-detected z>5 sources from the literature,
we found that the core brightness temperatures and monochromatic radio
powers tend to increase with radio loudness.
Description:
The selected ten faint radio sources were observed with the EVN
at a single frequency band centred around 1.66GHz. The observations
were carried out in two sessions under the project code EG119 (PI: G.
Baldini), one with nine targets in 2022 June 3 (EG119A) and another
with J0306+1853 as the only target in 2022 October 22 (EG119B).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 84 9 1.7-GHz VLBI image parameters and source positions
list.dat 94 9 List of fits images
fits/* . 9 Individual fits images
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Source name (JHHMM+DDMM)
12- 13 I2 h RAh VLBI right ascension (J2000)
15- 16 I2 min RAm VLBI right ascension (J2000)
18- 25 F8.5 s RAs VLBI right ascension (J2000)
27- 33 F7.5 s e_RAs rms uncertainty on right ascension
35 A1 --- DE- VLBI declination sign (J2000)
36- 37 I2 deg DEd VLBI declination (J2000)
39- 40 I2 arcmin DEm VLBI declination (J2000)
42- 48 F7.4 arcsec DEs VLBI declination (J2000)
50- 55 F6.4 arcsec e_DEs rms uncertainty on declination
57- 60 F4.2 mJy IPeak Image peak intensity at 1.7-GHz
62- 65 F4.2 mJy e_IPeak Image peak intensity 1.7-GHz uncertainty
67- 70 F4.1 mas Maj Restoring beam major axis
72- 74 F3.1 mas Min Restoring beam minor axis
76- 79 F4.1 deg PA Restoring beam position angle,
measured from north through east
81- 84 F4.2 mJy/beam Noise 1σ noise level
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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- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 37 A10 "datime" Obs.date Observation date
39- 45 F7.5 GHz Freq [1.65849] Observed frequency
47- 49 I3 Kibyte size Size of FITS file
51- 73 A23 --- FileName Name of FITS file, in subdirectory fits
75- 94 A20 --- Title Title of the FITS file
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Acknowledgements:
Mate Krezinger, krezinger.mate(at)csfk.org
(End) Patricia Vannier [CDS] 08-Oct-2024