J/ApJ/904/179 VLA observations of 147 radio-loud Quasars (Maithil+, 2020)
Investigating Orientation Effects Considering Angular Resolution for a Sample of
Radio-loud Quasars Using VLA Observations.
Maithil J., Runnoe J.C., Brotherton M.S., Wardle J.F., Wills B.J.,
DiPompeo M., De Breuck C.
<Astrophys. J., 904, 179 (2020)>
=2020ApJ...904..179M 2020ApJ...904..179M
ADC_Keywords: QSOs; Active gal. nuclei; Spectra, millimetric/submm;
Spectra, radio; Redshifts
Keywords: Quasars ; Radio loud quasars ; Very Large Array ; Active
galactic nuclei ; Radio cores
Abstract:
Radio core dominance measurements, an indicator of jet orientation,
sometimes rely on core flux density measurements from large-area
surveys like Faint Images of the Radio Sky at Twenty cm (FIRST) that
have an angular resolution of only 5". Such low-resolution surveys
often fail to resolve cores from the extended emission, resulting in
an erroneous measurement. We focus on investigating this resolution
effect for a sample of 119 radio-loud quasars. We obtained continuum
observations from NSF's Karl G. Jansky Very Large Array (VLA) at 10GHz
in A configuration with a 0.2 resolution. Our measurements show that
at FIRST spatial resolution, core flux measurements are indeed
systematically high even after considering the core variability. For a
handful of quasars, 10GHz images reveal extended features, whereas the
FIRST image shows a point source. We found that the resolution effect
is more prominent for quasars with smaller angular sizes. We further
computed two radio core dominance parameters R and R5100 for use in
statistical orientation investigations with this sample. We also
present the spectral energy distributions between 74MHz and 1.4GHz,
which we used to measure the spectral index of the extended emission
of these quasars. Our results empirically confirm that determination
of radio core dominance requires high spatial resolution data. We
highlight the practical issues associated with the choice of frequency
and resolution in the measurement of core and extended flux densities.
Description:
The Very Large Array (VLA) continuum observations were carried out at
10GHz (X band) with the A configuration to achieve 0.2" resolution, 25
times smaller than FIRST to separate the unresolved core from extended
emission. The VLA project ID of the observations is 16B-329.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 128 119 SDSS names, redshifts, optical and radio flux
densities, and spectral indices of extended
emission of 119 radio-loud quasars
table2.dat 65 114 Logarithm of R and R5100 calculated using new 10GHz
and FIRST 1.4GHz core flux densities
table4.dat 164 28 Data for 28 additional objects observed with VLA
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See also:
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
VIII/84 : A final non-redundant catalogue for 7C 151-MHz survey (Hales+ 2007)
VII/252 : SDSS-DR5 quasar catalog (Schneider+, 2007)
VIII/97 : 74MHz VLA Low-frequency Sky Survey Redux (VLSSr) (Lane+, 2014)
J/A+AS/124/259 : Westerbork Northern Sky Survey I. (Rengelink+ 1997)
J/A+A/369/380 : CSS/GPS radio sources VLA observations (Fanti+, 2001)
J/ApJ/658/203 : VLBA imaging and polarimetry survey at 5GHz (Helmboldt+, 2007)
J/AJ/141/182 : Radio and optical properties of QSOs (Kimball+, 2011)
J/AJ/147/143 : MOJAVE. XI. Spectral distributions (Hovatta+, 2014)
J/MNRAS/454/3864 : Orientation & QSO black hole mass estim. (Brotherton+ 2015)
J/A+A/598/A78 : The GMRT 150MHz all-sky radio survey (Intema+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- SDSS SDSS identifier
21- 25 F5.3 --- z [0.15/0.6] Spectroscopic redshift
27- 32 F6.2 10-17cW/m2/nm F5100 [0.17/176] Flux density at 5100Å (1)
34- 37 F4.2 10-17cW/m2/nm e_F5100 [0.1/0.3] Uncertainty in F5100 (1)
39- 46 F8.3 mJy/beam 10Core [0.53/4895]? 10GHz core flux density
48- 51 F4.2 mJy/beam e_10Core [0.02/3]? Uncertainty in 10Core
53- 59 F7.2 mJy/beam FIRSTCore [0.7/2853] FIRST 1.4GHz core flux
density
61- 64 F4.2 mJy/beam e_FIRSTCore [0.1/2] Uncertainty in FIRSTCore
66- 70 I5 mJy WENSSTot [109/30410] WENSS total flux density
72- 75 I4 mJy e_WENSSTot [6/1216] Uncertainty in WENSSTot
77- 83 F7.1 mJy TGSSTot [142/53958]? TGSS total flux density
85- 90 F6.1 mJy e_TGSSTot [15/5397]? Uncertainty in TGSSTot
92- 96 I5 mJy 7CTot [191/56685]? 7C total flux density
98-101 I4 mJy e_7CTot [27/2743]? Uncertainty in 7CTot
103-107 I5 mJy VLSSrTot [400/87680]? VLSSr total flux density
109-112 I4 mJy e_VLSSrTot [70/7550]? Uncertainty in VLSSrTot
114-119 F6.3 --- SpIndex [-1.15/-0.53] Slope of extended
emission
121-125 F5.3 --- e_SpIndex [0.03/0.2] Uncertainty in SpIndex
127-128 A2 --- Group Assigned group based on radio SED (2)
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Note (1): In units of 1e-17erg/s/cm2/Å.
Note (2): Quasars are assigned group 1, 2, 2-flag (2f) or 3 on the basis
of their radio spectrum. See section 5 for details.
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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- 19 A19 --- SDSS SDSS identifier
21- 25 F5.2 [-] R-1.4 [-2.62/2.68] log radio core dominance from 1.4GHz
core flux
27- 31 F5.3 [-] e_R-1.4 [0.03/0.4] Uncertainty in R-1.4
33- 37 F5.2 [-] R-10 [-2.23/2.17] log radio core dominance from 10GHz
core flux
39- 43 F5.3 [-] e_R-10 [0.03/0.4] Uncertainty in R-10
45- 48 F4.2 [-] R5100-1.4 [0.53/4.79] log R5100 from 1.4GHz core flux
density
50- 54 F5.3 [-] e_R5100-1.4 [0.001/2] Uncertainty in R5100-1.4
56- 59 F4.2 [-] R5100-10 [0.97/4.18] log R5100 from 10GHz core flux
density
61- 65 F5.3 [-] e_R5100-10 [0.002/2] Uncertainty in R5100-10
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- SDSS SDSS identifier
21- 26 F6.4 --- z [0.15/0.6] Spectroscopic redshift
28- 32 F5.2 10-17cW/m2/nm F5100 [1.39/40.4] Flux density at 5100Å
(1)
34- 37 F4.2 10-17cW/m2/nm e_F5100 [0.2/0.3] Uncertainty in F5100 (1)
39- 43 F5.2 mJy/beam 10Core [0.62/57.3]? 10GHz core flux density
45- 48 F4.2 mJy/beam e_10Core [0.01/0.5]? Uncertainty in 10GHzCore
50- 55 F6.2 mJy/beam FIRSTCore [1.42/292]FIRST 1.4GHz core flux
density
57- 60 F4.2 mJy/beam e_FIRSTCore [0.1/2] Uncertainty in FIRSTCore
62- 65 I4 mJy WENSSTot [51/1374] WENSS total flux density
67- 68 I2 mJy e_WENSSTot [5/55] Uncertainty in WENSSTot
70- 75 F6.1 mJy TGSSTot [42.4/2602]? TGSS total flux density
77- 81 F5.1 mJy e_TGSSTot [6.1/261]? Uncertainty in TGSSTot
83- 86 I4 mJy 7CTot [108/2460]? 7C total flux density
88- 90 I3 mJy e_7CTot [17/151]? Uncertainty in 7CTot
92- 95 I4 mJy VLSSrTot [460/4130]? VLSSr total flux density
97- 99 I3 mJy e_VLSSrTot [80/500]? Uncertainty in VLSSrTot
101-106 F6.3 --- SpIndex [-1.4/-0.5]Slope of extended emission
108-112 F5.3 --- e_SpIndex [0.05/0.3] Uncertainty in Sp+Index
114-120 A7 --- Group Assigned group based on radio SED (2)
122-126 F5.2 [-] R-1.4 [-1.19/2.02]? log radio core dominance
from 1.4GHz core flux
128-132 F5.3 [-] e_R-1.4 [0.05/0.3]? Uncertainty in R-1.4
134-138 F5.2 [-] R-10 [-1.5/1.5]? log radio core dominance
from 10GHz core flux
140-144 F5.3 [-] e_R-10 [0.05/0.3]? Uncertainty in R-10
146-149 F4.2 [-] R5100-1.4 [1.28/3.6]? log R5100 from 1.4GHz core
flux density
151-154 F4.2 [-] e_R5100-1.4 [0.01/0.3]? Uncertainty in R5100-1.4
156-159 F4.2 [-] R5100-10 [0.88/3.25]? log R5100 from 10GHz core
flux density
161-164 F4.2 [-] e_R5100-10 [0.01/0.3]? Uncertainty in R5100-10
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Note (1): In units of 1e-17 erg/s/cm2/Angstroms.
Note (2): Quasars are assigned group 1, 2, 2-flag (2f) or 3 on the basis
of their radio spectrum. See section 5 for details.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 21-Mar-2022