J/ApJ/852/48 "X-shaped" radio sources. II. Sample properties (Saripalli+, 2018)
What are "X-shaped" radio sources telling us?
II. Properties of a sample of 87.
Saripalli L., Roberts D.H.
<Astrophys. J., 852, 48 (2018)>
=2018ApJ...852...48S 2018ApJ...852...48S
ADC_Keywords: Galaxies, radio; Radio continuum; Photometry, SDSS; Morphology
Keywords: galaxies: active ; radio continuum: galaxies ; stars: black holes
Abstract:
In an earlier paper, we presented Jansky Very Large Array
multi-frequency, multi-array continuum imaging of a unique sample of
low-axial ratio radio galaxies. In this paper, the second in the
series, we examine the images to learn the phenomenology of how the
off-axis emission relates to the main radio source.
Inversion-symmetric offset emission appears to be bimodal and to
originate from one of two strategic locations: outer ends of radio
lobes (outer-deviation) or from inner ends (inner-deviation). The
latter sources are almost always associated with edge-brightened
sources. With S- and Z-shaped sources being a subset of
outer-deviation sources, this class lends itself naturally to
explanations involving black hole axis precession. Our data allow us
to present a plausible model for the more enigmatic inner-deviation
sources with impressive wings; as for outer-deviation sources these
too require black hole axis shifts, although they also require plasma
backflows into relic channels. Evolution in morphology over time
relates the variety in structures in inner-deviation sources including
XRGs. With features such as non- collinearities, central inner-S
"spine," corresponding lobe emission peaks, double and protruding
hotspots not uncommon, black hole axis precession, drifts, or flips
could be active in a significant fraction of radio sources with
prominent off-axis emission. At least 4% of radio galaxies appear to
undergo black hole axis rotation. Quasars offer a key signature for
recognizing rotating axes. With a rich haul of sources that have
likely undergone axis rotation, our work shows the usefulness of
low-axial ratio sources in pursuing searches for binary supermassive
black holes.
Description:
Roberts+ (2018, J/ApJ/852/47) present every image made of the 99
sources from the Cheung (2007, J/AJ/133/2097) sample, both archival
images from Roberts+ (2015, J/ApJS/220/7), and our Jansky VLA
observations. Altogether there are 236 total intensity images. The
sources were observed over a year from 2016 February through 2017
January at L- and S-band in the A-, B-, and C-arrays. The resolution
we obtained for the images in L-band is 4" (B-array), whereas in
S-band the resolutions range from 2" to 6" (AB-, B-, and C- arrays).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 74 87 Sample sources 1/2
table2.dat 74 87 Sample sources 2/2
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See also:
J/AJ/133/2097 : FIRST "Winged" and X-shaped radio source cand. (Cheung, 2007)
J/ApJS/181/548 : X-shaped radio sources. II. New redshifts (Cheung+, 2009)
J/AJ/146/120 : MOJAVE. X. Parsec-scale kinematics of AGNs (Lister+, 2013)
J/ApJS/220/7 : Abundance of X-shaped radio sources. I. VLA (Roberts+, 2015)
J/ApJ/852/47 : "X-shaped" radio sources. I. VLA imaging (Roberts+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- [C2007] IAU name (JHHMM+DDMM)
12- 13 I2 h RAh Hour of right ascension (J2000)
15- 16 I2 min RAm Minute of right ascension (J2000)
18- 22 F5.2 s RAs Second of right ascension (J2000)
24 A1 --- DE- Sign of declination (J2000)
25- 26 I2 deg DEd Degree of declination (J2000)
28- 29 I2 arcmin DEm Arcminute of declination (J2000)
31- 34 F4.1 arcsec DEs Arcsecond of declination (J2000)
36- 41 F6.4 --- z [0.03/0.9]? Redshift (1)
42 A1 --- f_z [*] *: photometric redshift from SDSS DR12
44- 50 A7 --- Class Morphology
52- 54 I3 arcsec LAS [24/177] Largest angular size along the main
source
56- 59 A4 --- OID? Optical identification? (Q=QSO, BLZ=blazar,
BLRG=broad_line radio galaxy, fnt=faint)
61- 62 A2 --- Rad [YN? ] Radio core?
64- 65 A2 --- XRG? [Y? ] Is the source a candidate "true XRG?"
67- 68 A2 --- Idev? [Y? ] Inner-deviation-type source? (2)
70- 71 A2 --- Odev? [NY? ] Outer-deviation-type source? (3)
73- 74 A2 --- Axis? [Y? ] Axis change?
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Note (1): Redshifts are largely from SDSS DR12, with the remaining ones
from Cheung (2007, J/AJ/133/2097), Cheung+ (2009, J/ApJS/181/548),
and Landt+ (2010MNRAS.408.1103L 2010MNRAS.408.1103L).
Note (2): Sources for which we can trace the origin of the off-axis emission to
the inner ends of lobes we label "I-dev" (which stands for
inner-deviation-type sources).
Note (3): Sources where the origin is traced to outer ends of lobes are labeled
"O-dev" (for outer-deviation-type sources)
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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 --- [C2007] IAU name (JHHMM+DDMM)
12- 16 F5.2 mag rmag [13.8/23.4]? Host-galaxy apparent r magnitude
17 A1 --- u_rmag [?] Uncertainty flag on rmag
19- 31 A13 --- emL Notes on emission lines
33- 35 I3 kpc LLS [23/759]? Projected largest linear size based on
the radio images and the redshifts
36- 38 A3 --- n_LLS Note on LLS (4)
40- 44 F5.2 [W/Hz] log(Pt) [24/27.2]? Log of total radio power at 1.4GHz
46- 60 A15 --- iEnds Gaps between the inner ends of lobes /
whether inner ends have sharp edges (5)
62- 64 F3.1 --- Asym [0/2.1]? Asymmetry: ratio of longer lobe extent
to shorter lobe extent along the main source
65 A1 --- u_Asym [?] Uncertainty flag on Asym
67- 71 A5 --- Hs? Are there hotspots? (6)
73- 74 A2 --- LW? Is the stronger hotspot on the side of the
longer wing?
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Note (4): Note as follows:
* = photometric redshift
GRG = giant radio galaxy
? = Uncertainty flag.
Note (5): 1 and 2 indicate only one or two gaps and edges.
0 indicates not applicable.
Note (6): Code as follows:
2dsim = two dissimilar strength hotspots;
2nsim = two nearly similar strength hotspots;
2sim = two similar strength hotspots;
NA = not available
N = No.
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History:
From electronic version of the journal
References:
Roberts et al. Paper I. 2018ApJ...852...47R 2018ApJ...852...47R J/ApJ/852/47
Saripalli et al. Paper II. 2018ApJ...852...48S 2018ApJ...852...48S This catalog
(End) Emmanuelle Perret [CDS] 23-Jul-2018