J/AJ/151/74 VLA/VLBA obscured radio-loud active galactic nuclei (Yan+, 2016)
Invisible active galactic nuclei.
II. Radio morphologies and five new H I 21cm absorption line detectors.
Yan T., Stocke J.T., Darling J., Momjian E., Sharma S., Kanekar N.
<Astron. J., 151, 74 (2016)>
=2016AJ....151...74Y 2016AJ....151...74Y (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Radio continuum ; Redshifts ; Spectroscopy ;
Morphology ; Interferometry
Keywords: quasars: absorption lines - radio continuum: galaxies
Abstract:
This is the second paper directed toward finding new highly redshifted
atomic and molecular absorption lines at radio frequencies. To this
end, we selected a sample of 80 candidates for obscured radio-loud
active galactic nuclei (AGNs) and presented their basic
optical/near-infrared (NIR) properties in Yan et al. 2012AJ....144..124Y 2012AJ....144..124Y.
In this paper, we present both high-resolution radio continuum images
for all of these sources and H I 21 cm absorption spectroscopy for a
few selected sources in this sample. A-configuration 4.9 and 8.5 GHz
Very Large Array continuum observations find that 52 sources are
compact or have substantial compact components with size <0.5" and
flux densities >0.1 Jy at 4.9 GHz. The 36 most compact sources were
then observed with the Very Long Baseline Array at 1.4 GHz. One
definite and 10 candidate Compact Symmetric Objects (CSOs) are newly
identified, which is a detection rate of CSOs ∼three times higher than
the detection rate previously found in purely flux-limited samples.
Based on possessing compact components with high flux densities, 60 of
these sources are good candidates for absorption-line searches.
Twenty-seven sources were observed for H I 21 cm absorption at their
photometric or spectroscopic redshifts with only six detections (five
definite and one tentative). However, five of these were from a small
subset of six CSOs with pure galaxy optical/NIR spectra (i.e., any AGN
emission is obscured) and for which accurate spectroscopic redshifts
place the redshifted 21 cm line in a radio frequency intereference
(RFI)-free spectral "window" (i.e., the percentage of H I 21 cm
absorption-line detections could be as high as ∼90% in this sample).
It is likely that the presence of ubiquitous RFI and the absence of
accurate spectroscopic redshifts preclude H I detections in similar
sources (only 1 detection out of the remaining 22 sources observed, 13
of which have only photometric redshifts); that is, H I absorption may
well be present but is masked by the RFI. Future searches for highly
redshifted H I and molecular absorption can easily find more distant
CSOs among bright, "blank field" radio sources, but will be severely
hampered by an inability to determine accurate spectroscopic redshifts
due to their lack of rest-frame UV continuum.
Description:
The specific selection criteria for the sample presented in Yan et al.
2012AJ....144..124Y 2012AJ....144..124Y (Paper I) include the presence of an SDSS r-band
optical counterpart within 1.5" of a bright (≥0.5 Jy) FIRST radio
source position and characteristics of the optical counterpart that
favor it being a late-type galaxy. Of the 82 objects originally selected
(Paper I), 2 are nearby galaxies at z<0.05 (J1352+3126 and J1413-0312)
and are excluded from our discussion in this paper.
Except when archive data were available, we observed all the sources
at 4.9 and 8.5 GHz using the VLA of NRAO in its most extended
A-configuration (VLA-A; project # AY0052). Overall, we obtained data
for 35 sources at both frequencies, 14 at 4.9 GHz only, and 8 at 8.5 GHz
only. Our data were taken during 2007 June to August in the transitional
period from VLA to Expanded VLA (EVLA; currently the Karl G. Jansky VLA).
We used the VLBA to obtain 1.4 GHz images for sources that are unresolved
or have compact components in VLA-A images (project # BY0020). Overall,
36 sources were observed in 2009 December and 2010 January.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 75 81 Observing Summary
table2.dat 97 80 Summary of Radio Galaxy Properties
table10.dat 98 80 Basic Observing Results
table11.dat 79 123 VLA 4.9 GHz Gaussian Fit Results
table12.dat 79 102 VLA 8.5 GHz Gaussian Fit Results
table13.dat 79 76 VLBA 1.4 GHz Gaussian Fit Results
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See also:
VIII/60 : Interferometer phase calibration sources (Patnaik+ 1998)
VIII/72 : CLASS survey of radio sources (Myers+, 2003)
J/A+A/369/380 : CSS/GPS radio sources VLA observations (Fanti+, 2001)
J/A+A/416/35 : Radio Emission from VLA FIRST Survey AGN (Wadadekar, 2004)
J/ApJ/658/203 : VLBA imaging and polarimetry survey at 5GHz (Helmboldt+, 2007)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Object name (JHHMM+DDMM)
12- 23 A12 --- Radio Radio name
25- 35 A11 "date" Date4.9 Date of observation at 4.9 GHz
37- 38 I2 --- r_Date4.9 [1/15]? Reference for Date4.9 (1)
40- 50 A11 "date" Date8.5 Date of observation at 8.5 GHz
52- 53 I2 --- r_Date8.5 [1/17]? Reference for Date8.5 (1)
55- 65 A11 "date" DateVLBI Date of VLBI observation
67- 68 I2 --- r_DateVLBI [1/19]? Reference for DateVLBI (1)
70- 75 A6 --- Note Note(s) (2)
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Note (1): Reference as follows:
1 = This work (VLA project AY0052 and VLBA project BY 0020);
2 = VLA project AA052;
3 = VLA project AA073;
4 = VLA project AB375;
5 = VLA project AB568;
6 = VLA project AB611;
7 = VLA project AB922;
8 = VLA project AH167;
9 = VLA project AS704;
10 = Cai et al. (2002A&A...381..401C 2002A&A...381..401C);
11 = Chambers et al. (1996ApJS..106..247C 1996ApJS..106..247C);
12 = Dallacasa et al. (2002A&A...389..126D 2002A&A...389..126D);
13 = Fanti et al. (2001, J/A+A/369/380);
14 = Helmboldt et al. (2007, J/ApJ/658/203);
15 = Lehar et al. (1997AJ....114...48L 1997AJ....114...48L);
16 = Myers et al. (2003, Cat. VIII/72);
17 = Patnaik et al. (1992, Cat. VIII/60);
18 = Peck & Taylor (2000ApJ...534...90P 2000ApJ...534...90P);
19 = Perlman et al. (2002AJ....124.2401P 2002AJ....124.2401P).
Note (2): Note as follows:
N1 = No flux calibration on the VLA-A 4.9 GHz image;
N2 = No flux calibration on the VLA-A 8.5 GHz image;
N3 = Not detected on the VLA-A 4.9 GHz image;
N4 = Not detected on the VLBA 1.4 GHz image;
N5 = All data are flagged on the VLA-A 4.9 GHz image.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Object name (JHHMM+DDMM)
12- 16 F5.3 --- z [0.122/3.200]? Redshift
17 A1 --- n_z [*abc] Note on z (1)
18 A1 --- u_z [:] Uncertainty flag on z
20- 24 A5 --- SEDType Optical+NIR SED type from Yan et al.
(2012AJ....144..124Y 2012AJ....144..124Y) (2)
26- 27 A2 --- GType Hubble type for pure "G"-type objects in column
"SEDType" (3)
29- 32 F4.2 Jy S365MHz [0.25/8.31] Flux density at 365 MHz
34- 37 F4.2 Jy S1.4GHz [0.32/4.86] Flux density at 1.4 GHz
39- 42 F4.2 Jy S4.9CHz [0.07/3.09] Flux density at 4.9 GHz
44- 47 F4.2 --- alphal [0.02/1.28] Low-frequency spectral index,
αl, between 365 MHz and 1.4 GHz
49- 53 F5.2 --- alphah [-1.41/0.37] High-frequency spectral index,
αh, between 1.4 and 4.9 GHz
55- 57 A3 --- Class Radio spectral classification (4)
58 A1 --- n_Class [a] Note on Class (5)
59 A1 --- u_Class [:] Uncertainty flag on Class
61- 65 F5.3 arcsec LAS [0.002/6.6] Largest angular size between major
components
66 A1 --- u_LAS [:] Uncertainty flag on LAS
68- 73 F6.3 kpc LLS [0.014/45.7] Largest linear size
74 A1 --- n_LLS [≲] Note on LLS (6)
76- 79 F4.2 GHz Freq [1.4/8.5] Frequency with which the LAS and LLS
are measured
81- 85 A5 --- Tel Telescope with which the LAS and LLS are
measured
87- 92 A6 --- Morph Radio source morphological classification (7)
94 A1 --- Eval1 [YN] Whether the object remains a good
candidate for an absorption-line search at
radio frequencies (Y=Yes, N=No)
96- 97 A2 --- Eval2 Whether the object is an intervening system (I)
or candidate (I:)
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Note (1): Note as follows:
* = Photometric redshift fit by its optical+NIR SED in Yan et al.
(2012AJ....144..124Y 2012AJ....144..124Y);
a = The redshift listed is for a background radio source that has an SDSS
detected Galaxy in the foreground;
b = The redshift listed is for a background radio source that is
gravitationally lensed by a foreground Galaxy at z=0.349;
c = This is an intervening system with a foreground Galaxy at z=0.206. The
radio source redshift is unknown.
Note (2): The optical+NIR SEDs were divided into four classes in Yan et al.
(2012AJ....144..124Y 2012AJ....144..124Y):
G = Pure galaxy;
G+Q = Galaxy with a quasar signature in the bluer bands;
Q = Quasar;
Q+abs = Quasar with extinction signatures in the bluer bands.
Note (3): We fit the G-type objects with template spectra of five Hubble types
(E, S0, Sa, Sb, and Sc), and give the best-fit Hubble types.
Note (4): Classification as follows:
SS = Steep Spectrum;
FS = Flat Spectrum;
USS = Ultra-Steep Spectrum;
GPS = Giga-Hertz Peak Spectrum.
Note (5): Note as follows:
a = The classification has been modified using additional information to the
spectral indices in columns "alphal" and "alphah".
Note (6): Note as follows:
∼ = A photometric redshift is used;
< = z=1.6 is used to obtain the largest size possible.
Note (7): Morphological classification as follows:
CPLX = Complex;
CJ = Core-jet;
GA = Gravitational arc;
PS = Point source;
SL = Single lobe;
CSO = Compact symmetric object;
CSO: = CSO candidate;
LSO = Large symmetric object;
MSO = Medium-size symmetric object.
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Byte-by-byte Description of file: table10.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Object name (JHHMM+DDMM)
12- 15 F4.2 arcsec MajAxis4.9 [0.42/0.97]? Major axis size at 4.9 GHz
17- 20 F4.2 arcsec MinAxis4.9 [0.40/0.49]? Minor axis size at 4.9 GHz
22- 26 F5.1 deg PA4.9 [-89.4/87.8]? Position angle of the
restored beam at 4.9 GHz
28- 31 F4.2 mJy/beam rms4.9 [0.12/0.77]? Map rms (σ) in
the vicinity of the source at 4.9 GHz
32 A1 --- n_rms4.9 [*] Note on rms4.9 (G1)
34- 38 F5.1 mJy/beam Smax4.9 [21.6/578.7]? Maximum flux density in
the map at 4.9 GHz
39 A1 --- n_Smax4.9 [*] Note on Smax4.9 (G1)
41- 44 F4.2 arcsec MajAxis8.5 [0.24/0.74]? Major axis size at 8.5 GHz
46- 49 F4.2 arcsec MinAxis8.5 [0.23/0.42]? Minor axis size at 8.5 GHz
51- 56 F6.1 deg PA8.5 [-175.8/174.3]? Position angle of the
restored beam at 8.5 GHz
58- 61 F4.2 mJy/beam rms8.5 [0.06/0.71]? Map rms (σ) in the
vicinity of the source at 8.5 GHz
62 A1 --- n_rms8.5 [*] Note on rms8.5 (G1)
64- 68 F5.1 mJy/beam Smax8.5 [10.0/605.1]? Maximum flux density in
the map at 8.5 GHz
69 A1 --- n_Smax8.5 [*] Note on Smax8.5 (G1)
71- 75 F5.2 arcsec MajAxis1.4 [8.12/61.82]? Major axis size at 1.4 GHz
77- 81 F5.2 arcsec MinAxis1.4 [4.86/55.91]? Minor axis size at 1.4 GHz
83- 87 F5.1 deg PA1.4 [-33.9/78.2]? Position angle of the
restored beam at 1.4 GHz
89- 92 F4.2 mJy/beam rms1.4 [0.11/3.50]? Map rms (σ) in the
vicinity of the source at 1.4 GHz
94- 98 F5.1 mJy/beam Smax1.4 [7.5/401.1]? Maximum flux density in
the map at 1.4 GHz
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Byte-by-byte Description of file: table11.dat table12.dat table13.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Object name (JHHMM+DDMM)
12- 13 A2 --- m_Name Multiplicity index on Name
15- 16 I2 h RAh ? Hour of Right Ascension (J2000) (1)
18- 19 I2 min RAm ? Minute of Right Ascension (J2000)
21- 27 F7.4 s RAs ? Second of Right Ascension (J2000)
29 A1 --- DE- ? Sign of the Declination (J2000)
30- 31 I2 deg DEd ? Degree of Declination (J2000)
33- 34 I2 arcmin DEm ? Arcminute of Declination (J2000)
36- 41 F6.3 arcsec DEs ? Arcsecond of Declination (J2000)
43- 47 F5.1 mJy/beam Speak [0.4/650.6] Peak flux density
48 A1 --- n_Speak [*] Note on Speak (not in table 13) (G1)
50- 54 F5.1 mJy Sint [1.8/929.4] Integrated flux density
55 A1 --- n_Sint [*] Note on Sint (not in table 13) (G1)
57- 62 F6.2 arcsec MajAxis [0.03/109] Deconvolved major axis
64- 68 F5.2 arcsec MinAxis [0.00/63] Deconvolved minor axis
70- 74 F5.1 deg PA [0.1/179.2] Position angle of the Gaussian
component
76- 79 F4.1 --- alpha [-3.6/3.1]? Spectral index (α)
calculated between 4.9 and 8.5 GHz
(only in table 12)
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Note (1): No position in Table 12.
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Global notes:
Note (G1): Note as follows:
* = Flux densities lack accurate flux calibrations. See Table 1 for details.
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History:
From electronic version of the journal
References:
Yan et al. Paper I. 2012AJ....144..124Y 2012AJ....144..124Y
(End) Tiphaine Pouvreau [CDS] 16-Mar-2018