J/MNRAS/494/923 WISE properties of AGNs from the AT20G survey (Chhetri+, 2020)
WISE mid-infrared properties of compact active galactic nuclei selected from
the high radio frequency AT20G survey.
Chhetri R., Kimball A., Ekers R.D., Mahony E.K., Sadler E.M., Jarrett T.
<Mon. Not. R. Astron. Soc., 494, 923-940 (2020)>
=2020MNRAS.494..923C 2020MNRAS.494..923C (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Galaxies, IR ; Galaxies, photometry ;
Radio sources ; Redshifts ; Cross identifications ; Surveys
Keywords: catalogues - galaxies: active - galaxies: distances and redshifts -
quasars: general - infrared: galaxies - infrared: general
Abstract:
Past studies of compact active galactic nuclei (AGNs), the dominant
population at high radio frequencies, selected them using flat
spectral index criteria. This biases the sample due to the steepening
of AGN spectra at high radio frequencies. We improve upon this by
selecting 3610 compact AGNs using their angular size information
(~<0.15arcsec scale) from the Australia Telescope 20GHz (AT20G)
high-angular resolution catalogue. We cross-match these against the
Wide-field Infrared Survey Explorer AllWISE catalogue and present a
catalogue with 3300 (91 per cent) matches, 91 (3 per cent) rejects,
and 219 (6 per cent) non-detections that are excellent high-redshift
candidates. Of the matched compact AGNs, 92 per cent exhibit QSO
mid-infrared colours (W1-W2>0.5). Therefore, our sample of high
frequency compact sources has a very high rate of identification with
mid-infrared QSOs. We find counterparts for 88 per cent of 387 compact
steep-spectrum (CSS) sources in the AT20G survey, 82±5 per cent of
which exhibit QSO mid-infrared colours and have moderate redshifts
(zmedian=0.82), while those dominated by host galaxy colours in
mid-infrared have lower redshifts (zmedian=0.13). The latter
classified into late- and early-type galaxies using their mid-infrared
colours shows a majority (68±4 per cent) have colours characteristic
of late-type galaxies. Thus, we find that a larger fraction of these
CSS sources are embedded in hosts with higher gas densities than
average early-type galaxies. We compare mid-infrared colours of our
AGNs against those reported for AGNs primarily selected using
non-radio techniques. This shows that mid-infrared SED of high
frequency selected compact radio AGN is comparatively less red,
possibly due to contributions from their hosts.
Description:
The WISE survey is very sensitive to galactic thermal sources. Hence,
in order to avoid possible incorrect matches of our compact source
sample with galactic sources, we excluded sources with Galactic
latitude |b|<10° from the AT20G high-angular-resolution catalogue.
The remaining 3610 compact AGNs form our parent sample for
cross-matching. Of these, 91 nearby AT20G sources have been included
in Sadler et al. (2014MNRAS.438..796S 2014MNRAS.438..796S, Cat. J/MNRAS/438/796) using the
WISE All-Sky catalogue (Cutri et al. 2012wise.rept....1C, Cat.
II/311). The All-Sky catalogue has been updated with the AllWISE
catalogue. Therefore, for these sources we used the WISE counterparts
provided in Sadler et al. (2014MNRAS.438..796S 2014MNRAS.438..796S, Cat. J/MNRAS/438/796)
but obtained updated AllWISE photometry from the WISE consortium (T.
Jarrett). We then cross-matched the remaining 3519 AT20G compact AGNs
against the AllWISE catalogue. Of these, 2844 (79±2 per cent)
sources have optical identifications as published in Mahony et al.
(2011MNRAS.417.2651M 2011MNRAS.417.2651M, Cat. J/MNRAS/417/2651). These identifications
are based on the digitized UK Schmidt Telescope survey in the
SuperCOSMOS data base (Hambly et al. 2001MNRAS.326.1279H 2001MNRAS.326.1279H), and
redshift information were found from either the 6dF Galaxy Survey or
the literature (Jones et al. 2010ApJ...713..970A 2010ApJ...713..970A, Cat. J/ApJ/713/970).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 249 3610 AT20G compact AGNs cross-matched with the
AllWISE mid-infrared catalogue
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See also:
J/MNRAS/434/956 : AT20G high-angular-resolution catalogue (Chhetri+, 2013)
J/MNRAS/438/796 : Local radio-galaxy population at 20GHz (Sadler+, 2014)
J/MNRAS/417/2651 : AT20G-optical catalogue (Mahony+, 2011)
II/328 : AllWISE Data Release (Cutri+ 2013)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name AT20G source name (JHHMMSS+DDMMSS)
16- 17 I2 h RAh Right ascension (J2000)
19- 20 I2 min RAm Right ascension (J2000)
22- 26 F5.2 s RAs Right ascension (J2000)
28 A1 --- DE- Declination sign (J2000)
29- 30 I2 deg DEd Declination (J2000)
32- 33 I2 arcmin DEm Declination (J2000)
35- 38 F4.1 arcsec DEs Declination (J2000)
40- 44 I5 mJy S20 20GHz flux density from the AT20G survey
46- 49 I4 mJy S8.6 ? 8.6GHz flux density from the AT20G survey
51- 54 I4 mJy S4.8 ? 4.8GHz flux density from the AT20G survey
56- 60 F5.2 --- alpha ? Spectral index between 1 (either NVSS or
SUMSS) and 4.8GHz
62- 65 F4.2 --- Vis 6-km visibility
67- 70 F4.2 --- e_Vis Error on Vis
72- 73 A2 --- Flag Flag from AT20G high-angular-resolution
catalogue (1)
75- 76 I2 h RAoh ? Right ascension of optical counterpart
(J2000)
78- 79 I2 min RAom ? Right ascension of optical counterpart
(J2000)
81- 85 F5.2 s RAos ? Right ascension of optical counterpart
(J2000)
87 A1 --- DEo- Declination sign of optical counterpart
(J2000)
88- 89 I2 deg DEod ? Declination of optical counterpart (J2000)
91- 92 I2 arcmin DEom ? Declination of optical counterpart (J2000)
94- 97 F4.1 arcsec DEos ? Declination of optical counterpart (J2000)
99- 102 F4.1 mag Bmag ? B-band magnitude from SuperCOSMOS
104- 107 F4.1 mag Rmag ? R-band magnitude from SuperCOSMOS
109- 113 F5.3 --- z ? Redshift
115- 116 A2 --- OptFlag Optical flag from Mahony et al.
(2011MNRAS.417.2651M 2011MNRAS.417.2651M, Cat. J/MNRAS/417/2651)
(2)
118- 119 A2 --- match Match flag (3)
121- 139 A19 --- OName WISEA designation of accepted counterpart
(JHHMMSS.ss+DDMMSS.s)
141- 142 I2 h RAwh ? Right ascension of WISEA counterpart (J2000)
144- 145 I2 min RAwm ? Right ascension of WISEA counterpart (J2000)
147- 151 F5.2 s RAws ? Right ascension of WISEA counterpart (J2000)
153 A1 --- DEw- Declination sign of WISEA counterpart (J2000)
154- 155 I2 deg DEwd ? Declination of WISEA counterpart (J2000)
157- 158 I2 arcmin DEwm ? Declination of WISEA counterpart (J2000)
160- 163 F4.1 arcsec DEws ? Declination of WISEA counterpart (J2000)
165- 169 F5.1 arcsec dRAw ? Offset in RA in WISEA counterpart position
from AT20G position
171- 175 F5.1 arcsec dDEw ? Offset in Dec in WISEA counterpart position
from AT20G position
177- 182 F6.3 mag W1mag ? WISE W1 (3.4um) band magnitude
184- 188 F5.3 mag e_W1mag ? Error on W1mag
190- 195 F6.3 mag W2mag ? WISE W2 (4.6um) band magnitude
197- 201 F5.3 mag e_W2mag ? Error on W2mag
203- 208 F6.3 mag W3mag ? WISE W3 (12um) band magnitude
210- 214 F5.3 mag e_W3mag ? Error on W3mag
216- 221 F6.3 mag W4mag ? WISE W4 (22um) band magnitude
223- 227 F5.3 mag e_W4mag ? Error on W4mag
229- 232 A4 --- MagType Magnitude type (4)
234- 237 A4 --- Quality ? Quality flag for magnitude (5)
239- 242 A4 --- ccFlag Contamination and confusion flag (6)
244- 247 A4 --- Phqual Photometric quality flag from WISE catalogue
(7)
249 A1 --- ExtFlag ? Extended source flag from WISE catalogue (8)
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Note (1): Flag as follows:
b = large and extended in AT20G main catalogue
e = extended in AT20G main catalogue
l = source has no counterpart in either NVSS or SUMSS
m = part of Magellanic clouds
v = more than two 6-km visibility values are present
Note (2): Flag as follows:
b = blended source
c = source is in a field too crowded to make an identification
o = source is slightly offset from radio position but still within 3.5arcsec
u = unreliable optical magnitude
Note (3): Flag as follows:
Aa = cross-match accepted automatically
Am = cross-match obtained manually
As = taken from Sadler et al. (2014MNRAS.438..796S 2014MNRAS.438..796S, Cat. J/MNRAS/438/796)
Av = cross-match accepted after visual inspection
Rb = cross-match rejected as counterpart is blended
Rv = cross-match rejected after visual inspection
Note (4): Each letter/number represents magnitude type for each band from left
(W1) to right (W4). Type as follows:
1 = magnitude is obtained from aperture 1
2 = magnitude is obtained from aperture 2
3 = magnitude is obtained from aperture 3
4 = magnitude is obtained from aperture 4
5 = magnitude is obtained from aperture 5
g = gmag
m = magnitude was obtained manually
p = profile-fit magnitude
Note (5): Each number represents magnitude quality for each band from left (W1)
to right (W4). Quality as follows:
0 = excellent detection
1 = source photometry is upper limit
2 = source photometry should be used with caution
3 = bad photometry - do not use
Note (6): Each number represents cc flag for each band from left (W1) to right
(W4). Flag as follows:
D,d = affected by diffraction spike
P,p = affected by persistency left by a bright image
H,h = affected by halo from a nearby bright source
O,o = affected by optical ghost due to a nearby bright source
0 = source unaffected by known artifacts
Note (7): Each letter represents teh photometric quality for each band from left
(W1) to right (W4). Flag as follows:
A = SNR≥10
B = 3<SNR<10
C = 2<SNR<3
U = upper limit on magnitude
X = profile-fit measurement not possible
Note (8): Flag as follows:
0 = not extended
1 = χ2≥3.0 in any band, suspected to be resolved or confused
2 = within isophotal extent of a 2MASS extended source
3 = as above and χ2≥3.0 in any band
4 = identically associated with a 2MASS extended source
5 = as above and also χ2≥3.0 in any band
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 23-May-2023