J/A+A/553/A107 Variability of 198 extragalactic radio sources (Chen+, 2013)
Long-term variability of extragalactic radio sources in the
Planck Early Release Compact Source Catalogue.
Chen X., Rachen J.P., Lopez-Caniego M., Dickinson C., Pearson T.J.,
Fuhrmann L., Krichbaum T.P., Partridge B.
<Astron. Astrophys. 553, A107 (2013)>
=2013A&A...553A.107C 2013A&A...553A.107C
ADC_Keywords: Radio sources ; Radio continuum ; BL Lac objects ; Galaxies, radio
Keywords: surveys - radio continuum: galaxies - BL Lacertae objects: general -
quasars: general - galaxies: individual
Abstract:
Combining measurements taken using the Wilkinson Microwave Anisotropy
Probe (WMAP) from 2001 to 2008 with measurements taken using Planck
from 2009 to 2010, we investigate the long-term flux density
variability of extragalactic radio sources selected from the Planck
Early Release Compact Source Catalogue. The single-year,
single-frequency WMAP maps are used to estimate yearly-averaged flux
densities of the sources in the four WMAP bands: Ka (33GHz),
Q (41GHz), V (61GHz), and W (94GHz). We identify 82, 67, 32, and 15
sources respectively as variable at greater than 99% confidence level
in these four bands. The amplitudes of variation are comparable
between bands, and are not correlated with either the flux densities
or the spectral indices of the sources. The number counts of WMAP
Ka-band sources are stable from year to year despite the fluctuation
caused by individual source variability. Most of our sources show
strong correlation in variability between bands. Almost all the
sources that show variability are blazars. We have attempted to fit
two simple, four-parameter models to the time-series of 32 sources
showing correlated variability at multiple frequencies - a long-term
flaring model and a rotating-jet model. We find that 19 sources (60%)
can be fit with the simple rotating-jet model, and ten of these also
fit the simple long-term flaring model. The remaining 13 sources (40%)
show more complex variability behaviour that is not consistent with
either model. Extended radio galaxies in our sample show no sign of
variability, as expected, with the exception of Pictor A for which we
report evidence for a millimetre flare lasting between 2002 and 2010.
Description:
WMAP single year Ka, Q, V and W band flux densities from 2001 to 2008,
together with the Planck ERCSC flux densities interpolated to the
center frequencies of the WMAP bands, are presented for 198
extragalactic radio sources selected from the ERCSC.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 161 792 Flux densities at WMAP Ka, Q, V, and W band for the
198 extragalactic radio sources selected from the
Planck Early Release Compact Source Catalogue (ERCSC)
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See also:
VIII/88 : Planck Early Release Compact Source Catalogue (Planck, 2011)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- JName J2000 name of the source
12- 19 A8 --- OName Commonly known name or B1950 name
21- 27 F7.3 deg GLON Galactic longitude (J2000)
30- 36 F7.3 deg GLAT Galactic latitude (J2000)
39- 42 A4 --- Type Object type if known: AGN, BLL, GAL, SBG (star
burst galaxy) or FSRQ (Flat Radio Spectrum QSO)
45- 46 A2 --- Band WMAP frequency band (Ka, Q, V or W) (1)
49- 53 F5.2 Jy WMAP1 Flux density measured on WMAP first year map
56- 59 F4.2 Jy e_WMAP1 Uncertainty on WMAP1 flux density
62- 66 F5.2 Jy WMAP2 Flux density measured on WMAP second year map
69- 72 F4.2 Jy e_WMAP2 Uncertainty on WMAP2 flux density
75- 79 F5.2 Jy WMAP3 Flux density measured on WMAP third year map
82- 85 F4.2 Jy e_WMAP3 Uncertainty on WMAP3 flux density
88- 92 F5.2 Jy WMAP4 Flux density measured on WMAP fourth year map
95- 98 F4.2 Jy e_WMAP4 Uncertainty on WMAP4 flux density
101-105 F5.2 Jy WMAP5 Flux density measured on WMAP fifth year map
108-111 F4.2 Jy e_WMAP5 Uncertainty on WMAP5 flux density
114-118 F5.2 Jy WMAP6 Flux density measured on WMAP sixth year map
121-124 F4.2 Jy e_WMAP6 Uncertainty on WMAP6 flux density
127-131 F5.2 Jy WMAP7 Flux density measured on WMAP seventh year map
134-137 F4.2 Jy e_WMAP7 Uncertainty on WMAP7 flux density
140-144 F5.2 Jy ERCSC Planck ERCSC flux density (2)
147-150 F4.2 Jy e_ERCSC Uncertainty on ERCSC flux density
153-158 F6.2 --- Vrms ? Variability index (3)
161 A1 --- V [Vv] Strongly (V) or moderately (v) variable (4)
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Note (1): WMAP frequency bands:
Ka = 30GHz (10.0mm)
Q = 40GHz (7.5mm)
V = 60GHz (5.0mm)
W = 90GHz (3.3mm)
Note (2): These are the ERCSC flux extrapolated to the center frequencies
of WMAP Ka, Q, V, and W-band.
Note (3): This field is left blank when a timeline is not included in the
variability analysis. Negative values indicate that the flux density
fluctuation level is less than the noise level.
Note (4): Notes as follows:
V = denotes strongly variable sources (>99% confidence) at a given frequency
v = denotes moderately variable sources (>95% confidence) at a given frequency
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Acknowledgements:
Xi Chen, xchen(at)ipac.caltech.edu
(End) Xi Chen [IPAC, Caltech, USA], Patricia Vannier [CDS] 31-Jan-2013