J/AJ/142/108 Radio variability of compact, flat-spectrum AGNs (Koay+, 2011)
Dual-frequency observations of 140 compact, flat-spectrum active galactic nuclei
for scintillation-induced variability.
Koay J.Y., Macquart J.-P., Rickett B.J., Bignall H.E., Lovell J.E.J.,
Reynolds C., Jauncey D.L., Pursimo T., Kedziora-Chudczer L., Ojha R.
<Astron. J., 142, 108 (2011)>
=2011AJ....142..108K 2011AJ....142..108K
ADC_Keywords: Active gal. nuclei ; Radio sources
Keywords: galaxies: active - intergalactic medium - ISM: structure -
methods: data analysis - quasars: general - radio continuum: ISM
Abstract:
The 4.9GHz Micro-Arcsecond Scintillation-Induced Variability (MASIV)
Survey detected a drop in interstellar scintillation (ISS) for sources
at redshifts z≳2, indicating an apparent increase in angular
diameter or a decrease in flux density of the most compact components
of these sources relative to their extended emission. This can result
from intrinsic source size effects or scatter broadening in the
intergalactic medium (IGM) in excess of the expected (1+z)1/2
angular diameter scaling of brightness temperature limited sources
resulting from cosmological expansion. We report here 4.9GHz and
8.4GHz observations and data analysis for a sample of 140 compact,
flat-spectrum sources which may allow us to determine the origin of
this angular diameter-redshift relation by exploiting their different
wavelength dependences. In addition to using ISS as a cosmological
probe, the observations provide additional insight into source
morphologies and the characteristics of ISS.
Description:
Observations were carried out over 11 days from 2009 January 15 to 25
using the VLA.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 91 128 List of sources and their properties
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See also:
J/ApJ/689/108 : MASIV survey. II. First four epochs (Lovell+, 2008)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Source IAU name (JHHMM+DDMM),
MASIV JHHMM+DDMM in Simbad
12- 16 F5.1 --- Halpha Hα Intensities from WHAM (Wisconsin
Hα Mapper database; see Haffner et al.
2003, Cat. II/249). Expressed in Rayleigh,
i.e. 1010ph/m2/s.
18- 21 F4.2 Jy S8.4 Mean flux density at 8.4GHz
23- 26 F4.2 Jy S4.9 Mean flux density at 4.9GHz
28- 32 F5.2 --- alpha Source spectral index α
34 A1 --- l_tau8.4 Limit flag on tau8.4
35- 38 F4.1 s tau8.4 ?=- Estimated characteristic timescale of
source variability at 8.4GHz
40- 42 F3.1 s e_tau8.4 ? rms uncertainty on tau8.4
44 A1 --- l_tau4.9 Limit flag on tau4.9
45- 48 F4.1 s tau4.9 ?=- Estimated characteristic timescale of
source variability at 4.9GHz
50- 53 F4.1 s e_tau4.9 ? rms uncertainty on tau4.9
55- 57 F3.1 % m8.4 Raw modulation index at 8.4GHz with no error
subtraction
59- 61 F3.1 % m4.9 Raw modulation index at 4.9GHz with no error
subtraction
63- 69 E7.3 --- D(4d)8.4 4 day structure function at 8.4GHz with
Dnoise subtracted
71- 76 E6.2 --- e_D(4d)8.4 rms uncertainty on D(4d)8.4
78- 84 E7.3 --- D(4d)4.9 4 day structure function at 4.9GHz with
Dnoise subtracted
86- 91 E6.2 --- e_D(4d)4.9 rms uncertainty on D(4d)4.9
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 20-Nov-2012