J/ApJ/739/76 Pi GHz Sky Survey (PiGSS). II. (Bower+, 2011)
The Allen Telescope Array Pi GHz Sky Survey
II. Daily and monthly monitoring for transients and variability in the Bootes
field.
Bower G.C., Whysong D., Blair S., Croft S., Keating G., Law C.,
Williams P.K.G., Wright M.C.H.
<Astrophys. J., 739, 76 (2011)>
=2011ApJ...739...76B 2011ApJ...739...76B
ADC_Keywords: Radio continuum ; Surveys
Keywords: radio continuum: galaxies - radio continuum: general -
radio continuum: stars - surveys
Abstract:
We present results from daily radio continuum observations of the
Bootes field as part of the Pi GHz Sky Survey (PiGSS). These results
are part of a systematic and unbiased campaign to characterize
variable and transient sources in the radio sky. The observations
include 78 individual epochs distributed over five months at a radio
frequency of 3.1GHz with a median rms image noise in each epoch of
2.8mJy. We produce five monthly images with a median rms of 0.6mJy. No
transient radio sources are detected in the daily or monthly images.
At 15mJy, we set an upper limit (2σ) to the surface density of
one-day radio transients at 0.025deg-2. At 5mJy, we set an upper
limit (2σ) to the surface density of one-month radio transients
at 0.18deg-2. We also produce light curves for 425 sources and
explore the variability properties of these sources. Approximately 20%
of the sources exhibit some variability on daily and monthly
timescales. The maximum rms fractional modulations on the one-day and
one-month timescales for sources brighter than 10mJy are 2 and 0.5,
respectively. The probability of a daily fluctuation for all sources
and all epochs by a factor of 10 is less than 10-4. We compare the
radio to mid-infrared variability for sources in the field and find no
correlation. Finally, we apply the statistics of transient and
variable populations to constrain models for a variety of source
classes.
Description:
The Pi GHz Sky Survey (PiGSS) is a key project of the ATA (Allen
Telescope Array). In Paper I (Bower et al. 2010, Cat. J/ApJ/725/1792),
we presented the survey description, methods in observation, data
reduction, and source identification, and initial results on transient
statistics. Briefly, PiGSS is a 3.1GHz survey of a large area of high
galactic latitude sky conducted synoptically with 100" resolution
and milli-Jansky sensitivity. In this paper, we present daily results
from the Bootes field. These consist of 78 individual epochs over
the five months between 2009 May 20 and 2009 September 29.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 79 425 Source statistics
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See also:
VIII/87 : The Allen Telescope Array 20cm Survey (ATATS). I. (Croft+ 2010)
J/ApJ/725/1792 : Pi Ghz Sky Survey (PiGSS). I. (Bower+, 2010)
J/AJ/123/1784 : 1.4 GHz imaging of the Bootes field (de Vries+, 2002)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- PiGSS Source name (JHHMMSS+DDMMSS)
16- 20 F5.1 mJy S [1/287.5] Primary-beam corrected flux density
at 3.1GHz
22- 24 F3.1 mJy e_S [0.3/5.5] Uncertainty in S
26- 30 F5.2 --- Gain [1/18.12] Primary beam gain
32- 35 F4.2 --- chi2d [0.1/2.66] Daily reduced χ2
37- 41 F5.2 --- chi2m [0.02/13.31] Monthly reduced χ2
43- 50 F8.2 --- sigModd [-1536.23/437.33] Daily RMS fractional modulation
52- 55 F4.2 --- sigModm [0.01/2.98] Monthly RMS fractional modulation
57- 62 F6.2 --- minModd [-13/-0.1] Minimum daily fractional modulation
64- 68 F5.2 --- maxModd [-0.37/12.57] Maximum daily fractional modulation
70- 74 F5.2 --- minModm Minimum monthly fractional modulation
76- 79 F4.2 --- maxModm Maximum monthly fractional modulation
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History:
From electronic version of the journal
References:
Bower et al. Paper I. 2010ApJ...725.1792B 2010ApJ...725.1792B Cat. J/ApJ/725/1792
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 29-Jan-2013