J/MNRAS/481/4548 New constraints on the 1.4GHz source counts (Prandoni+, 2018)
The Lockman Hole Project: new constraints on the sub-mJy source counts from
a wide-area 1.4 GHz mosaic.
Prandoni I., Guglielmino G., Morganti R., Vaccari M., Maini A.,
Rottgering H.J.A., Jarvis M.J., Garrett M.A.
<Mon. Not. R. Astron. Soc., 481, 4548-4565 (2018)>
=2018MNRAS.481.4548P 2018MNRAS.481.4548P (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Radio continuum ; Surveys
Keywords: catalogues - surveys - galaxies: evolution - radio continuum: galaxies
Abstract:
This paper is part of a series discussing the results obtained in the
framework of a wide international collaboration - the Lockman Hole
Project - aimed at improving the extensive multiband coverage
available in the Lockman Hole region, through novel deep, wide-area,
multifrequency (60, 150, 350MHz, and 1.4GHz) radio surveys. This
multifrequency, multiband information will be exploited to get a
comprehensive view of star formation and active galactic nucleus
activities in the high-redshift Universe from a radio perspective. In
this paper, we present novel 1.4GHz mosaic observations obtained with
the Westerbork Synthesis Radio Telescope. With an area coverage of
6.6deg2, this is the largest survey reaching an rms noise of
11µJy/beam. In this paper, we present the source catalogue (∼6000
sources with flux densities S≳55µJy (5σ), and we discuss the
1.4GHz source counts derived from it. Our source counts provide very
robust statistics in the flux range 0.1<S<1mJy, and are in excellent
agreement with other robust determinations obtained at lower and
higher flux densities. A clear excess is found with respect to the
counts predicted by the semi-empirical radio sky simulations developed
in the framework of the Square Kilometre Array Simulated Skies
project. A preliminary analysis of the identified (and classified)
sources suggests this excess is to be ascribed to star-forming
galaxies, which seem to show a steeper evolution than predicted.
Description:
We observed the LH region with the WSRT at 1.4GHz, in the period 2006
December-2007 June. The observations covered an area of ∼6.6deg2
(mostly overlapping the Spitzer and Herschel surveys), through
overlapping pointings. A good compromise between uniform sensitivity
and observing efficiency is generally obtained with a mosaic pattern
where pointing spacings, s, are ∼FWHP', where FWHP'=FWHP/sqrt(2),
and FWHP is the full width at half-power of the primary beam (see
Prandoni et al. 2000A&AS..146...31P 2000A&AS..146...31P). For our particular case
FWHP∼36arcmin, and FWHP'∼25.46arcmin. From noise simulations, we got 5
per cent noise variations with s=0.85FWHP' (=22arcmin) and 10 per cent
variations with s=FWHP'. We then decided to cover the 6.6deg2 area
with 16 overlapping pointings, with spacing of 22arcmin in RA and
25arcmin in Dec. Each field was observed for 12h. The primary
calibrator (3C 48) was observed for 15min at the beginning of each 12h
run, and the secondary calibrator (J1035+5628), unresolved on VLBA
scale, was observed for 3min every hour. The data were recorded in 512
channels, organized in eight 20MHz sub-bands, 64 channels each. The
channel width is 312kHz, and the total bandwidth is 160MHz.
The final catalogue lists 5997 sources, including 183
multiple-component sources. Most (90 per cent) are sub-mJy sources.
The full radio catalogue is available in Table 1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 115 6377 The radio catalogue: sample
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- ID Source unique ID number
6 A1 --- f_ID [SABCDT] Catalogue flag (1)
8- 26 A19 --- Name Source name (LHW JHHMMSS+DDMMSS)
28- 29 I2 h RAh Right ascension (J2000)
31- 32 I2 min RAm Right ascension (J2000)
34- 38 F5.2 s RAs Right ascension (J2000)
40 A1 --- DE- Declination sign (J2000)
41- 42 I2 deg DEd Declination (J2000)
44- 45 I2 arcmin DEm Declination (J2000)
47- 51 F5.2 arcsec DEs [0/60] Declination (J2000)
53- 59 F7.3 mJy Speak Source 1.4 GHz peak flux density
61- 67 F7.3 mJy Stot Source 1.4 GHz integrated flux density
69- 74 F6.2 arcsec thetamaj Fitted source major axis (FWHM)
76- 80 F5.2 arcsec thetamin ? Fitted source minor axis (FWHM)
82- 86 F5.1 deg PA []? Fitted position angle (measured N
through E) for the major axis
88- 93 F6.2 arcsec dthetamaj ? Deconvolved major axis of the source. Zero
values refer to unresolved sources
95- 99 F5.2 arcsec dthetamin ? Deconvolved minor axis of the source. Zero
values refer to unresolved sources
101-105 F5.1 deg dPA ? Deconvolved position angle (measured N
through E) for the major axis. Zero values
refer to unresolved sources
107-112 F6.4 mJy rmsloc Source local noise
114 A1 --- flagfit Flag indicating the fitting procedure and
parametrization adopted for the source or
source component (2)
115 A1 --- morph ? Additional morphology flag given in some
specific cases (3)
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Note (1): Flag as follows:
S = Single-component source
A = Indicate a specific component of a multi-component source
B = Indicate a specific component of a multi-component source
C = Indicate a specific component of a multi-component source
D = Indicate a specific component of a multi-component source
T = Global parameters of multi-component source
Note (2): Fitting procedure as follows:
G = Gaussian fitting ok
E = non-Gaussian source
M = multiple-source global parameters
Note (3): Morphology as follows:
* = poor determination of integrated flux
c = complex source, morphology shows deviations from Gaussianity
m = multiple source, morphology shows indications this may be a
multi-component source
n = most probably spurious source due to noise artefact
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 14-Jun-2022