J/MNRAS/458/1057 EoR0 central field source catalog (Offringa+, 2016)
Parametrizing Epoch of Reionization foregrounds: a deep survey of low-frequency
point-source spectra with the Murchison Widefield Array.
Offringa A.R., Trott C.M., Hurley-Walker N., Johnston-Hollitt M.,
McKinley B., Barry N., Beardsley A.P., Bowman J.D., Briggs F., Carroll P.,
Dillon J.S., Ewall-Wice A., Feng L., Gaensler B.M., Greenhill L.J.,
Hazelton B.J., Hewitt J.N., Jacobs D.C., Kim H.-S., Kittiwisit P., Lenc E.,
Line J., Loeb A., Mitchell D.A., Morales M.F., Neben A.R., Paul S.,
Pindor B., Pober J.C., Procopio P., Riding J., Sethi S.K., Shankar N.U.,
Subrahmanyan R., Sullivan I.S., Tegmark M., Thyagarajan N., Tingay S.J.,
Wayth R.B., Webster R.L., Wyithe J.S.B.
<Mon. Not. R. Astron. Soc., 458, 1057-1070 (2016)>
=2016MNRAS.458.1057O 2016MNRAS.458.1057O (SIMBAD/NED BibCode)
ADC_Keywords: Radio sources ; Interferometry ; Radio lines
Keywords: methods: observational - techniques: interferometric -
dark ages, reionization, first stars - radio continuum: general -
radio lines: galaxies
Abstract:
Experiments that pursue detection of signals from the Epoch of
Reionization (EoR) are relying on spectral smoothness of source
spectra at low frequencies. This article empirically explores the
effect of foreground spectra on EoR experiments by measuring
high-resolution full-polarization spectra for the 586 brightest
unresolved sources in one of the Murchison Widefield Array (MWA) EoR
fields using 45h of observation. A novel peeling scheme is used to
subtract 2500 sources from the visibilities with ionospheric and beam
corrections, resulting in the deepest, confusion-limited MWA image so
far. The resulting spectra are found to be affected by instrumental
effects, which limit the constraints that can be set on
source-intrinsic spectral structure. The sensitivity and
power-spectrum of the spectra are analysed, and it is found that the
spectra of residuals are dominated by point spread function sidelobes
from nearby undeconvolved sources. We release a catalogue describing
the spectral parameters for each measured source.
Description:
The observations used in this work have been made as part of the MWA
EoR project. We have used observations that are centred at RA 0°,
Dec. -27°, and recorded between 2013 August and October. The field
around this target is referred to as the MWA EoR0 field - one of three
fields that were selected based on having weak Galactic foregrounds
and passing nearly through zenith at the MWA.
The selected 15 nights are listed in Table 1. Of these 15 nights, 3
nights were not included in the analyses because they show RFI or
unusual calibration solutions. The MWA can observe 30.72MHz
simultaneously. To cover a larger redshift range, a total bandwidth of
138.9-197.7MHz is recorded by observing in two different bands. The
low band covers 138.9-169.6MHz and the high band covers
167.0-197.7MHz. Together these cover the HI 21cm line at
redshifts 6.1-9.2. The observations have a frequency resolution of
40kHz and time resolution of 0.5s.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 77 586 Catalog of sources in the central 10° radius
of the EoR0 field
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- --- [MWAEOR]
7- 20 A14 --- MWAEOR MWAEOR designation (JHHMMSS+DDMMSS)
22- 23 I2 h RAh Right ascension (J2000)
25- 26 I2 min RAm Right ascension (J2000)
28- 31 F4.1 s RAs Right ascension (J2000)
33 A1 --- DE- Declination sign (J2000)
34- 35 I2 deg DEd Declination (J2000)
37- 38 I2 arcmin DEm Declination (J2000)
40- 43 F4.1 arcsec DEs Declination (J2000)
45- 50 F6.3 Jy S168MHz Flux density at 168MHz
52- 56 F5.3 Jy e_S168MHz rms uncertainty on S168MHz
58- 62 F5.2 --- alpha Spectral index alpha at 168MHz (1)
64- 67 F4.2 --- e_alpha rms uncertainty on alpha
69- 73 F5.1 --- beta Spectral curvature beta at 168MHz (1)
75- 77 F3.1 --- e_beta rms uncertainty on beta
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Note (1): we fit each spectrum to a second-order logarithmic polynomial:
logS(nu)=logS0 + alphalog(nu/nu0) + beta(log(nu/nu0))2,
where S0 is the source flux density at the reference frequency nu0=168.3MHz,
alpha the spectral index at frequency nu0 et beta the spectral curvature.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 26-May-2017