244 research outputs found
A Bayesian approach to high fidelity interferometric calibration II: demonstration with simulated data
In a companion paper, we presented BayesCal, a mathematical formalism for
mitigating sky-model incompleteness in interferometric calibration. In this
paper, we demonstrate the use of BayesCal to calibrate the degenerate gain
parameters of full-Stokes simulated observations with a HERA-like hexagonal
close-packed redundant array, for three assumed levels of completeness of the a
priori known component of the calibration sky model. We compare the BayesCal
calibration solutions to those recovered by calibrating the degenerate gain
parameters with only the a priori known component of the calibration sky model
both with and without imposing physically motivated priors on the gain
amplitude solutions and for two choices of baseline length range over which to
calibrate. We find that BayesCal provides calibration solutions with up to four
orders of magnitude lower power in spurious gain amplitude fluctuations than
the calibration solutions derived for the same data set with the alternate
approaches, and between and times smaller than in the
mean degenerate gain amplitude on the full range of spectral scales accessible
in the data. Additionally, we find that in the scenarios modelled only BayesCal
has sufficiently high fidelity calibration solutions for unbiased recovery of
the 21 cm power spectrum on large spectral scales (). In all other cases, in the completeness regimes
studied, those scales are contaminated
On the nature of infrared-faint radio sources in the SXDF and VLA-VVDS fields
Infrared-Faint Radio Sources (IFRSs) are an unusual class of objects that are
relatively bright at radio wavelengths but have faint or undetected infrared
counterparts even in deep surveys. We identify and investigate the nature of
IFRSs using deep radio (S 100 Jy beam at
5), optical (m 26 - 27.7 at 5), and near-IR
(S 1.3 - 2.0 Jy beam at 5) data
available in two deep fields namely the Subaru X-ray Deep Field (SXDF) and the
Very Large Array - VIMOS VLT Deep Survey (VLA-VVDS) field. In 1.8 deg of
the two fields we identify a total of nine confirmed and ten candidate IFRSs.
We find that our IFRSs are high-redshift radio-loud AGN, with 12/19 sources
having redshift estimates in the range of 1.7 - 4.3, while a limit
of 2.0 is placed for the remaining seven sources. Notably, our study
finds, for the first time, IFRSs with measured redshift 3.0, and also, the
redshift estimates for IFRSs in the faintest 3.6 m flux regime i.e.,
S 1.3 Jy. Radio observations show that our IFRSs
exhibit both compact unresolved as well as extended double-lobe morphologies,
and have predominantly steep radio spectra between 1.4 GHz and 325 MHz. The
non-detection of all but one IFRSs in the X-ray band and the optical-to-MIR
colour (m - m) suggest that a significant fraction
of IFRSs are likely to be hosted in dusty obscured galaxies.Comment: 20 pages, 8 figures, 4 tables, accepted for publication in MNRA
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