Deep 3 GHz Observations of the Lockman Hole North with the Very Large
  Array - 1. Source extraction and uncertainty analysis
  This is the first of two papers describing the observations and cataloguing
of deep 3-GHz observations of the Lockman Hole North using the Karl G. Jansky
Very Large Array. The aim of this paper is to investigate, through the use of
simulated images, the uncertainties and accuracy of source-finding routines, as
well as to quantify systematic effects due to resolution, such as source
confusion and source size. While these effects are not new, this work is
intended as a particular case study that can be scaled and translated to other
surveys. We use the simulations to derive uncertainties in the fitted
parameters, as well as bias corrections for the actual catalogue (presented in
Paper 2). We compare two different source-finding routines, OBIT and AEGEAN,
and two different effective resolutions, 8 and 2.75 arcsec. We find that the
two routines perform comparably well, with OBIT being slightly better at
de-blending sources, but slightly worse at fitting resolved sources. We show
that 30 to 70 per cent of sources are missed or fit inaccurately once the
source size becomes larger than the beam, possibly explaining source count
errors in high-resolution surveys. We also investigate the effect of blending,
finding that any sources with separations smaller than the beam size are fit as
single sources. We show that the use of machine-learning techniques can
correctly identify blended sources up to 90 per cent of the time, and
prior-driven fitting can lead to a 70 per cent improvement in the number of
de-blended sources.
