Title: The SCUBA-2 Ambitious Sky Survey: a catalogue of beam-sized sources in the Galactic longitude range 120 to 140,
Abstract: The SCUBA-2 Ambitious Sky Survey (SASSy) is composed of shallow 850-$\umu$m
imaging using the Sub-millimetre Common-User Bolometer Array 2 (SCUBA-2) on the
James Clerk Maxwell Telescope. Here we describe the extraction of a catalogue
of beam-sized sources from a roughly $120\,{\rm deg}^2$ region of the Galactic
plane mapped uniformly (to an rms level of about 40\,mJy), covering longitude
120\degr\,$<$\,\textit{l}\,$<$\,140\degr\ and latitude
$\abs{\textit{b}}$\,$<$\,2.9\degr. We used a matched-filtering approach to
increase the signal-to-noise (S/N) ratio in these noisy maps and tested the
efficiency of our extraction procedure through estimates of the false discovery
rate, as well as by adding artificial sources to the real images. The primary
catalogue contains a total of 189 sources at 850\,$\umu$m, down to a S/N
threshold of approximately 4.6. Additionally, we list 136 sources detected down
to ${\rm S/N}=4.3$, but recognise that as we go lower in S/N, the reliability
of the catalogue rapidly diminishes. We perform follow-up observations of some
of our lower significance sources through small targeted SCUBA-2 images, and
list 265 sources detected in these maps down to ${\rm S/N}=5$. This illustrates
the real power of SASSy: inspecting the shallow maps for regions of 850-$\umu$m
emission and then using deeper targeted images to efficiently find fainter
sources. We also perform a comparison of the SASSy sources with the Planck
Catalogue of Compact Sources and the \textit{IRAS} Point Source Catalogue, to
determine which sources discovered in this field might be new, and hence
potentially cold regions at an early stage of star formation.