YSO jets in the Galactic Plane from UWISH2: I - MHO catalogue for
  Serpens and Aquila
  Jets and outflows from Young Stellar Objects (YSOs) are important signposts
of currently ongoing star formation. In order to study these objects we are
conducting an unbiased survey along the Galactic Plane in the 1-0S(1) emission
line of molecular hydrogen at 2.122mu using the UK Infrared Telescope. In this
paper we are focusing on a 33 square degree sized region in Serpens and Aquila
(18deg < l < 30deg; -1.5deg < b < +1.5deg).
  We trace 131 jets and outflows from YSOs, which results in a 15 fold increase
in the total number of known Molecular Hydrogen Outflows. Compared to this, the
total integrated 1-0S(1) flux of all objects just about doubles, since the
known objects occupy the bright end of the flux distribution. Our completeness
limit is 3*10^-18Wm^-2 with 70% of the objects having fluxes of less than
10^-17Wm^-2.
  Generally, the flows are associated with Giant Molecular Cloud complexes and
have a scale height of 25-30pc with respect to the Galactic Plane. We are able
to assign potential source candidates to about half the objects. Typically, the
flows are clustered in groups of 3-5 objects, within a radius of 5pc. These
groups are separated on average by about half a degree, and 2/3rd of the entire
survey area is devoid of outflows. We find a large range of apparent outflow
lengths from 4arcsec to 130arcsec. If we assume a distance of 3kpc, only 10% of
all outflows are of parsec scale. There is a 2.6sigma over abundance of flow
position angles roughly perpendicular to the Galactic Plane.
