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Keywords:

  • stars: formation;
  • stars: winds, outflows;
  • ISM: individual objects: Galactic plane;
  • ISM: jets and outflows

ABSTRACT

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 1–0 S(1) emission line of molecular hydrogen at 2.122 μm using the United Kingdom Infrared Telescope. In this paper, we are focusing on a 33-deg2-sized region in Serpens and Aquila (18° < l < 30°; − 1°.5 < b < +1°.5).

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 1–0 S(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 × 10−18 W m−2 with 70 per cent of the objects having fluxes of less than 10−17 W m−2.

Generally, the flows are associated with giant molecular cloud complexes and have a scaleheight of 25–30 pc 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 three to five objects, within a radius of 5 pc. These groups are separated on average by about half a degree, and two-thirds of the entire survey area is devoid of outflows. We find a large range of apparent outflow lengths from 4 to 130 arcsec. If we assume a distance of 3 kpc, only 10 per cent of all outflows are of parsec scale. There is a 2.6σ overabundance of flow position angles roughly perpendicular to the Galactic plane.