We present the goals and preliminary results of an unbiased, near-infrared, narrow-band imaging survey of the first galactic quadrant (10 • < l < 65 • ; −1. • 3 < b < +1. • 3). This area includes most of the giant molecular clouds and massive star forming regions in the Northern hemisphere. The survey is centred on the 1-0 S(1) rovibrational line of H 2 , a proven tracer of hot, dense molecular gas in star-forming regions, around evolved stars, and in supernova remnants. The observations complement existing and upcoming photometric surveys (Spitzer-GLIMPSE, UKIDSS-GPS, JCMT-JPS, AKARI, Herschel Hi-GAL, etc.), though we probe a dynamically active component of star formation not covered by these broad-band surveys. Our narrow-band survey is currently more than 60 per cent complete. The median seeing in our images is 0.73 arcsec. The images have a 5σ detection limit of point sources of K ∼ 18 mag and the surface brightness limit is 10 −19 W m −2 arcsec −2 when averaged over our typical seeing. Jets and outflows from both low-and high-mass young stellar objects are revealed, as are new planetary nebulae and -via a comparison with earlier K-band observations acquired as a part of the UKIDSS GPS -numerous variable stars. With their superior spatial resolution, the UWISH2 data also have the potential to reveal the true nature of many of the extended green objects found in the GLIMPSE survey.

Jets and outflows accompany the mass accretion process in protostars and young stellar objects. Using a large and unbiased sample, they can be used to study statistically the local feedback they provide and the typical mass accretion history. Here we analyse such a sample of molecular hydrogen emission‐line objects in the Serpens and Aquila part of the Galactic plane. Distances are measured by foreground star counts with an accuracy of 25 per cent. The resulting spacial distribution and outflow luminosities indicate that our objects sample the formation of intermediate‐mass objects. The outflows are unable to provide a sizeable fraction of energy and momentum to support, even locally, the turbulence levels in their surrounding molecular clouds. The fraction of parsec scale flows is one quarter and the typical dynamical jet age of the order of 104 yr. Groups of emission knots are ejected every 103 yr. This might indicate that low‐level accretion rate fluctuations and not FU‐Ori‐type events are responsible for the episodic ejection of material. Better observational estimates of the FU‐Ori duty cycle are needed.

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.

We discuss 94 Extended Green Objects (EGOs) in the northern Galactic plane cataloged by Cyganowski et al, based on near-infrared narrowband H 2 (2.122 µm) and continuum observations from the United Kingdom Infrared Telescope. This data set is three times larger than our previous study, and is unbiased by preselection. As discussed in the previous paper, the morphologies of the 4.5 µm emission generally resemble those of the near-infrared continuum, but are different from those of the H 2 emission. Of our sample, only 28% of EGOs with H 2 emission show similar morphologies between 4.5 µm and H 2 emission. These results suggest that the 4.5 µm emission mainly comes from scattered continuum from the embedded young stellar object (YSO), and partially from H 2 emission. About half of EGOs are associated with H 2 outflows, if the H 2 outflow incompleteness is considered. The H 2 outflow detection rate for EGOs with K-band detections (61%) is significantly higher than for those without K-band detections (36%). This difference may be due to the fact that both H 2 and K-band emissions are associated with outflows, i.e., H 2 emission and K-band continuum are associated with shocks and outflow cavities, respectively. We also compared the correlation between the H 2 outflows and Class I 44 GHz methanol masers from literature. The methanol masers can be located upstream or downstream of the H 2 outflows and some bright H 2 spots or outflows are not associated with methanol masers, suggesting that methanol masers and H 2 emission trace different excitation conditions.

We used UK Infrared Telescope (UKIRT) near‐infrared (NIR) broad‐band JHK photometry, narrow band imaging of the 1‐0 S(1) molecular hydrogen emission line and mid‐infrared Spitzer IRAC data to investigate the nature of the young cluster Mercer 14. Foreground star counts in decontaminated NIR photometry and a comparison with the Besancon Galaxy Model are performed to estimate the cluster distance. This method yields a distance of 2.5 kpc with an uncertainty of about 10 per cent and can be applied to other young and embedded clusters. Mercer 14 shows clear signs of ongoing star formation with several detected molecular hydrogen outflows, a high fraction of infrared excess sources and an association to a small gas and dust cloud. Hence, the cluster is less than 4 Myr old and has a line‐of‐sight extinction of AK = 0.8 mag. Based on the most massive cluster members we find that Mercer 14 is an intermediate mass cluster with about 500 M⊙.