1 research outputs found
A near IR imaging survey of intermediate and high-mass young stellar outflow candidates
We have carried out a near-infrared imaging survey of luminous young stellar
outflow candidates using the United Kingdom Infrared Telescope. Observations
were obtained in the broad band K (2.2 mu) and through narrow band filters at
the wavelengths of H_2 v=1--0 S(1) (2.1218 mu) and Br gamma (2.166 mu) lines.
Fifty regions were imaged with a field of view of 2.2 X 2.2 arcmin^2. Several
young embedded clusters are unveiled in our near-infrared images. 76% of the
objects exhibit H_2 emission and 50% or more of the objects exhibit aligned H_2
emission features suggesting collimated outflows, many of which are new
detections. These observations suggest that disk accretion is probably the
leading mechanism in the formation of stars, at least up to late O spectral
types. The young stellar objects responsible for many of these outflows are
positively identified in our images based on their locations with respect to
the outflow lobes, 2MASS colours and association with MSX, IRAS, millimetre and
radio sources. The close association of molecular outflows detected in CO with
the H_2 emission features produced by shock excitation by jets from the young
stellar objects suggests that the outflows from these objects are jet-driven.
Towards strong radio emitting sources, H_2 jets were either not detected or
were weak when detected, implying that most of the accretion happens in the
pre-UCHII phase; accretion and outflows are probably weak when the YSO has
advanced to its UCHII stage.Comment: 64 pages, 53 figures, Accepted for publication in the MNRA