A near IR imaging survey of high and intermediate-mass young stellar outflow candidates

Watson P. Varricatt$^{1}$, Christopher J.
Davis$^{1}$, Suzanne Ramsay$^{2}$, Stephen P. Todd$^{3}$

$^{1}$Joint Astronomy Centre, 660 N. Aohoku Place, Hilo, HI-96720, USA, $^{2}$European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-87548 Garching bei Muenchen, Germany, $^{3}$UK Astronomy Technology Centre, ROE, Edinburgh, UK

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 $mu$m) and through narrow band filters at the wavelengths of H$_{2}$ ${it{v}}=$1--0 S(1) (2.1218,$mu$m) and Br$gamma$ (2.166,$mu$m) lines. Fifty regions were imaged with a field of view of 2.2$times$2.2,arcmin$^{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-UCH{sc{ii}} phase; accretion and outflows are probably weak when the YSO has advanced to its UCH{sc ii} stage.

Reference: Accepted for publication in MNRAS
Status: Manuscript has been accepted

Weblink: http://adsabs.harvard.edu/abs/2010arXiv1001.2708V


Email: w.varricatt@jach.hawaii.edu