A characterization of young stellar objects in BOK globules: Infrared imaging, spectral energy distributions, and molecular outflows

Details A characterization of young stellar objects in BOK globules: Infrared imaging, spectral energy distributions, and molecular outflows A characterization of young stellar objects in BOK globules: Infrared imaging, spectral energy distributions, and molecular outflows

Sep 1993

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993phdt.........1y&link_type=abstract

Ph.D. Thesis Boston Univ., MA.

Astronomy and Astrophysics

Astronomy

4

Infrared Astronomy Satellite, Infrared Imagery, Molecular Clouds, Sky Surveys (Astronomy), Star Formation, Stellar Evolution, Infrared Photometry, Pre-Main Sequence Stars, Reflection Nebulae, Stellar Luminosity

Scientific paper

A large-scale observational study of star formation in Bok globules is presented. A sample of 248 optically selected, small molecular clouds (mostly Bok globules) was probed using IRAS co-added images to search for associated young stellar objects (YSO's). Fifty-seven of the globules show evidence for a total of 72 point sources near locations of local dust heating. A sub-sample of 41 globules was observed, in the CO J = 1-0 line, to search for molecular outflows associated with the YSO's. Outflows were found in about one-third of the sample (14 of 41). The presence of an outflow was found to be correlated with the value of the IRAS-based spectral index (between 12 and 25 microns) of the YSO's. A near-infrared imaging survey of 34 globules containing YSO-candidates was conducted in the J, H, and K bands using infrared arrays. Eleven YSO-candidates displayed near-infrared nebulosities. This group of objects, when ordered by their values of the 12/25 microns spectral index, seems to form an evolutionary sequence, from younger objects with negative (red) indices and whose nebulosities are brighter in the K-band, to objects in later stages of pre-main-sequence evolution with positive (bluer) indices and whose nebular emission is brighter in the J-band. Comparison of the morphology of the infrared nebulae with the corresponding CO outflow morphology supports the idea that infrared reflection nebulae, seen at 2.2 microns, are good morphological tracers of CO mass outflow, and that CO outflows occur during the earliest YSO phases. Photometry of the near-infrared counterparts of the YSO-candidates was combined with their IRAS fluxes to yield broad-band spectral energy distributions (SED's). The broadness and steepness of the SED's indicated clear evidence of the evolutionary stage of the objects confirming their youth. Given all of the new information obtained, a firm conclusion emerged, namely that Bok globules are active sites of low-mass star formation.

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