Star Formation at High Galactic Latitude:
A Case for Extensions to the Survey

Star Formation in HLCs

Given that most high-latitude clouds are translucent and quiescent, it is somewhat surprising that several have been found to contain young stellar objects. Furthermore, several high-latitude young stellar objects have been found serendipitously, apparently isolated from any molecular material (Feigelson 1996). Since these discoveries, all-sky databases from missions such as IRAS and Einstein, have been searched for point sources having the infrared and X-ray spectral signatures of TTauri stars, yielding hundred of candidates (eg. Magnani et al. 1995; Caillault et al. 1995). However, the most convincing signature of stellar youth is emission from the interface of the stellar photosphere and circumstellar material. Most high-latitude surveys to date have been objective prism images of well-known CO clouds (eg. Kun 1992). When digitized and paired with continuum images, the new AAO/UKST Survey will have the advantages of increased area, resolution, and sensitivity.

Gravitational collapse of cores in dense clouds is known to form stars. By what mechanism could TTauri stars form in translucent HLCs? Possibilities include shock-induced formation, dispersal/ejection from other regions, and formation in situ followed by evaporation of the surrounding cloud. When compared with multi-wavelength measurements of cloud environment, the detection of TTauri stars at high-latitude will have important implications for our understanding of the limits of conditions and processes that lead to star formation. To date, none of the TTauri stars found at high latitude are in a translucent cloud environment, but a more systematic search is needed.

© Copyright Astronomical Society of Australia 1997