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| Paper: |
Star-Formation at High Galactic Latitude |
| Volume: |
154, Cool Stars, Stellar Systems and the Sun: Tenth Cambridge Workshop |
| Page: |
1716 |
| Authors: |
Hearty, Thomas; Magnani, Loris; Caillault, Jean-Pierre; Neuhauser, Ralph; Schmitt, J. H. M. M.; Stauffer, John |
| Abstract: |
The star-formation capability of molecular clouds at high galactic latitude (|b| > 30 deg) is investigated. Possible pre-main sequence stars in and around translucent and dark high-latitude clouds have been identified via their X-ray emission by inspecting ROSAT All-Sky Survey and ROSAT pointed observations of the cores and surrounding regions of the clouds. Follow-up optical spectroscopy of the stellar X-ray sources with m_v <~ 15.5 mag was conducted with the 1.5-m Fred Lawrence Whipple Observatory telescope to identify standard signatures of pre-main sequence stars (i.e., Li 1 lambda6708 AA absorption and Hα emission). We found 16 stars near several of the molecular clouds which have lithium equivalent widths above our detection threshold. Three stars also have weak Hα emission. Relative ages for the stars with lithium are estimated by their position on a W(Li) vs. T_eff diagram. A calibration derived from data for several clusters with known ages indicates the stars are older than the translucent high-latitude clouds. We find it is unlikely that most of the X-ray active, lithium-rich stars we identified have formed in the clouds in question. Theoretical and observational arguments support this conclusion and render unlikely the possibility that low-extinction, low column density clouds, such as most of the high-latitude clouds can support star-formation. |
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