| dc.description.abstract | The Lupus molecular cloud complex is a nearby star-forming region in the southern
sky. The Lupus 1-4 molecular clouds are associated with obvious ongoing
star-forming activities, among which Lupus 3 clouds has the highest molecular
column density and hosts the largest number of T Tauri stars, signifying recent, active
star formation. The Lupus 5-9 clouds show no star formation activities.
We used archival UK Schmidt Telescope H-alpha Sky Survey and 2MASS
point-source catalog to identify in Lupus 3 (known to have atctive star formation) and
Lupus 5 (known to have no star formation) candidate low-mass pre-main sequence
stars, namely the classical T Tauri stars (CTTSs), which are characterized by H-alpha
emission and near-infrared excess. Some of the bright candidates were observed by
optical spectroscopy. In Lupus 3, almost all known CTTSs were found in our study.
In addition, we identified 4 candidates H-alpha stars not previously catalogued. Two
of them show a very strong H-alpha line in emission and prominent near-infrared
excess, yet are located away (0.4 deg) from the densest parts of the molecular clouds
so have been overlooked by earlier surveys. This suggests that the young stellar
sample, thus the star formation history, in the region may be largely incomplete. The
other two H-alpha stars were spectroscopically confirmed to be active chromospheric
M dwarfs (dMe stars). Extending our analysis to Lupus 5, we found only one
candidate whose spectrum indeed shows the H-alpha line, but without notable
near-infrared excess. This H-alpha star therefore is likely a dMe, rather than a young
star. Our study thereby confirms that the Lupus 5 cloud is quiescent in star
formation.
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