A large spectroscopic survey for young low-mass members of the Upper Scorpius OB Association

Thomas Preibisch, Eike Guenther, & Hans Zinnecker

Astronomical Journal, 121, 1040 (2001)


We present the results of a large intermediate-resolution spectroscopic survey for pre-main sequence (PMS) stars in the Upper Scorpius OB association, the most nearby region of recent massive star formation. Utilizing the multi-object spectrograph 2dF at the Anglo-Australian-Telescope, we obtained spectra of 576 stars with magnitudes R = [12.5 - 16.5] in a 6 square-degree area in Upper Scorpius. Among these objects we were able to identify 98 new PMS stars, nearly all of them M-type stars, by their strong lithium absorption lines. We place the new PMS stars into the HR diagram and find that their ages agree well with the mean age of 5 Myr determined in our earlier investigation (Preibisch & Zinnecker 1999) based on a smaller sample of stars. The number of low-mass (M_star ~ [0.1 - 0.5] M_sun) members is at least as high as expected from the know number of high-mass (M_star <= 3 M_sun) association members and recent determinations of the field star IMF. Thus, there is no deficit of low-mass stars in Upper Scorpius.

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You might be also interested in the previous paper about the young stars in Upper Scorpius, which was the basis of this work.

Some nice images of the Upper Scorpius association can be found here .

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