Publications
of the
MPIfR
Optical & Infrared
Interferometry Group
T. Preibisch, E. Guenther, and H.
Zinnecker
A large spectroscopic survey for young
low-mass members of the Upper Scorpius OB Association
Astronomical Journal 121, 1040-1049 (2001)
Abstract.
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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