Publications
of the
MPIfR
Optical & Infrared
Interferometry Group
T. Preibisch and H. Zinnecker
The history of low-mass star formation in the upper Scorpius OB
association
Astronomical Journal 117, 2381-2397 (1999)
Abstract.
We use a large sample of about 100 low-mass pre-main sequence (PMS) stars in
the Upper Scorpius OB association to explore the star formation history and
the IMF of this association. Upper Scorpius is an ideal target
for such a study, because the star formation process there is finished.
The PMS stars have recently been found in a
spatially unbiased wide field survey of X-ray selected stars in a 160
square-degree area, covering the Upper
Scorpius association nearly completely. Following the optical characterization
of these PMS stars, we present a
new HR diagram for this association.
We perform a detailed analysis of the HR diagram,
taking proper account of the uncertainties and the effects of
unresolved binaries, and derive ages and masses for the PMS stars. We find
that the low-mass PMS stars have a
mean age of about 5 Myr and show no evidence for a large age dispersion.
This agrees very well with the age of 5-6 Myr previously found for the
massive stars and shows that low-mass and high-mass stars are coeval and
co-spatial and thus have formed together.
We conclude that the star formation process in Upper Scorpius was probably
triggered by the shock wave of a
supernova explosion in the nearby Upper Centaurus-Lupus association.
After a short burst of very high star
formation activity, which lasted only for a few Myr, star formation in
Upper Scorpius was halted, probably by the
strong winds and the ionizing radiation of the numerous massive stars which
dispersed the molecular cloud.
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