Star formation in the Orion nebula cluster
Abstract (from CDS):
We study the record of star formation activity within the dense cluster
associated with the Orion Nebula. The bolometric luminosity function
of 900 visible members is well matched by a simplified theoretical
model for cluster formation. This model assumes that stars are
produced at a constant rate and distributed according to the
field-star initial mass function. Our best-fit age for the system,
within this framework, is 2x106 yr. To undertake a more
detailed analysis, we present a new set of theoretical pre-main-sequence
tracks. These cover all masses from 0.1 to 6.0 M☉, and
start from a realistic stellar birthline. The tracks end along a
zero-age main-sequence that is in excellent agreement with the
empirical one. As a further aid to cluster studies, we offer an
heuristic procedure for the correction of pre-main-sequence luminosities
and ages to account for the effects of unresolved binary companions.
The Orion Nebula stars fall neatly between our birthline and
zero-age main-sequence in the H-R diagram. All those more massive
than about 8 M☉ lie close to the main sequence, as also
predicted by theory. After accounting for the finite sensitivity of
the underlying observations, we confirm that the population between
0.4 and 6.0 M☉ roughly follows a standard initial mass
function. We see no evidence for a turnover at lower masses. We next
use our tracks to compile stellar ages, also between 0.4 and 6.0 M☉. Our age histogram reveals that star formation began at a low level some 107
yr ago and has gradually accelerated to the present epoch. The
period of most active formation is indeed confined to a fewx106
yr, and has recently ended with gas dispersal from the Trapezium. We
argue that the acceleration in stellar births, which extends over a
wide range in mass, reflects the gravitational contraction of the
parent cloud spawning this cluster.
http://simbad.harvard.edu/simbad/sim-ref?querymethod=bib&simbo=on&submit=submit+bibcode&bibcode=1999ApJ...525..772P
http://simbad.harvard.edu/simbad/sim-ref?querymethod=bib&simbo=on&submit=submit+bibcode&bibcode=1999ApJ...525..772P
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