Optical Spectroscopy of the Surface Population of the rho Ophiuchi Molecular Cloud: The First Wave of Star Formation
Astrophysics, abstract
astro-ph/0506251
From: Michael R. Meyer [view email]
Date: Fri, 10 Jun 2005 22:01:57 GMT (414kb)
Optical Spectroscopy of the Surface Population of the rho Ophiuchi
Molecular Cloud: The First Wave of Star Formation
Authors:
Bruce A. Wilking (Department of Physics and Astronomy, University of Missouri-St. Louis),
Michael R. Meyer (Steward Observatory, The University of Arizona),
John G. Robinson (Department of Physics and Astronomy, University of Missouri-St. Louis),
Thomas P. Greene (NASA/Ames Research Center)
Comments: 35 pages of postscript which includes seven figures (some of which
are multi-panel) and four postscript tables. Astronomical Journal (in press)
We present the results of optical spectroscopy of 139 stars obtained with the
Hydra multi-object spectrograph. The objects extend over a 1.3 square degree
area surrounding the main cloud of the rho Oph complex. The objects were
selected from narrowband images to have H alpha in emission. Using the presence
of strong H alpha emission, lithium absorption, location in the
Hertzsprung-Russell diagram, or previously reported x-ray emission, we were
able to identify 88 objects as young stars associated with the cloud. Strong H
alpha emission was confirmed in 39 objects with line widths consistent with
their origin in magnetospheric accretion columns. Two of the strongest
emission-line objects are young, x-ray emitting brown dwarf candidates with M8
spectral types. Comparisons of the bolometric luminosities and effective
temperatures with theoretical models suggest a medianage for this population of
2.1 Myr which is signifcantly older than the ages derived for objects in the
cloud core. It appears that these stars formed contemporaneously with low mass
stars in the Upper Scorpius subgroup, likely triggered by massive stars in the
Upper-Centaurus subgroup.
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