Optical Spectroscopy of the Surface Population of the rho Ophiuchi Molecular Cloud: The First Wave of Star Formation

Abstract

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.

35 pages of postscript which includes seven figures (some of which are multi-panel) and four postscript tables. Astronomical Journal (in press)

References in corpus (14)

• A Hipparcos census of the nearby OB associations
• Astrometry and Photometry for Cool Dwarfs and Brown Dwarfs
• The Formation of Brown Dwarfs as Ejected Stellar Embryos
• Characterization of M,L and T dwarfs in the Sloan Digital Sky Survey
• The Formation Mechanism of Brown Dwarfs
• The Physics of Star Formation
• Young Low-Mass Stars and Brown Dwarfs in IC 348
• An Assessment of Dynamical Mass Constraints on Pre-Main Sequence Evolutionary Tracks
• ISOCAM observations of the rho Ophiuchi cloud: Luminosity and mass functions of the pre-main sequence embedded cluster
• Low-Mass Star Formation and the Initial Mass Function in the Rho Ophiuchi Cloud Core
• Spectroscopy of Brown Dwarf Candidates in the rho Ophiuchi Molecular Core
• Exploring Brown Dwarf Disks in rho Oph
• Simultaneous Chandra and VLA Observations of Young Stars and Protostars in rho Ophiuchus Cloud Core A
• The X-ray emission from Young Stellar Objects in the rho Ophiuchi cloud core as seen by XMM-Newton

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