THE INITIAL MASS FUNCTION AND DISK FREQUENCY OF THE {rho} OPHIUCHI CLOUD: AN EXTINCTION-LIMITED SAMPLE
- Department of Physics and Astronomy, University of Missouri-St. Louis, 1 University Boulevard, St. Louis, MO 63121 (United States)
We have completed an optical spectroscopic survey of an unbiased, extinction-limited sample of candidate young stars covering 1.3 deg{sup 2} of the {rho} Ophiuchi star-forming region. While infrared, X-ray, and optical surveys of the cloud have identified many young stellar objects (YSOs), these surveys are biased toward particular stages of stellar evolution and are not optimal for studies of the disk frequency and initial mass function. We have obtained over 300 optical spectra to help identify 135 association members based on the presence of H{alpha} in emission, lithium absorption, X-ray emission, a mid-infrared excess, a common proper motion, reflection nebulosity, and/or extinction considerations. Spectral types along with R- and I-band photometry were used to derive effective temperatures and bolometric luminosities for association members to compare with theoretical tracks and isochrones for pre-main-sequence stars. An average age of 3.1 Myr is derived for this population which is intermediate between that of objects embedded in the cloud core of {rho} Ophiuchi and low-mass stars in the Upper Scorpius subgroup. Consistent with this age we find a circumstellar disk frequency of 27% {+-} 5%. We also constructed an initial mass function for an extinction-limited sample of 123 YSOs (A{sub v} {<=} 8 mag), which is consistent with the field star initial mass function for YSOs with masses >0.2 M{sub sun}. There may be a deficit of brown dwarfs but this result relies on completeness corrections and requires confirmation.
- OSTI ID:
- 21582816
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Journal Name: Astronomical Journal (New York, N.Y. Online) Journal Issue: 4 Vol. 142; ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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ABSORPTION
ALKALI METALS
BOLOMETERS
ELECTROMAGNETIC RADIATION
ELEMENTS
EMISSION
EVOLUTION
IONIZING RADIATIONS
LITHIUM
LUMINOSITY
MAIN SEQUENCE STARS
MASS
MEASURING INSTRUMENTS
METALS
MOTION
OPTICAL PROPERTIES
PHOTOMETRY
PHYSICAL PROPERTIES
PROPER MOTION
RADIATIONS
SORPTION
STAR EVOLUTION
STARS
X RADIATION