THE INITIAL MASS FUNCTION AND DISK FREQUENCY OF THE {rho} OPHIUCHI CLOUD: AN EXTINCTION-LIMITED SAMPLE

Journal Article · Sat Oct 15 00:00:00 EDT 2011 · Astronomical Journal (New York, N.Y. Online)

DOI:https://doi.org/10.1088/0004-6256/142/4/140· OSTI ID:21582816

Erickson, Kristen L; Wilking, Bruce A; Robinson, John G; Stephenson, Lauren N ^[1]

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1. 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), Vol. 142, Issue 4; Other Information: DOI: 10.1088/0004-6256/142/4/140; ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABSORPTION
BOLOMETERS
EMISSION
LITHIUM
LUMINOSITY
MAIN SEQUENCE STARS
MASS
PHOTOMETRY
PROPER MOTION
STAR EVOLUTION
X RADIATION
ALKALI METALS
ELECTROMAGNETIC RADIATION
ELEMENTS
EVOLUTION
IONIZING RADIATIONS
MEASURING INSTRUMENTS
METALS
MOTION
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
SORPTION
STARS