THE AGE, STELLAR CONTENT, AND STAR FORMATION TIMESCALE OF THE B59 DENSE CORE

Journal Article · Wed Oct 20 04:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/722/2/971· OSTI ID:21464649

Covey, K R; Lada, C J; Muench, A A; Forbrich, J; Ascenso, J ^[1]; Roman-Zuniga, C ^[2]

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1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
2. Centro Astronomico Hispano Aleman/CSIC-IAA, Granada 18006 (Spain)

We have investigated the stellar content of Barnard 59 (B59), the most active star-forming core in the Pipe Nebula. Using the SpeX spectrograph on the NASA Infrared Telescope Facility, we obtained moderate resolution, near-infrared (NIR) spectra for 20 candidate young stellar objects (YSOs) in B59 and a representative sample of NIR and mid-IR bright sources distributed throughout the Pipe. Measuring luminosity and temperature sensitive features in these spectra, we identified likely background giant stars and measured each star's spectral type, extinction, and NIR continuum excess. To measure B59's age, we place its candidate YSOs in the Hertzsprung-Russell diagram and compare their location to YSOs in several well-studied star-forming regions, as well as predictions of pre-main-sequence (PMS) evolutionary models. We find that B59 is composed of late-type (K4-M6) low-mass (0.9-0.1 M{sub sun}) YSOs whose median stellar age is comparable to, if not slightly older than, that of YSOs within the {rho} Oph, Taurus, and Chameleon star-forming regions. Deriving absolute age estimates from PMS models computed by D'Antona et al., and accounting only for statistical uncertainties, we measure B59's median stellar age to be 2.6 {+-} 0.8 Myr. Including potential systematic effects increases the error budget for B59's median (DM98) stellar age to 2.6{sup +4.1}{sub -2.6} Myr. We also find that the relative age orderings implied by PMS evolutionary tracks depend on the range of stellar masses sampled, as model isochrones possess significantly different mass dependences. The maximum likelihood median stellar age we measure for B59, and the region's observed gas properties, suggests that the B59 dense core has been stable against global collapse for roughly six dynamical timescales and is actively forming stars with a star formation efficiency per dynamical time of {approx}6%. While the {approx}150% uncertainties associated with our age measurement propagate directly into these derived star formation timescales, the maximum likelihood values nonetheless agree well with recent star formation simulations that incorporate various forms of support against collapse, such as subcritical magnetic fields, outflows, and radiative feedback from protostellar heating.

• OSTI ID: 21464649
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 722; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
DIAGRAMS
EVOLUTION
GIANT STARS
HERTZSPRUNG-RUSSELL DIAGRAM
INFORMATION
MAGNETIC FIELDS
MATHEMATICAL SOLUTIONS
MAXIMUM-LIKELIHOOD FIT
NEBULAE
NUMERICAL SOLUTION
SIMULATION
SPECTRA
STAR EVOLUTION
STARS
TELESCOPES