The Angular Momentum Content and Evolution of Class I and Flat-Spectrum Protostars

Abstract

We report on the angular momentum content of heavily embedded protostars based on our analysis of the projected rotation velocities (v sin i s) of 38 Class I/flat spectrum young stellar objects presented by Doppmann et al (2005). After correcting for projection effects, we find that infrared-selected Class I/flat spectrum objects rotate significantly more quickly (median equatorial rotation velocity ~ 38 km/sec) than Classical T Tauri stars (CTTSs; median equatorial rotation velocity ~ 18 km/sec) in the Rho Ophiuchi and Taurus-Aurigae regions. The detected difference in rotation speeds between Class I/flat spectrum sources and CTTSs proves difficult to explain without some mechanism which transfers angular momentum out of the protostar between the two phases. Assuming Class I/flat spectrum sources possess physical characteristics (M_*,R_*,B_*) typical of pre-main sequence stars, fully disk locked Class I objects should have co-rotation radii within their protostellar disks that match well (within 30%) with the predicted magnetic coupling radii of Shu et al (1994). The factor of two difference in rotation rates between Class I/flat spectrum and CTTS sources, when interpreted in the context of disk locking models, also imply a factor of 5 or greater difference in mass accretion rates between the two phases.

13 pages, 6 figures. Accepted for publication in the Astronomical Journal (tentatively for June 2005 edition)

References in corpus (22)

• The VizieR database of Astronomical Catalogues
• The NextGen Model Atmosphere grid for $3000\le \Teff \le 10000\K$
• Very Low Mass Stars and Brown Dwarfs in Taurus-Auriga
• Rotation and Activity in Mid-M to L Dwarfs
• On the Evolutionary Status of Class I Stars and Herbig-Haro Energy Sources in Taurus-Auriga
• 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
• Evidence for a T Tauri Phase in Young Brown Dwarfs
• The Mass Dependence of Stellar Rotation in the Orion Nebula Cluster
• Rotation in the Orion Nebula Cluster
• The young stellar population in the Serpens Cloud Core: An ISOCAM survey
• New Tests of Magnetospheric Accretion in T Tauri Stars
• Rotational Velocities and Radii of Pre-Main-Sequence Stars in the Orion Nebula Cluster
• A Near-Infrared Multiplicity Survey of Class I/Flat-Spectrum Systems in Six Nearby Molecular Clouds
• The Discovery of a Companion to the Very Cool Dwarf Gl~569~B with the Keck Adaptive Optics Facility
• Rotation periods of late-type stars in the young open cluster IC 2602
• Spectroscopic Detection of a Stellar-like Photosphere in an Accreting Protostar
• A 10-micron Search for Inner-Truncated Disks Among Pre-Main-Sequence Stars With Photometric Rotation Periods
• Stellar Properties of Pre-Main Sequence Stars from High Resolution Near-IR Spectra
• Does Disk Locking Solve the Stellar Angular Momentum Problem?
• High Resolution Near-Infrared Spectra of Protostars
• Can FU Orionis Outbursts Regulate the Rotation Rates of T Tauri Stars?

Cited by in corpus (23)

• The Formation and Early Evolution of Low-mass Stars and Brown Dwarfs
• The Physical Natures of Class I and Flat-Spectrum Protostellar Photospheres: A Near-Infrared Spectroscopic Study
• The Turbulent Origin of Spin-Orbit Misalignment in Planetary Systems
• OVRO N2H+ Observations of Class 0 Protostars: Constraints on the Formation of Binary Stars
• Spin Evolution of Accreting Young Stars. I. Effect of Magnetic Star-Disk Coupling
• Testing the Disk Regulation Paradigm with Spitzer Observations. I. Rotation Periods of Pre-main Sequence Stars in the IC 348 Cluster
• Observational studies of stellar rotation
• Pulsed Accretion in a Variable Protostar
• First Magnetic Field Detection on a Class I Protostar
• Measuring the magnetic field of young stars using iSHELL observations: BP Tau and V347 Aur
• The influence of the environment on the spin evolution of low-mass stars. I. External photoevaporation of circumstellar disks
• Mid-Infrared Observations of Class I/Flat-Spectrum Systems in Six Nearby Molecular Clouds
• Stellar Rotation: A Clue to the Origin of High Mass Stars?
• Stellar and Circumstellar Properties of Class I Protostars
• Spectral Energy Distributions of Young Stars in IC 348: The Role of Disks in Angular Momentum Evolution of Young, Low-Mass Stars
• Protostellar spin-down: a planetary lift?
• The Near Stellar Environment of Class 0 Protostars: A First Look with Near-Infrared Spectroscopy
• Measurement of the angular momenta of pre-main-sequence stars: early evolution of slow and fast rotators and empirical constraints on spin-down torque mechanisms
• Astrophysics in 2005
• Vsini-s for late-type stars from spectral synthesis in K-band region
• The Nature of Class I Sources: Periodic Variables in Orion
• Evidence of Accretion Burst: The Viscously Heated Inner Disk of the Embedded Protostar IRAS 16316-1540
• Searching for proto-brown dwarfs: Extending near IR spectroscopy of protostars below the hydrogen burning limit