The Physical Natures of Class I and Flat-Spectrum Protostellar Photospheres: A Near-Infrared Spectroscopic Study

Abstract

We present high resolution (R = 18,000), high signal-to-noise, 2 micron spectra of 52 infrared-selected Class I and flat-spectrum young stellar objects in the Taurus-Auriga, $\rho$ Ophiuchi, Serpens, Perseus, and Corona Australis dark clouds. We detect key absorption lines in 41 objects and fit synthetic spectra generated from pre-main sequence models to deduce the effective temperatures, surface gravities, near-infrared veilings, rotation velocities, and radial velocities of each of these 41 sources. We find these objects to span ranges in effective temperature, surface gravity, and stellar luminosity which appear similar to those of late spectral-type Class II sources and classical T-Tauri stars. We determine that the mean 2 micron veiling of Class I and flat-spectrum objects is significantly higher than that of Class II objects in the same region where both types of objects are extensively observed ($\rho$ Oph). We find a significant fraction of our protostellar sample also exhibits emission lines. Twenty-three objects show H${}_2$ emission, usually indicative of the presence of energetic outflows. Thirty-four sources show HI Br $\gamma$ emission and a number of these exhibit profile asymmetries consistent with in-fall. Eight sources show significant $\Delta v=2$ CO emission suggestive of emission from a circumstellar disk. Overall, these observations indicate that Class I and flat-spectrum objects are self-embedded protostars undergoing significant mass accretion, although the objects appear to span a broad range of mass accretion activity.

arXiv commentLaTeX, 35 pages + 23 figures. Accepted for publication in AJ

References in corpus (20)

• The VizieR database of Astronomical Catalogues
• A Hipparcos census of the nearby OB associations
• The NextGen Model Atmosphere grid for $3000\le \Teff \le 10000\K$
• A Method of Correcting Near-Infrared Spectra for Telluric Absorption
• Radial Velocities for 889 Late-type Stars
• 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
• The Palomar/MSU Nearby Star Spectroscopic Survey III: Chromospheric Activity, M-dwarf Ages and the Local Star Formation History
• Low-Mass Star Formation and the Initial Mass Function in the Rho Ophiuchi Cloud Core
• Kinematic Diagnostics of Disks Around Young Stars: CO Overtone Emission from WL16 and 1548C27
• Optical Spectroscopy of Embedded Young Stars in the Taurus-Auriga Molecular Cloud
• Probing the embedded YSOs of the R CrA region through VLT-ISAAC spectroscopy
• The young stellar population in the Serpens Cloud Core: An ISOCAM survey
• The Ages of Pre-main-sequence Stars
• NGC 2362: a Template for Early Stellar Evolution
• Spectroscopic Detection of a Stellar-like Photosphere in an Accreting Protostar
• Stellar Properties of Pre-Main Sequence Stars from High Resolution Near-IR Spectra
• The Angular Momentum Content and Evolution of Class I and Flat-Spectrum Protostars
• High Resolution Near-Infrared Spectra of Protostars
• A Spectroscopic Technique for Measuring Stellar Properties of Pre-Main Sequence Stars

Cited by in corpus (91)

• Theory of Star Formation
• The Spitzer c2d Legacy Results: Star Formation Rates and Efficiencies; Evolution and Lifetimes
• The XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST)
• A Submillimeter View of Circumstellar Dust Disks in $\rho$ Ophiuchus
• VLBA determination of the distance to nearby star-forming regions IV. A preliminary distance to the proto-Herbig AeBe star EC95 in the Serpens Core
• A Near-IR Spectroscopic Survey of FU Orionis Objects
• A Near-Infrared Spectroscopic Survey of Class I Protostars
• Protoplanetary disk rings and gaps across ages and luminosities
• Hot Organic Molecules Toward a Young Low-Mass Star: A Look at Inner Disk Chemistry
• A Combined Spitzer and Chandra Survey of Young Stellar Objects in the Serpens Cloud Core
• The Ophiuchus DIsc Survey Employing ALMA (ODISEA)-III: the evolution of substructures in massive discs at 3-5 au resolution
• Measuring Protoplanetary Disk Accretion with H I Pf-beta
• Multiple Gaps in the Disk of the Class I Protostar GY 91
• A Survey for New Members of the Taurus Star-Forming Region with the Sloan Digital Sky Survey
• The Age, Stellar Content and Star Formation Timescale of the B59 Dense Core
• Accretion and ejection properties of embedded protostars: the case of HH26, HH34 and HH46 IRS
• Near Infrared Spectroscopic Monitoring of EXor variables: First Results
• A census of molecular hydrogen outflows and their sources along the Orion A molecular ridge: characteristics and overall distribution
• Dust Polarization Toward Embedded Protostars in Ophiuchus with ALMA. III. Survey Overview
• A continuum of accretion burst behavior in young stars observed by K2
• Variable accretion and outflow in young brown dwarfs
• POISSON project - II - A multi-wavelength spectroscopic and photometric survey of young protostars in L 1641
• The onset of X-ray emission in young stellar objects: a Chandra observation of the Serpens star-forming region
• Highly Variable Extinction and Accretion in the Jet-driving Class I Type Young Star PTF 10nvg (V2492 Cyg, IRAS 20496+4354)
• Disk Masses for Embedded Class I Protostars in the Taurus Molecular Cloud
• Coronae in the Coronet: A very deep X-ray look into a stellar nursery
• Disks and Outflows in CO Rovibrational Emission from Embedded, Low-Mass Young Stellar Objects
• A Census of the Taurus Star-forming Region and Neighboring Associations with Gaia
• Near-Infrared High-Resolution Imaging Polarimetry of FU Ori-Type Objects: Towards A Unified Scheme for Low-Mass Protostellar Evolution
• WL 17: A Young Embedded Transition Disk
• High Resolution Near-Infrared Spectroscopy of FUors and FUor-like stars
• KMOS study of the mass accretion rate from Class I to Class II in NGC 1333
• POISSON project - III - Investigating the evolution of the mass accretion rate
• APOGEE Net: Improving the derived spectral parameters for young stars through deep learning
• The Mass Accretion Rate and Stellar Properties in Class I Protostars
• The JCMT Transient Survey: Detection of sub-mm variability in a Class I protostar EC 53 in Serpens Main
• Disk Masses at the end of the main accretion phase: CARMA Observations and Multi-Wavelength Modeling of Class I Protostars
• The Radial Velocity Distribution of Class I and Flat-Spectrum Protostars
• Star-disc (mis-)alignment in Rho Oph and Upper Sco: insights from spatially resolved disc systems with K2 rotation periods
• First Magnetic Field Detection on a Class I Protostar
• JWST Observations of Young protoStars (JOYS): Linked accretion and ejection in a Class I protobinary system
• The Effects of Starspots on Spectroscopic Mass Estimates of Low-mass Young Stars
• A Hot Gap Around Jupiter's Orbit in the Solar Nebula
• Experimental Ti I oscillator strengths and their application to cool star analysis
• Unveiling the nature and interaction of the intermediate/high-mass YSOs in IRAS 20343+4129
• Discovering Protostars and their Host Clusters via WISE
• Investigating the Nature of Variable Class I and Flat Spectrum Protostars Using 2-4$\mu$m Spectroscopy
• Short and long term near-infrared spectroscopic variability of eruptive protostars from VVV
• Accretion in rho-Ophiuchi brown dwarfs: infrared hydrogen line ratios
• Stellar and Circumstellar Properties of the Pre-Main Sequence Binary GV Tau from Infrared Spectroscopy
• Classifying the embedded young stellar population in Perseus and Taurus & the LOMASS database
• Multi-epoch Sub-arcsecond [Fe II] Spectroimaging of the DG Tau Outflows with NIFS. I. First data epoch
• Measuring the magnetic field of young stars using iSHELL observations: BP Tau and V347 Aur
• The Mean Magnetic Field Strength of CI Tau
• The Anatomy of an Unusual Edge-on Protoplanetary Disk. II. Gas temperature and a warm outer region
• Mid-Infrared Observations of Class I/Flat-Spectrum Systems in Six Nearby Molecular Clouds
• X-ray Emission from the FU Orionis Star V1735 Cygni
• The Identification of 93 Day Periodic Photometric Variability for YSO YLW 16A
• Stellar and Circumstellar Properties of Class I Protostars
• Discovery of a mid-infrared protostellar outburst of exceptional amplitude
• Near-IR Molecular Hydrogen Emission of Protostars: Probing Circumstellar Environments
• The feedback of atomic jets from embedded protostars in NGC 1333
• Constraining the Disk Masses of the Class I Binary Protostar GV Tau
• FLAMINGOS Near Infra-Red Survey of The Serpens Cloud Main Core
• Detection of Photospheric Features in the Near-Infrared Spectrum of a Class 0 Protostar
• The Near Stellar Environment of Class 0 Protostars: A First Look with Near-Infrared Spectroscopy
• Submillimeter Observations of the Young Low-Mass Object IRAS 04158+2805
• Is T Tauri North a 'Classical' T Tauri star?
• The relation between the Mass Accretion Rate and the Disk Mass in Class I Protostars
• An ALMA Study of the FU-Ori Type Object V900 Mon: Implications for the Progenitor
• IGRINS spectroscopy of Class I sources: IRAS 03445+3242 and IRAS 04239+2436
• Photo-reverberation Mapping of a Protoplanetary Accretion Disk around a T Tauri Star
• IRAS04325+2402C: A very low mass object with an edge-on disk
• Time-Variable Accretion in the TW Hya Star/Disk System
• The low-mass YSO CB230-A: investigating the protostar and its jet with NIR spectroscopy and Spitzer observations
• Finding proto-spectroscopic binaries: Precise multi-epoch radial velocities of 7 protostars in rho-Ophiuchus
• V1647 ORIONIS: Keck/Nirspec 2 MICRON Echelle Observations
• Massive pre-main-sequence stars in M17: $1^{\mathrm{st}}$ and $2^{\mathrm{nd}}$ overtone CO bandhead emission and the thermal infrared
• Astrophysics in 2005
• Inner warm disk of ESO H$\alpha$ 279A revealed by NA I and CO overtone emission lines
• Vsini-s for late-type stars from spectral synthesis in K-band region
• Variability of the Great Disk Shadow in Serpens
• On the diversification and dissipation of protoplanetary disks
• Large Amplitude Photometric Variability of the Candidate Protoplanet TMR-1C
• The Nature of Class I Sources: Periodic Variables in Orion
• A near-infrared variability campaign of TMR-1: New light on the nature of the candidate protoplanet TMR-1C
• Magnetic field measurements in a sample of Class I and flat-spectrum protostars observed with SPIRou
• Evidence of Accretion Burst: The Viscously Heated Inner Disk of the Embedded Protostar IRAS 16316-1540
• The role of radiative torques in the molecular cloud core L43
• Searching for proto-brown dwarfs: Extending near IR spectroscopy of protostars below the hydrogen burning limit
• The Variation of Circumstellar Parameters through Early Stellar Evolution