High-Resolution M-band Spectroscopy of CO towards the Massive Young Stellar Binary W3 IRS5

Abstract

We present in this paper the results of high spectral resolution ($R$=88,100) spectroscopy at 4.7 $\mu$m with iSHELL/IRTF of hot molecular gas close to the massive binary protostar W3 IRS5. The binary was spatially resolved and the spectra of the two sources (MIR1 and MIR2) were obtained simultaneously for the first time. Hundreds of ${}^{12}$CO $\nu$=0-1, $\nu$=1-2 lines, and $\nu$=0-1 transitions of the isotopes of ${}^{12}$CO were detected in absorption, and are blue-shifted compared to the cloud velocity $v_{LSR}=-$38 km/s. We decompose and identify kinematic components from the velocity profiles, and apply rotation diagram and curve of growth analyses to determine their physical properties. Temperatures and column densities of the identified components range from 30$-$700 K and 10${}^{21}-$10${}^{22}$ cm${}^{-2}$, respectively. Our curve of growth analyses consider two scenarios. One assumes a foreground slab with a partial covering factor, which well reproduces the absorption of most of the components. The other assumes a circumstellar disk with an outward decreasing temperature in the vertical direction, and reproduces the absorption of all the hot components. We attribute the physical origins of the identified components to the foreground envelope ($<$100 K), post-J-shock regions (200$-$300 K), and clumpy structures on the circumstellar disks ($\sim$600 K). We propose that the components with a J-shock origin are akin to water maser spots in the same region, and are complementing the physical information of water masers along the direction of their movements.

arXiv commentAccepted for publication in ApJ. 26 pages, 12 figures, and 9 tables. Comments are more than welcome!

References in corpus (46)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Astropy: A Community Python Package for Astronomy
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• Theory of Star Formation
• Toward Understanding Massive Star Formation
• A Method of Correcting Near-Infrared Spectra for Telluric Absorption
• The Formation of Massive Stars from Turbulent Cores
• The Wavelength Dependence of Interstellar Extinction from 1.25 to 8.0 microns Using GLIMPSE Data
• On the Formation of Massive Stars
• The Formation of Massive Star Systems by Accretion
• Massive star formation: Nurture, not nature
• Star formation through gravitational collapse and competitive accretion
• Planetary Spectrum Generator: an accurate online radiative transfer suite for atmospheres, comets, small bodies and exoplanets
• Structure and Evolution of the Envelopes of Deeply Embedded Massive Young Stars
• Ultraviolet Survey of CO and H_2 in Diffuse Molecular Clouds: The Reflection of Two Photochemistry Regimes in Abundance Relationships
• A 3-5 micron VLT spectroscopic survey of embedded young low mass stars I: Structure of the CO ice
• The Birth of High Mass Stars: Accretion and/or Mergers?
• Accretion disks in luminous young stellar objects
• Sulphur chemistry in the envelopes of massive young stars
• How Protostellar Outflows Help Massive Stars Form
• Formation of simple organic molecules in inner T Tauri disks
• Galactic interstellar 18O/17O ratios - a radial gradient?
• The gas-phase chemistry of carbon chains in dark cloud chemical models
• Interstellar H${}_2$O Masers from J Shocks
• Substructures in the Keplerian disc around the O-type (proto)star G17.64+0.16
• Mid-infrared size survey of Young Stellar Objects: Description of Keck segment-tilting experiment and basic results
• The Role of Outflows, Radiation Pressure, and Magnetic Fields in Massive Star Formation
• Deexcitation nuclear gamma-ray line emission from low-energy cosmic rays in the inner Galaxy
• Subarcsecond mid-infrared and radio observations of the W3 IRS5 protocluster
• Millimeter interferometry of W3 IRS5: A Trapezium in the making
• Hubble Space Telescope NICMOS Imaging of W3 IRS 5: A Trapezium in the Making?
• Exploring organic chemistry in planet-forming zones
• A Galactic survey of radio jets from massive protostars
• Mid-infrared interferometry towards the massive young stellar object CRL 2136: inside the dust rim
• Gaia-DR2 distance to the W3 Complex in the Perseus Arm
• Dense molecular cocoons in the massive protocluster W3 IRS5: a test case for models of massive star formation
• Different Evolutionary Stages in the Massive Star Forming Region W3 Main Complex
• HyGAL: Characterizing the Galactic ISM with observations of hydrides and other small molecules -- I. Survey description and a first look toward W3(OH), W3 IRS5 and NGC 7538 IRS1
• High-Resolution Continuum Imaging at 1.3 and 0.7 cm of the W3 IRS 5 Region
• Interpretation of Infrared Vibration-Rotation Spectra of Interstellar and Circumstellar Molecules
• Disk fragmentation in high-mass star formation. High-resolution observations towards AFGL 2591-VLA 3
• Unveiling the traits of massive young stellar objects through a multi-scale survey
• Multi-wavelength modelling of the circumstellar environment of the massive proto-star AFGL 2591 VLA 3
• K-band High-Resolution Spectroscopy of Embedded Massive Protostars
• Tying the geometrical traits of massive young stellar objects and their discs to a potential evolutionary sequence using infrared observations

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• High-resolution SOFIA/EXES Spectroscopy of Water Absorption Lines in the Massive Young Binary W3 IRS 5