Physical conditions in the warped accretion disk of a massive star. 349 GHz ALMA observations of G023.01$-$00.41

Abstract

Young massive stars warm up the large amount of gas and dust which condenses in their vicinity, exciting a forest of lines from different molecular species. Their line brightness is a diagnostic tool of the gas physical conditions locally, which we use to set constraints on the environment where massive stars form. We made use of the Atacama Large Millimeter/submillimeter Array at frequencies near 349 GHz, with an angular resolution of $0.1^{\prime \prime }$, to observe the methyl cyanide (CH${}_3$CN) emission which arises from the accretion disk of a young massive star. We sample the disk midplane with twelve distinct beams, where we get an independent measure of the gas (and dust) physical conditions. The accretion disk extends above the midplane showing a double-armed spiral morphology projected onto the plane of the sky, which we sample with ten additional beams: along these apparent spiral features, gas undergoes velocity gradients of about $1km{\mathrm{s}}^{-1}$ per 2000 au. The gas temperature (T) rises symmetrically along each side of the disk, from about 98 K at 3000 au to 289 K at 250 au, following a power law with radius, R${}^{-0.43}$. The CH${}_3$CN column density (N) increases from $9.2\times 10^{15}\mathrm{c}{\mathrm{m}}^{-2}$ to $8.7\times 10^{17}\mathrm{c}{\mathrm{m}}^{-2}$ at the same radii, following a power law with radius, R${}^{-1.8}$. In the framework of a circular gaseous disk observed approximately edge-on, we infer an H${}_2$ volume density in excess of $4.8\times 10^9\mathrm{c}{\mathrm{m}}^{-3}$ at a distance of 250 au from the star. We study the disk stability against fragmentation following the methodology by Kratter et al. (2010), appropriate under rapid accretion, and we show that the disk is marginally prone to fragmentation along its whole extent.

17 pages, 10 figures, 3 tables, accepted by Astronomy & Astrophysics

References in corpus (14)

• The Critical Density and the Effective Excitation Density of Commonly Observed Molecular Dense Gas Tracers
• On the existence of accretion-driven bursts in massive star formation
• An Unstable Truth: How Massive Stars get their Mass
• Trigonometric Parallaxes of Massive Star Forming Regions: V. G23.01-0.41 and G23.44-0.18
• Forming spectroscopic massive proto-binaries by disk fragmentation
• A necklace of dense cores in the high-mass star forming region G35.20-0.74N: ALMA observations
• Substructures in the Keplerian disc around the O-type (proto)star G17.64+0.16
• Modeling disk fragmentation and multiplicity in massive star formation
• Subarcsecond Imaging of the NGC 6334 I(N) Protocluster: Two Dozen Compact Sources and a Massive Disk Candidate
• Spiral arms and instability within the AFGL 4176 mm1 disc
• Radiation-hydrodynamical simulations of massive star formation using Monte Carlo radiative transfer II. The formation of a 25 solar-mass star
• ALMA View of the Infalling Envelope around a Massive Protostar in S255IR SMA1
• Disk Kinematics and Stability in High-Mass Star Formation: Linking Simulations and Observations
• Momentum-driven outflow emission from an O-type YSO: Comparing the radio jet with the molecular outflow

Cited by in corpus (8)

• A massive Keplerian protostellar disk with flyby-induced spirals in the Central Molecular Zone
• Salt-bearing disk candidates around high-mass young stellar objects
• The burst mode of accretion in massive star formation with stellar inertia
• Vibrationally-excited Lines of HC${}_3$N Associated with the Molecular Disk around the G24.78+0.08 A1 Hyper-compact H${}_{\mathrm{II}}$ Region
• Gas infall via accretion disk feeding Cepheus A HW2
• Could kilomasers pinpoint supermassive stars?
• CH${}_3$OH as a User-Friendly Density Probe: Calibration and Beyond
• A kinematic study of the disc-outflow system around a high-mass protostar G59.783+0.065 probed by methanol and water masers