Zooming into the water snowline: high resolution water observations of the HL Tau disk

Abstract

Water is one of the central molecules for the formation and habitability of planets. In particular, the region where water freezes-out, the water snowline, could be a favorable location to form planets in protoplanetary disks. We use high resolution ALMA observations to spatially resolve H${}_2$O, H${}^{13}$CO${}^{+}$ and SO emission in the HL Tau disk. A rotational diagram analysis is used to characterize the water reservoir seen with ALMA and compare this to the reservoir visible at mid- and far-IR wavelengths. We find that the H${}_2$O 183 GHz line has a compact central component and a diffuse component that is seen out to ~75 au. A radially resolved rotational diagram shows that the excitation temperature of the water is ~350 K independent of radius. The steep drop in the water brightness temperature outside the central beam of the observations where the emission is optically thick is consistent with the water snowline being located inside the central beam ($\lesssim 6$ au) at the height probed by the observations. Comparing the ALMA lines to those seen at shorter wavelengths shows that only 0.02%-2% of the water reservoir is visible at mid- and far-IR wavelengths, respectively, due to optically thick dust hiding the emission whereas 35-70% is visible with ALMA. An anti-correlation between the H${}_2$O and H${}^{13}$CO${}^{+}$ emission is found but this is likely caused by optically thick dust hiding the H${}^{13}$CO${}^{+}$ emission in the disk center. Finally, we see SO emission tracing the disk and for the first time in SO a molecular outflow and the infalling streamer out to ~2". The velocity structure hints at a possible connection between the SO and the H${}_2$O emission. Spatially resolved observations of H${}_2$O lines at (sub-)mm wavelengths provide valuable constraints on the location of the water snowline, while probing the bulk of the gas-phase reservoirs.

arXiv commentAccepted for publication in A&A

References in corpus (51)

• An atomic and molecular database for analysis of submillimetre line observations
• First Results from High Angular Resolution ALMA Observations Toward the HL Tau Region
• The Disk Substructures at High Angular Resolution Project (DSHARP): I. Motivation, Sample, Calibration, and Overview
• CASA, the Common Astronomy Software Applications for Radio Astronomy
• The effects of snowlines on C/O in planetary atmospheres
• Interpreting Spectral Energy Distributions from Young Stellar Objects. II. Fitting observed SEDs using a large grid of pre-computed models
• A high accuracy computed water line list
• Dust and Gas in the disc of HL Tauri: Surface density, dust settling, and dust-to-gas ratio
• Planetesimal formation starts at the snow line
• The warm gas atmosphere of the HD 100546 disk seen by Herschel (Evidence of a gas-rich, carbon-poor atmosphere?)
• Planetesimal formation near the snowline: in or out?
• Astrochemistry and compositions of planetary systems
• Survival of molecular gas in cavities of transition disks (I. CO)
• The Post-Shock Chemical Lifetimes of Outflow Tracers and a Possible New Mechanism to Produce Water Ice Mantles
• The Radial Distribution of Dust Particles in the HL Tau Disk from ALMA and VLA Observations
• Water in star-forming regions (WISH): Physics and chemistry from clouds to disks as probed by Herschel spectroscopy
• Determining protoplanetary disk gas masses from CO isotopologues line observations
• The Gould's Belt Distances Survey (GOBELINS). IV. Distance, Depth and Kinematics of the Taurus Star-Forming Region
• Spitzer IRS Spectra and Envelope Models of Class I Protostars in Taurus
• ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT) VI: Accretion shocks in the disk of DG Tau and HL Tau
• The Distribution and Excitation of CH${}_3$CN in a Solar Nebula Analog
• Methanol and its relation to the water snowline in the disk around the young outbursting star V883 Ori
• Spectrally resolved pure rotational lines of water in protoplanetary disks
• Volatile snowlines in embedded disks around low-mass protostars
• The Physics of Water Masers observable with ALMA and SOFIA: Model Predictions for Evolved Stars
• HL Tau disk in HCO+ (3-2) and (1-0) with ALMA: gas density, temperature, gap, and one-arm spiral
• Chemical Modelling of Young Stellar Objects, I. Method and Benchmarks
• Empirical Temperature Measurement in Protoplanetary Disks
• Detection of warm water vapour in Taurus protoplanetary discs by Herschel
• MINDS. Abundant water and varying C/O across the disk of Sz 98 as seen by JWST/MIRI
• Spatially Extended Brackett Gamma Emission in the Environments of Young Stars
• Chemically tracing the water snowline in protoplanetary disks with HCO${}^{+}$
• 13C17O suggests gravitational instability in the HL Tau disc
• Gas temperature structure across transition disk cavities
• ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT) V: Sample, overview, and demography of disk molecular emission
• The properties of the inner disk around HL Tau: Multi-wavelength modeling of the dust emission
• A high resolution mid-infrared survey of water emission from protoplanetary disks
• Bayesian Analysis of Molecular Emission and Dust Continuum of Protoplanetary Disks
• Into the thick of it: ALMA 0.45 mm observations of HL Tau at 2 au resolution
• SMA Submillimeter Observations of HL Tau: Revealing a compact molecular outflow
• Resolved ALMA observations of water in the inner astronomical units of the HL Tau disk
• A major asymmetric ice trap in a planet-forming disk IV. Nitric oxide gas and a lack of CN tracing sublimating ices and a C/O ratio $<1$
• Solving for the 2D Water Snowline with Hydrodynamic Simulations. Emergence of gas outflow, water cycle and temperature plateau
• H${}_2$O distribution in the disc of HD 100546 and HD 163296: the role of dust dynamics and planet--disc interaction
• Reimagining the water snowline
• Velocity-resolved hot water emission detected toward HL Tau with the Submillimeter Array
• Water Ortho-to-Para ratio in the coma of comet 67P/Churyumov-Gerasimenko
• Inner disc and circumplanetary material in the PDS 70 system
• ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT) VII: the layered molecular outflow from HL Tau and its relationship with the ringed disk
• Understanding JWST water spectra: what can thermochemical models tell us about the (cold) water in protoplanetary disks?
• Water vapor emission at the warm cavity wall of the HD 100546 disk as revealed by ALMA

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