Spiral Structure in the Gas Disk of TW Hya

Abstract

We report the detection of spiral substructure in both the gas velocity and temperature structure of the disk around TW~Hya, suggestive of planet-disk interactions with an unseen planet. Perturbations from Keplerian rotation tracing out a spiral pattern are observed in the SE of the disk, while significant azimuthal perturbations in the gas temperature are seen in the outer disk, outside 90~au, extending the full azimuth of the disk. The deviation in velocity is either $\Delta v_{\varphi }/v_{\mathrm{kep}}\sim 0.1$ or $\Delta v_z/v_{\mathrm{kep}}\sim 0.01$ depending on whether the perturbation is in the rotational or vertical direction, while radial perturbations can be ruled out. Deviations in the gas temperature are $\pm 4$ K about the azimuthally averaged profile, equivalent to deviations of $\Delta T_{\mathrm{gas}}/T_{\mathrm{gas}}\sim 0.05$. Assuming all three structures can be described by an Archimedean spiral, measurements of the pitch angles of both velocity and temperature spirals show a radially decreasing trend for all three, ranging from 9${}^{\circ }$ at 70 au, dropping to 3${}^{\circ }$ at 200 au. Such low pitch-angled spirals are not readily explained through the wake of an embedded planet in the location of previously reported at 94 au, but rather require a launching mechanism which results in much more tightly wound spirals. Molecular emission tracing distinct heights in the disk is required to accurately distinguish between spiral launching mechanisms.

Accepted to ApJL

References in corpus (9)

• Gaps, Rings, and Non-Axisymmetric Structures in Protoplanetary Disks - From Simulations to ALMA Observations
• Three radial gaps in the disk of TW Hydrae imaged with SPHERE
• Direct mapping of the temperature and velocity gradients in discs. Imaging the vertical CO snow line around IM Lupi
• Formation of a disc gap induced by a planet: Effect of the deviation from Keplerian disc rotation
• CO and dust properties in the TW Hya disk from high-resolution ALMA observations
• Spiral arms in the disk of HD 142527 from CO emission lines with ALMA
• Chasing Shadows: Rotation of the Azimuthal Asymmetry in the TW Hya Disk
• A Surface Density Perturbation in the TW Hydrae Disk at 95 au Traced by Molecular Emission
• Spiral arms in thermally stratified protoplanetary discs

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• Mapping the Complex Kinematic Substructure in the TW Hya Disk
• Large-scale CO spiral arms and complex kinematics associated with the T Tauri star RU Lup
• exoALMA V: Gaseous Emission Surfaces and Temperature Structures
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• exoALMA. VI. Rotating under Pressure: Rotation curves, azimuthal velocity substructures, and pressure variations
• Three-temperature radiation hydrodynamics with PLUTO: Tests and applications to protoplanetary disks
• The surprising evolution of the shadow on the TW Hya disk
• Detection of HC18O+ in a protoplanetary disk: exploring oxygen isotope fractionation of CO
• Discovery of Line Pressure Broadening and Direct Constraint on Gas Surface Density in a Protoplanetary Disk
• Particle Dynamics in 3D Self-gravitating Disks I: Spirals
• Chemical signatures of a warped protoplanetary disc
• A Simple Time-Dependent Method for Calculating Spirals: Applications to Eccentric Planets in Protoplanetary discs
• exoALMA. XVII. Characterizing the Gas Dynamics around Dust Asymmetries
• Characteristics of small protoplanetary disc warps in kinematic observations
• ALMA High-resolution Multiband Analysis for the Protoplanetary Disk around TW Hya
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• Observational Signatures of Planets in Protoplanetary Disks: Temperature structures in spiral arms
• Gas and Dust Shadows in the TW Hydrae Disk