Multiple Disk Gaps and Rings Generated by a Single Super-Earth. II. Spacings, Depths, and Number of Gaps, with Application to Real Systems

Ruobing 若冰 Dong 董,Hui 晖 Li 李,Eugene 詒曾 Chiang 蔣,Shengtai 胜台 Li 李

doi:10.3847/1538-4357/aadadd

Ruobing 若冰 Dong 董, Hui 晖 Li 李 + Show 2 more

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https://doi.org/10.3847/1538-4357/aadadd

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Abstract

Abstract The Atacama Large Millimeter/submillimeter Array (ALMA) has found multiple dust gaps and rings in a number of protoplanetary disks in continuum emission at millimeter wavelengths. The origin of such structures is under debate. Recently, we documented how one super-Earth planet can open multiple (up to five) dust gaps in a disk with low viscosity (α ≲ 10−4). In this paper, we examine how the positions, depths, and total number of gaps opened by one planet depend on input parameters, and apply our results to real systems. Gap locations (equivalently, spacings) are the easiest metric to use when making comparisons between theory and observations, as positions can be robustly measured. We fit the locations of gaps empirically as functions of planet mass and disk aspect ratio. We find that the locations of the double gaps in HL Tau and TW Hya, and of all three gaps in HD 163296, are consistent with being opened by a sub-Saturn mass planet. This scenario predicts the locations of other gaps in HL Tau and TW Hya, some of which appear consistent with current observations. We also show how the Rossby wave instability may develop at the edges of several gaps and result in multiple dusty vortices, all caused by one planet. A planet as low in mass as Mars may produce multiple dust gaps in the terrestrial planet-forming region.

Highlights

The Atacama Large Millimeter Array (ALMA) has discovered multiple gaps and rings in a number of protoplanetary disks in dust continuum emission at millimeter wavelengths at ∼10–100 AU
We find that the locations of the double gaps in HL Tau and TW Hya, and of all three gaps in HD 163296, are consistent with being opened by a sub-Saturn mass planet
We show how the Rossby wave instability may develop at the edges of several gaps and result in multiple dusty vortices, all caused by one planet

Summary

Introduction

The Atacama Large Millimeter Array (ALMA) has discovered multiple gaps and rings in a number of protoplanetary disks in dust continuum emission at millimeter (mm) wavelengths at ∼10–100 AU. Examples include the disk around HL Tau (ALMA Partnership et al 2015), TW Hya (Andrews et al 2016; Tsukagoshi et al 2016), HD 163296 (Isella et al 2016), AS 209 (Fedele et al 2018), AA Tau (Loomis et al 2017), Elias 24 (Cieza et al 2017; Cox et al 2017; Dipierro et al 2018), GY 91 (Sheehan & Eisner 2018), and V1094 Sco (Ansdell et al 2018; van Terwisga et al 2018). The origins of these gaps are being debated. In planet-disk interaction scenarios, even super-Earth planets may open dust gaps

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