Molecules with ALMA at Planet-forming Scales (MAPS) XVII: Determining the 2D Thermal Structure of the HD 163296 Disk

TL;DR

This study models the 2D thermal structure of the HD 163296 protoplanetary disk using ALMA data and thermo-chemical simulations, revealing temperature variations and the impact of gaps on disk heating.

Contribution

It presents a detailed thermo-chemical model of the HD 163296 disk that reproduces multiple observational datasets, including CO lines and continuum, and assesses the effects of gaps on disk temperature.

Findings

The disk mass is constrained to less than 0.35 solar masses.

A radial CO depletion timescale of 0.01 Myr is inferred.

Gaps increase local gas temperature by only 5-10%.

Abstract

Understanding the temperature structure of protoplanetary disks is key to interpreting observations, predicting the physical and chemical evolution of the disk, and modeling planet formation processes. In this study, we constrain the two-dimensional thermal structure of the disk around Herbig Ae star HD 163296. Using the thermo-chemical code RAC2D, we derive a thermal structure that reproduces spatially resolved ALMA observations (~0.12 arcsec (13 au) - 0.25 arcsec (26 au)) of CO J = 2-1, 13CO J = 1-0, 2-1, C18O J = 1-0, 2-1, and C17O J = 1-0, the HD J = 1-0 flux upper limit, the spectral energy distribution (SED), and continuum morphology. The final model incorporates both a radial depletion of CO motivated by a time scale shorter than typical CO gas-phase chemistry (0.01 Myr) and an enhanced temperature near the surface layer of the the inner disk (z/r <= 0.21). This model agrees with the majority of the empirically derived temperatures and observed emitting surfaces derived from the J = 2-1 CO observations. We find an upper limit for the disk mass of 0.35 Msun, using the upper limit of the HD J = 1-0 and J = 2-1 flux. With our final thermal structure, we explore the impact that gaps have on the temperature structure constrained by observations of the resolved gaps. Adding a large gap in the gas and small dust additionally increases gas temperature in the gap by only 5-10%. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.