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Journal Articles The Astrophysical Journal Supplement Series Year : 2021

Molecules with ALMA at Planet-forming Scales (MAPS). IV. Emission Surfaces and Vertical Distribution of Molecules

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Charles J. Law
  • Function : Author
Richard Teague
Ryan A. Loomis
  • Function : Author
Jaehan Bae
Karin I. Öberg
  • Function : Author
Ian Czekala
  • Function : Author
Sean M. Andrews
  • Function : Author
Yuri Aikawa
Felipe Alarcón
  • Function : Author
Edwin A. Bergin
  • Function : Author
Jennifer B. Bergner
  • Function : Author
Alice S. Booth
  • Function : Author
Arthur D. Bosman
  • Function : Author
Jenny K. Calahan
  • Function : Author
Gianni Cataldi
  • Function : Author
L. Ilsedore Cleeves
  • Function : Author
Kenji Furuya
  • Function : Author
Viviana V. Guzmán
  • Function : Author
Jane Huang
  • Function : Author
John D. Ilee
  • Function : Author
Yao Liu
  • Function : Author
Feng Long
  • Function : Author
Hideko Nomura
Laura M. Pérez
  • Function : Author
Chunhua Qi
Kamber R. Schwarz
  • Function : Author
Daniela Soto
  • Function : Author
Takashi Tsukagoshi
Yoshihide Yamato
  • Function : Author
Merel L. R. Van'T Hoff
  • Function : Author
Catherine Walsh
  • Function : Author
David J. Wilner
  • Function : Author
Ke Zhang
  • Function : Author

Abstract

The Molecules with ALMA at Planet-forming Scales (MAPS) Large Program provides a unique opportunity to study the vertical distribution of gas, chemistry, and temperature in the protoplanetary disks around IM Lup, GM Aur, AS 209, HD 163296, and MWC 480. By using the asymmetry of molecular line emission relative to the disk major axis, we infer the emission height (z) above the midplane as a function of radius (r). Using this method, we measure emitting surfaces for a suite of CO isotopologues, HCN, and C2H. We find that 12CO emission traces the most elevated regions with $z/r 0.3$ , while emission from the less abundant 13CO and C18O probes deeper into the disk at altitudes of $z/r\,\lesssim \,0.2$ . C2H and HCN have lower opacities and signal-to-noise ratios, making surface fitting more difficult, and could only be reliably constrained in AS 209, HD 163296, and MWC 480, with $z/r\,\lesssim \,0.1$ , i.e., relatively close to the planet-forming midplanes. We determine peak brightness temperatures of the optically thick CO isotopologues and use these to trace 2D disk temperature structures. Several CO temperature profiles and emission surfaces show dips in temperature or vertical height, some of which are associated with gaps and rings in line and/or continuum emission. These substructures may be due to local changes in CO column density, gas surface density, or gas temperatures, and detailed thermochemical models are necessary to better constrain their origins and relate the chemical compositions of elevated disk layers with those of planet-forming material in disk midplanes. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.

Dates and versions

insu-03672377 , version 1 (19-05-2022)

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Charles J. Law, Richard Teague, Ryan A. Loomis, Jaehan Bae, Karin I. Öberg, et al.. Molecules with ALMA at Planet-forming Scales (MAPS). IV. Emission Surfaces and Vertical Distribution of Molecules. The Astrophysical Journal Supplement Series, 2021, 257, ⟨10.3847/1538-4365/ac1439⟩. ⟨insu-03672377⟩
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