Molecules with ALMA at Planet-forming Scales (MAPS). VIII. CO gap in AS 209-gas depletion or chemical processing?
Abstract
Emission substructures in gas and dust are common in protoplanetary disks. Such substructures can be linked to planet formation or planets themselves. We explore the observed gas substructures in AS 209 using thermochemical modeling with RAC2D and high-spatial-resolution data from the Molecules with ALMA at Planet-forming Scales (MAPS) program. The observations of C18O J = 2-1 emission exhibit a strong depression at 88 au overlapping with the positions of multiple gaps in millimeter dust continuum emission. We find that the observed CO column density is consistent with either gas surface-density perturbations or chemical processing, while C2H column density traces changes in the C/O ratio rather than the H2 gas surface density. However, the presence of a massive planet (>0.2 MJup) would be required to account for this level of gas depression, which conflicts with constraints set by the dust emission and the pressure profile measured by gas kinematics. Based on our models, we infer that a local decrease of CO abundance is required to explain the observed structure in CO, dominating over a possible gap-carving planet present and its effect on the H2 surface density. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.
Citation
Alarcón , F , Bosman , A D , Bergin , E A , Zhang , K , Teague , R , Bae , J , Aikawa , Y , Andrews , S M , Booth , A S , Calahan , J K , Cataldi , G , Czekala , I , Huang , J , Ilee , J D , Law , C J , Le Gal , R , Liu , Y , Long , F , Loomis , R A , Ménard , F , Öberg , K I , Schwarz , K R , van't Hoff , M L R , Walsh , C & Wilner , D J 2021 , ' Molecules with ALMA at Planet-forming Scales (MAPS). VIII. CO gap in AS 209-gas depletion or chemical processing? ' , Astrophysical Journal Supplement Series , vol. 257 , no. 1 , 8 . https://doi.org/10.3847/1538-4365/ac22ae
Publication
Astrophysical Journal Supplement Series
Status
Peer reviewed
ISSN
0067-0049Type
Journal article
Description
Funding: I.C. was supported by NASA through the NASA Hubble Fellowship grant HST-HF2-51405.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. J.D.I. acknowledges support from the Science and Technology Facilities Council of the United Kingdom (STFC) under ST/T000287/1. C.W. acknowledges financial support from the University of Leeds, SFTC, and UKRI (grant Nos. ST/R000549/1, ST/T000287/1, and MR/T040726/1).Collections
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