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dc.contributor.authorBergner, Jennifer B.
dc.contributor.authorÖberg, Karin I.
dc.contributor.authorGuzmán, Viviana V.
dc.contributor.authorLaw, Charles J.
dc.contributor.authorLoomis, Ryan A.
dc.contributor.authorCataldi, Gianni
dc.contributor.authorBosman, Arthur D.
dc.contributor.authorAikawa, Yuri
dc.contributor.authorAndrews, Sean M.
dc.contributor.authorBergin, Edwin A.
dc.contributor.authorBooth, Alice S.
dc.contributor.authorCleeves, L. Ilsedore
dc.contributor.authorCzekala, Ian
dc.contributor.authorHuang, Jane
dc.contributor.authorIlee, John D.
dc.contributor.authorLe Gal, Romane
dc.contributor.authorLong, Feng
dc.contributor.authorNomura, Hideko
dc.contributor.authorMénard, François
dc.contributor.authorQi, Chunhua
dc.contributor.authorSchwarz, Kamber R.
dc.contributor.authorTeague, Richard
dc.contributor.authorTsukagoshi, Takashi
dc.contributor.authorWalsh, Catherine
dc.contributor.authorWilner, David J.
dc.contributor.authorYamato, Yoshihide
dc.identifier.citationBergner , J B , Öberg , K I , Guzmán , V V , Law , C J , Loomis , R A , Cataldi , G , Bosman , A D , Aikawa , Y , Andrews , S M , Bergin , E A , Booth , A S , Cleeves , L I , Czekala , I , Huang , J , Ilee , J D , Le Gal , R , Long , F , Nomura , H , Ménard , F , Qi , C , Schwarz , K R , Teague , R , Tsukagoshi , T , Walsh , C , Wilner , D J & Yamato , Y 2021 , ' Molecules with ALMA at Planet-forming Scales (MAPS). XI. CN and HCN as tracers of photochemistry in disks ' , Astrophysical Journal Supplement Series , vol. 257 , no. 1 , 11 .
dc.identifier.otherPURE: 295925304
dc.identifier.otherPURE UUID: ef7ebac4-a3a6-43f6-a517-6b7a5bc8f364
dc.identifier.otherBibCode: 2021ApJS..257...11B
dc.identifier.otherScopus: 85119669786
dc.identifier.otherORCID: /0000-0002-1483-8811/work/146464278
dc.descriptionFunding: 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. A.S.B. acknowledges the studentship funded by the Science and Technology Facilities Council of the United Kingdom (STFC). 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, STFC, and UKRI (grant Nos. ST/R000549/1, ST/T000287/1, MR/T040726/1).en
dc.description.abstractUV photochemistry in the surface layers of protoplanetary disks dramatically alters their composition relative to previous stages of star formation. The abundance ratio CN/HCN has long been proposed to trace the UV field in various astrophysical objects; however, to date the relationship between CN, HCN, and the UV field in disks remains ambiguous. As part of the ALMA Large Program MAPS (Molecules with ALMA at Planet-forming Scales), we present observations of CN N = 1-0 transitions at 0.″3 resolution toward five disk systems. All disks show bright CN emission within ~50-150 au, along with a diffuse emission shelf extending up to 600 au. In all sources we find that the CN/HCN column density ratio increases with disk radius from about unity to 100, likely tracing increased UV penetration that enhances selective HCN photodissociation in the outer disk. Additionally, multiple millimeter dust gaps and rings coincide with peaks and troughs, respectively, in the CN/HCN ratio, implying that some millimeter substructures are accompanied by changes to the UV penetration in more elevated disk layers. That the CN/HCN ratio is generally high (>1) points to a robust photochemistry shaping disk chemical compositions and also means that CN is the dominant carrier of the prebiotically interesting nitrile group at most disk radii. We also find that the local column densities of CN and HCN are positively correlated despite emitting from vertically stratified disk regions, indicating that different disk layers are chemically linked. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.
dc.relation.ispartofAstrophysical Journal Supplement Seriesen
dc.rightsCopyright © 2021 The American Astronomical Society. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the final published version of the work, which was originally published at
dc.subjectProtoplanetary disksen
dc.subjectInterstellar moleculesen
dc.subjectQB Astronomyen
dc.subjectQC Physicsen
dc.titleMolecules with ALMA at Planet-forming Scales (MAPS). XI. CN and HCN as tracers of photochemistry in disksen
dc.typeJournal articleen
dc.description.versionPublisher PDFen
dc.contributor.institutionUniversity of St Andrews. School of Physics and Astronomyen
dc.description.statusPeer revieweden

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