Line Ratios Reveal N2H+ Emission Originates above the Midplane in TW Hydrae
AffiliationUniv Arizona, Lunar & Planetary Lab
MetadataShow full item record
PublisherIOP PUBLISHING LTD
CitationKamber R. Schwarz et al 2019 ApJL 876 L13
JournalASTROPHYSICAL JOURNAL LETTERS
RightsCopyright © 2019. The American Astronomical Society. All rights reserved.
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at email@example.com.
AbstractLine ratios for different transitions of the same molecule have long been used as a probe of gas temperature. Here we use ALMA observations of the N2H+ J= 1-0 and J = 4-3 lines in the protoplanetary disk around TW Hya to derive the temperature at which these lines emit. We find an averaged temperature of 39 K with a 1 sigma uncertainty of 2 K for the radial range 0.'' 8-2 '', which is significantly warmer than the expected midplane temperature beyond 0 ''.5 in this disk. We conclude that the N2H+ emission in TW Hya is not emitting from near the midplane, but rather from higher in the disk, in a region likely bounded by processes such as photodissociation or chemical reprocessing of CO and N-2 rather than freeze-out.
VersionFinal published version
SponsorsNSF [AST-1514670]; NASA [NNX16AB48G, NAS526555]; NASA through Hubble Fellowship Program - Space Telescope Science Institute [HST-HF251419.001]