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dc.contributor.authorSchmidt, D. R.
dc.contributor.authorZack, L. N.
dc.contributor.authorZiurys, L. M.
dc.date.accessioned2019-01-25T23:49:34Z
dc.date.available2019-01-25T23:49:34Z
dc.date.issued2018-09-10
dc.identifier.citationD. R. Schmidt et al 2018 ApJL 864 L31en_US
dc.identifier.issn2041-8213
dc.identifier.doi10.3847/2041-8213/aadc09
dc.identifier.urihttp://hdl.handle.net/10150/631585
dc.description.abstractThe hydrocarbons CCH and c-C3H2 have been detected at multiple positions distributed across the Helix, along with the CN, indicating that these molecules are present throughout this very old planetary nebula. The species were identified by observations of the N = 1 -> 0 transitions of CCH and CN and the J = 2(1,2) -> 10,1 transition of c-C3H2, conducted with the new Atacama Large Millimeter/submillimeter Array (ALMA) prototype 12 m antenna of the Arizona Radio Observatory at 3 mm in wavelength. Column densities of the three species were calculated to be N-tot(CCH) similar to (0.8-6.6) x 10(12) cm(-2), N-tot(c-C3H2) similar to (0.3-5.9). x 10(11) cm(-2), and Ntot(CN) similar to (0.7-7.4). x. 10(12) cm(-2), corresponding to fractional abundances, with respect to H-2, of f(CCH) similar to (1.1-8.8). x. 10(-7), f (c-C3H2) similar to (0.4-7.9) x 10(-8), and f(CN) similar to (0.9-9.9) x 10(-7). Surprisingly, the abundances are comparable to those measured in younger planetary nebulae (PNe), indicating that predicted photodestruction processes for gas-phase molecules are inefficient in these objects, even over long timescales. The distributions of these two hydrocarbons in the Helix appear to be correlated, with a ratio of [CCH]/[c-C3H2] similar to 5-80 and an average value of 29 +/- 6-remarkably similar to both the range ([CCH]/[c-C3H2] similar to 11-53) and average value (28.2 +/- 1.4) found in diffuse clouds. The abundances of CCH, c-C3H2, and CN in the Helix are also factors of 10-100 greater than those measured in diffuse gas. These results suggest that molecular ejecta from PNe are a possible external source for polyatomic species found in diffuse clouds, including C-60.en_US
dc.description.sponsorshipNSF [AST-1515568]en_US
dc.language.isoenen_US
dc.publisherIOP PUBLISHING LTDen_US
dc.relation.urlhttp://stacks.iop.org/2041-8205/864/i=2/a=L31?key=crossref.b5a2d7d0700da12fdc6000cf40e9ee0fen_US
dc.rights© 2018. The American Astronomical Society. All rights reserved.en_US
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/
dc.subjectastrochemistryen_US
dc.subjectISM: moleculesen_US
dc.subjectplanetary nebulae: individual (NGC 7293)en_US
dc.subjectradio lines: ISMen_US
dc.titleWidespread CCH and c-C3H2 in the Helix Nebula: Unraveling the Chemical History of Hydrocarbonsen_US
dc.typeArticleen_US
dc.contributor.departmentUniv Arizona, Steward Observen_US
dc.contributor.departmentUniv Arizona, Dept Chem & Biochemen_US
dc.identifier.journalASTROPHYSICAL JOURNAL LETTERSen_US
dc.description.collectioninformationThis 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 repository@u.library.arizona.edu.en_US
dc.eprint.versionFinal published versionen_US
dc.source.journaltitleThe Astrophysical Journal
dc.source.volume864
dc.source.issue2
dc.source.beginpageL31
refterms.dateFOA2019-01-25T23:49:34Z


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