J/ApJ/778/16ivo://CDS.VizieR/J/ApJ/778/16doi:10.26093/cds/vizier.17780016CDSZeigler N.R.Zack L.N.Woolf N.J.Ziurys L.M.2015-06-10T18:46:20Z2015-05-15T13:02:25ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frplanetary-nebulaeradio-astronomyinterstellar-mediumThe J=1->0 transition of HCO^+^ at 89GHz has been mapped across the Helix Nebula (NGC 7293) with 70" spatial resolution (1.68km/s velocity resolution) using the Arizona Radio Observatory 12m telescope. This work is the first large-scale mapping project of a dense gas tracer (n(H_2_)~10^5^/cm3) in old planetary nebulae. Observations of over 200 positions encompassing the classical optical image were conducted with a 3{sigma} noise level of ~20mK. HCO^+^ was detected at most positions, often exhibiting multiple velocity components indicative of complex kinematic structures in dense gas. The HCO^+^ spectra suggest that the Helix is composed of a bipolar, barrel-like structure with red- and blue-shifted halves, symmetric with respect to the central star and oriented ~10{deg} east from the line of sight. A second bipolar, higher velocity outflow exists as well, situated along the direction of the Helix "plumes." The column density of HCO^+^ across the Helix is N_tot_~1.5x10^10^-5.0x10^11^/cm2, with an average value N_ave_~1x10^11^/cm2, corresponding to an abundance, relative to H_2_, of f~1.4x10^-8^. This value is similar to that observed in young PN, and contradicts chemical models, which predict that the abundance of HCO^+^ decreases with nebular age. This study indicates that polyatomic molecules readily survive the ultraviolet field of the central white dwarf, and can be useful in tracing nebular morphology in the very late stages of stellar evolution.2013ApJ...778...16Zhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/778/16CatalogResearchIsServedByTAP VizieR generic servicerelated-toV/84 : Strasbourg-ESO Catalogue of Galactic Planetary Nebulae (Acker+, 1992)J/ApJ/771/114 : Spectral analysis of evolved PNe from SPM (Pereyra+, 2013)J/MNRAS/431/2 : H{alpha} fluxes of Galactic planetary nebulae (Frew+, 2013)J/A+A/541/A98 : Interacting planetary nebulae (Ali+, 2012)J/A+A/526/A6 : Central stars of galactic planetary nebulae (Weidmann+, 2011)J/ApJ/724/748 : Galactic anticenter PNe and oxygen abundance (Henry+, 2010)J/ApJ/714/1096 : Galactic planetary nebulae (Stanghellini+, 2010)J/ApJ/689/194 : Distances of galactic planetary nebulae (Stanghellini+, 2008)J/A+A/479/155 : Proper motions of Galactic Planetary Nebulae (Kerber+, 2008)J/A+A/475/217 : Classification of planetary nebulae (Quireza+, 2007)J/MNRAS/349/793 : Galactic PNe abundances (Perinotto+, 2004)J/A+A/408/1029 : Coordinates of Galactic planetary nebulae (Kerber+, 2003)J/other/RMxAA/37.115 : Optical coordinates of southern PNe (Kimeswenger+, 2001)J/AJ/115/1989 : Distances of galactic planetary nebulae (Tajitsu+, 1998)J/ApJS/117/361 : PNe in NRAO VLA Sky Survey (Condon+ 1998)J/A+AS/132/13 : Planetary nebulae radial velocities (Durand+ 1998)J/A+A/318/256 : Planetary nebulae properties (Gorny+ 1997)J/A+AS/99/291 : CO & HCN observations of circumstellar envelopes (Loup+ 1993)J/A+AS/94/399 : Absolute fluxes and distances of PN (Cahn+, 1992)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/778/16https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/778/16http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/778/16https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/778/16https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/778/16http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/778/16GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapRadiodefaultJ/ApJ/778/16/table1Observations of HCO^+^(J=1-0) [89.1885GHz] in the Helix NebularecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintoRA[-525/525] Right Ascension offset (1)arcsecpos.eq.ra;arith.diffintoDE[-350/420] Declination offset (1)arcsecpos.eq.dec;arith.diffintl_TR*[<] Limit flag on TR*meta.code.errorcharTR*[6.7/107.5] Line intensitymKspect.line.intensityfloatFWHM[1.8/22]? Line widthkm/sspect.line.widthfloatnullableVLSR[-55.3/4]? Local Standard of Rest velocitykm/sspect.dopplerVelocfloatnullableNtot? HCO^+^ column densitycm**-2phys.columnDensitydoublenullablef(HCO+/H2)? Fractional HCO^+^/H_2_ abundancephys.abunddoublenullable