J/ApJ/778/16 Observations of HCO^+^ in NGC 7293 (Zeigler+, 2013) ================================================================================ The Helix Nebula viewed in HCO^+^: large-scale mapping of the J=1->0 transition. Zeigler N.R., Zack L.N., Woolf N.J., Ziurys L.M. =2013ApJ...778...16Z ================================================================================ ADC_Keywords: Planetary nebulae ; Radio lines ; Interstellar medium Keywords: astrochemistry; ISM: molecules; planetary nebulae: individual: NGC 7293; radio lines: ISM Abstract: The 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. Description: The observations were conducted between 2008 November and 2013 March using the 12m telescope of the Arizona Radio Observatory (ARO) at Kitt Peak, AZ. The J=1->0 transition of HCO^+^ at 89188.5MHz was observed at 219 positions in the nebula. Objects: ------------------------------------------------------ RA (ICRS) DE Designation(s) ------------------------------------------------------ 22 29 38.54 -20 50 13.6 Helix Nebula = NGC 7293 ------------------------------------------------------ File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 45 327 Observations of HCO^+^(J=1-0) [89.1885GHz] in the Helix Nebula -------------------------------------------------------------------------------- See also: V/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) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 I4 arcsec oRA [-525/525] Right Ascension offset (1) 6- 9 I4 arcsec oDE [-350/420] Declination offset (1) 11 A1 --- l_TR* [<] Limit flag on TR* 12- 16 F5.1 mK TR* [6.7/107.5] Line intensity 18- 21 F4.1 km/s FWHM [1.8/22]? Line width 23- 27 F5.1 km/s VLSR [-55.3/4]? Local Standard of Rest velocity 29- 36 E8.4 cm-2 Ntot ? HCO^+^ column density 38- 45 E8.4 --- f(HCO+/H2) ? Fractional HCO^+^/H_2_ abundance -------------------------------------------------------------------------------- Note (1): From central star position with J2000 coordinates: 22:29:38.6-20:50:18 (J2000) -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 22-Apr-2015