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.
<Astrophys. J., 778, 16 (2013)>
=2013ApJ...778...16Z 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(H2)∼105/cm3) in old planetary nebulae. Observations of over 200
positions encompassing the classical optical image were conducted with
a 3σ 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° 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 Ntot∼1.5x1010-5.0x1011/cm2, with an average value
Nave∼1x1011/cm2, corresponding to an abundance, relative to H2,
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:
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RA (ICRS) DE Designation(s)
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22 29 38.54 -20 50 13.6 Helix Nebula = NGC 7293
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 45 327 Observations of HCO+(J=1-0) [89.1885GHz]
in the Helix Nebula
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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 : Hα 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
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Bytes Format Units Label Explanations
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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+/H2 abundance
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Note (1): From central star position with J2000 coordinates:
22:29:38.6-20:50:18 (J2000)
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 22-Apr-2015