J/A+A/601/A4 IRC+10216 carbon chains mapped with ALMA (Agundez+, 2017)
Growth of carbon chains in IRC+10216 mapped with ALMA.
Agundez M., Cernicharo J., Quintana-Lacaci G., Castro-Carrizo A.,
Velilla Prieto L., Marcelino N., Guelin M., Joblin C., Martin-Gago J.A.,
Gottlieb C.A., Patel N.A., McCarthy M.C.
<Astron. Astrophys. 601, A4 (2017)>
=2017A&A...601A...4A 2017A&A...601A...4A (SIMBAD/NED BibCode)
ADC_Keywords: Stars, carbon ; Radio lines
Keywords: astrochemistry - molecular processes - techniques: interferometric -
stars: AGB and post-AGB - circumstellar matter - radio lines: stars
Abstract:
Linear carbon chains are common in various types of astronomical
molecular sources. Possible formation mechanisms involve both
bottom-up and top-down routes. We have carried out a combined
observational and modeling study of the formation of carbon chains in
the C-star envelope IRC +10216, where the polymerization of acetylene
and hydrogen cyanide induced by ultraviolet photons can drive the
formation of linear carbon chains of increasing length. We have used
ALMA to map the emission of 3 mm rotational lines of the hydrocarbon
radicals C2H, C4H, and C6H, and the CN-containing species CN,
C3N, HC3N, and HC5N with an angular resolution of 1". The
spatial distribution of all these species is a hollow 5-10" wide
spherical shell located at a radius of 10-20" from the star, with no
appreciable emission close to the star. Our observations resolve the
broad shell of carbon chains into thinner subshells that are 1-2"
wide and not fully concentric, indicating that the mass-loss process
has been discontinuous and not fully isotropic. The radial
distributions of the species mapped reveal subtle differences: while
the hydrocarbon radicals have very similar radial distributions, the
CN-containing species show more diverse distributions, with HC3N
appearing earlier in the expansion and the radical CN extending later
than the rest of the species. The observed morphology can be
rationalized by a chemical model in which the growth of polyynes is
mainly produced by rapid gas-phase chemical reactions of C2H and
C4H radicals with unsaturated hydrocarbons, while cyanopolyynes are
mainly formed from polyynes in gas-phase reactions with CN and C3N
radicals.
Description:
The FITS files contain the emission maps of carbon chains shown in
Figures 1, A1, A2, A3, A4, and A5 of the article.
Objects:
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RA (2000) DE Designation(s)
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09 47 57.41 +13 16 43.6 IRC+10216 = V* CW Leo
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 99 26 List of fits images
fits/* . 26 Individual fits images
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See also:
J/A+A/330/676 : IRC+10216 Silicon and sulfur chemistry (Willacy+ 1998)
J/ApJ/688/L83 : Detection of C5N- in IRC +10216 (Cernicharo+, 2008)
J/ApJS/177/275 : 1.3 and 2mm survey of IRC+10216 (He+, 2008)
J/ApJS/190/348 : 1mm spectral survey of IRC+10216 + VY CMa (Tenenbaum+, 2010)
J/ApJS/193/17 : Spectral-line survey of IRC+10216 at 293-355GHz (Patel+, 2011)
J/A+A/545/A12 : Chemistry of IRC+10216 inner wind modelled (Cherchneff, 2012)
J/ApJ/806/L3 : Disilicon carbide (SiCSi) in CW Leo (Cernicharo+, 2015)
J/A+A/574/A56 : IRC +10216 17.8GHz-26.3GHz spectrum (Gong+, 2015)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 37 F8.1 m/s RV Radial velocity
39- 43 I5 Kibyte size Size of FITS file
45- 60 A16 --- FileName Name of FITS file, in subdirectory fits
62- 99 A38 --- Title Title of the FITS file
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Acknowledgements:
Marcelino Agundez, marcelino.agundez(at)icmm.csic.es
(End) Marcelino Agundez [ICMM], Patricia Vannier [CDS] 24-Apr-2017