J/A+A/629/A146ivo://CDS.VizieR/J/A+A/629/A146doi:10.26093/cds/vizier.36290146CDSVelilla-Prieto L.Cernicharo J.Agundez M.Fonfria J.P.,Quintana-Lacaci G.Marcelino N.Castro-Carrizo A.2019-12-06T08:03:00Z2019-09-18T07:47:50ZCDS support team

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

cds-question@unistra.frlate-type-starsradio-astronomyLow-mass evolved stars are major contributors to interstellar medium enrichment as a consequence of the intense mass-loss process these stars experience at the end of their lives. The study of the gas in the envelopes surrounding asymptotic giant branch (AGB)stars through observations in the millimetre wavelength range provides information about the history and nature of these molecular factories. Here we present ALMA observations at subarsecond resolution, complemented with IRAM-30m data, of several lines of SiO, SiS, and CS towards the best-studied AGB circumstellar envelope, IRC+10 216. We aim to characterise their spatial distribution and determine their fractional abundances mainly through radiative transfer and chemical modelling. The three species display extended emission with several enhanced emission shells. CS displays the most extended distribution reaching distances up to ap-proximately 20". SiS and SiO emission have similar sizes of approximately 11", but SiS emission is slightly more compact. We have estimated fractional abundances relative to H_2_, which on average are equal to f(SiO)~10^-7^, f(SiS)~10^-6^, and f(CS)~10^-^6 up to the photo-dissociation region. The observations and analysis presented here show evidence that the circumstellar material displays clear deviations from an homogeneous spherical wind, with clumps and low density shells that may allow UV photons from the interstellar medium (ISM) to penetrate deep into the envelope, shifting the photo-dissociation radius inwards. Our chemical model predicts photo-dissociation radii compatible with those derived from the observations, although it is unable to predict abundance variations from the starting radius of the calculations (~10R_{sun}_), which may reflect the simplicity of the model. We conclude that the spatial distribution of the gas proves the episodic and variable nature of the mass loss mechanism of IRC+10 216, on timescales of hundreds of years2019A&A...629A.146Vhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/629/A146CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/330/676 : IRC+10216 Silicon and sulfur chemistry (Willacy+ 1998)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/A12u : Chemistry of IRC+10216 inner wind modelled (Cherchneff, 2012)J/A+A/574/A56 : IRC+10216 17.8GHz-26.3GHz spectrum (Gong+, 2015)J/ApJ/806/L3 : Disilicon carbide (SiCSi) discovery in CW LeoJ/A+A/601/A4 : IRC+10216 carbon chains mapped with ALMA (Agundez+, 2017)J/A+A/606/A74 : IRC+10216 13.3GHz-18.5GHz spectrum (Zhang+, 2017)J/A+A/618/A4 : IRC+10216 as a spectroscopic laboratory (Cernicharo+, 2018)J/ApJ/688/L83 : Detection of C_5_N^-^ in IRC +10216 (Cernicharo+, 2008)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/629/A146https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/629/A146http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/629/A146https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/629/A146https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/629/A146http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/629/A146GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/629/A146/list (List of datacubes)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/629/A146/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/629/A146/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/629/A146/list?GETtext/xml+votable180.050000true146.9893413.278840.0055555555555555566/4365https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/629/A146?format=asciiRadiodefaultJ/A+A/629/A146/listList of datacubesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension of center (J2000)degpos.eq.ra;meta.mainDEJ2000Declination of center (J2000)degpos.eq.dec;meta.mainNxNumber of pixels along X-axismeta.numberintNyNumber of pixels along Y-axismeta.numberintNzNumber of slicesmeta.numberintbVRADLower value of VRAD intervalm/sphys.velocdoubleBVRADUpper value of VRAD intervalm/sphys.velocdoubledVRADVRAD resolutionm/sspect.resolutionfloatsizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fits