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3D modelling of HCO$^+$ and its isotopologues in the low-mass proto-star IRAS16293$-$2422

hal.structure.identifierInstitut de recherche en astrophysique et planétologie [IRAP]
dc.contributor.authorQUENARD, D.
hal.structure.identifierInstitut de recherche en astrophysique et planétologie [IRAP]
dc.contributor.authorBOTTINELLI, S.
hal.structure.identifierInstitut de recherche en astrophysique et planétologie [IRAP]
dc.contributor.authorCAUX, E.
hal.structure.identifierAMOR 2018
dc.contributor.authorWAKELAM, Valentine
dc.date.issued2018
dc.identifier.issn0035-8711
dc.description.abstractEnIons and electrons play an important role in various stages of the star formation process. By following the magnetic field of their environment and interacting with neutral species, they slow down the gravitational collapse of the proto-star envelope. This process (known as ambipolar diffusion) depends on the ionisation degree, which can be derived from the \hco abundance. We present a study of \hco and its isotopologues (H$^{13}$CO$^+$, HC$^{18}$O$^+$, DCO$^+$, and H$^{13}$CO$^+$) in the low-mass proto-star IRAS16293$-$2422. The structure of this object is complex, and the HCO$^+$ emission arises from the contribution of a young NW-SE outflow, the proto-stellar envelope and the foreground cloud. We aim at constraining the physical parameters of these structures using all the observed transitions. For the young NW-SE outflow, we derive $T_{\rm kin}=180-220$ K and $n({\rm H_2})=(4-7)\times10^6$ cm$^{-3}$ with an HCO$^+$ abundance of $(3-5)\times10^{-9}$. Following previous studies, we demonstrate that the presence of a cold ($T_{\rm kin}$$\leqslant$30 K) and low density ($n({\rm H_2})\leqslant1\times10^4$ cm$^{-3}$) foreground cloud is also necessary to reproduce the observed line profiles. We have used the gas-grain chemical code \textsc{nautilus} to derive the HCO$^+$ abundance profile across the envelope and the external regions where X(HCO$^+$)$\gtrsim1\times10^{-9}$ dominate the envelope emission. From this, we derive an ionisation degree of $10^{-8.9}\,\lesssim\,x(e)\,\lesssim\,10^{-7.9}$. The ambipolar diffusion timescale is $\sim$5 times the free-fall timescale, indicating that the magnetic field starts to support the source against gravitational collapse and the magnetic field strength is estimated to be $6-46 \mu$G.
dc.language.isoen
dc.publisherOxford University Press (OUP): Policy P - Oxford Open Option A
dc.title.en3D modelling of HCO$^+$ and its isotopologues in the low-mass proto-star IRAS16293$-$2422
dc.typeArticle de revue
dc.identifier.doi10.1093/mnras/sty1004
dc.subject.halPlanète et Univers [physics]/Astrophysique [astro-ph]/Cosmologie et astrophysique extra-galactique [astro-ph.CO]
dc.identifier.arxiv1804.07590
bordeaux.journalMonthly Notices of the Royal Astronomical Society
bordeaux.page5312-5326
bordeaux.volume477
bordeaux.issue4
bordeaux.peerReviewedoui
hal.identifierhal-01773955
hal.version1
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-01773955v1
bordeaux.COinSctx_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.jtitle=Monthly%20Notices%20of%20the%20Royal%20Astronomical%20Society&rft.date=2018&rft.volume=477&rft.issue=4&rft.spage=5312-5326&rft.epage=5312-5326&rft.eissn=0035-8711&rft.issn=0035-8711&rft.au=QUENARD,%20D.&BOTTINELLI,%20S.&CAUX,%20E.&WAKELAM,%20Valentine&rft.genre=article


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