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Measuring Turbulence in TW Hya with ALMA: Methods and Limitations

dc.contributor.authorTEAGUE, Richard,
hal.structure.identifierAMOR 2016
dc.contributor.authorGUILLOTEAU, S.
dc.contributor.authorSEMENOV, Dmitry,
dc.contributor.authorHENNING, Thomas,
hal.structure.identifierAMOR 2016
dc.contributor.authorDUTREY, Anne
hal.structure.identifierInstitut de RadioAstronomie Millimétrique [IRAM]
dc.contributor.authorPIETU, Vincent,
dc.contributor.authorBIRNSTIEL, Tilman,
hal.structure.identifierAMOR 2016
dc.contributor.authorCHAPILLON, E.
dc.contributor.authorHOLLENBACH, David,
dc.contributor.authorGORTI, Uma,
dc.date.issued2016-05
dc.identifier.issn0004-6361
dc.description.abstractEnWe obtain high spatial and spectral resolution images of the CO J=2-1, CN N=2-1 and CS J=5-4 emission with ALMA in Cycle~2. The radial distribution of the turbulent broadening is derived with three approaches: two `direct' and one modelling. The first requires a single transition and derives \Tex{} directly from the line profile, yielding a \vturb{}. The second assumes two different molecules are co-spatial thus their relative linewidths allow for a calculation of \Tkin{} and \vturb{}. Finally we fit a parametric disk model where physical properties of the disk are described by power laws, to compare our `direct' methods with previous values. The two direct methods were limited to the outer $r > 40$~au disk due to beam smear. The direct method found \vturb{} ranging from $\approx$~\vel{130} at 40~au, dropping to $\approx$~\vel{50} in the outer disk, qualitatively recovered with the parametric model fitting. This corresponds to roughly $0.2 - 0.4~c_s$. CN was found to exhibit strong non-LTE effects outside $r \approx 140$~au, so \vturb{} was limited to within this radius. The assumption that CN and CS are co-spatial is consistent with observed linewidths only within $r \lesssim 100$~au, within which \vturb{} was found to drop from \vel{100} ($\approx~0.4~c_s$) to nothing at 100~au. The parametric model yielded a near constant \vel{50} for CS ($0.2 - 0.4~c_s$). We demonstrate that absolute flux calibration is and will be the limiting factor in all studies of turbulence using a single molecule. The magnitude of the dispersion is comparable with or below that predicted by the magneto-rotational instability theory. A more precise comparison would require to reach an absolute calibration precision of order 3\%, or to find a suitable combination of light and heavy molecules which are co-located in the disk.
dc.language.isoen
dc.publisherEDP Sciences
dc.subject.enAstrophysics - Solar and Stellar Astrophysics
dc.subject.enAstrophysics - Astrophysics of Galaxies
dc.title.enMeasuring Turbulence in TW Hya with ALMA: Methods and Limitations
dc.typeArticle de revue
dc.identifier.doi10.1051/0004-6361/201628550
dc.subject.halPlanète et Univers [physics]/Astrophysique [astro-ph]/Cosmologie et astrophysique extra-galactique [astro-ph.CO]
dc.identifier.arxiv1606.00005
bordeaux.journalAstronomy and Astrophysics - A&A
bordeaux.pageid.A49
bordeaux.volume592
bordeaux.peerReviewedoui
hal.identifierhal-01325420
hal.version1
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-01325420v1
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