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dc.contributor.authorHein Bertelsen, R. P.
dc.contributor.authorKamp, I.
dc.contributor.authorvan der Plas, G.
dc.contributor.authorvan den Ancker, M. E.
dc.contributor.authorWaters, L. B. F. M.
dc.contributor.authorThi, W.-F.
dc.contributor.authorWoitke, P.
dc.identifier.citationHein Bertelsen , R P , Kamp , I , van der Plas , G , van den Ancker , M E , Waters , L B F M , Thi , W-F & Woitke , P 2016 , ' A proposed new diagnostic for Herbig disc geometry : FWHM versus J of CO ro-vibrational lines ' , Astronomy & Astrophysics , vol. 590 , A98 , pp. 1-26 .
dc.identifier.otherRIS: 10.105100046361201527652
dc.descriptionI.K.,W.F.T., and P.W. acknowledge funding from the EU FP7-2011 under Grant Agreement No. 284405. G.v.d.p. acknowledges support from the Millennium Science Initiative (Chilean Ministry of Economy) through grant Nucleus P10-022-F and also acknowledges financial support provided by FONDECYT following grant 3140393.en
dc.description.abstractAims. The CO ro-vibrational lines observed from Herbig group II discs are often seen to be broad, while the same lines observed from group I discs are often narrow. This difference is not well understood. In this paper we explore the underlying cause for this difference and provide a pathway for a better understanding of the geometry and structure of the inner discs around Herbig Ae/Be stars. Methods. High spectral resolution infrared spectra of CO ro-vibrational emission from six Herbig Ae/Be candidate stars were taken with the CRyogenic high-resolution InfraRed Echelle Spectrograph (CRIRES) at the Very Large Telescope (VLT). From these spectra, we produce individual and co-added CO ro-vibrational line profiles. We investigate line profile shape differences, and we explore the full width at half maximum (FWHM) variations with J quantum number in the context of disc geometry. Furthermore, we put our new sources into the context of earlier observed sources to study a large sample. For comparison, we also investigate the FWHM variations with J of modelled CO ro-vibrational lines from two typical disc geometries produced with the thermochemical disc modelling code ProDiMo. Results. For our new observations of CO ro-vibrational lines, we find that the FWHM of individual lines are in the range of 10–60 km s-1. We find both narrow and broad single-peaked emission lines, but only Hen 2-80 displays double-peaked emission lines. For HD 250550, the FWHM of the CO lines increases with J value, indicating a radially extended emitting region, while Hen 2-80 shows a constant FWHM versus J behaviour, indicating a narrow emitting region. This qualitatively agrees with the two different modelled disc geometries. Comparing dust and gas inner disc geometries (inferred by the spectral energy distribution (SED) and CO ro-vibrational emission) for the expanded sample of observed Herbig discs, we find no clear correspondence between the SED (spectral energy distribution) groups of the sources and their inner CO radius. Conclusions. The FWHM versus J is a potential new gas diagnostic for the inner disc with, for example, a constant FWHM versus J indicating the presence of a large gas hole or gap. Models and observations both indicate the potential of this new diagnostic. Our extended sample does not fully support the previous trend where group I discs have CO ro-vibrational emission lines with small FWHM. Instead, our CO ro-vibrational data from a handful of sources indicates different inner disc geometries for the gas and dust of these sources.
dc.relation.ispartofAstronomy & Astrophysicsen
dc.subjectInfrared: starsen
dc.subjectLine: profilesen
dc.subjectCircumstellar matteren
dc.subjectProtoplanetary disksen
dc.subjectStars: pre-main sequenceen
dc.subjectQB Astronomyen
dc.subjectQC Physicsen
dc.titleA proposed new diagnostic for Herbig disc geometry : FWHM versus J of CO ro-vibrational linesen
dc.typeJournal articleen
dc.contributor.sponsorEuropean Commissionen
dc.contributor.institutionUniversity of St Andrews. School of Physics and Astronomyen
dc.description.statusPeer revieweden

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