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The search for high-mass protostars with ALMA revealed up to kilo-parsec scales (SPARKS): I. Indication for a centrifugal barrier in the environment of a single high-mass envelope

Authors :
Csengeri, T.
Bontemps, S.
Wyrowski, F.
Belloche, A.
Menten, K. M.
Leurini, S.
Beuther, H.
Bronfman, L.
Commerccon, B.
Chapillon, E.
Longmore, S.
Palau, A.
Tan, J. C.
Urquhart, J. S.
Source :
A&A 617, A89 (2018)
Publication Year :
2018

Abstract

The formation of the most massive O-type stars is poorly understood. We present a case study of a young massive clump from the ATLASGAL survey, G328.2551-0.5321. It exhibits a bolometric luminosity of 1.3$\times$10$^4$ L$_{\odot}$ corresponding to a current protostellar mass of $\sim$11 and 16 M$_{\odot}$. We analyze high angular-resolution observations with ALMA at $\sim$0.17" corresponding a physical scale of $\sim$400 au in dust continuum and molecular lines. The dust continuum emission reveals a single high-mass protostellar envelope and shows evidence for a marginally resolved continuum source. We detect a rotational line of CH$_3$OH within its $v_{\rm t}$=1 torsionally excited state revealing two bright peaks of emission spatially offset from the dust continuum peak, and exhibiting a distinct velocity component $\pm$4.5 km s$^{-1}$ offset compared to the source $v_{\rm lsr}$. Local thermodynamic equilibrium analysis suggests N(CH$_3$OH)=1.2$-$2$\times$10$^{19}$ cm$^{-2}$, and kinetic temperatures of 160$-$200 K at the position of these peaks. Their velocity shifts correspond well to the expected Keplerian velocity around a central object with 15M$_{\odot}$ consistent with the mass estimate based on the source's bolometric luminosity. We propose a picture where the CH$_3$OH emission peaks trace the accretion shocks around the centrifugal barrier, pinpointing the interaction region between the collapsing envelope and an accretion disk. Because the HC$_3$N $v_{\rm 7}$=1e ($J$=38-37) line shows compact emission, and a velocity pattern consistent with models of Keplerian rotation, we suggest that this could be a new tracer for compact accretion disks around high-mass protostars. The estimated physical properties of the accretion disk suggest a specific angular momentum several times larger than typically observed towards low-mass protostars.<br />Comment: Manuscript submitted to A&A, and revised after first referee report (abstract abbreviated)

Details

Database :
arXiv
Journal :
A&A 617, A89 (2018)
Publication Type :
Report
Accession number :
edsarx.1804.06482
Document Type :
Working Paper
Full Text :
https://doi.org/10.1051/0004-6361/201832753