Universität zu Köln

Maud, L. T., Cesaroni, R., Kumar, M. S. N., van der Tak, F. F. S., Allen, V., Hoare, M. G., Klaassen, P. D., Harsono, D., Hogerheijde, M. R., Sanchez-Monge, A., Schilke, P., Ahmadi, A., Beltran, M. T., Beuther, H., Csengeri, T., Etoka, S., Fuller, G., Galvan-Madrid, R., Goddi, C., Henning, Th., Johnston, K. G., Kuiper, R., Lumsden, S., Moscadelli, L., Mottram, J. C., Peters, T., Rivilla, V. M., Testi, L., Vig, S., de Wit, W. J. and Zinnecker, H. (2018). Chasing discs around O-type (proto)stars. Astron. Astrophys., 620. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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Abstract

We present high angular resolution (similar to 0.2 '') continuum and molecular emission line Atacama Large Millimeter/sub-millimeter Array (ALMA) observations of G17.64+0.16 in Band 6 (220-230 GHz) taken as part of a campaign in search of circumstellar discs around (proto)-O-stars. At a resolution of similar to 400 au the main continuum core is essentially unresolved and isolated from other strong and compact emission peaks. We detect SiO (5-4) emission that is marginally resolved and elongated in a direction perpendicular to the large-scale outflow seen in the (CO)-C-13 (2-1) line using the main ALMA array in conjunction with the Atacama Compact Array (ACA). Morphologically, the SiO appears to represent a disc-like structure. Using parametric models we show that the position-velocity profile of the SiO is consistent with the Keplerian rotation of a disc around an object between 10 and 30M(circle dot) in mass, only if there is also radial expansion from a separate structure. The radial motion component can be interpreted as a disc wind from the disc surface. Models with a central stellar object mass between 20 and 30 M-circle dot are the most consistent with the stellar luminosity (1 x 10(5) L-circle dot) and indicative of an O-type star. The H30 alpha millimetre recombination line (231.9 GHz) is also detected, but spatially unresolved, and is indicative of a very compact, hot, ionised region co-spatial with the dust continuum core. The broad line-width of the H30 alpha emission (full-width-half-maximum = 81.9 km s(-1)) is not dominated by pressure-broadening but is consistent with underlying bulk motions. These velocities match those required for shocks to release silicon from dust grains into the gas phase. CH3CN and CH3OH thermal emission also shows two arc shaped plumes that curve away from the disc plane. Their coincidence with OH maser emission suggests that they could trace the inner working surfaces of a wide-angle wind driven by G17.64 which impacts the diffuse remnant natal cloud before being redirected into the large-scale outflow direction. Accounting for all observables, we suggest that G17.64 is consistent with a O-type young stellar object in the final stages of protostellar assembly, driving a wind, but that has not yet developed into a compact HII region. The existance and detection of the disc in G17.64 is likely related to its isolated and possibly more evolved nature, traits which may underpin discs in similar sources.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Maud, L. T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Cesaroni, R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kumar, M. S. N. UNSPECIFIED UNSPECIFIED UNSPECIFIED van der Tak, F. F. S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Allen, V. UNSPECIFIED UNSPECIFIED UNSPECIFIED Hoare, M. G. UNSPECIFIED UNSPECIFIED UNSPECIFIED Klaassen, P. D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Harsono, D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Hogerheijde, M. R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Sanchez-Monge, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schilke, P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Ahmadi, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Beltran, M. T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Beuther, H. UNSPECIFIED UNSPECIFIED UNSPECIFIED Csengeri, T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Etoka, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Fuller, G. UNSPECIFIED UNSPECIFIED UNSPECIFIED Galvan-Madrid, R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Goddi, C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Henning, Th. UNSPECIFIED UNSPECIFIED UNSPECIFIED Johnston, K. G. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kuiper, R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Lumsden, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Moscadelli, L. UNSPECIFIED UNSPECIFIED UNSPECIFIED Mottram, J. C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Peters, T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Rivilla, V. M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Testi, L. UNSPECIFIED UNSPECIFIED UNSPECIFIED Vig, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED de Wit, W. J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Zinnecker, H. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-165426
DOI:	10.1051/0004-6361/201833908
Journal or Publication Title:	Astron. Astrophys.
Volume:	620
Date:	2018
Publisher:	EDP SCIENCES S A
Place of Publication:	LES ULIS CEDEX A
ISSN:	1432-0746
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language SUBMILLIMETER ARRAY OBSERVATIONS; INFRARED REFLECTION NEBULA; DISTANCE-LIMITED SAMPLE; MASSIVE STAR-FORMATION; LINE-DRIVEN ABLATION; IMAGING POLARIMETRY; CIRCUMSTELLAR DISCS; RADIATION PRESSURE; EARLY EVOLUTION; RADIO-EMISSION Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/16542