Protostars and Planets VI, Heidelberg, July 15-20, 2013

Poster 1B045

Dissecting disks around B-type protostars

Sanchez-Monge, Alvaro (Osservatorio Astrofisico di Arcetri - INAF; Italy)
Cesaroni, Riccardo (Osservatorio Astrofisico di Arcetri - INAF; Italy)
Beltran, Maite (Osservatorio Astrofisico di Arcetri - INAF; Italy)
Kumar, M. S. Nanda (Centro de Astrofisica da Universidade do Porto; Portugal)
Stanke, Thomas (ESO; Germany)
Zinnecker, Hans (SOFIA Science Center; USA)
Etoka, Sandra (Jodrell Bank Center for Astrophysics; UK)
Galli, Daniele (Osservatorio Astrofisico di Arcetri - INAF; Italy)
Hummel, Christian A. (ESO; Germany)
Moscadelli, Luca (Osservatorio Astrofisico di Arcetri - INAF; Italy)
Preibisch, Thomas (Universitats-Sternarte Munchen; Germany)
Ratzka, Thorsten (Universitats-Sternwarte Munchen; Germany)
van der Tak, Floris F. S. (SRON Netherlands Institute for Space Research; The Netherlands)
Vig, Sarita (Indian Institute of Space Science and Technology; India)
Walmsley, C. Malcolm (Osservatorio Astrofisico di Arcetri - INAF; Italy)
Wang, Kuo-Song (Leiden Observatory; The Netherlands)

Recent theoretical models indicate that OB-type stars could form through disk-mediated accretion, like their low mass counterparts. However, on the observational side, circumstellar disks appear still elusive, especially around the most massive (proto)stars. As for early B-type (proto)stars, an ever growing number of disk candidates has been proposed, but only very few of these present evidence for Keplerian rotation. The advent of ALMA provides us with the necessary sensitivity and angular resolution to assess the existence of such disks and possibly establish their rotation curves. With this in mind, we have performed ALMA observations with the highest possible resolution (~0.4\") at 350 GHz to search for circumstellar disks in a couple of presumably massive young stellar objects with luminosities of ~10000 Lsun and associated with bipolar nebulosities suggestive of the presence of disk/outflow systems. By observing simultaneously core and jet tracers, we could reveal molecular cores with velocity gradients perpendicular to the corresponding jets. In at least one case (G35.20-0.74 N), the core structure appears resolved and the velocity field can be fitted with an almost edge-on Keplerian disk rotating about a central mass of 18 Msun. This finding is consistent with the results of a recent study of the CO first overtone bandhead emission at 2.3mum towards G35.20-0.74 N. The disk radius and mass are >2500 au and 3 Msun. To reconcile the observed bolometric luminosity (3x10^4 Lsun) with the estimated stellar mass of 18 Msun, we propose that the latter is the total mass of a binary system.

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