Filamentary structure and Keplerian rotation in the high-mass star-forming region G35.03+0.35 imaged with ALMA^⋆

¹ INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
² I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
³ Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
⁴ Dublin Institute for Advanced Studies (DIAS), 31 Fitzwilliam Place, 2 Dublin, Ireland
⁵ Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK
⁶ Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
⁷ The University of Tokushima, Minami Jousanjima-machi 1-1, Tokushima, 770-8502 Tokushima, Japan
⁸ ESO, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
⁹ SRON Netherlands Institute for Space Research, PO Box 800, 9700 AV Groningen, The Netherlands
¹⁰ Kapteyn Astronomical Institute, University of Groningen, 9700 AV Groningen, The Netherlands
¹¹ Dept. of Earth and Space Science, Indian Institute of Space Science and Technology, Thiruvananthapuram, 695 547 Kerala, India
¹² Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
¹³ Academia Sinica, Institute of Astronomy and Astrophysics, PO Box 23-141, Taipei 10617, Taiwan, PR China
¹⁴ SOFIA Science Center, NASA Ames Research Center, Mailstop 232-12, Moffett Field, CA 94035, USA
¹⁵ Istituto di Astrofisica e Planetologia Spaziali − INAF, via Fosso del Cavaliere 100, 00133 Roma, Italy
¹⁶ Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125, USA

Received: 18 April 2014
Accepted: 24 July 2014

Abstract

Context. Theoretical scenarios propose that high-mass stars are formed by disk-mediated accretion.

Aims. To test the theoretical predictions on the formation of massive stars, we wish to make a thorough study at high-angular resolution of the structure and kinematics of the dust and gas emission toward the high-mass star-forming region G35.03+0.35, which harbors a disk candidate around a B-type (proto)star.

Methods. We carried out ALMA Cycle 0 observations at 870 μm of dust of typical high-density, molecular outflow, and cloud tracers with resolutions of < 0''̣5. Complementary Subaru COMICS 25 μm observations were carried out to trace the mid-infrared emission toward this star-forming region.

Results. The submillimeter continuum emission has revealed a filamentary structure fragmented into six cores, called A–F. The filament could be in quasi-equilibrium taking into account that the mass per unit length of the filament, 200–375 M_⊙/pc, is similar to the critical mass of a thermally and turbulently supported infinite cylinder, ~335 M_⊙/pc. The cores, which are on average separated by ~0.02 pc, have deconvolved sizes of 1300–3400 AU, temperatures of 35–240 K, H₂ densities >10⁷ cm ^-3, and masses in the range 1–5 M_⊙, and they are subcritical. Core A, which is associated with a hypercompact Hii region and could be the driving source of the molecular outflow observed in the region, is the most chemically rich source in G35.03+0.35 with strong emission of typical hot core tracers such as CH₃CN. Tracers of high density and excitation show a clear velocity gradient along the major axis of the core, which is consistent with a disk rotating about the axis of the associated outflow. The PV plots along the SE–NW direction of the velocity gradient show clear signatures of Keplerian rotation, although infall could also be present, and they are consistent with the pattern of an edge-on Keplerian disk rotating about a star with a mass in the range 5–13 M_⊙. The high t_ff/t_rot ratio for core A suggests that the structure rotates fast and that the accreting material has time to settle into a centrifugally supported disk.

Conclusions. G35.03+0.35 is one of the most convincing examples of Keplerian disks rotating about high-mass (proto)stars. This supports theoretical scenarios according to which high-mass stars, at least B-type stars, would form through disk-mediated accretion.