Abstract
We imaged the molecular outflows towards the cluster of high-mass young stellar objects G24.78+0.08 at high-angular resolution using SiO emission, which is considered the classical tracer of protostellar jets. We performed SiO observations with the VLA interferometer in the J = 1-0 v=0 transition and with the SMA array in the 5-4 transition. A complementary IRAM 30-m single-dish survey in the (2-1), (3-2), (5-4), and (6-5) SiO lines was also carried out. Two collimated SiO high-velocity outflows driven by the A2 and C millimeter continuum massive cores have been imaged. On the other hand, we detected no SiO outflow driven by the young stellar objects in more evolved evolutionary phases that are associated with ultracompact (B) or hypercompact (A1) HII regions. The LVG analysis reveals high-density gas (10^3-10^4 cm-3), with well constrained SiO column densities (0.5-1 10^15 cm-2). The driving source of the A2 outflow is associated with typical hot core tracers such as methyl formate, vinyl cyanide, cyanoacetilene, and acetone. The driving source of the main SiO outflow in G24 has an estimated luminosity of a few 10^4 Lsun (typical of a late O-type star) and is embedded in the 1.3 mm continuum core A2, which in turn is located at the centre of a hot core that rotates on a plane perpendicular to the outflow main axis. The present SiO images support a scenario similar to the low-mass case for massive star formation, where jets that are clearly traced by SiO emission, create outflows of swept-up ambient gas usually traced by CO.
Highlights
Two main theoretical scenarios, based on accretion, are proposed to explain the formation of O-B type stars: (i) the core accretion model (McKee & Tan 2002, 2003), where massive stars form from massive cores; and (ii) the competitive accretion model (Bonnell et al 2007), where a molecular cloud fragments into low-mass cores, which form stars that compete to accrete mass from a common gas reservoir
We present Silicon monoxide (SiO)(1–0) and SiO(5–4) images obtained with the NRAO1 Very Large Array (VLA) and SubMillimeter Array (SMA)2 as well as a complementary IRAM3 30-m observations to unveil the mass loss process driven by the G24 cluster of high-mass young stellar objects (YSOs)
We conducted a multiline SiO survey towards the G24.78+0.08 region, which is an excellent laboratory to study the process of high-mass star formation, because it is associated with YSOs in different evolutionary stages
Summary
Two main theoretical scenarios, based on accretion, are proposed to explain the formation of O-B type stars: (i) the core accretion model (McKee & Tan 2002, 2003), where massive stars form from massive cores; and (ii) the competitive accretion model (Bonnell et al 2007), where a molecular cloud fragments into low-mass cores, which form stars that compete to accrete mass from a common gas reservoir Both models predict the existence of accretion disks around massive young stellar objects (YSOs), and the presence of jets driving molecular outflows. The A cores are embedded in huge (0.1 pc), massive (a few 100 M ) toroids, that rotate around the southeast-northwest (SE-NW) direction, and could still host elusive accretion disks in their interior (Beltrán et al 2005) This possibility would be even more intriguing for the object labelled A1, which is unique, because of the simultaneous presence of almost all the “ingredients” expected in a typical star formation “recipe”: a 20 M star surrounded by a hypercompact. We present SiO(1–0) and SiO(5–4) images obtained with the NRAO1 Very Large Array (VLA) and SubMillimeter Array (SMA) as well as a complementary IRAM3 30-m observations to unveil the mass loss process driven by the G24 cluster of high-mass YSOs
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
