2006/08/16 by Ray S. Furuya, Yoshimi Kitamura, Hiroko Shinnaga
Chemistry · Earth and Planetary Sciences · Physics and Astronomy · #Accretion (finance) #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Atmospheric Ozone and Climate #Core (optical fiber) #Galaxy #Gravitational collapse #Maser #Millimeter #Molecular Spectroscopy and Structure #Optics #Outflow #Physics #Protostar #Star formation #Stars #Velocity dispersion #astro-ph
paper · pdf · doi:10.1086/508405
published as Astrophys.J.653:1369-1390,2006 · ApJ Accepted. The preprint including figures with the original quality is available at http://subarutelescope.org/staff/rsf/publication.html
arxiv created 2006/08/16 · openalex publication_date 2006/12/13 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present a study of the natal core harboring the low-mass Class 0 protostar GF 9-2 in the filamentary dark cloud GF 9 using the Nobeyama 45 m and CSO 10.4 m telescopes and the OVRO millimeter array. GF 9-2 is unique in the sense that it shows H 2 O masers, a clear signpost of protostar formation, but does not have a high-velocity large-scale outflow. These facts indicate that the GF 9-2 core is early enough after star formation that it still retains some information of initial conditions for collapse. Our 350 μm dust continuum image identified a protostellar envelope with an extent of ≃5400 AU in the center of the molecular core ≃0.08 pc in size. The envelope mass is estimated to be ≃0.6 M ☉ from the 350 μm flux density, while the LTE mass of the core is ≃3 M ☉ from molecular lines. We found that the core has a radial density profile of ρ( r ) ∝ r -2 for the 0.003 ≲ r /pc ≲ 0.08 region and that the velocity width of the core gas increases inward, while the outermost region maintains a velocity dispersion of a few times the ambient sound speed. If we interpret the broadened velocity width as infall, the core collapse can be well described by an extension of the Larson-Penston solution for the period after formation of a central star. We derived the mass accretion rate of ≃3 × 10 -5 M ☉ yr -1 from infall velocity of ≃0.3 km s -1 at r ≃ 7000 AU. Furthermore, we found evidence that a protobinary is being formed at the core center. All of the results suggest that the GF 9-2 core has been undergoing gravitational collapse for ≲5000 yr since the protostar formation and that the unstable state initiated the collapse ≃2 × 10 5 yr (the free-fall time) ago.