The Initial Conditions for Gravitational Collapse of a Core: An Extremely Young Low-Mass Class 0 Protostar GF9-2

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dc.creatorFuruya, Ray S.
dc.creatorKitamura, Yoshimi
dc.creatorShinnaga, Hiroko
dc.date2006-08-16
dc.date.accessioned2026-07-07T10:39:47Z
dc.date.available2026-07-07T10:39:47Z
dc.descriptionWe present a study of the natal core harboring the class 0 protostar GF9-2 in the filamentary dark cloud GF 9 (d = 200 pc). GF9-2 stands unique in the sense that it shows H2O maser emission, a clear signpost of protostar formation, whereas it does not have a high-velocity large-scale molecular outflow evidenced by our deep search for CO wing emission. These facts indicate that GF9-2 core is early enough after star formation so that it still retains some information of initial conditions for collapse. Our 350 um dust continuum emission image revealed the presence of a protostellar envelope in the center of a molecular core. The mass of the envelope is ~0.6 Msun from the 350 um flux density, while LTE mass of the core is ~3 Msun from moleuclar line observations. Combining visibility data from the OVRO mm-array and the 45m telescope, we found that the core has a radial density profile of $ρ(r)\propto r^{-2}$ for 0.003 < r/pc < 0.08 region. Molecular line data analysis revealed that the velocity width of the core gas increases inward,while the outermost region maintains a velocity dispersion of a few times of the ambient sound speed. The broadened velocity width can be interpreted as infall. Thus, the collapse in GF9-2 is likely to be described by an extension of the Larson-Penston solution for the period after formation of a central star. We derived the current mass accretion rate of ~3E-05 Msun/year from infall velocity of ~ 0.3 km/s at r~ 7000 AU. All results suggest that GF9-2 core has been undergoing gravitational collapse for ~ 5000 years since the formation of central protostar(s), and that the unstable state initiated the collapse ~2E+05 years (the free-fall time) ago.
dc.descriptionApJ Accepted. The preprint including figures with the original quality is available at http://subarutelescope.org/staff/rsf/publication.html
dc.identifierhttps://arxiv.org/abs/astro-ph/0608357
dc.identifierhttp://arxiv.org/abs/astro-ph/0608357
dc.identifierAstrophys.J.653:1369-1390,2006
dc.identifierdoi:10.1086/508405
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/181152
dc.subjectAstrophysics
dc.titleThe Initial Conditions for Gravitational Collapse of a Core: An Extremely Young Low-Mass Class 0 Protostar GF9-2
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