University of Cambridge > Talks.cam > Cavendish Astrophysics Seminars > The early stages of low-mass star formation: subsonic turbulence, isothermal filaments and a First Hydrostatic Core Candidate

The early stages of low-mass star formation: subsonic turbulence, isothermal filaments and a First Hydrostatic Core Candidate

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Low-mass stars are formed in Dense Cores, via gravitational collapse. However, the formation process of Dense Cores is not clear. I will present single dish observations in a dense gas tracer (NH3 using the GBT ) of four regions in the nearby Perseus Molecular Cloud. These data show, for the first time in a single tracer, the transition between the subsonic dense core and the dense but more turbulent gas surrounding it. This transition is sharp and unresolved, very similar to a shock. It is possible that these subsonic structures are needed stage for the star-formation process to take place (at least in low-mass). I will also present NH3 EVLA +GBT observations of the Barnard 5 region with a 6” beam. The observations reveal, for the first time, the presence of striking filamentary structure (20” wide of 5,000 AU at the distance of Perseus) in this low-mass star-forming region. The integrated intensity profile of this structure is consistent with models of an isothermal filament in hydrostatic equilibrium. Also, the observed separation between the B5-IRS1 young stellar object (YSO), in the central region of the core, and the northern starless condensation matches the Jeans length of the dense gas. This suggests that the dense gas in the coherent region is fragmenting. The region observed displays a narrow velocity dispersion, where most of the gas shows evidence for subsonic turbulence, and where little spatial variations are present. It is only close to the YSO where an increase in the velocity dispersion is found, but still displaying subsonic non-thermal motions. Finally, if there is enough time, I will briefly present interferometric follow-up results in one of the regions studied with the GBT . I will present the evidence for a central source, a slow-velocity outflow, and the modelling efforts that suggests the presence of a First Hydrostatic Core candidate.

This talk is part of the Cavendish Astrophysics Seminars series.

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