DIRECT OBSERVATION OF A SHARP TRANSITION TO COHERENCE IN DENSE CORES

By J. Pineda, A. Goodman, H. Arce, P. Caselli, J. Foster, P. Myers, Erik Rosolowsky. 2010

139 citations recorded by the source corpus.

We present NH3 observations of the B5 region in Perseus obtained with the Green Bank Telescope. The map covers a region large enough (∼11′×14′) that it contains the entire dense core observed in previous dust continuum surveys. The dense gas traced by NH3(1,1) covers a much larger area than the dust continuum features found in bolometer observations. The velocity dispersion in the central region of the core is small, presenting subsonic non-thermal motions which are independent of scale. However, it is because of the coverage and high sensitivity of the observations that we present the detection, for the first time, of the transition between the coherent core and the dense but more turbulent gas surrounding it. This transition is sharp, increasing the velocity dispersion by a factor of 2 in less than 0.04 pc (the 31″ beam size at the distance of Perseus, ∼250 pc). The change in velocity dispersion at the transition is ≈3 km s-1 pc−1. The existence of the transition provides a natural definition of dense core: the region with nearly constant subsonic non-thermal velocity dispersion. From the analysis presented here, we can neither confirm nor rule out a corresponding sharp density transition.

Subfields: Astronomy and Astrophysics, Atmospheric Science

View Paper: https://www.semanticscholar.org/paper/f172af5ea46ef0770a64e4b491b3a69b24c689c9

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Atmospheric Science

Citations in the corpus

On the diversity and statistical properties of protostellar discs (2018, background): “…within dense molecular clouds cores is typically subsonic and independent of scale (Goodman et al. 1998; Caselli et al. 2002) and there is observational evidence that dense cores may be kinematically distinct from the large clouds in which they are embedded (Pineda et al. 2010; Hacar et al. 2016).”
Dense core formation by fragmentation of velocity-coherent filaments in L1517 (2011, result): “Our finding of velocity coherence on scales larger than a core would seem to contradict the recent results from Pineda et al. (2010), who claim to have detected of the transition between the coherent and turbulent regimes in a core with observations of the B5 region in Perseus.”
Dense gas in the Galactic central molecular zone is warm and heated by turbulence (2015, background): “Such an effect would require a transition from supersonically turbulent to coherent (subsonically turbulent) gas motion (e.g., Pineda et al. 2010) and could reduce the required column densities by ∼ 100×.”
On the universality of interstellar filaments: theory meets simulations and observations (2015, unknown): “This transition may in fact be the same as what has been termed ‘the transition to coherence’ in observations of dense cores (Goodman et al. 1998; Pineda et al. 2010).”
The big problems in star formation: The star formation rate, stellar clustering, and the initial mass function (2014, background): “The structure of a single core is definitely not hierarchical and scale-free (e.g Barranco & Goodman 1998; Goodman et al. 1998; Pineda et al. 2010), but if one treats the dense cores as point particles like stars and analyzes their positions relative to one another, the result is again 12 a…”
Global hierarchical collapse in molecular clouds. Towards a comprehensive scenario (2019, background): “This decrease is sometimes inferred from radial scans of the line profile moving away from the core’s center, in which a progressive blurring of groups of hyperfine lines is observed towards the outer regions of the core (e.g., Pineda et al. 2010).”
Star Formation in the Milky Way and Nearby Galaxies (2012, methodology): “A recent, careful study of CO and 13CO toward the Taurus molecular cloud shows that N(CO) traces AV up to 10 mag in some regions but only up to 4 mag in other regions, and other issues cause problems below AV = 3 mag (Pineda et al. 2010b).”