Fragmentation and kinematics of dense molecular cores in the filamentary infrared-dark cloud G011.11–0.12

Ragan, S. E.; Henning, Thomas; Beuther, H.; Linz, H.; Zahorecz, Sarolta

doi:10.1051/0004-6361/201424948

Cited by 26 publications

(22 citation statements)

References 69 publications

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“…Nevertheless, we also fit the spectra taking into account the full hyperfine structure of the line (see below). Independent of this fit, the integrated emission images already show that this high-mass starless clump is far from being a kinematically homogeneous and potentially calm structure, but in contrast, we see a kinematically complex region that may be at the verge of collapse (see also Ragan et al 2015).…”

Section: Spectral Line Emissionmentioning

confidence: 69%

Hierarchical fragmentation and collapse signatures in a high-mass starless region

Beuther

Henning

Linz

et al. 2015

A&A

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Aims. We study the fragmentation and collapse properties of the dense gas during the onset of high-mass star formation. Methods. We observed the massive (∼800 M ) starless gas clump IRDC 18310-4 with the Plateau de Bure Interferometer (PdBI) at subarcsecond resolution in the 1.07 mm continuum and N 2 H + (3-2) line emission. Results. Zooming from a single-dish low-resolution map to previous 3 mm PdBI data, and now the new 1.07 mm continuum observations, the substructures hierarchically fragment on the increasingly smaller spatial scales. While the fragment separations may still be roughly consistent with pure thermal Jeans fragmentation, the derived core masses are almost two orders of magnitude larger than the typical Jeans mass at the given densities and temperatures. However, the data can be reconciled with models using non-homogeneous initial density structures, turbulence, and/or magnetic fields. While most subcores remain (far-)infrared dark even at 70 μm, we identify weak 70 μm emission toward one core with a comparably low luminosity of ∼16 L , supporting the notion of the general youth of the region. The spectral line data always exhibit multiple spectral components toward each core with comparably small line widths for the individual components (in the 0.3 to 1.0 km s −1 regime). Based on single-dish C 18 O(2-1) data we estimate a low virial-to-gas-mass ratio ≤0.25. We propose that the likely origin of these spectral properties may be the global collapse of the original gas clump that results in multiple spectral components along each line of sight. Even within this dynamic picture the individual collapsing gas cores appear to have very low levels of internal turbulence.

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Section: Spectral Line Emissionmentioning

confidence: 69%

Hierarchical fragmentation and collapse signatures in a high-mass starless region

Beuther

Henning

Linz

et al. 2015

A&A

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“…There are several examples in the literature of filamentary molecular clouds that exhibit a quasi-regular spacing of "cores" (e.g. Jackson et al 2010;Miettinen et al 2012;Busquet et al 2013;Takahashi et al 2013;Lu et al 2014;Wang et al 2014;Beuther et al 2015b;Ragan et al 2015;Contreras et al 2016;Teixeira et al 2016). This regularity is often discussed in the context of predictions from theoretical work describing the fragmentation of fluid cylinders due to gravitational or magnetohydrodynamic-driven instabilities (e.g.…”

Section: Investigating the Fragmentation Of A Filamentmentioning

confidence: 99%

Investigating the structure and fragmentation of a highly filamentary IRDC

Henshaw¹,

Caselli

Fontani³

et al. 2016

Mon. Not. R. Astron. Soc.

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We present 3.7 arcsec (∼ 0.05 pc) resolution 3.2 mm dust continuum observations from the Institut de Radioastronomie Millimétrique Plateau de Bure Interferometer, with the aim of studying the structure and fragmentation of the filamentary infrared dark cloud (IRDC) G035.39 − 00.33. The continuum emission is segmented into a series of 13 quasi-regularly spaced (λ obs ∼ 0.18 pc) cores, following the major axis of the IRDC. We compare the spatial distribution of the cores with that predicted by theoretical work describing the fragmentation of hydrodynamic fluid cylinders, finding a significant (factor of 8) discrepancy between the two. Our observations are consistent with the picture emerging from kinematic studies of molecular clouds suggesting that the cores are harboured within a complex network of independent sub-filaments. This result emphasizes the importance of considering the underlying physical structure, and potentially, dynamically important magnetic fields, in any fragmentation analysis. The identified cores exhibit a range in (peak) beam-averaged column density (3.6 × 10 23 cm −2 < N H,c < 8.0 ×10 23 cm −2 ), mass (8.1 M < M c < 26.1 M ), and number density (6.1 × 10 5 cm −3 < n H,c,eq < 14.7 × 10 5 cm −3 ). Two of these cores, dark in the mid-infrared, centrally-concentrated, monolithic (with no traceable substructure at our PdBI resolution), and with estimated masses of the order ∼ 20 − 25 M , are good candidates for the progenitors of intermediate-to-high-mass stars. Virial parameters span a range 0.2 < α vir < 1.3. Without additional support, possibly from dynamically important magnetic fields with strengths of the order of 230 µG < B < 670 µG, the cores are susceptible to gravitational collapse. These results may imply a multilayered fragmentation process, which incorporates the formation of sub-filaments, embedded cores, and the possibility of further fragmentation.

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“…For example, Csengeri et al (2011) Cygnus X, D = 1.7 kpc see infall |ur| = 0.1 − 0.6 km s −1 , σT ∼ 0.6 − 2 km s −1 at r ≈ 0.1 pc, n ∼ 10 5 − 10 6 . Other examples include Ragan et al (2012Ragan et al ( , 2015 and Peretto et al (2013).…”

Section: Comparisons To Observationsmentioning

confidence: 99%

Collapse in self-gravitating turbulent fluids

Murray¹,

Chang²,

Murray³

et al. 2016

Mon. Not. R. Astron. Soc.

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Motivated by the nonlinear star formation efficiency found in recent numerical simulations by a number of workers, we perform high-resolution adaptive mesh refinement simulations of star formation in self-gravitating turbulently driven gas. As we follow the collapse of this gas, we find that the character of the flow changes at two radii, the disk radius r d , and the radius r * where the enclosed gas mass exceeds the stellar mass. Accretion starts at large scales and works inwards. In line with recent analytical work, we find that the density evolves to a fixed attractor, ρ(r, t) → ρ(r), for r d < r < r * ; mass flows through this structure onto a sporadically gravitationally unstable disk, and from thence onto the star. In the bulk of the simulation box we find that the random motions v T ∼ r p with p ∼ 0.5, in agreement with Larson's sizelinewidth relation. In the vicinity of massive star forming regions we find p ∼ 0.2 − 0.3, as seen in observations. For r < r * , v T increases inward, with p = −1/2. Finally, we find that the total stellar mass M * (t) ∼ t 2 in line with previous numerical and analytic work that suggests a nonlinear rate of star formation.

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Fragmentation and kinematics of dense molecular cores in the filamentary infrared-dark cloud G011.11–0.12

Cited by 26 publications

References 69 publications

Hierarchical fragmentation and collapse signatures in a high-mass starless region

Hierarchical fragmentation and collapse signatures in a high-mass starless region

Investigating the structure and fragmentation of a highly filamentary IRDC

Collapse in self-gravitating turbulent fluids

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