Chains of dense cores in the Taurus L1495/B213 complex

Tafalla, M.; Hacar, A.

doi:10.1051/0004-6361/201424576

Cited by 147 publications

(203 citation statements)

References 90 publications

(198 reference statements)

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“…Hierarchical fragmentation was found by Hacar et al (2013) and Tafalla & Hacar (2015) in the nearby L1495/B2013 complex. The fray and fragment filament evolution scenario proposed by these authors is the following: The filamentary cloud first fragments into intertwined, velocity-coherent filaments, socalled fibers.…”

Section: Fray and Fragment?mentioning

confidence: 96%

Structure and stability in TMC-1: Analysis of NH₃molecular line andHerschelcontinuum data

Fehér

Tóth

Ward-Thompson

et al. 2016

A&A

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Aims. We examined the velocity, density, and temperature structure of Taurus molecular cloud-1 (TMC-1), a filamentary cloud in a nearby quiescent star forming area, to understand its morphology and evolution. Methods. We observed high signal-to-noise (S/N), high velocity resolution NH 3 (1,1), and (2, 2) emission on an extended map. By fitting multiple hyperfine-split line profiles to the NH 3 (1, 1) spectra, we derived the velocity distribution of the line components and calculated gas parameters on several positions. Herschel SPIRE far-infrared continuum observations were reduced and used to calculate the physical parameters of the Planck Galactic Cold Clumps (PGCCs) in the region, including the two in TMC-1. The morphology of TMC-1 was investigated with several types of clustering methods in the parameter space consisting of position, velocity, and column density. Results. Our Herschel-based column density map shows a main ridge with two local maxima and a separated peak to the south-west. The H 2 column densities and dust colour temperatures are in the range of 0.5−3.3 × 10 22 cm −2 and 10.5−12 K, respectively. The NH 3 column densities and H 2 volume densities are in the range of 2.8−14.2 × 10 14 cm −2 and 0.4−2.8 × 10 4 cm −3 . Kinetic temperatures are typically very low with a minimum of 9 K at the maximum NH 3 and H 2 column density region. The kinetic temperature maximum was found at the protostar IRAS 04381+2540 with a value of 13.7 K. The kinetic temperatures vary similarly to the colour temperatures in spite of the fact that densities are lower than the critical density for coupling between the gas and dust phase. The k-means clustering method separated four sub-filaments in TMC-1 with masses of 32.5, 19.6, 28.9, and 45.9 M and low turbulent velocity dispersion in the range of 0.13−0.2 km s −1 . Conclusions. The main ridge of TMC-1 is composed of four sub-filaments that are close to gravitational equilibrium. We label these TMC-1F1 through F4. The sub-filaments TMC-1F1, TMC-1F2, and TMC-1F4 are very elongated, dense, and cold. TMC-1F3 is a little less elongated and somewhat warmer, and probably heated by the Class I protostar, IRAS 04381+2540, which is embedded in it. TMC-1F3 is approximately 0.1 pc behind TMC1-F1. Because of its structure, TMC-1 is a good target to test filament evolution scenarios.

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Section: Fray and Fragment?mentioning

confidence: 96%

Structure and stability in TMC-1: Analysis of NH₃molecular line andHerschelcontinuum data

Fehér

Tóth

Ward-Thompson

et al. 2016

A&A

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“…They identified shorter 0.5 pc coherent non-interacting sub-filaments which have velocity separations of 0.5-1.0 km/s similar to what we observe. Tafalla & Hacar (2015) proposed a 'fray and fragment' model to explain the multiple structures. This model starts with a wide filament that fragments into sub-filaments, which then further fragment into cores.…”

Section: Multiple Structuresmentioning

confidence: 99%

Morphology and Kinematics of Filaments in the Serpens and Perseus Molecular Clouds

Dhabal

Mundy

Rizzo

et al. 2018

ApJ

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We present H 13 CO + (J=1-0) and HNC (J=1-0) maps of regions in Serpens South, Serpens Main and NGC 1333 containing filaments. We also observe the Serpens regions using H 13 CN (J=1-0). These dense gas tracer molecular line observations carried out with CARMA have an angular resolution of ∼ 7 , a spectral resolution of ∼ 0.16 km/s and a sensitivity of 50-100 mJy/beam. Although the large scale structure compares well with the Herschel dust continuum maps, we resolve finer structure within the filaments identified by Herschel. The H 13 CO + emission distribution agrees with the existing CARMA N 2 H + (J=1-0) maps; so they trace the same morphology and kinematics of the filaments. The H 13 CO + maps additionally reveal that many regions have multiple structures partially overlapping in the line-of-sight. In two regions, the velocity differences are as high as 1.4 km/s. We identify 8 filamentary structures having typical widths of 0.03 − 0.08 pc in these tracers. At least 50% of the filamentary structures have distinct velocity gradients perpendicular to their major axis with average values in the range 4 − 10 km s −1 pc −1 . These findings are in support of the theoretical models of filament formation by 2-D inflow in the shock layer created by colliding turbulent cells. We also find evidence of velocity gradients along the length of two filamentary structures; the gradients suggest that these filaments are inflowing towards the cloud core.

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“…Orders of magnitude lower in density, its interaction with the denser fiber-like structures should be negligible. However, some of these fibers could still gain mass while moving through (and sweeping up) this medium (Tafalla & Hacar 2015).…”

Section: Filling Factor and Inter-fiber Mediummentioning

confidence: 99%

Opacity broadening and interpretation of suprathermal CO linewidths: Macroscopic turbulence and tangled molecular clouds

Hacar

Alves

Burkert

et al. 2016

A&A

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Context. Since their first detection in the interestellar medium, (sub-)millimeter line observations of different CO isotopic variants have routinely been employed to characterize the kinematic properties of the gas in molecular clouds. Many of these lines exhibit broad linewidths that greatly exceed the thermal broadening expected for the low temperatures found within these objects. These observed suprathermal CO linewidths are assumed to originate from unresolved supersonic motions inside clouds. Aims. The lowest rotational J transitions of some of the most abundant CO isotopologues, 12 CO and 13 CO, are found to present large optical depths. In addition to well-known line saturation effects, these large opacities present a non-negligible contribution to their observed linewidths. Typically overlooked in the literature, in this paper we aim to quantify the impact of these opacity broadening effects on the current interpretation of the CO suprathermal line profiles. Methods. Combining large-scale observations and LTE modeling of the ground J = 1−0 transitions of the main 12 CO, 13 CO, C 18 O isotopologues, we have investigated the correlation of the observed linewidths as a function of the line opacity in different regions of the Taurus molecular cloud. Results. Without any additional contributions to the gas velocity field, a large fraction of the apparently supersonic (M ∼ 2-3) linewidths measured in both 12 CO and 13 CO (J = 1−0) lines can be explained by the saturation of their corresponding sonic-like, optically thin C 18 O counterparts assuming standard isotopic fractionation. Combined with the presence of multiple components detected in some of our C 18 O spectra, these opacity effects also seem to be responsible for most of the highly supersonic linewidths (M > 8-10) detected in some of the broadest 12 CO and 13 CO spectra in Taurus.Conclusions. Our results demonstrate that most of the suprathermal 12 CO and 13 CO linewidths reported in nearby clouds like Taurus could be primarily created by a combination of opacity broadening effects and multiple gas velocity components blended in these saturated emission lines. Once corrected by their corresponding optical depth, each of these gas components present transonic intrinsic linewidths consistently traced by the three isotopologues, 12 CO, 13 CO, and C 18 O, with differences within a factor of 2. Highly correlated and velocity-coherent at large scales, the largest and highly supersonic velocity differences inside clouds are generated by the relative motions between individual gas components. In contrast to the classical interpretation within the framework of microscopic turbulence, this highly discretized structure of the molecular gas traced in CO suggest that the gas dynamics inside molecular clouds could be better described by the properties of a fully resolved macroscopic turbulence.

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Chains of dense cores in the Taurus L1495/B213 complex

Cited by 147 publications

References 90 publications

Structure and stability in TMC-1: Analysis of NH₃molecular line andHerschelcontinuum data

Structure and stability in TMC-1: Analysis of NH₃molecular line andHerschelcontinuum data

Morphology and Kinematics of Filaments in the Serpens and Perseus Molecular Clouds

Opacity broadening and interpretation of suprathermal CO linewidths: Macroscopic turbulence and tangled molecular clouds

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Chains of dense cores in the Taurus L1495/B213 complex

Cited by 147 publications

References 90 publications

Structure and stability in TMC-1: Analysis of NH3molecular line andHerschelcontinuum data

Structure and stability in TMC-1: Analysis of NH3molecular line andHerschelcontinuum data

Morphology and Kinematics of Filaments in the Serpens and Perseus Molecular Clouds

Opacity broadening and interpretation of suprathermal CO linewidths: Macroscopic turbulence and tangled molecular clouds

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Structure and stability in TMC-1: Analysis of NH₃molecular line andHerschelcontinuum data

Structure and stability in TMC-1: Analysis of NH₃molecular line andHerschelcontinuum data