Determining structure in molecular clouds

Williams, Jonathan P.; Geus, E. J. de; Blitz, Leo

doi:10.1086/174279

Cited by 907 publications

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“…1 http://www.atnf.csiro.au/computing/software/ They extracted these clumps from NGC 6334 and the "interregion filament" using the Clumpfind algorithm (Williams et al 1994). Clumpfind defines a source as an emission peak that extends to a defined contour level (in Muñoz et al 2007, 3σ = 75 mJy beam −1 ) and separates it from other peaks/sources at saddle points located below a given level (here again 3σ) from the peaks.…”

Section: Analysis and Resultsmentioning

confidence: 99%

The earliest phases of high-mass star formation: the NGC 6334-NGC 6357 complex

Russeil¹,

Zavagno²,

Motte

et al. 2010

A&A

135

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Context. Our knowledge of high-mass star formation has been mainly based on follow-up studies of bright sources found by IRAS, and has thus been incomplete for its earliest phases, which are inconspicuous at infrared wavelengths. With a new generation of powerful bolometer arrays, unbiased large-scale surveys of nearby high-mass star-forming complexes now search for the high-mass analog of low-mass cores and class 0 protostars. Aims. Following the pioneering study of Cygnus X, we investigate the star-forming region NGC 6334-NGC 6357 (∼1.7 kpc). Methods. We study the complex NGC 6334-NGC 6357 in an homogeneous way following the previous work of Motte and collaborators. We used the same method to extract the densest cores which are the most likely sites for high-mass star formation. We analyzed the SIMBA/SEST 1.2 mm data presented in Munoz and coworkers, which covers all high-column density areas (A v ≥ 15 mag) of the NGC 6334-NGC 6357 complex and extracted dense cores following the method used for Cygnus X. We constrain the properties of the most massive dense cores (M > 100 M ) using new molecular line observations (as SiO, N 2 H + ,H 13 CO + , HCO + (1-0) and CH 3 CN) with Mopra and a complete cross-correlation with infrared databases (MSX, GLIMPSE, MIPSGAL) and literature. Results. We extracted 163 massive dense cores of which 16 are more massive than 200 M . These high-mass dense cores have a typical FWHM size of 0.37 pc, an average mass of M ∼ 600 M , and a volume-averaged density of ∼1.5 × 10 5 cm −3 . Among these massive dense cores, 6 are good candidates for hosting high-mass infrared-quiet protostars, 9 cores are classified as high-luminosity infrared protostars, and we find only one high-mass starless clump (∼0.3 pc, ∼4 × 10 4 cm −3 ) that is gravitationally bound. Conclusions. Since our sample is derived from a single molecular complex and covers every embedded phase of high-mass star formation, it provides a statistical estimate of the lifetime of massive stars. In contrast to what is found for low-mass class 0 and class I phases, the infrared-quiet protostellar phase of high-mass stars may last as long as their more well known high-luminosity infrared phase. As in Cygnus X, the statistical lifetime of high-mass protostars is shorter than found for nearby, low-mass star-forming regions which implies that high-mass pre-stellar and protostellar cores are in a dynamic state, as expected in a molecular cloud where turbulent and/or dynamical processes dominate.

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Section: Analysis and Resultsmentioning

confidence: 99%

The earliest phases of high-mass star formation: the NGC 6334-NGC 6357 complex

Russeil¹,

Zavagno²,

Motte

et al. 2010

A&A

135

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“…The FellWalker technique searches for sets of disjoint clumps, each containing a single significant peak, using a gradient-tracing scheme. The algorithm is qualitatively similar to the better known Clumpfind (Williams et al 1994) method that has been used extensively. The Fellwalker method, however, is more stable against noise and less susceptible to small changes in the input parameters (Watson 2010).…”

Section: Submillimeter Clumpsmentioning

confidence: 91%

Alma Resolves the Torus of NGC 1068: Continuum and Molecular Line Emission

García‐Burillo

Combes

Almeida

et al. 2016

ApJL

227

235

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We present 450 and 850 μm submillimeter continuum observations of the IC 5146 star-forming region taken as part of the James Clerk Maxwell Telescope Gould Belt Survey. We investigate the location of bright submillimeter (clumped) emission with the larger-scale molecular cloud through comparison with extinction maps, and find that these denser structures correlate with higher cloud column density. Ninety-six individual submillimeter clumps are identified using FellWalker,and their physical properties are examined. These clumps are found to be relatively massive, ranging from 0.5  M to 116  M with a mean mass of 8  M and a median mass of 3.7  M . A stability analysis for the clumps suggests that the majority are (thermally) Jeans stable, withWe further compare the locations of known protostars with the observed submillimeter emission, finding that younger protostars, i.e., Class 0 and I sources, are strongly correlated with submillimeter peaks and that the clumps with protostars are among the most Jeans unstable. Finally, we contrast the evolutionary conditions in the two major star-forming regions within IC 5146: the young cluster associated with the Cocoon Nebula and the more distributed star formation associated with the Northern Streamer filaments. The Cocoon Nebula appears to have converted a higher fraction of its mass into dense clumps and protostars, the clumps are more likely to be Jeans unstable, and a larger fraction of these remaining clumps contain embedded protostars. The Northern Streamer, however, has a larger number of clumps in total and a larger fraction of the known protostars are still embedded within these clumps.

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“…Hence, we use the 250 µm image and the 2D variation of the clumpfind algorithm (Williams, de Geus & Blitz 2011) to detect and identify sub-clumps. The 250 µm image has a higher and optimum resolution of 18 .…”

Section: Properties Of Dust Clumpsmentioning

confidence: 99%

Radio and infrared study of the star-forming region IRAS 20286+4105

Ramachandran

Das

Tej

et al. 2016

Mon. Not. R. Astron. Soc.

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A multi-wavelength investigation of the star forming complex IRAS 20286+4105, located in the Cygnus-X region, is presented here. Near-infrared K-band data is used to revisit the cluster / stellar group identified in previous studies. The radio continuum observations, at 610 and 1280 MHz show the presence of a HII region possibly powered by a star of spectral type B0 -B0.5. The cometary morphology of the ionized region is explained by invoking the bow-shock model where the likely association with a nearby supernova remnant is also explored. A compact radio knot with non-thermal spectral index is detected towards the centre of the cloud. Mid-infrared data from the Spitzer Legacy Survey of the Cygnus-X region show the presence of six Class I YSOs inside the cloud. Thermal dust emission in this complex is modelled using Herschel far-infrared data to generate dust temperature and column density maps. Herschel images also show the presence of two clumps in this region, the masses of which are estimated to be ∼ 175 M and 30 M . The mass-radius relation and the surface density of the clumps do not qualify them as massive star forming sites. An overall picture of a runaway star ionizing the cloud and a triggered population of intermediate-mass, Class I sources located toward the cloud centre emerges from this multiwavelength study. Variation in the dust emissivity spectral index is shown to exist in this region and is seen to have an inverse relation with the dust temperature.

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Determining structure in molecular clouds

Cited by 907 publications

References 0 publications

The earliest phases of high-mass star formation: the NGC 6334-NGC 6357 complex

The earliest phases of high-mass star formation: the NGC 6334-NGC 6357 complex

Alma Resolves the Torus of NGC 1068: Continuum and Molecular Line Emission

Radio and infrared study of the star-forming region IRAS 20286+4105

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