Corrections to virial estimates of molecular cloud masses

MacLaren, Iain; Richardson, K. M.; Wolfendale, A.W.

doi:10.1086/166791

Cited by 306 publications

(296 citation statements)

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“…To investigate the stability of the cores, we estimated their virial masses, M virial , by using the expression given by MacLaren et al (1988), M virial = 0.509 d θ ΔV 2 , where d is the distance in kpc, θ is the size of the cores in arcsec, and ΔV is the line width in km s −1 . The virial mass depends on the density profile.…”

Section: Stability Of the Filament And The Coresmentioning

confidence: 99%

“…The virial mass depends on the density profile. For a power-law density distribution of the type ρ ∝ r −p , the virial mass in Table 5 should be multiplied by a factor α = 3(5 − 2p)/5(3 − p), which is 0.6 ≤ α ≤ 1 for 0 ≤ p ≤ 2 (MacLaren et al 1988). Thus, the values given in Table 5 should not be reduced by more than a factor 2.…”

Section: Stability Of the Filament And The Coresmentioning

confidence: 99%

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Filamentary structure and Keplerian rotation in the high-mass star-forming region G35.03+0.35 imaged with ALMA

Beltrán

Sánchez-Monge

Cesaroni

et al. 2014

A&A

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Context. Theoretical scenarios propose that high-mass stars are formed by disk-mediated accretion. Aims. To test the theoretical predictions on the formation of massive stars, we wish to make a thorough study at high-angular resolution of the structure and kinematics of the dust and gas emission toward the high-mass star-forming region G35.03+0.35, which harbors a disk candidate around a B-type (proto)star. Methods. We carried out ALMA Cycle 0 observations at 870 μm of dust of typical high-density, molecular outflow, and cloud tracers with resolutions of <0. 5. Complementary Subaru COMICS 25 μm observations were carried out to trace the mid-infrared emission toward this star-forming region. Results. The submillimeter continuum emission has revealed a filamentary structure fragmented into six cores, called A-F. The filament could be in quasi-equilibrium taking into account that the mass per unit length of the filament, 200-375 M /pc, is similar to the critical mass of a thermally and turbulently supported infinite cylinder, ∼335 M /pc. The cores, which are on average separated by ∼0.02 pc, have deconvolved sizes of 1300-3400 AU, temperatures of 35-240 K, H 2 densities >10 7 cm −3 , and masses in the range 1-5 M , and they are subcritical. Core A, which is associated with a hypercompact Hii region and could be the driving source of the molecular outflow observed in the region, is the most chemically rich source in G35.03+0.35 with strong emission of typical hot core tracers such as CH 3 CN. Tracers of high density and excitation show a clear velocity gradient along the major axis of the core, which is consistent with a disk rotating about the axis of the associated outflow. The PV plots along the SE-NW direction of the velocity gradient show clear signatures of Keplerian rotation, although infall could also be present, and they are consistent with the pattern of an edge-on Keplerian disk rotating about a star with a mass in the range 5-13 M . The high t ff /t rot ratio for core A suggests that the structure rotates fast and that the accreting material has time to settle into a centrifugally supported disk. Conclusions. G35.03+0.35 is one of the most convincing examples of Keplerian disks rotating about high-mass (proto)stars. This supports theoretical scenarios according to which high-mass stars, at least B-type stars, would form through disk-mediated accretion.

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Section: Stability Of the Filament And The Coresmentioning

confidence: 99%

Section: Stability Of the Filament And The Coresmentioning

confidence: 99%

Filamentary structure and Keplerian rotation in the high-mass star-forming region G35.03+0.35 imaged with ALMA

Beltrán

Sánchez-Monge

Cesaroni

et al. 2014

A&A

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“…where G is the gravitational constant, R the cloud radius, k a factor depending on the radial density distribution, and σ the three-dimensional velocity dispersion (MacLaren et al 1988). σ is given by the equation…”

Section: Mass Calculationmentioning

confidence: 99%

Multiwavelength study of the high-latitude cloud L1642: chain of star formation

Malinen

Juvela

Zahorecz

et al. 2014

A&A

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Context. L1642 is one of the two high galactic latitude (|b| > 30 • ) clouds confirmed to have active star formation. Aims. We examine the properties of this cloud, especially the large-scale structure, dust properties, and compact sources at different stages of star formation.Methods. We present high-resolution far-infrared and submillimetre observations with the Herschel and AKARI satellites and millimetre observations with the AzTEC/ASTE telescope, which we combined with archive data from near-and mid-infrared (2MASS, WISE) to millimetre wavelength observations (Planck).Results. The Herschel observations, combined with other data, show a sequence of objects from a cold clump to young stellar objects (YSOs) at different evolutionary stages. Source B-3 (2MASS J04351455-1414468) appears to be a YSO forming inside the L1642 cloud, instead of a foreground brown dwarf, as previously classified. Herschel data reveal striation in the diffuse dust emission around the cloud L1642. The western region shows striation towards the NE and has a steeper column density gradient on its southern side. The densest central region has a bow-shock like structure showing compression from the west and has a filamentary tail extending towards the east. The differences suggest that these may be spatially distinct structures, aligned only in projection. We derive values of the dust emission cross-section per H nucleon of σ e (250 μm) = 0.5−1.5 × 10 −25 cm 2 /H for different regions of the cloud. Modified black-body fits to the spectral energy distribution of Herschel and Planck data give emissivity spectral index β values 1.8-2.0 for the different regions. The compact sources have lower β values and show an anticorrelation between T and β. Conclusions. Markov chain Monte Carlo calculations demonstrate the strong anticorrelation between β and T errors and the importance of millimetre wavelength Planck data in constraining the estimates. L1642 reveals a more complex structure and sequence of star formation than previously known.

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“…From our observational data we can obtain estimates for the clump mass, M , its virial mass, M vir , and radius R. With R known, the virial mass for a sphere of constant density can be estimated from [58] …”

Section: Clump Physicsmentioning

confidence: 99%

Observations of chemical differentiation in clumpy molecular clouds

Buckle¹,

Rodgers

Wirström

et al. 2006

Faraday Discuss.

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We have extensively mapped a sample of dense molecular clouds (L1512, TMC-1C, L1262, Per 7, L1389, L1251E) in lines of HC 3 N, CH 3 OH, SO and C 18 O. We demonstrate that a high degree of chemical differentiation is present in all of the observed clouds. We analyse the molecular maps for each cloud, demonstrating a systematic chemical differentiation across the sample, which we relate to the evolutionary state of the cloud. We relate our observations to the cloud physical, kinematical and evolutionary properties, and also compare them to the predictions of simple chemical models. The implications of this work for understanding the origin of the clumpy structures and chemical differentiation observed in dense clouds are discussed.

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Corrections to virial estimates of molecular cloud masses

Cited by 306 publications

References 0 publications

Filamentary structure and Keplerian rotation in the high-mass star-forming region G35.03+0.35 imaged with ALMA

Filamentary structure and Keplerian rotation in the high-mass star-forming region G35.03+0.35 imaged with ALMA

Multiwavelength study of the high-latitude cloud L1642: chain of star formation

Observations of chemical differentiation in clumpy molecular clouds

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