Dr21 Main: A Collapsing Cloud

Kirby, Larry

doi:10.1088/0004-637x/694/2/1056

Cited by 35 publications

(41 citation statements)

References 32 publications

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“…Of the objects in the Hertz archive, only the central regions of OMC-1 ) and DR21-Main (Kirby 2009) have, at this time, been re-observed with SHARP at this increased resolution. However, comparisons of these data have shown the obvious utility of increased resolution for careful studies of turbulence in molecular clouds, particularly in estimates of the turbulent correlation length Houde et al 2009).…”

Section: Resultsmentioning

confidence: 92%

350 μm POLARIMETRY FROM THE CALTECH SUBMILLIMETER OBSERVATORY

Dotson¹,

Vaillancourt²,

Kirby³

et al. 2010

ApJS

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106

156

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We present a summary of data obtained with the 350 μm polarimeter, Hertz, at the Caltech Submillimeter Observatory. We give tabulated results and maps showing polarization vectors and intensity contours. The summary includes over 4300 individual measurements in 56 Galactic sources and two galaxies. Of these measurements, 2153 have P 3σ p statistical significance. The median polarization of the entire data set is 1.46%.

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Section: Resultsmentioning

confidence: 92%

350 μm POLARIMETRY FROM THE CALTECH SUBMILLIMETER OBSERVATORY

Dotson¹,

Vaillancourt²,

Kirby³

et al. 2010

ApJS

Self Cite

106

156

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“…4.2). The orientation of the sub-filaments is not arbitrary: they follow the magnetic field lines that run orthogonal to the NS-orientated DR21 filament (Vallée & Fiege 2006;Kirby 2009). Magnetohydrodynamic turbulence models precisely produce such filamentary structures (Fig.…”

Section: Role Of Magnetic Field: Mhd With Self-gravity Modelingmentioning

confidence: 99%

Dynamic star formation in the massive DR21 filament

Schneider¹,

Csengeri²,

Bontemps

et al. 2010

A&A

313

386

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Context. The formation of massive stars is a highly complex process in which it is unclear whether the star-forming gas is in global gravitational collapse or an equilibrium state supported by turbulence and/or magnetic fields. In addition, magnetic fields may play a decisive role in the star-formation process since they influence the efficiency of gas infall onto the protostar. Aims. By studying one of the most massive and dense star-forming regions in the Galaxy at a distance of less than 3 kpc, i.e. the filament containing the well-known sources DR21 and DR21(OH), we attempt to obtain observational evidence to help us to discriminate between these two views. Methods. We use molecular line data from our 13 CO 1 → 0, CS 2 → 1, and N 2 H + 1 → 0 survey of the Cygnus X region obtained with the FCRAO and high-angular resolution observations in isotopomeric lines of CO, CS, HCO + , N 2 H + , and H 2 CO, obtained with the IRAM 30 m telescope, to investigate the distribution of the different phases of molecular gas. Gravitational infall is identified by the presence of inverse P Cygni profiles that are detected in optically thick lines, while the optically thinner isotopomers are found to reach a peak in the self-absorption gap. Results. We observe a complex velocity field and velocity dispersion in the DR21 filament in which regions of the highest columndensity, i.e., dense cores, have a lower velocity dispersion than the surrounding gas and velocity gradients that are not (only) due to rotation. Infall signatures in optically thick line profiles of HCO + and 12 CO are observed along and across the whole DR21 filament. By modelling the observed spectra, we obtain a typical infall speed of ∼0.6 km s −1 and mass accretion rates of the order of a few 10 −3 M yr −1 for the two main clumps constituting the filament. These massive clumps (4900 and 3300 M at densities of around 10 5 cm −3 within 1 pc diameter) are both gravitationally contracting (with free-fall times much shorter than sound crossing times and low virial parameter α). The more massive of the clumps, DR21(OH), is connected to a sub-filament, apparently "falling" onto the clump. This filament runs parallel to the magnetic field. Conclusions. All observed kinematic features in the DR21 filament (velocity field, velocity dispersion, and infall), its filamentary morphology, and the existence of (a) sub-filament(s) can be explained if the DR21 filament was formed by the convergence of flows on large scales and is now in a state of global gravitational collapse. Whether this convergence of flows originated from self-gravity on larger scales or from other processes cannot be determined by the present study. The observed velocity field and velocity dispersion are consistent with results from (magneto)-hydrodynamic simulations where the cores lie at the stagnation points of convergent turbulent flows.

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“…Overlapped on the P − flux plot of DR 21 in Figure 4 is a P −σ plot from the same sky positions. We note that theσ data in Figure 4 is based on HCN (4-3) lines (Kirby 2009), which could be optically thicker than the 350 µm dust emission, from which the polarimetry data is derived. So the correlation may change when optically thinner lines are used forσ , and the trend may be enhanced.…”

Section: Probing Into Deep Cloudsmentioning

confidence: 99%

Anchoring Magnetic Field in Turbulent Molecular Clouds

Dowell

Goodman

et al. 2009

ApJ

100

118

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One of the key problems in star formation research is to determine the role of magnetic fields. Starting from the atomic inter-cloud medium (ICM) which has density n H ~ 1 cm −3 , gas must accumulate from a volume several hundred pc across in order to form a typical molecular cloud. Star formation usually occurs in cloud cores, which have linear sizes below 1 pc and densities n H2 > 10 5 cm −3 . With current technologies, it is hard to probe magnetic fields at scales lying between the accumulation length and the size of cloud cores, a range corresponds to many levels of turbulent eddy cascade, and many orders of magnitude of density amplification. For field directions detected from the two extremes, however, we show here that a significant correlation is found. Comparing this result with molecular cloud simulations, only the sub-Alfvénic cases result in field orientations consistent with our observations.

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Dr21 Main: A Collapsing Cloud

Cited by 35 publications

References 32 publications

350 μm POLARIMETRY FROM THE CALTECH SUBMILLIMETER OBSERVATORY

350 μm POLARIMETRY FROM THE CALTECH SUBMILLIMETER OBSERVATORY

Dynamic star formation in the massive DR21 filament

Anchoring Magnetic Field in Turbulent Molecular Clouds

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