The CARMA-NRO Orion Survey

Suri, S.; Sánchez-Monge, Á.; Schilke, P.; Clarke, S. D.; Smith, Rowan J.; Ossenkopf-Okada, Volker; Klessen, Ralf S.; Padoan, Paolo; Goldsmith, Paul F.; Arce, Héctor G.; Bally, John; Carpenter, John M.; Ginsburg, Adam; Johnstone, Doug; Kauffmann, Jens; Kong, Shuo; Lis, D. C.; Mairs, Steve; Pillai, T.; Pineda, Jaime E.; Duarte-Cabral, A.

doi:10.1051/0004-6361/201834049

Cited by 63 publications

(83 citation statements)

References 51 publications

(78 reference statements)

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“…These individual peaks have widths comparable to those seen in Federrath (2016), but the effect of averaging all points together results in a much broader distribution. A very similar phenomenon has been found by Suri et al (2019) in C 18 O observations of the Orion A molecular cloud, who show that the width of the average filament profile is much broader than the typical width of the individual density peaks.…”

Section: R E S U Lt Ssupporting

confidence: 83%

“…Ossenkopf & Henning 1994;Howard et al 2019). If molecular-line radiation is used to define filaments (rather than dust continuum emission), the inferred filament widths depend on the molecule oberved, from ∼0.01 pc for N 2 H + (Hacar et al 2018) to 0.4 pc for 13 CO (Panopoulou et al 2014), although Suri et al (2019) find a value in agreement with Arzoumanian et al (2011) using C 18 O. Smith, Glover & Klessen (2014) and Panopoulou et al (2017) have also raised concerns about the effect of the fitting method on estimates of filament width.…”

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confidence: 99%

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Synthetic line and continuum observations of simulated turbulent clouds: the apparent widths of filaments

Priestley

Whitworth

2020

Monthly Notices of the Royal Astronomical Society

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Filamentary structures are ubiquitous in observations of real molecular clouds, and also in simulations of turbulent, self-gravitating gas. However, making comparisons between observations and simulations is complicated by the difficulty of estimating volume-densities observationally. Here, we have post-processed hydrodynamical simulations of a turbulent isothermal molecular cloud, using a full time-dependent chemical network. We have then run radiative transfer models to obtain synthetic line and continuum intensities that can be compared directly with those observed. We find that filaments have a characteristic width of ∼ 0.1 pc, both on maps of their true surface density, and on maps of their 850 μm dust-continuum emission, in agreement with previous work. On maps of line emission from CO isotopologues, the apparent widths of filaments are typically several times larger because the line intensities are poorly correlated with the surface density. On maps of line emission from dense-gas tracers such as N2H+ and HCN, the apparent widths of filaments are $\lesssim 0.1\, {\rm pc}$. Thus, current observations of molecular-line emission are compatible with the universal 0.1 pc filament width inferred from Herschel observations, provided proper account is taken of abundance, optical-depth, and excitation considerations. We find evidence for ∼0.4 km s−1 radial velocity differences across filaments. These radial velocity differences might be a useful indicator of the mechanism by which a filament has formed or is forming, for example the turbulent cloud scenario modelled here, as against other mechanisms such as cloud-cloud collisions.

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Section: R E S U Lt Ssupporting

confidence: 83%

mentioning

confidence: 99%

Synthetic line and continuum observations of simulated turbulent clouds: the apparent widths of filaments

Priestley

Whitworth

2020

Monthly Notices of the Royal Astronomical Society

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“…André et al 2010;Men'shchikov et al 2010;Arzoumanian et al 2011;Schneider et al 2012). Similar structures are also observed in C 18 O and 13 CO emission (Panopoulou et al 2014;Suri et al 2019), which appear to decompose into smaller scale 'fibers' when a higher critical density tracer is used (Hacar et al 2013(Hacar et al , 2016Henshaw et al 2016) Filament fragmentation differs from 3D Jeans fragmentation (Jeans 1902) (usually considered in spherical symmetry for simplicity) in that it occurs above a critical line mass (Larson 1973(Larson , 1985Inutsuka & Miyama 1992, takes place over a longer time-scale (Pon et al 2012), and occurs on a characteristic length scale (Larson 1985). In addition to determining fragmentation within the cloud, filaments may enhance the accretion onto cores at the 'hubs' where they intersect, enabling the assembly of the high mass end of the stellar initial mass function Myers 2011;Peretto et al 2012;Smith et al 2016).…”

Section: Introductionsupporting

confidence: 64%

The Cloud Factory I: Generating resolved filamentary molecular clouds from galactic-scale forces

Smith

Treß

Sormani

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We introduce a new suite of simulations, "The Cloud Factory", which self-consistently forms molecular cloud complexes at high enough resolution to resolve internal substructure (up to 0.25 M in mass) all while including galactic-scale forces. We use a version of the Arepo code modified to include a detailed treatment of the physics of the cold molecular ISM, and an analytical galactic gravitational potential for computational efficiency. The simulations have nested levels of resolution, with the lowest layer tied to tracer particles injected into individual cloud complexes. These tracer refinement regions are embedded in the larger simulation so continue to experience forces from outside the cloud. This allows the simulations to act as a laboratory for testing the effect of galactic environment on star formation. Here we introduce our method and investigate the effect of galactic environment on filamentary clouds. We find that cloud complexes formed after a clustered burst of feedback, have shorter lengths and are less likely to fragment compared to quiescent clouds (e.g. the Musca filament) or those dominated by the galactic potential (e.g. Nessie). Spiral arms and differential rotation preferentially align filaments, but strong feedback randomises them. Long filaments formed within the cloud complexes are necessarily coherent with low internal velocity gradients, which has implications for the formation of filamentary star-clusters. Cloud complexes formed in regions dominated by supernova feedback have fewer star-forming cores, and these are more widely distributed. These differences show galactic-scale forces can have a significant impact on star formation within molecular clouds.

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“…For M43, we use CO data observed with the Combined Array for Millimeter-Wave Astronomy (CARMA), within the CARMA-NRO Orion Survey project (Kong et al 2018;Suri et al 2019). The molecular lines observed are 13 CO J = 1-0 and C 18 O J = 1-0 for the seven [C ii] positions.…”

Section: Co Molecular Emissionmentioning

confidence: 99%

[C II] 158 μm self-absorption and optical depth effects

Guevara

Stützki

Ossenkopf-Okada

et al. 2020

A&A

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Context. The [C ii] 158 µm far-infrared (FIR) fine-structure line is one of the most important cooling lines of the star-forming interstellar medium (ISM). It is used as a tracer of star formation efficiency in external galaxies and to study feedback effects in parental clouds. High spectral resolution observations have shown complex structures in the line profiles of the [C ii] emission. Aims. Our aim is to determine whether the complex profiles observed in [ 12 C ii] are due to individual velocity components along the line-of-sight or to self-absorption based on a comparison of the [ 12 C ii] and isotopic [ 13 C ii] line profiles. Methods. Deep integrations with the SOFIA/upGREAT 7-pixel array receiver in the sources of M43, Horsehead PDR, Monoceros R2, and M17 SW allow for the detection of optically thin [ 13 C ii] emission lines, along with the [ 12 C ii] emission lines, with a high signalto-noise ratio (S/N). We first derived the [ 12 C ii] optical depth and the [C ii] column density from a single component model. However, the complex line profiles observed require a double layer model with an emitting background and an absorbing foreground. A multicomponent velocity fit allows us to derive the physical conditions of the [C ii] gas: column density and excitation temperature. Results. We find moderate to high [ 12 C ii] optical depths in all four sources and self-absorption of [ 12 C ii] in Mon R2 and M17 SW. The high column density of the warm background emission corresponds to an equivalent A v of up to 41 mag. The foreground absorption requires substantial column densities of cold and dense [C ii] gas, with an equivalent A v ranging up to about 13 mag. Conclusions. The column density of the warm background material requires multiple photon-dominated region (PDR) surfaces stacked along the line of sight and in velocity. The substantial column density of dense and cold foreground [C ii] gas detected in absorption cannot be explained with any known scenario and we can only speculate on its origins. Key words. ISM:clouds -ISM:individual objects: M43 -ISM:individual objects: M17 -photon-dominated region (PDR) -ISM:individual objects: Horsehead -ISM:individual objects: MonR2 1 At that time, the spectroscopic data were less accurate and the wavelength of the transition was assumed to fall at 157 µm instead of 158 µm.Article number, page 1 of 40 A&A proofs: manuscript no. 34380corr_2 mentum change F=2→1, F=1→0, and F=1→1. The frequencies of the fine structure transitions of both isotopes were determined by Cooksy et al. (1986). The astronomical observations are fully consistent with these frequencies, as was discussed by Ossenkopf et al. (2013), who also noted that the relative strengths of the [ 13 C ii] hyperfine satellites (s F→F , see Table 1) given by Cooksy et al. (1986) are incorrect. We summarize all the relevant [ 12 C ii] and [ 13 C ii] spectroscopic parameters in Table 1, including the velocity offsets of the [ 13 C ii] hyperfine components relative to [ 12 C ii]. The frequency separation of the hyperfi...

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The CARMA-NRO Orion Survey

Cited by 63 publications

References 51 publications

Synthetic line and continuum observations of simulated turbulent clouds: the apparent widths of filaments

Synthetic line and continuum observations of simulated turbulent clouds: the apparent widths of filaments

The Cloud Factory I: Generating resolved filamentary molecular clouds from galactic-scale forces

[C II] 158 μm self-absorption and optical depth effects

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The CARMA-NRO Orion Survey

Cited by 63 publications

References 51 publications

Synthetic line and continuum observations of simulated turbulent clouds: the apparent widths of filaments

Synthetic line and continuum observations of simulated turbulent clouds: the apparent widths of filaments

The Cloud Factory I: Generating resolved filamentary molecular clouds from galactic-scale forces

[C II] 158 μm self-absorption and optical depth effects

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[C II] 158 μm self-absorption and optical depth effects