Numerical Star-Formation Studies— A Status Report

Klessen, Ralf S.; Krumholz, Mark R.; Heitsch, Fabian

doi:10.1166/asl.2011.1207

Cited by 31 publications

(33 citation statements)

References 228 publications

(330 reference statements)

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“…The CO line may originate in the densest regions created by shocks in a turbulent medium (Klessen et al 2009). Simulations of a turbulent interstellar medium indicate that these dense regions with CO might not always be the most shielded ones .…”

Section: Resultsmentioning

confidence: 99%

LABOCA observations of giant molecular clouds in the southwest region of the Small Magellanic Cloud

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Rubio

Boulanger

et al. 2010

A&A

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Context. The amount of molecular gas is a key to understanding the future star formation in a galaxy. Because H 2 is difficult to observe directly in dense and cold clouds, tracers such as the CO molecule are used. However, at low metallicities especially, CO only traces the shielded interiors of the clouds. In this context, millimeter dust emission can be used as a tracer to unveil the total dense gas masses. However, the comparison of masses deduced from the continuum SIMBA 1.2 mm emission and virial masses (understood to trace the entire potential of the clouds) in a sample of giant molecular clouds in the Small Magellanic Cloud (SMC) by previous studies found a discrepancy between these two quantities that requires explanation. Aims. We attempt to more accurately assess possible uncertainties in the dust emission observed in the sample of giant molecular clouds from the SMC. We focus on the mass comparison in the densest parts of the giant molecular clouds where CO is detected to confirm the mass discrepancy previously observed. Methods. New observations of the southwest region of the SMC were obtained with the LABOCA camera on the APEX telescope. All the giant molecular clouds previously observed in CO are detected and their emission at 870 μm is compared to ancillary data. The different contributions to the sub-millimeter emission are estimated, as well as dust properties (temperatures, emissivities), to determine molecular cloud masses precisely. Results. The (sub-)millimeter emission observed in the giant molecular clouds in the southwest region of the SMC is dominated by dust emission, and masses are deduced for the part of each cloud where CO is detected and compared to the virial masses. The mass discrepancy between both methods is confirmed at 870 μm using the LABOCA observations: the virial masses are on average 4 times lower than the masses of dense gas inferred from dust emission, in contrast to what is observed for equivalent clouds in our Galaxy. Conclusions. At present, the origin of this mass discrepancy in the SMC remains unknown. The direct interpretation of this effect is that the CO linewidth used to compute virial masses do not measure the full velocity distribution of the gas. Geometrical effects and uncertainties in the dust properties are also discussed.

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Section: Resultsmentioning

confidence: 99%

LABOCA observations of giant molecular clouds in the southwest region of the Small Magellanic Cloud

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Rubio

Boulanger

et al. 2010

A&A

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“…Mellema et al 2006;Peters et al 2010) Miao et al 2006;Dale et al 2007;Bisbas et al 2009). Klessen et al (2009) andMac Low et al (2007) present recent reviews of the numerical methods employed.…”

Section: Some Common Approximationsmentioning

confidence: 99%

Ionisation Feedback in Star and Cluster Formation Simulations

Ercolano

Gritschneder

2010

Proc. IAU

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Abstract. Feedback from photoionisation may dominate on parsec scales in massive starforming regions. Such feedback may inhibit or enhance the star formation efficiency and sustain or even drive turbulence in the parent molecular cloud. Photoionisation feedback may also provide a mechanism for the rapid expulsion of gas from young clusters' potentials, often invoked as the main cause of 'infant mortality'. There is currently no agreement, however, with regards to the efficiency of this process and how environment may affect the direction (positive or negative) in which it proceeds. The study of the photoionisation process as part of hydrodynamical simulations is key to understanding these issues, however, due to the computational demand of the problem, crude approximations for the radiation transfer are often employed.We will briefly review some of the most commonly used approximations and discuss their major drawbacks. We will then present the results of detailed tests carried out using the detailed photoionisation code mocassin and the SPH+ionisation code iVINE code, aimed at understanding the error introduced by the simplified photoionisation algorithms. This is particularly relevant as a number of new codes have recently been developed along those lines.We will finally propose a new approach that should allow to efficiently and self-consistently treat the photoionisation problem for complex radiation and density fields.

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“…While this model of flow‐driven structure generation shows rapid onset of star formation while the parental cloud is forming, it cannot account for the observed low star formation rates (Klessen et al 2009). As there is a continuous instream of gas into the collision region, too much of the accumulated gas will be converted into stars.…”

Section: Introductionmentioning

confidence: 98%

“…It has been suggested that this fragmentation results from thermal processes in the interstellar medium (ISM; see e.g. Klessen, Krumholz & Heitsch 2009, and references therein). For a range of pressures and the heating and cooling rates appropriate for diffuse atomic gas, two thermally stable phases exist, i.e.…”

Section: Introductionmentioning

confidence: 99%

Shock-triggered formation of magnetically dominated clouds - II. Weak shock-cloud interaction in three dimensions

Loo¹,

Falle²,

Hartquist³

2010

Monthly Notices of the Royal Astronomical Society

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To understand the formation of a magnetically dominated molecular cloud from an atomic cloud, we study the interaction of a weak, radiative shock with a magnetized cloud. The thermally stable warm atomic cloud is initially in static equilibrium with the surrounding hot ionized gas. A shock propagating through the hot medium then interacts with the cloud. We follow the dynamical evolution of the shocked cloud with a time‐dependent ideal magnetohydrodynamic code. By performing the simulations in 3D, we investigate the effect of different magnetic field orientations including parallel, perpendicular and oblique to the shock normal. We find that the angle between the shock normal and the magnetic field must be small to produce clouds with properties similar to observed molecular clouds.

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Numerical Star-Formation Studies— A Status Report

Cited by 31 publications

References 228 publications

LABOCA observations of giant molecular clouds in the southwest region of the Small Magellanic Cloud

LABOCA observations of giant molecular clouds in the southwest region of the Small Magellanic Cloud

Ionisation Feedback in Star and Cluster Formation Simulations

Shock-triggered formation of magnetically dominated clouds - II. Weak shock-cloud interaction in three dimensions

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