Turbulence in giant molecular clouds: the effect of photoionization feedback

Boneberg, Dominika M.; Dale, James E.; Girichidis, Philipp; Ercolano, Barbara

doi:10.1093/mnras/stu2498

Cited by 21 publications

(20 citation statements)

References 70 publications

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“…Here, the VSF is almost flat, or even slightly increasing towards smaller separation scales. This kind of profile is typical for gas that is gravitationally contracting (Boneberg et al 2015;Burkhart et al 2015). Gas moves into the inner regions of the cloud, reducing the average lag distances, while being accelerated by the infall to higher velocity.…”

Section: Examplesmentioning

confidence: 90%

How do velocity structure functions trace gas dynamics in simulated molecular clouds?

Chira

Ibáñez-Mejía

Low

et al. 2019

A&A

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Context. Supersonic disordered flows accompany the formation and evolution of molecular clouds (MCs). It has been argued that this is turbulence that can support against gravitational collapse and form hierarchical sub-structures. Aims. We investigate the time evolution of simulated MCs to investigate: What physical process dominates the driving of turbulent flows? How can these flows be characterised? Are they consistent with uniform turbulence or gravitational collapse? Do the simulated flows agree with observations? Methods. We analyse three MCs that have formed self-consistently within kiloparsec-scale numerical simulations of the interstellar medium (ISM). The simulated ISM evolves under the influence of physical processes including self-gravity, stratification, magnetic fields, supernova-driven turbulence, and radiative heating and cooling. We characterise the flows using velocity structure functions (VSFs) with and without density weighting or a density cutoff, and computed in one or three dimensions. However, we do not include optical depth effects that can hide motions in the densest gas, limiting comparison of our results with observations. Results. In regions with sufficient resolution, the density-weighted VSFs initially appear to follow the expectations for uniform turbulence, with a first-order power-law exponent consistent with Larson's size-velocity relationship. SN blast wave impacts on MCs produce short-lived coherent motions at large scales, increasing the scaling exponents for a crossing time. Gravitational contraction drives small-scale motions, producing scaling coefficients that drop or even turn negative as small scales become dominant. Removing the density weighting eliminates this effect as that emphasises the diffuse ISM. Conclusions. We conclude that two different effects coincidentally reproduce Larson's size velocity relationship. Initially, uniform turbulence dominates, so the energy cascade produces VSFs consistent with Larson's relationship. Later, contraction dominates, the density-weighted VSFs become much shallower or even inverted, but the relationship of the global average velocity dispersion of the MCs to their radius follows Larson's relationship, reflecting virial equilibrium or free-fall collapse. The injection of energy by shocks is visible in the VSFs, but decays within a crossing time.

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Section: Examplesmentioning

confidence: 90%

How do velocity structure functions trace gas dynamics in simulated molecular clouds?

Chira

Ibáñez-Mejía

Low

et al. 2019

A&A

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“…The larger a cluster, the higher the probability it contains a massive star (only ∼0.3% of the total number of stars in a given cluster is more massive than 8 M ). Once formed, massive stars strongly influence their environment (Boneberg et al 2015). They photo-dissociate the surrounding gas, creating a zone of hot and diffuse gas (HII region) where star formation is inhibited, and emit powerful winds.…”

Section: Previous Modelsmentioning

confidence: 99%

The abundance of²⁶Al-rich planetary systems in the Galaxy

Gounelle

2015

A&A

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One of the most puzzling properties of the solar system is the high abundance at its birth of 26 Al, a short-lived radionuclide with a mean life of 1 Myr. Now decayed, it has left its imprint in primitive meteoritic solids. The origin of 26 Al in the early solar system has been debated for decades and strongly constrains the astrophysical context of the Sun and planets formation. We show that, according to the present understanding of star-formation mechanisms, it is very unlikely that a nearby supernova has delivered 26 Al into the nascent solar system. A more promising model is the one whereby the Sun formed in a wind-enriched, 26 Al-rich dense shell surrounding a massive star (M > 32 M ). We calculate that the probability of any given star in the Galaxy being born in such a setting, corresponding to a well-known mode of star formation, is of the order of 1%. It means that our solar system, though not the rule, is relatively common and that many exo-planetary systems in the Galaxy might exhibit comparable enrichments in 26 Al. Such enrichments played an important role in the early evolution of planets because 26 Al is the main heat source for planetary embryos.

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“…Of these mechanism, radiative feedback has been suggested as being most important during the early phases of cluster formation, particularly in clusters which are hosting massive star formation (Whitworth 1979;Matzner 2002;Murray et al 2010;Dale et al 2012;Bate 2012). The heating and ionization of the gas surrounding star-forming clusters prevents further fragmentation, and expanding HII regions can drive further turbulence (Gritschneder et al 2009;Boneberg et al 2015). Direct radiation pressure from high energy photons interacting with dust grains can also drive strong outflows.…”

Section: Introductionmentioning

confidence: 99%

Simulating radiative feedback and star cluster formation in GMCs – II. Mass dependence of cloud destruction and cluster properties

Howard

Harris

2017

Monthly Notices of the Royal Astronomical Society

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The process of radiative feedback in Giant Molecular Clouds (GMCs) is an important mechanism for limiting star cluster formation through the heating and ionization of the surrounding gas. We explore the degree to which radiative feedback affects early ( 5 Myr) cluster formation in GMCs having masses that range from 10 4−6 M using the FLASH code. The inclusion of radiative feedback lowers the efficiency of cluster formation by 20-50% relative to hydrodynamic simulations. Two models in particular -5×10 4 and 10 5 M -show the largest suppression of the cluster formation efficiency, corresponding to a factor of ∼2. For these clouds only, the internal energy, a measure of the energy injected by radiative feedback, exceeds the gravitational potential for a significant amount of time. We find a clear relation between the maximum cluster mass, M cl,max , formed in a GMC of mass M GM C ; M cl,max ∝ M 0.81 GM C . This scaling result suggests that young globular clusters at the necessary scale of 10 6 M form within host GMCs of masses near ∼ 5 × 10 7 M . We compare simulated cluster mass distributions to the observed embedded cluster mass function (dlog(N )/dlog(M ) ∝ M β where β = -1) and find good agreement (β = -0.99±0.14) only for simulations including radiative feedback, indicating this process is important in controlling the growth of young clusters. However, the high star formation efficiencies, which range from 16-21%, and high star formation rates compared to locally observed regions suggest other feedback mechanisms are also important during the formation and growth of stellar clusters.

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Turbulence in giant molecular clouds: the effect of photoionization feedback

Cited by 21 publications

References 70 publications

How do velocity structure functions trace gas dynamics in simulated molecular clouds?

How do velocity structure functions trace gas dynamics in simulated molecular clouds?

The abundance of²⁶Al-rich planetary systems in the Galaxy

Simulating radiative feedback and star cluster formation in GMCs – II. Mass dependence of cloud destruction and cluster properties

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Turbulence in giant molecular clouds: the effect of photoionization feedback

Cited by 21 publications

References 70 publications

How do velocity structure functions trace gas dynamics in simulated molecular clouds?

How do velocity structure functions trace gas dynamics in simulated molecular clouds?

The abundance of26Al-rich planetary systems in the Galaxy

Simulating radiative feedback and star cluster formation in GMCs – II. Mass dependence of cloud destruction and cluster properties

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The abundance of²⁶Al-rich planetary systems in the Galaxy