Star formation in a turbulent framework: from giant molecular clouds to protostars

Guszejnov, Dávid; Hopkins, Philip F.

doi:10.1093/mnras/stw619

Cited by 18 publications

(13 citation statements)

References 43 publications

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“…Overall, this work emphasizes the usefulness of the w2PF (A17) to measure clump sizes in observed and simulated datasets and it demonstrates the power of the clump size scaling relation of F17 to diagnose in-situ clump formation via VDIs. This parallels recent developments on spatial correlations of star-forming disks on scales larger than clumps (Combes et al 2012;Hopkins 2012;Grasha et al 2017), as well as within individual clumps (Guszejnov & Hopkins 2016). Spatial correlations can therefore be regarded as an essential modern tool for studying the physics of star-forming disks.…”

Section: Discussionsupporting

confidence: 53%

Size Scaling of Clump Instabilities in Turbulent, Feedback-regulated Disks

Ali¹,

Obreschkow²,

Wang³

et al. 2019

ApJ

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We explore the scaling between the size of star-forming clumps and rotational support in massively star-forming galactic disks. The analysis relies on simulations of a clumpy galaxy at z = 2 and the observed DYNAMO sample of rare clumpy analogs at z ≈ 0.1 to test a predictive clump size scaling proposed by Fisher et al. (2017a) in the context of the Violent Disk Instability (VDI) theory. We here determine the clump sizes using a recently presented 2point estimator, which is robust against resolution/noise effects, hierarchical clump substructure, clump-clump overlap and other galactic substructure. After verifying Fisher's clump scaling relation for the DYNAMO observations, we explore whether this relation remains characteristic of the VDI theory, even if realistic physical processes, such as local asymetries and stellar feedback, are included in the model. To this end, we rely on hydrodynamic zoom-simulations of a Milky Way-mass galaxy with four different feedback prescriptions. We find that, during its marginally stable epoch at z = 2, this mock galaxy falls on the clump scaling relation, although its position on this relation depends on the feedback model. This finding implies that Toomre-like stability considerations approximately apply to large (∼ kpc) instabilities in marginally stable turbulent disks, irrespective of the feedback model, but also emphasizes that the global clump distribution of a turbulent disk depends strongly on feedback.

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Section: Discussionsupporting

confidence: 53%

Size Scaling of Clump Instabilities in Turbulent, Feedback-regulated Disks

Ali¹,

Obreschkow²,

Wang³

et al. 2019

ApJ

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“…with power-law index ω. Observations and theory typically find values of β ≈ −4.. − 3 (Oey et al 2003, Guszejnov & Hopkins 2016 and ω ≈ 2.7..3 (Wisnioski et al 2012, Strömgren 1939).…”

Section: Gaussian Clumps With Power-law Size Distributionmentioning

confidence: 99%

Robust Cross-correlation-based Measurement of Clump Sizes in Galaxies

Ali

Obreschkow

Fisher

et al. 2017

ApJ

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Stars form in molecular complexes that are visible as giant clouds (∼ 10 5−6 M ⊙ ) in nearby galaxies and as giant clumps (∼ 10 8−9 M ⊙ ) in galaxies at redshifts z ≈ 1−3. Theoretical inferences on the origin and evolution of these complexes often require robust measurements of their characteristic size, which is hard to measure at limited resolution and often ill-defined due to overlap and quasi-fractal substructure. We show that maximum and luminosity-weighted sizes of clumps seen in star formation maps (e.g. Hα) can be recovered statistically using the two-point correlation function (2PCF), if an approximate stellar surface density map is taken as the normalizing random field. After clarifying the link between Gaussian clumps and the 2PCF analytically, we design a method for measuring the diameters of Gaussian clumps with realistic quasi-fractal substructure. This method is tested using mock images of clumpy disk galaxies at different spatial resolutions and perturbed by Gaussian white noise. We find that the 2PCF can recover the input clump scale at ∼ 20% accuracy, as long as this scale is larger than the spatial resolution. We apply this method to the local spiral galaxy NGC 5194, as well as to three clumpy turbulent galaxies from the DYNAMO-HST sample. In both cases, our statistical Hα-clump size measurements agree with previous measurements and with the estimated Jeans lengths. However, the new measurements are free from subjective choices when fitting individual clumps.

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“…Various theoretical models have been constructed to explain this (Padoan & Nordlund 2002;Mac Low & Klessen 2004;Hennebelle & Chabrier 2008; Hopkins 2012) based on gravoturbulent fragmentation of the host cloud. Radiative stellar feedback has been invoked to explain the precise shape of the IMF, using both simulations (e.g., Bate 2009) and analytic models (e.g., Guszejnov & Hopkins 2016). Early pioneering simulations of cluster formation approached the problem of producing a well-defined IMF (e.g., Bate et al 2003;Klessen et al 2008;Offner et al 2008), but were often limited in terms of statistics or resolution.…”

Section: The Imf and Sfe Of Molecular Cloudsmentioning

confidence: 99%

Simulating star clusters across cosmic time – I. Initial mass function, star formation rates, and efficiencies

Ricotti

Geen

2019

Monthly Notices of the Royal Astronomical Society

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We present radiation-magneto-hydrodynamic simulations of star formation in selfgravitating, turbulent molecular clouds, modeling the formation of individual massive stars, including their UV radiation feedback. The set of simulations have cloud masses between m gas = 10 3 M to 3 × 10 5 M and gas densities typical of clouds in the local universe (n gas ∼ 1.8 × 10 2 cm −3 ) and 10× and 100× denser, expected to exist in high-redshift galaxies. The main results are: i) The observed Salpeter power-law slope and normalisation of the stellar initial mass function at the high-mass end can be reproduced if we assume that each star-forming gas clump (sink particle) fragments into stars producing on average a maximum stellar mass about 40% of the mass of the sink particle, while the remaining 60% is distributed into smaller mass stars. Assuming that the sinks fragment according to a power-law mass function flatter than Salpeter, with log-slope 0.8, satisfy this empirical prescription. ii) The star formation law that best describes our set of simulation is dρ * /dt ∝ ρ 1.5 gas if n gas < n cri ≈ 10 3 cm −3 , and dρ * /dt ∝ ρ 2.5 gas otherwise. The duration of the star formation episode is roughly 6 cloud's sound crossing times (with c s = 10 km/s). iii) The total star formation efficiency in the cloud is f * = 2%(m gas /10 4 M ) 0.4 (1 + n gas /n cri ) 0.91 , for gas at solar metallicity, while for metallicity Z < 0.1 Z , based on our limited sample, f * is reduced by a factor of ∼ 5. iv) The most compact and massive clouds appear to form globular cluster progenitors, in the sense that star clusters remain gravitationally bound after the gas has been expelled.

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Star formation in a turbulent framework: from giant molecular clouds to protostars

Cited by 18 publications

References 43 publications

Size Scaling of Clump Instabilities in Turbulent, Feedback-regulated Disks

Size Scaling of Clump Instabilities in Turbulent, Feedback-regulated Disks

Robust Cross-correlation-based Measurement of Clump Sizes in Galaxies

Simulating star clusters across cosmic time – I. Initial mass function, star formation rates, and efficiencies

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