Interpreting the star formation efficiency of nearby molecular clouds with ionizing radiation

Geen, Sam; Soler, J. D.; Hennebelle, P.

doi:10.1093/mnras/stx1765

Cited by 74 publications

(98 citation statements)

References 71 publications

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“…This order of magnitude is in line with observations in the Galaxy (Lada & Lada 2003). It also agrees with the simulation by Geen et al (2017), labelled 'L', which has a similar initial mass and surface density, and includes ionization feedback - Geen et al (2017) found that the SFE for that cloud was closer to observations of local star-forming regions compared to denser models, where SFEs approached 100 per cent.…”

Section: Bulk Grid Propertiessupporting

confidence: 88%

Massive star feedback in clusters: variation of the FUV interstellar radiation field in time and space

Ali

Harries

2019

Monthly Notices of the Royal Astronomical Society

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We investigate radiative feedback from a 34 M star in a 10 4 M turbulent cloud using three-dimensional radiation-hydrodynamics (RHD) models. We use Monte Carlo radiative transfer to accurately compute photoionization equilibrium and radiation pressure, with multiple atomic species and silicate dust grains. We include the diffuse radiation field, dust absorption/re-emission, and scattering. The cloud is efficiently dispersed, with 75 per cent of the mass leaving the (32.3 pc) 3 grid within 4.3 Myr (1.1 t ff ). This compares to all mass exiting within 1.6 Myr (0.74 t ff ) in our previously published 10 3 M cloud. At most 20 per cent of the mass is ionized, compared to 40 per cent in the lower mass model, despite the ionized volume fraction being 80 per cent in both, implying the higher mass cloud is more resilient to feedback. The total Jeans-unstable mass increases linearly up to 1500 M before plateauing after 2 Myr, corresponding to a core formation efficiency of 15 per cent. We also measure the time-variation of the far-ultraviolet (FUV) radiation field, G 0 , impinging on other cluster members, taking into account for the first time how this changes in a dynamic cluster environment with intervening opacity sources and stellar motions. Many objects remain shielded in the first 0.5 Myr whilst the massive star is embedded, after which G 0 increases by orders of magnitude. Gas motions later on cause comparable drops which happen instantaneously and last for ∼ 1 Myr before being restored. This highly variable UV field will influence the photoevaporation of protoplanetary discs near massive stars.

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Section: Bulk Grid Propertiessupporting

confidence: 88%

Massive star feedback in clusters: variation of the FUV interstellar radiation field in time and space

Ali

Harries

2019

Monthly Notices of the Royal Astronomical Society

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“…There is no clear theoretical link between the SFE and projected column density, although Clark & Glover (2014) argue that there may be a link between the observed column density and the local density around the star. Geen et al (2017) reproduce the SFE observed by Lada et al (2010), although they find that the result is likely to be dependent on the average density of the neutral gas in the cloud. These simulations produce similar results to the simulations of Colin et al (2013).…”

Section: The Imf and Sfe Of Molecular Cloudsmentioning

confidence: 78%

“…The initial density profile is perturbed with a turbulent velocity field, analogously to the set up used in Geen et al (2017). The initial turbulence of the clouds follows a Kolmogorov power spectrum with random phases and has an amplitude such that the cloud is approximately in virial equilibrium.…”

Section: Initial Conditionsmentioning

confidence: 99%

“…For each simulation we estimate the total hydrogenionising photon emission rate at a given time as S cl (m cl ) = 8.96 × 10 46 s −1 (m cl /M ) (see Geen et al 2017), where m cl is the total mass of the sink particles. This is calculated by Monte Carlo sampling a stellar population as described in Geen et al (2016) (See Sec.…”

Section: Feedback and Properties Of Uv Sourcementioning

confidence: 99%

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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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“…Then, some fraction of cold gas can be converted into star clusters, although the conversion efficiency is not understood well (e.g., Geen et al 2017). Therefore, our results suggest that stellar distribution can sensitively depend on the metallicity of galaxies.…”

Section: Metallicity Dependencementioning

confidence: 78%

Gas clump formation via thermal instability in high-redshift dwarf galaxy mergers

Arata

Yajima

Nagamine

2018

Monthly Notices of the Royal Astronomical Society

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Star formation in high-redshift dwarf galaxies is a key to understand early galaxy evolution in the early Universe. Using the three-dimensional hydrodynamics code GIZMO, we study the formation mechanism of cold, high-density gas clouds in interacting dwarf galaxies with halo masses of ∼ 3 × 10 7 M , which are likely to be the formation sites of early star clusters. Our simulations can resolve both the structure of interstellar medium on small scales of 0.1 pc and the galactic disk simultaneously. We find that the cold gas clouds form in the post-shock region via thermal instability due to metalline cooling, when the cooling time is shorter than the galactic dynamical time. The mass function of cold clouds shows almost a power-law initially with an upper limit of thermally unstable scale. We find that some clouds merge into more massive ones with 10 4 M within ∼ 2 Myr. Only the massive cold clouds with 10 3 M can keep collapsing due to gravitational instability, resulting in the formation of star clusters. In addition, we investigate the dependence of cloud mass function on metallicity and H 2 abundance, and show that the cases with low metallicities ( 10 −2 Z ) or high H 2 abundance ( 10 −3 ) cannot form massive cold clouds with 10 3 M .

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Interpreting the star formation efficiency of nearby molecular clouds with ionizing radiation

Cited by 74 publications

References 71 publications

Massive star feedback in clusters: variation of the FUV interstellar radiation field in time and space

Massive star feedback in clusters: variation of the FUV interstellar radiation field in time and space

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

Gas clump formation via thermal instability in high-redshift dwarf galaxy mergers

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