Feedback From Massive Stars and Gas Expulsion From Proto-Globular Clusters

Calura, F.; Few, C. G.; Romano, D.; D’Ercole, A.

doi:10.1088/2041-8205/814/1/l14

Cited by 75 publications

(95 citation statements)

References 53 publications

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“…Second, a steady, moderately massloaded wind (e.g., Palouš et al 2013;Calura et al 2015) may remove gas over timescales that are long compared to the crossing time, which is probably what occurs in galactic winds (e.g., Strickland & Heckman 2009;von Glasow et al 2013). In this case, the change in gravitational potential is comparatively slow, such that the effect on the stellar kinematics is moderate, and the fraction of stars lost is small (Baumgardt & Kroupa 2007).…”

Section: Methodsmentioning

confidence: 99%

“…This is again a factor that makes it easier for gas expulsion to occur in our simple models, where energy input effectively happens at the cluster centre. Calura et al (2015) simulate an embedded star cluster with compactness index C 5 = 0.85 and a metallicity of [Fe/H] = −1.3. For these parameters, our simple model predicts a minimum local star formation efficiency for gas expulsion on the crossing timescale of 0.61 in the wind phase, and, respectively 0.41 in the supernova phase.…”

Section: Accuracy Of the Methodsmentioning

confidence: 99%

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Gas expulsion in massive star clusters?

Krause

Charbonnel

Bastian

et al. 2016

A&A

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Context. Gas expulsion is a central concept in some of the models for multiple populations and the light-element anti-correlations in globular clusters. If the star formation efficiency was around 30 per cent and the gas expulsion happened on the crossing timescale, this process could preferentially expel stars born with the chemical composition of the proto-cluster gas, while stars with special composition born in the centre would remain bound. Recently, a sample of extragalactic, gas-free, young massive clusters has been identified that has the potential to test the conditions for gas expulsion. Aims. We investigate the conditions required for residual gas expulsion on the crossing timescale. We consider a standard initial mass function and different models for the energy production in the cluster: metallicity-dependent stellar winds, radiation, supernovae and more energetic events, such as hypernovae, which are related to gamma ray bursts. The latter may be more energetic than supernovae by up to two orders of magnitude. Methods. We computed a large number of thin-shell models for the gas dynamics, and calculated whether the Rayleigh-Taylor instability is able to disrupt the shell before it reaches the escape speed. Results. We show that the success of gas expulsion depends on the compactness index of a star cluster C 5 ≡ (M * /10 5 M )/(r h /pc), with initial stellar mass M * and half-mass radius r h . For given C 5 , a certain critical, local star formation efficiency is required to remove the rest of the gas. Common stellar feedback processes may not lead to gas expulsion with significant loss of stars above C 5 ≈ 1. Considering pulsar winds and hypernovae, the limit increases to C 5 ≈ 30. If successful, gas expulsion generally takes place on the crossing timescale. Some observed young massive clusters have 1 < C 5 < 10 and are gas-free at ≈10 Myr. This suggests that gas expulsion does not affect their stellar mass significantly, unless powerful pulsar winds and hypernovae are common in such objects. By comparison to observations, we show that C 5 is a better predictor for the expression of multiple populations than stellar mass. The best separation between star clusters with and without multiple populations is achieved by a stellar winds-based gas expulsion model, where gas expulsion would occur exclusively in star clusters without multiple populations. Single and multiple population clusters also have little overlap in metallicity and age. Conclusions. Globular clusters should initially have C 5 100, if the gas expulsion paradigm was correct. Early gas expulsion, which is suggested by the young massive cluster observations, hence would require special circumstances, and is excluded for several objects. Most likely, the stellar masses did not change significantly at the removal of the primordial gas. Instead, the predictive power of the C 5 index for the expression of multiple populations is consistent with the idea that gas expulsion may prevent the expression of multiple populations. On this bas...

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Section: Methodsmentioning

confidence: 99%

Section: Accuracy Of the Methodsmentioning

confidence: 99%

Gas expulsion in massive star clusters?

Krause

Charbonnel

Bastian

et al. 2016

A&A

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“…These assumptions ensure a significant mass loss of FG stars due to the external potential. If the energy injected by the FG stellar winds and SNe is sufficient to expel the SN ejecta and the residual gas (Calura et al 2015), the stellar FG can expand beyond its tidal limit in response to this substantial gas loss and be prone to efficient stellar mass loss due to the external field (D'Ercole et al 2008). Clearly, the efficiency of this mechanism is sensitive to the parameters regulating the initial FG distribution, as more concentrated stellar distributions will give place to smaller amounts of mass lost via tidal stripping (e.g., Vesperini & Heggie 1997).…”

Section: Proto-globular Clustersmentioning

confidence: 99%

“…As recent hydrodynamical simulations of proto-GCs have shown (Calura et al 2015), the feedback of the stellar winds and SNe belonging to the FG can produce large and elongated hot cavities along which their interstellar gas is able to escape. In principle, these channels may also represent viable escape routes for ionizing photons.…”

Section: Dynamical Mass Of Id11mentioning

confidence: 99%

Paving the way for the JWST: witnessing globular cluster formation at z > 3

Vanzella¹,

Calura²,

Meneghetti³

et al. 2017

Monthly Notices of the Royal Astronomical Society

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215

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We report on five compact, extremely young (< 10 Myr) and blue (β U V < −2.5, F λ = λ β ) objects observed with VLT/MUSE at redshift 3.1169, 3.235, in addition to three objects at z = 6.145. These sources are magnified by the Hubble Frontier Field galaxy clusters MACS J0416 and AS1063. Their de-lensed half light radii (R e ) are between 16 to 140 pc, the stellar masses are 1 − 20 × 10 6 M , the magnitudes are m U V = 28.8 − 31.4 (−17 < M U V < −15) and specific star formation rates can be as large as ∼ 800 Gyr −1 . Multiple images of these systems are widely separated in the sky (up to 50 ) and individually magnified by factors 3-40. Remarkably, the inferred physical properties of two objects are similar to those expected in some globular cluster formation scenarios, representing the best candidate proto-globular clusters (proto-GC) discovered so far. Rest-frame optical high dispersion spectroscopy of one of them at z = 3.1169 yields a velocity dispersion σ v 20 km s −1 , implying a dynamical mass dominated by the stellar mass. Another object at z = 6.145, with de-lensed31.4), shows a stellar mass and a star-formation rate surface density consistent with the values expected from popular GC formation scenarios. An additional star-forming region at z = 6.145, with de-lensed m U V 32, a stellar mass of 0.5 ×10 6 M and a star formation rate of 0.06 M yr −1 is also identified. These objects currently represent the faintest spectroscopically confirmed star-forming systems at z > 3, elusive even in the deepest blank fields. We discuss how proto-GCs might contribute to the ionization budget of the universe and augment Lyα visibility during reionization. This work underlines the crucial role of JWST in characterizing the restframe optical and near-infrared properties of such low-luminosity high−z objects.

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“…The simulation was performed using a customized version of the RAMSES code (Teyssier 2002) as described by Calura et al (2015). The initial conditions are represented by a uniform and homogeneous distribution of gas characterized by a density of 10 −28 g cm −3 and temperature 10 4 K (see Section 4.4).…”

Section: Energy-driven Casementioning

confidence: 99%

Exponentially growing bubbles around early supermassive black holes

Gilli¹,

Calura²,

D’Ercole³

et al. 2017

A&A

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We address the as yet unexplored issue of outflows induced by exponentially growing power sources, focusing on early supermassive black holes (BHs). We assumed that these objects grow to 10 9 M by z=6 by Eddington-limited accretion and convert 5% of their bolometric output into a wind. We first considered the case of energy-driven and momentum-driven outflows expanding in a region where the gas and total mass densities are uniform and equal to the average values in the Universe at z > 6. We derived analytic solutions for the evolution of the outflow: for an exponentially growing power with e-folding time t S al , we find that the late time expansion of the outflow radius is also exponential, with e-folding time of 5t S al and 4t S al in the energy-driven and momentum-driven limit, respectively. We then considered energy-driven outflows produced by quasi-stellar objects (QSOs) at the centre of early dark matter halos of different masses and powered by BHs growing from different seeds. We followed the evolution of the source power and of the gas and dark matter density profiles in the halos from the beginning of the accretion until z = 6. The final bubble radius and velocity do not depend on the seed BH mass, but are instead smaller for larger halo masses. At z=6, bubble radii in the range 50-180 kpc and velocities in the range 400-1000 km s −1 are expected for QSOs hosted by halos in the mass range 3 × 10 11 − 10 13 M . These radius and velocity scales compare well with those measured for the outflowing gas in the z=6.4 QSO SDSS J1148+5251. By the time the QSO is observed, we found that the total thermal energy injected within the bubble in the case of an energy-driven outflow is E th ∼ 5 × 10 60 erg. This is in excellent agreement with the value of E th = (6.2 ± 1.7) × 10 60 erg measured through the detection of the thermal Sunyaev-Zeldovich effect around a large population of luminous QSOs at lower redshifts. This suggests that QSO outflows are closer to the energy-driven limit than to the momentum-driven limit. We investigated the stability of the expanding gas shell in the case of an energy-driven supersonic outflow propagating within a dark matter halo with M h = 3 × 10 11 M at z=6. We found that the shell is Rayleigh-Taylor unstable already at early times and, by means of a simple model, we investigated the fate of the fragments detaching from the shell. We found that these fragments should rapidly evaporate because of the extremely high temperature of the hot gas bubble if this does not cool. Since the only effective cooling mechanism for such a gas is inverse Compton by the cosmic microwave background (CMB) photons (IC-CMB), which is important only at z ≥ 6, we speculate that such shell fragments may be observed only around high-z QSOs, where IC-CMB cooling of the bubble gas can prevent their evaporation.

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Feedback From Massive Stars and Gas Expulsion From Proto-Globular Clusters

Cited by 75 publications

References 53 publications

Gas expulsion in massive star clusters?

Gas expulsion in massive star clusters?

Paving the way for the JWST: witnessing globular cluster formation at z > 3

Exponentially growing bubbles around early supermassive black holes

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