Hydrodynamical simulations of Galactic fountains - II. Evolution of multiple fountains

Melioli, C.; Brighenti, Fabrizio; D’Ercole, A.; Pino, E. M. de Gouveia Dal

doi:10.1111/j.1365-2966.2009.14725.x

Cited by 68 publications

(77 citation statements)

References 44 publications

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“…This result is consistent with the works of Bregman (1980), Fraternali & Binney (2008) and Melioli et al (2008). Melioli et al (2009) presented results for a multiple fountain model produced by randomly clustered explosions of SNe originating in stellar associations spread over a disk area of 8 kpc 2 . As in the case of a single fountain, the spreading of the SN ejecta back into the disk is not very large.…”

Section: Introductionsupporting

confidence: 80%

Effects of galactic fountains and delayed mixing in the chemical evolution of the Milky Way

Spitoni¹,

Matteuccí

Recchi

et al. 2009

A&A

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Context. The majority of galactic chemical evolution models assumes the instantaneous mixing approximation (IMA). This assumption is probably not realistic, as indicated by the existence of chemical inhomogeneities, although current chemical evolution models of the Milky Way can reproduce the majority of the observational constraints under the IMA. Aims. The aim of this paper is to test whether relaxing this approximation in a detailed chemical evolution model can improve or worsen the agreement with observations. To do that, we investigated two possible causes for relaxing of the instantaneous mixing: i) the "galactic fountain time delay effect" and ii) the "metal cooling time delay effect". Methods. We considered various galactic fountain time delays for the chemical enrichment from massive stars. We then tested a time delay in the enrichment from stars of all masses due to gas cooling in the range 0.5-1 Gyr. Results. We found that the effect of galactic fountains is negligible if an average time delay of 0.1 Gyr, as suggested in a previous paper, is assumed. Longer time delays produce differences in the results but they are not realistic. We also found that the O abundance gradient in the disk is not affected by galactic fountains. The metal cooling time delays produce strong effects on the evolution of the chemical abundances only if we adopt stellar yields depending on metallicity. If, instead, the yields computed for the solar chemical composition are adopted, negligible effects are produced, as in the case of the galactic fountain delay. Conclusions. The relaxation of the IMA by means of the galactic fountain model, where the delay is considered only for massive stars and only in the disk, does not affect the chemical evolution results. The combination of metal dependent yields and time delay in the chemical enrichment from all stars starting from the halo phase, instead, produces results at variance with observations.

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Section: Introductionsupporting

confidence: 80%

Effects of galactic fountains and delayed mixing in the chemical evolution of the Milky Way

Spitoni¹,

Matteuccí

Recchi

et al. 2009

A&A

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“…Unlike previous work studying supernova-driven superbubbles in three dimensions (Melioli et al 2008(Melioli et al , 2009, in this work we have not taken into account galactic shear or density stratifi- cation, ingredients that these authors have shown to be important in the evolution of the superbubbles as for the study of the overall dynamics of the ISM gas. The simulations presented here rather focus on the study of much smaller spatial and temporal scales.…”

Section: Summary and Discussionmentioning

confidence: 98%

Formation of Cold Filamentary Structure From Wind-Blown Superbubbles

Ntormousi¹,

Burkert²,

Fierlinger³

et al. 2011

ApJ

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The expansion and collision of two wind-blown superbubbles is investigated numerically. Our models go beyond previous simulations of molecular cloud formation from converging gas flows by exploring this process with realistic flow parameters, sizes, and timescales. The superbubbles are blown by time-dependent winds and supernova explosions, calculated from population synthesis models. They expand into a uniform or turbulent diffuse medium. We find that dense, cold gas clumps and filaments form naturally in the compressed collision zone of the two superbubbles. Their shapes resemble the elongated, irregular structure of observed cold, molecular gas filaments, and clumps. At the end of the simulations, between 65% and 80% of the total gas mass in our simulation box is contained in these structures. The clumps are found in a variety of physical states, ranging from pressure equilibrium with the surrounding medium to highly underpressured clumps with large irregular internal motions and structures which are rotationally supported.

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“…In particular, galactic fountains should not affect the outer disk much, because they deliver the ejected material close to the radius where they originate. They are only important for the inner, star-forming parts of the disk (Melioli et al 2008(Melioli et al , 2009). …”

Section: Further Discussionmentioning

confidence: 99%

Accretion-driven turbulence as universal process: galaxies, molecular clouds, and protostellar disks

Klessen¹,

Hennebelle²

2010

A&A

322

353

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Context. Even though turbulent motions are found everywhere in astrophysical systems, the origin of this turbulence is poorly understood. When cosmic structures form, they grow in mass via accretion from their surrounding environment. Aims. We propose that accretion is able to drive internal turbulent motions in a wide range of astrophysical objects and study this process in the case of galaxies, molecular clouds, and protoplanetary disks. Methods. We use a combination of numerical simulations and analytical arguments to predict the level of turbulence as a function of the accretion rate, the dissipation scale, and the density contrast, and compare our models with observational data. Results. We find that in Milky Way type galaxies the observed level of turbulence in the interstellar medium can be explained by accretion, provided that the galaxies gain mass at a rate comparable to the rate at which they form stars. This process is particularly relevant in the extended outer disks beyond the star-forming radius. For it to drive turbulence in dwarf galaxies, the accretion rate needs to exceed the star formation rate by a large factor, so we expect other sources to dominate. We also calculate the rate at which molecular clouds grow in mass when they build up from the atomic component of the galactic gas and find that their internal turbulence is likely to be driven by accretion as well. It is the very process of cloud formation that excites turbulent motions on small scales by establishing the turbulent cascade. In the case of T Tauri disks, we show that accretion can drive subsonic turbulence if the rate at which gas falls onto the disk is comparable to the rate at which disk material accretes onto the central star. This also explains the observed relation of accretion rate and stellar mass,Ṁ ∝ M 1.8 . The efficiency required to convert infall motion into turbulence is a few percent in all three cases. Conclusions. We conclude that accretion-driven turbulence is a universal concept with far-reaching implications for a wide range of astrophysical objects.

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Hydrodynamical simulations of Galactic fountains - II. Evolution of multiple fountains

Cited by 68 publications

References 44 publications

Effects of galactic fountains and delayed mixing in the chemical evolution of the Milky Way

Effects of galactic fountains and delayed mixing in the chemical evolution of the Milky Way

Formation of Cold Filamentary Structure From Wind-Blown Superbubbles

Accretion-driven turbulence as universal process: galaxies, molecular clouds, and protostellar disks

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