Volume filling factors of the ISM phases in star forming galaxies

Avillez, Miguel A. de; Breitschwerdt, D.

doi:10.1051/0004-6361:200400025

Cited by 182 publications

(200 citation statements)

References 36 publications

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“…Furthermore, three-dimensional simulations of a region of the galactic disk by de Avillez (2000) show a filling factor for gas with T > 10 4 K of ∼0.4 in good agreement with our results. We find an increase of 0.2 in f if the energy injection by SNII is higher by a factor 4, which is comparable to the results of de Avillez & Breitschwerdt (2004).…”

Section: The Multi-phase Ismsupporting

confidence: 87%

Modelling galaxies with a 3d multi-phase ISM

Harfst

Theis

Hensler

2006

A&A

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We present a new particle code for modelling the evolution of galaxies. The code is based on a multi-phase description for the interstellar medium (ISM). We include star formation (SF), stellar feedback by massive stars and planetary nebulae, phase transitions, and interactions between gas clouds and ambient diffuse gas, namely condensation, evaporation, drag, and energy dissipation. The last is realised by radiative cooling and inelastic cloud-cloud collisions. We present new schemes for SF and stellar feedback that include a consistent calculation of the star-formation efficiency (SFE) based on ISM properties, as well as a detailed redistribution of the feedback energy into the different ISM phases. As a first test we show a model of the evolution of a present day Milky-Way-type galaxy. Though the model exhibits a quasi-stationary behaviour in global properties like mass fractions or surface densities, the evolution of the ISM is strongly variable locally depending on the local SF and stellar feedback. We start only with two distinct phases, but a three-phase ISM is formed soon and consists of cold molecular clouds, a warm gas disk, and a hot gaseous halo. Hot gas is also found in bubbles in the disk accompanied by type II supernovae explosions. The volume-filling factor of the hot gas in the disk is ∼35%. The mass spectrum of the clouds follows a power-law with an index of α ≈ −2. The star-formation rate (SFR) is ∼1.6 M yr −1 on average, decreasing slowly with time due to gas consumption. In order to maintain a constant SFR, gas replenishment, e.g. by infall, of the order 1 M yr −1 is required. Our model is in fair agreement with Kennicutt's (1998, ApJ, 498, 541) SF law including the cut-off at ∼10 M pc −2 . Models with a constant SFE, i.e. no feedback on the SF, fail to reproduce Kennicutt's law. We performed a parameter study varying the particle resolution, feedback energy, cloud radius, SF time scale, and metallicity. In most these cases the evolution of the model galaxy was not significantly different to our reference model. Increasing the feedback energy by a factor of 4−5 lowers the SF rate by ∼0.5 M yr −1 , while decreasing the metallicity by a factor of ∼100 increases the mass fraction of the hot gas from about 10% to 30%.

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Section: The Multi-phase Ismsupporting

confidence: 87%

Modelling galaxies with a 3d multi-phase ISM

Harfst

Theis

Hensler

2006

A&A

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“…Simulations of the diffuse interstellar medium (e.g., Korpi et al 1999b,a;De Avillez & Breitschwerdt 2004;Gressel et al 2008;Piontek et al 2009;Hill et al 2012a,b;Bendre et al 2015;Henley et al 2015) include a wide variety of physical processes and can be treated as physically realistic numerical experiments. The data used here are obtained from the non-ideal MHD simulations of the supernova-driven, multiphase ISM of Gent et al (2013a,b) that include dynamo action, and thus produce physically realistic magnetic fields (other such models are presented by Korpi et al 1999b,a;Gressel et al 2008;Bendre et al 2015).…”

Section: The Simulated Ismmentioning

confidence: 99%

Topological signatures of interstellar magnetic fields – I. Betti numbers and persistence diagrams

Makarenko

Shukurov

Henderson

et al. 2018

Monthly Notices of the Royal Astronomical Society

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The interstellar medium (ISM) is a magnetised system in which transonic or supersonic turbulence is driven by supernova explosions. This leads to the production of intermittent, filamentary structures in the ISM gas density, whilst the associated dynamo action also produces intermittent magnetic fields. The traditional theory of random functions, restricted to second-order statistical moments (or power spectra), does not adequately describe such systems. We apply topological data analysis (TDA), sensitive to all statistical moments and independent of the assumption of Gaussian statistics, to the gas density fluctuations in a magnetohydrodynamic (MHD) simulation of the multi-phase ISM. This simulation admits dynamo action, so produces physically realistic magnetic fields. The topology of the gas distribution, with and without magnetic fields, is quantified in terms of Betti numbers and persistence diagrams. Like the more standard correlation analysis, TDA shows that the ISM gas density is sensitive to the presence of magnetic fields. However, TDA gives us important additional information that cannot be obtained from correlation functions. In particular, the Betti numbers per correlation cell are shown to be physically informative. Magnetic fields make the ISM more homogeneous, reducing the abundance of both isolated gas clouds and cavities, with a stronger effect on the cavities. Remarkably, the modification of the gas distribution by magnetic fields is captured by the Betti numbers even in regions more than 300 pc from the midplane, where the magnetic field is weaker and correlation analysis fails to detect any signatures of magnetic effects.

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“…Numerical simulations predict that ∼65% of the ISM volume (within the disk: |z| < 250 pc) is filled with gas at temperatures between 10 3 and 10 5.5 K; in particular, the WIM (10 4 < T < 10 5.5 K) is expected to fill 25% of the disk volume, while the HIM filling factor is smaller (17%) because it escapes to the halo (de Avillez and Breitschwerdt, 2004). These predictions agree with recent observations.…”

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confidence: 85%

UV Capabilities to Probe the Formation of Planetary Systems: From the ISM to Planets

Castro

Lecavelier

D’Avillez

et al.

Fundamental Questions in Astrophysics: Guidelines for Future UV Observatories

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Planetary systems are angular momentum reservoirs generated during star formation. Solutions to three of the most important problems in contemporary astrophysics are needed to understand the entire process of planetary system formation:The physics of the ISM. Stars form from dense molecular clouds that contain ∼30% of the total interstellar medium (ISM) mass. The structure, properties and lifetimes of molecular clouds are determined by the overall dynamics and evolution of a very complex system -the ISM. Understanding the physics of the ISM is of prime importance not only for Galactic but also for extragalactic and cosmological studies. Most of the ISM volume (∼65%) is filled with diffuse gas at temperatures between 3000 and 300 000 K, representing about 50% of the ISM mass. ing star formation, the so-called accretion-outflow engine. Elementary physical considerations show that, to be efficient, the acceleration region for the outflows must be located close to the star (within 1 AU) where the gravitational field is strong. According to recent numerical simulations, this is also the region where terrestrial planets could form after 1 Myr. One should keep in mind that today the only evidence for life in the Universe comes from a planet located in this inner disk region (at 1 AU) from its parent star. The temperature of the accretion-outflow engine is between 3000 and 10 7 K. After 1 Myr, during the classical T Tauri stage, extinction is small and the engine becomes naked and can be observed at ultraviolet wavelengths. The physics of planet formation. Observations of volatiles released by dust, planetesimals and comets provide an extremely powerful tool for determining the relative abundances of the vaporizing species and for studying the photochemical and physical processes acting in the inner parts of young planetary systems. This region is illuminated by the strong UV radiation field produced by the star and the accretion-outflow engine. Absorption spectroscopy provides the most sensitive tool for determining the properties of the circumstellar gas as well as the characteristics of the atmospheres of the inner planets transiting the stellar disk. UV radiation also pumps the electronic transitions of the most abundant molecules (H 2 , CO, etc.) that are observed in the UV.Here we argue that access to the UV spectral range is essential for making progress in this field, since the resonance lines of the most abundant atoms and ions at temperatures between 3000 and 300 000 K, together with the electronic transitions of the most abundant molecules (H 2 , CO, OH, CS, Springer 34 Astrophys Space Sci (2006) 303:33-52 S 2 , CO + 2 , C 2 , O 2 , O 3 , etc.) are at UV wavelengths. A powerful UV-optical instrument would provide an efficient mean for measuring the abundance of ozone in the atmosphere of the thousands of transiting planets expected to be detected by the next space missions (GAIA, Corot, Kepler, etc.). Thus, a follow-up UV mission would be optimal for identifying Earth-like candidates.

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Volume filling factors of the ISM phases in star forming galaxies

Cited by 182 publications

References 36 publications

Modelling galaxies with a 3d multi-phase ISM

Modelling galaxies with a 3d multi-phase ISM

Topological signatures of interstellar magnetic fields – I. Betti numbers and persistence diagrams

UV Capabilities to Probe the Formation of Planetary Systems: From the ISM to Planets

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