Understanding the formation of stars in galaxies is central to much modern astrophysics. For several decades it has been thought that stellar birth primarily controlled by interplay between gravity and magnetostatic support, modulated ambipolar diffusion. Recently, however, both observational numerical work begun suggest support supersonic turbulence rather than magnetic fields controls star formation. In this review we outline a new theory relying on control turbulence. We demonstrate...

We model the effects of repeated supernova explosions from starbursts in dwarf galaxies on interstellar medium these galaxies, taking into account gravitational potential their dominant dark matter haloes. explore rates one every 30,000 yr to 3 million yr, equivalent steady mechanical luminosities L=0.1-10 x 10^38 ergs/s, occurring with gas masses M_g=10^6 - 10^9 solar masses. address detail, both analytically and numerically, following three questions: 1. When do ejecta blow out disk...

We study two limiting cases of turbulence forcing in numerical experiments: solenoidal (divergence-free) forcing, and compressive (curl-free) compare our results to observations reported the literature. solve equations hydrodynamics on grids with up 1024^3 cells for purely forcing. Eleven lower-resolution models mixtures both forcings are also analysed. find velocity dispersion--size relations consistent independent simulations, irrespective type However, yields stronger turbulent...

view Abstract Citations (622) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Superbubbles in Disk Galaxies Mac Low, Mordecai-Mark ; McCray, Richard Correlated supernovae from an OB association create a superbubble: large, thin, shell of cold gas surrounding hot pressurized interior. Because supernova blast waves usually become subsonic before reaching the walls or cooling radiatively, we may reasonably approximate energy input as continuous...

Molecular clouds have broad linewidths suggesting turbulent supersonic motions in the clouds. These are usually invoked to explain why molecular take much longer than a free-fall time form stars. It has classically been thought that hydrodynamical turbulence would dissipate its energy quickly, but introduction of strong magnetic fields could maintain these motions. In previous paper it shown, however, isothermal, compressible, MHD and decay at virtually same rate, requiring constant driving...

We compute 3D models of supersonic, sub-Alfv\'enic, and super-Alfv\'enic decaying turbulence, with an isothermal equation state appropriate for star-forming interstellar clouds molecular gas. find that in the kinetic energy decays as ${t}^{\ensuremath{-}\ensuremath{\eta}}$, $0.85<\ensuremath{\eta}<1.2$. In 1D magnetized turbulence actually faster than unmagnetized turbulence. compared different algorithms, performed resolution studies reaching ${256}^{3}$ zones or ${70}^{3}$ particles....

Chondrules are millimeter-sized spherules that dominate primitive meteorites (chondrites) originating from the asteroid belt. The incorporation of chondrules into asteroidal bodies must be an important step in planet formation, but mechanism is not understood. We show main growth asteroids can result gas drag-assisted accretion chondrules. largest planetesimals a population with characteristic radius 100 km undergo runaway within ~3 My, forming planetary embryos up to Mars's size along...

We present three-dimensional numerical simulations of particle clumping and planetesimal formation in protoplanetary disks with varying amounts solid material. As centimeter-size pebbles settle to the mid-plane, turbulence develops through vertical shearing streaming instabilities. find that when pebble-to-gas column density ratio is 0.01, corresponding roughly solar metallicity, weak, so pebble rarely exceeds gas density. Doubling leads a dramatic increase clumping, characteristic densities...

We explore what dominant physical mechanism sets the kinetic energy contained in neutral, atomic (H i) gas. Both supernova (SN) explosions and magnetorotational instability (MRI) have been proposed to drive turbulence gas disks we compare H i line widths predicted from driven by these mechanisms direct observations 11 disk galaxies. use high-quality maps of mass surface density width, obtained The Nearby Galaxy Survey. show that all sample galaxies exhibit a systematic radial decline which...

We present a hydrodynamical simulation of the turbulent, magnetized, supernova (SN)-driven interstellar medium (ISM) in stratified box that dynamically couples injection and evolution cosmic rays (CRs) self-consistent chemical composition. CRs are treated as relativistic fluid advection-diffusion approximation. The thermodynamic gas is computed using network follows abundances H+, H, H2, CO, C+, free electrons includes (self-)shielding dust. find perceptibly thicken disk with heights 90%...

Abstract The A eos project introduces a series of high-resolution cosmological simulations that model star-by-star chemical enrichment and galaxy formation in the early Universe, achieving 1 pc resolution. These capture complexities evolution within first ~300 Myr by modeling individual stars their feedback processes. By incorporating yields from stars, generates galaxies with diverse stellar abundances, linking them to hierarchical nucleosynthetic events. underscore importance abundance...

This paper describes ZEUS-MP, a multiphysics, massively parallel, message-passing implementation of the ZEUS code. ZEUS-MP differs significantly from thoroughly documented ZEUS-2D code, completely undocumented (in peer-reviewed literature) ZEUS-3D and marginally "version 1" first distributed publicly in 1999. offers an MHD algorithm that is better suited for multidimensional flows than module by virtue modifications to method characteristics scheme suggested Hawley & Stone. shown compare...

Observed molecular clouds often appear to have very low star formation efficiencies and lifetimes an order of magnitude longer than their free-fall times. Their support is attributed the random supersonic motions observed in them. We study against gravitational collapse by supersonic, gas dynamical turbulence using direct numerical simulation. Computations with two different algorithms are compared: a particle-based, Lagrangian method (SPH), grid-based, Eulerian, second-order (ZEUS). The...

We study the formation of H2 in ISM, using a modified version astrophysical magnetohydrodynamical code ZEUS-MP that includes nonequilibrium treatment and destruction H2. examine two different approximations to treat shielding against photodissociation: local approximation, which gives us solid lower bound on amount shielding, method based ray-tracing is considerably more accurate some circumstances but produces results are harder clearly interpret. In both cases, computational cost...

Identifying the processes that determine initial mass function of stars (IMF) is a fundamental problem in star formation theory. One major uncertainties exact chemical state forming gas and its influence on dynamical evolution. Most simulations clusters use an isothermal equation (EOS). However, theoretical predictions observations suggest effective polytropic exponent gamma EOS varies with density. We address these issues study effect piecewise stellar turbulent, self-gravitating molecular...

To study how supernova feedback structures the turbulent interstellar medium, we construct 3D models of vertically stratified gas stirred by discrete explosions, including vertical gravitational field and parametrized heating cooling. The reproduce many observed characteristics Galaxy such as global circulation (i.e., galactic fountain) existence cold dense clouds in disk. Global quantities model warm hot filling factors midplane, mass fraction thermally unstable gas, averaged density...

view Abstract Citations (330) References (34) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Superbubble Blowout Dynamics Mac Low, Mordecai-Mark ; McCray, Richard Norman, Michael L. Multiple supernovae and stellar winds from OB associations carve large holes filled with hot gas in the galactic disk. These superbubbles sweep up H I into cold, thin, dense shells eventually grow enough to blow completely out of When disk, they vent supernova energy corona. In...

(Abridged). In this paper, we present results from a large set of numerical simulations that demonstrate H2 formation occurs rapidly in turbulent gas. Starting with purely atomic hydrogen, quantities molecular hydrogen can be produced on timescales 1 -- 2 Myr, given velocity dispersions and magnetic field strengths consistent observations. Moreover, as our underestimate the effectiveness self-shielding dust absorption, confident fractions compute are strong lower limits true values. The...

We describe the first three-dimensional simulation of gravitational collapse a massive, rotating molecular cloud that includes heating by both non-ionizing and ionizing radiation. find as protostars gain sufficient mass to ionize accretion flow, their H II regions are initially gravitationally trapped, but soon begin rapidly fluctuate between trapped extended states, in agreement with observations. Over time, same ultracompact region can expand anisotropically, contract again, take on any...

We present results from high-resolution three-dimensional simulations of turbulent interstellar gas that self-consistently follow its coupled thermal, chemical and dynamical evolution, with a particular focus on the formation destruction H2 CO. quantify time-scales for CO in physical conditions corresponding to those found nearby giant molecular clouds, show both species form rapidly, are comparable time-scale gas. also investigate spatial distributions CO, how they relate underlying...

We compare velocity structure observed in the Polaris Flare molecular cloud at scales ranging from 0.015 pc to 20 of a suite simulations supersonic hydrodynamic and MHD turbulence computed with ZEUS code. examine different methods characterising structure, including scanning-beam method that provides an objective measurement Larson's size-linewidth relation, functions, difference probability distribution functions (PDFs), Δ-variance wavelet transform, use them models observations. The is...

We use three-dimensional hydrodynamical simulations to study the rapid infall phase of common envelope interaction a red giant branch star mass equal 0.88 \msun and companion ranging from 0.9 down 0.1 \msun. first compare results obtained using two different numerical techniques with resolutions, find overall very good agreement. then outcomes those observed systems thought have gone through envelope. The fail reproduce in sense that most donor remains bound at end final orbital separations...

Outward migration of low-mass planets has recently been shown to be a possibility in non-barotropic disks. We examine the consequences this result evolutionary models protoplanetary Planet occurs toward equilibrium radii with zero torque. These themselves migrate inwards because viscous accretion and photoevaporation. show that as surface density temperature fall planet orbital disk depletion timescales eventually become comparable, precise timing depending on mass planet. When occurs,...

Massive stars influence their surroundings through radiation, winds, and supernova explosions far out of proportion to small numbers. However, the physical processes that initiate govern birth massive remain poorly understood. Two widely discussed models are monolithic collapse molecular cloud cores competitive accretion. To learn more about star formation, we perform analyze simulations rotating, massive, including radiative heating by both non-ionizing ionizing radiation using FLASH...