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Fast and accurate approximations of gas cooling and heating functions are needed for hydrodynamic galaxy simulations. We use machine learning to analyze atomic gas cooling and heating functions computed by Cloudy in the presence of a…

Astrophysics of Galaxies · Physics 2025-06-24 David Robinson , Camille Avestruz , Nickolay Y. Gnedin

Aims: We systematically explore a plausible subset of the parameter space involving effective temperatures and metallicities of the ionizing stellar sources, the effects of the hardening of their radiation by surrounding leaky HII regions…

Astrophysics of Galaxies · Physics 2019-02-13 J. A. Weber , A. W. A. Pauldrach , T. L. Hoffmann

We use the hydrodynamic, cosmological EAGLE simulations to investigate how hot gas in haloes condenses to form and grow galaxies. We select haloes from the simulations that are actively cooling and study the temperature, distribution, and…

We argue that stochastic and resonant ion heating, often viewed as distinct processes in low-$\beta$ collisionless plasmas, are the far limits of a continuum controlled by nonlinear broadening of turbulent fluctuations, and thus by the…

Solar and Stellar Astrophysics · Physics 2025-09-03 Zade Johnston , Jonathan Squire , Romain Meyrand

On the basis of the universal gas fraction in clusters of galaxies, we estimate that the effective thermal conductivity required to balance radiative cooling in the cores, where the gas temperature is 3-10keV, is about one tenth of the…

Astrophysics · Physics 2009-11-07 A. C. Fabian , L. M. Voigt , R. G. Morris

We study hydrogen plasmas at magnetic fields B ~ 10^{12}-10^{13} Gauss, densities ~ 10^{-3}-10^3 g/cc and temperatures T ~ 10^{5.5}-10^{6.5} K, typical of photospheres of middle-aged cooling neutron stars. We construct an analytical free…

Plasma Physics · Physics 2009-10-31 A. Y. Potekhin , G. Chabrier , Yu. A. Shibanov , J. Ventura

We propose a methodology to perform a self-consistent analysis of the physical properties of the emitting gas of HII galaxies adequate to the data that can be obtained with the XXI century technology. This methodology requires the…

Using N-body/hydrodynamic simulations, the influence of non-equipartition processes on the thermal and dynamical properties of cosmological baryonic gas is investigated. We focus on a possible departure from equilibrium between electrons,…

Astrophysics · Physics 2009-11-10 S. Courty , J. -M. Alimi

The galactic gaseous halo is a gas reservoir for the interstellar medium in the galaxy disk, supplying materials for star formation. We developed a gaseous halo model connecting the galaxy disk and the gaseous halo by assuming the star…

Astrophysics of Galaxies · Physics 2018-04-04 Zhijie Qu , Joel N. Bregman

We study the components of cool and warm/hot gas in the circumgalactic medium (CGM) of simulated galaxies and address the relative production of OVI by photoionization versus collisional ionization, as a function of halo mass, redshift, and…

[Abridged] Photoionization, whether by starlight or other sources, has difficulty in accounting for the observed spectra of the optical filaments that often surround central galaxies in large clusters. Our first paper examined whether…

Cosmic gas makes up about 90% of baryonic matter in the Universe and H$_2$ is the closest molecule to star formation. In this work we study cold neutral gas and its H$_2$ component at different epochs, exploiting state-of-the-art…

Astrophysics of Galaxies · Physics 2022-01-05 Umberto Maio , Céline Péroux , Benedetta Ciardi

This work follows Lykins et al. discussion of classic plasma cooling function at low density and solar metallicity. Here we focus on how the cooling function changes over a wide range of density (n_H<10^12 cm^(-3)) and metallicity (Z<30Z…

Instrumentation and Methods for Astrophysics · Physics 2014-05-12 Ye Wang , G. J. Ferland , M. L. Lykins , R. L. Porter , P. A. M. van Hoof , R. J. R. Williams

We extend our time-dependent hydrogen ionization simulations of diffuse ionized gas to include metals important for collisional cooling and diagnostic emission lines. The combination of heating from supernovae and time-dependent collisional…

Astrophysics of Galaxies · Physics 2024-11-12 Lewis McCallum , Kenneth Wood , Robert Benjamin , Dhanesh Krishnarao , Bert Vandenbroucke

We present a suite of cosmological radiation-hydrodynamical simulations of the assembly of galaxies driving the reionization of the intergalactic medium (IGM) at z >~ 6. The simulations account for the hydrodynamical feedback from…

Cosmology and Nongalactic Astrophysics · Physics 2015-08-11 Andreas H. Pawlik , Joop Schaye , Claudio Dalla Vecchia

We present a new model to compute the luminosity of emission lines in star forming galaxies and apply this in the semi-analytical galaxy formation code GALFORM. The model combines a pre-computed grid of HII region models with an empirical…

Astrophysics of Galaxies · Physics 2022-01-11 C. M. Baugh , C. G. Lacey , V. Gonzalez-Perez , G. Manzoni

We develop a self-consistent model for the equilibrium gas temperature and size-dependent dust temperature in cold, dense pre-stellar cores, assuming an arbitrary power-law size distribution of dust grains. Compact analytical expressions…

Astrophysics of Galaxies · Physics 2019-11-06 Alexei V. Ivlev , Kedron Silsbee , Olli Sipilä , Paola Caselli

We investigate the impact of nonequilibrium ionisation (NEI) and the metagalactic radiation-field on the thermal evolution, virial shock stability, and absorption signatures of gas surrounding galaxies. Using 1D, spherically symmetric…

Astrophysics of Galaxies · Physics 2026-05-05 Itai Bromberg , Kartick C. Sarkar , Orly Gnat , Yuval Birnboim

Current models of galaxy formation lack an efficient and physically constrained mechanism to regulate star formation (SF) in low and intermediate mass galaxies. We argue that the missing ingredient could be the effect of photoionization by…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-14 Sebastiano Cantalupo

Simulations of galaxy clusters have a difficult time reproducing the radial gas-property gradients and red central galaxies observed to exist in the cores of galaxy clusters. Thermal conduction has been suggested as a mechanism that can…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-16 Britton D. Smith , Brian W. O'Shea , G. Mark Voit , David Ventimiglia , Samuel W. Skillman