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Molecular clouds are essentially made up of atomic and molecular hydrogen, which in spite of being the simplest molecule in the ISM plays a key role in the chemical evolution of molecular clouds. Since its formation time is very long, the…

The recombination of hydrogen in the interstellar medium, taking place on surfaces of microscopic dust grains, is an essential process in the evolution of chemical complexity in interstellar clouds. The H_2 formation process has been…

Condensed Matter · Physics 2009-11-07 Ofer Biham , Azi Lipshtat

Physical conditions within DLAs can reveal the star formation history, determine the chemical composition of the associated ISM, and hence document the first steps in the formation of present day galaxies. Here we present calculations that…

Astrophysics · Physics 2009-09-29 Raghunathan Srianand , Gargi Shaw , Gary Ferland , Patrick Petitjean , Cedric Ledoux

Here we present a study of radial chemical mixing in non-rotating massive main-sequence stars driven by internal gravity waves (IGWs), based on multi-dimensional hydrodynamical simulations with the fully compressible code MUSIC. We examine…

Solar and Stellar Astrophysics · Physics 2025-01-08 Jack Morton , Thomas Guillet , Isabelle Baraffe , Adrien Morison , Arthur Le Saux , Dimitar Vlaykov , Tom Goffrey , Jane Pratt

Molecular hydrogen is the most abundant molecule in the universe. It is the first one to form and survive photo-dissociation in tenuous environments. Its formation involves catalytic reactions on the surface of interstellar grains. The…

Molecular gas is the key ingredient of the star formation cycle, and tracing its dependencies on other galaxy properties is essential for understanding galaxy evolution. In this work, we explore the relation between the different phases of…

Astrophysics of Galaxies · Physics 2025-07-23 Francesco Salvestrini , Simone Bianchi , Edvige Corbelli

We examine the abundance of molecular hydrogen (H2) in the spectra of gamma ray burst afterglows (GRBs). In nearby galaxies H2 traces the cold neutral medium (CNM) and dense molecular star-forming interstellar gas. Though H2 is detected in…

We performed high-resolution, 3D MHD simulations and we compared to observations of translucent molecular clouds. We show that the observed populations of rotational levels of H2 can arise as a consequence of the multi-phase structure of…

Instrumentation and Methods for Astrophysics · Physics 2016-06-01 V. Valdivia , P. Hennebelle , M. Gerin , P. Lesaffre

Statistical properties of the pair dispersion of Lagrangian particles (tracers) in incompressible turbulent flows provide insights into transport and mixing. We explore the same in transonic to supersonic compressible turbulence of an…

Fluid Dynamics · Physics 2026-02-13 Sadhitro De , Dhrubaditya Mitra , Rahul Pandit

We study the Lagrangian velocity and acceleration statistics of light particles (micro-bubbles in water) in homogeneous isotropic turbulence. Micro-bubbles with a diameter of 340 microns and Stokes number from 0.02 to 0.09 are dispersed in…

Fluid Dynamics · Physics 2012-05-30 Julian Martinez Mercado , Vivek N. Prakash , Yoshiyuki Tagawa , Chao Sun , Detlef Lohse

(Abridged) We explore the chemistry of the most abundant C, O, S, and N bearing species in molecular clouds, in the context of the IRAM 30 m Large Programme Gas phase Elemental abundances in Molecular Clouds (GEMS). In this work, we aim to…

Supersonic turbulence is an essential element in understanding how structure within interstellar gas is created and shaped. In the context of star formation, many computational studies show that the mass spectrum of density and velocity…

Astrophysics of Galaxies · Physics 2014-03-05 Ralph E. Pudritz , N. K. -R. Kevlahan

We combine Herschel observations of a total of 12 sources to construct the most uniform survey of HF and H2O in our Galactic disk. Both molecules are detected in absorption along all sight lines. The high spectral resolution of the…

Astrophysics of Galaxies · Physics 2015-06-11 P. Sonnentrucker , M. Wolfire , D. A. Neufeld , N. Flagey , M. Gerin , P. Goldsmith , D. Lis , R. Monje

Macroturbulence, introduced as a fudge to reproduce the width and shape of stellar absorption lines, reflects gas motions in stellar atmospheres. While in cool stars, it is thought to be caused by convection zones immediately beneath the…

Solar and Stellar Astrophysics · Physics 2016-09-07 Luca Grassitelli , Luca Fossati , Norbert Langer , Sergio Simon-Diaz , Norberto Castro , Debashis Sanyal

The fragmentation of gas to form stars in molecular clouds is intrinsically linked to the turbulence within them. These internal motions are set at the birth of the cloud and may vary with galactic environment and as the cloud evolves. In…

Astrophysics of Galaxies · Physics 2024-07-29 Jiten Dhandha , Zoe Faes , Rowan J. Smith

We present the results from three dimensional hydrodynamical simulations of decaying high-speed turbulence in dense molecular clouds. We compare our results, which include a detailed cooling function, molecular hydrogen chemistry and a…

Astrophysics · Physics 2009-11-07 Georgi Pavlovski , Michael D. Smith , Mordecai-Mark Mac Low , Alexander Rosen

Dynamical expansion of H II regions around star clusters plays a key role in dispersing the surrounding dense gas and therefore in limiting the efficiency of star formation in molecular clouds. We use a semi-analytic method and numerical…

Astrophysics of Galaxies · Physics 2016-03-23 Jeong-Gyu Kim , Woong-Tae Kim , Eve C. Ostriker

Radiative feedback from massive stars is a key process to understand how HII regions may enhance or inhibit star formation in pillars and globules at the interface with molecular clouds. We aim to contribute to model the interactions…

Solar and Stellar Astrophysics · Physics 2015-06-03 P. Tremblin , E. Audit , V. Minier , N. Schneider

Supersonic turbulence in molecular clouds is a dominant agent that strongly affects the clouds' evolution and star formation activity. Turbulence may be initiated and maintained by a number of processes, acting at a wide range of physical…

Astrophysics of Galaxies · Physics 2014-11-20 C. M. Brunt , M. H. Heyer , M. -M. Mac Low

Understanding the molecular content of galaxies is a critical problem in star formation and galactic evolution. Here we present a new method, based on a Stromgren-type analysis, to calculate the amount of HI that surrounds a molecular cloud…

Astrophysics of Galaxies · Physics 2015-05-13 Christopher F. McKee , Mark R. Krumholz