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Molecular hydrogen (H$_2$) formation and dissociation are key processes that drive the gas lifecycle in galaxies. Using the SImulating the LifeCycle of Molecular Clouds (SILCC) zoom-in simulation suite, we explore the utility of future…

Motivated by the observed connection between molecular hydrogen (H2) and star formation, we present a method for tracking the non-equilibrium abundance and cooling processes of H2 and H2-based star formation in Smoothed Particle…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-05 Charlotte Christensen , Thomas Quinn , Fabio Governato , Adrienne Stilp , Sijing Shen , James Wadsley

Context. A statistically significant sampling of H2 rotational excitation in the diffuse interstellar medium (ISM) is essential to identifying its excitation mechanisms and assessing the importance of H2 in the cooling of the gas and the…

Astrophysics of Galaxies · Physics 2026-04-10 E. Nigou , B. Godard , P. Guillard , G. Pineau Des Forêts , M A Miville-Deschênes , P. Lesaffre

{It is well established that the atomic interstellar hydrogen is filling the galaxies and constitutes the building blocks of molecular clouds.} {To understand the formation and the evolution of molecular clouds, it is necessary to…

Astrophysics of Galaxies · Physics 2015-05-14 E. Audit , P. Hennebelle

The most usual tracer of molecular gas is line emission from CO. However, the reliability of that tracer has long been questioned in environments different from the Milky Way. We study the relationship between H2 and CO abundances using a…

Astrophysics of Galaxies · Physics 2015-05-18 S. C. O. Glover , M. -M. Mac Low

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 and…

Solar and Stellar Astrophysics · Physics 2015-05-13 S. C. O. Glover , C. Federrath , M. -M. Mac Low , R. S. Klessen

We report the results of initial FUSE observations of molecular hydrogen (H2) in translucent clouds. These clouds have greater optical depth than any of the diffuse clouds previously observed for far-UV H2 absorption, and provide new…

We introduce a sub-grid model for the non-equilibrium abundance of molecular hydrogen in cosmological simulations of galaxy formation. We improve upon previous work by accounting for the unresolved structure of molecular clouds in a…

Astrophysics of Galaxies · Physics 2015-06-19 Matteo Tomassetti , Cristiano Porciani , Emilio Romano-Diaz , Aaron D. Ludlow

We investigate the physical properties of molecular hydrogen (H2) in isolated and interacting disk galaxies with different masses and Hubble types by using chemodynamical simulations with H2 formation on dust grains and dust growth and…

Astrophysics of Galaxies · Physics 2017-03-08 Kenji Bekki

We examine the triggering process of molecular cloud formation around diffuse HII regions. We calculate the time evolution of the shell as well as of the HII region in a two-phase neutral medium, solving the UV and FUV radiative transfer,…

Astrophysics · Physics 2011-02-11 Takashi Hosokawa , Shu-ichiro Inutsuka

We report JWST MIRI/MRS observations of the H2 S(1) 17.04 micron transition in two regions in the boundary of the Taurus Molecular Cloud. The two regions, denoted Edge (near the relatively sharp boundary of the 13CO J=1-0 emission) and Peak…

Astrophysics of Galaxies · Physics 2025-04-30 Paul F. Goldsmith , Shengzhe Wang , Xin Wang , Raphael Skalidis , Gary A. Fuller , Di Li , Chao-Weo Tsai , Lile Wang , Donghui Quan

Molecular hydrogen is the most abundant molecule in the Universe. It is thought that a large portion of H2 forms by association of hydrogen atoms to polycyclic aromatic hydrocarbons (PAHs). We model the influence of PAHs on total H2…

Astrophysics of Galaxies · Physics 2015-07-01 Leon Boschman , Stéphanie Cazaux , Marco Spaans , Ronnie Hoekstra , Thomas Schlathölter

In recent decades, significant attention has been dedicated to analytical and observational studies of the atomic hydrogen (HI) to molecular hydrogen (H2) transition in the interstellar medium. We focussed on the Draco diffuse cloud to gain…

We present synthetic Hi and CO observations of a simulation of decaying turbulence in the thermally bistable neutral medium. We first present the simulation, with clouds initially consisting of clustered clumps. Self-gravity causes these…

Astrophysics of Galaxies · Physics 2015-08-06 Jonathan S. Heiner , Enrique Vázquez-Semadeni , Javier Ballesteros-Paredes

After the recombination of Hydrogen, primordial molecules such as H_2, $HD$ can be formed.The formation of structures in the post-recombination gaseous medium is commonly explained by primordial density fluctuations. In a self-gravitating…

Astrophysics · Physics 2007-05-23 D. Puy , M. Signore

{It has recently been proposed that giant molecular complexes form at the sites where streams of diffuse warm atomic gas collide at transonic velocities.} {We study the global statistics of molecular clouds formed by large scale colliding…

Astrophysics · Physics 2009-11-13 P. Hennebelle , R. Banerjee , E. Vazquez-Semadeni , R. Klessen , E. Audit

Observations of spiral galaxies show a strong linear correlation between the ratio of molecular to atomic hydrogen surface density R_mol and midplane pressure. To explain this, we simulate three-dimensional, magnetized turbulence, including…

Astrophysics of Galaxies · Physics 2015-05-20 Mordecai-Mark Mac Low , Simon C. O. Glover

ABRIDGED: Context: HI and CO large scale surveys of the Milky Way trace the diffuse atomic clouds and the dense shielded regions of molecular hydrogen clouds. However, until recently, we have not had spectrally resolved C+ surveys to…

Astrophysics of Galaxies · Physics 2015-06-18 W. D. Langer , T. Velusamy , J. L. Pineda , K. Willacy , P. F. Goldsmith

We have developed a model for molecular hydrogen formation under astrophysically relevant conditions. This model takes fully into account the presence of both physisorbed and chemisorbed sites on the surface, allows quantum mechanical…

Astrophysics · Physics 2009-11-07 S. Cazaux , A. G. G. M. Tielens

Molecular hydrogen (H2) is the main constituent of the gas in the planet-forming disks that surround many PMS stars. H2 can be incorporated in the atmosphere of the giant planets. HD has been detected in a few disks and can be considered…

Astrophysics of Galaxies · Physics 2018-12-18 W. F. Thi , S. Hocuk , I. Kamp , P. Woitke , Ch. Rab , S. Cazaux , P. Caselli