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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 report the first ensemble results from the FUSE survey of molecular hydrogen in lines of sight with A_V $\gtrsim$ 1 mag. We have developed techniques for fitting computed profiles to the low-J lines of H2, and thus determining column…

A simple analytic model is presented to predict the near-IR H2 fluorescent line intensities emitted by diffuse interstellar clouds with a Plummer density profile. It is applicable to sightlines where (1) the column densities of H and H2…

星系天体物理 · 物理学 2024-10-15 David A. Neufeld

Molecular hydrogen being unobservable in cold molecular clouds, the column density measurements of molecular gas currently rely either on dust emission observation in the far-IR or on star counting. (Sub-)millimeter observations of numerous…

A reliable estimate of the molecular gas content in galaxies plays a crucial role in determining their dynamical and star-forming properties. However, H2, the dominant molecular species, is difficult to observe directly, particularly in the…

天体物理学 · 物理学 2008-11-26 T. A. Bell , E. Roueff , S. Viti , D. A. Williams

We investigate the chemical evolution of a forming molecular cloud behind an interstellar shock wave. We conduct three-dimensional magnetohydrodynamics simulations of the converging flow of atomic gas, including a simple chemical network…

星系天体物理 · 物理学 2026-01-08 Yuto Komichi , Yuri Aikawa , Kazunari Iwasaki , Kenji Furuya

We studied the statistical properties of the HI-to-H$_2$ transition observed in absorption in the local diffuse and multiphase ISM to identify the physical processes controlling the probability of occurrence of any line of sight. The…

We use far-UV absorption spectra obtained with FUSE towards three late B stars to study the formation and excitation of H2 in the diffuse ISM. The data interpretation relies on a model of the chemical and thermal balance in…

We revised the treatment of interstellar dust in the KOSMA-\tau\ PDR model code to achieve a consistent description of the dust-related physics in the code. The detailed knowledge of the dust properties is then used to compute the dust…

天体物理仪器与方法 · 物理学 2012-11-16 M. Röllig , R. Szczerba , V. Ossenkopf , C. Glück

We present a semi-analytical description of the relative HD/H2 abundance in the diffuse interstellar medium. We found three asymptotics of the relative HD/H$_2$ abundance for different parts of the medium and their dependence on the…

星系天体物理 · 物理学 2020-01-15 S. A. Balashev , D. N. Kosenko

We study the formation of H2 in the ISM, using a modified version of the astrophysical magnetohydrodynamical code ZEUS-MP that includes a non-equilibrium treatment of the formation and destruction of H2. We examine two different…

天体物理学 · 物理学 2008-11-26 S. C. O. Glover , M. -M. Mac Low

We investigate how the existence of hydrogen molecules on grain surfaces may affect H$_2$ formation efficiency in diffuse and translucent clouds. Hydrogen molecules are able to reduce the desorption energy of H atoms on grain surfaces in…

星系天体物理 · 物理学 2022-03-30 Gang Zhao , Qiang Chang , Xia Zhang , Donghui Quan , Yong Zhang , Xiao-Hu Li

Molecular clouds (MCs) are the birthplaces of new stars in galaxies. A key component of MCs are photodissociation regions (PDRs), where far-ultraviolet radiation plays a crucial role in determining the gas's physical and chemical state.…

H2 is the simplest and the most abundant molecule in the ISM, and its formation precedes the formation of other molecules. Understanding the dynamical influence of the environment and the interplay between the thermal processes related to…

星系天体物理 · 物理学 2016-02-24 Valeska Valdivia , Patrick Hennebelle , Maryvonne Gérin , Pierre Lesaffre

The modelling of emission spectra of molecules seen in interstellar clouds requires the knowledge of collisional rate coefficients. Among the commonly observed species, N$_2$H$^+$ is of particular interest since it was shown to be a good…

星系天体物理 · 物理学 2015-06-23 François Lique , Fabien Daniel , Laurent Pagani , Nicole Feautrier

Using archival, high-resolution far-ultraviolet HST/STIS spectra of 34 Galactic O and B stars, we measure CI column densities and compare them with measurements from the literature of CO and H_2 with regard to understanding the presence of…

星系天体物理 · 物理学 2014-11-20 Eric B. Burgh , Kevin France , Edward B. Jenkins

We present models of the evolution of the gaseous and stellar content of galaxies incorporating the formation of H_2 out of HI gas as part of such a model. We do so by formulating a subgrid model for gas clouds that uses well-known cloud…

天体物理学 · 物理学 2009-11-11 F. I. Pelupessy , P. P. Papadopoulos , P. P. van der Werf

We present results of analysis of physical conditions (number density, intensity of UV field, kinetic temperature) in the cold H$_2$-bearing interstellar medium of local and high redshift galaxies. Our measurements based on the fit to the…

星系天体物理 · 物理学 2020-10-07 V. V. Klimenko , S. A. Balashev

We have used archival FUSE data to complete a survey of interstellar HD in 41 lines of sight with a wide range of extinctions. This follow up to an earlier survey was made to further assess the utility of HD as a cosmological probe; to…

We study molecular hydrogen formation in and on solids. We construct a model with surface sites and bulk sites capable of describing (1) the motion and exchange of H and H_2 between surface and bulk, (2) the recombination of H and…

天体物理学 · 物理学 2007-05-23 Amir Levinson , David F. Chernoff , Edwin E. Salpeter
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