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Related papers: Diffuse Molecular Cloud Densities from UV Measurem…

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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…

Astrophysics of Galaxies · Physics 2026-01-08 Yuto Komichi , Yuri Aikawa , Kazunari Iwasaki , Kenji Furuya

Ultraviolet (UV) absorption cross sections are an essential ingredient of photochemical atmosphere models. Exoplanet searches have unveiled a large population of short-period objects with hot atmospheres, very different from what we find in…

Most exoplanets detected so far have atmospheric T significantly higher than 300K. Often close to their star, they receive an intense UV photons flux that triggers important photodissociation processes. The T dependency of VUV absorption…

We present the first numerical simulations that self-consistently follow the formation of dense molecular clouds in colliding flows. Our calculations include a time-dependent model for the H2 and CO chemistry that runs alongside a detailed…

Astrophysics of Galaxies · Physics 2015-06-04 Paul C. Clark , Simon C. O. Glover , Ralf S. Klessen , Ian A. Bonnell

We investigate the correlation between OH and H2 column densities in diffuse Galactic clouds, in order to identify potential molecular tracers of interstellar H2. For this, we analyse near-UV spectra extracted from the ESO/VLT archives…

Astrophysics of Galaxies · Physics 2023-06-09 Katherine Rawlins , Bhaswati Mookerjea

Water (H2O) ice is an important solid constituent of many astrophysical environments. To comprehend the role of such ices in the chemistry and evolution of dense molecular clouds and comets, it is necessary to understand the freeze-out,…

Relating the observed CO emission from giant molecular clouds (GMCs) to the underlying H2 column density is a long-standing problem in astrophysics. While the Galactic CO-H2 conversion factor (Xco) appears to be reasonably constant,…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-27 Desika Narayanan , Mark Krumholz , Eve C. Ostriker , Lars Hernquist

Carbon-bearing molecules, particularly CO, have been widely used as tracers of molecular gas in the interstellar medium (ISM). In this work, we aim to study the properties of molecules in diffuse, cold environments, where CO tends to be…

The diffuse interstellar medium is dynamic, and its chemistry and evolution is determined by shock fronts as well as photodissociation. Shocks are implied by the supersonic motions and velocity dispersion often statistically called…

Astrophysics of Galaxies · Physics 2021-03-17 William T. Reach , Carl Heiles

We recently reported a population of protostellar candidates in the 20 km s$^{-1}$ cloud in the Central Molecular Zone of the Milky Way, traced by H$_2$O masers in gravitationally bound dense cores. In this paper, we report…

Context. Molecular Clouds (MCs) are the place where stars are formed and their feedback starts to take place, regulating the evolution of galaxies. Therefore, MCs represent the critical scale at which to study how ultra-violet (UV) photons…

Astrophysics of Galaxies · Physics 2025-03-12 Fabio Di Mascia , Andrea Pallottini , Laura Sommovigo , Davide Decataldo

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 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

We present the detection of carbon monoxide molecules (CO) at z=1.6408 towards the quasar SDSSJ160457.50+220300.5 using the VLT Ultraviolet and Visual Echelle Spectrograph. CO absorption is detected in at least two components in the first…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-13 P. Noterdaeme , C. Ledoux , R. Srianand , P. Petitjean , S. Lopez

Cornerstone molecules (CO, H_2CO, CH_3OH, HCN, HNC, CN, CS, SO) were observed toward seven sub-millimeter bright sources in the Orion molecular cloud in order to quantify the range of conditions for which individual molecular line tracers…

Astrophysics · Physics 2009-11-10 Doug Johnstone , Annemieke M. S. Boonman , Ewine F. van Dishoeck

We describe a search for molecular absorption at millimetre wavelengths associated with dusty molecular tori in active galactic nuclei (AGN). The sample observed consists of 11 flat-spectrum radio sources known to have red optical to…

Astrophysics · Physics 2016-08-30 M. Drinkwater , F. Combes , T. Wiklind

Using UV spectra obtained with FUSE, HST, and/or IUE, we determine interstellar column densities of 12CO, 13CO, and/or C_2 for ten Galactic sight lines with 0.37<E(B-V)<0.72. The N(CO)/N(H_2) ratio varies over a factor of 100 in this…

Astrophysics · Physics 2009-05-29 P. Sonnentrucker , D. E. Welty , J. A. Thorburn , D. G. York

We examine the formation of molecular gas behind shocks in atomic gas using a chemical/dynamical model, particular emphasis is given to constraints the chemistry places on the dynamical evolution. The most important result of this study is…

We present ISO observations of several H2 pure-rotational lines (from S(0) to S(5)) towards a sample of 16 molecular clouds distributed along the central ~ 500 pc of the Galaxy. We also present C18O and 13CO J=1->0 and J=2->1 observations…

Experimental measurements and theoretical calculations of state-to-state rate coefficients for rotational energy transfer of CO in collision with H$_2$ are reported at the very low temperatures prevailing in dense interstellar clouds (5 -…