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The chemical composition of the interstellar medium is determined by gas phase chemistry, assisted by grain surface reactions, and by shock chemistry. The aim of this study is to measure the abundance of the hydroxyl radical (OH) in diffuse…

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…

星系天体物理 · 物理学 2023-06-09 Katherine Rawlins , Bhaswati Mookerjea

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…

星系天体物理 · 物理学 2015-06-11 P. Sonnentrucker , M. Wolfire , D. A. Neufeld , N. Flagey , M. Gerin , P. Goldsmith , D. Lis , R. Monje

The hydroxyl radical (OH) is found in various environments within the interstellar medium (ISM) of the Milky Way and external galaxies, mostly either in diffuse interstellar clouds or in the warm, dense environments of newly formed low-mass…

Near ultraviolet observations of OH+ and OH in diffuse molecular clouds reveal a preference for different environments. The dominant absorption feature in OH+ arises from a main component seen in CH+ (that with the highest CH+/CH column…

星系天体物理 · 物理学 2015-06-18 A. J. Porras , S. R. Federman , D. E. Welty , A. M. Ritchey

In diffuse interstellar clouds the chemistry that leads to the formation of the oxygen bearing ions OH+, H2O+, and H3O+ begins with the ionization of atomic hydrogen by cosmic rays, and continues through subsequent hydrogen abstraction…

Hydroxyl ($\rm OH$) is known to form efficiently in cold gas ($T\sim 100$K) along with the molecule $\rm H_2$ and can be used as an efficient tracer of the diffuse molecular gas in the interstellar medium (ISM). Using a simple formalism…

星系天体物理 · 物理学 2021-04-28 Sergei Balashev , Neeraj Gupta , Daria Kosenko

We model the production of OH+, H2O+, and H3O+ in interstellar clouds, using a steady state photodissociation region code that treats the freeze-out of gas species, grain surface chemistry, and desorption of ices from grains. The code…

星系天体物理 · 物理学 2015-06-05 David Hollenbach , M. J. Kaufman , D. Neufeld , M. Wolfire , J. R. Goicoechea

We present models for the chemistry in gas moving towards the ionization front of an HII region. When it is far from the ionization front, the gas is highly depleted of elements more massive than helium. However, as it approaches the…

天体物理学 · 物理学 2009-11-13 S. Viti , T. W. Hartquist , P. C. Myers

The HyGAL Stratospheric Observatory for Infrared Astronomy (SOFIA) legacy program aims at characterizing the interstellar medium in the Milky Way using hydrides, [C II], and [O I] absorption lines with the 2.7 m SOFIA telescope toward…

According to traditional gas-phase chemical models, O2 should be abundant in molecular clouds, but until recently, attempts to detect interstellar O2 line emission with ground- and space-based observatories have failed. Following the…

The molecular species hydrogen peroxide, HOOH, is likely to be a key ingredient in the oxygen and water chemistry in the interstellar medium. Our aim with this investigation is to determine how abundant HOOH is in the cloud core {\rho} Oph…

星系天体物理 · 物理学 2011-06-02 P. Bergman , B. Parise , R. Liseau , B. Larsson , H. Olofsson , K. M. Menten , R. Güsten

We model the temperature and chemical structure of molecular clouds as a function of depth into the cloud, assuming a cloud of constant density n illuminated by an external FUV (6 eV < E < 13.6 eV) flux G_0 (scaling factor in multiples of…

天体物理学 · 物理学 2011-02-11 David Hollenbach , Michael J. Kaufman , Edwin A. Bergin , Gary J. Melnick

We present a systematic survey of multiple velocity-resolved H$_2$O spectra using Herschel/HIFI towards nine nearby actively star forming galaxies. The ground-state and low-excitation lines (E$_{\rm up}\,\le 130\,{\rm K}$) show profiles…

JWST gives a unique access to the physical and chemical structure of inner disks ($<10$~au), where the majority of the planets are forming. However, the interpretation of mid-infrared (mid-IR) spectra requires detailed thermo-chemical…

地球与行星天体物理 · 物理学 2024-10-30 Benoît Tabone , Ewine F. van Dishoeck , John H. Black

We report on the abundance of interstellar neutral oxygen (OI) for 26 sightlines, using data from the Far Ultraviolet Spectroscopic Explorer (FUSE), the International Spectroscopic Explorer (IUE), and the Hubble Space Telescope (HST). OI…

天体物理学 · 物理学 2009-11-10 Adam G. Jensen , Brian L. Rachford , Theodore P. Snow

Molecular oxygen has been the subject of many observational searches as chemical models predicted it to be a reservoir of oxygen. Although it has been detected in two regions of the interstellar medium, its rarity is a challenge for…

星系天体物理 · 物理学 2019-06-04 V. Wakelam , M. Ruaud , P. Gratier , I. A. Bonnell

We have conducted OH 18 cm survey toward 141 molecular clouds in various environments, including 33 optical dark clouds, 98 Planck Galactic cold clumps (PGCCs) and 10 Spitzer dark clouds with the Arecibo telescope. The deviations from local…

星系天体物理 · 物理学 2020-12-23 Ningyu Tang , Di Li , Nannan Yue , Pei Zuo , Tie Liu , Gan Luo , Longfei Chen , Sheng-Li Qin , Yuefang Wu , Carl Heiles
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