New Constraints on Diffuse Interstellar Cloud Models. The Model of the ζ Ophiuchi Cloud Revisited

Viala, Y.; Abgrall, H.; Roueff, E.

doi:10.1007/978-94-009-4774-0_38

Cited by 5 publications

(5 citation statements)

References 13 publications

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“…Although the observations reveal several interstellar components at different heliocentric velocities, the one at v ⊙ =−14.4 km s −1 contains most of the material and is referred to as the ζ Oph cloud. There have been numerous efforts to build chemical models of this cloud (Black & Dalgarno 1977; van Dishoeck & Black 1986; Viala, Roueff & Abgrall 1988). In the pioneering work of Black & Dalgarno (1977), a two‐shell model is proposed to fit the observational data: a cold and denser core surrounded by a diffuse envelope.…”

Section: Introductionmentioning

confidence: 99%

Dust-correlated cm wavelength continuum emission from translucent clouds ζ Oph and LDN 1780

Vidal

Casassus

Dickinson

et al. 2011

Monthly Notices of the Royal Astronomical Society

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The diffuse cm wave IR-correlated signal, the 'anomalous' CMB foreground, is thought to arise in the dust in cirrus clouds. We present Cosmic Background Imager (CBI) cm wave data of two translucent clouds, ζ Oph and LDN 1780 with the aim of characterizing the anomalous emission in the translucent cloud environment.In ζ Oph, the measured brightness at 31 GHz is 2.4σ higher than an extrapolation from 5-GHz measurements assuming a free-free spectrum on 8 arcmin scales. The SED of this cloud on angular scales of 1• is dominated by free-free emission in the cm range. In LDN 1780 we detected a 3σ excess in the SED on angular scales of 1• that can be fitted using a spinning dust model. In this cloud, there is a spatial correlation between the CBI data and IR images, which trace dust. The correlation is better with near-IR templates (IRAS 12 and 25 µm) than with IRAS 100 µm, which suggests a very small grain origin for the emission at 31 GHz.We calculated the 31-GHz emissivities in both clouds. They are similar and have intermediate values between that of cirrus clouds and dark clouds. Nevertheless, we found an indication of an inverse relationship between emissivity and column density, which further supports the VSGs origin for the cm emission since the proportion of big relative to small grains is smaller in diffuse clouds.

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Section: Introductionmentioning

confidence: 99%

Dust-correlated cm wavelength continuum emission from translucent clouds ζ Oph and LDN 1780

Vidal

Casassus

Dickinson

et al. 2011

Monthly Notices of the Royal Astronomical Society

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“…Viala et al (1988a) have developed a more elaborate model of diffuse clouds in the same context where the photochemical equilibrium is solved at a fixed temperature. Meanwhile, the rotational and rovibrational collisional excitation of HD by H, He and H 2 has been studied with quantal close coupling techniques and new molecular potential surfaces (Roueff & Zeippen 1999Flower & Roueff 1999).…”

Section: Introductionmentioning

confidence: 99%

D/HD transition in Photon Dominated Regions (PDR)

Petit¹,

Roueff²,

Bourlot³

2002

A&A

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128

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Abstract. We present the basic features of a steady state chemical model of Photon Dominated Regions (PDR), where the deuterium chemistry is explicitly introduced. The model is an extension of a previous PDR model (Abgrall et al. 1992;Le Bourlot et al. 1993; in which the microscopic processes relative to HD have been incorporated. The J-dependent photodissociation probabilities have been calculated and included in the statistical equilibrium of the rotational levels of HD where the latest collision molecular data are also introduced. The thermal balance is calculated from the equilibrium between the different heating and cooling processes. We introduce a standard model of density n H = 500 cm −3 embedded in the Interstellar Standard Radiation Field (ISRF) from which we derive the main properties of HD in PDR. The D/HD transition does not depend only on the density, radiation field but also on the chemical processes and especially on the dust formation efficiency. In standard radiation field conditions, the D/HD transition occurs in a narrow range of visual extinctions as long as density is less than 1000 cm −3 and HD is formed through the D + + H 2 reaction. At higher densities a logarithmic dependence of the location of the transition is derived. The model is applied both to ultraviolet absorption observations from the ground rotational state of HD performed in diffuse and translucent clouds and infrared emission detectable at high densities and for high ultraviolet radiation fields coming from the bright surrounding stars.Key words. astrochemistry -molecular processes -ISM: molecules IntroductionSince deuterium has been formed only at the early beginning of the universe, the elemental deuterium to hydrogen ratio is one pivotal parameter to understand the evolution of astrophysical media. In the interstellar medium (ISM), deuterium may be present in atomic but also in molecular form and over 20 single D-bearing molecules and two doubly deuterated ones have been found in cold molecular clouds and star forming regions Loinard et al. 2000). Last but not least, the triply deuterated ammonia has been detected towards two dense cold clouds (Lis et al. 2002;van der Tak et al. 2002). However, chemical fractionation processes and mantle desorption from grains take place in these molecular clouds and it is not straightforward to derive the elemental deuterium abundance from such observations (Roberts & Millar 2000a,b).Atomic deuterium has first been observed with the Copernicus satellite in the local interstellar medium and in diffuse clouds in absorption towards bright stars where HD has also been detected (see Lemoine et al. 1999 for a review). The successful launch of the FUSE (Far Ultraviolet Spectroscopy Explorer) mission allows to search for molecular HD towards fainter sources, in translucent clouds which are intermediate between diffuse and molecular clouds. FUSE detections Send offprint requests to: E. Roueff, e-mail: Evelyne.Roueff@obspm.fr of interstellar HD have been reported in a variety of galactic lines o...

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“…The lack of interest in electron-impact excitation of D 2 is possibly due to the relative unimportance of the deuterium molecule in astrophysics. Although the H/D abundance ratio is of astrophysical importance, the abundance of D 2 is very low because essentially all the deuterium is present in the form of HD (Viala et al 1988). Nevertheless, high-resolution analysis of electron-excited D 2 is a natural progression of works on molecular hydrogen and offers an opportunity to examine the accuracy of quantum mechanical calculations beyond the Born-Oppenheimer (BO) approximation.…”

Section: Introductionmentioning

confidence: 99%

High-resolution far ultraviolet emission spectra of electron-excited molecular deuterium

Abgrall

Roueff

Liu

et al. 1999

J. Phys. B: At. Mol. Opt. Phys.

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The high-resolution (full width at half maximum = 0.11 Å) emission spectrum of the deuterium molecule produced by electron-impact excitation at 100 eV has been measured in the wavelength range 1200 - 1660 Å. In conjunction with the experimental measurement, transition probabilities of and D band systems are calculated. Synthetic spectra based on the calculated transition probabilities are in very good agreement with the optically thin experimental spectra. While centrifugal effects on the overall Lyman band emission intensity in D2 and H2 are similar, the effect of rotation-vibrational perturbations between the B 1u+ and C 1u+ states on spectral intensities is found to be less significant in D2. Excitations via isotropic ( J = 0) and anisotropic ( J = ±2, and 0) interactions for the dipole forbidden E, F 1g+-X 1g+ transition are inferred from the measured spectra. Excitation cross sections of the B 1u+-X 1g+ and C 1u-X 1g+ bands, along with the estimated E, F 1g+-B 1u+ cascade cross section, for D2 are obtained.

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New Constraints on Diffuse Interstellar Cloud Models. The Model of the ζ Ophiuchi Cloud Revisited

Cited by 5 publications

References 13 publications

Dust-correlated cm wavelength continuum emission from translucent clouds ζ Oph and LDN 1780

Dust-correlated cm wavelength continuum emission from translucent clouds ζ Oph and LDN 1780

D/HD transition in Photon Dominated Regions (PDR)

High-resolution far ultraviolet emission spectra of electron-excited molecular deuterium

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