The B′ 1Σu+ → X 1Σg+ and D 1Πu → X 1Σg+ band systems of molecular hydrogen

Abgrall, H.; Roueff, E.; Launay, Françoise; Roncin, Jean-Yves

doi:10.1139/p94-112

Cited by 85 publications

(109 citation statements)

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“…The origin of the velocity scale for this figure and all following ones is defined at the position of the CO-bearing component at z abs = 2.68957. and oscillator strengths were taken from Morton & Noreau (1994) and Eidelsberg & Rostas (2003) for CO and from Abgrall & Roueff (2006) for HD. Updated wavelengths of H 2 Lyman and Werner bands were taken from Bailly et al (2010), with oscillator strengths from the Meudon group 1 , based on calculations described in Abgrall et al (1994). Photospheric solar abundances are taken from Asplund et al (2009).…”

Section: Discussionmentioning

confidence: 99%

A translucent interstellar cloud atz = 2.69

Noterdaeme¹,

Petitjean²,

Ledoux³

et al. 2010

A&A

131

147

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We present the analysis of a sub-damped Lyman-α system with neutral hydrogen column density, log N(H 0 ) (cm −2 ) = 20.0 ± 0.15 at z abs = 2.69 toward SDSS J123714.60+064759.5 (z em = 2.78). Using the VLT/UVES and X-shooter spectrographs, we detect H 2 , HD, and CO molecules in absorption with log N(H 2 , HD, CO) (cm −2 ) = 19.21 +0.13 −0.12 , 14.48 ± 0.05 and 14.17 ± 0.09 respectively. The overall metallicity of the system is super-solar ([Zn/H] = +0.34 relative to solar) and iron is highly depleted ([Fe/Zn] = −1.39), revealing metal-rich and dusty gas. Three H 2 velocity components spanning ∼125 km s −1 are detected. The strongest H 2 component, at z abs = 2.68955, with log N(H 2 ) = 19.20, does not coincide with the centre of the H i absorption. This implies that the molecular fraction in this component, f H 2 = 2N(H 2 )/(2N(H 2 )+N(H 0 )), is higher than the mean molecular fraction f H 2 = 1/4 in the system. We also found the Cl 0 associated with this H 2 component to have N(Cl 0 )/N(Cl + ) > 0.4, which points in the same direction. Cl 0 is tied to H 2 by charge exchange reactions, this means that the molecular fraction in this component is not far from unity. The kinetic temperature derived from the J = 0 and 1 rotational levels of H 2 is T = 108 +84 −33 K and the particle density derived from the C 0 ground-state fine structure level populations is n H0 ∼ 50-60 cm −3 . We derive an electronic density <2 cm −3 for a UV field similar to the Galactic one and show that the carbon-to-sulphur ratio in the cloud is close to the solar ratio. The size of the molecular cloud is probably smaller than 1 pc. Both the CO/H 2 = 10 −5 and CO/C 0 ∼ 1 ratios for f H 2 > 0.24 indicate that the cloud classifies as translucent, i.e., a regime where carbon is found both in atomic and molecular form. The corresponding extinction, A V = 0.14, albeit lower than the definition of a translucent sightline (based on extinction properties), is high for the observed H 0 column density. This means that intervening clouds with similar local properties but with higher column densities (i.e. larger physical extent) could be missed by current magnitudelimited QSO surveys. The excitation of CO is dominated by radiative interaction with the cosmic microwave background radiation (CMBR) and we derive T ex (CO) = 10.5 +0.8 −0.6 K when T CMBR (z = 2.69) = 10.05 K is expected. We measure N(HD)/2N(H 2 ) = 10 −5 . This is about 10 times higher than what is measured in the Galactic ISM for f H 2 = 1/4 but similar to what is measured in the Galactic ISM for higher molecular fractions. The astration factor of deuterium with respect to the primordial D/H ratio is only about 3. This can be the consequence of accretion of unprocessed gas from the intergalactic medium onto the associated galaxy. In the future, it will be possible to search efficiently for molecular-rich DLAs/sub-DLAs with X-shooter, but detailed studies of the physical state of the gas will still need UVES observations.

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Section: Discussionmentioning

confidence: 99%

A translucent interstellar cloud atz = 2.69

Noterdaeme¹,

Petitjean²,

Ledoux³

et al. 2010

A&A

131

147

View full text Add to dashboard Cite

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“…The FUSE spectrum at the (1, 0) vibrational transition was too noisy to perform a good fit. The H 2 line positions and oscillator strengths were adopted from Abgrall et al (1994). The total transition probabilities that include the transitions to continuum (dissociating) states were taken from Abgrall et al (2000).…”

Section: Column Densitiesmentioning

confidence: 99%

Interstellar H₂toward HD 37903

Gnaciński

2011

A&A

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We present an analysis of interstellar H 2 toward HD 37903, which is a hot B 1.5 V star located in the NGC 2023 reflection nebula. Meyer et al. (2001, ApJ, 553, L59) used a rich spectrum of vibrationally excited H 2 observed by the HST to calculate a model of the interstellar cloud toward HD 37903. We extend their analysis by including the ν = 0 vibrational level observed by the FUSE satellite. The temperature calculated from the two lowest rotational levels (J = 0, 1) of the H 2 molecule should not be interpreted as a "rotational temperature", but rather as a temperature of thermal equilibrium between the ortho and para H 2 . The ortho-to-para H 2 ratio is lower for the lowest rotational levels than for the higher levels populated by fluorescence. The PDR model of the cloud located in front of HD 37903 points to a gas kinetic temperature ranging from 110 K on the observer side of the cloud to 377 K on the star side. The hydrogen density changes from n H = 1874 cm −3 on the observer side to 544 cm −3 on the star side. The star-cloud distance in our model is 0.45 pc.

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“…It should be noted that most of these 40 lines are resonance transitions. The optical thickness in the discharge experiments of Roncin et al (1984), Abgrall et al (1994), and prevents these resonance transitions from being observed. It should also be pointed out that the previous high-resolution emission studies were limited to wavelengths longer than 786 presumably since A , the weakness of the transitions and the required optical thickness make it impractical to study the transitions on the blue side of 786…”

Section: Methodsmentioning

confidence: 96%

“…While molecular hydrogen has been investigated extensively in the extreme ultraviolet (EUV) region with photoabsorption (MonÐls 1961(MonÐls , 1965Namioka 1964aNamioka , 1964bWilkinson 1968 ;Takezawa 1970 ;Herzberg & Jungen 1972 ;Dabrowski 1984 ;Glass-Maujean, Breton, & Guyon 1984, 1985, photoionization (Demher & Chupka 1976, 1995, and nonlinear laser techniques Pratt et al 1990Pratt et al , 1992Pratt et al , 1994OÏHalloran et al 1988OÏHalloran et al , 1989Hinnen et al 1994aHinnen et al , 1994b, 1996Reinhold, Hogervorst, & Ubachs 1996, 1997Hogervorst et al 1998), relatively few emission studies of H 2 have been performed in the EUV region (Herzberg & Howe 1959 ;Lunay, & Roncin 1980, 1985Daborwski Larzillie re, 1984 ;Roncin, Launay, & 1984 ;Ajello et al 1984, Larzillie re 1988Abgrall et al 1987Abgrall et al , 1994. To the blue side of the 1040 wavelength region, emissions from various levels of the A and Rydberg states to the 1sp g npp u 1& u 1sp g npn u 1% u v i \ level of the X state (i.e., resonance transitions) domi-0 1& g nate the spectrum.…”

Section: Introductionmentioning

confidence: 99%

“…Utilization of a low-pressure (D10~2 torr) discharge lamp has enabled et al (1980,1985) and Larzillie re Roncin et al (1984) to extend emission studies down to 780 although most resonance lines are still self-absorbed. A , Joint experimental emission observations and semiÈab initio calculations by Abgrall et al (1987Abgrall et al ( , 1993aAbgrall et al ( , 1993bAbgrall et al ( , 1993cAbgrall et al ( , 1994 (1994). The cross sections and emission yields of some Rydberg band systems have been reported in a companion paper in this issue (Jonin et al 2000, hereafter Paper I).…”

Section: Introductionmentioning

confidence: 99%

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