The Chemistry of Interstellar Molecules Containing the Halogen Elements

Neufeld, David A.; Wolfire, M. G.

doi:10.1088/0004-637x/706/2/1594

Cited by 160 publications

(237 citation statements)

References 54 publications

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“…Hydrogen chloride is predicted to be the dominant gasphase chlorine reservoir in high-extinction regions (Blake et al 1986b;Neufeld & Wolfire 2009), consistent with the expectation that the 11.4 km s −1 component traces the large-scale envelope. On the other hand, H 2 Cl + is predicted to be a significant carrier in photon-dominated regions, and correspondingly H 2 Cl + is detected in absorption in the blue-shifted foreground slab component.…”

Section: Chlorine-bearing Moleculessupporting

confidence: 75%

TheHerschel/HIFI spectral survey of OMC-2 FIR 4 (CHESS)

Kama

López-Sepulcre

Dominik

et al. 2013

A&A

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Context. Broadband spectral surveys of protostars offer a rich view of the physical, chemical and dynamical structure and evolution of star-forming regions. The Herschel Space Observatory opened up the terahertz regime to such surveys, giving access to the fundamental transitions of many hydrides and to the high-energy transitions of many other species. Aims. A comparative analysis of the chemical inventories and physical processes and properties of protostars of various masses and evolutionary states is the goal of the Herschel CHEmical Surveys of Star forming regions (CHESS) key program. This paper focusses on the intermediate-mass protostar, OMC-2 FIR 4. Methods. We obtained a spectrum of OMC-2 FIR 4 in the 480 to 1902 GHz range with the HIFI spectrometer onboard Herschel and carried out the reduction, line identification, and a broad analysis of the line profile components, excitation, and cooling. Results. We detect 719 spectral lines from 40 species and isotopologs. The line flux is dominated by CO, H 2 O, and CH 3 OH. The line profiles are complex and vary with species and upper level energy, but clearly contain signatures from quiescent gas, a broad component likely due to an outflow, and a foreground cloud. Conclusions. We find abundant evidence for warm, dense gas, as well as for an outflow in the field of view. Line flux represents 2% of the 7 L luminosity detected with HIFI in the 480 to 1250 GHz range. Of the total line flux, 60% is from CO, 13% from H 2 O and 9% from CH 3 OH. A comparison with similar HIFI spectra of other sources is set to provide much new insight into star formation regions, a case in point being a difference of two orders of magnitude in the relative contribution of sulphur oxides to the line cooling of Orion KL and OMC-2 FIR 4.

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Section: Chlorine-bearing Moleculessupporting

confidence: 75%

TheHerschel/HIFI spectral survey of OMC-2 FIR 4 (CHESS)

Kama

López-Sepulcre

Dominik

et al. 2013

A&A

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“…Indeed, three molecular species are detected, while the presence of neutral chlorine suggests chemical reactions involving HCl and HCl + (e.g. Dalgarno et al 1974;Neufeld & Wolfire 2009). The DLA system toward J 1237+0647 is therefore an excellent candidate to target with future extremely large telescopes (ELTs) to detect other molecular species like C 2 , CH, OH and study astrochemistry in the interstellar medium of high-redshift galaxies.…”

Section: Resultsmentioning

confidence: 99%

A translucent interstellar cloud atz = 2.69

Noterdaeme¹,

Petitjean²,

Ledoux³

et al. 2010

A&A

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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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“…In addition, we expect little depletion of chlorine (Neufeld & Wolfire 2009) for the low metallicity and reddening (see Sect. 3.8) measured in this system.…”

Section: Metallicity and Depletion Patternmentioning

confidence: 91%

CO-dark molecular gas at high redshift: very large H2 content and high pressure in a low-metallicity damped Lyman alpha system

Balashev

Noterdaeme

Rahmani

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present a detailed analysis of an H 2 -rich, extremely strong intervening damped Ly-α absorption system (DLA) at z abs = 2.786 towards the quasar J 0843+0221, observed with the Ultraviolet and Visual Echelle Spectrograph on the Very Large Telescope. The total column density of molecular (resp. atomic) hydrogen is log N(H 2 )=21.21 ± 0.02 (resp. log N(H i)=21.82 ± 0.11), making it to be the first case in quasar absorption line studies with H 2 column density as high as what is seen in 13 CO-selected clouds in the Milky-Way.We find that this system has one of the lowest metallicity detected among H 2 -bearing DLAs, with [Zn/H] = −1.52 +0.08 −0.10 . This can be the reason for the marked differences compared to systems with similar H 2 column densities in the local Universe: (i) the kinetic temperature, T ∼120 K, derived from the J = 0, 1 H 2 rotational levels is at least twice higher than expected; (ii) there is little dust extinction with A V < 0.1; (iii) no CO molecules are detected, putting a constraint on the X CO factor X CO > 2 × 10 23 cm −2 /(km/s K), in the very low metallicity gas. Low CO and high H 2 contents indicate that this system represents "CO-dark/faint" gas.We investigate the physical conditions in the H 2 -bearing gas using the fine-structure levels of C i, C ii, Si ii and the rotational levels of HD and H 2 . We find the number density to be about n ∼ 260 − 380 cm −3 , implying a high thermal pressure of 3 − 5 × 10 4 cm −3 K. We further identify a trend of increasing pressure with increasing total hydrogen column density. This independently supports the suggestion that extremely strong DLAs (with log N(H) ∼ 22) probe high-z galaxies at low impact parameters.

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The Chemistry of Interstellar Molecules Containing the Halogen Elements

Cited by 160 publications

References 54 publications

TheHerschel/HIFI spectral survey of OMC-2 FIR 4 (CHESS)

TheHerschel/HIFI spectral survey of OMC-2 FIR 4 (CHESS)

A translucent interstellar cloud atz = 2.69

CO-dark molecular gas at high redshift: very large H2 content and high pressure in a low-metallicity damped Lyman alpha system

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