VLT/UVES observations of extremely strong intervening damped Lyman-<i>α</i>systems

Noterdaeme, P.; Srianand, R.; Rahmani, H.; Petitjean, P.; Pâris, Isabelle; Ledoux, C.; Gupta, N.; López, Sebastián

doi:10.1051/0004-6361/201425376

Cited by 68 publications

(76 citation statements)

References 95 publications

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“…In Fig. 15 we compare this 'average' excitation with that of other high-N(H 2 ) absorption systems: embedded in a typical UV field of the MW (Gry et al 2002), a highly excited case towards the O9.5V runaway star HD 34078 (Boisse et al 2005) and the ESDLA at z = 2.34 towards J 2140−0321 (Noterdaeme et al 2015b). Both high-z DLAs show H 2 excitation higher than typical MW values, but lower than towards the OV star.…”

Section: Uv Fluxmentioning

confidence: 99%

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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Section: Uv Fluxmentioning

confidence: 99%

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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“…Neutral carbon has been considered an excellent tracer of molecular hydrogen (H 2 ) because the ionization potential of C i (11.26 eV) is very close to the dissociation energy of H 2 (e.g., Srianand et al 2005). When H 2 is detected, C i is always present in the same system (e.g., Ge & Bechtold 1999;Ge, Bechtold, & Kulkarni 2001;Srianand et al 2008;Guimarães et al 2012;Noterdaeme et al 2015;Balashev et al 2017.) Neutral Chlorine (Cl i), although rarely detected, is an alternative excellent tracer of H 2 (Jura 1974;Moomey, Federman, & Sheffer 2012;Noterdaeme et al 2010;Ma et al 2015;Balashev et al 2015).…”

Section: Das As Molecular Gas Tracersmentioning

confidence: 99%

Quasar 2175 Å dust absorbers – II. Correlation analysis and relationship with other absorption line systems

Prochaska

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present the cold neutral content (H i and C i gas) of 13 quasar 2175Å dust absorbers (2DAs) at z = 1.6 -2.5 to investigate the correlation between the presence of the UV extinction bump with other physical characteristics. These 2DAs were initially selected from the Sloan Digital Sky Surveys I -III and followed up with the Keck-II telescope and the Multiple Mirror Telescope as detailed in our Paper I. We perform a correlation analysis between metallicity, redshift, depletion level, velocity width, and explore relationships between 2DAs and other absorption line systems. The 2DAs on average have higher metallicity, higher depletion levels, and larger velocity widths than Damped Lyman-α absorbers (DLAs) or subDLAs. The correlation between [Zn/H] and [Fe/Zn] or [Zn/H] and log∆V 90 can be used as alternative stellar mass estimators based on the well-established mass-metallicity relation. The estimated stellar masses of the 2DAs in this sample are in the range of ∼ 10 9 to ∼2 × 10 11 M ⊙ with a median value of ∼2 × 10 10 M ⊙ . The relationship with other quasar absorption line systems can be described as (1) 2DAs are a subset of Mg ii and Fe ii absorbers, (2) 2DAs are preferentially metal-strong DLAs/subDLAs, (3) More importantly, all of the 2DAs show C i detections with logN(C i) > 14.0 cm −2 , (4) 2DAs can be used as molecular gas tracers. Their host galaxies are likely to be chemically enriched, evolved, massive (more massive than typical DLA/subDLA galaxies), and presumably star-forming galaxies.

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“…Ledoux et al (2015) have measured the equivalent widths of the λ1560 and λ1656 C I multiplets for 66 systems found in a sample of low-resolution (R∼2000) Sloan Digital Sky Survey spectra of 41,696 quasars-but higher-resolution spectra will be needed to determine accurate column densities and to assess the fine-structure excitation in those systems. Moderately high resolution spectra (mostly from Keck/HIRES and/or VLT/UVES) have yielded detections of C I in a smaller number of systems, and fits to the line profiles have yielded column densities for the ground and excited fine-structure states for the "individual" components discernible in the spectra (Quast et al 2002;Srianand et al 2005Srianand et al , 2008Noterdaeme et al 2007bNoterdaeme et al , 2010Noterdaeme et al , 2015Jorgenson et al 2010;Carswell et al 2011;Ma et al 2015). Srianand et al (2005) performed a simplified analysis of the C I excitation for components in eight systems (considering only collisions with atomic hydrogen and generally assuming T=100 K) and found somewhat higher pressures than those typically found in the local Galactic ISM.…”

Section: I In Qso Absorption-line Systemsmentioning

confidence: 99%

“…have been detected (Quast et al 2002;Srianand et al 2005Srianand et al , 2008Noterdaeme et al 2007aNoterdaeme et al , 2010Noterdaeme et al , 2015Jorgenson et al 2010;Carswell et al 2011;Guimarães et al 2012). The bottom section lists systems for which only total C I column densities are available; in some cases, the values are for just the ground fine-structure state.…”

Section: Appendix E C I In Qso Absorption-line Systemsmentioning

confidence: 99%

Thermal Pressures in the Interstellar Medium of the Magellanic Clouds*

Welty

Lauroesch

Wong

et al. 2016

ApJ

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We discuss the thermal pressures (n H T) in predominantly cold, neutral interstellar gas in the Magellanic Clouds, derived from analyses of the fine-structure excitation of neutral carbon, as seen in high-resolution Hubble Space Telescope/Space Telescope Imaging Spectrograph spectra of seven diverse sight lines in the LMC and SMC. Detailed fits to the line profiles of the absorption from C I, C I * , and C I ** yield consistent column densities for the three to six C I multiplets detected in each sight line. In the LMC and SMC, N(C I tot ) is consistent with Galactic trends versus N(Na I) and N(CH), but is slightly lower versus N(K I) and N(H 2 ). As for N(Na I) and N(K I), N(C I tot ) is generally significantly lower, for a given N(H tot ), in the LMC and (especially) in the SMC, compared to the local Galactic relationship. For the LMC and SMC components with well-determined column densities for C I, C I * , and C I ** , the derived thermal pressures are typically factors of a few higher than the values found for most cold, neutral clouds in the Galactic ISM. Such differences are consistent with the predictions of models for clouds in systems (like the LMC and SMC) that are characterized by lower metallicities, lower dust-to-gas ratios, and enhanced radiation fields-where higher pressures are required for stable cold, neutral clouds. The pressures may be further enhanced by energetic activity (e.g., due to stellar winds, star formation, and/or supernova remnants) in several of the regions probed by these sight lines. Comparisons are made with the C I observed in some quasar absorption-line systems.

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VLT/UVES observations of extremely strong intervening damped Lyman-αsystems

Cited by 68 publications

References 95 publications

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

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

Quasar 2175 Å dust absorbers – II. Correlation analysis and relationship with other absorption line systems

Thermal Pressures in the Interstellar Medium of the Magellanic Clouds*

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