A translucent interstellar cloud at<i>z</i> = 2.69

Noterdaeme, P.; Petitjean, P.; Ledoux, C.; López, Sebastián; Srianand, R.; Vergani, S. D.

doi:10.1051/0004-6361/201015147

Cited by 132 publications

(161 citation statements)

References 73 publications

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“…When measurable, these systems show high H 2 content (Srianand et al 2008b;Noterdaeme et al 2010Noterdaeme et al , 2017. Here, we do not detect CO absorption lines in spite of the extreme H 2 column density.…”

Section: Co Moleculessupporting

confidence: 38%

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: Co Moleculessupporting

confidence: 38%

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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“…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%

“…Targeting strong C i absorbers leads to more successful detections (Noterdaeme et al 2009(Noterdaeme et al , 2010(Noterdaeme et al , 2011Balashev et al 2017) after the first detection at high-redshift by Srianand et al (2008). However, this condition is not sufficient to obtain CO in detectable amounts because CO requires more shielding from UV photons than H 2 and C i given a dissociation energy of 11.09 eV.…”

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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“…After UV absorption bands from CO were detected for the first time at high redshift in a sub-DLA towards the QSO SDSS J 143912.05+111740.6 , it became clear that the best places to detect CO in absorption at high redshift are the systems with strong C i absorption. Following this strategy allowed us to detect carbon monoxide in five additional systems (Noterdaeme et al 2009a(Noterdaeme et al , 2010a(Noterdaeme et al , 2011.…”

Section: Introductionmentioning

confidence: 99%

Neutral atomic-carbon quasar absorption-line systems atz> 1.5

Ledoux

Noterdaeme

Petitjean

et al. 2015

A&A

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We present the results of a search for cold gas at high redshift along quasar lines of sight carried out without any a priori assumption on the neutral atomic-hydrogen content of the absorption-line systems. To do this, we systematically looked for neutral-carbon (C i) λλ1560, 1656 transition lines in 41 696 low-resolution quasar spectra (1.5 < z em < 4.46) from the SDSS-II -Data Release 7 -database. C i absorption lines should indeed probe the shielded gas in the neutral interstellar medium of galaxies more efficiently than traditional tracers such as neutral atomic-hydrogen (H i) damped Lyman-α (DLA) and/or Mg ii systems. We built up a sample of 66 C i absorbers with redshifts in the range 1.5 < z < 3.1 and rest-frame equivalent widths 0.1 < W r (λ1560) < 1.7 Å. The completeness limit of our survey is W r,lim (λ1560) 0.4 Å. C i systems stronger than that are more than one hundred times rarer than DLAs at z abs = 2.5. The number of C i systems per unit redshift is found to increase significantly below z = 2. We suggest that these C i absorbers are closely related to the process of star formation and the production of dust in galaxies and that their cosmic evolution is driven by the interplay between dust shielding and the evolution of the ultra-violet background at ∼10 eV. We derive the neutral atomic-hydrogen content of the C i systems observable from the southern hemisphere from VLT/UVES spectroscopy and find that a majority of them are sub-DLAs with N(H i) ∼ 10 20 atoms cm −2 . The dust content of these absorbers is yet significant as seen from the redder optical colours of the corresponding background quasars and their reddened spectral energy distributions, with E(B − V) values up to ∼0.3. The overall N(H i) distribution of C i systems is, however, relatively flat. As a consequence, among the C i systems classifying as DLAs, there is a probable excess of strong DLAs with log N(H i) > 21 (atoms cm −2 ) compared to systematic DLA surveys. Whilst the dust content of such systems is significant, their dust-to-gas ratio must still be limited. Indeed, strong DLAs having large amounts of shielded gas and dust producing stronger reddening and extinction of the background quasars, if they exist, should have been missed in the current magnitude-limited quasar sample. We study the empirical relations between W r (C i), N(H i), E(B − V), and the strength of the 2175 Å extinction feature. The latter is detected in about 30% of the C i absorbers. We show that, at equal amount of reddening, the 2175 Å feature is weak compared to Galactic lines of sight. This is probably the consequence of current or past star formation in the vicinity of the C i systems. We also find that the strongest C i systems tend to have the largest amounts of dust and that the metallicity of the gas and its molecular fraction is likely to be high in a large number of cases. The C i-absorber sample presented here hence provides ideal targets for detailed studies of the dust composition and molecular species at high redshift.

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A translucent interstellar cloud atz = 2.69

Cited by 132 publications

References 73 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

Neutral atomic-carbon quasar absorption-line systems atz> 1.5

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