Partial covering of the emission regions of Q 0528−250 by intervening H2 clouds

Клименко, В. В.; Balashev, S. A.; Ivanchik, A. V.; Ledoux, C.; Noterdaeme, P.; Petitjean, P.; Srianand, R.; Варшалович, Д. А.

doi:10.1093/mnras/stu2672

Cited by 23 publications

(33 citation statements)

References 48 publications

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“…Partial coverage has already been detected in at least two H 2 -bearing intervening systems (e.g. Balashev et al 2011;Klimenko et al 2015). From the residual flux at the bottom of the S ii λ1259 line, we estimate that about ∼ 20 per cent of the quasar photons at the corresponding wavelengths are leaking through the S ii absorbing region of the DLA.…”

Section: S IImentioning

confidence: 73%

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: S IImentioning

confidence: 73%

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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“…The primary reason for this is that the cold and dusty phases are missed probably because of their reduced cross-sections relative to the more pervasive warm neutral ISM (Zwaan & Prochaska 2006). Direct evidence for the relatively small physical sizes ( < ∼ 0.15 pc) of H 2 -detected clouds in DLAs has recently come from the observation of partial coverage of the QSO broad-line emitting region (Balashev et al 2011;Klimenko et al 2015).…”

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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“…Varshalovich et al (2001) reported the first high-redshift detection of HD. Subsequently, various other DLA systems have been found to contain HD molecules (Noterdaeme et al 2008b;Tumlinson et al 2010;Ivanchik et al 2010Ivanchik et al , 2015Balashev et al 2010Balashev et al , 2017Albornoz Vásquez et al 2014;Klimenko et al 2015a). CO has also been observed along different high-redshift DLA sightlines (Srianand et al 2008;Noterdaeme et al 2010Noterdaeme et al , 2011Noterdaeme et al , 2017Noterdaeme et al , 2018.…”

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confidence: 99%

Multicomponent H2 in DLA at zabs = 2.05: physical conditions through observations and numerical models★

Rawlins

Srianand

Shaw

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We perform detailed spectroscopic analysis and numerical modelling of an H 2 -bearing damped Lyman-α absorber (DLA) at z abs = 2.05 towards the quasar FBQS J2340-0053. Metal absorption features arise from fourteen components spread over ∆v 90 = 114 km s −1 , seven of which harbour H 2 . Column densities of atomic and molecular species are derived through Voigt profile analysis of their absorption lines. We measure total N (H i), N (H 2 ) and N (HD) to be 20.35±0.05, 17.99±0.05 and 14.28±0.08 (log cm −2 ) respectively. H 2 is detected in the lowest six rotational levels of the ground vibrational state. The DLA has metallicity, Z = 0.3 Z ⊙ ([S/H] = -0.52±0.06) and dustto-gas ratio, κ = 0.34±0.07. Numerical models of the H 2 components are constrained individually to understand the physical structure of the DLA. We conclude that the DLA is subjected to the metagalactic background radiation and cosmic ray ionization rate of ∼ 10 −15.37 s −1 . Dust grains in this DLA are smaller than grains in the Galactic interstellar medium. The inner molecular regions of the H 2 components have density, temperature and gas pressure in the range 30-120 cm −3 , 140-360 K and 7,000-23,000 cm −3 K respectively. Micro-turbulent pressure is a significant constituent of the total pressure, and can play an important role in these innermost regions. Our H 2 component models enable us to constrain component-wise N (H i), and elemental abundances of sulphur, silicon, iron and carbon. We deduce the line-of-sight thickness of the H 2bearing parts of the DLA to be 7.2 pc.

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Partial covering of the emission regions of Q 0528−250 by intervening H2 clouds

Cited by 23 publications

References 48 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

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

Multicomponent H2 in DLA at zabs = 2.05: physical conditions through observations and numerical models★

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