The Role of Sub–Damped Lyα Absorbers in the Cosmic Evolution of Metals

Kulkarni, Varsha P.; Khare, Pushpa; Péroux, Céline; York, Donald G.; Lauroesch, J. T.; Meiring, Joseph D.

doi:10.1086/515430

Cited by 91 publications

(158 citation statements)

References 78 publications

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“…Several works have suggested a decrease of metallicity with hydrogen column density in DLAs (e.g., Boisse et al 1998;Kulkarni & Fall 2002;Khare et al 2004;Akerman et al 2005;Meiring et al 2006), which could also extend to sub-DLAs (Péroux et al 2003a;DessaugesZavadsky et al 2003;York et al 2006;Kulkarni et al 2007;Khare et al 2007;Som et al 2013Som et al , 2015Kulkarni et al 2015). As seen in Figure 14, the value of σ h and the derived metal column densities are anticorrelated.…”

Section: Modelling Blended Linesmentioning

confidence: 63%

The Mean Metal-line Absorption Spectrum of Damped Lyα Systems in BOSS

Mas-Ribas

Miralda-Escudé

Pérez-Ràfols

et al. 2017

ApJ

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We study the mean absorption spectrum of the Damped Lyman alpha population at z ∼ 2.6 by stacking normalized, rest-frame shifted spectra of ∼ 27 000 DLAs from the DR12 of BOSS/SDSS-III. We measure the equivalent widths of 50 individual metal absorption lines in 5 intervals of DLA hydrogen column density, 5 intervals of DLA redshift, and overall mean equivalent widths for an additional 13 absorption features from groups of strongly blended lines. The mean equivalent width of low-ionization lines increases with N HI , whereas for high-ionization lines the increase is much weaker. The mean metal line equivalent widths decrease by a factor ∼ 1.1 − 1.5 from z ∼ 2.1 to z ∼ 3.5, with small or no differences between low-and high-ionization species. We develop a theoretical model, inspired by the presence of multiple absorption components observed in high-resolution spectra, to infer mean metal column densities from the equivalent widths of partially saturated metal lines. We apply this model to 14 low-ionization species and to AlIII, SIII, SiIII, CIV, SiIV, NV and OVI. We use an approximate derivation for separating the equivalent width contributions of several lines to blended absorption features, and infer mean equivalent widths and column densities from lines of the additional species NI, ZnII, CII * , FeIII, and SIV. Several of these mean column densities of metal lines in DLAs are obtained for the first time; their values generally agree with measurements of individual DLAs from high-resolution, high signal-to-noise ratio spectra when they are available.

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Section: Modelling Blended Linesmentioning

confidence: 63%

The Mean Metal-line Absorption Spectrum of Damped Lyα Systems in BOSS

Mas-Ribas

Miralda-Escudé

Pérez-Ràfols

et al. 2017

ApJ

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“…These results appear to contradict the near-solar mass-weighted mean metallicity at ∼ z 0 predicted by most models and observed in nearby galaxies. Equally surprising, a significant fraction of sub-DLAs appear to be highly metal-rich (near-solar or supersolar), even at redshifts of > z 2 (e.g., Akerman et al 2005;Péroux et al 2006aPéroux et al , 2006bPéroux et al , 2008Prochaska et al 2006;Meiring et al 2007Meiring et al , 2008Meiring et al , 2009aMeiring et al , 2009bKulkarni et al 2007Kulkarni et al , 2010Nestor et al 2008;Som et al 2013Som et al , 2015. The supersolar metallicities observed in many sub-DLAs (a large fraction of which are derived from Zn) are particularly strikingbecause no local counterparts to such systems are known among normal galaxies.…”

Section: Application To Dlas and Sub-dlasmentioning

confidence: 99%

Atomic Data for Zn Ii: Improving Spectral Diagnostics of Chemical Evolution in High-Redshift Galaxies

Kisielius

Kulkarni

Ferland

et al. 2015

ApJ

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Damped Lyα (DLA) and sub-DLA absorbers in quasar spectra provide the most sensitive tools for measuring the element abundances of distant galaxies. The estimation of abundances from absorption lines depends sensitively on the accuracy of the atomic data used. We have started a project to produce new atomic spectroscopic parameters for optical andUV spectral lines using state-of-the-art computer codes employing a very broad configuration interaction (CI) basis. Here we report our results for Zn II, an ion used widely in studies of the interstellar medium (ISM) as well as DLAs andsub-DLAs. We report new calculations of many energy levels of Zn IIand the line strengths of the resulting radiative transitions. Our calculations use the CI approach within a numerical HartreeFock framework. We use both nonrelativistic and quasi-relativistic one-electron radial orbitals. We have incorporated the results of these atomic calculations into the plasma simulation code Cloudyand applied them to a lab plasma and examples of a DLA and a sub-DLA. Our values of the Zn II λλ 2026, 2062 oscillator strengths are higher than previous values by 0.10 dex. TheCloudy calculations for representative absorbers with the revised Zn atomic data imply ionization corrections lower than calculated earlier by 0.05 dex. The new results imply that Zn metallicities should be lower by 0.1 dex for DLAs and by 0.13-0.15 dex for sub-DLAs than in past studies. Our results can be applied to other studies of Zn II in the Galactic and extragalactic ISM.

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“…It has an unusually low ratio [O i/H i] = −2.43 ± 0.05, indicating unusual ionization conditions given that intrinsic sub-DLA metallicities are rarely that low (e.g. Kulkarni et al 2007;Dessauges-Zavadsky et al 2009). All these properties identify the sub-DLA as an intrinsic system arising close to the central engine of the AGN.…”

Section: Absorption In Proximate Sub-dlamentioning

confidence: 99%

High-ion absorption in the proximate damped Ly-αsystem toward Q0841+129

Ledoux¹,

Petitjean²,

Srianand³

et al. 2011

A&A

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We present VLT/UVES spectroscopy of the quasar Q0841+129, whose spectrum shows a proximate damped Ly-α (PDLA) absorber at z = 2.47621 and a proximate sub-DLA at z = 2.50620, both lying close in redshift to the QSO itself at z em = 2.49510 ± 0.00003. This fortuitous arrangement, with the sub-DLA acting as a filter that hardens the QSO's ionizing radiation field, allows us to model the ionization level in the foreground PDLA, and provides an interesting case-study on the origin of the high-ion absorption lines Si iv, C iv, and O vi in DLAs. The high ions in the PDLA show at least five components spanning a total velocity extent of ≈160 km s −1 , whereas the low ions exist predominantly in a single component spanning just 30 km s −1 . We examine various models for the origin of the high ions. Both photoionization and turbulent mixing layer models are fairly successful at reproducing the observed ionic ratios after correcting for the non-solar relative abundance pattern, though neither model can explain all five components. We show that the turbulent mixing layer model, in which the high ions trace the interfaces between the cool PDLA gas and a hotter phase of shock-heated plasma, can explain the average high-ion ratios measured in a larger sample of 12 DLAs.

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The Role of Sub–Damped Lyα Absorbers in the Cosmic Evolution of Metals

Cited by 91 publications

References 78 publications

The Mean Metal-line Absorption Spectrum of Damped Lyα Systems in BOSS

The Mean Metal-line Absorption Spectrum of Damped Lyα Systems in BOSS

Atomic Data for Zn Ii: Improving Spectral Diagnostics of Chemical Evolution in High-Redshift Galaxies

High-ion absorption in the proximate damped Ly-αsystem toward Q0841+129

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