Ionization Properties and Elemental Abundances in Damped Lyα Systems

Vladilo, G.; Centurión, M.; Bonifacio, P.; Howk, J. C.

doi:10.1086/321650

Cited by 126 publications

(211 citation statements)

References 38 publications

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“…Indeed, even systems with much higher column densities may not be immune to such effects (Howk & Sembach 1999;Izotov et al 2001;Vladilo et al 2003; although some contrary views are presented by Vladilo et al 2001). A very important indicator of whether or not one is being misled by partial ionization effects is Ar i (Sofia & Jenkins 1998;Vladilo et al 2003), but unfortunately our upper limit for N(Ar i) is so high that it is not useful for this purpose.…”

Section: à0:41mentioning

confidence: 94%

A Near‐Solar Metallicity, Nitrogen‐deficient Lyman Limit Absorber Associated with Two S0 Galaxies

Jenkins

Bowen

Tripp³

et al. 2005

ApJ

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The UV spectrum of the bright quasar PHL 1811 at z em ¼ 0:192 reveals a foreground gas system at z ¼ 0:080923 with log N (H i) ¼ 17:98 AE 0:05. We have determined the abundances of various atomic species in this system from a spectrum covering the wavelength range 1160-1730 8 recorded at 7 km s À1 resolution by the E140M grating of the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST ), supplemented by coverage at shorter wavelengths by the Far Ultraviolet Spectroscopic Explorer (FUSE ). The abundances of C ii, Si ii, S ii, and Fe ii compared to that of O i indicate that a considerable fraction of the gas is in locations where the hydrogen is ionized. An oxygen abundance ½O/ H ¼ À0:19 AE 0:08 in the H i-bearing gas indicates that the chemical enrichment of the gas is unusually high for an extragalactic QSO absorption system. However, this same material has an unusually low abundance of nitrogen, ½N/ O < À0:59, indicating that there may not have been enough time during this enrichment for secondary nitrogen to arise from low-and intermediate-mass stars. From the convergence of high Lyman series lines we can determine the velocity width of H i, and after correcting for turbulent broadening shown by the O i absorption feature, we derive a temperature T ¼ 7070 þ3860 À4680 K. We determine a lower bound for the electron density n(e) > 10 À3 cm À3 by modeling the ionization by the intergalactic radiation field and an upper bound n(e) < 0:07 cm À3 from the absence of much C ii in an excited fine-structure level. The thermal pressure in the range 4 cm À3 K < p / k < 140 cm À3 K could be confined by a warm-hot intergalactic medium (WHIM) structure with /¯$ 20 that might accompany a wall of galaxies at the same redshift, seen in data from the Sloan Digital Sky Survey. An r-band image of the field surrounding PHL 1811 recorded by the ACS instrument on HST shows that two galaxies at the same redshift as the gas are S0 galaxies, separated by only 34 and 87 h À1 70 kpc from the line of sight. One or both of these galaxies may be the source of the material in the Lyman limit system, which may have been expelled from them in a fast wind, by tidal stripping, or by ram pressure stripping. Subtraction of the ACS point-spread function from the image of the QSO reveals the presence of a face-on spiral galaxy under the glare of the quasar; while it is possible that this galaxy may be responsible for the Lyman limit absorption, the exact alignment of the QSO with the center of the galaxy suggests that the spiral is the quasar host.

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Section: à0:41mentioning

confidence: 94%

A Near‐Solar Metallicity, Nitrogen‐deficient Lyman Limit Absorber Associated with Two S0 Galaxies

Jenkins

Bowen

Tripp³

et al. 2005

ApJ

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“…Had we assumed log 10 N w ¼ 19:0 cm À2 , the total column density of neutral plus ionized gas would exceed log N ¼ 20:0 cm À2 , and it is the total column density that is crucial for determining X-ray opacity. Furthermore, Vladilo et al (2001) present strong arguments that gas in DLAs is mostly neutral. Thus, our limit is conservative.…”

Section: Heatingmentioning

confidence: 94%

Cii* Absorption in Damped Lyα Systems. I. Star Formation Rates in a Two‐Phase Medium

Wolfe

Prochaska

Gawiser

2003

ApJ

160

261

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We describe a technique that for the first time measures star formation rates (SFRs) in damped Ly systems (DLAs) directly. We assume that massive stars form in DLAs and that the far-ultraviolet (FUV) radiation they emit heats the gas by the grain photoelectric mechanism. We infer the heating rate by equating it to the cooling rate measured by the strength of C ii* 1335.7 absorption. Since the heating rate is proportional to the product of the dust-to-gas ratio, the grain photoelectric heating efficiency, and the SFR per unit area, _ Ã Ã , we can deduce _ Ã Ã for DLAs in which the cooling rate and dust-to-gas ratio have been measured. We consider models in which the dust consists of carbonaceous grains and silicate grains. We present twophase models in which the cold neutral medium (CNM) and warm neutral medium (WNM) are in pressure equilibrium. In the CNM model the line of sight passes through CNM and WNM gas, while in the WNM model the line of sight passes only through WNM gas. Since the grain photoelectric heating efficiency is at least an order of magnitude higher in the CNM than in the WNM, most of the C ii* absorption arises in the CNM in the CNM model. We use the measured C ii* absorption lines to derive _ Ã Ã for a sample of %30 DLAs in which has been inferred from element depletion patterns. We show that the inferred _ Ã Ã corresponds to an average over the star-forming volume of the DLA rather than to local star formation along the line of sight. We obtain the average _ Ã Ã and show that _ Ã Ã ¼ 10 À2:2 M yr À1 kpc À2 for the CNM solution and _ Ã Ã ¼ 10 À1:3 M yr À1 kpc À2 for the WNM solution. Interestingly, the SFR per unit area in the CNM solution is similar to that measured in the Milky Way interstellar medium.

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“…However, with the stellar field CLOUDY is not able to finish the calculations because the gas temperature falls below the minimum allowed value before the total N(H i) is attained. To bypass this problem, Vladilo et al (2001) considered a two-region model composed of a mildly ionised interface and an inner neutral region that only hosts dominant ionisation species.…”

Section: Ionisation Effectsmentioning

confidence: 99%

The ESO UVES Advanced Data Products Quasar Sample – IV. On the deficiency of argon in DLA systems

Zafar¹,

Vladilo²,

Péroux³

et al. 2014

Monthly Notices of the Royal Astronomical Society

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In this work, we study argon abundances in the interstellar medium of high-redshift galaxies (2.0 z abs 4.2) detected as Damped Lyα absorbers (DLA) in the spectra of background quasars. We use high-resolution quasar spectra obtained from the ESO-UVES advanced data products (EUADP) database. We present 3 new measurements and 5 upper limits of Ar i. We further compiled DLAs/sub-DLA data from the literature with measurements available of argon and α-capture elements (S or Si), making up a total of 37 systems, i.e. the largest DLA argon sample investigated so far. We confirm that argon is generally deficient in DLAs, with a mean value [Ar/α] ≃ −0.4 ± 0.06 dex (standard error of the mean). The [Ar/α] ratios show a weak, positive trend with increasing H i column density and increasing absorption redshift, and a weak, negative trend with dust-free metallicity, [S/H]. Detailed analysis of the abundance ratios indicates that Ar i ionisation, rather than dust depletion or nucleosynthetic evolution, is responsible for the argon deficiency. Altogether, the observational evidence is consistent with a scenario of argon ionisation dominated by quasar metagalactic radiation modulated by local H i self-shielding inside the DLA host galaxies. Our measurements and limits of argon abundances suggest that the cosmic reionisation of He ii is completed above z ∼ 3, but more measurements at z abs > 3.5 are required to probe the final stages of this process of cosmic reionisation.

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Ionization Properties and Elemental Abundances in Damped Lyα Systems

Cited by 126 publications

References 38 publications

A Near‐Solar Metallicity, Nitrogen‐deficient Lyman Limit Absorber Associated with Two S0 Galaxies

A Near‐Solar Metallicity, Nitrogen‐deficient Lyman Limit Absorber Associated with Two S0 Galaxies

Cii* Absorption in Damped Lyα Systems. I. Star Formation Rates in a Two‐Phase Medium

The ESO UVES Advanced Data Products Quasar Sample – IV. On the deficiency of argon in DLA systems

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