We present the first results from our KODIAQ Z survey aimed at determining the metallicity distribution and physical properties of the z ≳ 2 partial and full Lyman limit systems (pLLSs and LLSs; 16.2 ≪ logNH I > 19), which are probed of the interface regions between the intergalactic medium (IGM) and galaxies. We study 31 H Iselected pLLSs and LLSs at 2.3 < z < 3.3 observed with Keck/HIRES in absorption against background QSOs. We compare the column densities of metal ions to H I and use photoionization models to assess the metallicity. The metallicity distribution of the pLLSs/LLSs at 2.3 < z < 3.3 is consistent with a unimodal distribution peaking at [X H] ≲ -2. The metallicity distribution of these absorbers therefore evolves markedly with z since at z ≲ 1 it is bimodal with peaks at [X H] ≲ -1.8 and -0.3. There is a substantial fraction (25%-41%) of pLLSs/LLSs with metallicities well below those of damped Ly? absorbers (DLAs) at any studied z from z ≲ 1 to z ∼ 2-4, implying reservoirs of metal-poor, cool, dense gas in the IGM/galaxy interface at all z. However, the gas probed by pLLSs and LLSs is rarely pristine, with a fraction of 3%-18% for pLLSs/LLSs with [X H] ≲ -3. We find C/α enhancement in several pLLSs and LLSs in the metallicity range -2 ≲ [X H] ? -0.5, where C/α is 2-5 times larger than observed in Galactic metal-poor stars or high-redshift DLAs at similar metallicities. This is likely caused by preferential ejection of carbon from metal-poor galaxies into their surroundings.

Nicolas, L., Lehner, N., O'Meara, J., Howk, J., Prochaska, J., Fumagalli, M. (2016). THE COSMIC EVOLUTION of the METALLICITY DISTRIBUTION of IONIZED GAS TRACED by LYMAN LIMIT SYSTEMS. THE ASTROPHYSICAL JOURNAL, 833(2) [10.3847/1538-4357/833/2/283].

THE COSMIC EVOLUTION of the METALLICITY DISTRIBUTION of IONIZED GAS TRACED by LYMAN LIMIT SYSTEMS

Fumagalli M.
2016

Abstract

We present the first results from our KODIAQ Z survey aimed at determining the metallicity distribution and physical properties of the z ≳ 2 partial and full Lyman limit systems (pLLSs and LLSs; 16.2 ≪ logNH I > 19), which are probed of the interface regions between the intergalactic medium (IGM) and galaxies. We study 31 H Iselected pLLSs and LLSs at 2.3 < z < 3.3 observed with Keck/HIRES in absorption against background QSOs. We compare the column densities of metal ions to H I and use photoionization models to assess the metallicity. The metallicity distribution of the pLLSs/LLSs at 2.3 < z < 3.3 is consistent with a unimodal distribution peaking at [X H] ≲ -2. The metallicity distribution of these absorbers therefore evolves markedly with z since at z ≲ 1 it is bimodal with peaks at [X H] ≲ -1.8 and -0.3. There is a substantial fraction (25%-41%) of pLLSs/LLSs with metallicities well below those of damped Ly? absorbers (DLAs) at any studied z from z ≲ 1 to z ∼ 2-4, implying reservoirs of metal-poor, cool, dense gas in the IGM/galaxy interface at all z. However, the gas probed by pLLSs and LLSs is rarely pristine, with a fraction of 3%-18% for pLLSs/LLSs with [X H] ≲ -3. We find C/α enhancement in several pLLSs and LLSs in the metallicity range -2 ≲ [X H] ? -0.5, where C/α is 2-5 times larger than observed in Galactic metal-poor stars or high-redshift DLAs at similar metallicities. This is likely caused by preferential ejection of carbon from metal-poor galaxies into their surroundings.
Articolo in rivista - Articolo scientifico
galaxies: abundances; galaxies: halos; galaxies: high-redshift; quasars: absorption lines Supporting material: machine-readable tables;
galaxies: abundances; galaxies: halos; galaxies: high-redshift; quasars: absorption lines Supporting material: machine-readable tables
English
2016
833
2
283
open
Nicolas, L., Lehner, N., O'Meara, J., Howk, J., Prochaska, J., Fumagalli, M. (2016). THE COSMIC EVOLUTION of the METALLICITY DISTRIBUTION of IONIZED GAS TRACED by LYMAN LIMIT SYSTEMS. THE ASTROPHYSICAL JOURNAL, 833(2) [10.3847/1538-4357/833/2/283].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/261909
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