The effect of dust bias on the census of neutral gas and metals in the high-redshift Universe due to SDSS-II quasar colour selection

Krogager, J.-K.; Fynbo, J. P. U.; Møller, P.; Noterdaeme, P.; Heintz, K. E.; Pettini, Max

doi:10.1093/mnras/stz1120

Cited by 34 publications

(25 citation statements)

References 73 publications

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“…As discussed by these authors (and previously by Ledoux et al 2009), the extinction by dust in so-called dark bursts (with A V > 0.5) is high enough for the optical afterglow to become too faint for spectroscopic follow-up, implying a bias against dimmed systems in the spectral follow-up campaigns of GRB afterglows. In principle, a similar bias could also apply to quasars when they are identified based on their colours in a flux-limited sample, as demonstrated by Krogager et al (2019) for the SDSS-II. However, the following SDSS stages are likely less inclined to dust bias because of improved selection methods and deeper observations.…”

Section: Dust Reddeningmentioning

confidence: 89%

Chemical enrichment and host galaxies of extremely strong intervening DLAs towards quasars

Ranjan

Noterdaeme

Krogager

et al. 2020

A&A

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We present the results from VLT/X-shooter spectroscopic observations of 11 extremely strong intervening damped Lyman-α absorbers (ESDLAs) that were initially selected as high N(H I) (i.e. ≥5 × 1021 cm−2) candidates from the Sloan Digital Sky Survey (SDSS). We confirm the high H I column densities, which we measure to be in the range log N(H I) = 21.6 − 22.4. Molecular hydrogen is detected with high column densities (N(H2)≥1018 cm−2) in 5 out of 11 systems, 3 of which are reported here for the first time, and we obtain conservative upper limits on N(H2) for the remaining 6 systems. We also measure the column density of various metal species (Zn II, Fe II, Si II, Cr II, and C I), quantify the absorption-line kinematics (Δv90), and estimate the extinction of the background quasar light (AV) by dust in the absorbing gas. We compare the chemical properties of this sample of ESDLAs, supplemented with literature measurements, to that of DLAs located at the redshift of long-duration γ-ray bursts (GRB-DLAs). We confirm that the two populations are almost indistinguishable in terms of chemical enrichment and gas kinematics. In addition, we find no marked differences in the incidence of H2. All this suggests that ESDLAs and GRB-DLAs probe similar galactic environments. We search for the galaxy counterparts of ESDLAs and find associated emission lines in 3 out of 11 systems, 2 of which are reported here for the first time (at zabs = 2.304 and 2.323 towards the quasars SDSS J002503.03+114547.80 and SDSS J114347.21+142021.60, respectively). The measured separations between the quasar sightlines and the emission associated with the ESDLA galaxy (for a total of five sightlines) are all very small (ρ < 3 kpc). Because our observations are complete up to ρ ∼ 7 kpc, we argue that the emission counterparts of the remaining systems are more likely below the detection limit than outside the search area. While the small impact parameters are similar to what is observed for GRB-DLAs, the associated star formation rates are on average lower than for GRB host galaxies. This is explained by long-duration GRBs being associated with the death of massive stars and therefore pinpointing regions of active star formation in the GRB host galaxies. Our observations support the suggestion from the literature that ESDLAs could act as blind analogues of GRB-DLAs, probing neutral gas with high column density in the heart of high-redshift galaxies, without any prior on the instantaneous star formation rate.

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Section: Dust Reddeningmentioning

confidence: 89%

Chemical enrichment and host galaxies of extremely strong intervening DLAs towards quasars

Ranjan

Noterdaeme

Krogager

et al. 2020

A&A

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“…The depletion of gas on to dust grains plagues metallicity measurements in QSO absorber analyses, as a component of the total metal content is missed. Such an effect is suspected to have an impact on the total metallicity evolution of subDLAs and DLAs (De Cia et al 2018;Krogager et al 2019;Poudel et al 2020). Corrections for dust depletion can be computed, but require the detection of multiple chemical elements in the absorber to either model the physical and chemical properties (Jenkins 2009;De Cia et al 2016) or measure abundance ratios of elements with similar nucleosynthetic origins (Berg et al 2015a).…”

Section: Effects Of Dust Depletionmentioning

confidence: 99%

Sub-damped Lyman α systems in the XQ-100 survey – II. Chemical evolution at 2.4 ≤ z ≤ 4.3

Berg

Fumagalli

D’Odorico

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We present the measured gas-phase metal column densities in 155 sub-damped Lyα systems (subDLAs) with the aim to investigate the contribution of subDLAs to the chemical evolution of the Universe. The sample was identified within the absorber-blind XQ-100 quasar spectroscopic survey over the redshift range 2.4 ≤ zabs ≤ 4.3. Using all available column densities of the ionic species investigated (mainly C iv, Si ii, Mg ii, Si iv, Al ii, Fe ii, C ii, and O i; in order of decreasing detection frequency), we estimate the ionization-corrected gas-phase metallicity of each system using Markov Chain Monte Carlo techniques to explore a large grid of Cloudy ionization models. Without accounting for ionization and dust depletion effects, we find that the H i-weighted gas-phase metallicity evolution of subDLAs are consistent with damped Lyα systems (DLAs). When ionization corrections are included, subDLAs are systematically more metal-poor than DLAs (between ≈0.5σ and ≈3σ significance) by up to ≈1.0 dex over the redshift range 3 ≤ zabs ≤ 4.3. The correlation of gas-phase [Si/Fe] with metallicity in subDLAs appears to be consistent with that of DLAs, suggesting that the two classes of absorbers have a similar relative dust depletion pattern. As previously seen for Lyman limit systems, the gas-phase [C/O] in subDLAs remains constantly solar for all metallicities indicating that both subDLAs and Lyman limit systems could trace carbon-rich ejecta, potentially in circumgalactic environments.

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“…3.2), we calculated the optical extinction (A V ) following Zafar & Møller (2019). We included a mock optical selection similar to large spectroscopic surveys by probabilistically rejecting sightlines with large A V (Krogager et al 2019). For details regarding the implementation, we refer readers to K20.…”

Section: Modeling Neutral Gas Absorptionmentioning

confidence: 99%

Modeling the statistics of the cold neutral medium in absorption-selected high-redshift galaxies

Krogager

Noterdaeme

2020

A&A

Self Cite

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We present a statistical model of the selection function of cold neutral gas in high-redshift (z = 2.5) absorption systems. The model is based on the canonical two-phase model of the neutral gas in the interstellar medium and contains only one parameter for which we do not have direct observational priors: namely the central pressure of an L * halo at z = 2.5, P *. Using observations of the fraction of cold gas absorption in strong H i-selected absorbers, we were able to constrain P *. The model simultaneously reproduces the column density distributions of H i and H 2 , and we derived an expected total incidence of cold gas at z ∼ 2.5 of l cnm = 12 × 10 −3. Compared to recent measurements of the incidence of C i-selected absorbers (EW λ 1560 > 0.4 Å), the value of l cnm from our model indicates that only 15% of the total cold gas would lead to strong C i absorption (EW > 0.4 Å). Nevertheless, C i lines are extremely useful probes of the cold gas as they are relatively easy to detect and provide direct constraints on the physical conditions. Lastly, our model self-consistently reproduces the fraction of cold gas absorbers as a function of N H i .

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The effect of dust bias on the census of neutral gas and metals in the high-redshift Universe due to SDSS-II quasar colour selection

Cited by 34 publications

References 73 publications

Chemical enrichment and host galaxies of extremely strong intervening DLAs towards quasars

Chemical enrichment and host galaxies of extremely strong intervening DLAs towards quasars

Sub-damped Lyman α systems in the XQ-100 survey – II. Chemical evolution at 2.4 ≤ z ≤ 4.3

Modeling the statistics of the cold neutral medium in absorption-selected high-redshift galaxies

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