Probing the Metal Enrichment of the Intergalactic Medium at z = 5–6 Using the Hubble Space Telescope

Cai, Zheng; Fan, Xiaohui; Davé, Romeel; Finlator, Kristian; Oppenheimer, Benjamin D.

doi:10.3847/2041-8213/aa8fc6

Cited by 17 publications

(27 citation statements)

References 45 publications

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“…This class of Mg ii absorbers has been associated with both star formation (Nestor et al 2011) and tidal interactions (Gauthier 2013) in group environments below redshift 1. Recently, Cai et al (2017) image the SDSS J1306 + 0356 field using HST and find a single LAE with SFR = 2.5 M yr −1 . Given this, we see it likely that that these systems are tracing a multi-phase medium where hot and cold gas is mixing at the interface between the CGM and IGM.…”

Section: Resultsmentioning

confidence: 99%

“…Recently, Cai et al (2017) also investigated the environment of these same C iv absorbers using HST narrow band imaging to identify Lyα emitters (LAE). They find a single LAE candidate at an impact parameter of 205 kpc with an associated Lyα luminosity derived star formation rate, SFR Ly α = 2.5 M yr -1 .…”

Section: The Physical Connection Between Low and High Ionisation Absomentioning

confidence: 99%

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The CGM and IGM at z ∼ 5: metal budget and physical connection

Codoreanu

Ryan-Weber

Crighton

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We present further results of a survey for absorption line systems in the spectra of four high redshift quasars (5.79 ≤ z em ≤ 6.13) obtained with the ESO Very Large Telescope X-Shooter. We identify 36 C iv and 7 Si iv systems with a ≥ 5σ significance. The highest redshift C iv and Si iv absorbers identified in this work are at z = 5.80738 ± 0.00017 and z = 5.77495 ± 0.00038, respectively. We compute the comoving mass density of Si iv (Ω Si iv ) and find that it evolves from Ω Si iv = 4.3 +2.1 −2.1 ×10 −9 at = 5.05 to Ω Si iv = 1.4 +0.6 −0.4 ×10 −9 at = 5.66. We also measure Ω C iv = 1.6 +0.4 −0.1 ×10 −8 at = 4.77 and Ω C iv = 3.4 +1.6 −1.1 ×10 −9 at = 5.66. We classify our C iv absorber population by the presence of associated low and/or high ionisation systems and compute their velocity width (∆v 90 ). We find that all C iv systems with ∆v 90 > 200 kms −1 have associated low ionisation systems. We investigate two such systems separated by 550 physical kpc along a line of sight, and find it likely that they are both tracing a multi-phase medium where hot and cold gas is mixing at the interface between the CGM and IGM. We further discuss the Mg ii systems presented in a previous work and we identify 5 Si ii, 10 Al ii, 12 Fe ii, 1 C ii, 7 Mg i and 1 Ca ii associated transitions. We compute the respective comoving mass densities in the redshift range 2 to 6, as allowed by the wavelength coverage.

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Section: Resultsmentioning

confidence: 99%

Section: The Physical Connection Between Low and High Ionisation Absomentioning

confidence: 99%

The CGM and IGM at z ∼ 5: metal budget and physical connection

Codoreanu

Ryan-Weber

Crighton

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…Metal absorbers are more than just a complicated substitute for the LAF, however: given their proximity to galaxies, they are the most direct observational probe of the galaxy-driven reionization hypothesis: they probably trace activity in the faint-currently unobservably so-systems that dominated reionization (Díaz et al 2014;Cai et al 2017), and their physical state bears the chemical and radiative signatures of outflows and ionizing flux from the young stars in those galaxies.…”

Section: Introductionmentioning

confidence: 99%

Reionization in Technicolor

Finlator

Keating

Oppenheimer³

et al. 2018

Monthly Notices of the Royal Astronomical Society

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111

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We present the Technicolor Dawn simulations, a suite of cosmological radiationhydrodynamic simulations of the first 1.2 billion years. By modeling a spatiallyinhomogeneous UVB on-the-fly with 24 frequencies and resolving dark matter halos down to 10 8 M ⊙ within 12h −1 Mpc volumes, our simulations unify observations of the intergalactic and circumgalactic media, galaxies, and reionization into a common framework. The only empirically-tuned parameter, the fraction f esc,gal (z) of ionizing photons that escape the interstellar medium, is adjusted to match observations of the Lyman-α forest and the cosmic microwave background. With this single calibration, our simulations reproduce the history of reionization; the stellar mass-star formation rate relation of galaxies; the number density and metallicity of damped Lyman-α absorbers (DLAs) at z ∼ 5; the abundance of weak metal absorbers; the ultraviolet background (UVB) amplitude; and the Lyman-α flux power spectrum at z = 5.4. The galaxy stellar mass and UV luminosity functions are underproduced by ≤ 2×, suggesting an overly vigorous feedback model. The mean transmission in the Lyman-α forest is underproduced at z < 6, indicating tension between measurements of the UVB amplitude and Lyman-α transmission. The observed Si IV column density distribution is reasonably well-reproduced (∼ 1σ low). By contrast, C IV remains significantly underproduced despite being boosted by an intense > 4 Ryd UVB. Solving this problem by increasing metal yields would overproduce both weak absorbers and DLA metallicities. Instead, the observed strength of high-ionization emission from high-redshift galaxies and absorption from their environments suggest that the ionizing flux from conventional stellar population models is too soft.

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“…Other works further suggest a relationship between absorbers and host halo properties, such as mass (Oppenheimer et al 2016;Kacprzak et al 2019). There is also evidence of causal connection between galaxies and absorbers at very high redshifts (z > 5) with characteristics of early galaxies, such as their masses or star formation rates, showing some correlations with absorber equivalent widths or galaxy-absorber separation (Cai et al 2017;García et al 2017). Though the quasar number density drops significantly above z > 4, there are still a significant number of visible quasar lines-of-sight over the entire sky for z > 5.6 (Bañados et al 2016).…”

Section: Introductionmentioning

confidence: 86%

Evolution of neutral oxygen during the epoch of reionization and its use in estimating the neutral hydrogen fraction

Doughty

Finlator

2019

Monthly Notices of the Royal Astronomical Society

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We use synthetic sightlines drawn through snapshots of the Technicolor Dawn simulations to explore how the statistics of neutral oxygen (O i) absorbers respond to hydrogen reionization. The ionization state of the circumgalactic medium (CGM) initially roughly tracks that of the intergalactic medium, but beginning at z = 8 the CGM grows systematically more neutral owing to self-shielding. Weak absorbers trace diffuse gas that lies farther from halos, hence they are ionized first, whereas stronger systems are less sensitive to reionization. The overall O i covering fraction decreases slowly with time owing to competition between ongoing enrichment and gradual encroachment of ionization fronts into increasingly overdense gas. While the declining covering fraction is partially offset by continued formation of new halos, the ionization of the diffuse gas causes the predicted line-of-sight incidence rate of O i absorbers to decline abruptly at the overlap epoch, in qualitative agreement with observations. In comparison to the recently-observed equivalent width (EW) distribution at z ≈ 6, the simulations underproduce systems with EW ≥ 0.1Å, although they reproduce weaker systems with EW ≥ 0.05Å. By z ≈ 5, the incidence of EW < 0.1Å systems are overproduced, consistent with previous indications that the simulated ionizing background is too weak at z < 6. The summed column densities of Si ii and Si iv trace the total oxygen column, and hence the ratio of the O i and Si ii + Si iv comoving mass densities traces the progress of reionization. This probe may prove particularly useful in the regime where x H i > 10%.

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Probing the Metal Enrichment of the Intergalactic Medium at z = 5–6 Using the Hubble Space Telescope

Cited by 17 publications

References 45 publications

The CGM and IGM at z ∼ 5: metal budget and physical connection

The CGM and IGM at z ∼ 5: metal budget and physical connection

Reionization in Technicolor

Evolution of neutral oxygen during the epoch of reionization and its use in estimating the neutral hydrogen fraction

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