A recalibration of strong-line oxygen abundance diagnostics via the direct method and implications for the high-redshift universe

ABSTRACT We present detections of [O iii] λ4363 and direct-method metallicities for star-forming galaxies at z = 1.7–3.6. We combine new measurements from the MOSFIRE Deep Evolution Field (MOSDEF) survey with literature sources to construct a sample of 18 galaxies with direct-method metallicities at z > 1, spanning 7.5 < 12+log(O/H) < 8.2 and log(M*/M⊙) = 7–10. We find that strong-line calibrations based on local analogues of high-redshift galaxies reliably reproduce the metallicity of the z > 1 sample on average. We construct the first mass–metallicity relation at z > 1 based purely on direct-method O/H, finding a slope that is consistent with strong-line results. Direct-method O/H evolves by ≲0.1 dex at fixed M* and star formation rate from z ∼ 0 to 2.2. We employ photoionization models to constrain the ionization parameter and ionizing spectrum in the high-redshift sample. Stellar models with supersolar O/Fe and binary evolution of massive stars are required to reproduce the observed strong-line ratios. We find that the z > 1 sample falls on the z ∼ 0 relation between ionization parameter and O/H, suggesting no evolution of this relation from z ∼ 0 to z ∼ 2. These results suggest that the offset of the strong-line ratios of this sample from local excitation sequences is driven primarily by a harder ionizing spectrum at fixed nebular metallicity compared to what is typical at z ∼ 0, naturally explained by supersolar O/Fe at high redshift caused by rapid formation time-scales. Given the extreme nature of our z > 1 sample, the implications for representative z ∼ 2 galaxy samples at ∼1010 M⊙ are unclear, but similarities to z > 6 galaxies suggest that these conclusions can be extended to galaxies in the epoch of reionization.

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Spatially resolved direct method metallicity in a high-redshift analogue local galaxy: temperature structure impact on metallicity gradients

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3757 ◽

2020 ◽

Author(s):

Alex J Cameron ◽

Tiantian Yuan ◽

Michele Trenti ◽

David C Nicholls ◽

Lisa J Kewley

Keyword(s):

Direct Method ◽

High Redshift ◽

Direct Methods ◽

Spectroscopic Studies ◽

Strong Line ◽

H Ii Regions ◽

Temperature Structure ◽

Spatially Resolved ◽

Systematic Effects ◽

Gradient Measurements

Abstract We investigate how H ii region temperature structure assumptions affect “direct-method” spatially-resolved metallicity observations using multispecies auroral lines in a galaxy from the SAMI Galaxy Survey. SAMI609396B, at redshift z = 0.018, is a low-mass galaxy in a minor merger with intense star formation, analogous to conditions at high redshifts. We use three methods to derive direct metallicities and compare with strong-line diagnostics. The spatial metallicity trends show significant differences among the three direct methods. Our first method is based on the commonly used electron temperature Te([O iii]) from the [O iii]λ4363 auroral line and a traditional Te([O ii]) – Te([O iii]) calibration. The second method applies a recent empirical correction to the O+ abundance from the [O iii]/[O ii] strong-line ratio. The third method infers the Te([O ii]) from the [S ii]λλ4069,76 auroral lines. The first method favours a positive metallicity gradient along SAMI609396B, whereas the second and third methods yield flattened gradients. Strong-line diagnostics produce mostly flat gradients, albeit with unquantified contamination from shocked regions. We conclude that overlooked assumptions about the internal temperature structure of H ii regions in the direct method can lead to large discrepancies in metallicity gradient studies. Our detailed analysis of SAMI609396B underlines that high-accuracy metallicity gradient measurements require a wide array of emission lines and improved spatial resolutions in order to properly constrain excitation sources, physical conditions, and temperature structures of the emitting gas. Integral-field spectroscopic studies with future facilities such as JWST/NIRSpec and ground-based ELTs will be crucial in minimising systematic effects on measured gradients in distant galaxies.

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Exploration of the high-redshift universe enabled by THESEUS

Experimental Astronomy ◽

10.1007/s10686-021-09778-w ◽

2021 ◽

Author(s):

N. R. Tanvir ◽

E. Le Floc’h ◽

L. Christensen ◽

J. Caruana ◽

R. Salvaterra ◽

...

Keyword(s):

Star Formation ◽

Gamma Ray ◽

High Redshift ◽

Formation Rate ◽

Star Forming ◽

Chemical Enrichment ◽

Long Duration ◽

Absorption Studies ◽

Population Iii Stars ◽

High Redshift Universe

AbstractAt peak, long-duration gamma-ray bursts are the most luminous sources of electromagnetic radiation known. Since their progenitors are massive stars, they provide a tracer of star formation and star-forming galaxies over the whole of cosmic history. Their bright power-law afterglows provide ideal backlights for absorption studies of the interstellar and intergalactic medium back to the reionization era. The proposed THESEUS mission is designed to detect large samples of GRBs at z > 6 in the 2030s, at a time when supporting observations with major next generation facilities will be possible, thus enabling a range of transformative science. THESEUS will allow us to explore the faint end of the luminosity function of galaxies and the star formation rate density to high redshifts; constrain the progress of re-ionisation beyond $z\gtrsim 6$ z ≳ 6 ; study in detail early chemical enrichment from stellar explosions, including signatures of Population III stars; and potentially characterize the dark energy equation of state at the highest redshifts.

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Gamma‐Ray Bursts as a Probe of the Very High Redshift Universe

The Astrophysical Journal ◽

10.1086/308918 ◽

2000 ◽

Vol 536 (1) ◽

pp. 1-18 ◽

Cited By ~ 309

Author(s):

Donald Q. Lamb ◽

Daniel E. Reichart

Keyword(s):

Gamma Ray ◽

High Redshift ◽

Gamma Ray Bursts ◽

High Redshift Universe ◽

Very High

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Semi-Analytic Galaxy Formation: Understanding the High Redshift Universe

QSO Hosts and Their Environments ◽

10.1007/978-1-4615-0695-9_50 ◽

2001 ◽

pp. 295-306

Author(s):

C. M. Baugh ◽

A. J. Benson ◽

S. Cole ◽

C. S. Frenk ◽

C. G. Lacey

Keyword(s):

Galaxy Formation ◽

High Redshift ◽

High Redshift Universe

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GRB afterglows: Dust extinction properties from the low to high redshift universe

Planetary and Space Science ◽

10.1016/j.pss.2016.08.010 ◽

2016 ◽

Vol 133 ◽

pp. 14-16 ◽

Cited By ~ 2

Author(s):

Tayyaba Zafar

Keyword(s):

High Redshift ◽

Dust Extinction ◽

High Redshift Universe

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The Lyman-α‎ Line as a Probe of the Early Universe

The First Galaxies in the Universe ◽

10.23943/princeton/9780691144917.003.0011 ◽

2013 ◽

Author(s):

Abraham Loeb ◽

Steven R. Furlanetto

Keyword(s):

Simple Model ◽

High Redshift ◽

Young Star ◽

H Ii Regions ◽

Host Galaxies ◽

Star Forming ◽

Starting Point ◽

Good Starting Point ◽

High Redshift Universe

This chapter investigates a number of specific observational probes of the high-redshift Universe. It examines the Lyman-α‎ line, an extraordinarily rich and useful—albeit complex—probe of both galaxies and the intergalactic medium (IGM). As established in the previous chapter, young star-forming galaxies can produce very bright Lyman-α‎ emissions. Although the radiative transfer of these photons through their host galaxies is typically very complex, a good starting point is a simple model in which a fraction of stellar ionizing photons are absorbed within their source galaxy, forming embedded H II regions. The resulting protons and electrons then recombine, producing Lyman-α‎ photons. Assuming ionization equilibrium, the rate of these recombinations must equal the rate at which ionizing photons are produced.

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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

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1120 ◽

2019 ◽

Vol 486 (3) ◽

pp. 4377-4397 ◽

Cited By ~ 9

Author(s):

Jens-Kristian Krogager ◽

Johan P U Fynbo ◽

Palle Møller ◽

Pasquier Noterdaeme ◽

Kasper E Heintz ◽

...

Keyword(s):

Mass Density ◽

High Redshift ◽

Target Selection ◽

Neutral Hydrogen ◽

Sloan Digital Sky Survey ◽

Selection Probability ◽

Optical Extinction ◽

Neutral Gas ◽

High Redshift Universe ◽

The Impact

ABSTRACT We present a systematic study of the impact of a dust bias on samples of damped Ly α absorbers (DLAs). This bias arises as an effect of the magnitude and colour criteria utilized in the Sloan Digital Sky Survey (SDSS) quasar target selection up until data release 7 (DR7). The bias has previously been quantified assuming only a contribution from the dust obscuration. In this work, we apply the full set of magnitude and colour criteria used up until SDSS-DR7 in order to quantify the full impact of dust biasing against dusty and metal-rich DLAs. We apply the quasar target selection algorithm on a modelled population of intrinsic colours, and by exploring the parameter space consisting of redshift, ($z_{\rm{\small QSO}}$and zabs), optical extinction, and H i column density, we demonstrate how the selection probability depends on these variables. We quantify the dust bias on the following properties derived for DLAs at z ≈ 3: the incidence rate, the mass density of neutral hydrogen and metals, and the average metallicity. We find that all quantities are significantly affected. When considering all uncertainties, the mass density of neutral hydrogen is underestimated by 10–50 per cent, and the mass density in metals is underestimated by 30–200 per cent. Lastly, we find that the bias depends on redshift. At redshift z = 2.2, the mass density of neutral hydrogen and metals might be underestimated by up to a factor of 2 and 5, respectively. Characterizing such a bias is crucial in order to accurately interpret and model the properties and metallicity evolution of absorption-selected galaxies.

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