Assessing the sources of reionisation: a spectroscopic case study of a 30$\times$ lensed galaxy at $z\sim 5$ with Lyα, CIV, MgII, and [NeIII]

Abstract

We present a detailed spectroscopic analysis of a galaxy at $z\simeq 4.88$ that is, by chance, magnified $\sim 30\times$ by gravitational lensing. Only three sources at $z\gtrsim 5$ are known with such high magnification. This particular source has been shown to exhibit widespread, high equivalent width CIV $\lambda$ 1549 Å emission, implying it is a unique example of a metal-poor galaxy with a hard radiation field, likely representing the galaxy population responsible for cosmic reionisation. Using UV nebular line ratio diagnostics, VLT/X-shooter observations rule out strong AGN activity, indicating a stellar origin of the hard radiation field instead. We present a new detection of [NeIII] $\lambda$ 3870 Å and use the [NeIII]/[OII] line ratio to constrain the ionisation parameter and gas-phase metallicity. Closely related to the commonly used [OIII]/[OII] ratio, our [NeIII]/[OII] measurement shows this source is similar to local "Green Pea" galaxies and Lyman-continuum leakers. It furthermore suggests this galaxy is more metal poor than expected from the Fundamental Metallicity Relation, possibly as a consequence of excess gas accretion diluting the metallicity. Finally, we present the highest redshift detection of MgII $\lambda$ 2796 Å, observed at high equivalent width in emission, in contrast to more evolved systems predominantly exhibiting MgII absorption. Strong MgII emission has been observed in most $z\sim 0$ Lyman-continuum leakers known and has recently been proposed as an indirect tracer of escaping ionising radiation. In conclusion, this strongly lensed galaxy, observed just 300 Myr after reionisation ends, enables testing of observational diagnostics proposed to constrain the physical properties of distant galaxies in the $JWST$/ELT era.

arXiv comment15 pages, 9 figures. Accepted for publication in Monthly Notices of the Royal Astronomical Society

References in corpus (107)

• Astropy: A Community Python Package for Astronomy
• The NumPy array: a structure for efficient numerical computation
• Stellar population synthesis at the resolution of 2003
• The chemical composition of the Sun
• Galactic Stellar and Substellar Initial Mass Function
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The Seventh Data Release of the Sloan Digital Sky Survey
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• Cosmic Star Formation History
• The Origin of the Mass--Metallicity Relation: Insights from 53,000 Star-Forming Galaxies in the SDSS
• Theoretical Modeling of Starburst Galaxies
• The Host Galaxies and Classification of Active Galactic Nuclei
• Rest-Frame Ultraviolet Spectra of z~3 Lyman Break Galaxies
• UV Luminosity Functions at redshifts z~4 to z~10: 10000 Galaxies from HST Legacy Fields
• X-shooter, the new wide band intermediate resolution spectrograph at the ESO Very Large Telescope
• A fundamental relation between mass, SFR and metallicity in local and high redshift galaxies
• An ultra-deep near-infrared spectrum of a compact quiescent galaxy at z=2.2
• AMAZE. I. The evolution of the mass-metallicity relation at z>3
• Molecfit: A general tool for telluric absorption correction. I. Method and application to ESO instruments
• Automated data reduction workflows for astronomy
• De Re Metallica: The cosmic chemical evolution of galaxies
• Ubiquitous outflows in DEEP2 spectra of star-forming galaxies at z=1.4
• The Stellar, Gas and Dynamical Masses of Star-Forming Galaxies at z~2
• Model-independent evidence in favor of an end to reionization by z~6
• Molecfit: A general tool for telluric absorption correction II. Quantitative evaluation on ESO-VLT X-Shooter spectra
• The 2013 Release of Cloudy
• Reconciling the Stellar and Nebular Spectra of High Redshift Galaxies
• The Mass-Metallicity and the Fundamental Metallicity Relation revisited on a fully Te-based abundance scale for galaxies
• SINFONI - Integral Field Spectroscopy at 50 milli-arcsecond resolution with the ESO VLT
• Gas metallicity diagnostics in star-forming galaxies
• The Universe is Reionizing at z~7: Bayesian Inference of the IGM Neutral Fraction Using Ly$\alpha$ Emission from Galaxies
• Lyman-alpha and CIII] Emission in z=7-9 Galaxies: Accelerated Reionization Around Luminous Star Forming Systems?
• Detection of high Lyman continuum leakage from four low-redshift compact star-forming galaxies
• Modelling the nebular emission from primeval to present-day star-forming galaxies
• Nuclear activity versus star formation: emission-line diagnostics at ultraviolet and optical wavelengths
• Low-redshift Lyman continuum leaking galaxies with high [OIII]/[OII] ratios
• The Relation Between SFR and Stellar Mass for Galaxies at 3.5 $\le z\le$ 6.5 in CANDELS
• The MOSDEF Survey: Electron Density and Ionization Parameter at $z\sim 2.3$
• New Strong Line Abundance Diagnostics for \HII Regions: Effects of $\kappa$-Distributed Electron Energies and New Atomic Data
• Evidence for Ubiquitous, High-EW Nebular Emission in z~7 Galaxies: Towards a Clean Measurement of the Specific Star Formation Rate using a Sample of Bright, Magnified Galaxies
• Lyman Alpha Emitting Galaxies as a Probe of Reionization
• Lyman continuum leaking from the compact star-forming dwarf galaxy J0925+1403
• The MOSDEF Survey: The Evolution of the Mass-Metallicity Relation from $z=0$ to $z\sim 3.3$
• Line Emitting Galaxies Beyond a Redshift of 7: An Improved Method for Estimating the Evolving Neutrality of the Intergalactic Medium
• Metallicity evolution, metallicity gradients and gas fractions at z~3.4
• Spectroscopic detection of CIV in a galaxy at z=7.045: Implications for the ionizing spectra of reionization-era galaxies
• The Origin and Optical Depth of Ionizing Radiation in the "Green Pea" Galaxies
• J1154+2443: a low-redshift compact star-forming galaxy with a 46 per cent leakage of Lyman continuum photons
• A Pair of Lensed Galaxies at z=4.92 in the Field of CL1358+62
• The KMOS Redshift One Spectroscopic Survey (KROSS): Dynamical properties, gas and dark matter fractions of typical z~1 star-forming galaxies
• Lyman-alpha spectral properties of five newly discovered Lyman continuum emitters
• The Persistence of Cool Galactic Winds in High Stellar Mass Galaxies Between z~1.4 and ~1
• Ly$\alpha$ profile, dust, and prediction of Ly$\alpha$ escape fraction in Green Pea Galaxies
• Hubble imaging of the ionizing radiation from a star-forming galaxy at z=3.2 with fesc>50%
• AGN Emission Line Diagnostics and the Mass-Metallicity Relation up to Redshift z~2: the Impact of Selection Effects and Evolution
• An extreme [OIII] emitter at $z=3.2$: a low metallicity Lyman continuum source
• A fundamental relation between the metallicity, gas content, and stellar mass of local galaxies
• Ultraviolet spectra of extreme nearby star-forming regions --- approaching a local reference sample for JWST
• High-precision Photometric Redshifts from Spitzer/IRAC: Extreme [3.6]-[4.5] Colors Identify Galaxies in the Redshift Range z~6.6-6.9
• Galactic Outflows in Absorption and Emission: Near-UV Spectroscopy of Galaxies at 1<z<2
• What is the physical origin of strong Lya emission? II. Gas Kinematics and Distribution of Lya Emitters
• The Chemical Evolution of Carbon, Nitrogen, and Oxygen in Metal-Poor Dwarf Galaxies
• "Direct" Gas-Phase Metallicity in Local Analogs of High-Redshift Galaxies: Empirical Metallicity Calibrations for High-Redshift Star-Forming Galaxies
• Gravitationally Lensed Galaxies at 2<z<3.5: Direct Abundance Measurements of Lya Emitters
• Evidence for a Hard Ionizing Spectrum from a z=6.11 Stellar Population
• KMOS^3D: Dynamical constraints on the mass budget in early star-forming disks
• A spectroscopic search for AGN activity in the reionization era
• CANDELSz7: a large spectroscopic survey of CANDELS galaxies in the reionization epoch
• The origin of the escape of Lyman alpha and ionizing photons in Lyman Continuum Emitters
• Ionising the Intergalactic Medium by Star Clusters: The first empirical evidence
• Green Pea Galaxies Reveal Secrets of Ly$\alpha$ Escape
• Low-ionization Line Emission from Starburst Galaxies: A New Probe of Galactic-Scale Outflows
• Theoretical ISM pressure and electron density diagnostics for local and high-redshift galaxies
• A young star-forming galaxy at z = 3.5 with an extended Ly\,$\alpha$ halo seen with MUSE
• Chemical Abundances and Ionizing Clusters of HII Regions in the LINER Galaxy NGC 4258
• The impact of stars stripped in binaries on the integrated spectra of stellar populations
• Fundamental metallicity relation in CALIFA, SDSS-IV MaNGA and high-z galaxies
• The Low Mass End of the Fundamental Relation for Gravitationally Lensed Star Forming Galaxies at 1<z<6
• A Spatially Resolved Map of the Kinematics, Star-Formation and Stellar Mass Assembly in a Star-Forming Galaxy at z=4.9
• Optically-Thin Spatially-Resolved Mg II Emission Maps the Escape of Ionizing Photons
• Neon and Argon optical emission lines in ionized gaseous nebulae: Implications and applications
• Resolved Spectroscopy of a Gravitationally Lensed L* Lyman-break Galaxy at z~5
• Intense CIV and HeII Emission in z~0 Galaxies: Probing High-Energy Ionizing Photons
• A Close Relationship between Lyman Alpha and Mg II in Green Pea Galaxies
• Synthetic nebular emission from massive galaxies II: ultraviolet-line diagnostics of dominant ionizing sources
• Extremely metal-poor galaxies with HST/COS: laboratories for models of low-metallicity massive stars and high-redshift galaxies
• The X-SHOOTER Lyman-$\alpha$ survey at z=2 (XLS-z2) I: What makes a galaxy a Lyman-$\alpha$ emitter?
• Near-Infrared Spectroscopy of Galaxies During Reionization: Measuring CIII] in a Galaxy at $\mathbf{z}=7.5$
• Molecular gas as the driver of fundamental galactic relations
• Galaxy metallicities depend primarily on stellar mass and molecular gas mass
• [NeIII]/[OII] as an Ionization Parameter Diagnostic in Star-Forming Galaxies
• Discovery Of Cold, Pristine Gas Possibly Accreting Onto An Overdensity Of Star-Forming Galaxies At Redshift z ~ 1.6
• Spatially Resolved Galactic Wind in Lensed Galaxy RCSGA 032727-132609
• The MUSE Hubble Ultra Deep Field Survey: XII. MgII emission and absorption in star-forming galaxies
• Fine-Structure FeII* Emission and Resonant MgII Emission in z = 1 Star-Forming Galaxies
• A gravitationally-boosted MUSE survey for emission-line galaxies at z>~5 behind the massive cluster RCS 0224
• Emission Line Properties of Seyfert Galaxies in the 12 Micron Sample
• The MUSE Hubble Ultra Deep Field Survey: VII. FeII* Emission in Star-Forming Galaxies
• HST Emission Line Galaxies at z ~ 2: The Mystery of Neon
• Properties of five z~0.3-0.4 confirmed LyC leakers: VLT/XShooter observations
• Star Formation in Emission-Line Galaxies Between Redshifts of 0.8 and 1.6
• The MOSDEF Survey: Neon as a Probe of ISM Physical Conditions at High Redshift
• The MOSDEF Survey: First Measurement of Nebular Oxygen Abundance at $z>4$
• CASSOWARY 20: a Wide Separation Einstein Cross Identified with the X-shooter Spectrograph
• A highly-ionized region surrounding SN Refsdal revealed by MUSE
• On the lack of correlation between Mg II 2796, 2803 Angstrom and Lyman alpha emission in lensed star-forming galaxies
• COOL-LAMPS I. An Extraordinarily Bright Lensed Galaxy at Redshift 5.04

Cited by in corpus (25)

• JADES NIRSpec Spectroscopy of GN-z11: Lyman-$\alpha$ emission and possible enhanced nitrogen abundance in a $z=10.60$ luminous galaxy
• The chemical enrichment in the early Universe as probed by JWST via direct metallicity measurements at z~8
• The Far-Ultraviolet Continuum Slope as a Lyman Continuum Escape Estimator at High-redshift
• Nitrogen enhancements 440 Myr after the Big Bang: super-solar N/O, a tidal disruption event or a dense stellar cluster in GN-z11?
• Dual constraints with ALMA: new [O III] 88 $\mu$m and dust-continuum observations reveal the ISM conditions of luminous LBGs at $z\sim 7$
• New AGN diagnostic diagrams based on the [OIII]$\lambda 4363$ auroral line
• Witnessing the onset of reionisation via Lyman-$\alpha$ emission at redshift 13
• JWST FRESCO: a comprehensive census of H$\beta$+[OIII] emitters at 6.8<z<9.0 in the GOODS fields
• JWST/NIRSpec Measurements of the Relationships Between Nebular Emission-line Ratios and Stellar Mass at z~3-6
• JADES: Primaeval Lyman-$\alpha$ emitting galaxies reveal early sites of reionisation out to redshift $z\sim 9$
• Strong C IV emission from star-forming galaxies: a case for high Lyman continuum photon escape
• Lyman alpha and Lyman continuum emission of MgII-selected star-forming galaxies
• Seeing sharper and deeper: JWST's first glimpse of the photometric and spectroscopic properties of galaxies in the epoch of reionisation
• The Dual Nature of GHZ9: Coexisting Active Galactic Nuclei and Star Formation Activity in a Remote X-ray Source at z = 10.145
• The Low-Redshift Lyman Continuum Survey: Optically Thin and Thick Mg II Lines as Probes of Lyman Continuum Escape
• Metal-Enriched Neutral Gas Reservoir around a Strongly-lensed, Low-mass Galaxy at $z=4$ Identified by JWST/NIRISS and VLT/MUSE
• Classifying Intermediate Redshift Galaxies in SDSS: Alternative Diagnostic Diagrams
• UNCOVERing the High-redshift AGN Population among Extreme UV Line Emitters
• MOSEL Survey: Extremely weak outflows in EoR analogues at z=3-4
• JADES -- The small blue bump in GN-z11: insights into the nuclear region of a galaxy at z=10.6
• Understanding the spatial variation of \ion{Mg}{II} and ionizing photon escape in a local LyC leaker
• GA-NIFS: Dissecting the multiple sub-structures and probing their complex interactions in the \Lyalpha emitter galaxy CR7 at z = 6.6 with JWST/NIRSpec
• Galaxy Spectra neural Networks (GaSNets). I. Searching for strong lens candidates in eBOSS spectra using Deep Learning
• The Neon Gap: Probing Ionization with Dwarf Galaxies at z~1
• Unraveling the Lyman Continuum Emission of Ion3: Insights from HST multi-band imaging and X-Shooter spectroscopy