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dc.contributor.authorWitstok, Jorisen
dc.contributor.authorSmit, Renskeen
dc.contributor.authorMaiolino, Robertoen
dc.contributor.authorCurti, Mirkoen
dc.contributor.authorLaporte, Nicolasen
dc.contributor.authorMassey, Richarden
dc.contributor.authorRichard, Johanen
dc.contributor.authorSwinbank, Marken
dc.date.accessioned2021-09-13T23:31:18Z
dc.date.available2021-09-13T23:31:18Z
dc.date.issued2021-10-06en
dc.identifier.issn0035-8711
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/327948
dc.description.abstractWe 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 {\AA} 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 {\AA} 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 {\AA}, 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 $\mathit{JWST}$/ELT era.
dc.languageenen
dc.publisherOxford University Press
dc.rightsAttribution 4.0 International
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/
dc.titleAssessing the sources of reionization: a spectroscopic case study of a 30× lensed galaxy at z ∼ 5 with Lyα, C iv, Mg ii, and [Ne iii]en
dc.typeArticle
prism.endingPage1700
prism.issueIdentifier2en
prism.publicationDate2021en
prism.publicationNameMonthly Notices of the Royal Astronomical Societyen
prism.startingPage1686
prism.volume508en
dc.identifier.doi10.17863/CAM.75401
dcterms.dateAccepted2021-09-07en
rioxxterms.versionofrecord10.1093/mnras/stab2591en
rioxxterms.versionVoR
rioxxterms.licenseref.urihttp://www.rioxx.net/licenses/all-rights-reserveden
rioxxterms.licenseref.startdate2021-10-06en
dc.contributor.orcidWitstok, Joris [0000-0002-7595-121X]
dc.contributor.orcidSmit, Renske [0000-0001-8034-7802]
dc.contributor.orcidMaiolino, Roberto [0000-0002-4985-3819]
dc.contributor.orcidCurti, Mirko [0000-0002-2678-2560]
dc.contributor.orcidLaporte, Nicolas [0000-0001-7459-6335]
dc.contributor.orcidMassey, Richard [0000-0002-6085-3780]
dc.contributor.orcidRichard, Johan [0000-0001-5492-1049]
dc.contributor.orcidSwinbank, Mark [0000-0003-1192-5837]
dc.identifier.eissn1365-2966
rioxxterms.typeJournal Article/Reviewen
pubs.funder-project-idSTFC (ST/M001172/1)
pubs.funder-project-idECH2020 EUROPEAN RESEARCH COUNCIL (ERC) (695671)
pubs.funder-project-idFoundation MERAC (Mobilising European Research in Astrophysics and Cosmology) (N/A)
pubs.funder-project-idSTFC (ST/V000918/1)
cam.issuedOnline2021-07-13en
cam.orpheus.successMon Sep 27 07:30:27 BST 2021 - Embargo updated*
cam.orpheus.counter1*
rioxxterms.freetoread.startdate2100-01-01


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Attribution 4.0 International
Except where otherwise noted, this item's licence is described as Attribution 4.0 International