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The synchrony of pr...
The synchrony of production and escape : half the bright Lyα emitters at z ≈ 2 have Lyman continuum escape fractions ≈50 per cent
- Article/chapterEnglish2022
Publisher, publication year, extent ...
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2021-12-11
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Oxford University Press (OUP),2022
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printrdacarrier
Numbers
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LIBRIS-ID:oai:DiVA.org:su-203961
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https://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-203961URI
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https://doi.org/10.1093/mnras/stab3601DOI
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Language:English
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Summary in:English
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Subject category:ref swepub-contenttype
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Subject category:art swepub-publicationtype
Notes
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The ionizing photon escape fraction [Lyman continuum (LyC) fesc] of star-forming galaxies is the single greatest unknown in the reionization budget. Stochastic sightline effects prohibit the direct separation of LyC leakers from non-leakers at significant redshifts. Here we circumvent this uncertainty by inferring fesc using resolved (R > 4000) Lyman α (Lyα) profiles from the X-SHOOTER Lyα survey at z = 2 (XLS-z2). With empirically motivated criteria, we use Lyα profiles to select leakers (fesc>20 per centfesc>20 per cent) and non-leakers (fesc<5 per centfesc<5 per cent) from a representative sample of >0.2L* Lyman α emitters (LAEs). We use median stacked spectra of these subsets over λrest ≈ 1000–8000 Å to investigate the conditions for LyC fesc. Our stacks show similar mass, metallicity, MUV, and βUV. We find the following differences between leakers versus non-leakers: (i) strong nebular C IV and He II emission versus non-detections; (ii) [O III]/[O II] ≈ 8.5 versus ≈3; (iii) Hα/Hβ indicating no dust versus E(B − V) ≈ 0.3; (iv) Mg II emission close to the systemic velocity versus redshifted, optically thick Mg II; and (v) Lyα fesc of ≈50 per cent≈50 per cent versus ≈10 per cent≈10 per cent. The extreme equivalent widths (EWs) in leakers ([O III]+Hβ≈1100Hβ≈1100 Å rest frame) constrain the characteristic time-scale of LyC escape to ≈3–10 Myr bursts when short-lived stars with the hardest ionizing spectra shine. The defining traits of leakers – extremely ionizing stellar populations, low column densities, a dust-free, high-ionization state interstellar medium (ISM) – occur simultaneously in the fesc>20 per centfesc>20 per cent stack, suggesting they are causally connected, and motivating why indicators like [O III]/[O II] may suffice to constrain fesc at z > 6 with the James Webb Space Telescope (JWST). The leakers comprise half of our sample, have a median LyCfesc≈50 per centfesc≈50 per cent (conservative range: 20−55 per cent20−55 per cent), and an ionizing production efficiency log(ξion/Hz erg−1)≈25.9log(ξion/Hz erg−1)≈25.9 (conservative range: 25.7–25.9). These results show LAEs – the type of galaxies rare at z ≈ 2, but that become the norm at higher redshift – are highly efficient ionizers, with extreme ξion and prolific fesc occurring in sync.
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Matthee, Jorryt
(author)
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Oesch, Pascal A.
(author)
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Conroy, Charlie
(author)
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Sobral, David
(author)
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Pezzulli, Gabriele
(author)
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Hayes, Matthew J.Stockholms universitet,Institutionen för astronomi,Oskar Klein-centrum för kosmopartikelfysik (OKC)(Swepub:su)mhaye
(author)
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Erb, Dawn
(author)
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Amorín, Ricardo
(author)
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Gronke, Max
(author)
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Schaerer, Daniel
(author)
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Tacchella, Sandro
(author)
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Kerutt, Josephine
(author)
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Paulino-Afonso, Ana
(author)
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Calhau, João
(author)
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Llerena, Mario
(author)
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Rottgering, Huub
(author)
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Stockholms universitetInstitutionen för astronomi
(creator_code:org_t)
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In:Monthly notices of the Royal Astronomical Society: Oxford University Press (OUP)510:3, s. 4582-46070035-87111365-2966
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Naidu, Rohan P.
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Matthee, Jorryt
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Oesch, Pascal A.
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Conroy, Charlie
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Sobral, David
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Pezzulli, Gabrie ...
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Hayes, Matthew J ...
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Erb, Dawn
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Amorín, Ricardo
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Gronke, Max
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Schaerer, Daniel
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Tacchella, Sandr ...
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Kerutt, Josephin ...
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Paulino-Afonso, ...
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Calhau, João
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Llerena, Mario
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Rottgering, Huub
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- NATURAL SCIENCES
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Stockholm University