Please use this identifier to cite or link to this item:
http://hdl.handle.net/20.500.12386/23397
DC Field | Value | Language |
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dc.contributor.author | HAARDT, FRANCESCO | en_US |
dc.contributor.author | SALVATERRA, Ruben | en_US |
dc.date.accessioned | 2020-03-19T15:14:29Z | - |
dc.date.available | 2020-03-19T15:14:29Z | - |
dc.date.issued | 2015 | en_US |
dc.identifier.issn | 0004-6361 | en_US |
dc.identifier.uri | http://hdl.handle.net/20.500.12386/23397 | - |
dc.description | We thank A. Comastri, P. Madau, A. Moretti for many fruitful discussions, and E. Giallongo for allowing us to use their results before publication. | en |
dc.description.abstract | The rapidly declining population of bright quasars at z ≳ 3 appears to make an increasingly smaller contribution to the ionising background at the H I Lyman limit. It is thererfore generally thought that massive stars in (pre-)Galactic systems may provide the additional ionising flux needed to complete H I reionisation by z ≳ 6. A galaxy-dominated background, however, may require that the escape fraction of Lyman continuum radiation from high-redshift galaxies is as high as 10%, which is somewhat at odds with (admittedly scarce) observational constraints. High escape fractions from dwarf galaxies have been advocated, or, alternatively, a so-far undetected (or barely detected) population of unobscured, high-redshift faint AGNs. Here we examine the latter hypothesis and show that such sources, to be consistent with the measured level of the unresolved X-ray background at z = 0, can provide a fraction of the H II filling factor no larger than 13% by z ≃ 6. The fraction rises to ≲27% in the somewhat extreme case of a constant comoving redshift evolution of the AGN emissivity. This still calls for a mean escape fraction of ionising photons from high-z galaxies of ≳10%. <P /> | en_US |
dc.language.iso | eng | en_US |
dc.title | High-redshift active galactic nuclei and H I reionisation: limits from the unresolved X-ray background | en_US |
dc.type | Article | - |
dc.identifier.doi | 10.1051/0004-6361/201525627 | en_US |
dc.identifier.scopus | 2-s2.0-84924589103 | en_US |
dc.identifier.isi | 000360710400033 | en_US |
dc.identifier.url | https://www.aanda.org/articles/aa/abs/2015/03/aa25627-15/aa25627-15.html | en_US |
dc.relation.medium | STAMPA | en_US |
dc.relation.volume | 575 | en_US |
dc.relation.firstpage | L16 | en_US |
dc.type.referee | REF_1 | en_US |
dc.description.international | no | en_US |
dc.relation.scientificsector | FIS/05 - ASTRONOMIA E ASTROFISICA | en_US |
dc.relation.journal | ASTRONOMY & ASTROPHYSICS | en_US |
dc.type.miur | 262 Articolo in rivista | - |
dc.identifier.adsbibcode | 2015A&A...575L..16H | en_US |
dc.description.apc | no | en_US |
dc.description.oa | 1 – prodotto con file in versione Open Access (allegherò il file al passo 5-Carica) | en_US |
item.grantfulltext | open | - |
item.openairecristype | http://purl.org/coar/resource_type/c_18cf | - |
item.fulltext | With Fulltext | - |
item.languageiso639-1 | en | - |
item.openairetype | Article | - |
item.cerifentitytype | Publications | - |
crisitem.journal.journalissn | 0004-6361 | - |
crisitem.journal.ance | E016240 | - |
crisitem.author.dept | IASF Milano | - |
crisitem.author.orcid | 0000-0002-9393-8078 | - |
Appears in Collections: | 1.01 Articoli in rivista |
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File | Description | Size | Format | |
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aa25627-15.pdf | 171.04 kB | Adobe PDF | View/Open |
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