dc.contributor.author Chardin, Jonathan en dc.contributor.author Puchwein, Ewald en dc.contributor.author Haehnelt, Martin en dc.date.accessioned 2017-03-28T12:35:59Z dc.date.available 2017-03-28T12:35:59Z dc.date.issued 2017-03-01 en dc.identifier.issn 0035-8711 dc.identifier.uri https://www.repository.cam.ac.uk/handle/1810/263280 dc.description.abstract Ly$\alpha$ forest data probing the post-reionization Universe show surprisingly large opacity fluctuations over rather large (≥50 $h^{−1}$ comoving Mpc) spatial scales. We model these fluctuations using a hybrid approach utilizing the large-volume Millennium simulation to predict the spatial distribution of QSOs combined with smaller scale full hydrodynamical simulation performed with $\small \text{RAMSES}$ and post-processed with the radiative transfer code $\small \text{ATON}$. We produce realistic mock absorption spectra that account for the contribution of galaxies and QSOs to the ionizing UV background. These improved models confirm our earlier findings that a significant ($\gtrsim$50 per cent) contribution of ionizing photons from QSOs can explain the large reported opacity fluctuations on large scales. The inferred QSO luminosity function is thereby consistent with recent estimates of the space density of QSOs at this redshift. Our simulations still somewhat struggle, however, to reproduce the very long (110 $h^{−1}$ comoving Mpc) high-opacity absorption through observed in ULAS J0148+0600, perhaps suggesting an even later end of reionization than assumed in our previously favoured model. Medium-deep/medium area QSO surveys as well as targeted searches for the predicted strong transverse QSO proximity effect would illuminate the origin of the observed large-scale opacity fluctuations. They would allow us to substantiate whether UV fluctuations due to QSO are indeed primarily responsible, or whether significant contributions from other recently proposed mechanisms such as large-scale fluctuations in temperature and mean free path (even in the absence of rare bright sources) are required. dc.description.sponsorship This work was supported by the ERC Advanced Grant 320596 ‘The Emergence of Structure during the epoch of Reionization’. This work was performed using the COSMOS and Darwin Supercomputers of the University of Cambridge High Performance Computing Service (http://www.hpc.cam.ac.uk/), provided by Dell Inc. using Strategic Research Infrastructure Funding from the Higher Education Funding Council for England and funding from the Science and Technology Facilities Council. This work furthermore used the Wilkes GPU cluster at the University of Cambridge High Performance Computing Service (http://www.hpc.cam.ac.uk/), provided by Dell Inc., NVIDIA and Mellanox, and part funded by STFC with industrial sponsorship from Rolls Royce and Mitsubishi Heavy Industries. Some of the hydrodynamical simulations used in this work were performed with supercomputer time awarded by the Partnership for Advanced Computing in Europe (PRACE) 8th Call. We acknowledge PRACE for enabling access to the Curie supercomputer, based in France at the Tres Grand Centre de Calcul (TGCC). EP acknowledges support by ` the Kavli foundation. The research of JC and MH was supported by the Munich Institute for Astro- and Particle Physics (MIAPP) of the DFG cluster of excellence ‘Origin and Structure of the Universe’. dc.language.iso en en dc.publisher Oxford University Press dc.subject methods: numerical en dc.subject galaxies: evolution en dc.subject quasars: general en dc.subject cosmology: theory en dc.subject diffuse radiation en dc.title Large-scale opacity fluctuations in the Ly$\alpha$ forest: evidence for QSOs dominating the ionizing UV background at $z$ ~ 5.5–6? en dc.type Article prism.endingPage 3445 prism.issueIdentifier 3 en prism.publicationDate 2017 en prism.publicationName Monthly Notices of the Royal Astronomical Society en prism.startingPage 3429 prism.volume 465 en dc.identifier.doi 10.17863/CAM.8602 dcterms.dateAccepted 2016-11-11 en rioxxterms.versionofrecord 10.1093/mnras/stw2943 en rioxxterms.version VoR en rioxxterms.licenseref.uri http://www.rioxx.net/licenses/all-rights-reserved en rioxxterms.licenseref.startdate 2017-03-01 en dc.contributor.orcid Haehnelt, Martin [0000-0001-8443-2393] dc.identifier.eissn 1365-2966 dc.publisher.url http://dx.doi.org/10.1093/mnras/stw2943 en rioxxterms.type Journal Article/Review en pubs.funder-project-id SCIENCE & TECHNOLOGY FACILITIES COUNCIL (ST/N000927/1) pubs.funder-project-id STFC (ST/J005673/1) pubs.funder-project-id STFC (ST/K00333X/1) pubs.funder-project-id STFC (ST/M007065/1) pubs.funder-project-id European Research Council (320596) pubs.funder-project-id STFC (ST/P000673/1) pubs.funder-project-id STFC (ST/L000636/1) cam.issuedOnline 2016-11-17 en cam.orpheus.success Thu Jan 30 12:53:33 GMT 2020 - The item has an open VoR version. * rioxxterms.freetoread.startdate 2100-01-01
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