dc.contributor.author Rorai, Alberto en dc.contributor.author Becker, GD en dc.contributor.author Haehnelt, Martin en dc.contributor.author Carswell, RF en dc.contributor.author Bolton, JS en dc.contributor.author Cristiani, S en dc.contributor.author D'Odorico, V en dc.contributor.author Cupani, G en dc.contributor.author Barai, P en dc.contributor.author Calura, F en dc.contributor.author Kim, T-S en dc.contributor.author Pomante, E en dc.contributor.author Tescari, E en dc.contributor.author Viel, M en dc.date.accessioned 2017-02-06T15:27:25Z dc.date.available 2017-02-06T15:27:25Z dc.date.issued 2017-04-01 en dc.identifier.issn 0035-8711 dc.identifier.uri https://www.repository.cam.ac.uk/handle/1810/262333 dc.description.abstract At low densities, the standard ionization history of the intergalactic medium (IGM) predicts a decreasing temperature of the IGM with decreasing density once hydrogen (and helium) reionization is complete. Heating the high-redshift, low-density IGM above the temperature expected from photoheating is difficult, and previous claims of high/rising temperatures in lowdensity regions of the Universe based on the probability density function (PDF) of the opacity in Ly $\alpha$ forest data at 2 < $z$ < 4 have been met with considerable scepticism, particularly since they appear to be in tension with other constraints on the temperature–density relation (TDR). We utilize here an ultrahigh signal-to-noise spectrum of the Quasi-stellar object HE0940-1050 and a novel technique to study the low opacity part of the PDF. We show that there is indeed evidence (at 90 per cent confidence level) that a significant volume fraction of the underdense regions at $z$ ~ 3 has temperatures as high or higher than those at densities comparable to the mean and above. We further demonstrate that this conclusion is nevertheless consistent with measurements of a slope of the TDR in overdense regions that imply a decreasing temperature with decreasing density, as expected if photoheating of ionized hydrogen is the dominant heating process. We briefly discuss implications of our findings for the need to invoke either spatial temperature fluctuations, as expected during helium reionization, or additional processes that heat a significant volume fraction of the low-density IGM. dc.description.sponsorship We thank Volker Springel for making GADGET-3 available. This work made use of the Distributed Research utilising Advanced Computing High Performance Computing System (HPCS) and the COSMOlogy Supercomputer shared memory service at the University of Cambridge. These are operated on behalf of the Science and Technology Facilities Council (STFC) DiRAC HPC facility. This equipment is funded by Department for Business, Innovation and Skills National E-infrastructure capital grant ST/J005673/1 and STFC grants ST/H008586/1, ST/K00333X/1. We acknowledge Partnership for Advanced Computing in Europe for awarding us access to the Curie supercomputer, based in France at the Tres Grand Centre de Calcul (TGCC), through the 8th regular call. Support by the European Research Council Advanced Grant 320596 ‘The Emergence of structure during the epoch of reionization’ is gratefully acknowledged. ET is supported by the Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), through project number CE110001020. AR thanks Joseph F. Hennawi and the ENIGMA group at the Max Planck institute for Astronomy for helpful comments and discussion. MV and TSK acknowledges funding support to the European Research Council Starting Grant ‘Cosmology with the IGM’ through grant GA-257670. PB is supported by the Istituto Nazionale di Astrofisica PRIN-2014 grant ”Windy black holes combing galaxy evolution”. dc.language.iso en en dc.publisher Oxford University Press dc.subject intergalactic medium en dc.subject quasars: absorption lines en dc.title Exploring the thermal state of the low-density intergalactic medium at $z$ = 3 with an ultrahigh signal-to-noise QSO spectrum en dc.type Article prism.endingPage 2709 prism.issueIdentifier 3 en prism.publicationDate 2017 en prism.publicationName Monthly Notices of the Royal Astronomical Society en prism.startingPage 2690 prism.volume 466 en dc.identifier.doi 10.17863/CAM.7593 dcterms.dateAccepted 2016-11-09 en rioxxterms.versionofrecord 10.1093/mnras/stw2917 en rioxxterms.version VoR en rioxxterms.licenseref.uri http://www.rioxx.net/licenses/all-rights-reserved en rioxxterms.licenseref.startdate 2017-04-01 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/stw2917 en rioxxterms.type Journal Article/Review en pubs.funder-project-id STFC (ST/J005673/1) pubs.funder-project-id STFC (ST/K00333X/1) pubs.funder-project-id STFC (ST/M00418X/1) pubs.funder-project-id STFC (ST/M007065/1) pubs.funder-project-id STFC (ST/L000636/1) pubs.funder-project-id European Research Council (320596) pubs.funder-project-id SCIENCE & TECHNOLOGY FACILITIES COUNCIL (ST/N000927/1) pubs.funder-project-id STFC (ST/H008586/1) pubs.funder-project-id STFC (ST/P000673/1) cam.issuedOnline 2016-11-12 en dc.identifier.url http://dx.doi.org/10.1093/mnras/stw2917 en cam.orpheus.success Thu Jan 30 12:57:02 GMT 2020 - The item has an open VoR version. * rioxxterms.freetoread.startdate 2100-01-01
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