Evolution of the Intergalactic Medium and UV Background Radiation

Publications of the Astronomical Society of Japan

Okoshi, Katsuya¹  Ikeuchi, Satoru¹ 

[1] Department of Earth and Space Science,Faculty of Science, Osaka University, Machikaneyama-cho, Toyonaka, Osaka 560

关键词: Cosmology;    "Early universe";    "Galaxies : intergalactic medium";    Quasars;   

DOI  :  10.1093/pasj/48.3.441

学科分类：天文学(综合)

来源: Oxford University Press

【 摘 要 】

TheabsenceofanHIGunn-PetersontroughextendingtothebluesideoftheLymanαemissioninthespectraofhigh-redshiftquasarshasplacedaseverelimitonthedensityofneutralhydrogenintheintergalacticmedium.Inaddition,aprobabledetectionofaHeIIGunn-Petersontroughhasbeenreported,thoughitiscontroversial.Ontheotherhand,numerousandnarrowabsorptionlinesinquasarspectrahavebeeninterpretedastheso-calledLymanαforest.TheywouldplayanimportantroleinrelationtotheevolutionoftheUVbackgroundradiationathighredshifts.WecalculatetheevolutionoftheUVbackgroundradiation,andexploretheionizationstatesofintergalacticgasandcloudswhiletryingtosolveanymutualrelationsamongthemconsistently.WeexaminetwosuchmodelsfortheLymanαcloudsaspressure-confinedandforthecloudsconfinedbycolddarkmatter,theminihalos.Fortheformer,theevolutionisnotconsistentwithotherobservationalconstraints,becausethesecloudswithlowHIcolumndensitiesevolvetoorapidlytobemissedindetectionatlowredshifts,z≲2,contrarytotheHSTobservationsthatmorenumerousLymanαabsorptionlinesexistthanpredictedbyextrapolationfromhighredshift.Otherwise,theminihaloscannotreproducetheevolutionoftheLyαforestathighredshiftsifassumedthattheevolutionoftheUVbackgroundisproportionaltothenumberofQSOs.Consequently,weproposeatwo-componentmodel:pressure-confinedcloudsathighredshiftsandminihalosatlowredshifts,whilesatisfyingalloftheobservationalconstraintsmarginallywithinresonableparameters.

【 授权许可】

Unknown