The redshift distribution of absorption-line syste

arXiv:astro-ph/0703277v112Mar2007Mon.Not.R.Astron.Soc.000,1–??(2007)PrintedFebruary5,2008(MNLATEXstylefilev2.2)Theredshiftdistributionofabsorption-linesystemsinQSOspectraA.I.Ryabinkov,A.D.Kaminker⋆,andD.A.VarshalovichIoffePhysico-TechnicalInstitute,Politekhnicheskaya26,194021St.Petersburg,Russia,e-mail:[e-mail],[kam,varsh]@astro.ioffe.ruAcceptedbyMNRAS2006January30.Received2006December5;inoriginalform2006April6ABSTRACTAstatisticalanalysisofthespace-timedistributionofabsorption-linesys-tems(ALSs)observedinQSOspectrawithinthecosmologicalredshiftin-tervalz=0.0–3.7iscarriedoutonthebaseofourcatalogofabsorptionsystems(Ryabinkovetal.2003).Weconfirmourpreviousconclusionthatthez-distributionofabsorbingmattercontainsnon-uniformcomponentdis-playingapatternofstatisticallysignificantalternatingmaxima(peaks)andminima(dips).Usingthewavelettransformationwedeterminethepositionsofthemaximaandminimaandestimatetheirstatisticalsignificance.Thepo-sitionsofthemaximaandminimaofthez-distributionsobtainedfordifferentcelestialhemispheresturnouttobeweaklysensitivetoorientationsofthehemispheres.Thedatarevealaregularity(quasi-periodicity)ofthesequenceofthepeaksanddipswithrespecttosomerescalingfunctionsofz.Thesameperiodicitywasfoundfortheone-dimensionalcorrelationfunctioncalculatedforthesampleoftheALSsunderinvestigation.Weassumetheexistenceofaregularstructureinthedistributionofabsorptionmatter,whichisnotonlyspatialbutalsotemporalinnaturewithcharacteristictimevaryingwithintheinterval150–650Myrforthecosmologicalmodelapplied.Keywords:galaxies:high-redshift–quasars:absorptionlines.⋆Sendoffprintrequestto:A.D.Kaminker2A.I.Ryabinkov,A.D.Kaminker,D.A.VarshalovichredshiftzNAS00.40.81.21.622.42.83.23.640204060802003ALS847ALSFigure1.z-distributionsofabsorption-linesystemsobservedinQSOspectrawithintheredshiftintervalz=0.0–3.7:(i)847systemsaretakenfromthecataloguebyJunkkarinenetal.(1991)and(ii)2003systems–fromthecataloguebyRyabinkovetal.(2003)(seetext).1INTRODUCTIONWecontinueourpreviousstudies(e.g.,Kaminker,Ryabinkov&Varshalovich2000,here-afterPaperI)ofthespace-timedistributionofabsorption-linesystems(ALSs)imprintedinspectraofquasars(QSOs).Actually,ALSscontainbasicinformationonthedistribu-tionofmatterbetweentheobserverandQSOsaswellasonphysicalprocessesoccurredindifferentepochsofthecosmologicalevolution.Inthefirststage(e.g.,PaperI)weusedasindicatorsofmatteronlydataontheresonanceabsorptiondoubletsofCIVandMgIIobservedinQSOspectraatcosmologicalredshiftsz=0.2−3.2payingspecialattentiontodiminishingofpossibleselectioneffects.Then,weexploredconsiderablylargernumberofALSs(Ryabinkov,Kaminker&Varshalovich2001;hereafterPaperII)basingonthecatalogbyJunkkarinen,Hewitt&Burbidge(1991)withintheextendedrangez=0.0−3.7.Itwasshownthatthez-distributionofALSsdisplaysapatternofalternatingmaxima(peaks)andminima(dips)whicharestatisticallysignificantagainstasmoothdependence(trend).Itisessentialthatthepositionsofthepeaksanddipsturnedouttobeindependent(withinsta-tisticaluncertainties)ofobservationdirections.Thissuggestedthatthederiveddistributionofabsorptionmatterisnotonlyspatialbutalsotemporalinnature.Wepresenttheresultsofanextendedstatisticalanalysisperformedbydifferentmethodsonthebaseofourcatalogofabsorptionsystems(Ryabinkovetal.2003).Fig.1demonstratestwoz-distributionsNAS(z)ofALSscontainingabsorptionlinesofheavyelementswithintheredshiftintervalz=0.0–3.7.Oneofthemisobtainedusing847systemsfromthecatalogTheredshiftdistribution3byJunkkarinenetal.(1991)andthesecondoneisbasedon2003systemsregisteredinthespectraof661QSOs(emissionredshiftswithinze=0.29–4.9)fromthecatalogbyRyabinkovetal.(2003).AllALSsunderconsiderationcompriselinesofheavyelementsandmayincludeupto20–30absorptionlinesdetectedindifferentregionsofQSOspectra(predominantlywithintheinterval3000–8000˚A).WeexcludeALSsconsistingonlyofneutralhydrogenlinesaswellasdampedLyαabsorptionsystems(DLA).AllredshiftszjregisteredinspectraofeachQSOandfallenintothevelocityintervalδv=500kms−1aretreatedasasingleabsorptionsystemwithanaveragedredshiftza=(Pnaj=1zj)/na,wherenaisanumberofredshiftswithintheinterval.BothdistributionsinFig.1areobtainedusingso-calledsliding-averageapproachwhichrepresentsasetofconsecutivedisplacementsoftheaveragingbinΔz=0.071alongz-axiswithastepδz=0.01.Acomparisonofthetwoz-distributions(Fig.1)revealssimilarpatternsofthepeaksanddipsrelativelysmoothcurves.Thepositionsofmajorityofthepeaksanddipsremainthesameaftertheextensionofstatisticsandsomeofthembecomemoresignificant.Thereareonlyafewexceptionsconcernedwithsplittingofsomeinitiallysinglepeaksintodoubleonesandanappearanceofnewpeaks(seeTable1).InPapersIandIIthestatisticalanalysisofALSswasperformedusingtheaveragingbinΔz=0.071.Thisvaluewaschosenwithemployingtheχ2-criterionasameasureofthemostsignificantdeviationsofthez-distributionsobtainedfordifferentvaluesΔzfromthehypothesisoftheuniformdistribution(withuseofthetrendsubtraction).Onthiswaytheresultsofstatisticalconsiderationscouldbesensitivetoartificialnon-uniformitiesinducedbyaseparationofthewholesampleoftheredshiftsintobins.Toexcludes