Colour corrections for high redshift objects due to intergal

Corrections to the magnitudes of high redshift objects due to intergalactic attenuation are computed using current estimates of the properties of the intergalactic medium. The results of numerical simulations are used to estimate the contributions to reson

Preprint-00

Colourcorrectionsforhighredshiftobjectsduetointergalacticattenuation

AveryMeiksin

5February2008

SUPA ,InstituteforAstronomy,UniversityofEdinburgh,BlackfordHill,EdinburghEH93HJ,UK

arXiv:astro-ph/0512435v1 16 Dec 2005

ABSTRACT

Correctionstothemagnitudesofhighredshiftobjectsduetointergalacticattenuationarecomputedusingcurrentestimatesofthepropertiesoftheintergalacticmedium.TheresultsofnumericalsimulationsareusedtoestimatethecontributionstoresonantscatteringfromthehigherorderLymantransitions.Di erencesof0.5 1magnitudefromthepreviousestimateofMadau(1995)arefound.IntergalactickIGM-correctionsandcoloursareprovidedforhighredshiftstarburstgalaxiesandTypeIandTypeIIQSOsforseveral ltersystemsusedincurrentandplanneddeepopticalandinfra-redsurveys.

Keywords:galaxies:highredshift-galaxies:photometry-intergalacticmedium-quasars:absorptionlines-quasars:general-surveys

1INTRODUCTION

Overthepastdecade,deepopticalandinfra-redsurveyshaveenabledgiantstridestobetakeninelucidatingthena-tureandpropertiesofobjectsthatpopulatethehighredshiftuniverse.Theband-dropoutmethodhasunveiledapopu-lationofLymanbreakgalaxiesatz≈3(Guhathakurtaetal.1990;Bithell1991;Steidel&Hamilton1992,1993;Steidel,Pettini&Hamilton1995;Steideletal.2003)andhigher(Sawicki&Thompson2005).TheselectionmethodwassuccessfullyappliedtotheHubbleDeepField(HDF)(Giavalisco,Steidel&Macchetto1996;Steideletal.1996),broadeningtheredshiftrangeandvolumecoverageoverpre-vioussurveys.MostrecentlytheUltraDeepField(UDF)

>

wasexploitedtodiscoverobjectsasdistantasz～6(Stan-way,Bunker&McMahon2003;Bouwensetal.2004;Yan&Windhorst2004;Giavaliscoetal.2004).

Analternativeselectionmethodforidentifyinghighredshiftobjectsreliesoncombinationsofbroadbandcolourstoestimatephotometricredshifts,forwhichthemostlikelyredshiftisassignedbasedonpredictedspectralenergydis-tributions(Sawicki,Lin&Yee1997;Csabaietal.2000).

Themodellingofthehighredshiftobjectsthroughpopulationsynthesis,appliedtoacombinationofspectro-scopicdataandbroad-bandcolours,suggeststhatmostofthehighredshiftobjectsarestar-forminggalaxies(Madauetal.1996;Metcalfeetal.2001;Papovich,Dickinson&Fer-guson2001;Pettinietal.2001;Shapleyetal.2003).AfewoftheLymanbreakgalaxiescontainActiveGalacticNuclei

(Steideletal.2002),usedtodeterminethefaintendoftheQSOluminosityfunctionatz≈3(Huntetal.2004).

ParalleltothesesurveyshavebeenseveralsearchesforhighredshiftQuasi-StellarObjects(QSOs).Thediscoveryofafewdozenz>3.6QSOsbytheSloanDigitalSkySurvey(SDSS)hasmadepossibleanewevaluationofthebrightendoftheQSOluminosityfunctionanditsevolutionatthesehighredshifts(Fanetal.2001).Theresultsarecurrentlybeingrevised(Richardsetal.2005)basedonthemuchlargernumbersnowdetected,includingover500atz>4(Schneideretal.2005).

Similarsurveysareexpectedtocontinuewellintothefuture,includingsomenowinprogress,suchastheCanada-France-HawaiiTelescopeLegacySurvey(CFHTLS )andtheUKIRTInfraredDeepSkySurvey(UKIDSS ;Hewettetal.,inpreparation),orplannedfortelescopescurrentlyunderdevelopment,suchastheVisible&InfraredSurveyTelescopeforAstronomy(VISTA§)andtheJamesWebbSpaceTelescope(JWST¶).

Crucialtoalltheseanalysesisanaccurateestimateoftheamountofintergalacticattenuationduetointerveningabsorptionsystems.MosthavereliedonthestandardworkofMadau(1995),whoseassessmentwasbasedonthethenmostcurrentunderstandingofthepropertiesanddistribu-tionsofinterveningsystems.Madau(1995)estimatedthe

ScottishUniversitiesPhysicsAlliancec2005RAS

§¶

www.cfht.hawaii.edu/Science/CFHLS/www.vista.ac.ukwww.ngst.nasa.gov