Colour corrections for high redshift objects due to intergal(4)

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

4A.Meiksin

I

Table2.IntergalacticHλ( A)

z=1.5

transmissionasafunctionofobservedwavelength.

z=2.5

z=3.0

z=3.5

z=4.0

z=4.5

z=5.0

z=5.5

z=6.0

z=6.5

z=7.0

z=2.0

Note:Thefulltableispublishedintheelectronicversionofthepaper.Aportionisshownhereonlyforguidanceregardingitsformandcontent.

3

210

34567

redshift

3

210

2.5

33.544.55

redshift

Figure2.IntergalacticattenuationkIGM-correctionandcoloursfora600Myrstarburstwithcontinuousstarformation.(a)Fromlefttoright,kIGMforUn,G,R,Iandz′bands(solidlines).FortheUnandGbands,kIGMassumingtheabsenceofLymanLimitSystemsisshownbythedashedlines.TheabsenceofLymanLimitSystemsleavestheresultsfortheremainingbandsunal-tered.ThelightsolidlinescorrespondtothepredictionsforkIGMusingtheattenuationmodelofMadau(1995).(b)TheUn G(solid)andG R(longdashed)coloursofthestarburst.Thedot-tedshort-dashedlinesanddottedlong-dashedlineshowUn GandG R,respectively,assumingtheabsenceofLymanLimitSystems.ThelightlinescorrespondtothepredictionsbasedontheattenuationmodelofMadau(1995).

FunctionandweregeneratedbytheSTARBURST99modelofLeithereretal.(1999).TheTypeIQSOspectrumisthecompositespectrumconstructedfromover2200spectraho-mogeneouslyselectedfromtheSDSSQSOsurveycoveringtheredshiftinterval0.044<z<4.789andrestframewave-lengthrange800 A 8555 A(VandenBerketal.2001).TheTypeIIQSOspectrumisbasedonobservationsofCXO52(Sternetal.2002),asdescribedinMeiksin(2005).ThisTypeIIQSOwaschosenbecauseithashighequivalentwidthemissionlinesthatwilldominatethemagnitudeofthebandinwhichtheylie,andsorepresentsaclassofob-jectsthatwillhaveunusualbroadbandcoloursthatvarysubstantiallywithredshift.

Thee ectofintergalacticattenuationonbroadbandmagnitudesiscomputedforseveral ltersystemsrelevanttorecentandplannedmajorsurveys:theSloanu′g′r′i′z′system(assumingairmass1.3responseforapointsource);theUnGRsystemofSteidel’sgroup,supplementedbytheI-bandadoptingtheHarrisI lter;theHubbleSpaceTele-scope(HST)ACS/NICMOSB435(F435W),V606(F606W),i775(F775W),z850(F850LP),J110(F110W)andH160(F160W)bands(includinginstrumentalresponses);theUKIDSSZYJHK lters;andtheJWSTF070W(desig-natedm070andapproximatedasasquaretransmissionre-sponse)andF150W(designatedm150)bands.Allmagni-tudesarecomputedontheABsystem.

ThekIGM-correctionsandcoloursfortheUn,GandR ltersofSteidel&Hamilton(1992)aswellastheIandz′bands,areshowninFigure2forthe600Myroldstar-burst.Thee ectofinternalredenningisnotincluded.Thiswillnegligiblya ectkIGM,sothemagnitudecorrectionstothecoloursduetoredenningwillsimplybeadditive.AlsoshownaretheresultsassumingnoLymanLimitSystemsintercepttheline-of-sight.ThemeancontributionofLymanLimitSystemshasasubstantiale ectonUn,asmalle ectonG,andanegligiblee ectonthelongerwavelengthbandsforkIGM<3.AcomparisonwiththeattenuationmodelofMadau(1995)showsareductioninkIGMofabout0.5magni-tude,althoughthee ectonthecoloursapproachashiftofafullmagnitude.Intermsofphotometricredshifts,thedi er-enceinattenuationmodelsproducesashiftof z=0.1 0.2forUn GandG R.ThekIGM-correctionsandvariouscolourcombinationsforallthesourcesconsideredareshowninFigures3and4.ThekIGM-correctionsarenearlyindepen-dentofthesourcespectrum,exceptfortheTypeIIQSOforwhichthemagnitudesmaybedominatedbyemissionlines(Meiksin2005).ThecoloursalsoaresimilarexceptfortheTypeIIQSO,althoughcertaincolours,suchasUKIDSSJ KandH K,areparticularlye ectiveatseparatingtheothersources.

4SUMMARY

Theamountoftheattenuationoflightfromhighredshiftob-jectsonpassingthroughtheIGMhasbeencomputedbasedonrecentmeasurementsofthemeantransmittedLyα uxthroughtheIGMandrecentassessmentsofthenumbersofLymanLimitSystems.ThepropertiesoftheIGMrequiredtocomputetheattenuationduetoresonantLymanphotonscatteringwerebasedonnumericalsimulationsmatchingthemeasuredpropertiesoftheIGM.Di erencesfromthepre-dictionsofthemodelofMadau(1995)arefoundforkIGM

c2005RAS,MNRAS000,000–000