eso phase 3 data release description

ESO Phase 3 Data Release Description

Data Collection KiDSRelease Number 4Data Provider KonradKuijkenDate 19.02.2019

Abstract ThisdatareleaseconstitutesthefourthpublicreleasebytheKilo-DegreeSurvey(KiDS).KiDSisanESOpublicsurveycarriedoutwiththeVLTSurveyTelescopeandOmegaCAMcamera,thatwillimage1350squaredegreesinfourfilters(u,g,r,i),insingleepochsperfilter.KiDSwasde-signedasaweaklensingsheartomographysurvey,anditscoresciencedriversaremappingofthelarge-scalematterdistributionintheuniverseandconstrainingtheequation-of-stateofDarkEnergy.AdditionalsciencecasesaremanifoldandrangefromgalaxyevolutiontoMilkyWaystructure,andfromdetectionofwhitedwarfstohigh-redshiftquasars.Thisdatareleasemorethandoublestheskyareacoveredbythefirstthreereleasescombined,andforthefirsttimeincludesphotometryfromthepartnerVIKINGESOpublicimagingsurveyonVISTA.Foreachof1006square-degreesurveytilesthedatareleaseincludescalibratedstackedimagesinu,g,randifilters,theircorrespondingweightsandmasks,andsingle-bandsourcelistsextractedfromthestacks.Furthermore,amulti-bandugriZYJHKssourcecatalogueisprovidedthatencompassesthecombined1006squaredegreeareaofthisdatarelease,withPSF-homogenisedandaperture-matchedphotometryandphotometricredshiftestimates.TheVSTdataincludedinKiDS-ESO-DR4weretakenunderESOprogrammeIDs:177.A-3016(A),177.A-3016(B),177.A-3016(C),177.A-3016(D),177.A-3016(E),177.A-3016(F),177.A-3016(G),177.A-3016(H),177.A-3016(I),177.A-3016(J),177.A-3016(K),177.A-3016(L),177.A-3016(M),177.A-3016(N),177.A-3016(O),177.A-3016(P),177.A-3016(Q),177.A-3016(S),177.A-3017(A),177.A-3018(A),60.A-9038(A),and094.B-0512(A).TheVISTAdatainthisdatareleasearetakenfromVIKINGDR3(q.v.),releasedSept.1,2017.

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Figure1:locationofthe1006KiDS-ESO-DR4tiles.TheareacoveredinDR1/2/3isshowninblue,whilethegreentilesarenewadditions.Thetarget1350sq.deg.KiDSsurveyarea(top:KiDS-North;bottom:KiDS-South)isoutlinedingrey.

Overview of Observations Thisdatarelease(KiDS-ESO-DR4)consistsofthecoaddedimages,weightmaps,masksandsourcelistsof1006squaredegreesurveytilesobservedwithOmegaCAMontheVSTinu,g,randibandsbeforeJanuary24,2018.Itsupercedesthe440tilesreleasedinDR1/2/3(deJongetal.2015,A&A582,A62;deJongetal.2017,A&A604,A134).Figure1showstheDR4footprint.Un-liketheprevious,incrementalreleases,forDR4alldatawerereprocessedwithimprovedastro-metricandphotometriccalibrationalgorithms.Theu,g,randiimageswerereducedwiththeAs-tro-WISEsystem(McFarlandetal.2013,Exp.Astron.,35,45).

Inadditiontothesesingle-banddataproducts,KiDS-ESO-DR4includesa9-bandugriZYJHKssourcecataloguethatspansallsurveytilesinthedatarelease.Itcontainslist-driven,aperture-andPSF-matchedGAaPphotometryfromthestackedVSTimages,aswellasfromtheVISTApointingstakenforthenear-IRVIKINGsurvey(Edgeetal.2013,TheMessenger154,32).Theincludedsourcesaredetectedonaseparatereductionofther-bandstackswiththeTHELIpipe-line(Erbenetal.2013,MNRAS433,2545),optimisedfortheweaklensinganalysis.Theser-banddetectionimagesarealsoincludedinthedatarelease.

Fromthebeginning,KiDSandVIKINGwereconceivedtogetherasacombinedsurvey,coveringthesamepartsofthesky.TheVIKINGsurveystartedbeforeKiDS,andwasterminatedin2015beforecompletingtheoriginallyplanned1500squaredegreefootprint.ItwasthereforedecidedthatKiDSobservationswouldprioritisethe1350squaredegreesforwhichVIKINGdataexist.AtthetimeofwritingitseemslikelythatKiDSwillalsoconcludeobservationsoncethe1350squaredegreeVIKINGfootprinthasbeencovered.ThefootprintareashowningreyinFigure1isthisreducedarea.

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Release Content

Imaging products and single-band source lists Thelistof1006tilesforwhichimagingdataproductsandsingle-bandsourcelistsareincludedinKiDS-ESO-DR4isprovidedonlineathttp://kids.strw.leidenuniv.nl/DR4/data_table.php.

Eachtilewasobservedinu,g,r,andiband.Thefinalfootprintofeachtileisslightlylargerthan1squaredegreeduetotheditheringscheme:61.9x65.4arcminutesinu;62.3x66.8arcminutesing,randi.Takingthisintoaccount,thetotalskycoverageisapproximately993squaredegrees(1022iftheedgesofthefootprint,wheretherearefewerditherexposures,areincluded).Com-paredtopreviousDRtheskycoverageofthereleaseddataissignificantlymorecontiguous,asillustratedinFigure1.Thesingle-bandsourcelistswereextractedfromthecalibrated,stackedimagesforeachtileandfilterseparately,usingtheAstro-WISEprocessingsystem.Inaddition,asecond,weaklensing-optimisedreductionofther-bandsurveytilesusingtheTHELIdatareductionpipelinewasper-formed,resultinginaseparater-bandsourcelistthatisusedforthe9-bandphotometryand(future)weaklensinganalysis(thesecataloguesaredescribedinthenextsection).

SincetheOmegaCAMCCDmosaicconsistsof32individualCCDs,theskycoveredbyasingleex-posurehasgaps.Inordertofillinthesegaps,KiDStilesarebuiltupfrom5ditheredobservationsing,randiand4inu.Thedithersformastaircasepatternwithditherstepsof25′′inX(RA)and85′′inY(DEC),bridgingtheinter-CCDgaps(deJongetal.,2015,A&A,582,A62).ThetilecentresarebasedonatilingstrategythattilesthefullskyefficientlyforVST/OmegaCAM.NeighbouringditheredstackshaveanoverlapinRAof5%andinDECof10%.

InFigure2theobtainedseeing(FWHM),PSFellipticity,andlimitingmagnitude(5σABin2''ap-erture)distributionsperfilterareshown,toillustratetheobtaineddataquality.Incaseofthefiltersobservedindarktime(u,g,r)theFWHMdistributionsreflectthedifferentobservingcon-straints,withr-bandtakingthebestconditions.Sincei-bandistheonlyfilterobservedinbrighttime,itisobservedunderalargerangeofseeingconditions.AveragePSFellipticitiesarealwayssmall:<0.1(theaverageisovertheabsoluteamountofellipticity,regardlessofthedirectionofellipticity).Thewiderangeoflimitingmagnitudesini-bandiscausedbythelargerrangeinsee-ingandinmoonphaseandthusskybrightness.

ArepeatpassofthefullKiDSareainibandisunderway,andwillbeincludedinafuturerelease.ThesenewdatadonotsufferfromthepoorbafflingoftheVSTintheperioduptoMay2015thatparticularlyaffectedtheibandskybackground.

Forafulloverviewofthedataqualityparametersforeachobservationwerefertothefollowingonlinetable:http://kids.strw.leidenuniv.nl/DR4/data_table.php.

Thesingle-bandtilesinthisdatareleaseconsistsof19.114filesandatotaldatasizeof179Gbofcataloguedataand17Tbofpixeldata(image,weightandmask).

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Figure2:Tile-by-tilerawdataqualityparametersforKiDS-ESO-DR4.Left:averagePSFsize(FWHM)distributions;centre:averageellipticitydistributions(definedas1-B/A,whereAandBarethemajorandminoraxisRMSlengthofthePSF);right:limitingmagnitudedistributions(5σABin2''aperture).Thedistributionsareperfilter:fromtoptobottomu,g,r,andi,respectively.

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9-band source catalogue TheKiDS-ESO-DR49-bandsourcecatalogueisbasedontheimagingdataproductsdescribedabove,aswellasnewZYJHKsnear-IRphotometrymeasuredontheimagesfromtheoverlappingVIKINGsurveyonVIRCAM@VISTA.Hereweprovideageneraldescriptionofthecataloguedata,whileanoverviewofalltileswithcoordinates,PSFsize,limitingmagnitude,etc.isprovidedonline:http://kids.strw.leidenuniv.nl/DR4/data_table.php.

Thecatalogueisbasedonthecombined1006surveytiles,providingatotalareacoverageofap-proximately1022squaredegrees.Thedetectioncataloguewasgeneratedfromther-bandimag-esreducedwiththeTHELIpipeline.Thoseimagesformthebasisfortheweaklensingshapemeasurements,andthischoiceensuresthatthedefinitionofthesourcesinthephotometriccata-logueisconsistentwiththeupcominglensingcatalogue(therewasnosuchmatchbetweentheDR3photometriccatalogueandtheDR3.1lensingcatalogue,eventhoughtheyweregeneratedfromthesamerawdata).Thesourcecoordinatesandsizeswerethenusedforforced(list-driven)'GaussianApertureandPSF(GAaP)'photometry(Kuijkenetal.2015,MNRAS454,3500)ontheAstro-WISEugriVSTimages,andtheZYJHKsVISTAimagesreducedattheCambridgeAs-tronomicalSurveyUnit(CASU).TheGAaPphotometryforasourceiseffectivelytheintegratedsurfacebrightnessoveranellipticalGaussianaperturefunction,definedontheintrinsic,seeing-deconvolvedsky.Itweightseachpartofthesourceconsistentlyineachphotometricband.Exceptforunresolvedsources,itdoesnotmeasurethetotalflux;insteadtheGAaPaperturesize,shapeandorientationitisoptimisedtoreturnahighSNRfluxforuseincolourmeasurements.ErrorestimatesontheGAaPfluxesareobtainedbypropagatingthermspixelnoisethroughthemeas-urementprocess.

TheGAaPfluxesfortheVSTdataweremeasuredfromthestackedu,g,randiimages.FortheVISTAdata,wherethegapsbetweendetectorsarelargerandPSFvariationsacrossthefieldandfromsubexposuretosubexposuregreater,photometrywasmeasuredfromindividualsummedjittered'paw-print'images(seeVIKINGDR3releasedescription).Eachsourcewastypicallyde-tected2-6timespernear-IRfilter,andthe9-bandcataloguereportstheoptimally-weightedav-eragefluxoverallavailablesubexposurescontainingthatsource.

TheinitialphotometriccalibrationoftheVSTimagesisbasedonnightlyzeropointsfromphoto-metricstandardstarfieldsobservations.Thesearesubsequentlyrefinedatcataloguelevelwithstellar-locusregressionandanchoringtotheGaiaGbandphotometry(Brownetal.2018,A&A616,A1).Thefluxscalesintheimagescorrespondtothenightlyzeropoints,withthecatalogue-levelcorrectionsreportedintheimageheader.

VIKINGimagingiscalibratedto2MASSphotometry(Skrutskieatal.2006,AJ,131,1163)withinCASU.Thiscalibrationisverifiedafterphotometryismeasuredbycomparingindividualstellarfluxestimatesperpaw-printtoSDSSz-banddata(Alametal.2015,ApJS219,12)fortheZ-band,colourconvertedSDSSzand2MASSJdatafortheY-band,and2MASSJHKdatafortheJHKsbandsrespectively.Medianoffsetsbetween2MASSandVIKINGphotometryperobservationarealsocalculated,toflagpoorlycalibratedobservations.

Foranygivensource,GAaPphotometryrequiresthesameaperturetobespecifiedacrossallbands,andthisaperturemustnotbesmallerthantheseeing.TheGAaPapertureradiiaresettothermsradiimeasuredonther-banddetectionimage(SExtractorparametersA_WORLDandB_WORLD),quadraticallyaddedtoaminimumradiuschosentooptimizetheSNR.Toaccommo-dateoccasionalpoorseeinginoneofthe9bands,GAaPphotometrywasrunwithtwochoicesofaminimumGaussianaperturermsradius:0.7”and1.0”.Whentheseeingisgoodinallbandsthesmallersettingwillyieldthemostaccuratemeasurements,andthisphotometryisused.Butforabandwheretheseeingispoor,thelargeraperturemayyieldamoreaccurateflux,orthesmaller

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aperturemaynotyieldafluxmeasurementatall.Thechoiceofapertureradiusismadesourcebysource.

AdetaileddescriptionoftheVIKINGGAaPphotometryisprovidedinWrightetal.(ref).

The9-bandcataloguecontainsatotalof100.350.873sources,ismadeupof1007files(1006da-tafilesand1metadatafile),andhasatotaldatavolumeof28.5GB.

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Release Notes

Data Reduction and Calibration TheKiDS-ESO-DR4pipelineisanevolutionoftheKiDS-ESO-DR3pipeline(deJongetal,2017,A&A604,A134)(DJ17)andbasedontheAstro-WISEopticalpipelinedescribedinMcFarlandetal.(2013,ExA35,45)(MF13).BelowwesummarizetheprocessingstepsandlistKiDS-specificinformation(i.e.,KiDSprocessconfigurationanddeparturesfromAstro-WISEopticalpipeline).Themaindifferenceswiththepreviousreleaseareanimprovedastrometriccalibrationproce-dure,improvedmanualmaskingofsatellitetracks,theseparater-banddetectionimagespro-ducedwithTHELIthatformthebasisofthe9-bandphotometrycatalogue,andthephotometriccalibrationtotheall-skyGaiaDR2Gbandcatalogue.

Image de-trending De-trendingoftherawdataconsistsofthefollowingsteps.

• Cross-talkcorrection.Electroniccross-talkoccursbetweenCCDs#93,#94,#95and#96,resultinginfaintimprintsofbrightsourcesonneighbouringCCDs.Acorrectionwasmadeforcross-talkbetweenCCDs#95and#96,whereitisstrongest(upto0.7%).

• De-biasingandoverscancorrection.First,foreachscienceandcalibrationexposuretheoverscanissubtractedperrow(usingmethod6,seeMF13).Second,adailyover-scan-subtractedbiasissubtracted.Thisisadailyaverageof10biaseswith3σ-rejection.

• Flat-fielding.Whereasinthetwopreviousdatareleasesasinglemasterflat(perCCDandfilter)wasusedforalldata,changestothetelescopebafflesinthreestepsduring2014/2015necessitatedthecreationofnewsetsofmasterflats.Table1liststhefourdif-ferentbaffleconfigurationsandtheperiodsduringwhichtheywereonthetelescope.

Config. Description Startdate Enddate

1 Originalset-up May2011 7Jan2014

2 Baffleextensions1(M2,chimney) 8Jan2014 6Apr2014

3 Baffleextensions2(M2,chimney,M1plug)

7Apr2014 29Apr2015

4 Baffleextensions3(chimneyridges,plug) 30Apr2015 presentTable1:VSTbaffleconfigurationsForeachbafflingconfigurationasinglemasterflat(perCCDandfilter)wasused,byvir-tueofthestabilityoftheintrinsicpixelsensitivities,thatcanbeconsideredconstantto~0.2%orbetterforg,randi(DJ15,VerdoesKleijnetal.,2013,ExA,35,103).Forg,randithismasterflatisacombinationofamasterdome(forhighspatialfrequencies)andmastertwilight(=sky)flat-field(forlowspatialfrequencies).Bothcontributingflatsareanaverageof5rawflat-fieldexposureswith3σ-rejection.Inubandonlythetwilightflatsareused.

• Illuminationcorrection.Illuminationcorrection(a.k.a.“photometricsuperflat”)isap-pliedinpixelspace,andonlyonthesourcefluxes(i.e.,afterbackgroundsubtraction).Asingleilluminationcorrectionimageisusedtocorrecteachmasterflat(seealsoDJ15andVerdoesKleijnetal.,2013,ExA35,103).Forbafflingconfiguration2,3and4illumina-tioncorrectionframeswerederivedfromthoseforconfiguration1,basedonthediffer-encebetweenflatfieldsobservedwitheachbafflingconfigurationandwiththeoriginalset-up.

• De-fringing.De-fringingisonlyneededforKiDSi-band.Analysisofnightlyfringeframesshowedthatthepatternisconstantintime.Therefore,asinglefringeimagewasusedforallKiDS-ESO-DR4imagesobservedafter2012-01-11.Foreachscienceexposurethis

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fringeimageisscaled(afterbackgroundsubtractionofthescienceexposureandfringeframe)andthensubtractedtominimizeresidualfringes.

• Pixelmasking.Cosmic-rays,hotandcoldpixels,saturatedpixelsareautomaticallymaskedasdescribedinMF13duringde-trending.Theseareincludedintheweightim-age.Additionalautomaticandmanualmaskingisappliedonthecoadds(seebelow).

• Satellitetrackremoval.SatellitetracksaredetectedautomaticallybyapplyingtheHoughtransform(Hough,1962)toadifferenceimageofmaximallyoverlappingexpo-sureswithinadithersequenceaftermaskingbrightstarsandbrightghosts.Thepixelsaffectedbysatellitetracksaremaskedandincludedintheweightimage.Note:satellitetracksorpartsthereofremainingafterthisautomatedsteparemaskedduringthecoad-ditionstage,seebelow.

• Backgroundsubtraction.Toremovevignettingbybondwirebaffling(Iwertetal.2006,Proc.SPIE6276,62760A)inthefocalplane,arow-by-rowbackgroundsubtractionmethodisused,beforethebackgroundsubtractiondonebySWARP(seebelow).Note:strongvignettingisnotfullyremovedwiththismethodandismaskedduringthecoaddi-tionstage,seebelow.

TheTHELIreductionsofther-bandimagesaregroupedintwo-week‘runs’andnewcalibrationframesarederivedforeachrun.Thisincludesilluminationcorrections,masterflats,andbiases.AmoredetaileddescriptionoftheTHELIprocessingwillbegiveninErbenetal.(inpreparation)'.

Photometric calibration Thestepstakentocalibratethephotometryareasfollows.

• KiDS-ESO-DR4photometriccalibrationstartswithindividualzero-pointsperCCDbasedonsecondarystandardfieldobservations.Thecalibrationdeploysafixedaperture(6.3arcsecdiameter)notcorrectedforfluxlosses,andusesSDSSDR8PSFmagnitudesofstarsintheSAfieldsasreference.MagnitudesareexpressedinABintheinstrumentalphotometricsystem(i.e.,nocolourcorrectionsbetweentheOmegaCAMandSDSSpho-tometricsystemapplied).

• Next,thephotometryintheg,r,andifiltersishomogenizedacrossCCDsanddithersforeachfilterineachtileindependently.Foru-bandthishomogenizationisnotappliedbe-causetherelativelysmallsourcedensityoftenprovidesinsufficientinformationtotieadjacentCCDstogether.Thisglobalphotometricsolutionisderivedandappliedinthreesteps:

1. Fromtheoverlappingsourcesacrossditheredexposures,zero-pointdifferencesbetweenthedithers(e.g.duetovaryingatmosphericextinction)arederived.

2. Zero-pointdifferencesbetweenCCDsarecalculatedusingallCCDoverlapsbe-tweentheditheredexposures.Steps1and2bothapplyaminimizationalgo-rithm(seeMaddoxetal.1990,MNRAS,246,433).

3. Thezero-pointoffsetsareappliedtoallCCDsw.r.t.anaveragezero-pointvalidforthenight,derivedfromthenightlySAfieldobservations.IfnoSAfieldobser-vationsareavailableforthenight,defaultvaluesareusedinstead.

Theabovestepscompletethephotometriccalibrationoftheimagedataandsingle-bandsourcelists.Afurtherhomogenizationofthephotometryoverthewholesurveyareaiscalculatedusing,andappliedto,themulti-bandsourcecatalog,andisdescribedbelow.

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Astrometry, regridding and coadding Aglobal(multi-CCDandmulti-dither)astrometriccalibrationiscalculatedperfilterpertile.SCAMP(Bertin2006,ASPConf.Series351,112)isusedforthispurpose,withapolynomialde-greeof3overthewholemosaic,whileaninitialmodelissuppliedtoconstrainthefocalplanegeometry.The(unfiltered)2MASS-PSC(Skrutskieetal.2006,AJ,131,1163)isusedasastromet-ricreferencecatalogue.

SWARPisusedtoresampleallexposuresinatiletothesamepixelgrid,withapixelsizeof0.2arcseconds.Afterbackgroundsubtractiontheexposuresarecoaddedusingaweightedmeanstackingprocedure.

Masking residual satellite tracks and bond wire baffling features Spuriousfeaturesremaininginthecoaddedimagesareidentifiedbyvisualinspectionof1500x1500pixel'thumbnails',attwolevelsofcontrast,byateamofKiDSmembers.Missedorincompletelymaskedtracksthatarecaughtatthisstagearemarkedmanuallyonthumbnailim-ages,afterwhichanautomaticprocedureidentifiesandmasksthetracksinthecorrectsubexpo-sure(s).Residualbackgroundfeaturesduetothebondwirebafflesareflaggedmanually,triggeringthecreationofmasksbasedonstandardregionfiles.IndividualCCDsshowingelectronicinstabilityarealsomanuallyflaggedandremovedfromthelistofframestobeco-added.Finally,usingtheupdatedmasks,newstacksandcorrespondingweightimagesareproduced.

Masking of bright stars Astand-aloneprogramdubbedPulecenellav1.0(DJ15)wasdevelopedtocreatemasksforKiDScoadds,andisnowembeddedinthepipeline.Itisanautomatizedprocedureformaskcreationcompletelyindependentfromexternalstarcatalogues.AnexampleofadetailofamaskisshowninFigure3.Pulecenelladetectsthefollowingtypesofcriticalareas,allrelatedtobrightstars:

• saturatedpixels,• spikescausedbydiffractionbythemirrorsupports,• readoutspikes,• reflectionhalosproducedbytheopticscomponents(acentralcorehalo,anduptothree

widerreflectionhaloswithspatiallydependentoffsets,dependingonthebrightnessofthestar.

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Figure3:DetailofaPulecenellav1.0mask.Left:detailofaKiDSstackedimagewithbrightstars;criticalareasdetectedbyPulecenellaareover-plottedwithgreenoutlines.Right:FLAGimagecor-respondingtotheimageshownontheleft,withdifferentcoloursindicatingthepixelvaluesresult-ingfromthecombinationofdifferentflagvalues.ThemasksareprovidedasFITSFLAGimages,whereeachtypeofcriticalregionisidentifiedbyadifferentflagvalue,aslistedinTable2.Duringsourceextractionforthesingle-bandsourcelist(seebelow)theFLAGimageisusedtoflagsourceswhoseisophotesoverlapwiththecriticalare-as.Theresultingflagsarestoredinthefollowingtwosourceparameters:

• IMAFLAGS_ISO:FLAGimageflagsOR'dovertheisophoteprofile• NIMAFLAG_ISO:numberofflaggedpixelsenteringIMAFLAGS_ISO

Typeofarea Flagvalue Typeofarea Flagvalue

Readoutspike 1 Secondaryhalo 16

Saturationcore 2 Tertiaryhalo 32

Diffractionspike 4 Badpixel 64

Primaryhalo 8 Table2:Criticalareasinthesingle-bandimagemasksandtheirflagvalues.

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Parameter Value Description

DETECT_THRESH 1.5 <sigmas>or<threshold>,<ZP>inmag.arcsec-2

DETECT_MINAREA 3 minimumnumberofpixelsabovethreshold

ANALYSIS_THRESH 1.5 <sigmas>or<threshold>,<ZP>inmag.arcsec-2

DEBLEND_NTHRESH 32 Numberofde-blendingsub-thresholds

DEBLEND_MINCONT 0.002 Minimumcontrastparameterforde-blending

FILTER Y Applyfilterfordetection(YorN)

FILTER_NAME default.conv Nameofthefilecontainingthefilter

CLEAN Y Cleanspuriousdetections?(YorN)?

CLEAN_PARAM 1.0 Cleaningefficiency

BACK_SIZE 256 Backgroundmesh:<size>or<width>,<height>

BACK_FILTERSIZE 3 Backgroundfilter:<size>or<width>,<height>

BACKPHOTO_TYPE LOCAL canbe“GLOBAL”or“LOCAL”

BACKPHOTO_THICK 24 thicknessofthebackgroundLOCALannulusTable3:detectionset-upforKiDS-ESO-DR4single-bandsourcelists

Single-band source list extraction and star/galaxy separation Thesingle-bandsourcelistsdeliveredinthisdatareleaseareintendedas“generalpurpose”sourcelists.Sourcelistextractionandstar/galaxy(hereafterS/G)separationisdonewithanau-tomatedprocedureoptimizedforKiDSdata:KiDS-CAT.Thisprocedure,thebackboneofwhichisformedbyS-Extractor(Bertin&Arnouts,1996,A&AS,317,393)performsthefollowingsteps.

1. S-ExtractorisrunonthestackedimagetomeasuretheFWHMofallsources.High-confidencestarcandidatesarethenidentified(fordetailsseeLaBarberaetal.2008,PASP,120,L681).

2. TheaveragePSFFWHMiscalculatedbyapplyingthebi-weightlocationestimatortotheFWHMdistributionofthehigh-confidencestarcandidates.

3. AsecondpassofS-ExtractorisrunwithSEEING_FWHMsettothederivedaveragePSFFHWM.Duringthissecondpasstheimageisbackground-subtracted,filteredandthresholded“on-thefly”.Detectedsourcesarethende-blended,cleaned,photometered,andclassified.AnumberofS-Extractorinputparametersaresetindividuallyforeachimage(e.g.,SEEING_FWHMandGAIN),whileothershavebeenoptimizedtoprovidethebestcompromisebetweencompletenessandspuriousdetections(seetheDataQualitysectionbelow).Thedetectionset-upusedissummarizedinTable3;afullSExtractorconfigfileisavailableatthisURL:http://kids.strw.leidenuniv.nl/DR4/example_config.sexApartfromisophotalmagnitudesandKron-likeellipticalaperturemagnitudes,alargenumberofaperturefluxesareincludedinthesourcelists.Thisallowsuserstoestimateaperturecorrectionsandtotalsourcemagnitudes.AllparametersprovidedinthesourcelistsarelistedintheDataFormatsectionbelow.

4. S/GseparationisperformedbasedtheCLASS_STAR(starclassification)andSNR(signal-to-noiseratio)parametersprovidedbyS-Extractorandconsistsofthefollowingsteps:

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• IntheSNRrangewherethehigh-confidencestarcandidatesarelocated(thereddotsinFigure4)thebi-weightestimatorisusedtodefinetheirCLASS_STARlo-cation,θ,anditswidth,σ;alowerenvelopeofθ−4σisdefined.

• AtSNRbelowthatofthehigh-confidencestarcandidates,arunningmedianCLASS_STARvalueiscomputedfromsourceswithCLASS_STAR>0.8,whichisshiftedtomatchtheθ−4σlocus.Theresultingcurve(bluecurveinFigure4)definestheseparationofstarsandgalaxies.

Figure4:High-confidencestarcandidatesandstar/galaxyseparation.Left:thehigh-confidencestarcandidates(reddots)areusedtolocatethestellarlocusandcalculatetheaverageFWHMoftheimage.Right:exampleofstar/galaxyseparation;atSNR>50,thehigh-confidencestarcandi-dates(reddots)areusedtodefinetheblueline;atlowerSNR,allsourceswithCLASS_STAR>0.8areused;sourcesabovethebluelineareclassifiedasstars.

Thesourcemagnitudesandfluxesinthefinalsingle-bandsourcelistsarenotcorrectedforGalac-ticforegroundorintergalacticextinction.TheresultoftheS/Gclassificationisavailableinthesourcelistsviathe2DPHOTflag(SG2DPHOTinthemulti-bandcatalog).Flagvaluesare:1(high-confidencestarcandidates),2(objectswithFWHMsmallerthanstarsinthestellarlocus,e.g.,somecosmic-raysand/orotherunreliablesources),4(starsaccordingtoS/Gseparation),and0otherwise(galaxies);flagvaluesaresummed,so2DPHOT=5signifiesahigh-confidencestarcandidatethatisalsoabovetheS/Gseparationline.

9-band source catalogue Apartfromthesingle-bandVSTdataproducts,ESO-KiDS-DR4alsoincludesamatched-aperturephotometrycatalogue,containing9optical+near-infraredbandsfromacombinedanalysisofKiDSandVIKING.Thiscatalogueisoptimisedforweakgravitationallensingscience,andforthispurposeanindependent,high-accuracyastrometricanalysisofther-bandimageswasperformedusingtheTHELIpipeline.Sourcesforthe9-bandcataloguearedetectedonthese'detectionim-ages',andtheirpositionsusedforlist-drivenphotometryontheugriKiDSandZYJHKsVIKING'science'images.TheTHELI-reducedr-banddetectionimages,aswellastheirassociatedweightandmaskimages,arepartofDR4.Accurategalaxyshapemeasurementsforthegalaxieswillbeprovidedasaseparatedataproductinafurtherrelease.

SourcesaredetectedontheTHELIr-banddetectionimagesusingSExtractor,andsourceaper-turepositionsandsizesarethenusedtoperformGAaPphotometryontheKiDS(Astro-WISE)andVIKING(CASU)images.Thedetectionsetupisslightlydifferenttothesingle-bandAstro-

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WISEsetupinTable3:theTHELIsetupusesDETECT_MINAREA=1,BACK_TYPE=MANUAL,BACK_VALUE=0.0,0.0andDEBLEND_MINCONT=0.001.Notethatthesourcesinthiscataloguearenotnecessarilythesameasthoseinthesingle-bandr-bandsourcelistsdescribedabove.AnumberofmorphologicalparametersarebasedonthisSExtractorrun,aswellasGAaPfluxes,fluxerrors,andmaskflagsforeachofthe9bands.Foreachsourcetheextinctioninallninefiltersisprovid-ed,interpolatedfromtheextinctionmapsbySchlegeletal.(1998,ApJ,500,525),withupdatedextinctioncoefficientsfromSchlafly&Finkbeiner(2011,ApJ,737,103).

Topreventsourcesintileoverlapsfromappearingmultipletimesinthecatalogue,thesurveytileshavebeencroppedtoseamlesslyconnecttoeachother.Alongtheedgesofsurveytilesthedataarelessdeep,butnoworsethanintheareaslocatedinthegapsbetweentherowsofCCDsinthefocalplane,exceptalongtheouteredgesofthecontiguousareas.9-bandfluxesarereport-edforallr-banddetections.

Seeingdifferencesandaperture-matching

ThecatalogueincludesmagnitudesfromthePSFhomogenizationandmatched-aperturepho-tometry“GAaP”pipeline.ThisnoveltechniqueisdesignedtoaccountforPSFdifferencesbetweendifferentfilters,whileoptimizingsignal-to-noise.Inshort,thePSFwithineachcoaddedimageishomogenizedtoaGaussianshapewithoutsignificantlydegradingtheseeing.Aperturephotome-tryisthenperformedusingellipticalGaussianapertureweightfunctions,whichareanalyticallycorrectedforseeingdifferences.AdetaileddescriptionofthepipelinecanbefoundinKuijkenetal.(2015,MNRAS,454,3500)(K15).Itisimportanttonotethatthesemagnitudesaredesignedforderivingaccuratecoloursofgalaxies,notfortotalmagnitudesofgalaxies.Forpointsources(stars),GAaPmagnitudesapproachPSF-fittingphotometry.TheGaussianapertureshape(Agap-er,Bgaper)andorientationissetfromtheSextractorA,BandPAmeasurementsonther-banddetectionimage:Agaper=sqrt(MINAPER**2+(A_WORLD*3600)**2),dittoB;valuesaremaxim-isedatMAXAPER=2”.PhotometryfortwoGAaPruns,withMINAPER=0.7”and1.0”,isreportedinthecatalogue(columnsFLUX_GAAP_0p7_xandFLUX_GAAP_1p0_x,etc).ThelargerMINAPERval-ueensuresvalidmeasurementsforthosepartsofthesurveywheretheseeinginoneofthebandswasparticularlypoor.

Surveyphotometrichomogenization

Zero-pointcorrectionshavebeencalculatedforallugriKiDSsurveytilesincludedinthemulti-bandcataloguetoimprovethehomogeneityofthephotometry.Thesecorrectionsarebasedonstellarlocusregression(SLR).TheSLRisusedtocalibratetheu,gandifilterstother-band,andthelatteristiedtoGaiaDR2usingtransformationsderivedfromtheoverlapareabetweenKiDSandSDSS.

Themajorityofstarsdisplayawell-definedphotometricstellarlocus:atightrelationincolour-colourspacewithalocationthatvarieslittleacrosstheskyoutsidetheGalacticplane.SLRisthemethodwheretheobservedstellarlocusismatchedtothefiducialintrinsiclocus,andoffersthepossibilitytoachievecolourhomogeneity.SLRwasappliedtotheGAaPphotometryofunmaskedandnotflagged,highS/N(magr,GAaP<19)pointsources(0.4''<FWHMr<0.8'').PersourcetheGAaPmagnitudesarecorrectedforGalacticextinctionusingtheE(B-V)colourexcessfromSchle-geletal.(1998)andextinctioncoefficientsfromSchafly&Finkbeiner(2011).Thestellarlocusisparametrizedusingthe“principalcolours”s,xandwasdefinedbyIvezicetal.(2004,AN,325,583).Foreachofthesecolours(projectionsthatarelinearcombinationsoftheugrifilters),a

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straightsectionofthestellarlocusliesparalleltooneaxis(P1)andiscentredat0ontheotheraxis(P2),seeFig.5.Weaddafourth,redundantcolourkasadditionalguardforfittingrobust-ness.PersourcetheP1andP2arecalculatedineachcolourandsourcesonthestraightpartofthestellarlocusareselectedusingfixedlimitsinP1.ThemedianP2valuesineachtilearecon-vertedtozero-pointoffsetswithrespecttor(d(u-r),d(g-r),d(i-r)).Fig.5showsanexampleofatypicalfit.

Figure5:principalcolourss,w,xandkfortileKiDS_129.0_0.5.Thesamestars(yellow)areplottedineachpanel,withthestarsusedtolocatethestraightsectionsofthelocusshowninblack.Thein-ferredmedianP2offsets’formalerrorsandstandarddeviationsareshownaboveeachpanel.

AlreadyinDR3weconcludedthatubandcalibrationwiththeSLRtechniquesdescribedaboveresultedinlargeerrors,andthealternativeapproachofoverlapphotometrywasused.ForDR4adifferentapproachwasusedfortheuband,acombinationofSLRwithalatitude-dependentcor-rectionterm,obtainedbyfittingtheextinction-correctedubandasafunctionofdereddened(g-r)colourandgalacticlatitudeovertheSDSSregionthatoverlapswithKiDS-N:

u=g+2.0(g-r)0+0.456+max(0,0.66-2(g-r)0)-0.25|sin(b)|(0.15<(g-r)0<0.8)

Theu-bandzeropointofeachKiDStileisthenadjusteduntilthemedianresidualfromthisrela-tioniszero.

TheSLRyieldsazero-pointoffset/correctionpersurveytileforeachfilter.Theoffsetsasde-rivedforbandxarelistedinthecatalogueheadersasDx_SLRandDx_SLR_1fortheMINA-PER=0.7and1.0GAaPruns.Theoffsetsarealsolistedonlineinthecataloguetable.Bydefinition,ther-bandSLRoffsetiszero.

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Figure6.IllustrationofthecalibrationoftherbandphotometryfortileKiDS_131.0_0.5totheGaiaGband,usingthedereddenedKiDS(g-i)coloursofstarswith16.5<G<19.25.Thestarsplottedinblueareusedtodeterminetheverticallocationoftheredbox,whichiscenteredontherelationde-rivedfromtheSDSS-Gaia-KiDSoverlap.

CalibrationtoGaia-DR2Gband

WiththeadventofGaia,ahigh-density,accuratephotometriccataloguecoveringthewholeskyhasbecomeavailable.Pertiletypically500-1000Gaiastarswereusedtotiether-bandphoto-metriczeropointtotheGaia-DR2Gbandcalibration,usingafiducialdereddened(r-G)vs(g-i)colour-colourrelationderivedfromtheoverlapofKiDS-NorthwiththeSDSSDR7catalogue.Thesameoffsetisappliedtou,gandimagnitudesaswell,topreservetheSLRcalibration.AnexampleofthiscalibrationisshowninFigure6.ThesezeropointsarereportedinthecatalogueheadersasDMAG_xandDMAG_x_1,fortheMINAPER=0.7and1.0GAaPruns,andareappliedtotheMAG_GAAP_0p7_xandMAG_GAAP_1p0_xmagnitudesgiveninthecatalogues.Foreachugriim-agethezeropointthatisderivedusingthelargestnumberofstarsisrecordedintheimagehead-er;thekeywordCALMINAPrecordsthecorrespondingvalueofMINAPER.

Near-infraredphotometryfromVIKINGtiedto2MASS

VIKINGphotometryiscalibratedto2MASSduringitsprocessing.TheGAaPfluxesinthe9-bandcatalogueusethiscalibrationwithoutchange.AllVIKINGfluxeshavemagnitudezeropoint30.MoredetailsareprovidedinWrightetal(2018).

ChoiceofGAaPapertureandextinctioncorrectedmagnitudes

BecausethefootprintsoftheVISTAandVSTobservationsdiffer,theband-by-bandseeingofthesourcesvariesonscalessmallerthanaKiDStile.Thecataloguethereforeprovidesasource-by-sourcechoicebetweentheMINAPER=0.7andMINAPER=1.0columns.Thedecisionisbasedonthefluxerrorsonthemeasurementsofthatsourceinallbands:

1. DefineERROR_RATIO_x=FLUXERR_GAAP_x_1p0/FLUXERR_GAAP_0p7_xforeachbandx.

2. IfMAX(ERROR_RATIO_x)*MIN(ERROR_RATIO_x)<1,usethelarger(1p0)aperture.

Thischoiceensuresthatthelargerapertureisonlyusedif,foratleastoneband,ityieldsafrac-tionalimprovementinfluxerrorthatisgreaterthanthefractionalpenaltyinanyotherband.

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ThefluxesthatcorrespondtothisbestaperturechoicearerecordedinthecataloguesasFLUX_GAAP_x,MAG_GAAP_x,etc.Themagnitudesarecorrectedforthephotometriczero-pointandgalacticextinction:

MAG_GAAP_x=DMAG_x–2.5log10(FLUX_GAAP_0p7_x)–EXTINCTION_x

or

MAG_GAAP_x=DMAG_x_1–2.5log10(FLUX_GAAP_1p0_x)–EXTINCTION_x

wheretheDMAG_xandDMAG_x_1valuesarethosereportedintheheaderforx=u,g,r,i,andequalto30fortheVISTAZ,Y,J,H,Ksbands.

(NotethatthemagnitudesMAG_GAAP_0p7_xandMAG_GAAP_1p0_xareNOTcorrectedforex-tinction)

Extinction-correctedcolours

Inordertofacilitatefastercataloguesearches,thecatalogueincludescolumnswithsourcecol-oursbetweenadjacentbands(u-g,g-r,…,J-H,H-Ks).ThesecoloursarebasedontheGAaPmagni-tudes,whichprovidethemostaccuratecoloursbothforgalaxiesandpointsources.Inthesecol-umnsthezero-pointcorrectionsdescribedabove,aswellastheper-sourceGalacticextinctioncorrections,arealreadyapplied.

Photometricredshifts

BasedonthehomogenizedGAaPphotometry,photometricredshiftshavebeencalculatedfollow-ingthemethodsdevelopedforCFHTLenSanddescribedinK15.ThismakesuseoftheBayesianphotometricredshiftcodeBPZ(Benítez,2000,ApJ,536,571)incombinationwiththere-calibratedtemplatesfromCapak(2004,PhD.thesis,Univ.Hawai'i).Anewpriordistribution(RaichoorA.,etal.,2014,ApJ,797,102)hasbeenusedforDR4,whichismoreeffectiveatfaintermagnitudesthanthepriorusedforDR3,butisbiasedbyca.+0.06atbrightmagnitudes.Wealsoswitchedto68%confidenceintervalsforthephoto-zposterior(previousreleasesreported95%).Wecautionallusersthatforaccuratework,thephotometricredshiftsshouldbeusedinconjunctionwithexternalcalibrationdatainordertoquantifytheirerrordistri-bution(see,e.g.Hildebrandtetal.2017,465,1454).ThecataloguealsoincludestheODDSpa-rameter,ameasureoftheuni-modalityoftheredshiftPDF,andthebest-fittemplateforeachsource(parameterT_B).Thevaluescorrespondtothefollowingtypes,wherefractionaltypescanoccurbecausethetemplatesareinterpolated:1=CWW-Ell,2=CWW-Sbc,3=CWW-Scd,4=CWW-Im,5=KIN-SB3,6=KIN-SB2.

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Data Quality AnoverviewoftheintrinsicdataqualityofKiDS-ESO-DR4,intermsofseeing,PSFellipticity,andlimitingmagnitudesdistributionsispresentedinFig.2.Inthefollowingwefocusonthequalityofthereduceddataproducts.

Photometric quality Thematterofphotometricqualitycanbesplitupintwo:

1. theuniformityofthephotometrywithineachtile2. thequalityoftheabsolutephotometriccalibrationpertile/filter

Boththeinternalphotometrichomogeneitywithinacoaddandthequalityoftheabsolutepho-tometricscalecanbeassessedbycomparingtheKiDS-ESO-DR4photometrytoSDSSDR8(Aiharaetal.,2011,ApJS,193,29).Forthis,PSFmagnitudeswereextractedfromSDSSDR8andcom-paredtoboththeaperture-correctedandGAaPmagnitudesintheKiDS-ESO-DR4multi-bandcat-alogue.OnlystarswithphotometricerrorsbothinKiDSandinSDSSsmallerthan0.02maging,r,andior0.03inuwereused.ThiscomparisoncanbemadeonlyforalltilesintheKiDS-Northfield,butsinceKiDS-SouthwascalibratedinthesamewayasKiDS-North,weexpecttheconclu-sionstoholdforalldata.

Figure7showstheoffsetsbetweenKiDSaperture-correctedandSDSSDR8magnitudesfor1tile(KIDS_182.0_-0.5),whichisarepresentativeexample.Generally,thephotometryinafilterisuni-formwithinonetiletowithinafewpercent.Inu-bandthephotometrymaybelessstableinsomecasesduetothelackofphotometrichomogenizationwithinatile.

Figure7:KiDS−SDSSmagnitudeoffsetsfor(unmasked)starsintileKiDS182.0_-0.5vsRA(toppan-el)andDEC(bottompanel),basedonaperture-correctedfluxes.Fromtoptobottomthesub-panelscorrespondtou,g,r,andi,respectively.Eachdotcorrespondstoastar,andthereddashedlinesindicate+0.05and−0.05magnitudes.

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Fig.8:PhotometriccalibrationandPSFsizesinKiDS-North.AveragemagnitudeoffsetsforKiDS-ESO-DR3tilesbetweenKiDSGAaPmagnitudesandSDSSDR8PSFmagnitudesofstarsareindicatedbythecolourcoding,whilethesymbolsizecorrespondstotheaveragePSFsize.

ThequalityoftheabsolutephotometricscaleisillustratedinFigure8andsummarizedinTable4.Smallsystematicoffsetsof2to3%arepresentinallfilters.Thiscouldbeduetothefactthatnightlyzero-pointsaredeterminedusingafixedapertureonstarsintheSAfieldwithoutaper-turecorrection.Thescatterandoccasionaloutliersinthestandardcalibrationareduetonon-photometricconditions(duringeitherKiDSorSAfieldobservations)and,particularlyincaseoftheu-band,useofdefaultzero-pointsfornightswithoutgoodSAfieldobservations.PhotometricinhomogeneitiesinSDSS,whichisreliableto1%ingriand2%inu(Padmanabhanetal.2008,ApJ,674,2)alsocontributetothemeasuredscatter.

Filter Meanoffset(mag) Standarddeviation(mag)

u 0.008 0.035

g 0.001 0.014

r -0.013 0.005

i -0.003 0.009Table4:AveragemagnitudeoffsetsandtheirstandarddeviationwithrespecttoSDSSDR8(foru,g,r,i)andexpectedstellarlocuslocations(inprincipalcolourss,w,x)forGAaPandaperture-corrected(10'')magnitudes,bothbeforeandafterphotometrichomogenization.

Thephotometrichomogenizationschemesignificantlyimprovesthestabilityofthecalibrationandannihilatestheoutlierscompletely,withthepossibleexceptionsofisolatedtilesorverysmallcontiguousgroupswithoutphotometricanchors.DerivedusingGAaPmagnitudes,theho-mogenizationclearlyworksbestwhenappliedtotheGAaPmagnitudes.GiventhephotometricstabilityofSDSSquotedbyPadmanabhanetal.(2008,ApJ,674,2),thestandarddeviationsoftheoffsetstoSDSS(secondtolastcolumninTable4)implythatthestabilityofthecalibrationintheu-,g-r-andi-bandsisapproximately2%,2%,1%and1%,respectively.Alsowhenappliedtotheaperture-correctedmagnitudesthestabilityofthecalibrationissignificantlyimprovedandoutli-ersremoved.TheSLRstepinthephotometrichomogenizationprocedureensuresthatthestellarlocus“principalcolours”(bottomthreerowsinTable4)areclosetozero.Overall,thecombina-tionofGAaPmagnitudes,extinctioncorrectionsandphotometrichomogenizationproducesthemostaccuratecolours,bothforstarsandgalaxies.Notethatthecolourcolumnsinthemulti-bandcataloguealreadycontainallthesecorrections,whiletheindividualmagnitudecolumnsarenotcorrectedforextinctionandcalibrationvariations!

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Colour terms ThephotometriccalibrationprovidedinKiDS-ESO-DR4isinABmagnitudesintheinstrumentalsystem.Wereportherethecolour-termscalculatedwithrespecttotheSDSSphotometricsystemforDR3.

Aperture-correctedmagnitudestakenfromthemulti-bandcatalogue,werematchedtoSDSS(DR8)PSFmagnitudesofpoint-likesources.Foreachfilter,themedianoffsettoSDSSisfirstsub-tracted,rejectingtileswherethisoffsetexceeds0.1maginanyoftheg,randibands.Thefitismadeusingallpointsfromtheremainingtiles.Theresultingcolourterms:

uKiDS−uSDSS=(−0.050±0.002)(uSDSS−gSDSS), gKiDS−gSDSS=(−0.052±0.002)(gSDSS−rSDSS), rKiDS−rSDSS=(−0.033±0.002)(gSDSS−rSDSS), iKiDS−iSDSS=(+0.012±0.002)(rSDSS−iSDSS).

Known issues

Image defects ScatteredlightandreflectionsSomeofthemainissuesintheDR1/2/3VST/OmegaCAMdata(beforethebafflingimprovementsdescribedaboveweremade)arerelatedtoscatteredlightandreflections.Duetotheopenstruc-tureofthetelescope,lightfromsourcesoutsidethefield-of-viewcanaffecttheobservations.Thisexpressesitselfinanumberofways:

• Reflections:insomecasesstrongreflectedlightpatternsareseeninthefocalplane;thesearecausedbylightfrombrightpointsourcesoutsidethefield-of-viewandcanoc-curinallfilters.

• VignettingbyCCDmasks:vignettingandscatteringbythemaskspresentatthecornersofthefocalplanearray,andatthegapsbetweentherowsofCCDs;thiseffectisparticu-larlystrongini-bandduetothebrightconditions.TheeffectneartheCCDgapsislargelycorrectedfor,butinmanycasestheareasinthecornersoftheCCDarrayisstronglyaf-fected.

• Extendedbackgroundartefacts:relatedtothereflectionsmentionedbefore,thisismost-lyseenini-bandandprobablycausedbymoonlight.

Improvementstothetelescopebafflesthatwereinstalledin2014and2015significantlyim-provedscatteredlightsuppression.Thei-bandobservations,manyofwhichweretakenwiththemoonabovethehorizon,wereparticularlyaffectedbyscatteredlight;asecondi-bandpassisunderwayandthesenewdata(whichwillformpartofDR5)shouldhavesignificantlylowerandsmootherbackgrounds.

MoredetailedillustrationsofsomeofthescatteredlighteffectsareprovidedintheReleaseNotesaccompanyingKiDS-ESO-DR3.

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Previous Releases Thecurrentrelease,KiDSpublicdatareleasenumber4orKiDS-ESO-DR4,wasprecededbydatareleasenumbers1-3(KiDS-ESO-DR1/2/3).Itsupersedestheseearlierreleases,representingacompletere-reductionofallKiDStilescompletedbeforeJanuary24th,2018.Forasmallnumberoftilestheautomaticreductionfailedinawaythatcouldnoteasilybefixed,andinordernottodelayDR4thesehavebeenexcludedfromthedelivery.TheywillbeincludedinDR5.Thesemiss-ingtilesincludefivetiles(KIDS_39.6_-34.1,KIDS_338.8_-32.1,KIDS_340.0_-32.1,KIDS_340.2_-31.2,KIDS_343.5_-32.1)whichprocessedwithouterrorinDR1+2+3,butwhichfailedtoyieldaconsistentastrometricsolutionintheDR4pipeline(conversely,amuchlargernumberoftilesthatgaveproblemsintheearlierprocessingpassedthroughtheDR4reductionwithoutprob-lem).

Apartfromthelargeincreaseinarea,from440to1006square-degreetiles,themainenhance-mentofDR4overthepreviousreleaseistheinclusionoftheVIKINGphotometryinthemulti-bandcatalogue,andthehomogeneouscalibrationoftheKiDSdatatoGaiathroughstellarlocusregression.

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Data Format

Files Types Table5liststhetypesofdataproductsprovidedinthisrelease,togetherwithdescriptionsofthefiletypesandnamingconventionsused.

Thenamingconventionusedforalldataproductsisthefollowing:

KiDS_DR4.0_R.R_D.D_F_TTT.fits,

whereR.RandD.DaretheRAandDECofthetilecentreindegrees(J2000.0)with1decimalplace,Fisthefilter(u,g,r,oriforsingle-banddatafiles,“ugriZYJHKs”formulti-bandcataloguefiles),andTTTisthedataproducttype(seecolumn4ofTable5).

Forexample:ther-bandstackedimageofthetile“KIDS_131.0_-0.5”iscalledKiDS_DR4.0_131.0_-0.5_r_sci.fits.

Table5:dataproductsandfiletypes

Format of coadded images Thefinalcalibrated,coaddedimagesfromtheAstro-WISEpipelinehaveauniformpixelscaleof0.2arcsec.Thepixelunitsarefluxesrelativetothefluxcorrespondingtomagnitude=0,asbasedonnightlyphotometriccalibrations.Thismeansthattheeffectivezero-pointisequalto0andthemagnitudemcorrespondingtoapixelvaluefis:

m=−2.5log10f.

SubsequentphotometriczeropointcorrectionswerederivedfromthecataloguesandrecordedintheimageheadersusingtheDMAGkeyword.ThekeywordsCALSTARSandCALMINAPgivethenumberofGaiastarsthatwereusedinthecalibration,andCALMINAPisthevalueoftheGAaPMINAPERparameter(0.7or1.0)thatwasusedforthephotometrythatresultedinthiszero-point.

Ther-banddetectionimages,whichresultfromareductionusingTHELI,specificallydesignedforoptimalimageshapemeasurementandsmallastrometricreductions,arethebasisofthemulti-bandcatalogue.TheyhaveapixelscalethatisclosertothenativeOmegaCAMpixelsizeof0.213”.

Dataproduct ESOproductcategoryname

Filetype TTT F

Calibrated,stackedimages SCIENCE.IMAGE FITSimage sci u,g,r,i

Weightframes ANCILLARY.WEIGHTMAP FITSimage wei u,g,r,i

Masks ANCILLARY.MASK FITSimage msk u,g,r,i

Single-bandsourcelists SCIENCE.SRCTBL BinaryFITStable src u,g,r,i

Multi-bandcataloguedatafile SCIENCE.MCATALOG BinaryFITStable cat ugriZYJHKs

THELIdetectionimage ANCILLARY.IMAGE FITSimage det_sci r

THELIweightimage ANCILLARY.IMAGE FITSimage det_wei r

Multi-bandmaskimage ANCILLARY.MASK FITSimage msk ugriZYJHKs

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Catalogue Columns Table6liststhecolumnsthatarepresentinthesingle-bandsourcelistsprovidedinKiDS-ESO-DR4.Alargenumber(27)ofaperturefluxesareprovidedtosuittheneedsofdifferentusersandallowinterpolationtoestimatee.g.aperturecorrections.Onlythecolumnsforthesmallestaper-ture(2pixels,or0.4arcsecdiameter)andthelargestaperture(200pixels,or40arcsecdiame-ter)arelistedinTable6.Note:thelabelfortheapertureof28.5pixelsisFLUX_APER_28p5.

Table7liststhecolumnsthatarepresentinthemulti-bandsourcecatalogueprovidedinKiDS-ESO-DR4.ThemeaningofthebitsofthecorrespondingMASKvaluesisexplainedinTable8.

Table6:columnsprovidedintheKiDS-ESO-DR4single-bandsourcelistsLabel Format Unit Description

2DPHOT J Source classification

X_IMAGE E pixel Object position along x

Y_IMAGE E pixel Object position along y

NUMBER J Running object number

CLASS_STAR E S-Extractor S/G classifier

FLAGS J Extraction flags

IMAFLAGS_ISO J FLAG-image flags OR'ed over the iso. profile

NIMAFLAG_ISO J Number of flagged pixels entering IMAFLAGS_ISO

FLUX_RADIUS E pixel Fraction-of-light radii

KRON_RADIUS E pixel Kron apertures in units of A or B

FWHM_IMAGE E pixel FWHM assuming a gaussian core

ISOAREA_IMAGE J pixel**2 Isophotal area above Analysis threshold

ELLIPTICITY E 1 - B_IMAGE/A_IMAGE

THETA_IMAGE E deg Position angle (CCW/x)

MAG_AUTO E mag Kron-like elliptical aperture magnitude

MAGERR_AUTO E mag RMS error for AUTO magnitude

ALPHA_J2000 D deg Right ascension of barycentre (J2000)

DELTA_J2000 D deg Declination of barycentre (J2000)

FLUX_APER_2 E count Flux vector within circular aperture of 2 pixels

... ... ... ...

FLUX_APER_200 E count Flux vector within circular aperture of 200 pixels

FLUXERR_APER_2 E count RMS error vector for flux within aperture of 2 pixels

... ... ... ...

FLUXERR_APER_200 E count RMS error vector for flux within aperture of 2 pixels

MAG_ISO E mag Isophotal magnitude

MAGERR_ISO E mag RMS error for isophotal magnitude

MAG_ISOCOR E mag Corrected isophotal magnitude

MAGERR_ISOCOR E mag RMS error for corrected isophotal magnitude

MAG_BEST E mag Best of MAG_AUTO and MAG_ISOCOR

MAGERR_BEST E mag RMS error for MAG_BEST

BACKGROUND E count Background at centroid position

THRESHOLD E count Detection threshold above background

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Label Format Unit DescriptionMU_THRESHOLD E arcsec**(-2) Detection threshold above background

FLUX_MAX E count Peak flux above background

MU_MAX E arcsec**(-2) Peak surface brightness above background

ISOAREA_WORLD E deg**2 Isophotal area above Analysis threshold

XMIN_IMAGE J pixel Minimum x-coordinate among detected pixels

YMIN_IMAGE J pixel Minimum y-coordinate among detected pixels

XMAX_IMAGE J pixel Maximum x-coordinate among detected pixels

YMAX_IMAGE J pixel Maximum y-coordinate among detected pixels

X_WORLD D deg Barycentre position along world x axis

Y_WORLD D deg Barycentre position along world y axis

XWIN_IMAGE E pixel Windowed position estimate along x

YWIN_IMAGE E pixel Windowed position estimate along y

X2_IMAGE D pixel**2 Variance along x

Y2_IMAGE D pixel**2 Variance along y

XY_IMAGE D pixel**2 Covariance between x and y

X2_WORLD E deg**2 Variance along X-WORLD (alpha)

Y2_WORLD E deg**2 Variance along Y-WORLD (delta)

XY_WORLD E deg**2 Covariance between X-WORLD and Y-WORLD

CXX_IMAGE E pixel**(-2) Cxx object ellipse parameter

CYY_IMAGE E pixel**(-2) Cyy object ellipse parameter

CXY_IMAGE E pixel**(-2) Cxy object ellipse parameter

CXX_WORLD E deg**(-2) Cxx object ellipse parameter (WORLD units)

CYY_WORLD E deg**(-2) Cyy object ellipse parameter (WORLD units)

CXY_WORLD E deg**(-2) Cxy object ellipse parameter (WORLD units)

A_IMAGE D pixel Profile RMS along major axis

B_IMAGE D pixel Profile RMS along minor axis

A_WORLD E deg Profile RMS along major axis (WORLD units)

B_WORLD E deg Profile RMS along minor axis (WORLD units)

THETA_WORLD E deg Position angle (CCW/world-x)

THETA_J2000 E deg Position angle (east of north) (J2000)

ELONGATION E deg A_IMAGE/B_IMAGE

ERRX2_IMAGE E pixel**2 Variance of position along x

ERRY2_IMAGE E pixel**2 Variance of position along y

ERRXY_IMAGE E pixel**2 Covariance of position between x and y

ERRX2_WORLD E deg**2 Variance of position along X-WORLD (alpha)

ERRY2_WORLD E deg**2 Variance of position along Y-WORLD (delta)

ERRXY_WORLD E deg**2 Covariance of position X-WORLD/Y-WORLD

ERRCXX_IMAGE E pixel**(-2) Cxx error ellipse parameter

ERRCYY_IMAGE E pixel**(-2) Cyy error ellipse parameter

ERRCXY_IMAGE E pixel**(-2) Cxy error ellipse parameter

ERRCXX_WORLD E deg**(-2) Cxx error ellipse parameter (WORLD units)

ERRCYY_WORLD E deg**(-2) Cyy error ellipse parameter (WORLD units)

ERRCXY_WORLD E deg**(-2) Cxy error ellipse parameter (WORLD units)

ERRA_IMAGE E pixel RMS position error along major axis

ERRB_IMAGE E pixel RMS position error along minor axis

ERRA_WORLD E deg World RMS position error along major axis

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Label Format Unit DescriptionERRB_WORLD E deg World RMS position error along minor axis

ERRTHETA_IMAGE E deg Error ellipse pos. angle (CCW/x)

ERRTHETA_WORLD E deg Error ellipse pos. angle (CCW/world-x)

ERRTHETA_J2000 E deg J2000 error ellipse pos. angle (east of north)

FWHM_WORLD E deg FWHM assuming a gaussian core

ISO0 J pixel**2 Isophotal area at level 0

ISO1 J pixel**2 Isophotal area at level 1

ISO2 J pixel**2 Isophotal area at level 2

ISO3 J pixel**2 Isophotal area at level 3

ISO4 J pixel**2 Isophotal area at level 4

ISO5 J pixel**2 Isophotal area at level 5

ISO6 J pixel**2 Isophotal area at level 6

ISO7 J pixel**2 Isophotal area at level 7

SLID K Source list ID

SID K Source ID within the source list

HTM K Hierarchical Triangular Mesh (level 25)

FLAG K Not used

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Table7:ColumnsprovidedintheKiDS-ESO-DR49-bandphotometrycatalogueLabel Format Unit Description

GeneralSourceParametersDerivedfromr-bandTHELIDetectionImage

ID 30A ESOID

SeqNr 1J Runningobjectnumberwithinthecatalogue

SLID 1J AstroWiseSourcelistID

SID 1J AstroWiseSourceIDwithinthesourcelist

FLUX_AUTO 1E count r-bandflux(counts)

FLUXERR_AUTO 1E count ErroronFLUX_AUTO(counts)

MAG_AUTO 1E mag r-bandmagnitude(mag)

MAGERR_AUTO 1E mag ErroronMAG_AUTO(mag)

KRON_RADIUS 1E pixel Scalingradiusoftheellipseformagnitudemeasurements

BackGr 1E count Backgroundcountsatcentroidposition(counts)

Level 1E count Detectionthresholdabovebackground(counts)

MU_THRESHOLD 1E mag*arcsec**(-2) Detectionthresholdabovebackground(magarcsec^-2)

MaxVal 1E count Peakfluxabovebackground(counts)

MU_MAX 1E mag*arcsec**(-2) Peaksurfacebrightnessabovebackground(magarcsec^-2)

ISOAREA_WORLD 1E deg**2 Isophotalareaaboveanalysisthreshold(deg^2)

Xpos 1E pixel CentroidxpositionintheTHELIimage(pix)

Ypos 1E pixel CentroidypositionintheTHELIimage(pix)

RAJ2000 1D deg Centroidskypositionrightascension(J2000)(deg)

DECJ2000 1D deg Centroidskypositiondeclination(J2000)(deg)

A_WORLD 1E deg ProfileRMSalongmajoraxis(deg)

B_WORLD 1E deg ProfileRMSalongminoraxis(deg)

THETA_J2000 1E deg Positionangle(WestofNorth)(deg)

THETA_WORLD 1E deg Positionangle(Counterclockwisefromworldx-axis(deg)

ERRA_WORLD 1E deg WorldRMSpositionerroralongmajoraxis(deg)

ERRB_WORLD 1E deg WorldRMSpositionerroralongminoraxis(deg)

ERRTHETA_J2000 1E deg ErroronTHETA_J2000(deg)

ERRTHETA_WORLD 1E deg ErroronTHETA_WORLD(deg)

FWHM_IMAGE 1E pixel FWHMassumingagaussianobjectprofile(pix)

FWHM_WORLD 1E deg FWHMassumingagaussianobjectprofile(deg)

Flag 1I SExtractorextractionflags

FLUX_RADIUS 1E pixel Half-lightradius(pix)

CLASS_STAR 1E Star-galaxyclassifier

GAaPphotometryparametersfromAstro-WISEco-addedu,g,r,iimages

EXTINCTION_u 1E mag Galacticextinctionintheuband(mag)

EXTINCTION_g 1E mag Galacticextinctioninthegband(mag)

EXTINCTION_r 1E mag Galacticextinctiointherband(mag)

EXTINCTION_i 1E mag Galacticextincionintheiband(mag)

Agaper_0p7 1E arcsec MajoraxisofGAaPapertureminaper0.7arcs(arcsec)

Bgaper_0p7 1E arcsec MinoraxisofGAaPapertureminaper0.7arcs(arcsec)

Agaper_1p0 1E arcsec MajoraxisofGAaPapertureminaper1.0arcs(arcsec)

Bgaper_1p0 1E arcsec MinoraxisofGAaPapertureminaper1.0arcs(arcsec)

PAgaap 1E deg PositionangleofmajoraxisofGAaPaperture(NorthofWest)(deg)

FLAG_GAAP_0p7_u 1J GAaPFlagforMAG_GAAP_uminaper0.7arcs

FLAG_GAAP_0p7_g 1J GAaPFlagforMAG_GAAP_gminaper0.7arcs

26

FLAG_GAAP_0p7_r 1J GAaPFlagforMAG_GAAP_rminaper0.7arcs

FLAG_GAAP_0p7_i 1J GAaPFlagforMAG_GAAP_iminaper0.7arcs

FLUX_GAAP_0p7_u 1E count GAAPu-bandfluxminaper0.7arcs(counts)

FLUX_GAAP_0p7_g 1E count GAAPg-bandfluxminaper0.7arcs(counts)

FLUX_GAAP_0p7_r 1E count GAAPr-bandfluxminaper0.7arcs(counts)

FLUX_GAAP_0p7_i 1E count GAAPi-bandfluxminaper0.7arcs(counts)

FLUXERR_GAAP_0p7_u 1E count ErroronFLUX_GAAP_uminaper0.7arcs(counts)

FLUXERR_GAAP_0p7_g 1E count ErroronFLUX_GAAP_gminaper0.7arcs(counts)

FLUXERR_GAAP_0p7_r 1E count ErroronFLUX_GAAP_rminaper0.7arcs(counts)

FLUXERR_GAAP_0p7_i 1E count ErroronFLUX_GAAP_iminaper0.7arcs(counts)

FLAG_GAAP_1p0_u 1J GAaPFlagforMAG_GAAP_uminaper1.0arcs

FLAG_GAAP_1p0_g 1J GAaPFlagforMAG_GAAP_gminaper1.0arcs

FLAG_GAAP_1p0_r 1J GAaPFlagforMAG_GAAP_rminaper1.0arcs

FLAG_GAAP_1p0_i 1J GAaPFlagforMAG_GAAP_iminaper1.0arcs

FLUX_GAAP_1p0_u 1E count GAAPu-bandfluxminaper1.0arcs(counts)

FLUX_GAAP_1p0_g 1E count GAAPg-bandfluxminaper1.0arcs(counts)

FLUX_GAAP_1p0_r 1E count GAAPr-bandfluxminaper1.0arcs(counts)

FLUX_GAAP_1p0_i 1E count GAAPi-bandfluxminaper1.0arcs(counts)

FLUXERR_GAAP_1p0_u 1E count ErroronFLUX_GAAP_uminaper1.0arcs(counts)

FLUXERR_GAAP_1p0_g 1E count ErroronFLUX_GAAP_gminaper1.0arcs(counts)

FLUXERR_GAAP_1p0_r 1E count ErroronFLUX_GAAP_rminaper1.0arcs(counts)

FLUXERR_GAAP_1p0_i 1E count ErroronFLUX_GAAP_iminaper1.0arcs(counts)

MAG_GAAP_0p7_u 1E mag u-bandGAaPmagnitudemin_aper=0.7arcsec

MAGERR_GAAP_0p7_u 1E mag u-bandGAaPmagnitudeerrormin_aper=0.7arcsec

MAG_GAAP_0p7_g 1E mag g-bandGAaPmagnitudemin_aper=0.7arcsec

MAGERR_GAAP_0p7_g 1E mag g-bandGAaPmagnitudeerrormin_aper=0.7arcsec

MAG_GAAP_0p7_r 1E mag r-bandGAaPmagnitudemin_aper=0.7arcsec

MAGERR_GAAP_0p7_r 1E mag r-bandGAaPmagnitudeerrormin_aper=0.7arcsec

MAG_GAAP_0p7_i 1E mag i-bandGAaPmagnitudemin_aper=0.7arcsec

MAGERR_GAAP_0p7_i 1E mag i-bandGAaPmagnitudeerrormin_aper=0.7arcsec

MAG_GAAP_1p0_u 1E mag u-bandGAaPmagnitudemin_aper=1.0arcsec

MAGERR_GAAP_1p0_u 1E mag u-bandGAaPmagnitudeerrormin_aper=1.0arcsec

MAG_GAAP_1p0_g 1E mag g-bandGAaPmagnitudemin_aper=1.0arcsec

MAGERR_GAAP_1p0_g 1E mag g-bandGAaPmagnitudeerrormin_aper=1.0arcsec

MAG_GAAP_1p0_r 1E mag r-bandGAaPmagnitudemin_aper=1.0arcsec

MAGERR_GAAP_1p0_r 1E mag r-bandGAaPmagnitudeerrormin_aper=1.0arcsec

MAG_GAAP_1p0_i 1E mag i-bandGAaPmagnitudemin_aper=1.0arcsec

MAGERR_GAAP_1p0_i 1E mag i-bandGAaPmagnitudeerrormin_aper=1.0arcsec

SuppementarySourceParametersfromTHELIr-bandDetectionImage

MAG_ISO 1E mag r-bandIsophotalMagnitude(mag)

MAGERR_ISO 1E mag ErroronMAG_ISO(mag)

FLUX_ISO 1E count r-bandIsophotalFlux(counts)

FLUXERR_ISO 1E count ErroronFLUX_ISO(counts)

MAG_ISOCOR 1E mag r-bandCorrectedIsophotalMagnitude(mag)

MAGERR_ISOCOR 1E mag ErroronMAG_ISOCOR(mag)

FLUX_ISOCOR 1E count r-bandCorrectedIsophotalFlux(counts)

FLUXERR_ISOCOR 1E count ErroronFLUX_ISOCOR(counts)

NIMAFLAGS_ISO 1I Numberofflaggedpixelsovertheisophotalprofile

27

IMAFLAGS_ISO 1I FLAG-imageflagsORedovertheisophotalprofile

XMIN_IMAGE 1I pixel Minimumx-coordinateamongdetectedpixels(pixel)

YMIN_IMAGE 1I pixel Minimumy-coordinateamongdetectedpixels(pixel)

XMAX_IMAGE 1I pixel Maximumx-coordinateamongdetectedpixels(pixel)

YMAX_IMAGE 1I pixel Maximumx-coordinateamongdetectedpixels(pixel)

X_WORLD 1D deg Barycentrepositionalongworldxaxis(deg)

Y_WORLD 1D deg Barycentrepositionalongworldyaxis(deg)

X2_WORLD 1E deg**2 VarianceofpositionalongX_WORLD(alpha)(deg^2)

Y2_WORLD 1E deg**2 VarianceofpositionalongX_WORLD(delta)(deg^2)

XY_WORLD 1E deg**2 CovarianceofpositionX_WORLDY_WORLD(deg^2)/

ERRX2_WORLD 1E deg**2 ErroronXY_WORLD(deg^2)

ERRY2_WORLD 1E deg**2 ErroronXY_WORLD(deg^2)

ERRXY_WORLD 1E deg**2 ErroronXY_WORLD(deg^2)

CXX_WORLD 1E deg**(-2) SExtractorCxxobjectellipseparameter(deg^-2)

CYY_WORLD 1E deg**(-2) SExtractorCyyobjectellipseparameter(deg^-2)

CXY_WORLD 1E deg**(-2) SExtractorCxyobjectellipseparameter(deg^-2)

ERRCXX_WORLD 1E deg**(-2) ErroronCXX_WORLD(deg^-2)

ERRCYY_WORLD 1E deg**(-2) ErroronCYY_WORLD(deg^-2)

ERRCXY_WORLD 1E deg**(-2) ErroronCXY_WORLD(deg^-2)

A_IMAGE 1D pixel ProfileRMSalongx-axis(pix)

B_IMAGE 1D pixel ProfileRMSalongy-axis(pix)

ERRA_IMAGE 1E pixel ErroronA_IMAGE

ERRB_IMAGE 1E pixel ErroronB_IMAGE

S_ELLIPTICITY 1E SExtractorEllipticity(1-B_IMAGEA_IMAGE)/

S_ELONGATION 1E SExtractorElongation(A_IMAGEB_IMAGE)/

MAG_APER_4 1E mag r-bandMagnitudewithinacircularapertureof4pixels(mag)

MAGERR_APER_4 1E mag ErroronMAG_APER_4(mag)

FLUX_APER_4 1E count r-bandFluxwithinacircularapertureof4pixels(counts)

FLUXERR_APER_4 1E count ErroronFLUX_APER_4(counts)

MAG_APER_6 1E mag r-bandMagnitudewithinacircularapertureof6pixels(mag)

MAGERR_APER_6 1E mag ErroronMAG_APER_6(mag)

FLUX_APER_6 1E count r-bandFluxwithinacircularapertureof6pixels(counts)

FLUXERR_APER_6 1E count ErroronFLUX_APER_6(counts)

MAG_APER_8 1E mag r-bandMagnitudewithinacircularapertureof8pixels(mag)

MAGERR_APER_8 1E mag ErroronMAG_APER_8(mag)

FLUX_APER_8 1E count r-bandFluxwithinacircularapertureof8pixels(counts)

FLUXERR_APER_8 1E count ErroronFLUX_APER_8(counts)

MAG_APER_10 1E mag r-bandMagnitudewithinacircularapertureof10pixels(mag)

MAGERR_APER_10 1E mag ErroronMAG_APER_10(mag)

FLUX_APER_10 1E count r-bandFluxwithinacircularapertureof10pixels(counts)

FLUXERR_APER_10 1E count ErroronFLUX_APER_10(counts)

MAG_APER_14 1E mag r-bandMagnitudewithinacircularapertureof14pixels(mag)

MAGERR_APER_14 1E mag ErroronMAG_APER_14(mag)

FLUX_APER_14 1E count r-bandFluxwithinacircularapertureof14pixels(counts)

FLUXERR_APER_14 1E count ErroronFLUX_APER_14(counts)

MAG_APER_20 1E mag r-bandMagnitudewithinacircularapertureof20pixels(mag)

MAGERR_APER_20 1E mag ErroronMAG_APER_20(mag)

FLUX_APER_20 1E count r-bandFluxwithinacircularapertureof20pixels(counts)

28

FLUXERR_APER_20 1E count ErroronFLUX_APER_20(counts)

MAG_APER_30 1E mag r-bandMagnitudewithinacircularapertureof30pixels(mag)

MAGGERR_APER_30 1E mag ErroronMAG_APER_30(mag)

FLUXERR_APER_30 1E count r-bandFluxwithinacircularapertureof30pixels(counts)

FLUX_APER_30 1E count ErroronFLUX_APER_30(counts)

MAG_APER_40 1E mag r-bandMagnitudewithinacircularapertureof40pixels(mag)

MAGERR_APER_40 1E mag ErroronMAG_APER_40(mag)

FLUX_APER_40 1E count r-bandFluxwithinacircularapertureof40pixels(counts)

FLUXERR_APER_40 1E count ErroronFLUX_APER_40(counts)

MAG_APER_60 1E mag r-bandMagnitudewithinacircularapertureof60pixels(mag)

MAGERR_APER_60 1E mag ErroronMAG_APER_60(mag)

FLUX_APER_60 1E count r-bandFluxwithinacircularapertureof60pixels(counts)

FLUXERR_APER_60 1E count ErroronFLUX_APER_60(counts)

MAG_APER_100 1E mag r-bandMagnitudewithinacircularapertureof100pixels(mag)

MAGERR_APER_100 1E mag ErroronMAG_APER_100(mag)

FLUX_APER_100 1E count r-bandFluxwithinacircularapertureof100pixels(counts)

FLUXERR_APER_100 1E count ErroronFLUX_APER_100(counts)

ISO0 1I pixel**2 Isophotalareaatlevel0(pixel^2)

ISO1 1I pixel**2 Isophotalareaatlevel1(pixel^2)

ISO2 1I pixel**2 Isophotalareaatlevel2(pixel^2)

ISO3 1I pixel**2 Isophotalareaatlevel3(pixel^2)

ISO4 1I pixel**2 Isophotalareaatlevel4(pixel^2)

ISO5 1I pixel**2 Isophotalareaatlevel5(pixel^2)

ISO6 1I pixel**2 Isophotalareaatlevel6(pixel^2)

ISO7 1I pixel**2 Isophotalareaatlevel7(pixel^2)

ALPHA_J2000 1D deg SExtractornamedCentroidskypositionrightascension(J2000)(deg)

DELTA_J2000 1D deg SEXtractornamedCentroidskypositiondeclination(J2000)(deg)

SG2DPHOT 1I 2DPhotStarGalaxyclassifier(1forhighconfidencestar)

HTM 1J HierarchicalTriangularMesh(level25)

FIELD_POS 1I Referencenumbertofieldparameters

THELI_NAME 14A NameofthepointinginTHELIconvention

KIDS_TILE 14A NameofthepointinginAWconvention

GAaPphotometryparametesfromtheVIKINGZ,Y,J,H,Kspawprints

EXTINCTION_Z 1E mag GalacticextinctionintheZband(mag)

EXTINCTION_Y 1E mag GalacticextinctionintheYband(mag)

EXTINCTION_J 1E mag GalacticextinctionintheJband(mag)

EXTINCTION_H 1E mag GalacticextinctionintheHband(mag)

EXTINCTION_Ks 1E mag GalacticextinctionintheKsband(mag)

MAG_GAAP_0p7_Z 1E mag Zmagnitude

MAGERR_GAAP_0p7_Z 1E mag Zmagnitudeerror

FLUX_GAAP_0p7_Z 1E count Zflux

FLUXERR_GAAP_0p7_Z 1E count Zfluxerror

FLAG_GAAP_0p7_Z 1I GAAPphotometryFlag

MAG_GAAP_1p0_Z 1E mag Zmagnitude

MAGERR_GAAP_1p0_Z 1E mag Zmagnitudeerror

FLUX_GAAP_1p0_Z 1E count Zflux

FLUXERR_GAAP_1p0_Z 1E count Zfluxerror

29

FLAG_GAAP_1p0_Z 1I GAAPphotometryFlag

MAG_GAAP_0p7_Y 1E mag Ymagnitude

MAGERR_GAAP_0p7_Y 1E mag Ymagnitudeerror

FLUX_GAAP_0p7_Y 1E count Yflux

FLUXERR_GAAP_0p7_Y 1E count Yfluxerror

FLAG_GAAP_0p7_Y 1I GAAPphotometryFlag

MAG_GAAP_1p0_Y 1E mag Ymagnitude

MAGERR_GAAP_1p0_Y 1E mag Ymagnitudeerror

FLUX_GAAP_1p0_Y 1E count Yflux

FLUXERR_GAAP_1p0_Y 1E count Yfluxerror

FLAG_GAAP_1p0_Y 1I GAAPphotometryFlag

MAG_GAAP_0p7_J 1E mag Jmagnitude

MAGERR_GAAP_0p7_J 1E mag Jmagnitudeerror

FLUX_GAAP_0p7_J 1E count Jflux

FLUXERR_GAAP_0p7_J 1E count Jfluxerror

FLAG_GAAP_0p7_J 1I GAAPphotometryFlag

MAG_GAAP_1p0_J 1E mag Jmagnitude

MAGERR_GAAP_1p0_J 1E mag Jmagnitudeerror

FLUX_GAAP_1p0_J 1E count Jflux

FLUXERR_GAAP_1p0_J 1E count Jfluxerror

FLAG_GAAP_1p0_J 1I GAAPphotometryFlag

MAG_GAAP_0p7_H 1E mag Hmagnitude

MAGERR_GAAP_0p7_H 1E mag Hmagnitudeerror

FLUX_GAAP_0p7_H 1E count Hflux

FLUXERR_GAAP_0p7_H 1E count Hfluxerror

FLAG_GAAP_0p7_H 1I GAAPphotometryFlag

MAG_GAAP_1p0_H 1E mag Hmagnitude

MAGERR_GAAP_1p0_H 1E mag Hmagnitudeerror

FLUX_GAAP_1p0_H 1E count Hflux

FLUXERR_GAAP_1p0_H 1E count Hfluxerror

FLAG_GAAP_1p0_H 1I GAAPphotometryFlag

MAG_GAAP_0p7_Ks 1E mag Ksmagnitude

MAGERR_GAAP_0p7_Ks 1E mag Ksmagnitudeerror

FLUX_GAAP_0p7_Ks 1E count Ksflux

FLUXERR_GAAP_0p7_Ks 1E count Ksfluxerror

FLAG_GAAP_0p7_Ks 1I GAAPphotometryFlag

MAG_GAAP_1p0_Ks 1E mag Ksmagnitude

MAGERR_GAAP_1p0_Ks 1E mag Ksmagnitudeerror

FLUX_GAAP_1p0_Ks 1E count Ksflux

FLUXERR_GAAP_1p0_Ks 1E count Ksfluxerror

FLAG_GAAP_1p0_Ks 1I GAAPphotometryFlag

Optimalaperture9-bandGaaPphotometry

MAG_GAAP_u 1E mag u-bandGAaPmagnitudeoptimalmin_aper

MAGERR_GAAP_u 1E mag u-bandGAaPmagnitudeerroroptimalmin_aper

FLUX_GAAP_u 1E count u-bandGAaPfluxoptimalmin_aper

FLUXERR_GAAP_u 1E count u-bandGAaPfluxerroroptimalmin_aper

FLAG_GAAP_u 1I GAaPFlagforMAG_GAAP_uoptimalmin_aper

MAG_GAAP_g 1E mag g-bandGAaPmagnitudeoptimalmin_aper

30

MAGERR_GAAP_g 1E mag g-bandGAaPmagnitudeerroroptimalmin_aper

FLUX_GAAP_g 1E count g-bandGAaPfluxoptimalmin_aper

FLUXERR_GAAP_g 1E count g-bandGAaPfluxerroroptimalmin_aper

FLAG_GAAP_g 1I GAaPFlagforMAG_GAAP_goptimalmin_aper

MAG_GAAP_r 1E mag r-bandGAaPmagnitudeoptimalmin_aper

MAGERR_GAAP_r 1E mag r-bandGAaPmagnitudeerroroptimalmin_aper

FLUX_GAAP_r 1E count r-bandGAaPfluxoptimalmin_aper

FLUXERR_GAAP_r 1E count r-bandGAaPfluxerroroptimalmin_aper

FLAG_GAAP_r 1I GAaPFlagforMAG_GAAP_roptimalmin_aper

MAG_GAAP_i 1E mag i-bandGAaPmagnitudeoptimalmin_aper

MAGERR_GAAP_i 1E mag i-bandGAaPmagnitudeerroroptimalmin_aper

FLUX_GAAP_i 1E count i-bandGAaPfluxoptimalmin_aper

FLUXERR_GAAP_i 1E count i-bandGAaPfluxerroroptimalmin_aper

FLAG_GAAP_i 1I GAaPFlagforMAG_GAAP_ioptimalmin_aper

MAG_GAAP_Z 1E mag Z-bandGAaPmagnitudeoptimalmin_aper

MAGERR_GAAP_Z 1E mag Z-bandGAaPmagnitudeerroroptimalmin_aper

FLUX_GAAP_Z 1E count Z-bandGAaPfluxoptimalmin_aper

FLUXERR_GAAP_Z 1E count Z-bandGAaPfluxerroroptimalmin_aper

FLAG_GAAP_Z 1I GAaPFlagforMAG_GAAP_Zoptimalmin_aper

MAG_GAAP_Y 1E mag Y-bandGAaPmagnitudeoptimalmin_aper

MAGERR_GAAP_Y 1E mag Y-bandGAaPmagnitudeerroroptimalmin_aper

FLUX_GAAP_Y 1E count Y-bandGAaPfluxoptimalmin_aper

FLUXERR_GAAP_Y 1E count Y-bandGAaPfluxerroroptimalmin_aper

FLAG_GAAP_Y 1I GAaPFlagforMAG_GAAP_Yoptimalmin_aper

MAG_GAAP_J 1E mag J-bandGAaPmagnitudeoptimalmin_aper

MAGERR_GAAP_J 1E mag J-bandGAaPmagnitudeerroroptimalmin_aper

FLUX_GAAP_J 1E count J-bandGAaPfluxoptimalmin_aper

FLUXERR_GAAP_J 1E count J-bandGAaPfluxerroroptimalmin_aper

FLAG_GAAP_J 1I GAaPFlagforMAG_GAAP_Joptimalmin_aper

MAG_GAAP_H 1E mag H-bandGAaPmagnitudeoptimalmin_aper

MAGERR_GAAP_H 1E mag H-bandGAaPmagnitudeerroroptimalmin_aper

FLUX_GAAP_H 1E count H-bandGAaPfluxoptimalmin_aper

FLUXERR_GAAP_H 1E count H-bandGAaPfluxerroroptimalmin_aper

FLAG_GAAP_H 1I GAaPFlagforMAG_GAAP_Hoptimalmin_aper

MAG_GAAP_Ks 1E mag Ks-bandGAaPmagnitudeoptimalmin_aper

MAGERR_GAAP_Ks 1E mag Ks-bandGAaPmagnitudeerroroptimalmin_aper

FLUX_GAAP_Ks 1E count Ks-bandGAaPfluxoptimalmin_aper

FLUXERR_GAAP_Ks 1E count Ks-bandGAaPfluxerroroptimalmin_aper

FLAG_GAAP_Ks 1I GAaPFlagforMAG_GAAP_Ksoptimalmin_aper

Agaper 1E arcsec MajoraxisofGAaPapertureoptimalmin_aper(arcsec)

Bgaper 1E arcsec MinoraxisofGAaPapertureoptimalmin_aper(arcsec)

Photometricredshiftestimate

Z_B 1D 9-bandBPZredshiftestimate;peakofposteriorprobabilitydis-tribution

Z_B_MIN 1D Lowerboundofthe68%confidenceintervalofZ_B

Z_B_MAX 1D Upperboundofthe68%confidenceintervalofZ_B

T_B 1D SpectraltypecorrespondingtoZ_B

ODDS 1D EmpiricalODDSofZ_B

31

Z_ML 1D 9-bandBPZmaximumlikelihoodredshift

T_ML 1D SpectraltypecorrespondingtoZ_ML

CHI_SQUARED_BPZ 1D chisqaredvalueassociatedwithZ_B

M_0 1D mag ReferencemagnitudeforBPZprior

BPZ_FILT 1J filterswithgoodphotometry(BPZ)

NBPZ_FILT 1J numberoffilterswithgoodphot.(BPZ)

BPZ_NONDETFILT 1J filterswithfaintphotometry(BPZ)

NBPZ_NONDETFILT 1J numberoffilterswithfaintphot.(BPZ)

BPZ_FLAGFILT 1J flaggedfilters(BPZ)

NBPZ_FLAGFILT 1J numberofflaggedfilters(BPZ)

MASK 1J 9-bandmaskinformation

Extinction-correctedcolours

COLOUR_GAAP_u_g 1E mag u-gcolourindex

COLOUR_GAAP_g_r 1E mag g-rcolourindex

COLOUR_GAAP_r_i 1E mag r-icolourindex

COLOUR_GAAP_i_Z 1E mag i-Zcolourindex

COLOUR_GAAP_Z_Y 1E mag Z-Ycolourindex

COLOUR_GAAP_Y_J 1E mag Y-Jcolourindex

COLOUR_GAAP_J_H 1E mag J-Hcolourindex

COLOUR_GAAP_H_Ks 1E mag H-Kscolourindex

Table8.MASKvaluesinthe9-bandcatalogues

Bit Meaning0 THELImanualmask(veryconservative)1 THELIautomaticlargestarhalomask(faint)2 THELIautomaticlargestarhalomask(bright)orbrightstarmask3 Manualmaskofregionsaroundglobularclusters,Fornaxdwarf,ISSpassage4 THELIvoidmask,orasteroids,orweight=05 VIKINGZbandimagemasked6 VIKINGYbandimagemasked7 VIKINGJbandimagemasked8 VIKINGHbandimagemasked9 VIKINGKsbandimagemasked10 Astro-WISEubandhalo+stellarPULECENELLAmaskorweight=011 Astro-WISEgbandhalo+stellarPULECENELLAmaskorweight=012 Astro-WISErbandhalo+stellarPULECENELLAmaskorweight=013 Astro-WISEibandhalo+stellarPULECENELLAmaskorweight=014 ObjectoutsidetheRA/DECcutforitstile15 Notused(reservedassignbitinFITS2-byteinteger)

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Acknowledgements Thefollowingacknowledgmentisvalidatthemomentofwritingthisdocument.Foranup-to-dateversion,pleasevisitthefollowingwebpage:http://kids.strw.leidenuniv.nl/DR4/acknowledgements.php

Usersofdatafromthisreleaseshouldcite“Kuijkenetal.(2019)”.(referencetobeupdateduponpublication)

Pleaseusethefollowingstatementinyourarticleswhenusingthesedata:

BasedonobservationsmadewithESOTelescopesattheLaSillaParanalObservatoryun-derprogrammeIDs177.A-3016,177.A-3017,177.A-3018and179.A-2004,andondataproductsproducedbytheKiDSconsortium.TheKiDSproductionteamacknowledgessup-portfrom:DeutscheForschungsgemeinschaft,ERC,NOVAandNWO-Mgrants;Target;theUniversityofPadova,andtheUniversityFedericoII(Naples).