Detection of cosmic filaments using the Candy model

Jorge Mateu‡

Description

Detection of cosmic filaments using the Candy model Radu S. Stoica? Departament de Matematiques, Universitat Jaume I, Campus Riu Sec, E-12071 Castello, Spain Vicent J. Martınez† Observatori Astronomic de la Universitat de Valencia, Apartat de correus 22085, 46075 Valencia, Spain Jorge Mateu‡ Departament de Matematiques, Universitat Jaume I, Campus Riu Sec, E-12071 Castello, Spain Enn Saar Tartu Observatoorium, To˜ravere, 61602 Estonia (Dated: May 19, 2004) Abstract We propose to apply a marked point process to automatically delineate filaments of the large- scale structure in redshift catalogues. We illustrate the feasibility of the idea on an example of simulated catalogues, describe the procedure, and characterize the results. We find the distribution of the length of the filaments, and suggest how to use this approach to obtain other statistical characteristics of filamentary networks. PACS numbers: 98.65.Dx, 02.70.Rr, 42.30.Sy ?Electronic address: †Electronic address: ‡Electronic address: Electronic address: 1

• lebesgue measure


• both slices


• measure exhibits no


• combines both local


• large-scale structure


• marked point


• universitat jaume


• observatori astronomic de la universitat de valencia

Sujets

• Lebesgue measure
• Observable universe

Informations

• Publié par: profil-urra-2012
• Nombre de lectures: 14
• Langue: English
• Poids de l'ouvrage: 3 Mo

Extrait

DetectionofcosmicfilamentsusingtheCandymodel RaduS.Stoica ∗ DepartamentdeMatema`tiques,UniversitatJaumeI, CampusRiuSec,E-12071Castello´,Spain VicentJ.Martı´nez † ObservatoriAstrono`micdelaUniversitatdeVale`ncia, Apartatdecorreus22085,46075Vale`ncia,Spain JorgeMateu ‡ DepartamentdeMatematiques,UniversitatJaumeI, CampusRiuSec,E-12071Castell´o,Spain EnnSaar § TartuObservatoorium,To˜ravere,61602Estonia (Dated:May19,2004) Abstract Weproposetoapplyamarkedpointprocesstoautomaticallydelineatefilamentsofthelarge- scalestructureinredshiftcatalogues.Weillustratethefeasibilityoftheideaonanexampleof simulatedcatalogues,describetheprocedure,andcharacterizetheresults.Wefindthedistribution ofthelengthofthefilaments,andsuggesthowtousethisapproachtoobtainotherstatistical characteristicsoffilamentarynetworks. PACSnumbers:98.65.Dx,02.70.Rr,42.30.Sy ∗ Electronicaddress: [e-mail] † Electronicaddress: [e-mail] ‡ Electronicaddress: [e-mail] § Electronicaddress: [e-mail] 1

I.INTRODUCTION Thelarge-scalestructureoftheUniverseisstudiedbycreatinggalaxymaps–positions ofthousands(afewyearsago)andmillions(nowadays)ofgalaxiesinspace.Theangular positionsofgalaxiesarerelativelyeasytomeasure,buttheirdistancescanbeestimatedonly bymeasuringtheirrecessionvelocities.Thelattertaskisdifficult,especiallyforfaintdistant objects,andthusreallydetailedmapsofgalaxieshavestartedtoappearonlylately.An additionalcaveatisthattherecessionvelocitiescontainacontributionfromthedynamical velocityofagalaxy,sotheapparentdistancesofgalaxiesareinerror.Suchmapsarecalled ’redshiftspace’maps,butthedistanceerrorsarenotasseriousastochangetheoverall pictureofthelarge-scalestructure. Anoverviewofsuchgalaxymapsisgivenin[1].Asanexample,wepresentheretwo maps.Thefirstmapcomesfromawell-knownrecentgalaxysurvey,theLasCampanas RedshiftSurvey(LCRS,[23]).Thissurveymeasuredtheredshifts(recessionvelocities)of galaxiesinsixslicesofwidthof80 ◦ andofthicknessof1.5 ◦ ;atypicalnumberofgalaxiesin asliceisabout4000,andthedepthofthesurveyisabout575h −1 Mpc[31](corresponding toaredshiftz=0.2forthestandardcosmologicalmodel).Amapofoneoftheslices(the −42 ◦ slice)isshowninFig.1,intheupperpanel. Theothermapweshowisfromthemostrecent,ongoingsurvey,theSloanDigitalSky Survey(SDSS,[29]).ThissurveywillmeasurefaintergalaxiesthantheLCRS,willreach deeperinspaceandwillfinallycoverafulladjointπsterradiansofthesky.Thedatathat havebeenreleasedbynowconsistalsoofseparateslices;wechoseacontiguoussliceof2.5 ◦ thickand60 ◦ wide(DataRelease1,theslicewiththemean’surveycoordinate’η≈−23 ◦ ). ThedepthoftheSDSSmaingalaxysampleisabout840h −1 Mpc(theredshiftz=0.3).The mapoftheselectedslice,containing10886galaxies,isshowninFig.1,inthelowerpanel. Thedominantfeatureofthesemaps,asofallothergalaxymapsofthelarge-scalestruc- tureoftheuniverse,isthenetworkoffilamentsofdifferentsizeandcontrast,alongwith relativelyemptyvoidsbetweenthefilaments.Thefilamentarynetworkcontainsdifferent scales,wheresmaller-scalefilamentsarealsolessprominent.Thegradualdisappearance ofstructureswithincreasingdistanceisduetothefactthattheapparentluminosityofa galaxyisthefainterthemoredistantitis,andinmoredistantregionswecanobserveonly afewofthebrightestgalaxies. 2