A THREE DIMENSIONAL OBJECT POINT PROCESS FOR DETECTION OF COSMIC
21 Pages
English
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A THREE DIMENSIONAL OBJECT POINT PROCESS FOR DETECTION OF COSMIC

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21 Pages
English

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A THREE DIMENSIONAL OBJECT POINT PROCESS FOR DETECTION OF COSMIC FILAMENTS by Radu S. Stoica Vicent J. Martinez Enn Saar Research Report No. 17 January 2006 Unite de Biometrie Institut National de la Recherche Agronomique Avignon, France

  • exact simulation methods

  • poisson law

  • filament

  • galaxy maps

  • point process

  • methods based

  • methods require local

  • both local

  • distance can


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A THREE DIMENSIONAL OBJECT POINT PROCESS FOR DETECTION OF COSMIC FILAMENTS
by
Radu S. Stoica Vicent J. Martinez Enn Saar
Research Report No. 17 January 2006
Unite de Biometrie Institut National de la Recherche Agronomique Avignon, France http://www.avignon.inra.fr/biometrie
A three dimensional object point process for detection of cosmic lamen ts
R.S. Stoica 1 , V.J. Martinez 2 and E. Saar 3 1 INRAUniteBiometrie,DomaineSt.PaulsiteAgroparc, 84914 Avignon Cedex 9, France. E-mail : radu.stoica@avignon.inra.fr 2 ObservatoriAstronomicdelaUniversitatdeValencia, Apartatdecorreus22085,46075Valencia,Spain.Email:martinez@uv.es 3 TartuObservatoorium,To˜ravere, 61602 Estonia. Email : saar@aai.ee Summary . We propose to apply an object point process to automatically delineate laments of the large-scale structure in redshift catalogues. We illustrate the feasibility of the idea on an example of the recent 2dF Galaxy Redshift Survey, describe the procedure, and characterize the results. Keywords : Object point processes, Bisous model, laments, cosmology, large-scale structure
1. Introduction The large-scale structure of the Universe is studied by creating galaxy maps – positions of thousands, a few years ago, and millions, nowadays, of galaxies in space. The angular positions of galaxies are relatively easy to measure, but their distances can be estimated only by measuring their recession velocities. The latter task is dicult, especially for faint distant objects, and thus really detailed maps of galaxies have started to appear only lately. An additional caveat is that the recession velocities contain a contribution from the dynamical velocity of a galaxy, so the apparent distances of galaxies are in error. Such maps are called ’redshift space’ maps, but the distance errors are not as serious as to change the overall picture of the large-scale structure. An overview of such galaxy maps is given in Mart nez and Saar (2002). As an example, we present here a map from a recently completed 2dF Galaxy Redshift Survey (2dFGRS, Colless et al. (2001)). This survey measured the redshifts (recession velocities) of galaxies in about 1500 square degrees, up to the distances of about 700 h  1 Mpc (corresponding to a redshift z = 0 . 2 for the standard cosmological model). The redshifts were measured in twodi erentregionsofthesky;Fig.1showsthepositionsofgalaxiesintwo2 . 6  thick slices from both regions. The dominant feature of this map, as of all other galaxy maps of the large-scale structure oftheuniverse,isthenetworkof lamentsofdi erentsizeandcontrast,alongwithrelatively emptyvoidsbetweenthe laments.The lamentarynetworkcontainsdi erentscales,where Distances between galaxies are usually measured in megaparsecs (Mpc); 1Mpc  3  10 24 cm. The constant h is the dimensionless Hubble parameter; the latest determinations give for its value h  0 . 71.