G f fGalaxy cluster finding in the era of large area surveysGalaxy cluster finding in the era of large area surveysGalaxy cluster finding in the era of large area surveysy g g yWayne Barkhouse and Cody RudeWayne Barkhouse and Cody RudeWayne Barkhouse and Cody Rudey y

f fDepartment of Physics and Astrophysics University of North DakotaDepartment of Physics and Astrophysics, University of North DakotaDepartment of Physics and Astrophysics, University of North Dakota

Introduction SDSS DR7Introduction SDSS DR7In the era of large area surveys (e g SDSS CFHTLS The red sequence voronoi tessellation and percolationIn the era of large area surveys (e.g., SDSS, CFHTLS, The red sequence voronoi tessellation and percolation

l l t d t ti th d li d t th DR7DES, and LSST) the automatic compilation of a large galaxy cluster detection method was applied to the DR7 , ) p gnumber of galaxy clusters with a well-defined selection release of the SDSS (Abazajian et al. 2009). Clusters werenumber of galaxy clusters with a well-defined selection f i i i i h bi f l l

release of the SDSS (Abazajian et al. 2009). Clusters were detected based on the simultaneous application of i andfunction is an important aspect in the probing of large-scale detected based on the simultaneous application of r−i and p p p g g

structure Galaxy clusters play a key role in constraining i−z color slices (2D).structure. Galaxy clusters play a key role in constraining l i l t ( d h d k ) i th

i co o s ces ( ).cosmological parameters (and hence dark energy) via the z=0.23redshift-distance relation and the growth rate of cosmic

z 0.23redshift distance relation and the growth rate of cosmic str ct re formationstructure formation.

Figure 6 Comparison of the Bgc cluster richness measurementPresented in this poster are preliminary results of an Figure 6. Comparison of the Bgc cluster richness measurement ith N N i d fi d th b f d l iPresented in this poster are preliminary results of an

i ff t t t t l l t f l lwith Ngal. Ngal is defined as the number of red sequence galaxies

on-going effort to extract galaxy clusters from several large detected within 1 Mpc radius of the cluster center, and having a area surveys (e.g., SDSS DR7, CFHTLS, and UKIDSS)

p gmagnitude between m* − 2 mag and m* + 1mag. This is essentiallyarea surveys (e.g., SDSS DR7, CFHTLS, and UKIDSS)

using the red sequence voronoi tessellation and percolationmagnitude between m 2 mag and m 1mag. This is essentially the same definition as that used by Koester et al 2007 The datausing the red sequence voronoi tessellation and percolation the same definition as that used by Koester et al. 2007. The data for this figure was obtained from the galaxy simulation of Song et almethod (see, for example, Ramella et al. 2001; Barkhouse for this figure was obtained from the galaxy simulation of Song et al. 2010 Th b l i th l ft h d d i t th t i l

( , p , ;et al 2006) Cluster candidates are cross correlated with 2010. The cross symbol in the upper-left hand corner depicts the typical et al. 2006). Cluster candidates are cross-correlated with

l i d d l i h iFigure 3. Aitoff equatorial projection in Galactic coordinates of z=0 35 uncertainty in Bgc and Ngal. overlapping X-ray data, and cluster richness estimates are

g q p japproximately 150,000 cluster/group candidates detected from the

z 0.35 y g galpp g y ,provided

approximately 150,000 cluster/group candidates detected from theSDSS DR7 dataprovided. SDSS DR7 data.

UKIDSSUKIDSSUKIDSS

V i T ll ti dVoronoi Tessellation andVoronoi Tessellation and Percolation Techniq ePercolation TechniquePercolation TechniqueTh d t ti f l l t i b d thThe detection of galaxy clusters is based on the over-density of galaxies selected via their location in the color-density of galaxies selected via their location in the colormagnitude plane The early type cluster red sequencemagnitude plane. The early-type cluster red sequence Figure 4. Redshift distribution of cluster/group candidates detectedoccupies a unique position in the cluster color-magnitude from DR7 using the VTP method (green histogram). The red p q p gdiagram as the 4000 Å break shifts to longer observed

g (g g )histogram depicts the maxBCG catalog (Koester et al 2007) whilediagram as the 4000 Å break shifts to longer observed

l h i h i i l d hif Clhistogram depicts the maxBCG catalog (Koester et al. 2007), while the blue histogram represents cluster candidates from Wen et al 2009wavelengths with increasing cluster redshift. Clusters are the blue histogram represents cluster candidates from Wen et al. 2009.g g

detected by searching for spatial over-densities by applying Figure 7 Spatial plot of detected cluster candidatesdetected by searching for spatial over-densities by applyingth VTP t h i t l t l d i d f

Figure 7. Spatial plot of detected cluster candidates from the UKIRT Infrared Deep Sky Survey Clustersthe VTP technique to galaxy catalogs derived from from the UKIRT Infrared Deep Sky Survey. Clusters

d t t d b d 2D d l lioverlapping red sequence slices (width= ± 0 1 mag) The are detected based on 2D red sequence color slices overlapping red sequence slices (width ± 0.1 mag). TheVTP l ith titi th l ti l l i t utilizing the J,H, and K bands.VTP algorithm partitions the galaxy spatial plane into g

polyhedral cells, each containing a unique galaxy. The cellpolyhedral cells, each containing a unique galaxy. The cellsize is determined by the distance between nearest CFHT Ssize is determined by the distance between nearest CFHTLSneighbors and encloses the maximum area nearest to a CFHTLSggiven galaxy Clusters are detected as over densities in thegiven galaxy. Clusters are detected as over-densities in the

b f ll i l i l i l inumber of cells per unit area. Selecting galaxies relative top g gthe red sequence slices provides an estimate of the clusterthe red sequence slices provides an estimate of the cluster

d hif D d i h l f l iredshift. Due to degeneracy in the colors of galaxies at Figure 5. X-ray luminosity (0.5-2 keV) vs. the optical richness higher redshift r−i and i−z colors are required to sample

g y y ( ) pparameter Bgc for a subset of matched objects. The Bgchigher redshift, r i and i z colors are required to sample

d f 0 < < 1 1parameter Bgc for a subset of matched objects. The Bgcrichness measurement is defined as the amplitude of thered sequences for 0 < z < 1.1. richness measurement is defined as the amplitude of the correlation function between the cluster center and its red

Z=0.7correlation function between the cluster center and its red

l l ti ( Y & Elli 2003z=0.7

sequence galaxy population (e.g., Yee & Ellingson 2003; z=0 5

Barkhouse et al. 2006). The X-ray luminosities are taken from z=0.5

) ythe 400 square degree ROSAT PSPC survey (Burenin et al. 2007).the 400 square degree ROSAT PSPC survey (Burenin et al. 2007).

Z=0.05z=1 05z=1.05

z=0.8z 0.8

Figure 8 Redshift distribution of cluster candidatesFigure 8. Redshift distribution of cluster candidates detected from the CFHTLS Deep fields (release T0005)

z=0.4detected from the CFHTLS Deep fields (release T0005). Th d it d d th f th fi ld ( i b d

z=0 23 z=0 27The deep magnitude depths of these fields (e.g., i-band

z=0.23 z=0.27 turnover magnitude~26.3) will help to uncover poor systems Figure 1. Voronoi tessellation Figure 2. Red sequences at high redshifts.Figure 1. Voronoi tessellation on a galaxy distribution

Figure 2. Red sequences (RS) for the early-type

gon a galaxy distribution satisfying the color cut

(RS) for the early-type cluster galaxies based onsatisfying the color cut

t d f l t dcluster galaxies based on

i l ti d lexpected for a cluster red passive evolution models A k l d tsequence at z=0.475. Area and a formation at z=5. Top: Acknowledgmentsq

enclosed within the circle is ap

r−i RS for clusters from 0.05enclosed within the circle is a previously unknown cluster that

r i RS for clusters from 0.05 < z < 0 7 Bottom: i−z RS z=0.35 z=0.44 The authors acknowledge the use of data from the Sloan Digital previously unknown cluster that

is detected as an e tended< z < 0.7. Bottom: i z RS for 0 4 < z < 1 05 Solid

e aut o s ac o edge t e use o data o t e S oa g taSky Survey DR7 the Canada France Hawaii Telescope Legacyis detected as an extended

Cfor 0.4 < z < 1.05. Solid

i * f hFigure 6. SDSS DR7 postage stamp images of four galaxy

Sky Survey DR7, the Canada France Hawaii Telescope Legacy Survey and the UKIRT Infrared Deep Sky SurveyChandra x-ray source points represent m* for each

g p g p g g yclusters of various redshift detected using the red sequence

Survey, and the UKIRT Infrared Deep Sky Survey. (Barkhouse et al. 2006). depicted redshift interval.

clusters of various redshift detected using the red sequenceVTP technique The estimated photometric redshift is given( ) p VTP technique. The estimated photometric redshift is given for each cluster Note the presence of gravitational arcs infor each cluster. Note the presence of gravitational arcs in th t l t l th b ttthe two clusters along the bottom row.