The Structure of Supervoids { I: Void Hierarchy in the Northern Local
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AA manuscript no will b e inserted by hand later ASTRONOMY AND Your thesaurus co des are ASTROPHYSICS The Structure of Sup ervoids I Void Hierarchy in the Northern Lo cal Sup ervoid 1 2 2 34 1 2 Ulrich Lindner Jaan Einasto Maret Einasto Wolfram Freudling Klaus Fricke and Erik Tago 1 University Observatory D GottingenGermany 2 Tartu Astrophysical Observatory EE Toravere Estonia 3 Space Telescope Europ ean Co ordinating Facility D Garching Germany 4 Europ ean Southern Observatory D Garching Germany Accepted for publication February Introduction Abstract Sup ervoids are regions in the lo cal Universe The presence of voids in the distribution of galaxies has which do not contain rich clusters of galaxies In order to b een discovered even in early redshift surveys of galaxies investigate the distribution of galaxies in and around su eg Joeveer Einasto Tarenghi et al Tit p ervoids we have studied the closest example the North Gregory and Tully Fisher Further stud ern Local Void It is dened as the region b etween the Lo ies show that the largest voids are those delineated by cal Coma and the Hercules sup erclusters which is well rich clusters and sup erclusters of galaxies We call these covered by available redshift surveys voids sup ervoids This denition is analogous to the def We nd that this sup ervoid is not empty but it con inition of sup erclusters which consist of rich clusters of tains small galaxy systems and p o or clusters of galax galaxies and outline the regions of sup ervoids A classi ies We study the cosmography of this void by analyz cal example of a sup ervoid is the Bo otes void Kirshner et ing the distribution of p o or clusters of galaxies elliptical al The Bo otes void is lo cated at a distance of ab out and other galaxies in two pro jections We present a cata 1 h Mp c from us This void is surrounded by the logue of voids dened by galaxies of dierent morpholog Hercules Corona Borealis and Bo otes sup erclusters and ical type and luminosity and analyze mean diameters of 1 has a diameter of at least h Mp c Other cluster de voids in dierent environments ned voids are the Perseus void b ehind the PerseusPisces This analysis shows that sizes of voids and prop erties sup ercluster Einasto Joeveer and Saar and the su of void walls are related Voids dened by p o or clusters p ervoid describ ed by Bahcall Soneira The clos of galaxies and by bright elliptical galaxies have a mean 1 est sup ervoid the Northern Lo cal void hereafter NLV diameter of up to h Mp c Faint latetype galaxies Einasto et al is lo cated in front of the Hercules divide these voids into smaller voids The faintest galaxies sup ercluster This void is b ordered by the Lo cal and the we can study are outlining voids with mean diameters of 1 Coma sup erclusters and by walls b etween these sup erclus ab out h Mp c Voids lo cated in a highdensity envi ters and the Hercules sup ercluster From the southern side astro-ph/9503044 10 Mar 1995 ronment are smaller than voids in lowdensity regions the NLV reaches the Cetus wall and the Shapley sup er The dep endence of void diameters on the type and cluster cf Einasto et al hereafter EETDA and luminosity of galaxies as well as on the largescale envi Figure a ronment shows that voids form a hierarchical system Catalogues of clusterdened sup erclusters and su p ervoids were presented by Batuski and Burns Key words cosmology observations galaxies cluster and EETDA The mean diameter of sup ervoids is ab out ing largescale structure of the Universe 1 h Mp c EETDA Einasto et al hereafter EEG Previous studies have shown that sup ervoids are not completely empty In the Bo otes void a number of galaxies have b een found Balzano Weedman Zmo o dy et Send oprint requests to Ulrich LindnerUniversity al Peimbert TorresPeimbert Szomoru et Observatory Geismarlandstr D Gottingen al Szomoru Gorkom and Gregg Szomoru et Germany U Lindner et al Void Hierarchy in the Northern Lo cal Sup ervoid Fig a Distributi on of rich clusters of galaxies and strong radio galaxies in sup ergalactic co ordinates Clusters of galaxies which are members of rich sup erclusters with at least members cf EETDA are plotted as lled circles lo cated in interval 1 1 X h Mp c or op en circles lo cated in interval X h Mp c dierent notation enables to distinguish members of the Shapley sup ercluster isolated clusters and clusters in p o or sup erclusters are plotted as small dots radio galaxies as crosses The zone of avoidance is given by dashed lines Identications of some sup erclusters are given CB stands for Corona Borealis AC for AquariusCapricornus Box shows the contour of the region of NLV plotted in Figure b al The same has b een found for the void near the The Hercules region has attracted the attention of as PerseusPisces sup ercluster Weinberg et al and tronomers since Shapley discovered the Hercules in the Northern Lo cal Sup ervoid Freudling et al sup ercluster The spatial structure of the lowdensity re These studies show that dwarf galaxies in large voids tend gion in front of the Hercules sup ercluster was studied by to form small systems In particular Szomoru et al have Joeveer Einasto Zeldovich Einasto and Shan shown that galaxies in the Bo otes void cluster to form darin Einasto et al and Freudling Haynes groups and laments of galaxies and Giovanelli This lowdensity region was inde p endently discovered and studied by Tully Tully et al by the CfA team de Lapparent et The aim of the present pap er is to investigate the de al Geller and Huchra Vogeley Geller tailed structure of the area of the Northern Lo cal void and Huchra Vogeley et al ab and by which will serve as an example of prop erties of sup ervoids Shaver More recent redshift surveys of the area to guide future investigations of sup ervoids We investi include Freudling et al and Tarenghi et al gate in detail the prop erties of voids in the Northern Lo These studies have shown that the region of NLV is lled cal sup ervoid and in the neighboring sup erclusters the with a network of faint galaxy systems which divide the Lo cal Coma and Hercules sup erclusters The closeness of sup ervoid into smaller voids see Figure b Mean diame this sup ervoid and the surrounding sup erclusters gives us ters of galaxydened voids are times smaller than a unique p ossibility to compare structures of galaxies in diameters of sup ervoids These systems are p opulated low and highdensity environment Dierences if found mostly by spiral galaxies Tago et al give imp ortant information on the galaxy formation in various environments U Lindner et al Void Hierarchy in the Northern Lo cal Sup ervoid Fig b Distribution of galax ies in sup ergalactic co ordinates 1 in a sheet X h Mp c Bright galaxies M are plotted with lled circles fainter galaxies M with op en circles Solid lines show equidensity contours found by Gaussian smo othing of the density eld with disp ersion 1 h Mp c cf Section The mean density is denoted as Highdensity regions corresp ond to sup erclusters lowdensity regions to the lo cal sup ervoid intermedi ate density regions to density enhancements in the sup ervoid the sup ercluster outskirts and the walls b etween them We see the Lo cal the Coma and the Hercules sup er clusters in the lower left lower right and upp er right part of the gure resp ectively The in termediate density region in the right part of the gure b etween the Coma and the Hercules su p erclusters b elongs to the Great Wall in the direction of the NLV and Coma and Hercules sup er Recently several catalogues of galaxydened voids clusters In x we present a void catalogue in this region have b een published Kaufmann and Fairall here of sky In x we analyze the distribution of void diameters after KF HaqueCopilah and Basu hereafter HB dened by p o or clusters of galaxies and by galaxies of dif and Slezak et al hereafter SLB In these catalogues ferent morphological type and luminosity In x we discuss however no distinction has b een made b etween voids de our results The pap er ends with a summary of principal ned by dierent types of ob jects By contrast in this conclusions work we emphasize a comparison of prop erties of voids dened by galaxies of various luminosity and morphol Throughout this pap er we use a Hubble constant of 1 1 ogy lo cated in dierent environments Thereby we con H h km s Mp c rm previous results by EEG and Einasto et al hereafter EEGS suggesting that the void analysis char acterizes some prop erties of the distribution of galaxies The data b etter than other statistics esp ecially in lowdensity re The Hercules sup ercluster covers a large area of the sky gions EEG and EEGS studied the void prop erties in the north of the celestial equator in the right ascension range direction of the Coma sup ercluster applying mean void h h b etween Centers of the Lo cal and Coma diameter statistics and the void probability function us h h sup erclusters lie also in the region b etween ing redshift data available in the late s In the present and Strong galactic obscuration starts at pap er we shall use a much deep er and larger dataset and h Therefore we select for our study the region combine the quantitative analysis with a cosmographic de h h and The main b o dy of the Her scription of the galaxy distribution cules sup ercluster lies b etween redshifts and 1 km s Thus we considered only redshifts up to The pap er is organized as follows In x we describ e 1 km s We use cubic