You will be presented with the full text of a science research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
catalogs of galaxy clusters have provided useful data for numbers of works in the field of observational cosmology .
the popular catalogs of nearby clusters include those by abell(1958 ) , zwicky et al .
( 1961 - 68 ) , abell , corwin , and olowin ( 1989 , hereafter aco ) , lumsden et al .
( 1992 ) , dalton et al .
however , these catalogs are claimed to suffer from incompleteness and contamination because clusters in these catalogs are identified basically by finding local peaks of surface number density of galaxies in the sky .
a new cluster - finding algorithm , matched - filter , was proposed by postman et al .
( 1996 ) and it is becoming a standard way for finding , especially , distant clusters .
this time i have applied matched - filter to the 3.3 million galaxy sample from the apm galaxy survey ( maddox et al .
1990a , 1990b ) and constructed a new catalog of nearby clusters covering about 5800 deg@xmath0 in the southern galactic cap .
in this work , a matched - filter algorithm by kawasaki et al .
( 1998 ) is used . simultaneously using two - dimensional positions and apparent magnitudes of galaxies ,
matched - filter has several advantages over the classical cluster - finding algorithms such as count - in - cells which use only galaxy positions : ( i ) much poorer clusters which were undetectable with classical techniques can be found , ( ii ) spurious detection rate of non - physical clusters is greatly suppressed , and ( iii ) rough estimates of redshift and richness of clusters are obtained as byproducts of detection ( for details , see kawasaki et al .
1998 ) .
figure 1 shows a demonstration of matched - filter s ability of finding distant / poor clusters which count - in - cells can not find .
as the unit of processing the whole data , 81 subregions with 10@xmath310@xmath4 area are defined as shown in figure 2 . the galaxy distribution in one of the subregion is shown in figure 3 , and a ` richness map ' , the output of matched - filter , is shown in figure 4 .
the cluster candidates appear as peaks in the gray scale . here
cluster candidates with estimated richness @xmath5 ( similar to abell richness class 0 ) are compiled to the preliminary catalog .
they are shown with the plus marks in figure 4 .
for nearby apparent clusters , figure 4 shows that there is generally a good correspondence between our sample and abell / aco clusters .
however , it is also shown that some apparent candidates are missed in aco catalog .
aco clusters which are not cataloged in our sample are less rich ( @xmath6 ) ones .
our cluster sample seems to be complete up to @xmath7 , twice deeper than the completeness limit for aco clusters with measured redshifts . for @xmath8
, there may exist a significant fraction of contamination .
incidentally noting , figure 6 seems to show the non - uniformity of cluster distribution on 100mpc scale .
abell , g. o. 1958 , apjs , 3 , 211 abell , g. o. , corwin , h. g. , & olowin , r. p. 1989 , apjs , 70 , 1 ( aco ) dalton , g. b. , efstathiou , g. , maddox , s. j. , & sutherland , w. j. 1994 , mnras , 269 , 151 kawasaki , w. , shimasaku , k. , doi , m. , & okamura , s. 1998 , a&as , 130 , 567 lumsden , s. l. , nichol , r. c. , collins , c. a. , & guzzo , l. 1992 , mnras , 258 , 1 maddox , s. j. , sutherland , w. j. , efstathiou , g. , & loveday , j. 1990a , mnras , 243 , 692 maddox , s. j. , efstathiou , g. , & sutherland , w. j. 1990b , mnras , 246 , 433 postman , m. , lubin , l. m. , gunn , j. e. , oke , j. b. , hoessel , j. g. , schneider , d. p. , & christensen , j. a. 1996 , aj , 111 , 615 zwicky , f. , herzog , e. , wild , p. , karpowicz , m. , & kowal , c. t. 1961 - 68 , _ catalogue of galaxies and clusters of galaxies _ , ( zrich : l. speich )
a catalog of nearby clusters in the 5800 deg@xmath0 area in the southern galactic cap is constructed by applying a matched - filter cluster - finding algorithm to the sample of 3.3 million galaxies from the apm galaxy survey . 
 i have preliminarily detected more than 4000 cluster candidates with estimated redshift of less than 0.2 and with richness similar to those of aco clusters . 
 generally , a good correspondence is found between the nearest cluster candidates in our catalog and the aco clusters which have measured redshift . while the aco catalog becomes incomplete at @xmath1 , the completeness limit of our cluster catalog reaches @xmath2 .