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|Groups of Galaxies in the Two Micron All Sky Redshift Survey|
We present the results of applying a percolation algorithm to theinitial release of the Two Micron All Sky Survey Extended SourceCatalog, using subsequently measured redshifts for almost all of thegalaxies with K<11.25 mag. This group catalog is based on the firstnear-IR all-sky flux-limited survey that is complete to|b|=5deg. We explore the dependence of the clustering on thelength and velocity scales involved. The paper describes a groupcatalog, complete to a limiting redshift of 104 kms-1, created by maximizing the number of groups containingthree or more members. A second catalog is also presented, created byrequiring a minimum density contrast of δρ/ρ>=80 toidentify groups. We identify known nearby clusters in the catalogs andcontrast the groups identified in the two catalogs. We examine andcompare the properties of the determined groups and verify that theresults are consistent with the UZC-SSRS2 and northern CfA redshiftsurvey group catalogs. The all-sky nature of the catalog will allow thedevelopment of a flow-field model based on the density field inferredfrom the estimated cluster masses.
|The K-Band Galaxy Luminosity Function|
We measured the K-band luminosity function using a complete sample of4192 morphologically typed 2MASS galaxies withμKs=20 mag arcsec-2 isophotalmagnitudes 7-0.5) galaxies havesimilarly shaped luminosity functions, αe=-0.92+/-0.10and αl=-0.87+/-0.09. The early-type galaxies arebrighter, MK*e=-23.53+/-0.06 mag compared toMK*l=-22.98+/-0.06 mag, but less numerous,n*e=(0.45+/-0.06)×10-2 h3Mpc-3 compared ton*l=(1.01+/-0.13)×10-2 h3Mpc-3 for H0=100 h km s-1Mpc-1, such that the late-type galaxies slightly dominate theK-band luminosity density,jlate/jearly=1.17+/-0.12. Including a factor of1.20+/-0.04 correction for the conversion of the isophotal surveymagnitudes to total magnitudes, the local K-band luminosity density isj=(7.14+/-0.75)×108 h LsolarMpc-3, which implies a stellar mass density relative tocritical of Ω*h=(1.9+/-0.2)×10-3 for aKennicutt initial mass function (IMF) andΩ*h=(3.4+/-0.4)×10-3 for a SalpeterIMF. Our morphological classifications are internally consistent, areconsistent with previous classifications, and lead to luminosityfunctions unaffected by the estimated uncertainties in theclassifications. These luminosity functions accurately predict theK-band number counts and redshift distributions for K<~18 mag, beyondwhich the results depend on galaxy evolution and merger histories. Thispublication makes use of data products from the Two Micron All SkySurvey (2MASS), which is a joint project of the University ofMassachusetts and the Infrared Processing and Analysis Center/CaliforniaInstitute of Technology, funded by the National Aeronautics and SpaceAdministration and the National Science Foundation.
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