星系团Abell 85的光度函数

Luminosity Functions of Galaxy Cluster Abell 85

基于NASA/IPAC河外星系数据库(NASA/IPAC Extragalactic Database,NED)和Sloan数字巡天(Sloan Digital Sky Survey,SDSS)第8次释放的数据(The Eighth Data Release,DR8),对星系团Abell 85(以下简称A85)的2倍动力学特征半径2r_(200)内的光度函数(Luminosity Function,LF)进行了研究.研究表明,A85的光度函数在Sloan巡天5个波段用Schechter函数均能拟合得很好.在u、g和z波段光度函数都显示出1个下凹.早型星系r波段的两个最佳拟合参数(r波段特征绝对星等和暗端的陡度)分别为M_r~*=-21.14_(-0.17)^(+0.17)mag,α=-0.83_(-0.14)^(+0.12),晚型星系为M_r~*=-21.98_(-0.98)^(+0.84)mag,α=-1.5_(-0.35)^(+0.24).早型星系的特征星等暗于晚型星系,而暗端比晚型星系要平坦得多.早型星系的光度函数在-20.5^-20.0 mag下凹.将1.5r_(200)范围内的星系按距离团中心的远近划分为3个环状区域,发现距离团中心越近,光度函数的暗端越陡,特征星等越亮.

We present the luminosity function （LF） of the galaxy cluster Abell 85 based on the photometric and spectroscopic data from NASA/IPAC Extragalactic Database （NED） and the Eighth Data Release of Sloan Digital Sky Survey （SDSS-DR8） within the dynami- cal radius 2r200. It is shown that the LF of A85 can be fitted well with a single Schechter function in all five bands from SDSS, and a dip is shown in u, g, and z bands, respectively. The best-fitting parameters （the characteristic absolute magnitude in r band and the slope ＂）1 1A＋0.17 mag at the faint end of the luminosity function） of Schechter function are Mr＊=-21.14-0.17^＋0.171;mag,Q=-0.83±-0.14^＋0.12 for early-type galaxies, andMr＊=-21.98-0.98^＋0.84mag,a=-1.5-0.35^＋0.24 for late-type galaxies, respectively. The LF of early-type galaxies shows a dip around M＊ -20.5 to -20.0 mag. We also investigate the LFs in three cluster-centric annuli within 1.5r2oo, and find that the closer the distance from the cluster center, the steeper the faint- end slope, and the brighter the characteristic magnitude.