星系群HCG 95中的星系群内光观测研究

Research on the Intra-Group Light in the HCG 95 Group

星系团/群内光(ICL(Intra-Cluster Light)/IGL(Intra-Group Light))可以用来研究星系群和星系团的动力学演化.Hickson致密星系群密度高并且速度弥散低,其致密的环境可以用来研究星系并合和相互作用星系的性质,是研究IGL理想场所之一.利用中国近地天体巡天望远镜(Chinese Near Object Survey Telescope,CNEOST)的观测,获得了星系群HCG 95的g波段和r波段深度成像数据.采用模型拟合方法来测量HCG 95星系群中的IGL光度,并计算了IGL的光度占星系群总光度的比例f_(IGL),在g和r波段的结果分别为3.55%±0.38%和3.78%±0.59%.此外,利用常规的表面亮度阈值截取方法,在g和r波段的结果分别为1.9%-10%和1.5%-10%,与前述结果一致.估算的IGL颜色(g-r=0.78±0.37)与星系群中的HCG 95A和HCG 95C星系的颜色(g-r=0.82-0.85)一致,属于年老星族,表明HCG 95星系群中的IGL可能来自HCG 95A和HCG 95C相互作用剥离出来的物质,也有可能来自近期的吸积.最后,结合其他星系群测量的结果,发现f_(IGL)和其对应的星系群总质量没有关系,但与星系群演化(即早型星系的数目)有关.

The Intra-Group/Cluster Light(IGL/ICL)can be used to study the dynamical evolution of galaxy groups and clusters.Hickson Compact Groups(HCGs)have a high density and a low velocity dispersion,providing a unique environment to study galaxies merger and properties of interacting galaxies.It is also a promising target for the study of IGL.The g and r band deep imaging data of HCG 95 were obtained with Chinese Near Object Survey Telescope(CNEOST).The IGL fraction in HCG 95 is measured with model fitting using GALFIT,giving an IGL fraction(defined by the ratio between the IGL luminosity and the group total luminosity)of 3.55%±0.38%and 3.78%±0.59%in the g and r band,respectively.When applying the surface brightness threshold method,the IGL fraction is 1.9%-10%and 1.5%-10%in the g an r band,respectively.The color of the IGL(g−r=0.78±0.37)is similar to that of the HCG 95A and HCG 95C in the group(g−r=0.82−0.85),suggesting that it is composed by an old population.It is showed that the IGL in the group may be from the stripped material of interaction between HCG 95A and HCG 95C,with little recent accretion.Combined with the IGL fraction measurements from literatures,we find that the IGL fraction shows no clear correlation with the total mass of groups.A positive correlation is found between the IGL fraction and the early-type galaxies fraction of groups,suggesting that the IGL fraction is linked to the evolutionary stage of a group.