标题： 星团中的尘埃：分离星系和星团介质的贡献 显示英文标题

标题： Dust in clusters: separating the contribution of galaxies and intracluster media

摘要： 我们分析了一个包含327组星系团的样本，这些星系团的红移范围为0.06至0.70。利用HERSCHEL HerMES项目的地图和目录，得到了它们平均星际尘埃发射的强限制条件；在每个星系团中心半径为5角分的范围内，观测频率为250、350和500 $\mu$m时获得的95%置信水平（C.L.）限制分别为86.6、48.2和30.9 mJy。根据这些限制条件，并假设典型银河系星际介质的物理参数，我们获得了背景星系因星系团内介质导致的视觉消光的严格上限： $A_V$（95% C.L.） <~$10^{-3}$ 镁。 对于此类尘埃的质量也得出了强限制条件；例如，使用350 $\mu$m处的数据，我们在以星系团为中心、半径为5角分的圆内设定了一个95%的上限值$<10^9M_\odot$。 这相当于星系团总质量的$9.5\times 10^{-6}$，表明星系团内介质的气体与尘埃比例比银河系中的值低大约三个数量级。 分别计算三个红移范围（0.05-0.24、0.24-0.42 和 0.42-0.71）和两个质量范围（$<10^{14}$和$>10^{14}M_\odot$）内的星团总红外光度，发现这两个质量范围内光度随红移（$L\sim z^{1.5}$）的变化非常明显。 结果表明，过去$\sim 6$千兆年的时间里恒星形成率随着时间有明显的下降。 显示英文摘要

摘要： We have analized a sample of 327 clusters of galaxies spanning the range 0.06-0.70 in redshift. Strong constraints on their mean intracluster emission by dust have been obtained using maps and catalogs from the HERSCHEL HerMES project; within a radius of 5 arcmin centered in each cluster, the 95% C.L. limits obtained are 86.6, 48.2 and 30.9 mJy at the observed frequencies of 250, 350 and 500 $\mu$m. From these restrictions, and assuming physical parameters typical of interstellar media in the Milky Way, we have obtained tight upper limits on the visual extinction of background galaxies due to the intracluster media: $A_V$(95% C.L.) <~$10^{-3}$ mags. Strong constraints are also obtained for the mass of such dust; for instance using the data at 350 $\mu$m we establish a 95% upper limit of $<10^9M_\odot$ within a circle with a radius of 5 arcmin centered in the clusters. This corresponds to a fraction of the total mass of the clusters of $9.5\times 10^{-6}$, and indicates a deficiency in the gas-to-dust ratio in the intracluster media by about three orders of magnitude as regards the value found in the Milky Way. Computing the total infrared luminosity of the clusters in three ranges of redshift (0.05-0.24, 0.24-0.42 and 0.42-0.71) and two ranges of mass ($<10^{14}$ and $>10^{14}M_\odot$) respectively, a strong evolution of luminosity in redshift ($L\sim z^{1.5}$) for both ranges of masses is found. The results indicate a strong declining in star formation rate with time in the last $\sim 6$ Gyr.