标题： 室女座星系团吸积区的深紫外光度函数 显示英文标题

标题： Deep UV Luminosity Functions at the Infall Region of the Coma Cluster

摘要： 我们利用深度GALEX观测数据在Coma星系团的流入区域测量了迄今为止最暗的紫外光度函数（LFs）。Coma的紫外LFs在GALEX FUV和NUV波段测量到M_UV = -10.5，比之前的研究暗3.5个星等，并首次达到了Coma中的矮早型星系群体。Schechter暗端斜率（两个GALEX波段中alpha = -1.39）比之前报告的Coma紫外LF研究更平缓，这是由于在暗星等处LF更平坦。高斯加Schechter模型对紫外LFs提供了稍微更好的参数化，导致两个GALEX波段中暗端斜率为~ -1.15。两组分模型给出了比-1更平缓的暗端斜率（拐点），这是针对被动和恒星形成星系分别构建的LFs。恒星形成星系的紫外LFs在M_UV ~ -14处出现拐点，这是由于Coma中恒星质量低于M*=10^8 Msun的矮恒星形成星系缺乏。最近对室女座星系团测量的紫外LFs中也发现了类似的拐点，这表明这可能是本地星系团的共同特征，而场紫外LFs在暗星等处继续上升。我们没有发现预期的被动星系过剩，如果缺失的矮恒星形成星系在星系团内被抑制的话。事实上，矮被动星系和恒星形成星系的LFs在暗星等处都显示出相同的拐点。我们讨论了Coma中缺失的矮恒星形成星系的可能起源及其根据与本地场星系比较所预期的特性。 显示英文摘要

摘要： We have used deep GALEX observations at the infall region of the Coma cluster to measure the faintest UV luminosity functions (LFs) presented for a rich galaxy cluster thus far. The Coma UV LFs are measured to M_UV = -10.5 in the GALEX FUV and NUV bands, or 3.5 mag fainter than previous studies, and reach the dwarf early-type galaxy population in Coma for the first time. The Schechter faint-end slopes (alpha = -1.39 in both GALEX bands) are shallower than reported in previous Coma UV LF studies owing to a flatter LF at faint magnitudes. A Gaussian-plus-Schechter model provides a slightly better parametrization of the UV LFs resulting in a faint-end slope of ~ -1.15 in both GALEX bands. The two-component model gives faint-end slopes shallower than -1 (a turnover) for the LFs constructed separately for passive and star forming galaxies. The UV LFs for star forming galaxies show a turnover at M_UV ~ -14 owing to a deficit of dwarf star forming galaxies in Coma with stellar masses below M*=10^8 Msun. A similar turnover is identified in recent UV LFs measured for the Virgo cluster suggesting this may be a common feature of local galaxy clusters, whereas the field UV LFs continue to rise at faint magnitudes. We did not identify an excess of passive galaxies as would be expected if the missing dwarf star forming galaxies were quenched inside the cluster. In fact, the LFs for both dwarf passive and star forming galaxies show the same turnover at faint magnitudes. We discuss the possible origin of the missing dwarf star forming galaxies in Coma and their expected properties based on comparisons to local field galaxies.