标题： 红移约 z ~ 2 时由 BzK 选择的 ULIRG（超亮红外星系）群体 显示英文标题

标题： The population of BzK selected ULIRGs at z~2

摘要： 我们研究了在起源深空调查（GOODS）北区域的红移 z~2 的 BzK 星系形成的多波段辐射。大部分（82%）的源在斯皮策 MIPS 成像中被单独检测到 24 微米波段，在 VLA 射电数据中四分之一（26%）被检测到。通过射电、亚毫米和 X 射线域的堆叠分析获得了未单独检测到的目标的显著检测结果。典型的红移 z=2 的恒星质量 ~10^{11}Mo 星系是一个超亮红外星系（ULIRG），具有 L_IR ~ 1-2x10^{12}Lo 辐射亮度和 SFR 200-300Mo/yr 恒星形成率，表明 z=2 时 ULIRG 的共动密度至少比本地高出三个数量级。从消光修正后的紫外亮度推导出的恒星形成率平均与较长波长的估计值一致。高 24 微米探测率表明 BzK 星系形成的相对较高的活跃周期，这与 z>1.4 的被动演化星系空间密度的独立测量结果一致。如果 z=2 的初始质量函数（IMF）与本地相似，尤其是不是顶部沉重的 IMF，则表明 z~1.4 时星系恒星质量函数的高质量尾部（>10^{11}Mo）已经完成。 显示英文摘要

摘要： We investigate the multi-wavelength emission of BzK selected star forming galaxies at z~2 in the Great Observatories Origins Deep Survey (GOODS) North region. Most (82%) of the sources are individually detected at 24um in the Spitzer MIPS imaging, and one fourth (26%) in the VLA radio data. Significant detections of the individually undetected objects are obtained through stacking in the radio, submm and X-ray domains. The typical star forming galaxy with stellar mass ~10^{11}Mo at z=2 is an Ultra-luminous Infrared Galaxy (ULIRG), with L_IR ~ 1-2x10^{12}Lo and star formation rate SFR 200-300Mo/yr, implying a comoving density of ULIRGs at z=2 at least 3 orders of magnitude above the local one. SFRs derived from the reddening corrected UV luminosities agree well, on average, with the longer wavelength estimates. The high 24um detection rate suggests a relatively large duty cycle for the BzK star forming phase, consistently with the available independent measurements of the space density of passively evolving galaxies at z>1.4. If the IMF at z=2 is similar to the local one, and in particular is not a top-heavy IMF, this suggests that a substantial fraction of the high mass tail (>10^{11}Mo) of the galaxy stellar mass function was completed by z~1.4.