标题： CO发射在低红移和高红移射电星系中 显示英文标题

标题： CO Emission in Radio Galaxies at Low and High Redshift

摘要： CO观测结果展示了0<z<4的射电星系。 对于高红移强大射电星系（HzPRGs：z > 1，P_408MHz > 10^27 瓦特/赫兹）的L_CO上限与分子气体（H_2）质量随红移和/或射电功率没有演化的结果一致。 对于低红移强大射电星系（LzPRGs：z<0.2，P_408MHz MHz > 10^23.5 W/Hz）的观测显示，只有一F-R II星系在CO中被检测到，而大约50%的射电紧凑（FC）和F-R I星系已被检测到。 迄今为止的CO和成像数据表明，F-R II星系可能是相对于FC/F-R I星系的气体贫乏星系合并的结果，或者某些FC/F-R I星系演化为F-R II星系。 在任何一种情况下，强大射电星系中的射电活动很可能是由合并事件触发的，H_2可能是在合并早期阶段活动星系核（AGN）的燃料。 显示英文摘要

摘要： CO observations of 0<z<4 radio galaxies are presented. The L_CO upper limits for the high-redshift powerful radio galaxies (HzPRGs: z > 1, P_408MHz > 10^27 Watts/Hz) are consistent with no evolution in molecular gas (H_2) mass with redshift and/or radio power. Of the low-redshift powerful radio galaxies (LzPRGs: z<0.2, P_408MHz MHz > 10^23.5 W/Hz) observed, only one F-R II galaxy has been detected in CO, whereas approximately 50% of the radio-compact (FC) and F-R I galaxies have been detected. The CO and imaging data to date imply that either F-R II galaxies result from mergers of gas-poor galaxies relative to FC/F-R I galaxies, or that some FC/F-R I galaxies evolve into F-R II galaxies. In either scenario, the radio activity in powerful radio galaxies is most likely triggered by a merger event, and H_2 may be the fuel for the active galactic nucleus (AGN) in the early stages of the merger.