Diverse young stellar populations in the intermediate-redshift radio galaxies 3C 213.1 and 3C 459: implications for the evolution of the host galaxies
Diverse young stellar populations in the intermediate-redshift radio galaxies 3C 213.1 and 3C 459: implications for the evolution of the host galaxies
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中红移射电星系 3C 213.1 和 3C 459 中多样化的年轻恒星群：对宿主星系演化的影响
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发表时间：
2008
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通讯作者：
R. Morganti
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作者：
K. Wills;C. Tadhunter;J. Holt;R. Delgado;K. Inskip;J. Zaurin;R. Morganti
我们目前的欧洲南方天文台甚大望远镜（ESO VLT）和威廉赫歇尔望远镜（WHT）光谱观测两个强大的射电星系在中等红移（3C 213.1和3C 459），获得的目的是建立的性质和演化状态的主机星系。光谱合成模型已被用来证明，年轻的恒星种群（YSP）作出了重大贡献的综合光学在这两个来源，贡献至少37%和80%的综合B波段光在3C 213.1和3C 459，分别。3C 213.1的YSP年龄介于0.4-0.8 Gyr之间，占恒星总质量的3%-30%，而3C 459的光谱则需要年轻（<0.1 Gyr）和中等（0.2-1.2 Gyr）年龄的YSP成分的组合，它们共同占恒星总质量的5%-100%。3C 459的光学和远红外特性都与其作为超亮红外星系（ULIRG）的地位相一致，并且在一个主要的富含气体的合并中，观测到的射电源在接近星星形成活动的峰值时被触发。另一方面，在3C 213.1中，射电源很可能在星暴峰值之后的一段时间内被触发（或重新触发），并且源的远红外光度相当低。在修正了YSP的贡献后，两个源的宿主星系的绝对星等都相对适中（≤2L*），从而表明强大的射电活动并不总是与最大质量和最明亮的椭圆星系有关。这些结果有助于强调，射电源人口是多样化的，无论是在宿主星系的属性和触发机制（S）的射电源活动。
We present European Southern Observatory Very Large Telescope (ESO VLT) and William Herschel Telescope (WHT) spectroscopic observations of two powerful radio galaxies at intermediate redshifts (3C 213.1 and 3C 459), obtained with the aim of establishing the nature and evolutionary status of the host galaxies. Spectral synthesis modelling has been used to demonstrate that young stellar populations (YSP) make a major contribution to the integrated optical light in both sources, contributing at least 37 and 80 per cent of the integrated B-band light in 3C 213.1 and 3C 459, respectively. While in the case of 3C 213.1 the YSP has an intermediate age (0.4–0.8 Gyr) and comprises 3–30 per cent of the total stellar mass, adequate fits to the spectra of 3C 459 require a combination of younger (<0.1 Gyr) and intermediate (0.2–1.2 Gyr) age YSP components that together comprise 5–100 per cent of the total stellar mass. Both the optical and far-IR properties of 3C 459 are consistent with its status as an ultraluminous infrared galaxy (ULIRG), and a scenario in which the observed radio source has been triggered close to the peak of star formation activity in a major gas-rich merger. On the other hand, in 3C 213.1 it is likely that the radio source has been triggered (or re-triggered) a significant period after the starburst peak, and the far-IR luminosity of the source is substantially lower. Following correction for the contributions of the YSP, the absolute magnitudes of the host galaxies of both sources are relatively modest (≤2L*), thus demonstrating that powerful radio activity is not always associated with the most massive and luminous elliptical galaxies. These results serve to emphasize that the radio source population is diverse, in terms of both the host galaxy properties and the triggering mechanism(s) for the radio source activity.