标题： 高红移射电星系的形态演化与巨型椭圆星系的形成 显示英文标题

标题： Morphological Evolution in High Redshift Radio Galaxies and the Formation of Giant Elliptical Galaxies

摘要： 我们展示了用凯克I望远镜的NIRC（近红外摄像仪）获得的高红移射电星系的深度近红外图像。在大多数情况下，近红外数据采样的波长位于~4000埃附近，不受强发射线的影响。在z > 3的情况下，静止帧光学形态通常具有围绕多个大小约为10千秒差距组件的微弱、大规模辐射。小结点中最亮的部分常常与射电结构对齐。在z < 3的情况下，形态发生显著变化，显示出单一、紧凑的结构，没有与射电对齐的特征。z > 3射电星系中的单个组件的大小和光度与通过Lyman dropout技术在z ~ 3发现的射电安静恒星形成星系相似。z > 3射电星系的静止帧光学颜色与最近的恒星形成主导观测到的红外光的模型一致，并且在一个案例（4C 41.17）中，我们有直接光谱证据证明了大规模恒星形成（Dey等人，1997a）。我们的结果表明，z > 3的射电星系在2 < z < 3时演化为非常巨大的椭圆星系，这在定性上与星系形成的等级模型是一致的。我们还讨论了射电星系的哈勃图、K-z关系中的射电功率依赖的可能性以及射电星系形成的含义。 显示英文摘要

摘要： We present deep near-IR images of high redshift radio galaxies obtained with NIRC on the Keck I telescope. In most cases, the near-IR data sample rest wavelengths at ~4000 Angstroms, free of strong emission lines. At z > 3, the rest frame optical morphologies generally have faint, large-scale emission surrounding multiple components of ~10 kpc size. The brightest of the small knots are often aligned with the radio structures. At z < 3, the morphologies change dramatically, showing single, compact structures without radio-aligned features. The sizes and luminosities of the individual components in the z > 3 radio galaxies are similar to those of the radio-quiet star-forming galaxies discovered at z ~ 3 by the Lyman dropout technique. The rest frame optical colors of the z > 3 radio galaxies are consistent with models in which recent star formation dominates the observed IR light, and in one case (4C 41.17) we have direct spectroscopic evidence for massive star formation (Dey et al. 1997a). Our results suggest that the z > 3 radio galaxies evolve into very massive elliptical galaxies at 2 < z < 3, in qualitative agreement with the hierarchical model of galaxy formation. We also discuss the Hubble diagram of radio galaxies, the possibility of a radio power dependence in the K-z relation, and the implications for radio galaxy formation.