Stern D, Eisenhardt P, Spinrad H, Dawson S, van Breugel W, Dey A, de Vries W, Stanford S A
Jet Propulsion Laboratory, California Institute of Technology, Pasadena 91109, USA.
Nature. 2000 Nov 30;408(6812):560-2. doi: 10.1038/35046027.
The identification of galaxies at extreme distances provides the most direct information about the earliest phases of galaxy formation. But at redshifts z > 5 even the most luminous galaxies appear faint; the interpretation of low signal-to-noise ratio data is difficult and misidentifications do occur. Here we report optical and near-infrared observations of the source STIS123627+621755, which was previously suggested to be at a redshift of 6.68 (ref. 1). At that redshift, and with the reported spectral energy distribution, the galaxy should be essentially invisible at wavelengths less than 9,300 A, because the intervening intergalactic medium absorbs almost all light energetic enough to ionize neutral hydrogen--that is, with wavelengths less than the redshifted Lyman limit of lambda = (1 + z) x 912A. At near-infrared wavelengths, however, the galaxy should be relatively bright. Here we report a detection of the galaxy at 6,700 A and a non-detection at a wavelength of 1.2 microm, contrary to expectations for z approximately 6.68. The data conservatively require that STIS123627+621755 has a redshift z < 6.
对极远距离星系的识别提供了有关星系形成最早阶段的最直接信息。但在红移z > 5时，即使是最亮的星系看起来也很暗淡；低信噪比数据的解释很困难，而且确实会出现误识别。在此，我们报告了对源STIS123627+621755的光学和近红外观测，该源此前被认为红移为6.68（参考文献1）。在该红移下，根据报告的光谱能量分布，该星系在波长小于9300埃时应该基本上不可见，因为中间的星系际介质几乎吸收了所有能量足以使中性氢电离的光——即波长小于红移后的莱曼极限λ = (1 + z)×912埃的光。然而，在近红外波长下，该星系应该相对明亮。在此我们报告在6700埃处检测到该星系，而在1.2微米波长处未检测到，这与z约为6.68的预期相反。这些数据保守地要求STIS123627+621755的红移z < 6。
