A SPECTROSCOPIC STUDY OF IRAS F10214+4724

The z = 2.286 IRAS galaxy F10214 + 4724 remains one of the most lumino us galaxies in the Universe, despite its gravitational lens magnificat ion. We present optical and near-infrared spectra of F10214 + 4724, wi th clear evidence for three distinct components: lines of width simila r to 1000 km s(-1) from a Seyfert 2 nucleus; less than or similar to 2 00 km s(-1) lines which are likely to be associated with star formatio n; and a broad (similar to 4000 km s(-1)) C III] 1909-Angstrom emissio n line which is blueshifted by similar to 1000 km s(-1) with respect t o the Seyfert 2 lines. Our study of the Seyfert 2 component leads to s everal new results. (i) From the double-peaked structure in the Ly alp ha line, and the lack of Ly beta, we argue that the Ly alpha photons h ave emerged through a neutral column of N-H similar to 2.5 x 10(25) m( -2), possibly located within the AGN narrow-line region, as proposed f or several high-redshift radio galaxies. (ii) The resonant O VI 1032, 1036-Angstrom doubler (previously identified as Ly beta) is in an opti cally thick (1:1) ratio. At face value this implies an extreme density (n(e) similar to 10(17) m(-3)) more typical of broad-line region clou ds. However, we attribute this instead to the damping wings of Ly beta from the resonant absorption, (iii) A tentative detection of He II 10 86 suggests little extinction in the rest frame ultraviolet.