A spectroscopic study of IRAS F10214 + 4724

Serjeant, Stephen; Rawlings, Steve; Lacy, Mark; McMahon, Richard G.; Lawrence, Andy; Rowan-Robinson, Michael and Mountain, Matt (1998). A spectroscopic study of IRAS F10214 + 4724. Monthly Notices of the Royal Astronomical Society, 298(2) pp. 321–331.

DOI: https://doi.org/10.1046/j.1365-8711.1998.01522.x

URL: http://dx.doi.org/10.1046/j.1365-8711.1998.01522.x

Abstract

The z = 2.286 IRAS galaxy F10214 + 4724 remains one of the most luminous galaxies in the Universe, despite its gravitational lens magnification. We present optical and near-infrared spectra of F10214 + 4724, with clear evidence for three distinct components: lines of width ∼ 1000 km s⁻¹ from a Seyfert 2 nucleus; ≲ 200 km s⁻¹ lines which are likely to be associated with star formation; and a broad (∼ 4000 km s⁻¹) C iii] 1909-Å emission line which is blueshifted by ∼ 1000 km s⁻¹ with respect to the Seyfert 2 lines. Our study of the Seyfert 2 component leads to several new results. (i) From the double-peaked structure in the Lya line, and the lack of Lyβ, we argue that the Lya photons have emerged through a neutral column of NH ∼ 2.5 × 10²⁵ m⁻², possibly located within the AGN narrow-line region, as proposed for several high-redshift radio galaxies. (ii) The resonant O vi 1032, 1036-Å doublet (previously identified as Lyβ) is in an optically thick (1:1) ratio. At face value this implies an extreme density (n_e ∼ 10¹⁷ m⁻³) more typical of broad-line region clouds. However, we attribute this instead to the damping wings of Lyβ from the resonant absorption. (iii) A tentative detection of He ii 1086 suggests little extinction in the rest frame ultraviolet.

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