Open AccessA spectroscopic study of IRAS F10214 + 4724
Author(s) -
Serjeant Stephen,
Rawlings Steve,
Lacy Mark,
McMahon Richard G.,
Lawrence Andy,
RowanRobinson Michael,
Mountain Matt
Publication year - 1998
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1998.01522.x
Subject(s) - physics , astrophysics , galaxy , redshift , gravitational lens , astronomy , line (geometry) , extinction (optical mineralogy) , emission spectrum , luminous infrared galaxy , star formation , spectral line , optics , geometry , mathematics
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 Lyα line, and the lack of Lyβ, we argue that the Lyα photons have emerged through a neutral column of N H ∼ 2.5 × 10 25 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 ∼ 10 17 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.