A Gravitational Lens Solution for the [ITAL]IRAS[/ITAL] Galaxy FSC 10214+4724

Abstract

We show that the z = 2.3 IRAS source FSC 10214+4724 is gravitationally lensed by an intervening elliptical galaxy. Its many anomalous properties can be explained if the active galactic nucleus (AGN) region of the source is much more magnified than its outer regions. We uncover a small counterimage to the arc adjacent to the lensing galaxy, as predicted by our lens model. A redshift of unity for the lens is suggested by a red component in the observed spectrum, yielding a lensing mass interior to the critical radius of M(r < 3 kpc) ≈ 10¹¹ M_☉, consistent with an ordinary massive galaxy. We present new high-resolution optical images which show a thin arc of emission, implying that the optical source is compact (less than 0.5 kpc) and highly magnified (more than 20 times). Since the optical emission is known to be strongly polarized and Seyfert 2, we propose that the optical arc is a highly magnified image of the inner "mirror" region of an obscured AGN. The central obscuring "torus" will be similarly magnified, naturally accounting for the large IR flux. We propose that cases like F10214 represent the obscured AGN counterparts to the lensed QSO population, and find that the probability of finding objects like F10214 in IRAS redshift surveys is reasonably large.