2007MNRAS.382L..11C

We report the detection of HI 21-cm absorption in the z = 0.96 early-type lensing galaxy towards MG J0414+0534 with the Green Bank Telescope. The absorption, with total N_HI= 1.6x10¹⁸ (T_s/f)/cm2, is resolved into two strong components, probably due to the two strongest lens components, which are separated by 0.4 arcsec. Unlike the other three lenses that have been detected in HI, J0414+0534 does not exhibit strong OH absorption, giving an OH/HI column density ratio of N_OH/N_HI ≲ 10^–6 (for T_s= 100 K, T_x= 10 K and f_HI= f_OH= 1). This underabundance of molecular gas may indicate that the extreme optical-near-infrared colour (V - K = 10.26) along the line of sight is not due to the lens. We therefore suggest that despite the strong upper limits on molecular absorption at the quasar redshift, as traced by millimetre lines, the extinction occurs primarily in the quasar host galaxy.