Detection of OH and wide HI absorption toward B 0218 + 357

We present deep GMRT OH and WSRT HI absorption spectra of the z = 0.6846 gravitational lens toward B0218+357. Both the 1665 MHz and 1667 MHz OH lines are clearly detected for the first time while a new wide absorption component was detected (at low significance) in the HI spectrum; the OH spectra yielded an OH column density of NOH = 2.3 × 10 cm−2. The ratio of 1667 and 1665 MHz equivalent widths is ∼ 1.8 while the redshift of peak OH absorption is z = 0.68468± 0.000008 for both lines; this redshift agrees with that obtained from the HI line. The velocity spread (between nulls) of the HI absorption is ∼ 140 km s−1, while that of both OH lines is ∼ 100 km s−1; the HI and OH spectra are broadly similar in that they each have two principal narrow components and a wide absorption trough. We argue that the wide absorption is likely to arise from source components in the Einstein ring and derive a rotation velocity of ∼ 150 km s−1 at a distance of 1.5 kpc from the centre of the z ∼ 0.6846 galaxy.