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Paper: HI and OH Absorption towards 1830-211
Volume: 156, Highly Redshifted Radio Lines
Page: 228
Authors: Chengalur, J. N.; de Bruyn, A. G.; Narasimha, D.
Abstract: We report on WSRT observations of HI and OH absorption at a redshift of z = 0.885 toward the radio lens PKS 1830-21. The mm wave transitions of several molecular species have already been observed in absorption toward PKS 1830-21 at this redshift. At mm wavelengths the source structure consists of two extremely compact components, the northeast (NE) and southwest (SW) components. At lower frequencies in addition to these two components there is also a broad Einstein ring connecting the NE and SW components. The HI spectrum we obtain is asymmetric, with a peak at -147 km/s wrt to z = 0.88582 and a total velocity width ~300 km/s. In OH we detect both the 1667 and the 1665 MHz transitions, and the ratio of their optical depths is not consistent with what is expected in thermal equilibrium. The OH spectrum has a velocity width comparable to that of the HI spectrum, suggesting that it is wide spread in the absorber. This coupled with the lack of a strong HI peak in the spectrum at the velocity corresponding to the SW component, suggests that the galaxy responsible for the absorption at z = 0.885 has a central molecular disk a few kpc in size, and that HI is deficient in this central region.
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