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Highly ionized collimated outflow from HE 0238–1904




We present a detailed analysis of a highly ionized, multiphased and collimated outflowing gas detected through O v, O vi, Ne viii and Mg x absorption associated with the QSO HE 0238–1904 (zem≃ 0.629). Based on the similarities in the absorption-line profiles and estimated covering fractions, we find that the O vi and Ne viii absorption trace the same phase of the absorbing gas. Simple photoionization models can reproduce the observed inline image, inline image and inline image from a single phase whereas the low-ionization species (e.g. N iii, N iv and O iv) originate from a different phase. The measured inline image ratio is found to be remarkably similar (within a factor of ∼2) in several individual absorption components kinematically spread over ∼1800 km s−1. Under photoionization this requires a fine-tuning between hydrogen density (nH) and the distance of the absorbing gas from the Quasi Stellar Object (QSO). Alternatively, this can also be explained by collisional ionization in hot gas with T≥ 105.7 K. Long-term stability favours the absorbing gas being located outside the broad-line region. We speculate that the collimated flow of such a hot gas could possibly be triggered by the radio jet interaction.