* Astronomy

Title: Highly Ionised Collimated Outflow from HE 0238 - 1904
Authors: Sowgat Muzahid (IUCAA), Raghunathan Srianand (IUCAA), Blair D. Savage (Wisconsin), Anand Narayanan (IIST), Vijay Mohan (IUCAA), Gulab C. Dewangan (IUCAA)

We present a detailed analysis of a highly ionised, multiphased and collimated outflowing gas detected through O V, O VI, Ne VIII and Mg X absorption associated with the QSO HE 0238 - 1904 (z_em ~ 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 photoionisation models can reproduce the observed N(Ne VIII), N(O VI) and N(Mg X) from a single phase whereas the low ionisation species (e.g. N III, N IV, O IV) originate from a different phase. The measured N(Ne VIII)/N(O VI) ratio is found to be remarkably similar (within a factor of ~ 2) in several individual absorption components kinematically spread over ~ 1800 km/s. Under photoionisation this requires a fine tuning between hydrogen density (nH) and the distance of the absorbing gas from the QSO. Alternatively this can also be explained by collisional ionisation in hot gas with T > 10^{5.7} K. Long-term stability favours the absorbing gas being located outside the broad line region (BLR). We speculate that the collimated flow of such a hot gas could possibly be triggered by the radio jet interaction.

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