Highly Ionized Collimated Outflow from HE 0238 - 1904

TL;DR

This paper analyzes a highly ionized, collimated outflow from QSO HE 0238 - 1904, revealing multiple ionization phases, potential origins, and the possibility of jet-induced collimation, with implications for quasar feedback mechanisms.

Contribution

It provides a detailed multi-phase analysis of the outflow, proposing that the observed ionization states can be explained by either photoionization or collisional ionization, and suggests jet interaction as a collimation mechanism.

Findings

O VI and Ne VIII trace the same gas phase.

Observed ion ratios are consistent with either photoionization or collisional ionization.

The outflow is located outside the broad line region, possibly influenced by radio jets.

Abstract

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 (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 photoionization models can reproduce the observed N(Ne VIII), N(O VI) and N(Mg X) from a single phase whereas the low ionization 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 photoionization 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 ionization in hot gas with T > 10^{5.7} K. Long-term stability favors 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.