2017MNRAS.471..792P

We report on the detection of two Ne VIII absorbers, at z = 0.619 07 and 0.570 52 in the Hubble Space Telescope/Cosmic Origins Spectrograph spectrum of background quasars SDSS J080908.13 + 461925.6 and SBS 1122 + 594, respectively. The Ne VIII 770 line is at ∼3σ significance. In both instances, the Ne VIII is found to be tracing gas with T >= 10⁵ K, predominantly collisionally ionized, with moderate densities of n_ H_ 10^–4 cm^–3, sub-solar metallicities and total hydrogen column densities of N(H) >= 10¹⁹ cm^–2. In the z = 0.619 07 absorber, the low, intermediate ions and O VI are consistent with origin in photoionized gas, with the O VI potentially having some contribution from the warm collisional phase traced by Ne VIII. The z = 0.570 52 system has H I absorption in at least three kinematically distinct components, with one of them having b( H  I) = 49  ±  11 km s^–1. The intermediate-ionization lines, O VI and Ne VIII, are coincident in velocity with this component. Their different line widths suggest warm temperatures of T = (0.5-1.5) x 10⁵ K. Both absorbers are residing in regions where there are several luminous (>=L) galaxies. The absorber at z = 0.570 52 is within the virial radius of a 2.6L galaxy, possibly associated with shock-heated circumgalactic material.