We explore the dependence of the radial alignment of subhaloes on the mass of the host halo they orbit in. As the effect is seen on a broad range of scales including massive clusters as well as galactic systems it only appears natural to explore this phenomenon by means of cosmological simulations covering the same range in masses. We have 25 well resolved host dark matter haloes at our disposal ranging from 1015 h−1 M⊙ down to 1012 h−1 M⊙ each consisting of order of a couple of million particles within the virial radius. We observe that subhaloes tend to be more spherical than isolated objects. Both the distributions of sphericity and triaxiality of subhaloes are Gaussian‐distributed with peak values of 〈s〉≈ 0.80 and 〈T〉≈ 0.56, irrespective of host mass. Interestingly, we note that the radial alignment is independent of host halo mass and the distribution of cos θ (i.e. the angle between the major‐axis Ea of each subhalo and the radius vector of the subhalo in the reference frame of the host) is well fitted by a simple power law P(cos θ) ∝ cos4θ with the same fitting parameters for all host haloes.

To explore the ionization conditions in highly-ionized absorbers at high redshift we have studied in detail two intervening O vi absorbers at z ≈ 2 towards the quasar PKS 1448−232, based on high (R ≈ 75, 000) and intermediate (R ≈ 45, 000) resolution optical VLT/UVES spectra. We find that both absorption systems are composed of several narrow subcomponents with C iv/O vi Doppler-parameters b < 10 km s −1 , typically. This implies that the gas temperatures are T < 10 5 K and that the absorbers are photoionized by the UV background. The system at z = 2.1098 represents a simple, isolated O vi absorber that has only two absorption components and that is relatively metal-rich (Z ∼ 0.6 solar). Ioinization modeling implies that the system is photoionized with O vi, C iv, and H i coexisting in the same gas phase. The second system at z = 2.1660 represents a complicated, multi-component absorption system with eight O vi components spanning almost 300 km s −1 in radial velocity. The photoionization modeling implies that the metallicity is non-uniform and relatively low (≤ 0.1 solar) and that the O vi absorption must arise in a gas phase different from that traced by C iv, C iii, and H i. Our detailed study of the two O vi systems towards PKS 1448−232 shows that multi-phase, multi-component high-ion absorbers like the one at z = 2.1660 require a detailed ionization modeling of the various subcomponents to obtain reliable results on the physical conditions and metal-abundances in the gas.

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