tokens: flattening in the values at lower column densities could be an effect of completeness. The nominal function (e.g., blue curve in Figure 9 ) is calculated for 3 σ detections. If this threshold is raised to 4 σ or even 5 σ , there is relatively less effective pathlength at lower column densities. The blue curve in the left-hand panels of Figures 9 , 11 , 12 representing moves to the right by ∼0.1 dex for each 1 σ increase in significance level and the frequency of weak absorbers rises. This results in a steepening of the weak-end slope of the cumulative distribution function (less pathlength for the same number of detections), but it does not eliminate the non-power-law nature of the distributions in any case. Therefore, we believe that the turnovers seen in many of the metal absorber distributions are real, but the weak-end slopes should be treated with caution. 4.2.5. Ne <sc>viii</sc> The extreme-UV (2 s – 2 p ) doublet transition of Ne viii (, f = 0.1030, 0.0505) is often presented as a less-ambiguous tracer of collisionally ionized gas than O vi or other highly ionized, FUV metal transitions (Savage et al. 2005 ). Several compelling studies of warm-hot or multiphase gas have been made using Ne viii in conjunction with H i , O vi , and other ions to constrain gas temperature and density (Savage et al. 2005 , 2011 ; Narayanan et al. 2009 , 2011 ; Tripp et al. 2011 ; Meiring et al. 2013 ; Hussain et al. 2015 ). Unfortunately, the Ne viii doublet only redshifts into the COS/G130M band at , which limits us to the 13 highest-redshift AGN sight lines in this survey, usually without observations of the strong H i counterparts. We measure several dozen Ne viii systems, but all are at redshifts similar to the background AGNs and show the hallmarks of intrinsic, rather than intervening, absorption. They are primarily strong, blended, multi-component absorption profiles in high ions, often lacking H i absorption. There are three Ne viii detections at >3 σ in our survey that can be reasonably identified as intergalactic rather than intrinsic systems. The system detected toward PKS 0405−123 at z = 0.49494 in Ne viii and O vi by Narayanan et al. ( 2011 ) shows and . In an earlier reduction of the data allowing for the contaminating effects of fixed pattern noise, Narayanan et al. ( 2011 ) measured column densities of and . The origin of the Ne viii and O vi is consistent with collisionally ionized gas with T ≈ 5 × 10 5 K and a baryonic column density of cm −2 . Two other Ne viii detections have no corresponding absorption in any other metal or H i transition. The first is a pair of broad absorption features toward PKS 0637−752 consistent with Ne viii doublet absorption at z = 0.60552 with . Ly β and O vi λ 1032 non-detections place column density upper limits of and , respectively. A similar pair of weak absorption features in the HE 0238−1904 sight line is consistent with a z = 0.50511 Ne viii doublet: , , and . These two Ne viii -only systems provide
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