The GOLIATH Survey: OVI Absorption Reveals CGM Evolution through the Starburst-to-Quiescent Transition in Massive Galaxies

We present the GOLIATH survey (Galaxies, Outflows, and the Lifecycle of Immense, Active, Transforming Halos), a study of the multiphase circumgalactic medium (CGM) of massive (M/M about 11), blue (u-r < 1.65) starburst and post-starburst galaxies at z about 0.43. This work characterizes the warm-hot CGM through OVI absorption in the inner halo (R/R vir at most 0.6) of these rare systems. Across the star-forming population, OVI column density rises by nearly 1 dex from M/M about 8 to about 11.5 and increases with specific star-formation rate (sSFR). Two GOLIATH galaxies with the highest sSFR show the strongest CGM OVI absorption (N O,VI[cm-2] 15). In the M/M = [11,12) inner-CGM region, massive star-forming galaxies exceed quiescent galaxies on average by a factor of about 3 in OVI column density and about 1.5 dex in CGM OVI mass ((M O, VI/M) about 7.3 versus about 5.8), with covering fractions roughly three times higher (62.5% versus 24% at N O,VI[cm-2] at least 14). The OVI line widths and column densities are consistent with feedback-driven radiative cooling, in which outflow shocks heat the CGM and the gas cools back through the OVI window; the short cooling time, t cool about 10 - 100 Myr, requires continuous replenishment by active feedback to sustain this reservoir. The residual OVI in quiescent systems may arise from ambient gas at the high-temperature end of the cooling curve. OVI thus traces feedback on short timescales and probes the star-forming--quiescent transition at M/M 11.