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

Abstract

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 ($⟨\log M_{\star }/M_{\odot }⟩\approx 11$), blue ($u-r<1.65$) starburst and post-starburst galaxies at $⟨z⟩\approx$ 0.43. This work characterizes the warm-hot CGM through OVI absorption in the inner halo ($R/R_{\mathrm{vir}}\le 0.6$) of these rare systems. Across the star-forming population, OVI column density rises by nearly 1~dex from $\log M_{\star }/M_{\odot }\sim 8$ to $\sim 11.5$ and increases with specific star-formation rate (sSFR). Two GOLIATH galaxies with the highest sSFR show the strongest CGM OVI absorption ($\log N_{\mathrm{O}\mathrm{VI}}[\mathrm{c}{\mathrm{m}}^{-2}]\gtrsim 15$). In the $\log M_{\star }/M_{\odot }=[11,12)$ inner-CGM region, massive star-forming galaxies exceed quiescent galaxies on average by a factor of $\sim 3$ in OVI column density and $\sim 1.5$~dex in CGM OVI mass ($\log (M_{\mathrm{O}\mathrm{VI}}/M_{\odot })\approx 7.3$ versus $\approx 5.8$), with covering fractions roughly three times higher (62.5% versus 24% at $\log N_{\mathrm{O}\mathrm{VI}}[\mathrm{c}{\mathrm{m}}^{-2}]\ge 14$). 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, $t_{\mathrm{cool}}\sim 10$-$100$~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 $\log M_{\star }/M_{\odot }\gtrsim 11$.

29 pages, 10 Figures, 3 tables, Submitted to ApJ