Molecular Gas Excitation in z ∼ 0.7 Gas-rich Poststarburst Galaxies from SQuIGG(Formula presented) L→[jls-end-space/]E

Many poststarburst galaxies at z ∼ 0.7 have been shown to retain substantial molecular gas reservoirs yet host low ongoing star formation, suggesting that the remaining gas may be inefficient at forming stars during the early postburst phase. We present new Atacama Large Millimeter/submillimeter Array CO(5–4) observations of nine gas-rich poststarburst galaxies at z ∼ 0.7 from the Studying Quenching in Intermediate-z Galaxies: Gas, angu (Formula presented) L→ ar momentum, and Evolution (SQuIGG (Formula presented) L→ E) survey, providing a view of the molecular gas excitation in these systems. Combined with existing CO(2–1) data, we detect CO(5–4) in eight out of nine targets and find that most have moderate CO excitation with (Formula presented) r52≡LCO(5−4)′/LCO(2−1)′≈0.1−0.3. These systems show no clear trend between r₅₂ and either total or surface-density of star formation. Specifically, all objects have Σ_SFR ∼ 0.01–1 M_⊙ yr⁻¹ kpc⁻², consistent with compact, modest star formation, even when allowing for buried activity, as these galaxies decline from their peak. One object, J1448+1010, which has clear optical, mid-infrared, and radio indicators of an active galactic nucleus, is an outlier with r₅₂ ≈ 0.6; its elevated excitation likely requires significant nonstellar heating, with a contribution from potentially obscured star formation. Together, most gas-rich SQuIGG (Formula presented) L→ E poststarbursts have moderately excited molecular gas alongside little to modest star-forming activity, indicating that the remaining gas hosts relatively suppressed star formation efficiencies instead of strong buried starburst activity.