2020ApJ...904L..10Z

We report the first detection of multiphase gas within a quiescent galaxy beyond z ≃ 0. The observations use the brighter image of doubly lensed QSO HE 0047-1756 to probe the interstellar medium (ISM) of the massive (M_star~10¹¹M_☉) elliptical lens galaxy at z_gal=0.408. Using Hubble Space Telescope's Cosmic Origins Spectrograph (COS), we obtain a medium-resolution FUV spectrum of the lensed QSO and identify numerous absorption features from H₂ in the lens ISM at projected distance d = 4.6 kpc. The H₂ column density is logN(H₂)/cm^–2=17.8_–0.3^+0.1 with a molecular gas fraction of f_H2_=2 % –5 % , roughly consistent with some local quiescent galaxies. The new COS spectrum also reveals kinematically complex absorption features from highly ionized species O VI and N V with column densities log N(O VI)/cm^–2=15.2±0.1 and log N(N V)/cm^–2=14.6±0.1, among the highest known in external galaxies. Assuming the high-ionization absorption features originate in a transient warm (T ∼ 10⁵ K) phase undergoing radiative cooling from a hot halo surrounding the galaxy, we infer a mass accretion rate of ∼0.5–1.5M_☉yr^–1. The lack of star formation in the lens suggests that the bulk of this flow is returned to the hot halo, implying a heating rate of ∼10⁴⁸ergyr^–1. Continuous heating from evolved stellar populations (primarily SNe Ia but also winds from AGB stars) may suffice to prevent a large accumulation of cold gas in the ISM, even in the absence of strong feedback from an active nucleus.