Evidence for Late-time Feedback from the Discovery of Multiphase Gas in a Massive Elliptical at z = 0.4

Abstract

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 ( ) elliptical lens galaxy at . 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 H 2 in the lens ISM at projected distance d  = 4.6 kpc. The H 2 column density is with a molecular gas fraction of , 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 ) and log N (N v ) , among the highest known in external galaxies. Assuming the high-ionization absorption features originate in a transient warm ( T ∼ 10 5 K) phase undergoing radiative cooling from a hot halo surrounding the galaxy, we infer a mass accretion rate of . 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 . 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.