An extreme metallicity, large-scale outflow from a star-forming galaxy at z ~ 0.4

We present a detailed analysis of a large-scale galactic outflow in the circumgalactic medium of a massive (Mh 10 M ~ 12.5 ), star-forming (~6.9 M yr−1), sub-L* ( 0.5LB~ *) galaxy at z = 0.39853 that exhibits a wealth of metal-line absorption in the spectra of the background quasar Q 0122−003 at an impact parameter of 163 kpc. The galaxy inclination angle (i = 63) and the azimuthal angle (F = 73) imply that the QSO sightline is passing through the projected minor-axis of the galaxy. The absorption system shows a multiphase, multicomponent structure with ultra-strong, wide velocity spread O VI (log N = 15.16  0.04, Dv90 = 419 km s−1) and N V (log N = 14.69  0.07, Dv90 = 285 km s−1) lines that are extremely rare in the literature. The highly ionized absorption components are well explained as arising in a low density (~10-4.2 cm−3), diffuse (∼10 kpc), cool (∼104 K) photoionized gas with a super-solar metallicity ([X H]  0.3). From the observed narrowness of the Lyβ profile, the non-detection of S IV absorption, and the presence of strong C IV absorption in the low-resolution FOS spectrum, we rule out equilibrium/non-equilibrium collisional ionization models. The low-ionization photoionized gas with a density of ~10-2.5 cm−3 and a metallicity of [X H]  -1.4 is possibly tracing recycled halo gas. We estimate an outflow mass of~2 ´ 1010 M, a mass-flow rate of~54 M yr-1,  a kinetic luminosity of ~9 ´ 1041 erg s−1, and a mass loading factor of ∼8 for the outflowing high-ionization gas. These are consistent with the properties of “down-the-barrel” outflows from infrared-luminous starbursts as studied by Rupke et al. Such powerful, large-scale, metal-rich outflows are the primary means of sufficient mechanical and chemical feedback as invoked in theoretical models of galaxy formation and evolution