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 ( M h ∼ 10 12.5 M ⊙ ?> ), star-forming ( ∼ 6.9 M ⊙ ?> yr−1), sub-L* ( ∼ 0.5 L B * ?> ) 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 ( Φ = 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 , ?> Δ v 90 = ?> 419 km s−1) and N V ?> ( log N = 14.69 ± 0.07 , ?> Δ v 90 = ?> 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 × 10 10 M ⊙ , ?> a mass-flow rate of ∼ 54 M ⊙ yr − 1 , ?> a kinetic luminosity of ∼ 9 × 10 41 ?> 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.