An extreme metallicity, large-scale outflow from a star-forming galaxy at z ∼ 0.4.
MUZAHID S., KACPRZAK G.G., CHURCHILL C.W., CHARLTON J.C., NIELSEN N.M., MATHES N.L. and TRUJILLO-GOMEZ S.
Abstract (from CDS):
We present a detailed analysis of a large-scale galactic outflow in the circumgalactic medium of a massive (), star-forming (/yr), sub-L*() 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 () and the azimuthal angle () 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 ( 419 km/s) and ( 285 km/s) lines that are extremely rare in the literature. The highly ionized absorption components are well explained as arising in a low density (/cm3), diffuse (∼10 kpc), cool (∼104 K) photoionized gas with a super-solar metallicity (). From the observed narrowness of the Lyβ profile, the non-detection of absorption, and the presence of strong 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/cm3 and a metallicity of is possibly tracing recycled halo gas. We estimate an outflow mass of a mass-flow rate of a kinetic luminosity of erg/s, 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.