AN EXTREME METALLICITY, LARGE-SCALE OUTFLOW from A STAR-FORMING GALAXY at z ∼ 0.4

Sowgat Muzahid, Glenn G. Kacprzak, Christopher W. Churchill, Jane C. Charlton, Nikole M. Nielsen, Nigel L. Mathes, Sebastian Trujillo-Gomez

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Abstract

We present a detailed analysis of a large-scale galactic outflow in the circumgalactic medium of a massive (Mh 10 M ∼12.5 M⊙), 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 (Φ = 73�) imply that the QSO sightline is passing through the projected minor-axis of the galaxy. The absorption system shows a multiphase, ulticomponent structure with ultra-strong, wide velocity spread O VI (log N = 15.16�0.04, Δv90 = 419 km s-1) and N V (log N = 14.69�0.07, Δv90 = 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 ∼2x1010M⊙a mass-flow rate of ∼54 M⊙ yr-1, a kinetic luminosity of ∼9x1041 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.

Original languageEnglish (US)
Article number132
JournalAstrophysical Journal
Volume811
Issue number2
DOIs
StatePublished - Oct 1 2015

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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