JWST Discovery of High-Velocity Mid-Infrared Ionized Outflows in Ultraluminous Infrared Galaxies F11119+3257 and F05189-2524

Ultra-fast outflows (UFOs) are thought to be a driving mechanism of large-scale winds driven by active galactic nuclei, which cause significant galactic feedback through quenching star formation and regulating supermassive black hole growth. We present James Webb Space Telescope (JWST) Mid-Infrared Instrument Medium-Resolution Spectrometer observations of two nearby ultraluminous infrared galaxies (ULIRGs), F11119+3257 and F05189-2524, with nuclear X-ray detected UFOs and kiloparsec-scale outflow. These galaxies show remarkably similar mid-infrared continuum and emission line features, notably including a high-velocity $v_{90}$ $\sim$ 4000 km s$^{-1}$ outflow detected in highly ionized neon emission lines, e.g., \nevi. In F05189-2524, we see a slightly slower biconical outflow extending up to $\sim2$ kpc in the same neon emission lines. Both sources show evidence of AGN-driven radiative feedback through a deficit of rotational molecular hydrogen lines in the nuclear region, $<$1 kpc from the central quasar, but no clear evidence of any molecular gas entrained in the quasar-driven outflow. Energetic analysis shows that the warm ionized gas in both of these sources contributes minimally ($\sim0.1-5%$) to the momentum outflow rate of these sources and leaves the conclusions of previous literature unchanged: the energetics of these sources are broadly consistent with a momentum-conserving outflow.

💡 Research Summary

This paper presents JWST Mid‑Infrared Instrument (MIRI) Medium‑Resolution Spectrometer (MRS) observations of two nearby ultra‑luminous infrared galaxies (ULIRGs), F11119+3257 (z≈0.19) and F05189‑2524 (z≈0.043), both of which host X‑ray detected ultra‑fast outflows (UFOs) and previously known kiloparsec‑scale winds in multiple gas phases. The authors processed the data with the latest JWST pipeline (v1.15.1) and CRDS (v12.0.2), applying a two‑step fringe mitigation strategy: spatial smoothing with a 1.5‑pixel radius circular average followed by the “fit residual fringes 1d” correction. After homogenising the point‑spread function to the H₂ S(1) 17.03 µm line (FWHM ≈ 1.46″ for F11119+3257 and 0.99″ for F05189‑2524) and stitching the four MIRI channels, they produced unified data cubes suitable for both 1‑D nuclear spectrum extraction and spatially resolved analysis.

For spectral fitting, the team employed the q3dfit adaptation of the QUEST‑fit framework, which simultaneously models PAH emission, silicate absorption, extinction, and black‑body continua. After continuum subtraction, emission lines were fitted with sums of Lorentzian profiles. The most striking result is the detection of extremely broad, blueshifted high‑ionisation neon lines—particularly