Resolving the Multiphase Outflow, Shock Signatures, and PAHs in the AGN-Starburst Composite ULIRG F10565+2448 with JWST MIRI/MRS

Kylie Yui Dan, Jerome Seebeck, Sylvain Veilleux, David Rupke, Eduardo Gonzalez-Alfonso, Ismael Garcia-Bernete, Weizhe Liu, Dieter Lutz, Marcio Melendez, Miguel Pereira Santaella, Eckhard Sturm, Francesco Tombesi

First listed 2026-05-04 | Last updated 2026-05-04

Abstract

We present new James Webb Space Telescope Mid-Infrared Instrument (MIRI) Medium-Resolution Spectrometer (MRS) observations of the nearby ultra-luminous infrared galaxy F10565+2448. These integral field spectroscopic data reveal an unresolved nuclear outflow in both warm-ionized and warm-molecular gas phases as well as a resolved blueshifted kpc-scale warm-molecular outflow. The unresolved warm-ionized outflow has a mean projected velocity up to $-520$ km/s, while the unresolved warm-molecular outflow is slower at $-150$ km/s. For the resolved warm-molecular outflow, the projected mean velocity ($-280 < v_{50} < -110$ km/s) is only slightly faster than the velocity of the disk ($-70 < v_{50} < 120$ km/s) and as such likely does not exceed the estimated escape velocity of $\gtrsim 300$ km/s. The warm-molecular outflow is slightly hotter ($507 \pm 25$K) than the disk ($329 \pm 5$K), and displays areas of higher temperature and lower column density that may indicate a shock front, which we explore using the [Fe II] 5.34 $μ$m/Pf$α$ shock diagnostic. Analysis of the polycyclic aromatic hydrocarbon features reveal trends of ionization and grain size that first decrease with radius up to 1 kpc before increasing up to 3 kpc. These results bolster the picture of F10565+2448 being an AGN-starburst composite where both star formation and AGN-powered phenomena are required to explain the outflow energetics.

Short digest

JWST/MIRI MRS integral-field spectroscopy of the nearby ULIRG F10565+2448 isolates an unresolved nuclear outflow and a resolved kpc-scale warm-molecular outflow, allowing the authors to compare warm ionized gas, warm H2, and PAH-emitting material within the same merger-driven system. The nucleus shows a faster warm-ionized outflow with projected mean velocity up to -520 km/s, while the unresolved warm-molecular component is slower at -150 km/s; the resolved warm-molecular flow spans -280 to -110 km/s and is slightly hotter than the disk at 507 +/- 25 K versus 329 +/- 5 K. The spatially resolved H2 component also contains hotter, lower-column regions suggestive of a shock front, explored with the [Fe II] 5.34 um/Pf alpha diagnostic, while PAH ratios show a radial drop and then recovery in ionization and grain size from the center to 3 kpc. Altogether, the paper sharpens the case that F10565+2448 is a true AGN-starburst composite, with both black-hole and star-formation power needed to explain the outflow energetics, even though the warm-molecular phase likely does not escape the galaxy.

Key figures to inspect

• Figure 1 is worth checking first because the paper's kinematic claims depend on aggressive post-processing: it shows how the team combined pipeline 2D defringing with an extra spaxel-by-spaxel residual-fringe correction to recover cleaner MIRI/MRS line profiles across all four channels.
• Figure 2 gives the nuclear spectral decomposition that underpins the rest of the analysis; inspect how the cool, warm, and hot dust continua, PAH templates, emission lines, and the 6.1 um water-ice absorption are separated, since that tells you how robust the derived PAH and line measurements are in this dusty ULIRG n…
• Figure 3 appears to be the key nuclear outflow diagnostic: the trends of line velocity and width against ionization potential and critical density show whether the faster broad components are preferentially associated with higher-ionization gas, helping distinguish a compact AGN-driven ionized outflow from the broader…
• Figure 4 is the cleanest line-profile evidence for the nuclear ionized outflow. Compare [Ne II], [Ne III], and [Ne V] directly to see the shared blueshifted broad component, the absence of a narrow [Ne V] core, and the phase stratification implied by the different neon ionization states; also note the nearby [Cl II] l…