JWST Discovery of a Very Fast Biconical Outflow of Warm Molecular Gas in the Nearby Ultra-Luminous Infrared Galaxy F08572+3915 NW

TL;DR

JWST observations reveal a fast, kpc-scale biconical outflow of warm molecular gas in the ULIRG F08572+3915 NW, indicating active quasar feedback impacting galaxy evolution.

Contribution

First JWST mid-infrared integral field spectroscopy of this galaxy uncovers a high-velocity warm-molecular outflow with detailed kinematic and thermal properties.

Findings

Outflow velocity reaches up to 3000 km/s.

Outflowing gas is warmer than disk material, likely due to shock heating.

Warm outflow is faster than cold molecular outflows from previous observations.

Abstract

We present new James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) Medium-Resolution Spectrometer (MRS) observations of the nearby ultra-luminous infrared galaxy (ULIRG) F08572+3915 NW. These integral field spectroscopic (IFS) data reveal a kpc-scale warm-molecular rotating disk and biconical outflow traced by the H$_2$ $\nu$ = 0$-$0 S(1), S(2), S(3), and S(5) rotational transitions. The outflow maintains a relatively constant median (maximum) projected velocity of 1100 km s$^{-1}$ (3000 km s$^{-1}$) out to $\sim$ 1.4 kpc from the nucleus. The outflowing H$_2$ material is slightly warmer (640 $-$ 700 K) than the rotating disk material (460 $-$ 520 K), perhaps due to shock heating in the highly turbulent outflowing material. This outflow shares the same kinematics and orientation as the sub-kpc scale warm-H$_2$ outflow traced by the ro-vibrational H$_2$ lines in Keck AO near-infrared IFS data. However, this warm-H$_2$ outflow is significantly faster than the sub-kpc scale cold-molecular outflow derived from multi-transition far-infrared OH observations with Herschel and the $\gtrsim$ kpc-scale cold-molecular outflow mapped by mm-wave interferometric CO 1$-$0 observations with IRAM-PdBI and NOEMA. The new JWST data bolster the scenario where the buried quasar in this ULIRG is excavating the dust screen, accelerating perhaps as much as 60\% of the dusty warm-molecular material to velocities beyond the escape velocity, and thus influencing the evolution of the host galaxy.