Speaker
Description
We present spatially resolved JWST NIRSpec and MIRI integral-field spectroscopy of the nebula surrounding the ultraluminous X-ray source Holmberg II X-1, providing the first direct view of high-ionization infrared emission on scales of only tens of parsecs in this system. By combining emission-line surface-brightness maps, diagnostic line ratios, and kinematic profiles, we detect intense [Ne V] and [Ne VI] emission that is strongly confined to a localized sector of the nebula, in contrast to the more extended hydrogen recombination and low-ionization emission. All detected transitions exhibit narrow velocity dispersions, with no evidence for broad wings or systematic velocity shifts, ruling out fast radiative shocks as the dominant excitation mechanism. The highest-ionization gas is aligned with previously identified radio structures, suggesting directional escape of hard photons from the accretion flow. Comparisons with other low-metallicity galaxies hosting ULXs show that similar high-ionization luminosities can arise in very different star-formation environments, pointing to the dominance of compact accretion as a source of hard ionizing radiation. These results demonstrate that anisotropic hard-photon feedback from compact objects can imprint observable signatures on the interstellar medium, providing a resolved laboratory for studying the coupling between accretion power and nebular ionization in extreme environments.
