SITELLE Hyperspectral Cubes Map Northern Jet as Ballistic Ejecta Linked to Crab Nebula Central Cavity

The study acquired hyperspectral cubes covering [O II], Hβ, [O III], [N II], He I, [S II] and Hα across a field that includes the 45-arcsec-wide chimney. SITELLE’s imaging Fourier transform spectroscopy delivered velocity-resolved maps that geometrically tie the filamentary network to the jet funnel, showing near-ballistic motion and no southern counterpart. This directly supports an early PWN role in carving the structure rather than later interactions alone.

Three formation channels remain plausible: bipolar outflow collimated by a progenitor disk, a breach in the ejecta shell, or a pre-existing low-density mass-loss channel. Each explains different combinations of the jet’s extreme collimation, one-sidedness and kinematics, yet none is ruled out by the present data. Prior 2D studies had suggested the cavity but lacked the full spatial-velocity resolution now achieved.

Discriminating scenarios requires fully 3D hydrodynamic simulations evolved from the progenitor through PWN expansion. Such models must reproduce both the observed cavity-jet continuity and the absence of a symmetric southern feature within the remnant’s 1000-year age. The current reconstruction supplies precise initial conditions and boundary constraints for those simulations.

Follow-up integral-field observations at higher spectral resolution and targeted X-ray proper-motion measurements will test whether the jet continues to expand ballistically or shows deceleration at its tip.