3I/ATLAS · KCWI
19 January 2026

Molecular coma maps
Keck II/KCWI maps of 3I/ATLAS on 2026 January 19. Upper panels show band-plus-continuum emission around CN (386.5-389.0 nm) and C3 (397.5-415.0 nm); lower panels show continuum-subtracted emission, with CN measured over 387.55-389.55 nm. The CN residual map has provisional flux calibration; other panels retain electron-rate units. North is up and east is left. Cyan Anti-Sun and white +v_hel arrows show projected antisolar and positive heliocentric-velocity directions; arrow lengths are illustrative. Scale bars span 5000 km. Extended CN-region emission and the central C3 excess depend on continuum and background subtraction.

Neutral nickel maps
KCWI maps integrated over +/-0.4 nm around Ni I 351.51, 352.45, and 361.94 nm, before (upper panels) and after (lower panels) continuum subtraction. Dashed circles mark the 5-arcsec extraction radius; no annulus subtraction is applied. The 361.94-nm identification remains tentative. North is up and east is left; arrows follow the molecular-map convention. These maps show morphology; the production estimate uses fitted line profiles and their covariance.