3I/ATLAS · GMOS IFU
26 November 2025

Molecular-region maps
Gemini North/GMOS IFU observations of 3I/ATLAS on 2025 November 26, totaling 1200 s. These observations were part of the Shadow the Scientists program. Columns show CN (385.5-389.25 nm), the C3 core (402-407.5 nm), C2 at 474 nm (463-474.5 nm), and the narrow 515.94-516.81-nm candidate. Upper stamps retain the continuum; lower stamps subtract it. Only the narrow C2 pair includes the refined solar/sky treatment. Each panel has its own scale in normalized nm per square arcsec; the lower-right scale starts above zero. Dashed radii are 1.25 arcsec, except C3 (0.50 arcsec). North is up and east left. Cyan Anti-Sun and white +v_hel arrows give projected antisolar and positive heliocentric velocity directions; lengths are illustrative. Bars span 2000 km. Small gaps were median-filled for display only, and narrow C2 has 0.30-arcsec smoothing. Measurements use the original masks and unsmoothed arrays. Residuals depend on continuum and background treatment; the narrow C2 identification remains conditional.

Extracted aperture spectra
Reconstructed flux density (upper plot), normalized reflectance (middle), and native-sampling molecular-region traces (bottom) for complete circular apertures of radius 0.50, 1.00 and 1.25 arcsec. The upper two panels use 1-nm bins, each requiring all eight native samples to be valid; any masked sample removes the entire bin. Isolated valid bins are invisible in the lines drawn without point markers. These display choices widen apparent gaps relative to the zooms, which retain valid samples at native 0.125-nm spacing. The 474-nm zoom ends at 480 nm and excludes the separate masked interval near 485-487 nm. Missing samples remain masked; the display binning does not affect the production estimates. Reflectance is normalized over 545-555 nm. Shading propagates the recorded variance and nearest-channel covariance; it excludes the shared 18.7% flux normalization error and unquantified response and background uncertainties. Nested apertures share data. These sky-retained baseline spectra precede the focused C2 transient rejection and solar/sky fits; labeled wavelength regions do not imply secure molecular identifications. Wavelengths are air, topocentric.