Extended Data Fig. 2: ALMA emission maps of CH3OH in comet 12P.
From: A D/H ratio consistent with Earth’s water in Halley-type comet 12P from ALMA HDO mapping
The data, observed in Band 6 (between 2024 April 18-25; left) and Band 5 (2024 May 4; right), have been spectrally integrated, continuum-subtracted, and are centered on the thermal continuum peak. The Band 6 image is integrated over 14 transitions, with a contour separation of 10σ, while the Band 5 image is integrated over 8 transitions, with 5σ contours (see Supplementary Table 2 for details). Inset panels (upper right) show the spectral line profiles of selected transitions as a function of cometocentric velocity (v), extracted at the origin (8 lines in the Band 5 CH3OH spectrum have been averaged in velocity space, to improve the signal-to-noise rato). The spatial resolution (beam FWHM) is shown lower left, and the directions of the (sky-projected) comet-Sun and orbital trail vectors are shown lower right.
