Extended Data Fig. 2: Object positions and spectral extraction procedure.
From: Cospatial ice mapping of H2O with CO2 and CO across a molecular cloud with JWST/NIRCam
a) Object positions across the ~ 6.2 arcmin2 field used to derive cospatial ice maps for H2O, CO2 and CO. The positions of the 44 individual background sources are given by black crosses. The H2 column density contours derived from Herschel far-IR observations from refs. 39,40,41 are overplotted. The yellow star marks the position of the deeply embedded Class 0 YSO Cha MMS138. b) A dispersed frame with the object positions overlaid. A black arrow marks the dispersion in the direction of increasing λ and a yellow box marks the position of a cross-dispersion direction cutout of the dispersed frame (20 by 100 pixels). c) The cutout of the dispersed frame is shown in close-up on the left, with the position of the 1 pixel-wide data column that is analysed in each step of our pipeline highlighted in dark blue. At this scale, one high flux trace is visible against the red background, but actually there are six traces in this one column (marked with light blue lines). Data from this one pixel column are plotted in dark blue on the right. Overlaid on top of these data is the 1D PSF fit to these sources (in light blue). This fitting happens for every source that lies within each 1 pixel column cutout, along the full trace length of each source, and for every source in the field.
