Fig. 4: Comparison of ice column densities in Cha I with other clouds.
From: Cospatial ice mapping of H2O with CO2 and CO across a molecular cloud with JWST/NIRCam
Left, the total ice column densities presented as a ternary plot, showing the sum of the fractional column densities for the three ice species, that is, [H2O] + [CO2] + [CO] = 1 for each object. Marker size corresponds to the total ice column density \({N_{{{\rm{H}}_{2}}{\rm{O}}}}\) + \({N_{{{\rm{CO}}_{2}}}}\) + NCO. The 44 Cha I lines of sight are marked in black. Literature data points for other cloud background stars are shown in coloured symbols: red from ref. 8, orange from ref. 20 including data from refs. 12,13,14,16,19, pink from ref. 22 including data from refs. 12,13,14,16,17,18,21,23, and cyan from ref. 10. Note that the axis ranges are truncated for all three species, but the range sampled in each case is 0.55 (for CO and CO2 we plot 0–0.55, while for H2O we plot 0.45–1). Right, the relative column densities of CO and CO2 to H2O for the five representative spectra shown in Fig. 1 are plotted as bars in the bottom panel, with \({N_{{\rm{CO}}}}/{N_{{{\rm{H}}_{2}}{\rm{O}}}}\) in green and \({N_{{{\rm{CO}}_{2}}}}/{N_{{{\rm{H}}_{2}}{\rm{O}}}}\) in purple. The error bars on the ratios are the propagated column density errors. \({N_{{{\rm{H}}_{2}}{\rm{O}}}}/{N_{{{\rm{H}}_{2}}{\rm{O}}}}\) = 100% is marked as a dashed blue line. Median and mean values for the 44 objects in this study and the 23 background stars for which all three ices have been measured in the literature are shown in the top panel for reference. In each case, the median abundance of CO and CO2 ice (relative to H2O ice) is indicated by the orange line on the bar and the mean is shown as a solid black line. The coloured bar (green for CO and purple for CO2) displays the range lying between the first and third quartiles of the data (interquartile range). The dashed black lines show the first quartile minus 1.5 times the interquartile range and the third quartile plus 1.5 times the interquartile range. Data points outside of this range (outliers) are shown as black crosses.
