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Fig. 8

image

Results from modeling the observed DCO+ peak with our simple analytic chemical model. The left column shows results for IRAS 16293−2422, while the right column shows those for VLA 1623−2417. The top row shows the input density (black) and temperature (red) as functions of radius for each system. The solid red line shows the original temperature profile used for the constant CO model (second row). The dashed red line is the profile decreased by factors of 3 and 1.5 for IRAS 16293−2422 and VLA 1623−2417, respectively, and used for the drop CO model (third row). The lower limit on the temperature is set at 8 K. In the second and third rows, the shaded range is the location of the observed DCO+ peak. The fourth and fifth rows show the observed radial profiles of DCO+ (black lines) overlaid with both Constant (dashed gray lines) and Drop CO models (solid orange lines). In all panels, the protostellar source is located on the left, and the envelope on the right, with the peak position of DCO+ indicating the disk-envelope interface. We note that the excess DCO+ 5–4 emission from the disk(-like) regions is not well reproduced by the cold DCO+ network.

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