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Fig. 4.


YSO distribution and YSO’s mean positions projected in a cartesian plane. In this coordinate frame the Sun (at X, Y, Z = 0, 0, 0) is connected to the location of Orion A with XOrion pointing toward (l/b)=(211°/−19.5°). Consequently, XOrion is similar to the distance from the Sun, while the YOrion and ZOrion components coincide roughly with the l and b distribution, respectively. The YSOs are shown in gray scale colored by σϖ. The mean positions per Δl are shown as orange filled circles (as in Fig. 3), while the two rightmost points from Fig. 3 are excluded. The gray dashed lines are lines of constant l as viewed from the Sun (2° steps from l = 206° to 216°). For orientation, the numbered boxes show the mean positions of YSOs projected near eight known clusters, as listed in the bottom left legend. In brackets we give the estimated distances (derived from Gaia DR2 parallaxes), which are used to plot the boxes.

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