Large-scale spatial distribution of 1483 candidate young stars (small dots) in the Orion and Taurus-Auriga associations. The X-ray sources have been selected from the ROSAT All-Sky Survey. Their space density is color-coded, where the parameter α represents the discriminant probability; the higher α, the more probable is the occurrence of a source corresponding to a young star. Circles refer to sources observed spectroscopically in this work, while triangles represent targets previously analyzed by Alcalá et al. (1996) and Alcalá et al. (2000). The symbol size increases with the lithium equivalent width EW (0,  <150, 150–300,  > 300 mÅ). The dashed line coincides with the position of the Galactic plane, while the dash-dotted line represents the Gould Belt, as given by Guillout et al. (1998). The sky strip (195° < l_II < 205°,  − 60° < b_II < 15°) selected by us across the Gould Belt in the Orion vicinity is also shown together with the area selected on the X-Clump 0534+22 (see Sect. 4). The regions of enhanced density of young star candidates and of high-lithium stars southward of the Galactic plane coincide with the location of the Gould Belt midplane. North is up and East to the left.

Large-scale spatial distribution of all targets observed at low and/or high resolution. Circles refer to sources observed spectroscopically in this work, while triangles are targets analyzed by Alcalá et al. (1996) and Alcalá et al. (2000). The symbol size increases with the lithium equivalent width (0,  < 150, 150–300,  > 300 mÅ). The arrows refer to stars for which we measured the iron abundance (downward for  [Fe/H]  ≤  −0.14, horizontal for  −0.14 <  [Fe/H]  ≤ 0.06, upward for  [Fe/H]  > 0.06; the central bin corresponds to the average metallicity of our targets  ± 1σ). Dotted lines represent the strip, long-dashed line is the Galactic plane, while dash-dotted lines represent the Gould Belt disk, as outlined by Guillout et al. (1998). The CO J = 1 → 0 emission contour maps by Dame et al. (2001) of the Orion, Monoceros, and Taurus molecular clouds, and the λ Orionis H ii region are also overlaid.