The density distribution of refractory elements away from the Galactic plane

The density distributions of the three refractory elements Ti II, Ca II, and Fe II away from the Galactic plane are compared with the distribution of hydrogen and dust by examining plots of N s in b versus z. It is found that Ti II and Ca II are considerably more extended in z than the H I and dust and that Fe II has an intermediate extension. Although the results are strongly influenced by sample bias, the indicated exponential scale heights for the data sample are h(Ti II) not less than 2 kpc, h(Ca II) = 1 kpc, h(Fe II) = 0.5 kpc, H(H I) = 0.3 kpc, and h(E/B-V) = 0.1 kpc. Furthermore, it is demonstrated that Ti II and Ca II are much more smoothly distributed in space than the hydrogen or dust. The large scale heights for Ti II and Ca II and their smooth distributions are most easily understood as the effect of a mixture along the line of sight of two H I phases namely, a diffuse cloud phase, in which nearly all of the Ti and Ca are tied up in dust, and an intercloud medium, where refractory elements are less depleted. It is found that Ti II and Ca II mostly trace the smoothly distributed intercloud medium. The smoothness of the distributions of Ti II and Ca II makes them candidates for use as distance indicators.