Radial distribution of helium in the Milky Way

Abstract

We present preliminary results of the study of the radial distribution of helium in the Milky Way. We use 37 spectra from 23 Galactic HII regions observed with VLT, GTC and Magellan Telescope. Using PyNeb, we calculate the abundance of He$^+$ with all the He$\thinspace$I detected lines. In most cases, both the average abundance of He$^+$ and its associated dispersion are higher when triplet lines are used. Although corrections for collisional processes are considered in the calculations, the differences in the He$^+$ abundance are not negligible between both spin configurations. This suggests that self-absorption processes are important in most triplet lines. Four ICFs were used to estimate the contribution of He$^0$ in the total abundance. The resulting radial distribution of helium has a negative slope when singlet lines are used, regardless of the ICF used.