Free electron density distribution of the milky way

Uzun, Nezihe
The aim of this study is to determine the free electron density distribution of the Milky Way Galaxy using dispersion measures of pulsars. By making use of 1893 Galactic pulsar, 274 supernova remnant and 543 HII region data, the overall free electron density map of the Galaxy is obtained by using a 3D mesh-like structure of irregular size. The main idea behind the study is to treat each 3D section of the Galaxy privately considering the distance versus dispersion measure graphs of the pulsars that fall into those sections. This sectioning procedure is followed using a trial and error method and results in 348 sections through which free electron densities can be calculated. Using linear fits of distance versus dispersion measure graphs, pulsars that deviate from the curves are investigated and new distances are adopted to 140 of them that are decided to have wrong distance estimates. By this way both distance values and the free electron densities of the sections are improved. In the end, by using the free electron density values of 348 sections, a projected and cumulative free electron density map of the Galaxy is plotted in polar coordinates. This map is compared with three different spiral arm models and it is seen that the best accordance is with Hou et al. 2009 spiral arm model.
Citation Formats
N. Uzun, “Free electron density distribution of the milky way,” M.S. - Master of Science, Middle East Technical University, 2012.