Free electron density distribution of the milky way

Date

2012

Author

Uzun, Nezihe

Metadata

Show full item record

Item Usage Stats

152
views

0
downloads

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.

Subject Keywords

Milky Way., Galaxies., Pulsars.

URI

http://etd.lib.metu.edu.tr/upload/12614312/index.pdf
https://hdl.handle.net/11511/21307

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

Energy spectrum of a 2D Dirac oscillator in the presence of a constant magnetic field and an antidot potential Akçay, Hüseyin; Sever, Ramazan (2016-07-04) We investigate the energy spectrum and the corresponding eigenfunctions of a 2D Dirac oscillator confined by an antidot potential in the presence of a magnetic field and Aharonov-Bohm flux field. Analytical solutions are obtained and compared with the results of the Schrodinger equation found in the literature. Further, the dependence of the spectrum on the magnetic quantum number and on the repulsive potential is discussed.
Shape similarity measurement for boundary based features Arica, N; Yarman Vural, Fatoş Tunay (2005-01-01) In this study, we propose two algorithms for measuring the distance between shape boundaries. In the algorithms, shape boundary is represented by the Beam Angle Statistics (BAS), which maps 2-D shape information into a set of 1-D functions. Firstly, we adopt Dynamic Time Warping method to develop an efficient distance calculation scheme, which is consistent with the human visual system in perceiving shape similarity. Since the starting point of the representations may differ in shapes, the best corresponden...
Geospatial Object Recognition From High Resolution Satellite Imagery Ergul, Mustafa; Alatan, Abdullah Aydın (2013-01-01) In this paper, a novel automatic geo-spatial object recognition algorithm from high resolution satellite imagery is proposed. The proposed algorithm consists of two main steps; the generation of hypothesis with a local feature based algorithm and verification step with a shape based approach. The superiority of this method is the ability of minimization of false alarm number in the recognition and this is because object shape includes more characteristic and discriminative information about object identity ...
Frequency Selective Characteristics of a Plasma Layer with Sinusoidally Varying Electron Density Profile GÜREL, ÇİĞDEM SEÇKİN; Oencue, Emrah (Springer Science and Business Media LLC, 2009-06-01) In this study reflection, absorbtion and transmission characteristics of a plasma layer having sinusoidally varying electron number density are analysed. In the analysis, plasma layer is divided into thin subslabs with constant electron number densities. The general frequency selective behavior of the plasma is investigated by varying the plasma parameters, external magnetic field excitation and sinusoidal electron distribution in order to be used in recent plasma applications.
Beam test results from a fine-sampling quartz fiber calorimeter for electron, photon and hadron detection Akchurin, N; et. al. (1997-11-11) We present the results of beam tests with high-energy (8-375 GeV) electrons, pions, protons and muons of a sampling calorimeter based on the detection of Cherenkov light produced by shower particles. The detector, a prototype for the very forward calorimeters in the CMS experiment, consists of thin quartz fibers embedded in a copper matrix. Results are given on the light yield of this device, on its energy resolution for electron and hadron detection, and on the signal uniformity and linearity. The signal g...

Citation Formats

N. Uzun, “Free electron density distribution of the milky way,” M.S. - Master of Science, Middle East Technical University, 2012.