A MULTI-WAVELENGTH VIEW OF M17 MASSIVE STAR-FORMING REGION

ABSTRACT

In this project (A Multi-Wavelength View of M17 Massive Star-Forming Region), efforts were made to determine the distributions of polycyclic aromatic hydrocarbons (PAHs) within the M17 region. We find that PAHs are destroyed over a short distance or edge of the HII region. This PAH destruction edge can be located easily using Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) band-ratio images. We try to find out the relative roles of extreme ultraviolet (EUV) and X-ray photons in the destruction of PAHs concluding that X-rays are not an important PAH destruction mechanism in M17 or by extension, in any other Galactic HII region. The result gotten supports the hypothesis that PAHs are destroyed by EUV photons within HII regions. PAHs dominate the mid-IR emission in the neutral Photo-dissociation Region (PDR) beyond the ionized gas.

TABLE OF CONTENTS

TITLE PAGE                                                                                                                              I

APPROVAL PAGE                                                                                                                   II

DEDICATION                                                                                                                          III

ACKNOWLEDGEMENT                                                                                                        IV

TABLE OF CONTENTS                                                                                                           V

ABSTRACT                                                                                                                              VI

CHAPTER ONE

INTRODUCTION                                                                                                                           1

1.1  BACKGROUND OF STUDY                                                                                                   1

      1.1.1 PURPOSE OF STUDY                                                                                                    5

1.1.2 AIM OF THE PARAMETER INVESTIGATED                                                             6

1.2 SPECTRAL CLASSIFICATION OF STARS                                                                          6

1.2.1 MAIN CLASSIFICATION                                                                                                    7

1.2.2 SUB-CLASSIFICATION                                                                                                       8

1.2.3 HERZSPRUNG-RUSSELL DIAGRAM (H-R DIAGRAM)                                                9

            1.2.3.1 THE MAIN SEQUENCE                                                                                        9

1.3 THE GEOMETRY OF M17                                                                                                    11

CHAPTER TWO

LITERATURE REVIEW                                                                                                              15

2.1 MORPHOLOGY OF M17                                                                                                       15

2.2 THE DIFFUSE EMISSION                                                                                                     17

2.3 GLIMPSE AND 2MASS                                                                                                         20

2.4 MID-COURSE SPACE EXPERIMENT (MSX)                                                                    21

CHAPTER THREE        

DATA ANALYSIS AND RESULTS                                                                                            23

3.1 SOURCE OF DATA                                                                                                               23

CHAPTER FOUR

 DISCUSSION AND CONCLUSION                                                                                          26

4.1 PAH EMISSION                                                                                                                      26

4.2 PAH DESTRUCTION BY EUV AND X-RAY PHOTONS                                                  27

4.3 CONCLUSION                                                                                                                        31

REFERNCES                                                                                                                                 33