CO Observation Study Of G172 Molecular Cloud Complex

In order to learn the structure and physical properties of G172 molecular cloud complex,we carried out the CO(¹²CO,¹³ CO,C¹⁸O)observations conducted with the13.7-meter millimeter-wavelength telescope of the Purple Mountain Observatory（PMO）on this area.The first chapter introduces the properties and the research significance of molecular cloud,CO survey and the Milky Way Imaging Scroll Painting project of PMO.Molecular clouds are places for stars to form,the research of the formation and evolution of molecular cloud can provide an important basis for the study of the interstellar medium and star formation.The research of molecular cloud relies largely on the molecular spectral lines,CO spectral line is the most widely used among them.The ongoing project—MWISP of PMO is a large CO survey toward the northern Galactic Plane,it covers a wide range of area of the sky with high spatial resolution,and has the ability of simultaneous observations in 12CO/13CO/C18O（J=1-0）lines,this survey is designed to get more comprehensive information of the molecular clouds in galactic plane.The second chapter introduces the past studies of G172 molecular cloud complex.There have been researches of HII regions,nebulae,clusters and so on,it has not done research of filamentary structures（filaments）,but the main structure of this area is filament.We do basic research on the distribution and physical properties of the molecular cloud in this area.First,we introduce the process of survey and data processing and data store,after that,we introduce the recent research advance of G172 molecular cloud complex in detail.We extract filaments in the spatial distribution and velocity structure map of13 CO,combined with velocity structure of 12 CO,then we extract five filaments in G172 molecular cloud complex and named them after the peak position of 13 CO integrated intensity of each filament.We calculate physical quantities of filaments and molecular cloud clumps in terms of excitation temperature,column density,mass,optical depth and so on in the use of LTE approximation.For distance,Bayesian distance calculator is in use in this paper,and we make a contrast with a three-dimensional map of interstellar dust reddening.Molecular clouds of G172 molecular cloud complex located in Perseus arm in view of distance.At the end of thethird chapter,we use Gauss Clumps to search for molecular clumps in G172 molecular cloud complex with a low threshold of 6 times of rms value and find 183 clumps.We list the physical quantities of filaments and molecular clumps in chapter four.MWISP G170.658-00.250 has the largest mass among five filaments and the weakest filament-MWISP G172.858-00.367 has the lowest mass.There are some molecular cloud clumps with greater masses,most of the molecular cloud clumps has virial mass higher than LTE mass.Chapter five introduces the future research direction of G172 molecular cloud complex.