| The structure and morphology of galaxies can not only reflect the physical characteristics of galaxies,but also have a certain relationship with other physical properties[1].For example,early-type galaxies generally have the characteristics of old age,weak extinction,red color,low star formation rate,and are mostly located in high-density regions,while late-type galaxies have the opposite characteristics of early-type galaxies[2].In addition,different types of galaxies may also indicate that their formation and evolution are different.Therefore,studying the morphological characteristics of galaxies at different redshifts can help us better understand how galaxies and the universe are formed and evolved[3].In order to understand the physical properties of galaxies of different morphological types,we first need to classify galaxies according to their morphological characteristics.In this way,a reasonable classification method is particularly important.In this paper,the morphological analysis and statistical research on the selected LBGs?Lyman Break Galaxies?galaxies with redshifts of z3 in the COSMOS sky area are carried out.The COSMOS celestial region is a celestial region of about 2square degrees.The larger celestial region can expand the statistical samples in the study of LBGs galaxy morphology and provide better statistical constraints for models that study the formation and evolution of galaxies[4][5].In this paper,GALFIT software was used to fit the morphological parameters of the high resolution images of the selected sample of the Hubble Telescope?HST?F814W band.The Sérsic index and effective radius obtained from the fitting were combined with other physical properties of the galaxy such as mass and star formation.Rate,color,etc.have been statistically analyzed and studied.The structure of this article is as follows:The first chapter mainly introduces the research background,significance and current status of galaxies morphological classification research at home and abroad,and elaborate on the development process of galaxies morphological research and three galaxies morphological classifications of visual classification system,model classification system and non-model classification system The characteristics,advantages and disadvantages of the system,and applicable conditions,etc.The use of advanced techniques and methods to observe and study galaxies with high redshift and large mass(mass?1010M?)is a hotspot and focus in the study of galaxy formation and evolution.Studying the evolution of galaxies'morphology and structure over time provides important help and clues for us to study the formation and evolution of galaxies,and the most direct observation data we can get to express the structural characteristics of galaxies is the morphology of galaxies[2].Furthermore,comparing the basic unit of the studied universe,the morphology and structure of galaxies at different redshifts,with known models,we can further understand the formation and evolution mechanisms of galaxies and even the universe[6].The second chapter mainly introduces the data source,sample selection and processing.The sample selected in this paper comes from the COSMOS sky area,which is about 2 square degrees.The existing high-resolution imaging observations of the F814W band of the Hubble telescope are more suitable for studying the morphological statistical characteristics of high redshift galaxies.Observational data in the celestial region can expand the research sample of LBGs galaxy morphology.We use the COSMOS sky area UltraVISTA R-band photometric star catalog to select the LBGs with red shift z3 by UV drop-out method,and find their corresponding F814W band observation images.The third chapter introduces in detail the process of parameter fitting the images of the selected LBGs galaxy samples in the F814W band.First introduced the software used to extract the basic parameter information such as the position,magnitude,effective radius,and ellipticity of the galaxy we need from the astronomical image-SExtractor and its operation method,which is used in many large-scale surveys.It is widely used in the light process;then introduces the PSF image generation software used to correct the point diffusion effect when performing morphological fitting-Tiny Tim,Tiny Tim can be used to generate the Hubble telescope observation area very conveniently PSF of images in different wave bands;Finally,the software used to shape the two-dimensional images of galaxies,GALFIT,is introduced.GALFIT can use different adjustable parameter function models to simulate the light distribution of celestial photometric images Together,we can fit the galaxies of different shapes by adjusting the parameters of the function model it uses.On this basis,we introduced the detailed fitting process of using GALFIT to fit the LBGs in the COSMOS sky area we selected.Finally,the selection of galaxy morphology parameters under the unmodeled galaxy morphology classification system is introduced and used to analyze LBGs with redshifts z3 in the COSMOS fields.The fourth chapter is the results of the statistical analysis of the morphological properties of LBGs galaxies.Based on the GALFIT fitting data such as Sérsic index,effective radius,magnitude,galaxy aggregation index C,Gini coefficient G and moment index M20,combined with the physical properties of the galaxy's star mass,star formation rate and other physical properties,the statistics of the LBG galaxy are analyzed Characteristics,and compared with the properties of other galaxies with redshift z3 in the sky.The research shows that the Sérsic index?median=0.825,average=0.895?and effective radius?average=1.814kpc,median=1.509kpc?of the456 LBGs galaxies z3 in the COSMOS sky region we selected)Are small,and galaxies with a small Sérsic index are generally late-type galaxies;the LBGs of z3and all the galaxies of z3 in the sky area are mostly distributed in the range of 109M?10111 M?,and The LBGs galaxies of z3?average=7.76×109M?,median=8.31×109M??compared to other galaxies of z3 in the sky area?average=6.92×109M?,median=7.24×109M??,quality The median and average value of is slightly larger;the LBGs of z3 and the mass of all galaxies of z3 in this sky area are mostly distributed in the range of 10 M?yr-1102 M?yr-1,and zThe median and average SFRs of the 3 LBGs in galaxy 3(mean=30.2 M?yr-1,median=28.84 M?yr-1)are greater than other galaxies in the sky area z3(mean=18.62 M?yr-1,median=19.05 M?yr-1);and these galaxies have no particularly prominent morphological characteristics compared to other ordinary galaxies in z3 in the sky area.The fifth chapter is a summary of the prospects,mainly introducing the research process,research flaws and later optimization and supplement of this article.In order to further study the morphological characteristics and other characteristics of LBGs galaxies,we also need larger and more sky areas to obtain more observation data information of LBGs galaxies,in addition to optimize and supplement our research process. |
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