The Isophotal Study Of High-redshift Quiescent Galaxies In CANDELS

The isophotal properties of galaxies are coupled with the structural properties of galaxies.Therefore,investigating the isophotal evolution of galaxies is helpful to understand the evolution of galaxy structure.The ellipticity(?)and disk / box parameter 4are the most dominant parameters to describe the isophotes of galaxies.Studying the spatial distributions of ? and 4is helpful to identify the structural components of galaxies,such as disks,bulges and stellar halos.In this thesis,we selected a large sample of quiescent galaxies between redshift 0.5and 1.5 in all five CANDELS fields.We applied the 2-D bulge/disk decomposition technique to divide the whole sample into two groups: bulge-dominated and disk-dominated quiescent galaxies,in order to studythe influence of the ratio of different components on the isophotes of galaxies.In addition,we further divide our sample into two categories: high inclined and low inclined galaxies.By comparing the radial distributions of ?and 4in different inclinations and different stellar components,we study the similarities and differences of their isophotal properties.As a result,we show that the viewing angle might be the most dominant parameter to impact the isophotal properties of high-z galaxies;Main results are shown as follows:(1)Low-inclined(low inclin,?global< ?global,med)quiescent galaxies generally have nearly flat ? and 4,whatever for the entire sample of quiescent galaxis orsubsamples of bulge-dominated or disk-dominated galaxies.Moreover,the median values of ? and 4at all radii are nearly zero.;(2)High-inclined(high inclin,?global> ?global,med)quiescent galaxies generally have monotonically increasing profiles ?and 4profiles,whatever for the entire sample of quiescent galaxis or subsamples of bulge-dominated or disk-dominated galaxies.Such the feature is more remarkable at higher redshift.The above observational results show that the inclination has the have a great influence on the isophotal properties of quiescent galaxies at high redshifts.When observing quiescent galaxies in low inclination,galaxiesgenerally exhibit the feature of non-rotating components(dominated by velocity dispersion);however,when observing galaxies in high inclination,galaxies generally exhibit the rotating supported freature.These findings indicate that quiescent galaxies at high redshift are likely to harbor disk-like stellar components.