The Isophotal Study Of Star-forming Galaxies At 0.5<z<1.8 In Candels

The structure of high-redshift galaxies is one of the most popular research fields of galaxy formation and evolution.However,the research progress on the structure of high-redshift galaxies had been slow,due to the red shift in transforming from observed bands to the rest-frame bands and the effect of cosmic surface brightness dimming,until before the last ten years.Nowadays,with the aid of the HST WFC3/IR high-resolution image data,people have known many of the structural properties of high-redshift galaxies.The isophotal properties of galaxies are coupled with the structure of galaxies.Therefore,one can trace the evolution of galaxy structure by investigating the isophotal evolution of galaxies.However,at present,no related work is done for galaxies at intermediate and high redshifts.In this thesis,we selected ~4,600 UVJ-defined star-forming galaxies(SFGs)between redshift 0.5 and 1.8 in the GOODS-S and UDS fields of CANDELS,and have measured their ellipticity(?)and disk / box parameters profiles with high accuracy.Based on these data,we first make statistically robust analyses of the ellipticity and profiles of galaxies at intermediate and high redshifts on an evolutionary grid laid by stellar mass and redshift.Based on the average size-mass relation in each redshift bin,we divide our galaxies at a given mass into relatively Small SFGs(SSFGs;smaller than the average)and Large SFGs(LSFGs;larger than the average),the main results are as follows:(1)At low masses(M*< 10 M?),the SSFGs generally have nearly flat ? and A4 profiles in both edge-on and face-on views,and the values at all radii are almost zero.However,the elliptical profile of the edge-on LSFGs is mainly characterized by a monotonic increase with radius and the intermediate region of galaxies exhibits > 0(Disky)features.(2)At high masses(M*> 10 M?),in edge-on views,the ? and profiles of SSFGs and LSFGs both rise to the maximum and then decrease.At the same time,the intermediate region of galaxies shows a more distinct disky shape.Such the feature is more prevalent at lower redshifts(z < 1.4)or for more massive(M*> 10 M?).(3)Along the evolutionary paths laid out by stellar mass and redshift,the ellipticities of both SSFGs and LSFGs in the central region(R=1.5 kpc)show a declining trend.The above observational results show that: at the intermediate and high redshifts,the low-mass SSFGs likely have not formed a stellar disk(or the structure of stellar disk is different from that in the nearby universe),the structure of low-mass LSFGs is similar to that of nearby disk galaxies.During the evolutionary process of SFGs towards lower redshifts and higher stellar mass,the central bulges and outer stellar halos build up in line with the growth of disks in the intermediate region of galaxies.