Study On The Formation And Evolution Of Massive Compact Galaxies

The formation and evolution of galaxies are closely related to the cosmic environment.Galaxies in different cosmic periods have different properties,it is very important to study the formation and evolution of galaxies to reveal the physics of the early universe.The formation of massive galaxies have relation to early universe,thus the study of the evolution of massive galaxies has always been a hot topic in the study of the structure and evolution of galaxies.Previous studies on high-redshift massive quiescent compact galaxies have suggested that high-redshift massive quiescent galaxies have similar structures to massive elliptical galaxies in the local universe,and there should be an evolutionary link between the two.Therefore,it is necessary to study the evolutionary mechanisms of high-redshift galaxies evolving into nowadays massive galaxies within hundreds millions of years.The evolution mechanisms of galaxy's size is supported by researchers in several aspects:(1)progenitor bias;(2)the feedback effect of active galactic nuclei;(3)merger mechanism,etc.There is a theory widely supported by researchers that the formation of galaxies can be divided into two stages.The core region of a galaxy is formed at higher redshift,while the outer extension is formed at lower redshift.With the supporting of the research and the development of research techniques,the researchers suspect that nowadays massive galaxies with compact core is similar to high-redshift quiescent galaxies,this idea for the evolution of the massive galaxy opened up a new way of thinking,and provides a new evolution path.Our study is based on analyzing the spectra of compact cores to research the evolution path of massive galaxies.In this paper,we selected 182 massive galaxies in local universe with compact cores from Sloan Digital Sky Survey data,and use the Starlight software to study 182 local massive galaxies,whose cores fulfill the compactness criterion.The redshift range is 0.02-0.06 to ensure the observed range on the sky is exactly the effective radius of high-redshift compact galaxies.We regard the bulge component satisfying the compactness criterion as the compact core.We work on the median stacked spectra to gain high quality input spectra,and we find that the median age of galaxy with compact core is about 11.8 Gyr,this result agrees with the idea that the core of local massive galaxy may form earlier and extended part forms later.The analysis of morphology of sample shows though most of galaxies show early type characteristics,about 20%of sample galaxies are in late-type systems,this may imply that high-redshift compact galaxies are survived as compact cores in different kinds of present-day massive galaxies.