The stars, gas, and star-formation during galaxy transformation in the early Universe

Po-Feng Wu^1*

¹Academia Sinica, Institute of Astronomy and Astrophysics, Taipei City, Taiwan

* Presenter:Po-Feng Wu, email:pfwu@asiaa.sinica.edu.tw

Why and how galaxies stop forming stars is one of the most important unsolved questions in galaxy evolution. I present the most comprehensive multi-wavelength, imaging, and spectroscopic observations of galaxies which are transforming from active star formation to quiescent at 7 billion years ago, the epoch that the cosmic star-formation rate density is dropping rapidly.

The data collected by various observing facilities, including HST, Spitzer, VLT 8m, VLA, and ALMA, allow us to investigate the spatial distributions of stars, gas, and star-formation as well as the kinematics of the same set of such kinds of galaxies in the distant Universe.

I will demonstrate that the truncation of star-formation in the distant Universe is part of the process of a centrally-concentrated starburst induced by galaxy-galaxy interaction a few hundred million years ago. I will show that during this phase, the properties of galaxies can change rapidly, causing some inconsistencies of galaxy properties found among different studies. The detailed description of this transformation process is the crucial step toward understanding how star-formation truncation in the early Universe.

Keywords: Star formation, galaxy evolution, galaxy quenching, early Universe