Title: Exploring the formation of red sequence galaxies in the local universe Speaker:Cai-Na Hao
Abstract: It is well-known that galaxies are located in two different groups in the color-magnitude or color-stellar mass diagrams: the blue cloud dominated by star-forming late-type galaxies and the red sequence occupied by quiescent early-type galaxies. It has been proposed that galaxies on the red sequence are the end products of blue cloud galaxies, and there may be two different evolutionary pathways for the transformation. In this talk, I will introduce our efforts on exploring the formation of massive red sequence galaxies via two threads. Firstly, I will present our studies on the fast mode of the evolutionary pathway, based on a sample of 89 (Ultra-)Luminous Infrared Galaxies at the late stage of mergers. By investigating the star-formation main sequence relation, the color-stellar mass diagram and the star formation history indicators (EW(Hα), EW(HδA), Dn(4000)), we found that these advanced-merger (U)LIRGs are probably in the process of evolving from blue to red rapidly (10^7-10^8 yrs), in support of the fast evolutionary mode from the blue cloud to the red sequence. Secondly, I will introduce our exploration of the formation mechanisms of spiral galaxies on the red sequence. The existence of red spirals poses a challenge to the scenario that the quenching of star formation must be accompanied by morphological transformation. And it may not fit into either of the two evolutionary pathways. Based on SDSS imaging and MaNGA IFU data, we studied various physical properties of a sample of ~280 red spirals, and compared them to red ellipticals and blue spirals at similar masses. We found that local massive red spirals are probably remnants of very gas-rich major mergers at redshift above 1.
Biography: Dr. Cai-Na Hao is a professor at Tianjin Normal University. She was a postdoc at the Institute of Astronomy, University of Cambridge after she obtained her PhD from the National Astronomical Observatories, Chinese Academy of Sciences (CAS). Her main research interests are the observational studies of galaxy formation and evolution at both low and high redshifts, including earlier work on infrared QSOs, star formation rate calibrations and recent work on redshift~2 Lyman-alpha emitters, local massive (U)LIRGs, spirals and ellipticals. She has published more than 40 refereed papers in major astronomical Journals, which has been cited for over 3900 times.