Oral Presentation
Galaxy evolution within the cosmic web at high redshift : case study for z=2.5 protocluster with ALMA
Presenter: MINJU Lee (The University of Tokyo)
I present our recent results from ALMA observations that reveal gas properties of star forming galaxies in the protocluster 4C23.56 at z=2.5. The cold gas is one of the key ingredients to understand galaxy evolution. There is almost a desert of information on cold gas properties for high redshift (proto)clusters compared to nearby (cluster) studies, particularly of the typical star forming galaxies on the main sequence. From the four and seven detections in 1.1 mm dust continuum and CO(3-2) emission line, respectively, we firstly confirmed the amount of the cold gas locked within the massive population, Mstar >4e10 Msun, on the main sequence. The protocluster galaxies normally have a similar gas content and a gas fraction known from general field studies at similar redshift (on the main sequence). The average gas mass is typically Mgas ~ 5e10 Msun with the gas fraction of fgas ~ 0.5. With an order of higher cosmic gas density of the protocluster, an intriguing positive correlation between the surface number density of galaxies and the global star formation efficiency, and the stellar mass (with the decreasing gas fraction), may suggest an important role of galaxy environment on the galaxy evolution, during the high-z cluster forming epoch. A frequent mergers are one of the mechanisms that could derive such correlation from the analysis of kinematics. Further detailed inspection of these findings can be achieved with larger samples in different environments and with higher solution imaging of the galaxies. I will finally stress that such studies require additional information from other observatories, particularly related to the ionized (or hotter) gas properties, such as metallicity and size, and kinematic information of stellar population.
asiaa.sinica.edu.tw