The SAMI Galaxy Survey: the Galaxy Stellar Mass Function for Fast and Slow Rotators in the Local Universe

The importance of galaxy stellar mass function (SFM) is that it underlies the mass assembly history of galaxies, making itself a standard tool to gain insights into galaxy evolution. With increasing observational data on large samples of galaxies in both local and the high-redshift universe, considerable efforts have been made to study the overall properties of the population of galaxies and its evolution over cosmic time. Among the studies, galaxy morphology and structure are a topic of particular interest, as they are thought to be intimately tied to a galaxy’s formation and evolution. Spheroidal structures are largely believed to form through dissipationless mergers, while disc-like structures largely arise from the dissipational gas physics process. Thus SFMs divided into different morphological types, or different components directly tells the mass budget assigned to distinct physical processes. However, as suggested by the bimodal distribution in colour and in their kinematic properties, the origination of spheroids, including early-type galaxies and galactic bulges, is difficult to be constrained to unified dissipationless processes, implying morphology divisions not among the most fundamental parameters correlating with galaxy evolution. On the other hand, that galaxy assembly histories are embedded in stellar dynamics makes their kinematic information, including angular momentum and spin parameters, great tools to trace back the dominant physical processes in forming galaxies, shedding light on finding the essential reasons that make galaxies look diverse today. Here we propose to study the SFM of low-redshift galaxies based on integral field spectroscopy from SAMI observation, from which we can retrieve both morphological and resolved kinematics information for the largest sample in the local universe. In this work, we will find the SMF of galaxies divided into fast and slow rotator (as well as different types of fast rotators), and revisit the SFMs for different morphology types as a comparison. We will compare the mass dependence between galaxies in different kinematic and morphological types, from which, finding clues on the physical processes that have driven the mass-dependent evolution for galaxies. Our quantitative result will also give good constraints to current cosmological simulations. A key element of this work will be the use of the R-package ‘dftools’ developed by Obreschkow at all. which allow us to correct the SAMI survey for its selection and observational biases.

Publication Date: 
September 2019