A combined photometric and kinematic recipe for evaluating the nature of bulges using the CALIFA sample

<p>Understanding the nature of bulges in disc galaxies can provide important insights into the formation and evolution of galaxies and their secular structures. For instance, the presence of a classical bulge suggests a relatively violent history, in contrast, the presence of simply an inner disc (also referred to as "pseudobulge") indicates the occurrence of secular evolution processes in the main disc. However, we still lack criteria to effectively categorise bulges, limiting our ability to study their impact on the evolution of the host galaxies and their secularily built structures. In this talk, I will present a recipe to separate inner discs from classical bulges by combining four different parameters from photometric and kinematic analyses. I will also show the results of applying that recipe to a sample of 45 galaxies from the integral-field spectroscopic survey CALIFA. To aid in categorising bulges within these galaxies, we performed 2D image decomposition to determine bulge Sérsic index, bulge-to-disc light ratio, surface brightness and effective radius and we used growth curve analysis to derive a new concentration index, C_{20,50}. We further extracted the stellar kinematics from CALIFA data cubes and analysed the radial velocity dispersion profile. The results of the different approaches are in good agreement and allow a safe classification for approximately 95% of the galaxies. In particular, we found that our new concentration index performs better than the traditionally used C_{50,90} when yielding the nature of bulges. We also found that a combined use of this index and the Kormendy relation gives a robust indication of the physical nature of the bulge.