Revealing the Origins of S0 Galaxies Using Maximum Likelihood Analysis of PNe 2D Kinematics: The Role of Environment

Abstract

Lenticular galaxies lie between ellipticals and spirals on the Hubble sequence, since they have the featureless old stellar populations of elliptical systems, but also contain the disk components associated with spirals. At the moment there is no consensus as to the end of the Hubble sequence to which they are more closely related. Clearly, some process has shut off their star formation; they could be the result of galaxy mergers, much in the manner that star formation is believed to be quenched in elliptical galaxies, or they could be relatively normal spiral galaxies whose star formation has been stopped by some gentler process. The best way of discriminating between these scenarios is offered by the stellar dynamics of S0 galaxy disk. We present a new method based on a maximum likelihood analysis and a bulge-to-disk light decomposition to recover the star kinematic of lenticular galaxies. We test the method on the galaxy NGC 1023.