Formation of S0s in extreme environments I: clues from kinematics and
  stellar populations
  Despite numerous efforts, it is still unclear whether lenticular galaxies
(S0s) evolve from spirals whose star formation was suppressed, or formed trough
mergers or disk instabilities. In this paper we present a pilot study of 21 S0
galaxies in extreme environments (field and cluster), and compare their
spatially-resolved kinematics and global stellar populations. Our aim is to
identify whether there are different mechanisms that form S0s in different
environments. Our results show that the kinematics of S0 galaxies in field and
cluster are, indeed, different. Lenticulars in the cluster are more
rotationally supported, suggesting that they are formed through processes that
involve the rapid consumption or removal of gas (e.g. starvation, ram pressure
stripping). In contrast, S0s in the field are more pressure supported,
suggesting that minor mergers served mostly to shape their kinematic
properties. These results are independent of total mass, luminosity, or
disk-to-bulge ratio. On the other hand, the mass-weighted age, metallicity, and
star formation time-scale of the galaxies correlate more with mass than with
environment, in agreement with known relations from previous work such as the
one between mass and metallicity. Overall, our results re-enforce the idea that
there are multiple mechanisms that produce S0s, and that both mass $and$
environment play key roles. A larger sample is highly desirable to confirm or
refute the results and the interpretation of this pilot study.
