J/MNRAS/481/5580 The formation sequence of S0 galaxies (Fraser-McKelvie+, 2018) ================================================================================ SDSS-IV MaNGA: the formation sequence of S0 galaxies. Fraser-McKelvie A., Aragon-Salamanca A., Merrifield M., Tabor M., Bernardi M., Drory N., Parikh T., Argudo-Fernandez M. =2018MNRAS.481.5580F (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Galaxies ; Morphology ; Abundances Keywords: galaxies: elliptical and lenticular - galaxies: evolution - galaxies: general - galaxies: stellar content Abstract: Gas stripping of spiral galaxies or mergers are thought to be the formation mechanisms of lenticular galaxies. In order to determine the conditions in which each scenario dominates, we derive stellar populations of both the bulge and disc regions of 279 lenticular galaxies in the MaNGA survey. We find a clear bimodality in stellar age and metallicity within the population of S0s and this is strongly correlated with stellar mass. Old and metal-rich bulges and discs belong to massive galaxies, and young and metal-poor bulges and discs are hosted by low-mass galaxies. From this we conclude that the bulges and discs are co-evolving. When the bulge and disc stellar ages are compared, we find that the bulge is almost always older than the disc for massive galaxies (M_*_>10^10^M_{sun}_). The opposite is true for lower mass galaxies. We conclude that we see two separate populations of lenticular galaxies. The old, massive, and metal-rich population possess bulges that are predominantly older than their discs, which we speculate may have been caused by morphological or inside-out quenching. In contrast, the less massive and more metal-poor population have bulges with more recent star formation than their discs. We postulate they may be undergoing bulge rejuvenation (or disc fading), or compaction. Environment does not play a distinct role in the properties of either population. Our findings give weight to the notion that while the faded spiral scenario likely formed low-mass S0s, other processes, such as mergers, may be responsible for high-mass S0s. Description: 279 lenticular galaxies were selected from the MaNGA survey's MaNGA product launch 5 (MPL-5), consisting of 2778 galaxy data cubes observed from March 2014 to May 2016. The MaNGA galaxy survey is an IFS survey that aims to observe ~10000 galaxies by 2020 (Bundy et al. 2015ApJ...798....7B; Drory et al. 2015AJ....149...77D) and is a project of SDSS-IV (Blanton et al. 2017AJ....154...28B) using the 2.5m telescope at the Apache Point Observatory (Gunn et al. 2006AJ....131.2332G) and BOSS spectrographs (Smee et al. 2013AJ....146...32S). All galaxy observations have wavelength coverage of ~3500-10000{AA}, spectral resolution R ~2000 (which gives an instrumental resolution of ~60km/s), and an effective spatial resolution of 2.5arcsec (full width at half-maximum) after combining dithered observations; the sample lies within the redshift range 0.01