Clues to the Formation of Lenticular Galaxies Using Spectroscopic Bulge-Disk Decomposition

Lenticular galaxies have long been thought of as evolved spirals, but the processes involved to quench the star formation are still unclear. By studying the individual star formation histories of the bulges and disks of lenticulars, it is possible to look for clues to the processes that triggered their transformation from spirals. To accomplish this feat, we present a new method for spectroscopic bulge-disk decomposition, in which a long-slit spectrum is decomposed into two one-dimensional spectra representing purely the bulge and disk light. We present preliminary results from applying this method to lenticular galaxies in the Virgo and Fornax Clusters, in which we show that the most recent star formation activity in these galaxies occurred within the bulges. We also find that the bulges are in general more Fe-enriched than the disks of the same galaxy, and that this enrichment grows stronger as the age of the bulge becomes younger. These results point towards a scenario where the star formation in the disks of spiral galaxies are quenched, followed by a burst of star formation in the central regions from the gas that has been funnelled inwards through the disk.
Comment: 4 pages, 2 figures, To appear in the conference proceedings of The Structure and Dynamics of Disk Galaxies, M.S. Seigar and P. Treuthardt, eds