Narrow Line Seyfert 1 Galaxies and the Evolution of Galaxies and Active Galaxies

Narrow Line Seyfert 1 galaxies (NLS1s) are intriguing due to their continuum as well as emission line properties. The observed peculiar properties of the NLS1s are believed to be due to accretion rate close to Eddington limit. As a consequence, for a given luminosity, NLS1s have smaller black hole (BH) masses compared to normal Seyfert galaxies. Here we argue that NLS1s might be Seyfert galaxies in their early stage of evolution and as such may be low redshift, low luminosity analogues of high redshift quasars. We propose that NLS1s may reside in rejuvenated, gas rich galaxies. The also argue in favor of collisional ionization for production of FeII in active galactic nuclei (AGN).