Exploring accretion and jet in Narrow-Line Seyfert 1 galaxies

Powerful radio jet launched by the active galactic nuclei (AGN) is one of the most important form of AGN feedback regulating the galaxy evolution. Only ~15% of all AGN are radio=loud with powerful relativistic radio jet, while the rest are radio-quiet with faint or no radio jet. How is the jet launched in AGN? What's the role of accretion process in jet formation? These are still open questions. Here I explore these questions using an exceptional sub-group of active galaxies, the so-called Narrow-line Seyfert 1 (NLS1) galaxies, which are in a phase of strong accretion activity and rapidly growing their supermassive blackholes. I'll introduce our work mainly on three topics: relativistic jet launched in gamma-ray emitting radio-loud NLS1 galaxies; the radio-X-ray relation in radio-quiet NLS1 galaxies; the parsec scale radio emission in highest Eddington ratio NLS1 galaxies.