Multicolor optical imaging of infrared-warm Seyfert galaxies. IV. Surface photometry: Color distributions

This paper is the fourth in a series studying the optical properties of a sample of mid-infrared warm Seyfert galaxies and of a control sample of mid-infrared cold galaxies. The present paper is devoted to the analysis of the color distributions characterizing the hosts. The warm Seyfert 1 and 2 galaxies show opposite color gradients and their color profiles are depicting age and dust effects within single-burst, solar-metallicity models. In particular, we find ample evidence for the occurrence of strong star formation in the Seyfert 2 disks: their color and emission line two-dimensional maps suggest dust extinction associated with ongoing star formation in spiral and tidal features; their color profiles show starbursts of 0.5-1 Gyr or younger, superposed on the older underlying galaxy population. Most of these properties are shared with the cold galaxies, while the warm Seyfert 1 galaxies show mostly older stellar populations and, in only a few cases, evidence for circumnuclear star formation.