Multicolor optical imaging of infrared-warm Seyfert galaxies. II. Optical and infrared properties and their correlations

This paper is the second in a series, studying the optical properties of a sample of mid-IR-warm Seyfert galaxies and a control sample of mid-IR-cold galaxies. The present paper is devoted to aperture photometry. We discuss nuclear (within the central 2 kpc) and disk optical properties and their correlations with IR properties. Our results suggest intrinsic differences in the host properties of the Seyfert type 1 and 2 nuclei. We find a transition in the observed optical and IR properties from the cold to the warm Seyfert 2 and Seyfert 1 samples, with a partial overlap between the first two. This is in the sense of (1) increasing nuclear optical luminosities and bluer nuclear colors, (2) decreasing disk optical luminosities and sizes, and (3) increasing 25 mum luminosities, decreasing far-IR excess (L-FIR/L-B) and IR loudness (alpha ((V,25)), alpha ((V,60))), and bluer alpha ((25,60)), and alpha ((12,100)) colors. We interpret these results as indicating larger dust content and disk star formation for Seyfert 2s, while the optical properties of Seyfert Is are mostly dominated by their nuclei. The 25 mum emission of the warm sample is mainly due to the active galactic nucleus (AGN) thermal component, although in Seyfert 2s it is probably further enhanced by disk star formation. The far-IR (60-100 mum) luminosity traces mainly emission at large scales (the host disks for both Seyfert types). In the IR-cold galaxies, the bulk of IR emission at all wavelengths appears to be dominated by dust in their disks.