Ground-based Paα narrow-band imaging of local luminous infrared galaxies. II. Bulge structure and star formation activity

Abstract

We present properties of two types of bulges (classical and pseudo-bulges) in 20 luminous infrared galaxies (LIRGs) observed in the near infrared of the H, K s and 1.91µm narrow-band targeting at the hydrogen Paα emission line by the University of Tokyo Atacama Observatory (TAO) 1.0 m telescope. To classify the two types of bulges, we first perform a two-dimensional bulge-disk decomposition analysis in the K s -band images. The result shows a tentative bimodal distribution of Sérsic indices with a separation at log(n b ) ∼ 0.5, which is consistent with that of classical and normal galaxies. We next measure extents of the distribution of star forming regions in Paα emission line images, normalized with the size of the bulges, and find that they decrease with increasing Sérsic indices. These results suggest that star-forming galaxies with classical bulges have compact star forming regions concentrated within the bulges, while those with pseudobulges have extended star forming regions beyond the bulges, suggesting that there are different formation scenarios at work in classical and pseudobulges.