Ground-based Pa$α$ Narrow-band Imaging of Local Luminous Infrared Galaxies II: Bulge Structure And Star Formation Activity

Ken Tateuchi, Kentaro Motohara, Masahiro Konishi, Hidenori Takahashi, Yutaro Kitagawa, Natsuko Kato, Soya Todo, Shinya Komugi, Ryou Ohsawa, Mamoru Doi, Yuzuru Yoshii

Published 2019-03-25Version 1

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 1.91$\mu$m narrow-band targeting at the hydrogen Pa$\alpha$ 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 $K_\mathrm{s}$-band images. The result shows a tentative bimodal distribution of S\'ersic indices with a separation at $\log(n_b)\sim0.5$, which is consistent with that of classical and normal galaxies. We next measure extents of the distribution of star forming regions in Pa$\alpha$ emission line images, normalized with the size of the bulges, and find that they decrease with increasing S\'ersic 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.