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

## TL;DR

This study investigates the structural differences and star formation activity in classical and pseudo-bulges of 20 luminous infrared galaxies using near-infrared imaging and Paα emission line analysis.

## Contribution

It provides a detailed classification of bulge types in LIRGs and links bulge structure to star formation region distribution, revealing different formation processes.

## Key findings

- Classical bulges have compact star-forming regions within the bulge.
- Pseudo-bulges exhibit extended star-forming regions beyond the bulge.
- A bimodal distribution of Sersic indices supports bulge classification.

## 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 1.91$\mu$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.