Ground-based Pa$α$ Narrow-band Imaging of Local Luminous Infrared Galaxies I: Star Formation Rates and Surface Densities

Ken Tateuchi, Masahiro Konishi, Kentaro Motohara, Hidenori Takahashi, Natsuko Mitani Kato, Yutaro Kitagawa, Soya Todo, Koji Toshikawa, Shigeyuki Sako, Yuka K. Uchimoto, Ryou Ohsawa, Kentaro Asano, Yoshifusa Ita, Takafumi Kamizuka, Shinya Komugi, Shintaro Koshida, Sho Manabe, Tomohiko Nakamura, Asami Nakashima, Kazushi Okada, Toshinobu Takagi, Toshihiko Tanabé, Mizuho Uchiyama, Tsutomu Aoki, Mamoru Doi, Toshihiro Handa, Kimiaki Kawara, Kotaro Kohno, Takeo Minezaki, Takashi Miyata, Tomoki Morokuma, Takeo Soyano, Yoichi Tamura, Masuo Tanaka, Ken'ichi Tarusawa, Yuzuru Yoshii

Published 2014-12-12Version 1

Luminous infrared galaxies (LIRGs) are enshrouded by a large amount of dust, produced by their active star formation, and it is difficult to measure their activity in the optical wavelength. We have carried out Pa$\alpha$ narrow-band imaging observations of 38 nearby star-forming galaxies including 33 LIRGs listed in $IRAS$ RBGS catalog with the Atacama Near InfraRed camera (ANIR) on the University of Tokyo Atacama Observatory (TAO) 1.0 m telescope (miniTAO). Star formation rates (SFRs) estimated from the Pa$\alpha$ fluxes, corrected for dust extinction using the Balmer Decrement Method (typically $A_V$ $\sim$ 4.3 mag), show a good correlation with those from the bolometric infrared luminosity of $IRAS$ data within a scatter of 0.27 dex. This suggests that the correction of dust extinction for Pa$\alpha$ flux is sufficient in our sample. We measure the physical sizes and the surface density of infrared luminosities ($\Sigma_{L(\mathrm{IR})}$) and $SFR$ ($\Sigma_{SFR}$) of star-forming region for individual galaxies, and find that most of the galaxies follow a sequence of local ultra luminous or luminous infrared galaxies (U/LIRGs) on the $L(\mathrm{IR})$-$\Sigma_{L(\mathrm{IR})}$ and $SFR$-$\Sigma_{SFR}$ plane. We confirm that a transition of the sequence from normal galaxies to U/LIRGs is seen at $L(\mathrm{IR})=8\times10^{10}$ $L_{\odot}$. Also, we find that there is a large scatter in physical size, different from those of normal galaxies or ULIRGs. Considering the fact that most of U/LIRGs are merging or interacting galaxies, this scatter may be caused by strong external factors or differences of their merging stage.