OAO/ISLE Near-IR Spectroscopy of IRAS Galaxies

TL;DR

This study uses near-infrared spectroscopy to analyze nine IRAS galaxies, identifying nuclear activity types and unusual phenomena, demonstrating ISLE's effectiveness in exploring infrared galaxy features.

Contribution

First application of ISLE spectrograph to IRAS galaxies revealing nuclear activity and unique spectral features in a small sample.

Findings

NGC 1266 likely hosts a LINER nucleus

NGC 2633 and NGC 2903 possibly contain AGNs

Detected unusual spectral features like large [Fe II] line widths

Abstract

We present the results of the near-infrared (IR) spectroscopy of nine IRAS galaxies (NGC 1266, NGC 1320, NGC 2633, NGC 2903, NGC 3034, Mrk 33, NGC 7331, NGC 7625, NGC 7714) with the ISLE imager and spectrograph mounted on the Okayama Astrophysical Observatory 1.88 m telescope. [Fe II] 1.257 um and Pa beta emission lines were observed for the whole sample while H2 2.121 um and Br gamma lines were additionally obtained for two sources, whose flux ratios are used as a diagnostic tool of dominant energy sources of the galaxies. We find that the nucleus of NGC 1266 is most likely a low ionization nuclear emission-line region (LINER), while NGC 2633 and NGC 2903 possibly harbor active galactic nuclei (AGNs). No AGN or LINER signal is found for other objects. In addition, we find the spectral features which is indicative of some unusual phenomena occurring in the galaxies, such as the large [Fe II] line widths compared to the local escape velocity in NGC 1266. The present work shows the potential ability of the ISLE to shed new light on the nature of infrared galaxies, either through a statistical survey of galaxies or an exploration of spectral features found in individual objects.