On the Nature of LINERs: A Clue from Keck/LRIS Observations

  • Bae, Hyun-Jin (Center for Galaxy Evolution Research and Department of Astronomy, Yonsei University) ;
  • Yagi, Masafumi (Optical and Infrared Astronomy Division, NAOJ) ;
  • Woo, Jong-Hak (Astronomy Program, Department of Physics and Astronomy, Seoul National University) ;
  • Yoshida, Michitoshi (Hiroshima Astrophysical Science Center, Hiroshima University) ;
  • Yoon, Suk-Jin (Center for Galaxy Evolution Research and Department of Astronomy, Yonsei University)
  • Published : 2011.10.05

Abstract

Low-ionization nuclear emission-line regions (LINERs) have been generally regarded to be powered by active galactic nuclei (AGNs), yet still a number of alternative explanations on the origin of LINER emission are suggested; for example, planetary nebulae nuclei of massive stars, supernovae shocks from death of massive stars, and old stellar populations. Interestingly, a majority of recent star formation early-type galaxies (ETGs) in local universe presents such LINER emission lines. Given that situation, revealing the true nature of LINERs is a crucial step to constrain the evolution path to quiescent ETGs. To resolve the issue, we use Keck/LRIS to obtain spatially resolved spectra on a carefully selected ETG. The ETG SDSS J091628.05+420818.7 at redshift z ~ 0.024 shows modest LINER emission line features without any detection of 21 cm radio continuum nor X-ray emission. We perform a stellar continuum subtraction and measure emission line strengths and their uncertainties for each spectrum from five apertures along the slit with size of 1 arcsecond (~0.5 kpc). We find that extended spatial distributions of four emission lines $H{\alpha}$, $H{\beta}$, [OIII]${\lambda}5007$, and [NII]${\lambda}6583$, and they can be explained by central emission blurring effect. We conclude that the emissions seem to be centrally concentrated, indicating the AGN-nature of LINERs.

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