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arXiv · 0908.4544

quantitative determination of the AGN content in local ULIRGs through L-band spectroscopy

G. Risaliti·M. Imanishi·E. Sani
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Abstract

We present a quantitative estimate of the relative AGN/starburst content in a sample of 59 nearby (z<0.15) infrared bright ULIRGs taken from the 1 Jy sample, based on infrared L-band (3-4 micron) spectra. By using diagnostic diagrams and a simple deconvolution model, we show that at least 60% of local ULIRGs contain an active nucleus, but the AGN contribution to the bolometric luminosity is relevant only in ~15-20% of the sources. Overall, ULIRGs appear to be powered by the starburst process, responsible for >85% of the observed infrared luminosity. The subsample of sources optically classified as LINERs (31 objects) shows a similar AGN/starburst distribution as the whole sample, indicating a composite nature for this class of objects. We also show that a few ULIRGs, optically classified as starbursts, have L-band spectral features suggesting the presence of a buried AGN.

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G. Risaliti, M. Imanishi, E. Sani. 2009-08-31. quantitative determination of the AGN content in local ULIRGs through L-band spectroscopy. https://doi.org/10.1111/j.1365-2966.2009.15622.x

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