Energy Diagnoses of Nine Infrared Luminous Galaxies Based on 3--4 Micron Spectra

Masatoshi Imanishi; C. C. Dudley

doi:10.1086/317863

paper

Energy Diagnoses of Nine Infrared Luminous Galaxies Based on 3--4 Micron Spectra

arXiv:astro-ph/0008092 · doi:10.1086/317863

Abstract

The energy sources of nine infrared luminous galaxies (IRLGs) are diagnosed based on their ground-based 3--4 $μ$ m spectra. Both the equivalent width of the 3.3 $μ$ m polycyclic aromatic hydrocarbon (PAH) emission feature and the 3.3 $μ$ m PAH to far-infrared luminosity ratio ( $L_{3.3} / L_{FIR}$ ) are analyzed. Assuming nuclear compact starburst activity in these sources produces the 3.3 $μ$ m PAH emission as strongly as that in starburst galaxies with lower far-infrared luminosities, the followings results are found: For six IRLGs, both the observed equivalent widths and the $L_{3.3} / L_{FIR}$ ratios are too small to explain the bulk of their far-infrared luminosities by compact starburst activity, indicating that active galactic nucleus (AGN) activity is a dominant energy source. For the other three IRLGs, while the 3.3 $μ$ m PAH equivalent widths are within the range of starburst galaxies, the $L_{3.3} / L_{FIR}$ ratios after correction for screen dust extinction are a factor of $\sim$ 3 smaller. The uncertainty in the dust extinction correction factor and in the scatter of the intrinsic $L_{3.3} / L_{FIR}$ ratios for starburst galaxies do not allow a determination of the ultimate energy sources for these three IRLGs.

29 pages, 2 figures, Accepted for publication in ApJ

Energy Diagnoses of Nine Infrared Luminous Galaxies Based on 3--4 Micron Spectra

Abstract

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