paper

8--13 micron spectroscopy of luminous and ultraluminous infrared galaxies

arXiv:astro-ph/9903250 · doi:10.1046/j.1365-8711.1999.02631.x

Abstract

New moderate-resolution mid-infrared spectroscopy at 10 micron of 27 infrared galaxies is presented. The galaxies have been chosen from three 60 micron selected and one 12 micron selected complete flux-limited catalogs of galaxies; 17 of these sources have L_IR(8--1000 micron) >= 5 times 10^11 L_sun. A high-resolution spectrum of the source Arp 299B1 is also presented. Combining these new results with previously published results, a nearly complete 60 micron selected flux limited subsample, with L_IR(8--1000 micron) >= 1.6 times 10^11 L_sun of 25 galaxies is defined. Within this subsample, it is found that the dominant power source of infrared galaxies in the luminosity range 1.6 times 10^11 < L_IR(8--1000 micron) < 10^{12} L_sun is massive star formation based on the clear presence of the 11.3 micron aromatic hydrocarbon emission feature in the majority of the spectra. Three of the five ultraluminous infrared galaxies (L_IR(8--1000 micron) >= 10^12 L_sun) within this subsample show evidence that an active galactic nucleus provides an energetically important power source based on the detection of silicate absorption in their mid-infrared spectra. The physical basis of a possible anti-correlation between the 11.3 micron feature equivalent width and infrared light to molecular gas mass ratios is discussed.

10 pages with 9 pages of postscript tables and 13 pages of postscript figures (6 tables and 4 figures). To appear in MNRAS

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