We present mid-infrared spectra of 5 submillimeter galaxies at z=0.65-2.38 taken with the Spitzer Space Telescope. Four of these sources, at z<1.5, have strong PAH features and their composite spectrum is well fitted by an M82-like spectrum with an additional power-law component consistent with that expected from AGN activity. Based on a comparison of the 7.7-micron PAH equivalent width and the PAH-to-infrared luminosity ratio of these galaxies with local templates, we conclude that these galaxies host both star-formation and AGN activity, with star-formation dominating the bolometric luminosity. The source at z=2.38 displays a Mrk231-type broad feature at restframe ~8 micron that does not conform to the typical 7.7/8.6 micron PAH complex in starburst galaxies, suggesting a more substantial AGN contribution.
CITATION STYLE
Menéndez-Delmestre, K., Blain, A. W., Alexander, D. M., Smail, I., Armus, L., Chapman, S. C., … Teplitz, H. I. (2007). Mid-Infrared Spectroscopy of High-Redshift Submillimeter Galaxies: First Results. The Astrophysical Journal, 655(2), L65–L68. https://doi.org/10.1086/512038
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