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Mid-Infrared Spectroscopy of High Redshift Submillimeter Galaxies: First Results

Karín Menéndez-Delmestre·Andrew W. Blain·Dave M. Alexander·Ian Smail·Lee Armus·Scott C. Chapman·Dave Frayer·Rob J. Ivison·Harry Teplitz
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Abstract

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.

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Karín Menéndez-Delmestre, Andrew W. Blain, Dave M. Alexander, Ian Smail, Lee Armus, Scott C. Chapman, Dave Frayer, Rob J. Ivison, Harry Teplitz. 2006-12-24. Mid-Infrared Spectroscopy of High Redshift Submillimeter Galaxies: First Results. https://doi.org/10.1086/512038

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