Physics
Scientific paper
May 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006sptz.prop30471s&link_type=abstract
Spitzer Proposal ID #30471
Physics
Scientific paper
Massive nuclear black holes are now recognized as a fundamental property of almost all local elliptical and spiral galaxies, and low-luminosity AGN play an important role in modifying the observational form of even predominantly star-forming galaxies. The PAH emission bands between 3-18 microns dominate the MIR emission of star-forming galaxies, contributing up to 20% of the total 3-1100 micron infrared luminosity in these features alone. PAHs are uniquely important for modeling high redshift sources in the deep infrared surveys currently being produced by Spitzer's imaging instruments, and are commonly used to probe ongoing star formation, locally, and at high redshift. Although it is commonly assumed that AGN destroy all PAH grains, very recent results from the SINGS survey have uncovered important clues into the power source of galaxies containing low-luminosity AGN, with indications that the gas environments in these nuclei lead to a distinctive and unusual PAH emission spectrum, with marked suppression of the short wavelength PAH bands. These results suggest that the AGN itself may be providing the UV photons necessary to excite this PAH emission. This could have a profound impact on the use of PAH bands as indicators of star-formation rate in systems hosting weak AGN. Or goal is to uncover the nature of PAH emission in galaxies hosting low-luminosity AGN. We propose deep, low-resolution IRS spectral mapping of a small sample of nearby LLAGN to test whether AGN can excite PAH emission, and assess the energetic importance and physical extent of such emission in galaxies with both weak AGN and extended star-formation. We will quantify the difference in the PAH emission spectrum seen in such sources, compared to normal galaxies, and use these results to investigate the predominant power source of low-luminosity AGN. We will also investigate the degree to which AGN-fueled PAH emission could contaminate star-formation rates derived from the absolute strength of the PAH bands.
Armus Lee
Charmandaris Vassilis
Dale Danny
Draine Bruce
Kewley Lisa
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