Paper: astro-ph/0512404
Date: Thu, 15 Dec 2005 16:47:10 GMT (47kb)

Title: The PAH Emission Deficit In Low-Metallicity Galaxies - A Spitzer View

Authors: B. O'Halloran, S. Satyapal and R. P. Dudik

Comments: 19 pages, 4 figures, accepted for publication in ApJ
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Archival observations of 18 starburst galaxies that span a wide range in
metallicity reveal for the first time a correlation between the ratio of
emission line fluxes of [FeII] at 26 microns and [NeII] at 12.8 microns and the
7.7 micron PAH strength, with the [FeII]/[NeII] flux ratio decreasing with
increasing PAH strength. We also find a strong correlation between the
[FeII]/[NeII] flux ratio and the host galaxy metallicity, with the flux ratio
decreasing with increasing metallicity.

Since [FeII] emission has been linked primarily to supernova shocks, we
attribute the high [FeII]/[NeII] ratios in low-metallicity galaxies to enhanced
supernova activity. We consider this to be a dominant mechanism for PAH
destruction, rather than grain destruction in photoionized regions surrounding
young massive stars. We also consider whether the extreme youth of the
low-metallicity galaxies is responsible for the lack of PAH emission.

\\ ( http://arXiv.org/abs/astro-ph/0512404 , 47kb)