Spitzer View of Four Low Surface Brightness Giant Galaxies: Malin 1, UGC 6614, UGC 6879, UGC 9024
Abstract
We present $Spitzer$ IRAC and MIPS imaging of four low surface brightness (LSB) galaxies: Malin 1, UGC 6614, UGC 6879, UGC 9024. Our study shows that the gigantic disks such as Malin 1 and UGC 9024 appear just like a point source in the IRAC and MIPS images. Their morphological features suggest that IR emission is concentrated in central few kpc in these disks. For Malin 1, however, far-IR emission from the rest of the disk is too faint to be detected by the IRAC and MIPS implying presence of cold cirrus components in this galaxy emitting mostly in the $\geq 200$ micron. UGC 6614 and UGC 6894, on the other hand have, substantial amount of dust with various radiation intensity: hot, warm and cool. The most striking outcome of our study is that these LSB galaxies show enhance PAH emission. The existence of diffuse PAH emission indicates that the ISM in LSB disks have significant amount of carbon enrichment over time and that radiation field intensity must have been significantly weak to be able to reduce the strength of diffuse emission. We have constructed IR spectral energy distribution (SED) for these LSB galaxies. Though we still lack information beyond $\sim$200 micron the trend seen in our preliminary study suggests that cirrus emission heated by the interstellar radiation field must play a significant role at least in Malin type disks. However, at present using SST alone we are unable to probe the cold dust components.
- Publication:
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American Astronomical Society Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AAS...209.1501R