A Morphological Study of M81: Comparison Between GALEX and Spitzer Imaging
We perform a 2D Fourier morphological analysis of GALEX and Spitzer images of M81, an early-type spiral galaxy. We present the Fourier spectra, m-armed spiral densities and synthetic m=2 spirals, which represent very well the entire structure. The Fourier spectra from the FUV and NUV GALEX images are quite similar. In all m=2 spectra, we find spiral arm modulation. For Spitzer images the spiral structure is more tightly-bound for redder filters (5.8 and 8.0 μm). Furthermore, pitch angles for FUV, NUV, 5.8 μm and 8.0 μm are very similar. This last statement strongly suggests a common locus for the origin of UV, 5.8, and 8.0 μm infrared light, and it is an important result pointing in the direction that 5.8 and 8.0 μm light comes from dust illuminated by ultraviolet photons from the very young population.
KeywordsPitch Angle Fourier Spectrum Inverse Fourier Transform Infrared Light Spiral Structure
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