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| Paper: |
Spiral Structure Observed in Near-Infrared |
| Volume: |
275, Disks of Galaxies: Kinematics, Dynamics and Perturbations |
| Page: |
305 |
| Authors: |
Grosbøl, P.; Pompei, E.; Patsis, P. A. |
| Abstract: |
Near-infrared observations of the spiral pattern in galaxies reveal the underlying density perturbations in the disks much better than maps in visual bands although some population effects are still present. A preliminary analysis of the spiral structure in 53 nearby spiral galaxies observed in the K band with SOFI/NTT is presented including the distribution of arm amplitudes and pitch angles. The frequency of bars in a subsample of 30 galaxies classified as non-barred in the visual was studied. In the K band, ~75% of these galaxies showed bars or oval distortions with a relative amplitude larger than 2% and a length in excess of 5 arcsec. This suggests that the majority (i.e. ~95%) of all spirals may have some kind of bar perturbation although in many cases weak. The histogram of relative bar amplitudes suggested a bi-modal distribution. Most galaxies observed in K have a grand design, two-armed, symmetric spiral pattern in their inner parts which often breakup into tighter winded, multiple arms further out. The distribution of mean amplitudes of the main two-armed spiral as function of pitch angle shows a lack of strong tight spirals. This may be caused by non-linear effects occurring for spiral with relative radial force perturbations larger than 5%. |
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