The Carnegie-Irvine Galaxy Survey. VI. Quantifying Spiral Structure

Understand

The Carnegie-Irvine Galaxy Survey provides high-quality broad-band optical images of a large sample of nearby galaxies for detailed study of their structure.

• To probe the physical nature and possible cosmological evolution of spiral arms, a common feature of many disk galaxies, it is important to quantify their main characteristics.
• We describe robust methods to measure the number of arms, their mean strength, length, and pitch angle.
• The arm strength depends only weakly on the adopted radii over which it is measured, and it is stronger in bluer bands than redder bands.