Basic Measurements

For consistency with the 2MASS extended source catalog, the Large Galaxy Atlas includes basic measurements, including size, orientation and photometry. The 2MASS processor, GALWORKS, has been modified to operate on these large images, a few of which are nearly a degree in size (e.g., M33). One critical modification is to use aprior knowledge of the approximate orientation of the galaxy, axis ratio and position angle, as given in the RC3 or UGC or 2MASS. These parameters are used as initial (iteration zero) guesses for the isophotal surface (ellipse) fit.

Processing & Measurements

star removal
3-sigma and 20 mag/arcsec^2 isophotes
elliptical orientation (axis ratio & position angle)
surface brightness
half-light radii
concentration index
photometry
fixed circular
isophotal
Kron
total

Links

Below are a set of links to the relevant 2MASS Extended Source Processor pages that explain Kron, Total and other photometric measures.

• 2MASS Extended Source Catalog
  
• Kron Photometry
  
• Radial Profile Fitting and Total Mags