Index Key to Source Characterization Table

Name & Position

Orientation & Shape

Additional information:

Image Parameters

Small cut-outs of the non-compressed J, H and Ks Atlas Images around each of the XSC sources in the AllSky Release are available on-line. The Postage Stamp Image sizes are scaled to the size of the object, ranging from 21´´ × 21´´ for the faintest galaxies (Ks > 13 mag) to a maximum of 301´´ × 301´´. For galaxies larger than 301´´, it is best to use the 2MASS Large Galaxy ATLAS, which consists of full mosaiced images and photometry of the largest galaxies in the sky.

The 2MASS Extended Source Postage Stamp Images are 6-dimensional FITS image cubes. Each plane contains the J, H and Ks 2MASS image data, respectively, with stars removed from the final 3 planes. The near-infrared background emission has been subtracted from each image plane. Positional and photometric calibration information are included in the image header. An example header is given here.

Isophotal Photometry

The isophotal measurements are set at the 20 mag per arcsec2 isophote at Ks (corresponding to roughly 1-sigma of the background RMS), using both circular and elliptically shape-fit apertures.

Additional information:

7" Radius Circular Aperture Photometry

Kron Photometry

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"Total" Photometry

The "total" aperture consists of the isophotal aperture plus the integration of the surface brightness profile that extends from the isophotal aperture out to ~4 disk scale lengths (i.e., well below the 1-sigma RMS noise level). With this curve of growth technique, an additional 10-20% of the galaxy flux is recovered (depending on the type of galaxy).

Additional information:

Half-Light "Effective" Size, Surface Brightness & Concentration Index

Additional information:

Profile Fit Parameters

Additional information: