Instructions
2MASS Extended Source Catalog (XSC) sources, which include galaxies, HII regions, nebulae, etc., have associated non-lossy-compressed 'postage-stamp' images available. These images cover small areas centered on and encompassing each extended source. The image size is scaled to the size of the object, ranging from 21"X21" for the faintest galaxies (Ks > 13th mag) to the maximum 301"X301" for the largest galaxies that the 2MASS pipeline can fully image (e.g., NGC 7479). For galaxies larger than 2 or 3', the source probably belongs to the 2MASS Large Galaxy Atlas, which is fully described in the AJ paper Jarrett et al. 2003, and accessible through this IRSA service.
The 2MASS Extended Source 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.
Additional information about 2MASS extended sources and the extended source processor can be found here: 2MASS Galaxy Catalog and the 2MASS Large Galaxy Atlas.
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