2. NIR Data
The data used to construct the Large Galaxy Atlas are derived from the 2MASS images and source catalogs. 2MASS surveyed the sky with 8.5 arcmin * 6° tiles or "scans" (Skrutskie et al 1997), forming 23 separate images per tile per band of size 512*1024 pixels with resampled 1arcsec pixels. These images, 8.5*17 arcmin in angular size, are also known as "coadds" since they are comprised of ~6 optimally dithered samples per pixel. This movie shows several consecutive frames from a scan through the globular cluster M92.
The effective beam or PSF FWHM is ~2 to 3 arcsec, depending on the atmospheric seeing. These coadd images are the basic data product from which galaxies and extended sources are detected, characterized and extracted into the 2MASS database (Jarrett et al 2000). The typical 1-sigma background noise is 21.4, 20.6, and 20.0 mag arcsec-2 for J, H and Ks, respectively. The coadd images include a photometric zero-point calibration that is accurate to 2-3% and an astrometric solution that is accurate to <0.2 arcsec (Cutri et al 2000). The large mosaics presented here are constructed from these individual coadd images.