The 2MASS First Release PSC contains astrometry and photometry in the three survey bandpasses for 20,204,378 sources that were detected in the survey image data. Positions, magnitudes, astrometric and photometric uncertainties, associations with ACT or USNOA optical catalog sources and a number of flags indicating the quality of the photometry are presented for each source.
The PSC also contains point-source processed photometry for virtually
all of the resolved sources found in the Extended Source Catalogs.
The 2MASS First Release XSC contains positions and photometry in the
three survey bandpasses for 73,980 objects found to be resolved relative
to a single point-spread-function during processing. Positions,
magnitudes measured in a wide variety of ways, uncertainties,
associations with several external catalogs and a number of
flags and scores indicating the quality of the measurements,
and the likelihood of "extendedness" are presented for each source.
The 2MASS First Incremental Data Release includes 233,979 FITS images
in the three survey bands constructed from the
scans of 8.5' × 6° long Survey Tiles. 223,806 of the
images are 512×1024 (1"/pix) in size, and a small number, 10,173, from
the ends of scans are 512×698 (1"/pixel).
The J, H and Ks images for each region of sky are
resampled to the same scale and registered to facilitate 3-color
investigations. Positional and photometric calibration data
are carried in the FITS header for each image.
Because of the prohibitive size of image data, currently only ~20:1
lossy-compressed versions of the
Atlas Images are accessible on-line. Compression of the images
was carried out using the
hcompress procedure. It is hoped that it will be possible to serve the
full resolution Atlas Images in the future.
Small cut-outs of the full resolution J, H and Ks Atlas Images
around each of the XSC sources in the First Incremental Data Release are
available on-line.
The image sizes are scaled to the size of the object, ranging from
21´´ × 21´´
for the faintest galaxies (Ks > 13 mag) to the maximum
101´´ × 101´´ for the largest galaxies that 2MASS can
always fully image in a single Tile. For galaxies larger than 101´´,
it is best to use the 2MASS Survey Visualizer, which will display larger
(but lossy compressed) 2MASS Atlas images.
The 2MASS Extended Source Images are 3-dimensional FITS image cubes.
Each cube contains three image planes,
and each plane contains the J, H and Ks 2MASS image data,
respectively.
The near-infrared background emission has been subtracted from each image
plane. Positional and photometric calibration information are included in the
image header.
[Last Updated: 1999 May 6; by R. Cutri]
b. Extended Source Catalog (XSC)
c. Image Products
i. Atlas Images
ii. Extended Source Postage Stamp Images
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