The 2MASS Second Incremental Release PSC contains astrometry and photometry in the three survey bandpasses for 162,213,354 sources. 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 Second Incremental Release XSC contains positions and photometry
in the
three survey bandpasses for 585,056 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 Second Incremental Data Release includes 1,897,017 FITS images
in the three survey bands constructed from the
scans of 8.5´ × 6° long Survey Tiles. 1,814,538 of the
images are 512×1024 (1"/pix) in size. The remaining 82,479 images
lie at the ends of Survey scans and 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.
20:1 lossy-compressed versions of the Atlas Images, known as the
"Quicklook" Images, are also available, and are suitable for many
applications such as finding charts and visual inspection of fields.
Compression of the "Quicklook" images was carried out using the
hcompress procedure. Because of the losses during compression,
the "Quicklook" images should not be used for quantitative brightness
measurements.
ii. Extended Source Postage Stamp Images
Small cut-outs of the uncompressed J, H and Ks Atlas Images
around each of the XSC sources in the Second Incremental 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 a maximum of
101´´ × 101´´.
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,
containing three image planes.
Each plane contains the J, H and Ks 2MASS image data,
respectively.
The near-infrared sky background emission has been subtracted from each image
plane. Positional and photometric calibration information are included in the
image header.
[Last Updated: 2001 January 31; by R. Cutri]
b. Extended Source Catalog (XSC)
c. Image Products
i. Atlas Images
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