The Scan Information Table contains parameters describing and derived from each observation of the 59,731 Tiles (see III.2a) that comprise the All-Sky Data Release. These parameters include Tile identification, and location on the sky, observatory and instrument specifications, measured environmental and derived sky conditions, and statistics and quality information regarding the scan. The Scan Information Table Format page describes each column in the table, and provides links to more detailed descriptions of the parameters when they are available.
Each entry in the Scan Information Table contains a unique index, scan_key. Entries in the Point and Extended Source Catalogs are cross-referenced to the Scan Information Table listings via the scan_key value.
The Scan Information Table will be accessible using the IRSA/GATOR online query engine beginning on April 22, 2003. It is also available in database-readable ascii form via download from anonymous ftp and on the All-Sky Release DVD-ROM (I.4).
Table 1 - Scan Information Table Format
The Atlas Image Information Table contains metadata and derived information
for each 1,373,813 registerd sets of J, H and Ks Atlas Images
(see II.4) in the All-Sky Data Release.
The columns in this table provide descriptions, locations
and calibration information for each image, as well as
parameters such as seeing and background derived from measurements of
the images during data processing.
The Atlas Image Information
Table Format page describes each column in the table, and provides links to
sections of the Explanatory Supplement that contain detailed descriptions
of the parameters when they are available.
Each entry in the Atlas Image Information Table contains a unique index,
coadd_key. Entries in the Point and Extended Source Catalogs
are cross-referenced to the Atlas Image Information Table listings via the
coadd_key value.
The Atlas Image Information Table will be accessible using the
IRSA/GATOR online
query engine, and is also available in
database-readable form via anonymous ftp and on the All-Sky Release
DVD-ROM.
Table 2 - Atlas Image Information Table Format NOT YET AVAILABLE
The All-Sky Release PSC contains 15,964 sources that are positionally
associated with the predicted positions of known asteroids.
These sources were identified during scan data processing
by determining which known asteroids were within the boundaries of
a 2MASS Tile when it was scanned, and searching for positional correlations
between the predicted positions of those objects and extracted 2MASS
sources. Section
IV.9 contains a description
of this procedure, the asteroid ephemerides
and position prediction methods used. Association between
predicted asteroid and 2MASS source positions does not imply
an identification, particularly at low galactic latitude where chance
association with background stars is likely.
The Known
Asteroid Association List gives for each asteroid that
was associated with a source in the All-Sky Release PSC object
identification, orbital data used to predict positions and visual
brightness, and abridged PSC data for the source.
Cross-reference to the full PSC source entry (and in some cases
the XSC) is made via the
pts_key and
ext_key columns.
The description of each column
is provided in the table header. Note that the names of
some columns in the table header have been abbreviated from their full
PSC names to save space. The full PSC column names are given in the
definitions in these cases.
A number of asteroids have multiple entries in this table because
they were detected more than once during the Survey due to their motion,
and appear in the PSC multiple times.
For example, (52) Europa appears in the PSC five times, its position
having been scanned on 1998 September 19 and 25 UT, twice on
2000 February 25 UT, and once again on 2000 March 14 UT.
Table 3 - Known Asteroid Association List
The All-Sky Release PSC contains 46 sources that are positionally
associated with the predicted positions of known comets. Eight of
these were resolved 2MASS detections and are thus also included
in the All-Sky Release XSC.
These sources were identified during scan data processing
by determining which known comets were within the boundaries of
a 2MASS Tile when it was scanned, and searching for positional correlations
between the predicted positions of those objects and extracted 2MASS
sources. Users are encouraged to read Section
IV.9 for a detailed description
of this procedure, for details concerning comet ephemerides
and position prediction. Association between
predicted comet and 2MASS source positions does not imply
an identification, particularly at low galactic latitude where chance
association with background stars is likely.
The Known
Comet Association List gives for each comet that
was associated with a source in the All-Sky Release PSC object
identification, orbital data used to predict positions and visual
brightness, and abridged PSC data for the source.
Cross-reference to the full PSC and XSC source entries
is made via the
pts_key and
ext_key columns.
The description of each column
is provided in the table header. Note that the names of
some columns in the table header have been abbreviated from their full
PSC names to save space. The full PSC column names are given in the
definitions in these cases.
Several comets appear in this table more than once because
they were detected more than once during the Survey due to their motion,
and appear in the PSC and/or XSC multiple times.
Table 4 - Known Comet Association List
The All-Sky Release PSC contains detections of Uranus, Neptune and Pluto
and 14 satellites of these planets and Jupiter.
Jupiter was also scanned during Survey operations, but it was so bright
that its glare effectively washed out the scan data that covered it.
That region of the sky was reobserved at a later time after Jupiter had
moved on, and Jupiter's scan was not included in the All Sky Release.
Planetary detections were identified during scan data processing
by determining which known planets were within the boundaries of
a 2MASS Tile when it was scanned, and searching for positional correlations
between the predicted positions of those objects and extracted 2MASS
sources. Planetary satellite associations were made manually after
pipeline data processing was complete, using a similar procedure.
Users are encouraged to read
Section IV.9 for a detailed description
of these procedures, for details concerning planet ephemerides
and position prediction, and for important caveats concerning the
associations.
The Known
Planet and Satellite Association List gives for each planet and satellite
was associated with a source in the All-Sky Release PSC object
identification, orbital data used to predict positions and visual
brightness, and abridged PSC data for the source.
Cross-reference to the full PSC source entry
is also provided via the
pts_key columns.
The description of each column
is provided in the table header. Note that the names of
some columns in the table header have been abbreviated from their full
PSC names to save space. The full PSC column names are given in the
definitions in these cases.
Uranus and several of its satellites appear twice in this table
because their positions were scanned twice at different times during
the Survey, and they have multiple entries in the PSC. However,
Uranus is resolved so it
was not reliably extracted each time it was observed.
Table 5 - Known Planet and Satellite Association List
The effective spatial coverage of the XSC was limited by the presence of
foreground stars. Bright stars mask out regions in large halos and
covering long diffraction spike around their locations. The masked area
was computed during extended source processing (see
IV.5), and the fractional coverage for each
2MASS Atlas Image in each band was derived. The fractional coverage
per image was used to generate large scale effective coverage maps
for the XSC. These coverage maps are available in GIF previews
and FITS formats in the link above.
Every effort has been made to remove
unreliable sources from the Catalogs, and to flag sources that might
be contaminated by image artifacts.
However, the sheer volume of the 2MASS image and source data products make
it impossible to guarantee their perfection. For example, the target
reliability for sources in unconfused regions of the sky in the
2MASS Catalogs is 99.95% (PSC) and 99% (XSC for |b|>20°).
Even at these strict limits, there may be >170,000 unreliable point sources
and >12,000 unreliable extended sources. A summary of the types
of unreliable sources that are known to have persisted into the Catalogs
are given in Sections I.6b.vi
and I.6c.
The All-Sky Release PSC and XSC are static, so unreliable sources
identified after they are released will not be removed.
Catalog sources that are identified to be spurious or contaminated
by artifacts
will be tabulated in the PSC and XSC Anomaly Lists.
These lists will be updated periodically. There are two
classes of anomaly lists for the PSC and XSC. The first contains
lists of catalog entries that have been confirmed (usually through
visual inspection of the images) to be spurious extractions, and not
detections of astrophysical sources. The second contains catalog
entries that are likely detections of real sources, but that
measurements corrupted by confusion, artifacts and/or transient events,
and are not so indicated in the cc_flg in the Catalog entries.
These lists will be updated periodically as new instances of anomalies
are found.
Each entry in the anomaly tables contains basic catalog source
identification information and a brief description of the nature
of the anomaly. The columns in the table are as follows:
Table 6 - PSC Anomaly List - Spurious Sources
Table 7 - PSC Anomaly List - Contaminated Sources
XSC Anomaly Lists - Please see I.6.c for
tables of artifacts, false extended sources and contaminated sources in
the XSC.
The 2MASS All-Sky Catalog Tables are available in a bulk
distribution on DVD-ROM. These disks do not contain
the Image Atlas. Please see I.4 for
details.
Updates or corrections to material contained on the DVD distribution
set are posted on the All-Sky DVD Release
Update web page.
[Last Updated: 2006 Jun 5, by R. Cutri]
b. Atlas Image Information Table
c. Known Asteroid Association List
d. Known Comet Association List
e. Known Planet and Satellite Association List
f. Extended Source Spatial Coverage Maps
g. PSC and XSC Anomaly Files
h. DVD-ROM Release Updates
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