Appendix 1. Introduction to the 2MASS Extended Mission and Ancillary Data Products


6. Auxiliary Tables

The 2MASS Survey, 6x and Calibration Scan Point Source WDBs contain 41,029 entries that are positionally associated with the predicted positions of known asteroids, comets, planets or planetary satellites. These sources were identified during scan data processing by determining which known solar system objects 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 solar system object ephemerides and position prediction methods used.

Association between predicted solar system object and 2MASS source positions does not imply a physical identification. The probability of chance associations with detections of background stars is significant, particularly in high source density regions at low galactic latitudes. Background source "contamination" is discussed in IV.9.b. Because the full 2MASS WDBs contain a large number of spurious detections of noise and image artifacts, predicted asteroid, comet, planet or planetary satellite positions may also be associated by chance with noise or artifact detections. The reliability of the 2MASS point source detections associated with the predicted solar system object positions is indicated by the WDB reliability flag, rel, that is included with each entry in the tables below. This flag describes the probability that the 2MASS detection is a real source as opposed to the probability that the association with a specific source is correct.

a. Known Asteroid Association Lists

The Survey, 6x and Calibration WDB Known Asteroid Association List gives for each asteroid that was associated with an extraction in these point source WDBs, object identification, orbital data used to predict positions and visual brightness, and abridged WDB data for the source. All of the asteroid associations from the three data sets are concatenated into one table, and sorted by asteroid designation. The data set of origin for each association is indicated in the "DS" column (S=Survey, 6=6x, C=Calibration). Cross-reference to the full WDB source entry (and in some cases the Extended Source WDB) 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 WDB names to save space. The full WDB column names are given in the definitions in these cases.

Asteroids may have multiple entries in this table because they were detected more than once during the Survey, 6x and Calibration observations and appear in one or more WDBs multiple times. This is especially true for the Calibration Scan WDBs since some of those fields were observed up to 36 times each night.

Table 1 - Survey, 6x and Calibration Scan WDB Known Asteroid Association List

b. Known Comet Association Lists

The Survey, 6x and Calibration WDB Known Comet Association Lists gives for each comet that was associated with an extraction in the point source WDBs, object identification, orbital data used to predict positions and visual brightness, and abridged WDB data for the source. All of the comet associations from the two data sets are concatenated into one table, and sorted by comet name. The data set of origin for each association is indicated in the "DS" column (S=Survey, 6=6x, C=Calibration). Cross-reference to the full PSWDB source entry (and in some cases the Extended Source WDBs) 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 WDB names to save space. The full WDB column names are given in the definitions in these cases.

Several comets appear more than once in this table because they were scanned and detected multiple times in the Survey or Calibration observations.

Table 2 - Survey, 6x and Calibration Scan WDB Known Comet Association List

c. Planet and Planetary Satellite Association Lists

The Survey Point Source WDB contains 19 extractions that are associated with Uranus, Neptune and Pluto, and satellites of these planets and Jupiter. Jupiter was scanned during Survey operations, but 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 saved in the Working Databases. Several Jovian satellites were detected in adjacent scans that were preserved, and their extractions are included in the Survey WDB. Mars and Saturn were not directly observed by 2MASS, the closest scans being 2.6 and 1 deg away, respectively. There are no planet or planetary satellite detections known to be in the 6x or Calibration WDBs.

Planetary detections were identified during survey, 6x and calibration 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. Please read IV.9 for a description of this procedure, for details concerning planet ephemerides and position prediction, and for important caveats concerning the associations.

Planetary satellite associations were made manually after pipeline data processing was complete. Ephemerides for all of the named moons of Jupiter, Saturn, Uranus and Neptume were generated for each night of 2MASS operations using the JPL Horizons system. Predicted satellite positions on each night were then correlated with the positions of all extractions in the Survey PSWDB. Potential associations were then screened by hand to filter out spurious associations with artifacts, noise, or inertially fixed background objects.

The Survey Planet and Planetary Satellite Association List gives for each planet and satellite associated with a source in the Survey WDB object identification, orbital data used to predict positions and visual brightness, and abridged WDB data for the source. Cross-reference to the full WDB source entry is made via the pts_key column. 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 WDB names to save space. The full WDB column names are given in the definitions in these cases.

Uranus appears three times in this table, and several of its satellites appear twice because their positions were scanned and detected multiple times during the Survey, and thus have multiple entries in the WDB. However, Uranus was not accurately measured by the point source characterization because of its large extent. It is not found in the Survey XSWDB.

Table 3 - Survey WDB Planet and Planetary Satellite Association List


[Last Update: 2006 December 30, by R. Cutri]


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