II. NEOWISE Single-exposure Source Database

II.1. General Properties

II.1.f. Additional Information

II.1.f.i. AllWISE and 2MASS Associations

Each Entry in the NEOWISE Single-exposure Source Database has been positionally cross-correlated with the AllWISE Source Catalog, and the 2MASS Point and Extended Source Catalogs (PSC and XSC).

A simple positional search was made in a circular region with a radius of 3 arcsec around the position of each NEOWISE Source Database entry in the AllWISE Source and 2MASS Point Source Catalogs. If more than one AllWISE or 2MASS PSC object was found within 3 arcsec, the closest association is recorded. No correction was made for proper motion between the epochs of NEOWISE, AllWISE or 2MASS. For NEOWISE Source Database detections with AllWISE and/or 2MASS PSC associations, the DB entries include:

• the allwise_cntr and tmass_key parameters, which are the unique identifier of the associated AllWISE Catalog and 2MASS PSC sources,
• n_allwise and n_2mass, which are the number of AllWISE Catalog and 2MASS PSC sources, respectively, found within 3 arcsec of the NEOWISE position,
• the associated AllWISE Catalog source W1, W2, W3, and W4 profile-fit photometry magnitudes and their uncertainties,
• the associated 2MASS PSC source J, H and K_s default magnitudes and their uncertainties, and
• the amplitude and position angle of the vector from the NEOWISE extractions to the closest associated AllWISE and 2MASS PSC sources, in degrees East of North, r_allwise, pa_allwise, r_2mass and pa_2mass.

Associations between NEOWISE Single-exposure Source Database entries and the 2MASS XSC were searched using a matching radius equal to 1.1 times the K_s 20 mag/arcsec² isophotal elliptical aperture semi-major axis size of the 2MASS XSC source. This identifies NEOWISE extractions that are both identically the 2MASS XSC source, as well as some that are fragments of or foreground objects superimposed on the extended object. The separation between the NEOWISE and 2MASS XSC positions is given by xscprox value in the Source Database.

AllWISE and 2MASS source information included in the NEOWISE Source Database are associations, not identifications. Although the position accuracies of the Databases and Catalogs are all excellent, there is a non-zero probability of chance associations between physically unrelated objects, as well as missed associations. Moreover, moving solar system objects detected by NEOWISE may align with a background source in the AllWISE and/or 2MASS Catalogs. You should always confirm associations by carefully reviewing the entries from the NEOWISE Database and both Catalogs.

Last Updated: 6 February 2024