II. Contents of the First 2MASS Incremental Data Release

1. General Properties of the Data Release

• Range of Dates From Which Release Was Drawn:     1997 June 7 - 1998 January 30 UT
  
  
• Total Number of Fully or Partially Photometric Nights in that Range:     100
  
  
• Number of Tiles Included in Release:     3391



• Area of Release (includes a 10´´ inner border for each tile):     2483 sq.degrees    



• Map of Regions Included in Release
  (galactic aitoff projection with equatorial coordinate grid, overlaid on 100 micron IRAS all-sky map)



• Range of Galactic Latitudes Covered (not complete):     -51.0° < b < +86.7°



• Criteria for Selection of Tiles to Include in Release:
  • Data Acquired in Photometric Conditions
    (photometric zero point offsets < 0.04 mag in all 3 bands)
  
  
  
  • Photometric Sensitivity Meets Level 1 Requirements in all 3 Bands
    (based on Average Sky Background Levels and Seeing in Tile)
  
  
  
  • Average Seeing FWHM < 3.5´´ in all 3 Bands
    (for accurate photometry and star/galaxy separation)
  
  
  
  • H-Band Atlas Image Background Residuals Due to Airglow < 1.20 DN
    (for accurate extended source photometry)
  
  
  
  • Tile Must Fall in Contiguous Block of >3 Acceptable Tiles
    (for accurate assessemnt of astrometric residuals)
  
  
  

• Basic Tile Information Available in the Scan Information Table Accessible via IRSA/CATSCAN
  • UT Observation Date and Time
  
  
  
  • Reconstructed Tile Corner Positions
  
  
  
  • Mean Photometric Parameters
  
  
  
  • Mean Point Source Noise Levels
  
  
  
  • Mean Extracted Source Densities
  
  
  

[Last Updated: 1999 May 6; by R. Cutri]