II. Contents of the Second 2MASS Incremental Data Release
1. General Properties of the Data Release
- Range of Dates Over Which Release Data Were Acquired:
- North: 1997 June 7 - 1998 December 14 and 1999 February 2 - 1999 May 21 UT
- South: 1998 March 19 - 1999 February 20 UT
- Total Number of Fully or Partially Photometric Nights in that Range:
- North: 329
- South: 239
- Number of Survey Tiles Included in Release (59,650 in full sky): 27,493
- Area of Release:
- Nominal unique area covered by Tiles: 19,680.8 sq.degrees
- Effective area of PSC (includes a 10´´ border for each Tile): 19,641.6 sq.degrees
- Effective area of XSC (includes a 15´´ border for each Tile): 19,609.4 sq.degrees
- Sky Coverage Map for Second Incremental Release (2MASS PSC JHKs surface density map in galactic aitoff projection, with equatorial coordinate grid overlay; c.f. I.6a.)
- Criteria for Selection of Tiles to Include in Release (c.f. V.2 for more details):
- Data Acquired in Photometric Conditions
(residuals to a linear fit to photometric zero point offset < 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 Background Residual Noise Due to Atmospheric Airglow < 5x the Noise Value Predicted for Background Level and Source Density in >87% of a Tile Area (for accurate extended source photometry)
- Tile Must Fall in Contiguous Block of >3 Acceptable Tiles (for accurate assessment of positional uncertainties)
- Data Acquired in Photometric Conditions
- Basic Tile Information Available in the
Scan Information Table Accessible
via IRSA/GATOR
- UT Observation Date and Time
- Reconstructed Tile Corner Positions
- Mean Photometric Parameters
- Mean Point Source Noise Levels
- Mean Extracted Source Densities
[Last Updated: 2000 April 10; by R. Cutri]
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