2MASS Facts
SURVEY LEVEL 1 REQUIREMENTS
The complete version
giving the specs and justification for most specs. (ps file)
Bands Surveyed and Sensitivity
| | Completeness and Reliability Mag. limits
|
|---|
| Band | Wavelength (µm) | Point Sources (SNR=10)1 | Extended Sources
|
|---|
| J | 1.25 | 15.8 | 15.0
|
| H | 1.65 | 15.12 | 14.33
|
| Ks | 2.17 | 14.3 | 13.5
|
Note: These specs only apply to unconfused sources outside of the Galactic Plane (|b|>10o), and outside of any
confusion-limited areas of the sky outside of the Galactic Plane.
1 At SNR=10, sigma(mag) = 2.5 / ln 10 = 0.109
2 The feasibility of this requirement is uncertain due to lack of knowledge of the background variations at H.
3 14.2 in Level 1 Science Requirements Document was a misprint. All values intended to be 0.8 mag brighter than point source limits.
Completeness and Reliability
| | Absolute Galactic Latitude Range
|
|---|
| Parameter | >30o | 20-30o | 10-20o | <10o
|
|---|
| Differential Completeness1
|
|---|
| Point Sources | 0.99 | -- | -- | --
|
| Extended Sources2 | 0.90 | -- | -- | --
|
| Differential Reliability1
|
|---|
| Point Sources | 0.9995 | 0.9995 | 0.9995 | 0.9995
|
| Extended Sources | 0.99 | 0.99 | 0.80 | --
|
Note: These specs only apply to unconfused sources outside of the Galactic Plane (|b|>10o), and outside of any
confusion-limited areas of the sky outside of the Galactic Plane.
1 Differential Completeness (Reliability) is the completeness (reliability) of sources falling in the last half-magnitude bin above the completeness limit.
2 The completeness for extended sources applies only to galaxies that can be reliably distinguished from point sources, with "shape" values 0.5" greater than those of the mean point sources.
Photometric and Positional Accuracy
- Photometric precision
- unconfused point sources (for sources with SNR >> 20): 5%
- unconfused extended sources (for isophotal
magnitude at 20 mag/square arcsecond): 10% (H < 13.8)
- Photometric spatial uniformity
- point sources: 4%
- extended sources: 10%
- Position Reconstruction Error (1 coordinate, 1 sigma, SNR>20): 0.5"
- Brightest stars
- bias (for K > 4): < 2%
- repeatability:
- Position reconstruction: 0.5" (1 sigma) for unconfused sources
Sky coverage
- |b| > 10o: 95%
|b| < 10o: 95%
- Overall coverage: no gaps > 200 sq. deg.
http://spider.ipac.caltech.edu/staff/tchester/2mass/facts.html
Comments to: Tom Chester
Last update: 26 June 1997