Also See:

• Spitzer Background Estimation: Methods and implementation (e.g., how Spot calculates backgrounds)
• Spitzer Performance Estimation Tool.

The background estimates were generated using a prototype version of the Spitzer background estimator. Three lines of sight were chosen to represent low, medium, and high background.

Line of Sight Parameters

Background Contributions

The background model includes the zodiacal light, interstellar medium (cirrus), and the cosmic infrared background (at wavelengths greater than 100 microns). The contributions of each component can be seen in the figure below. The zodiacal light dominates IRAC and IRS wavelengths for all these lines of sight. For MIPS 70 microns, there are comparable interstellar and zodiacal contributions, while at 160 microns, the interstellar contribution dominates.

Brightness Values

The background spectra were integrated over the Spitzer passbands and the results are reported as per the Spitzer calibration convention (same as IRAS, ISO, COBE) below. The first column is the mnemonic wavelength for the band and the second column is the quoted surface brightness of that band. For reference, the color corrections ranged from 0.98 to 1.08.

A. Low-background


Wavelength (microns)	Background (MJy/sr)
3.60000	0.0769
4.50000	0.267
5.80000	1.37
8.00000	5.47
15.7500	16.8
22.2500	16.7
24.0000	16.1
70.0000	5.15
160.000	6.53

B. Medium-background


Wavelength (microns)	Background (MJy/sr)
3.60000	0.125
4.50000	0.366
5.80000	1.93
8.00000	7.69
15.7500	24.4
22.2500	24.7
24.0000	23.9
70.0000	8.95
160.000	16.5

C. High-background


Wavelength (microns)	Background (MJy/sr)
3.60000	0.43
4.50000	0.85
5.80000	4.64
8.00000	18.3
15.7500	63.1
22.2500	67.0
24.0000	65.6
70.0000	32.3
160.000	84.3