Sources of confusion noise in the infrared wavelength range

Abstract

In this paper we use the model of extragalactic background light to investigate the factors that have influence on the confusion noise. It was shown that (1) Large-Scale Structure of the Universe is an important factor; (2) gravitational lensing does not have a significant effect on the confusion noise; (3) lower redshift limit of objects that contribute to the confusion noise does not depend on the wavelength and is about $z_{min}\sim 0.5-0.6$, while upper redshift limit gradually changes from $\sim4$ to $\sim3$ with the increase of wavelength from 70$\mu m$ up to 2000$\mu m$; (4) at rather short wavelengths ($\simeq70\mu m$) galaxies with luminosities in the range $10^7L_\odot$ -- $10^9L_\odot$ give the most contribution to the confusion noise, while at larger wavelengths (650-2000$\mu m$) their luminosities are greater than $L\geq10^{10}L_\odot$; (5) contribution from objects with different color characteristics is considered; (6) the variability of the extragalactic background on the timescale from 1 day to 1 year is noticeable at short wavelengths (70--350$\mu m$) and manifests at fluxes ${}^<_\sim$ 1~mJy.