The Spectrum of the Extragalactic Far‐Infrared Background from theCOBEFIRAS Observations

Abstract

The COBE FIRAS data contain foreground emission from interplanetary, Galactic interstellar dust and extragalactic background emission. We use three different methods to separate the various emission components, and derive the spectrum of the extragalactic Far InfraRed Background (FIRB). Each method relies on a different set of assumptions, which affect the FIRB spectrum in different ways. Despite this, the FIRB spectra derived by these different methods are remarkably similar. The average spectrum that we derive in the ν = 5 − 80 cm −1 (2000 -125 µm) frequency interval is:, where ν 0 = 100 cm −1 (λ 0 = 100 µm) and P is the Planck function. The derived FIRB spectrum is consistent with the DIRBE 140 and 240 µm detections. The total intensity received in the 5 -80 cm −1 frequency interval is 14 nW m −2 sr −1 , and comprises about 20% of the total intensity expected from the energy release from nucleosynthesis throughout the history of the universe.

Dusty star-forming galaxies at high redshift

“…The total intensity of the cosmic infrared background (CIB) at submm wavelengths is now known from absolute photometry measurements (Puget et al, 1996;Fixsen et al, 1998;Dwek et al, 1998). While the integrated intensity is known, albeit highly uncertain, we still do not have a complete understanding of the sources responsible for the background, the key reason being that existing surveys are limited by large beamsizes and confusion noise.…”

“…They report a CIB intensity of 0.69 +0.12 −0.07 MJy sr −1 at 250µm. The COBE CIB measurement at 240µmis at the level of 0.9 ± 0.2 MJy sr −1 (Puget et al, 1996;Fixsen et al, 1998;Dwek et al, 1998). While the two agree within one σ uncertainties, the lensing-based measurement is likely an underestimate as it only focuses on the sources behind the cluster and a separate accounting of the sources in the foreground needs to be made to obtain the total background intensity.…”

Demonstrating the feasibility of line intensity mapping using mock data of galaxy clustering from simulations

“…For the examples below we include both the CMB and emission from dust in our galaxy. The dust emission is treated as a black body with a ν 2 emissivity scaled to match the background radiation measured by COBE FIRAS in the faintest area on the sky [25]. In Figure 2, we illustrate the different components which make up our data sets.…”

X-ray Surveys of the Obscured Universe

“…The cosmic energy density spectrum from radio waves to high energy gamma rays in a νIν representation, where a horizontal line corresponds to equal radiation power per decade of energy. The FIR to UV data are from (left to right) [35,13,22,45,33,2]. The dotted line shows one of the models in [9] extrapolated from the visual to the EUV range.…”

“…the CMB, the interplanetary dust emission, the interstellar dust emission, scattering from the interplanetary dust (zodiacal light), galactic starlight and scattering by inter-stellar dust. In the far-infrared range different groups have recently detected the long-sought residual cosmic far-infrared background (CIB) signal [35,22,13] by carefully modelling the other components in the high-frequency tail of the Cosmic Microwave Background (see fig. 1).…”