Details of EDGE's capabilities

EDGE will map the large-scale spatial distribution of galaxies and proto-galaxies. It will measure galaxy distribution on the largest spatial scales through a new observational tool, the anisotropy of the Cosmic Infrared Background (CIB). CIB variations, when observed with 6' resolution present themselves as changes in surface brightness. These changes probe the distribution of galaxies at large scale without requiring galaxy counting. A simulation of the cosmic infra-red background fluctuations that EDGE will observe is shown below. The speed with which areas of sky may be measured, relative to source counting, opens new avenues for tesing the growth of large-scale structure. The intrinsic uncertainties due to source counting noise are reduced because of the large sampled volume, enabling higher sensitivity measurements. Redshift information is obtained using the 8 spectral bands. This measurement of light emission is compared to the underlying dark matter distribution to trace the evolution of galaxy bias. EDGE will determine the emission weighted galaxy bias as a function of redshift and its dependence on scale-size, to better than 5%.

This image is a simulation of the cosmic infrared background fluctuations at 440 GHz. The large map is shown at the EDGE angular resolution. The inset shows a field from the SCUBA survey carried out by Scott et al. (astro-ph/0107446), with protogalaxies identified by red circles. The size of the inset field is about one EDGE resolution element. Click on image for larger version.

EDGE will measure variations in the distribution of galaxies on spatial scales ranging from > 200/h Mpc, where dark matter variations are determined directly from the cosmic microwave background radiation anisotropy to 5/h Mpc, where the distribution of dark matter and galaxies is determined from galaxy redshift surveys and the underlying dynamics of structure growth is non-linear. The EDGE mission will span this range of scale and provide a link between these complementary large-scale structure probes.

One of the important features of EDGE is its ability to separate out astrophysical sources based on how much they radiate at different wavelengths. EDGE records the radiation in 8 bands of the spectrum to be able to achieve this as mentioned above. The figure below shows the expected fluctuations in the infra-red, and contributions from interstellar dust, the cosmic microwave background anisotropy and the fluctuations in the CIB as measured with the Far Infrared Absolute Spectrophotometer (FIRAS) instrument on the Cosmic Background Explorer (COBE) satellite. The EDGE spectral bands are included at the top of this figure.

EDGE's advances to cosmology are made possible by its ability to separate astrophysical sources based on their spectral content. At the top of the figure is the model Cosmic Infrared Background (CIB) fluctuations (red) which is fit to data obtain from the FIRAS instrument on the COBE satellite. The light grey band is the +/- 1 sigma error band for the FIRAS measurement. The modeled CIB emission from four ranges in redshift are shown in light red. Also shown is the spectrum of the cosmic microwave background (CMBR) anisotropy in dashed black, and the spectrum of interstellar dust from our galaxy (blue). The dust spectrum plotted is for 1% contrast in amplitude at the South Galactic Pole. The EDGE spectral bands are shown at the top and will separate out the contributions from these different spectra. Click on image for a larger version.