Measurements of Diffuse Sky Emission Components in High Galactic Latitudes at 3.5 and 4.9 um Using DIRBE and WISE Data

TL;DR

This study reanalyzes all-sky infrared data to measure diffuse sky emissions at high Galactic latitudes, improving estimates of interstellar dust components and residual isotropic emission, with implications for understanding cosmic background light.

Contribution

It introduces an improved method for estimating integrated starlight using WISE data and provides new constraints on dust composition and residual emission in the near-infrared.

Findings

DGL correlates linearly with 100 um emission at high Galactic latitudes.

PAH particles constitute more than ~2% of total dust mass.

Residual emission at 3.5 um is marginally consistent with EBL constraints.

Abstract

Using all-sky maps obtained from COBE/DIRBE at 3.5 and 4.9 um, we present a reanalysis of diffuse sky emissions such as zodiacal light (ZL), diffuse Galactic light (DGL), integrated starlight (ISL), and isotropic residual emission including the extragalactic background light (EBL). Our new analysis, which includes an improved estimate of ISL using the Wide-field Infrared Survey Explorer (WISE) data, enabled us to find the DGL signal in a direct linear correlation between diffuse near-infrared and 100 um emission at high Galactic latitudes (|b| > 35 degree). At 3.5um, the high-latitude DGL result is comparable to the low-latitude value derived from the previous DIRBE analysis. In comparison with models of the DGL spectrum assuming a size distribution of dust grains composed of amorphous silicate, graphite, and polycyclic aromatic hydrocarbon (PAH), the measured DGL values at 3.5 and 4.9 um constrain the mass fraction of PAH particles in the total dust species to be more than ~ 2%. This was consistent with the results of Spitzer/IRAC toward the lower Galactic latitude regions. The derived residual emission of 8.9 +/- 3.4 nW m^{-2} sr^{-1} at 3.5 um is marginally consistent with the level of integrated galaxy light and the EBL constraints from the gamma-ray observations. The residual emission at 4.9 um is not significantly detected due to the large uncertainty in the ZL subtraction, same as previous studies. Combined with our reanalysis of the DIRBE data at 1.25 and 2.2 um, the residual emission in the near-infrared exhibits the Rayleigh-Jeans spectrum.