Cosmic Infrared Background Tomography and a Census of Cosmic Dust and Star Formation

Abstract

The cosmic far-infrared background (CIB) encodes dust emission from all galaxies and carries valuable information on structure formation, star formation, and chemical enrichment across cosmic time. However, its redshift-dependent spectrum remains poorly constrained due to line-of-sight projection effects. We address this in [arXiv:2504.05384][1] by cross-correlating 11 far-infrared intensity maps spanning a 50-fold frequency range from Planck, Herschel, and IRAS, with spectroscopic galaxies and quasars from SDSS I-IV tomographically. We mitigate foregrounds using [CSFD][2], a CIB-free Milky Way dust map, and also remove the tomographic SZ background from hot gas in the cosmic web detected in [arXiv:2006.14650][3]. These cross-correlation amplitudes on two-halo scales trace bias-weighted CIB redshift distributions and collectively yield a 60σ detection of the evolving CIB spectrum, sampled across hundreds of rest-frame frequencies over 0 < z < 4. We break the bias-intensity degeneracy by adding monopole information from FIRAS. The recovered CIB spectrum reveals a dust temperature distribution that is broad, spanning the full range of host environments, and moderately evolving. Using low-frequency CIB amplitudes, we constrain cosmic dust density, Ω_dust, which peaks at z = 1-1.5 and declines threefold to the present. Our wide spectral and sky coverages enable a determination of the total infrared luminosity density with negligible cosmic variance across 90% of cosmic time. This yields a more precise yet consistent constraint on the cosmic star formation history compared to the Madau & Dickinson (2014) compilation. Additionally, we find that star formation occurs in a mode that is, on average, 80% dust-obscured at z = 0 and 60% at z = 4. Our results, based on intensity mapping, are complete, requiring no extrapolation to faint galaxies or low-surface-brightness components. We release our tomographic CIB spectrum and redshift distributions in [this link][4] as a public resource for future studies of the CIB, both as a cosmological matter tracer and CMB foreground. [1]: https://arxiv.org/abs/2504.05384 [2]: https://arxiv.org/abs/2306.03926 [3]: https://arxiv.org/abs/2006.14650 [4]: https://zenodo.org/records/15149425