Cosmoglobe DR2. II. CIB monopole measurements from COBE-DIRBE through global Bayesian analysis

• Main Authors: Watts, D. J, Galloway, M, Gjerløw, E, San, M, Aurlien, R, Basyrov, A, Brilenkov, M, Eriksen, H. K, Fuskeland, U, Herman, D, Ihle, H. T, Lunde, J. G. S, Næss, S. K, Stutzer, N. -O, Thommesen, H, Wehus, I. K
• Format: Journal Article
• Language: English
• Published: 03-06-2024
• Subjects: Physics - Cosmology and Nongalactic Astrophysics
• DOI: 10.48550/arxiv.2406.01491

We derive new constraints on the CIB monopole spectrum from a set of
reprocessed COBE-DIRBE sky maps that have lower instrumental and astrophysical
contamination than the legacy DIRBE maps. These maps have been generated
through a global Bayesian analysis framework that simultaneously fits
cosmological, astrophysical, and instrumental parameters, as described in a
series of papers collectively referred to as Cosmoglobe DR2. We have applied
this method to the DIRBE TODs, complemented by selected HFI and FIRAS sky maps
to break key astrophysical degeneracies, as well as WISE and Gaia compact
object catalogs. In this paper, we focus on the CIB monopole constraints that
result from this work. We report positive detections of an isotropic signal in
six out of the ten DIRBE bands (1.25, 2.2, 3.5, 100, 140, and 240 $\mathrm{\mu
m}$). For the 2.2 $\mu$m channel, we find an amplitude of
$10.2\pm1.2\,\mathrm{nW\,m^{-2}\,sr^{-1}}$, 74 % lower than that reported from
the official DIRBE maps. For the 240 $\mu\mathrm{m}$ channel, we find
$6\pm3\mathrm{nW\,m^{-2}\,sr^{-1}}$, 56 % lower than the official DIRBE
release. We interpret these lower values as resulting from improved zodiacal
light and Galactic foreground modeling. For the bands between 4.9 and 60
$\mu\mathrm{m}$, the presence of excess radiation in solar-centric coordinates
precludes the definition of lower limits. However, the analysis still provides
well-defined upper limits. For the 12 $\mu\mathrm{m}$ channel, we find an upper
95 % confidence limit of 55 $\mathrm{nW\,m^{-2}\,sr^{-1}}$, more than a factor
of eight lower than the corresponding legacy result of 468
$\mathrm{nW\,m^{-2}\,sr^{-1}}$. The results presented in this paper redefine
the state-of-the-art CIB monopole constraints from COBE-DIRBE, and provide a
real-world illustration of the power of global end-to-end analysis of multiple
complementary datasets.