Constraints on galaxy formation from the cosmic-infrared-background$\,-\,$optical-imaging cross-correlation using $\boldsymbol{Herschel}$ and UNIONS

Abstract

Using Herschel-SPIRE imaging and the Canada-France Imaging Survey (CFIS) Low Surface Brightness data products from the Ultraviolet Near-Infrared Optical Northern Survey (UNIONS), we present a cross-correlation between the cosmic infrared background and cosmic optical background fluctuations. With a combined sky area of 91 deg 2 and a minimum resolved scale of 18 arcsec, the cross-spectrum is measured for two cases: all galaxies are kept in the images; or all individually-detected galaxies are masked to produce 'background' maps. We report the detection of the crosscorrelation signal at 22 σ ( 18 σ for the background map). The part of the optical brightness variations that are correlated with the submm emission translates to an rms brightness of 32.5 mag arcsec −2 in the r band, a level normally unreachable for individual sources. A critical issue is determining what fraction of the cross-power spectrum might be caused by emission from Galactic cirrus. For one of the fields, the Galactic contamination is approximately a factor of 10 higher than the extragalactic signal, with the contamination being estimated using a linear regression from several external survey maps; however, for the other fields, the contamination is typically around 20 per cent. An additional discriminant is that the cross-power spectrum is of the approximate form P (k) ∝ 1/k, much shallower than that of Galactic cirrus. We interpret the results in a halo-model framework, which shows good agreement with independent measurements for the scalings of star-formation rates in galaxies. The approach presented in this study holds great promise for future surveys such as FYST/CCAT-prime combined with Euclid or the Vera Rubin Observatory (LSST), which will enable a detailed exploration of the evolution of star formation in galaxies.

A Recipe for Unbiased Background Modeling in Deep Wide-field Astronomical Images

“…This reinforces our assumption that the same dust population emits thermally in the submillimeter and scatters the starlight in the optical (as expected by dust models, Zhang et al 2023; and see discussion in Section 8.2). This correlation is also supported by observations in various other studies (e.g., Ienaka et al 2013;Miville-Deschênes et al 2016;Román et al 2020;Marchuk et al 2021;Lim et al 2022;Smirnov et al 2023). Note that the resolution of Planck (beam FWHM 5…”

“…Due to the low temperature of the dust grains, they are most prominent at FIR-submillimeter wavelengths. However, deep imaging surveys probing below 28 mag arcsec −2 in the optical bands have revealed the presence of Galactic cirrus across the sky (e.g., Duc et al 2015;Mihos et al 2017;Zaritsky et al 2019;Román et al 2020;Zaritsky et al 2021;Lim et al 2022).…”

“…One person's trash is another's treasure. The Galactic cirrus contaminant in extragalactic science is of great interest to researchers interested in the interstellar dust at visible wavelengths in the Milky Way, particularly those seeking to constrain their physical properties and conditions (e.g., Ienaka et al 2013;Miville-Deschênes et al 2016;Marchuk et al 2021;Lim et al 2022;Smirnov et al 2023;Zhang et al 2023). Historically, using Galactic cirrus complexes at visible wavelengths as diagnostics has been difficult because of the low surface brightness nature of the structures and their large angular sizes, which can span many degrees on the sky.…”