A new constraint on the $y$-distortion with FIRAS: implications for feedback models in galaxy formation and cosmic shear measurements

Abstract

The $y$-type distortion of the blackbody spectrum of the cosmic microwave background radiation probes the pressure of the gas trapped in galaxy groups and clusters. We reanalyze archival data of the FIRAS instrument with an improved astrophysical foreground cleaning technique, and measure a mean $y$-distortion of $\langle y\rangle = (1.2\pm 2.0) \times 10^{-6}$ ($\langle y\rangle\lesssim 5.2\times 10^{-6}$ at 95\% C.L.), a factor of $\sim 3$ tighter than the original FIRAS results. This measurement directly rules out many models of baryonic feedback as implemented in cosmological hydrodynamical simulations, mostly using information in objects with mass $M\lesssim 10^{14} {\rm M}_{\odot}$. We discuss its implications for the analysis of cosmic shear and kinetic Sunyaev-Zel'dovich effect data, and future spectral distortion experiments.

Figures (9)

• Figure 1: SEDs of sky monopole components on the P60 footprint from the Planck Commander sky model planck15_fg, compared to the FIRAS total error (green). Our new $\langle y\rangle$ measurement and cumulative signal-to-noise ratio relative to FIRAS errors are in solid and dotted black. The grey area denotes excluded FIRAS frequencies. The shaded red shows the Galactic dust monopole on the P80 and P20 footprints. The orange line and shading represent the mean, maximum, and minimum CIB monopole amplitudes for our considered CIB SEDs. The purple points indicate foreground template noise from the original FIRAS analysis.
• Figure 1: $y$ maps obtained with different component separation methods investigated in this work. The top right panel shows the consistency mask that identifies pixels for which different component separation methods give consistent estimates (red). Pixels removed by the FIRAS destriper mask appear in grey.
• Figure 2: $\langle y\rangle$ measurements obtained with different foreground cleaning methods on FIRAS real (blue) and mock (orange) data obtained on the P60 mask. Our best estimate is shown in red.
• Figure 2: As Fig. \ref{['fig:implications']} in the main text for Astrid LH and SB7 suites. The darker grey shaded areas show the 95th percentile.
• Figure 3: Left: CAMELS SIMBA predictions of $\langle T_e\rangle$, $\langle y\rangle$ color coded by values of $A_{AGN2}$ (top) and $A_{SN2}$ (bottom) compared to our $\langle y\rangle$ measurement (red). As $\langle T_e\rangle$ is unconstrained by the data, we fix it to the median of the predictions. The excluded area at 95% C.L. is shown in grey. Right: baryon-induced matter power spectrum suppression measured in the CAMELS SIMBA LH suite with allowed values constrained from DES cosmic shear alone (orange) and with kSZ data (purple). The median of the excluded (allowed) models in the left panels is shown in grey (blue) and the corresponding shaded area show their 16th and 84th percentiles. The suppression of the fiducial SIMBA simulation appears in black simba.