Deciphering Baryonic Feedback from ACT tSZ Galaxy Clusters

Abstract

The next generation of cosmology surveys will probe the matter distribution of the universe to unparalleled precision. To match this level of precision in cosmological parameter estimation, we need to use information at small scales of $\sim$ 1 Mpc, which requires an accurate model of baryonic feedback. In this paper, we employ the Dark Matter + Baryon (DMB) model, a flexible halo model that is well-fit to various hydrodynamical simulations, to extract information on baryonic feedback from galaxy cluster observables. Using a sample of thermal Sunyaev-Zeldovich (tSZ) selected galaxy clusters from the Atacama Cosmology Telescope (ACT) - with masses calibrated via weak lensing from the Dark Energy Survey (DES) - we develop a robust end-to-end pipeline that directly models the calibrated observables. Our analysis demonstrates that the tSZ Y-M relation can constrain several DMB model parameters, providing key insights into baryonic feedback effects on cosmic shear at the several percent level. We find a preference for intermediate to strong levels of feedback, which is both consistent with several hydrodynamic simulations and competitive with similar analyses performed on complementary probes. Finally, we discuss the implications of our results in the context of current and upcoming cosmic shear surveys.

Figures (14)

• Figure 1: A schematic for the modeling approach that we take in this paper. Input parameters are given by the yellow ellipse and the data are denoted by red rectangles, whereas computed quantities are in blue rectangles. The green circles detail the various modeling components that are used to describe the data vector, and our main result is the computed suppression in the power spectrum.
• Figure 2: Left: A plot of the different components of the DMB halo model (red) as compared to the a standard NFW profile (black). The blue dash-dotted line is the gas component of the profile described by Equation \ref{['eq:rhogas']}, the orange dashed line is the collisionless matter component described by Equation \ref{['eq:clm']}, and the green dotted line is the central galaxy component given by Equation \ref{['eq:cg']}. Right: The thermal pressure profile as it varies for different choices of DMB model parameters. In blue, we have the fiducial values, which are given by the mean of the prior, as shown in Table \ref{['tab:Halomodel']}. In orange, we vary the extent of the gas profile with $\theta_{\rm{ej}}$; in green and red we vary the gas slope by changing $\mu_\beta$ and $\gamma$ respectively.
• Figure 3: Histogram of the ACT DR5 cluster catalog in logarithmic bins of $y_{\rm{fixed}}$ (fixed_y_c in the catalog). Colors indicate the five larger bins that we use in our analysis.
• Figure 4: Sample images taken from the Nemo cluster detection pipeline. The left panel shows the true DMB cluster signal as a change in temperature $\delta T$ in $\mu \rm{K}$ with a 90 GHz beam. The middle panel shows the cluster signal combined with a simulated primary CMB signal. The rightmost panel shows the impact of noise on the cluster signal, and the necessity for matched filters to identify the underlying cluster.
• Figure 5: Sample model fits to data, displayed with color according to the value of one of the better constrained parameters $\mu_\beta$, which is the mass dependence of the slope of the gas profile. The model fits are heavily weighted to the first three data points in $y_{\rm{fixed}}$ given that these three bins contain most of the clusters in the catalog, and have the tightest errors on the mean mass. The bin widths corresponding to the same bins in Figure \ref{['fig:bins']} are color coded in the background of the plot.