Atacama Cosmology Telescope: Modeling the gas thermodynamics in BOSS CMASS galaxies from kinematic and thermal Sunyaev-Zel’dovich measurements

Abstract

The thermal and kinematic Sunyaev-Zel'dovich effects (tSZ, kSZ) probe the thermodynamic properties of the circumgalactic and intracluster medium (CGM and ICM) of galaxies, groups, and clusters, since they are proportional, respectively, to the integrated electron pressure and momentum along the line of sight. We present constraints on the gas thermodynamics of CMASS (constant stellar mass) galaxies in the Baryon Oscillation Spectroscopic Survey using new measurements of the kSZ and tSZ signals obtained in a companion paper [Schaan et al.]. Combining kSZ and tSZ measurements, we measure within our model the amplitude of energy injection ϵM ⋆ c 2 , where M ⋆ is the stellar mass, to be ϵ ¼ ð40 AE 9Þ × 10 −6 , and the amplitude of the nonthermal pressure profile to be α Nth < 0.2ð2σÞ, indicating that less than 20% of the total pressure within the virial radius is due to a nonthermal component. We estimate the effects of including baryons in the modeling of weak-lensing galaxy cross-correlation measurements using the best-fit density profile from the kSZ measurement. Our estimate reduces the difference between the original theoretical model and the weak-lensing galaxy cross-correlation measurements in [A. Leauthaud et al., Mon. Not. R. Astron. Soc. 467, 3024 (2017)] by half (50% at most), but does not fully reconcile it. Comparing the kSZ and tSZ measurements to cosmological simulations, we find that they underpredict the CGM pressure and to a lesser extent the CGM density at larger radii with probabilities to exceed ranging from 0.00 to 0.03 and 0.12 to 0.14, for tSZ and kSZ, respectively. This suggests that the energy injected via feedback models in the simulations that we compared against does not sufficiently heat the gas at these radii. We do not find significant disagreement at smaller radii. These measurements provide novel tests of current and future simulations. This work demonstrates the power of joint, high signal-to-noise kSZ and tSZ observations, upon which future cross-correlation studies will improve.

Atacama Cosmology Telescope: Combined kinematic and thermal Sunyaev-Zel’dovich measurements from BOSS CMASS and LOWZ halos

“…This joint tSZ and kSZ measurement also informs the "lensing is low" tension, where the galaxygalaxy lensing signal of BOSS galaxies is found to be anomalously low, compared to the expected signal based on their clustering [39][40][41]. This paper and companion paper [36] are a first step in constraining the gas thermodynamics in galaxy groups and directly measuring the baryonic effects in weak lensing. References [42,43] present complementary kSZ and tSZ measurements using the same microwave temperature maps, but consider different galaxy samples, and instead focus on the luminosity dependence of the signals and the velocity correlation function, which contains information on neutrino masses [44], dark energy and modifications to general relativity [45] and primordial non-Gaussianity [46].…”

“…The tSZ signal is detected by its characteristic spectral signature in our multifrequency CMB data, in which it yields a temperature decrement (increment) at frequencies below (above) 217 GHz. Thermal emission from dust inside the galaxy groups produces a smaller and more concentrated temperature excess, which we also measure and correct for in several ways [36]. This tSZ stacking procedure nulls the kSZ signal, which changes sign depending on the galaxy group's bulk velocity, and thus cancels on average.…”

“…Percentlevel sidelobes are visible at 2-4 0 . These are included in the modeling of the signal in [36]. The beams for the ILC maps with and without deprojection from [78] are shown in green and cyan.…”

“…The tSZ and kSZ thus provide complementary information on the electron density and temperature in galaxies and clusters. In principle, by combining the kSZ, tSZ and lensing mass measurements from the same galaxies or clusters, we can fully determine the thermodynamic properties of the sample, including the amount of energy injected by feedback or the fraction of nonthermal pressure support [34][35][36]. In the absence of kSZ measurements, this approach would be limited by the modeling of the gas temperature (for tSZ) and clumping (x rays) [37,38].…”

“…Finally, our conclusions are found in Sec. V. The interpretation of the measurements is presented in detail in [36].…”