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Register a new userConstraining the intracluster pressure profile from the thermal SZ power spectrum
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Added by
Miriam Elizabeth Ramos-Ceja
Publication date
2014
fields
Physics
and research's language is
English
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The angular power spectrum of the thermal Sunyaev-Zeldovich (tSZ) effect is highly sensitive to cosmological parameters such as sigma_8 and Omega_m, but its use as a precision cosmological probe is hindered by the astrophysical uncertainties in modeling the gas pressure profile in galaxy groups and clusters. In this paper we assume that the relevant cosmological parameters are accurately known and explore the ability of current and future tSZ power spectrum measurements to constrain the intracluster gas pressure or the evolution of the gas mass fraction, f_gas. We use the CMB bandpower measurements from the South Pole Telescope and a Bayesian Markov Chain Monte Carlo (MCMC) method to quantify deviations from the standard, universal gas pressure model. We explore analytical model extensions that bring the predictions for the tSZ power into agreement with experimental data. We find that a steeper pressure profile in the cluster outskirts or an evolving f_gas have mild-to-severe conflicts with experimental data or simulations. Varying more than one parameter in the pressure model leads to strong degeneracies that cannot be broken with current observational constraints. We use simulated bandpowers from future tSZ survey experiments, in particular a possible 2000 deg^2 CCAT survey, to show that future observations can provide almost an order of magnitude better precision on the same model parameters. This will allow us to break the current parameter degeneracies and place simultaneous constraints on the gas pressure profile and its redshift evolution, for example.
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The pressure profiles of the Intracluster Plasma in galaxy clusters show a wide variance when observed in X rays at low redshifts z<0.2. We find the profiles to follow two main patterns, featuring either a steep or a shallow shape throughout both core and outskirts. We trace these shapes back to a physical dichotomy of clusters into two classes, marked by either low entropy (LE) or high entropy (HE) throughout. From X-ray observations and Sunyaev-Zeldovich stacked data at higher 0.2<z<0.4, we elicit evidence of an increasing abundance of HEs relative to LEs. We propose this to constitute a systematic trend toward high z; specifically, we predict the pressure profiles to converge into a truly universal HE-like template for z>0.5. We submit our physical templates and converging trend for further observational tests, in view of the current and upcoming measurements of individual, stacked, and integrated Sunyaev-Zeldovich signals.
The thermal Sunyaev-Zeldovich (tSZ) effect directly measures the thermal pressure of free electrons integrated along the line of sight and thus contains valuable information on the thermal history of the universe. However, the redshift information is entangled in the projection along the line of sight. This projection effect severely degrades the power of the tSZ effect to reconstruct the thermal history. We investigate the tSZ tomography technique to recover this otherwise lost redshift information by cross correlating the tSZ effect with galaxies of known redshifts, or alternatively with matter distribution reconstructed from weak lensing tomography. We investigate in detail the 3D distribution of the gas thermal pressure and its relation with the matter distribution, through our adiabatic hydrodynamic simulation and the one with additional gastrophysics including radiative cooling, star formation and supernova feedback. (1) We find a strong correlation between the gas pressure and matter distribution, with a typical cross correlation coefficient r ~ 0.7 at k . 3h/Mpc and z < 2. This tight correlation will enable robust cross correlation measurement between SZ surveys such as Planck, ACT and SPT and lensing surveys such as DES and LSST, at ~20-100{sigma} level. (2) We propose a tomography technique to convert the measured cross correlation into the contribution from gas in each redshift bin to the tSZ power spectrum. Uncertainties in gastrophysics may affect the reconstruction at ~ 2% level, due to the ~ 1% impact of gastrophysics on r, found in our simulations. However, we find that the same gastrophysics affects the tSZ power spectrum at ~ 40% level, so it is robust to infer the gastrophysics from the reconstructed redshift resolved contribution.
Galaxy cluster merger shocks are the main agent for the thermalization of the intracluster medium and the energization of cosmic ray particles in it. Shock propagation changes the state of the tenuous intracluster plasma, and the corresponding signal variations are measurable with the current generation of X-ray and Sunyaev-Zeldovich (SZ) effect instruments. Additionally, non-thermal electrons (re-)energized by the shocks sometimes give rise to extended and luminous synchrotron sources known as radio relics, which are prominent indicators of shocks propagating roughly in the plane of the sky. In this short review, we discuss how the joint modeling of the non-thermal and thermal signal variations across radio relic shock fronts is helping to advance our knowledge of the gas thermodynamical properties and magnetic field strengths in the cluster outskirts. We describe the first use of the SZ effect to measure the Mach numbers of relic shocks, for both the nearest (Coma) and the farthest (El Gordo) clusters with known radio relics.
We forecast the number of galaxy clusters that can be detected via the thermal Sunyaev-Zeldovich (tSZ) signals by future cosmic microwave background (CMB) experiments, primarily the wide area survey of the CMB-S4 experiment but also CMB-S4s smaller delensing survey and the proposed CMB-HD experiment. We predict that CMB-S4 will detect 75,000 clusters with its wide survey of $f_{rm sky}$ = 50% and 14,000 clusters with its deep survey of $f_{rm sky}$ = 3%. Of these, approximately 1350 clusters will be at $z ge 2$, a regime that is difficult to probe by optical or X-ray surveys. We assume CMB-HD will survey the same sky as the S4-Wide{}, and find that CMB-HD will detect $times3$ more overall and an order of magnitude more $z ge 2$ clusters than CMB-S4. These results include galactic and extragalactic foregrounds along with atmospheric and instrumental noise. Using CMB-cluster lensing to calibrate cluster tSZ-mass scaling relation, we combine cluster counts with primary CMB to obtain cosmological constraints for a two parameter extension of the standard model ($Lambda CDM+sum m_{ u}+w_{0}$). Besides constraining $sigma(w_{0})$ to $lesssim 1%$, we find that both surveys can enable a $sim 2.5-4.5sigma$ detection of $sum m_{ u}$, substantially strengthening CMB-only constraints. We also study the evolution of intracluster medium by modelling the cluster virialization ${rm v}(z)$ and find tight constraints from CMB-S4, with further factors of 3-4 improvement for CMB-HD.
We measure the Cosmic Microwave Background (CMB) skewness power spectrum in $textit{Planck}$, using frequency maps of the HFI instrument and the Sunyaev-Zeldovich (SZ) component map. The two-to-one skewness power spectrum measures the cross-correlation between CMB lensing and the thermal SZ effect. We also directly measure the same cross-correlation using $textit{Planck}$ CMB lensing map and the SZ map and compare it to the cross-correlation derived from the skewness power spectrum. We model fit the SZ power spectrum and CMB lensing-SZ cross power spectrum via the skewness power spectrum to constrain the gas pressure profile of dark matter halos. The gas pressure profile is compared to existing measurements in the literature including a direct estimate based on the stacking of SZ clusters in $textit{Planck}$.
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