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Register a new userDetection of warm and diffuse baryons in large scale structure from the cross-correlation of gravitational lensing and the thermal Sunyaev-Zeldovich effect
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Ludovic Van Waerbeke
Publication date
2013
fields
Physics
and research's language is
English
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We report the first detection of a correlation between gravitational lensing by large scale structure and the thermal Sunyaev-Zeldovich (tSZ) effect. Using the mass map from the Canada France Hawaii Telescope Lensing Survey (CFHTLenS) and a newly-constructed tSZ map from Planck, we measure a non-zero correlation between the two maps out to one degree angular separation on the sky, with an overall significance of 6 sigma. The tSZ maps are formed in a manner that removes primary cosmic microwave background fluctuations and minimizes residual contamination by galactic and extragalactic dust emission, and by CO line emission. We perform numerous tests to show that our measurement is immune to these residual contaminants. The resulting correlation function is consistent with the existence of a warm baryonic gas tracing the large scale structure with a bias b_gas. Given the shape of the lensing kernel, our signal sensitivity peaks at a redshift z~0.4, where half a degree separation on the sky corresponds to a physical scale of ~10 Mpc. The amplitude of the signal constrains the product (b_gas/1)(T_e / 0.1 keV)(n_e / 1 m^-3)=2.01pm 0.31pm 0.21, at redshift zero. Our study suggests that a substantial fraction of the missing baryons in the universe may reside in a low density warm plasma that traces dark matter.
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We use the cosmo-OWLS suite of cosmological hydrodynamical simulations, which includes different galactic feedback models, to predict the cross-correlation signal between weak gravitational lensing and the thermal Sunyaev-Zeldovich (tSZ) $y$-parameter. The predictions are compared to the recent detection reported by van Waerbeke and collaborators. The simulations reproduce the weak lensing-tSZ cross-correlation, $xi_{ykappa}(theta)$, well. The uncertainty arising from different possible feedback models appears to be important on small scales only ($theta lesssim 10$ arcmin), while the amplitude of the correlation on all scales is sensitive to cosmological parameters that control the growth rate of structure (such as $sigma_8$, $Omega_m$ and $Omega_b$). This study confirms our previous claim (in Ma et al.) that a significant proportion of the signal originates from the diffuse gas component in low-mass ($M_{rm{halo}} lesssim 10^{14} M_{odot}$) clusters as well as from the region beyond the virial radius. We estimate that approximately 20$%$ of the detected signal comes from low-mass clusters, which corresponds to about 30$%$ of the baryon density of the Universe. The simulations also suggest that more than half of the baryons in the Universe are in the form of diffuse gas outside halos ($gtrsim 5$ times the virial radius) which is not hot or dense enough to produce a significant tSZ signal or be observed by X-ray experiments. Finally, we show that future high-resolution tSZ-lensing cross-correlation observations will serve as a powerful tool for discriminating between different galactic feedback models.
We confront the universal pressure profile (UPP) proposed by~citet{Arnaud10} with the recent measurement of the cross-correlation function of the thermal Sunyaev-Zeldovich (tSZ) effect from Planck and weak gravitational lensing measurement from the Red Cluster Sequence lensing survey (RCSLenS). By using the halo model, we calculate the prediction of $xi^{y-kappa}$ (lensing convergence and Compton-$y$ parameter) and $xi^{y-gamma_{rm t}}$ (lensing shear and Compton-$y$ parameter) and fit the UPP parameters by using the observational data. We find consistent UPP parameters when fixing the cosmology to either WMAP 9-year or Planck 2018 best-fitting values. The best constrained parameter is the pressure profile concentration $c_{500}=r_{500}/r_{rm s}$, for which we find $c_{500} = 2.68^{+1.46}_{-0.96}$ (WMAP-9) and $c_{500} = 1.91^{+1.07}_{-0.65}$ (Planck-2018) for the $xi^{y-gamma_t}$ estimator. The shape index for the intermediate radius region $alpha$ parameter is constrained to $alpha=1.75^{+1.29}_{-0.77}$ and $alpha = 1.65^{+0.74}_{-0.5}$ for WMAP-9 and Planck-2018 cosmologies, respectively. Propagating the uncertainties of the UPP parameters to pressure profiles results in a factor of $3$ uncertainty in the shape and magnitude. Further investigation shows that most of the signal of the cross-correlation comes from the low-redshift, inner halo profile ($r leqslant r_{rm vir}/2$) with halo mass in the range of $10^{14}$--$10^{15},{rm M}_{odot}$, suggesting that this is the major regime that constitutes the cross-correlation signal between weak lensing and tSZ.
This paper continues a series in which we intend to show how all observables of galaxy clusters can be combined to recover the two-dimensional, projected gravitational potential of individual clusters. Our goal is to develop a non-parametric algorithm for joint cluster reconstruction taking all cluster observables into account. In this paper, we begin with the relation between the Compton-y parameter and the Newtonian gravitational potential, assuming hydrostatic equilibrium and a polytropic stratification of the intracluster gas. We show how Richardson-Lucy deconvolution can be used to convert the intensity change of the CMB due to the thermal Sunyaev-Zeldovich effect into an estimate for the two-dimensional gravitational potential. Synthetic data simulated with characteristics of the ALMA telescope show that the two-dimensional potential of a cluster with mass 5*10^14 M_sun/h at redshift 0.2 is possible with an error of < 5% between the cluster centre and a radius r < 0.9 Mpc/h.
Stacking cosmic microwave background (CMB) maps around known galaxy clusters and groups provides a powerful probe of the distribution of hot gas in these systems via the Sunyaev-Zeldovich (SZ) effect. A stacking analysis allows one to detect the average SZ signal around low mass halos, and to extend measurements out to large scales, which are too faint to detect individually in the SZ or in X-ray emission. In addition, cross correlations between SZ maps and other tracers of large-scale structure (with known redshifts) can be used to extract the redshift-dependence of the SZ background. Motivated by these exciting prospects, we measure the two-point cross-correlation function between a catalog of $sim 380,000$ galaxy groups (with redshifts spanning $z=0.01-0.2$) from the Sloan Digital Sky Survey (SDSS) and Compton-y parameter maps constructed by the Planck collaboration. We find statistically significant correlations between the group catalog and Compton-y maps in each of six separate mass bins, with estimated halo masses in the range $10^{11.5-15.5} M_odot/h$. We compare these measurements with halo models of the SZ signal, which describe the stacked measurement in terms of one-halo and two-halo terms. The one-halo term quantifies the average pressure profile around the groups in a mass bin, while the two-halo term describes the contribution of correlated neighboring halos. For the more massive groups we find clear evidence for the one- and two-halo regimes, while groups with mass below $10^{13} M_odot/h$ are dominated by the two-halo term given the resolution of Planck data. We use the signal in the two-halo regime to determine the bias-weighted electron pressure of the universe: $langle b P_e rangle= 1.50 pm 0.226 times 10^{-7}$ keV cm$^{-3}$ (1-$sigma$) at $zapprox 0.15$.
X-ray emission and the thermal Sunyaev-Zeldovich distortion to the Cosmic Microwave Background are two important handles on the gas content of the Universe. The cross-correlation between these effects eliminates noise bias and reduces observational systematic effects. Using analytic models for the cluster profile, we develop a halo model formalism to study this cross-correlation and apply it to forecast the signal-to-noise of upcoming measurements from eROSITA and the Simons Observatory. In the soft X-ray band (0.5--2 keV), we forecast a signal-to-noise of 174 for the cross-power spectrum. Over a wide range of the scales, the X-rays will be signal-dominated, and so sample variance is important. In particular, non-Gaussian (4-point) contributions to the errors highlight the utility of masking massive clusters. Masking clusters down to $10^{14} M_odot$ increases the signal-to-noise of the cross-spectrum to 201. We perform a Fisher Analysis on the fitting coefficients of the Battaglia et al. gas profiles and on cosmological parameters. We find that the cross spectrum is most sensitive to the overall scale of the profiles of pressure and electron density, as well as cosmological parameters $sigma_8$ and $H_0$, but that the large number of parameters form a degenerate set, which makes extracting the information more challenging. Our modeling framework is flexible, and in the future, we can easily extend it to forecast the spatial cross-correlations of surveys of X-ray lines available to high-energy-resolution microcalorimetry, to studies of the Warm-Hot Intergalactic Medium, and other effects.
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