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Register a new userDirect detection of the kinetic Sunyaev-Zeldovich effect in galaxy clusters
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We report the direct detection of the kinetic Sunyaev-Zeldovich (kSZ) effect in galaxy clusters with a 3.5 sigma significance level. The measurement was performed by stacking the Planck map at 217 GHz at the positions of galaxy clusters from the Wen-Han-Liu (WHL) catalog. To avoid the cancelation of positive and negative kSZ signals, we used the large-scale distribution of the Sloan Digital Sky Survey (SDSS) galaxies to estimate the peculiar velocities of the galaxy clusters along the line of sight and incorporated the sign in the velocity-weighted stacking of the kSZ signals. Using this technique, we were able to measure the kSZ signal around galaxy clusters beyond 3R500. Assuming a standard beta-model, we also found that the gas fraction within R500 is fgas,500 = 0.12 +- 0.04 for the clusters with the mass of M500 ~ 1e14 Msun/h. We compared this result to predictions from the Magneticum cosmological hydrodynamic simulations as well as other kSZ and X-ray measurements, most of which show a lower gas fraction than the universal baryon fraction for the same mass of clusters. Our value is statistically consistent with results from the measurements and simulations and also with the universal value within our measurement uncertainty.
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The masses of galaxy clusters are a key tool to constrain cosmology through the physics of large-scale structure formation and accretion. Mass estimates based on X-ray and Sunyaev--Zeldovich measurements have been found to be affected by the contribution of non-thermal pressure components, due e.g. to kinetic gas energy. The characterization of possible ordered motions (e.g. rotation) of the intra-cluster medium could be important to recover cluster masses accurately. We update the study of gas rotation in clusters through the maps of the kinetic Sunyaev--Zeldovich effect, using a large sample of massive synthetic galaxy clusters ($ M_{vir} > 5times 10^{14} h^{-1}$M$_odot$ at $z~=~0 $) from MUSIC high-resolution simulations. We select few relaxed objects showing peculiar rotational features, as outlined in a companion work. To verify whether it is possible to reconstruct the expected radial profile of the rotational velocity, we fit the maps to a theoretical model accounting for a specific rotational law, referred as the vp2b model. We find that our procedure allows to recover the parameters describing the gas rotational velocity profile within two standard deviations, both with and without accounting for the bulk velocity of the cluster. The amplitude of the temperature distortion produced by the rotation is consistent with theoretical estimates found in the literature, and it is of the order of 23 per cent of the maximum signal produced by the cluster bulk motion. We also recover the bulk velocity projected on the line of sight consistently with the simulation true value.
We present the detection of the kinetic Sunyaev-Zeldovich effect (kSZE) signals from groups of galaxies as a function of halo mass down to $log (M_{500}/{rm M_odot}) sim 12.3$, using the {it Planck} CMB maps and stacking about $40,000$ galaxy systems with known positions, halo masses, and peculiar velocities. The signals from groups of different mass are constrained simultaneously to take care of projection effects of nearby halos. The total kSZE flux within halos estimated implies that the gas fraction in halos is about the universal baryon fraction, even in low-mass halos, indicating that the `missing baryons are found. Various tests performed show that our results are robust against systematic effects, such as contamination by infrared/radio sources and background variations, beam-size effects and contributions from halo exteriors. Combined with the thermal Sunyaev-Zeldovich effect, our results indicate that the `missing baryons associated with galaxy groups are contained in warm-hot media with temperatures between $10^5$ and $10^6,{rm K}$.
We present the detection of the kinetic Sunyaev-Zeldovich effect (kSZE) signals from groups of galaxies as a function of halo mass down to $log (M_{500}/{rm M_odot}) sim 12.3$, using the {it Planck} CMB maps and stacking about $40,000$ galaxy systems with known positions, halo masses, and peculiar velocities. The signals from groups of different mass are constrained simultaneously to take care of projection effects of nearby halos. The total kSZE flux within halos estimated implies that the gas fraction in halos is about the universal baryon fraction, even in low-mass halos, indicating that the `missing baryons are found. Various tests performed show that our results are robust against systematic effects, such as contamination by infrared/radio sources and background variations, beam-size effects and contributions from halo exteriors. Combined with the thermal Sunyaev-Zeldovich effect, our results indicate that the `missing baryons associated with galaxy groups are contained in warm-hot media with temperatures between $10^5$ and $10^6,{rm K}$.
We consider the prospects for measuring the pairwise kinetic Sunyaev-Zeldovich (kSZ) signal from galaxy clusters discovered in large photometric surveys such as the Dark Energy Survey (DES). We project that the DES cluster sample will, in conjunction with existing mm-wave data from the South Pole Telescope (SPT), yield a detection of the pairwise kSZ signal at the 8-13 sigma level, with sensitivity peaking for clusters separated by ~100 Mpc distances. A next-generation version of SPT would allow for a 18-30 sigma detection and would be limited by variance from the kSZ signal itself and residual thermal Sunyaev-Zeldovich (tSZ) signal. Throughout our analysis we assume photometric redshift errors, which wash out the signal for clusters separated by <~50 Mpc; a spectroscopic survey of the DES sample would recover this signal and allow for a 26-43 sigma detection, and would again be limited by kSZ/tSZ variance. Assuming a standard model of structure formation, these high-precision measurements of the pairwise kSZ signal will yield detailed information on the gas content of the galaxy clusters. Alternatively, if the gas can be sufficiently characterized by other means (e.g. using tSZ, X-ray, or weak lensing), then the relative velocities of the galaxy clusters can be isolated, thereby providing a precision measurement of gravity on 100 Mpc scales. We briefly consider the utility of these measurements for constraining theories of modified gravity.
We propose a novel technique to separate the late-time, post-reionization component of the kinetic Sunyaev-Zeldovich (kSZ) effect from the contribution to it from a (poorly understood and probably patchy) reionization history. The kSZ effect is one of the most promising probe of the {em missing baryons} in the Universe. We study the possibility of reconstructing it in three dimensions (3D), using future spectroscopic surveys such as the Euclid survey. By reconstructing a 3D template from galaxy density and peculiar velocity fields from spectroscopic surveys we cross-correlate the estimator against CMB maps. The resulting cross-correlation can help us to map out the kSZ contribution to CMB in 3D as a function of redshift thereby extending previous results which use tomographic reconstruction. This allows the separation of the late time effect from the contribution owing to reionization. By construction, it avoids contamination from foregrounds, primary CMB, tSZ effect as well as from star forming galaxies. Due to a high number density of galaxies the signal-to-noise (S/N) for such cross-correlational studies are higher, compared to the studies involving CMB power spectrum analysis. Using a spherical Bessel-Fourier (sFB) transform we introduce a pair of 3D power-spectra: ${cal C}^{parallel}_ell(k)$ and ${cal C}^{perp}_ell(k)$ that can be used for this purpose. We find that in a future spectroscopic survey with near all-sky coverage and a survey depth of $zapprox 1$, reconstruction of ${cal C}^{perp}_ell(k)$ can be achieved in a few radial wave bands $kapprox(0.01-0.5 h^{-1}rm Mpc)$ with a S/N of upto ${cal O}(10)$ for angular harmonics in the range $ell=(200-2000)$ (abrdiged).
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