Search

We introduce the Planck SZiFi catalogues, a new set of 10 catalogues of galaxy clusters detected through their thermal Sunyaev-Zeldovich (tSZ) signature. The catalogues are produced by applying the SZiFi cluster finder to the Planck PR3 temperature data down to a signal-to-noise threshold of 5. They span three frequency channel combinations (100-857 GHz, 100-545 GHz, and 100-353 GHz) and 7 of them are constructed by spectrally deprojecting the Cosmic Infrared Background (CIB). This approach allows us, for the first time in the context of cluster finding, to carefully assess the impact of the cluster-correlated CIB on the recovered cluster tSZ observables, which we find to be negligible. In addition, we quantify the impact of the relativistic corrections to the tSZ signal, finding them to be at the 5-10% level for the cluster tSZ amplitude but negligible for the signal-to-noise. We compile our catalogues into a single Planck SZiFi master catalogue containing a total of 1499 detections. We cross-match the master catalogue with several external tSZ and X-ray cluster catalogues, setting a lower bound on the purity of our baseline catalogue of 95% and 99% at a minimum signal-to-noise of 5 and 6, respectively. We validate our cluster detection pipeline by applying it to synthetic observations, recovering cluster number counts for which we are able to produce a theoretical prediction that accurately describes them. This validation exercise indicates that our catalogues are well-suited for cosmological inference. The Planck SZiFi master catalogue will become publicly available at github.com/inigozubeldia/szifi/tree/main/planck_szifi_master_catalogue., Comment: 32 pages, 22 figures, submitted to MNRAS

We introduce cosmocnc, a Python package for computing the number count likelihood of galaxy cluster catalogues in a fast, flexible and accurate way. cosmocnc offers three types of likelihoods: an unbinned, a binned, and an extreme value likelihood. It also supports the addition of stacked cluster data, which is modelled consistently with the cluster catalogue. The unbinned likelihood, which is the main focus of the code, can take an arbitrary number of mass observables as input and deal with several complexities in the data, such as variations in the properties of the cluster observable across the survey footprint, the possibility of different clusters having measurements for different combinations of mass observables, redshift measurement uncertainties, and the presence on unconfirmed detections in the catalogue. If there are more than one mass observables, the unbinned likelihood is computed with the backward convolutional approach, a novel approach that is first implemented in cosmocnc. After developing the likelihood formalism and describing its implementation, we validate the code with synthetic Simons-Observatory-like catalogues, finding excellent agreement between their properties and cosmocnc's predictions and obtaining constraints on cosmological and scaling relation parameters featuring negligible biases. cosmocnc is publicly available at github.com/inigozubeldia/cosmocnc., Comment: 22 pages, comments welcome

As demonstrated by Planck, SPT, and ACT, the abundance of Sunyaev-Zeldovich-detected galaxy clusters across mass and redshift is a powerful cosmological probe. Upcoming experiments such as the Simons Observatory (SO) will detect over an order of magnitude more objects than what previous experiments have found, thereby providing an unprecedented constraining potential. However, in order for this potential to be realised, the cluster detection and analysis pipelines will have to be built and understood to a much higher level of accuracy than has been demonstrated to date. Here we discuss ongoing efforts towards the accurate modelling of tSZ cluster counts, focusing on several improvements regarding optimisation bias, covariance estimation, and foreground deprojection, which are implemented in the publicly-available SZiFi package. Next, we briefly discuss the application of these improved cluster detection methods to Planck data. Finally, we introduce cosmocnc, a new cluster number count likelihood code that will be publicly available soon., Comment: To appear in Proc. of the mm Universe 2023 conference, Grenoble (France), June 2023, published by F. Mayet et al. (Eds), EPJ Web of conferences, EDP Sciences

Galaxy clusters detected through the thermal Sunyaev-Zeldovich (tSZ) effect are a powerful cosmological probe from which constraints on cosmological parameters such as $\Omega_{\mathrm{m}}$ and $\sigma_8$ can be derived. The measured cluster tSZ signal can be, however, contaminated by Cosmic Infrared Background (CIB) emission, as the CIB is spatially correlated with the cluster tSZ field. We quantify the extent of this contamination by applying the iterative multi-frequency matched filter (iMMF) cluster-finding method to mock Planck-like data from the Websky simulation. We find a significant bias in the retrieved cluster tSZ observables (signal-to-noise and Compton-$y$ amplitude), at the level of about $0.5\, \sigma$ per cluster. This CIB-induced bias translates into about $20$% fewer detections than expected if all the Planck HFI channels are used in the analysis, which can potentially bias derived cosmological constraints. We introduce a spectrally constrained iMMF, or sciMMF, which proves to be highly effective at suppressing this CIB-induced bias from the tSZ cluster observables by spectrally deprojecting the cluster-correlated CIB at the expense of a small signal-to-noise penalty. Our sciMMF is also robust to modelling uncertainties, namely to the choice of deprojection spectral energy distribution. With it, CIB-free cluster catalogues can be constructed and used for cosmological inference. We provide a publicly available implementation of our sciMMF as part of the SZiFi package., Comment: 21 pages, submitted to MNRAS, comments welcome

Multi-frequency matched filters (MMFs) are routinely used to detect galaxy clusters from CMB data through the thermal Sunyaev-Zeldovich (tSZ) effect, leading to cluster catalogues that can be used for cosmological inference. In order to be applied, MMFs require knowledge of the cross-frequency power spectra of the noise in the maps. This is typically estimated from the data and taken to be equal to the power spectra of the data, assuming the contribution from the tSZ signal of the detections to be negligible. Using both analytical arguments and \textit{Planck}-like mock observations, we show that doing so causes the MMF noise to be overestimated, inducing a loss of signal-to-noise. Furthermore, the MMF cluster observable (the amplitude $\hat{y}_0$ or the signal-to-noise $q$) does not behave as expected, which can potentially bias cosmological inference. In particular, the observable becomes biased with respect to its theoretical prediction and displays a variance that also differs from its predicted value. We propose an iterative MMF (iMMF) approach designed to mitigate these effects. In this approach, after a first standard MMF step, the noise power spectra are reestimated by masking the detections from the data, delivering an updated iterative cluster catalogue. Applying our iMMF to our \textit{Planck}-like mock observations, we find that the aforementioned effects are completely suppressed. This leads to a signal-to-noise gain relative to the standard MMF, with more significant detections and a higher number of them, and to a cluster observable with the expected theoretical properties, thus eliminating any potential biases in the cosmological constraints., Comment: 16 pages, 11 figures, submitted for publication to MNRAS

Matched filters are routinely used in cosmology in order to detect galaxy clusters from mm observations through their thermal Sunyaev-Zeldovich (tSZ) signature. In addition, they naturally provide an observable, the detection signal-to-noise or significance, which can be used as a mass proxy in number counts analyses of tSZ-selected cluster samples. In this work, we show that this observable is, in general, non-Gaussian, and that it suffers from a positive bias, which we refer to as optimisation bias. Both aspects arise from the fact that the signal-to-noise is constructed through an optimisation operation on noisy data, and hold even if the cluster signal is modelled perfectly well, no foregrounds are present, and the noise is Gaussian. After reviewing the general mathematical formalism underlying matched filters, we study the statistics of the signal-to-noise with a set Monte Carlo mock observations, finding it to be well-described by a unit-variance Gaussian for signal-to-noise values of 6 and above, and quantify the magnitude of the optimisation bias, for which we give an approximate expression that may be used in practice. We also consider the impact of the bias on the cluster number counts of Planck and the Simons Observatory (SO), finding it to be negligible for the former and potentially significant for the latter.

CMB lensing is a promising, novel way to measure galaxy cluster masses that can be used, e.g., for mass calibration in galaxy cluster counts analyses. Understanding the statistics of the galaxy cluster mass observable obtained with such measurements is essential if their use in subsequent analyses is not to lead to biased results. We study the statistics of a CMB lensing galaxy cluster mass observable for a Planck-like experiment with mock observations obtained from an N-body simulation. We quantify the bias and intrinsic scatter associated with this observable following two different approaches, one in which the signal due to the cluster and nearby correlated large-scale structure is isolated, and another one in which the variation due to uncorrelated large-scale structure is also taken into account. For our first approach we also quantify deviations from log-normality in the scatter, finding them to have a negligible impact on mass calibration for our Planck-like experiment. We briefly discuss how some of our results change for experiments with higher angular resolution and lower noise levels, such as the current generation of surveys obtained with ground-based, large-aperture telescopes.

This paper discusses the science case for a sensitive spectro-polarimetric survey of the microwave sky. Such a survey would provide a tomographic and dynamic census of the three-dimensional distribution of hot gas, velocity flows, early metals, dust, and mass distribution in the entire Hubble volume, exploit CMB temperature and polarisation anisotropies down to fundamental limits, and track energy injection and absorption into the radiation background across cosmic times by measuring spectral distortions of the CMB blackbody emission. In addition to its exceptional capability for cosmology and fundamental physics, such a survey would provide an unprecedented view of microwave emissions at sub-arcminute to few-arcminute angular resolution in hundreds of frequency channels, a data set that would be of immense legacy value for many branches of astrophysics. We propose that this survey be carried-out with a large space mission featuring a broad-band polarised imager and a moderate resolution spectro-imager at the focus of a 3.5m aperture telescope actively cooled to about 8K, complemented with absolutely-calibrated Fourier Transform Spectrometer modules observing at degree-scale angular resolution in the 10-2000 GHz frequency range. We propose two observing modes: a survey mode to map the entire sky as well as a few selected wide fields, and an observatory mode for deeper observations of regions of specific interest., Comment: 20 pages, white paper submitted in answer to the "Voyage 2050" call to prepare the long term plan in the ESA science programme

This Science White Paper, prepared in response to the ESA Voyage 2050 call for long-term mission planning, aims to describe the various science possibilities that can be realized with an L-class space observatory that is dedicated to the study of the interactions of cosmic microwave background (CMB) photons with the cosmic web. Our aim is specifically to use the CMB as a backlight -- and survey the gas, total mass, and stellar content of the entire observable Universe by means of analyzing the spatial and spectral distortions imprinted on it. These distortions result from two major processes that impact on CMB photons: scattering by electrons (Sunyaev-Zeldovich effect in diverse forms, Rayleigh scattering, resonant scattering) and deflection by gravitational potential (lensing effect). Even though the list of topics collected in this White Paper is not exhaustive, it helps to illustrate the exceptional diversity of major scientific questions that can be addressed by a space mission that will reach an angular resolution of 1.5 arcmin (goal 1 arcmin), have an average sensitivity better than 1 uK-arcmin, and span the microwave frequency range from roughly 50 GHz to 1 THz. The current paper also highlights the synergy of our BACKLIGHT mission concept with several upcoming and proposed ground-based CMB experiments., Comment: Science White Paper submitted in response to the ESA Voyage 2050 call, 20 pages + title page + references

We present a new cosmological analysis of the galaxy clusters in the Planck MMF3 cosmology sample with a cosmic microwave background (CMB) lensing calibration of the cluster masses. As demonstrated by Planck, galaxy clusters detected via the Sunyaev-Zel'dovich (SZ) effect offer a powerful way to constrain cosmological parameters such as $\Omega_{\mathrm{m}}$ and $\sigma_8$. Determining the absolute cluster mass scale is, however, difficult, and some recent calibrations have yielded cosmological constraints in apparent tension with constraints in the $\Lambda$CDM model derived from the power spectra of the primary CMB anisotropies. In order to calibrate the absolute mass scale of the full Planck cluster sample, we remeasure the masses of all 433 clusters through their weak lensing signature in the CMB temperature anisotropies as measured by Planck. We perform a joint Bayesian analysis of the cluster counts and masses taking as input the estimated cluster masses, SZ signal-to-noise ratios, and redshifts. Our analysis properly accounts for selection effects in the construction of the cluster sample. We find $\sigma_8 \left(\Omega_{\mathrm{m}}/0.33\right)^{0.25} = 0.765 \pm 0.035$ and $1-b_{\mathrm{SZ}} = 0.71 \pm 0.10$, where the mass bias factor $1-b_{\mathrm{SZ}}$ relates cluster mass to the SZ mass that appears in the X-ray-calibrated cluster scaling relations. We find no evidence for tension with the Planck primary CMB constraints on $\Lambda$CDM model parameters.

Lensing of the CMB is now a well-developed probe of large-scale clustering over a broad range of redshifts. By exploiting the non-Gaussian imprints of lensing in the polarization of the CMB, the CORE mission can produce a clean map of the lensing deflections over nearly the full-sky. The number of high-S/N modes in this map will exceed current CMB lensing maps by a factor of 40, and the measurement will be sample-variance limited on all scales where linear theory is valid. Here, we summarise this mission product and discuss the science that it will enable. For example, the summed mass of neutrinos will be determined to an accuracy of 17 meV combining CORE lensing and CMB two-point information with contemporaneous BAO measurements, three times smaller than the minimum total mass allowed by neutrino oscillations. In the search for B-mode polarization from primordial gravitational waves with CORE, lens-induced B-modes will dominate over instrument noise, limiting constraints on the gravitational wave power spectrum amplitude. With lensing reconstructed by CORE, one can "delens" the observed polarization internally, reducing the lensing B-mode power by 60%. This improves to 70% by combining lensing and CIB measurements from CORE, reducing the error on the gravitational wave amplitude by 2.5 compared to no delensing (in the null hypothesis). Lensing measurements from CORE will allow calibration of the halo masses of the 40000 galaxy clusters that it will find, with constraints dominated by the clean polarization-based estimators. CORE can accurately remove Galactic emission from CMB maps with its 19 frequency channels. We present initial findings that show that residual Galactic foreground contamination will not be a significant source of bias for lensing power spectrum measurements with CORE. [abridged], Comment: 44 pages, 12 figures

Combining galaxy cluster and void abundances breaks the degeneracy between mean matter density $\Omega_{\rm m}$ and power spectrum normalization $\sigma_8$. In a first for voids, we constrain $\Omega_{\rm m} = 0.21 \pm 0.10$ and $\sigma_8 = 0.95 \pm 0.21$ for a flat $\Lambda$CDM universe, using extreme-value statistics on the claimed largest cluster and void. The Planck-consistent results detect dark energy with two objects, independently of other dark energy probes. Cluster-void studies also offer complementarity in scale, density, and non-linearity - of particular interest for testing modified-gravity models., Comment: 13 pages, 1 figure, 2 tables. ApJL accepted, revised version. Minor changes: added clarifying remarks, discussion on redshift sensitivity and more general models. Results and conclusions unchanged