Introduction to the meeting

• Marco De Petris (ROMA1)

The NIKA2 Sunyaev-Zeldovich Large Program: precise galaxy cluster physics for an accurate cluster-based cosmology

• Laurence Perotto (LPSC - CNRS - Univ. grenoble-Alpes)

Current cosmological studies based on clusters of galaxies are limited by the accuracy with which the mass of these objects can be inferred. The Sunyaev-Zel'dovich (SZ) effect is a direct probe of the thermal pressure of the Intra-Cluster Medium (ICM). When combined with X-ray data, the SZ effect can also provide a valuable measure of the mass of the galaxy clusters under the hydrostatic equilibrium assumption. With an angular resolution comparable to that of the XMM-Newton space observatory, NIKA2 will unveil the pressure distribution of the ICM and will allow the full deployment of combined SZ and X-ray methods to infer the hydrostatic mass. The Guaranteed-Time SZ Large Program (LP-SZ) is dedicated to the high-angular resolution SZ mapping of a representative sample of 45 galaxy clusters drawn from the SZ-selected catalogues of the Planck satellite, or of the Atacama Cosmology Telescope. The LP-SZ sample spans a mass range from 3 to 11x10^{14} M_{sun} and a redshift range from 0.5 to 0.9, extending to higher redshift and lower mass the previous samples dedicated to the cluster mass calibration and universal properties estimation. The main goals of the LP-SZ are the measurement of the average radial profile of the ICM pressure up to R_500 by combining NIKA2 with Planck or ACT data, and the estimation of the scaling law between the SZ observable and the mass using NIKA2, XMM-Newton and Planck/ACT data. Furthermore, combining LP-SZ data with existing or forthcoming public data in lensing, optical/NIR or radio domains, we will build a consistent picture of the cluster physics and further gain knowledge on the mass estimate as a function of the cluster morphology and dynamical state. In this talk, I will present the LP-SZ, the recent results obtained within this framework, the status of the observation and analysis, and the future implication for cosmology with galaxy clusters.

Multi-probe analysis of the galaxy cluster CLJ1227: unveiling systematics in mass estimation

• Miren Muñoz Echeverría (LPSC)

We present a multi-probe analysis of the well known galaxy cluster CLJ1227 as a proof of concept for multi-wavelength studies within the NIKA2 Sunyaev-Zeldovich Large Program (LPSZ). CLJ1227 is a massive and high redshift cluster that has already been observed at several wavelengths. A joint analysis of the thermal SZ (tSZ) effect at millimeter wavelength with the NIKA2 camera and in X-ray with XMM-Newton satellite permits the reconstruction of the cluster’s thermodynamical properties and mass in hydrostatic equilibrium hypothesis. The tSZ results are compared to previous studies on CLJ1227 to quantify possible systematic effects in the data or induced by the data processing. Using the optical CLASH observations we obtain estimates of the lensing mass profile, which can be compared to the hydrostatic mass profiles derived from the tSZ and X-ray analysis. From this we are able to test the hydrostatic equilibrium hypothesis in the cluster. Furthermore, we derive an estimation of the gas mass fraction for the cluster. In addition, using interferometric NOEMA observations at 70 GHz we study the cluster core in detail. Finally, from radio data we study contributions from non-thermal pressure. This multi-probe analysis allows us to better understand the dynamical state of such a cluster, which is both spherically symmetric and disturbed at the cluster core.

Impact of the complex morphology of a cluster on thermodynamical quantities: PSZ2G091

• Emmanuel Artis (LPSC)

PSZ2G091 is a massive galaxy cluster with M500= 7.43x10^14 Msun at z = 0.816. This object exhibit a complex morphology with a clear bimodality observed in X-rays. However, it was detected and analyzed in the Planck sample as a single, spherical cluster. This simplified model can lead to miscalculations of thermodynamical quantities, like the pressure profile. The effect then propagates on Y500 measurements and impacts the selection function of SZ detected clusters. As future SZ cluster samples will detect more and more objects at higher redshifts (where we expect the fraction of merging objects to be higher), it is crucial to quantify this systematic. In this presentation, we use high-resolution observations of PSZ2G091 by the NIKA2 camera to integrate the morphological characteristic of the cluster in our modeling. We then compare these results with the spherical assumption and extrapolate the impact of this systematic on current and future samples.

A new software to measure pressure profiles from SZ observations

• Florian Kéruzoré (LPSC, Grenoble, France)

Galaxy clusters and their distribution in the Universe are a powerful cosmological probe, that can be used at many different wavelengths to set constraints on cosmological parameters. Recent CMB surveys such as Planck, SPT and ACT have led to numerous such studies, by enabling the detection of large samples of nearly mass-selected galaxy clusters detected through the Sunyaev-Zeldovich (SZ) effect. The exploitation of such surveys is limited by its reliance on a prior knowledge of the physical properties of galaxy clusters. Among these properties is the mean pressure profile of galaxy clusters, that is needed for the construction of cluster catalog from millimeter observations. Thanks to the tight link between the observed SZ surface brightness and the pressure distribution in galaxy clusters, high-resolution millimeter instruments are an excellent tool to get precise measurements of this distribution. We have developed a new software to perform the measurement of galaxy cluster pressure profiles from high-resolution SZ observations. One of the key advantages of the code is the possibility to use binned, non-parametric pressure profiles, enabling possible detections of pressure features better than smooth functions such as the traditionally used generalized Navarro-Frenk-White profile. Another major upside is the software's performance, enabling the extraction of the pressure profile and associated confidence intervals via MCMC sampling in times as short as a few minutes. The code allows the user to take into account various features of millimeter observations, such as PSF convolution, pipeline filtering, correlated residual noise, and point source contamination, in a forward-modelling approach. In this talk, I will present the code and its validation on various realistic synthetic maps, of ideal spherical clusters, as well as of realistic, hydrodynamically simulated objects. We plan to publicly release the software in the coming months.

JoXSZ: Joint X-SZ fitting code for galaxy clusters

• Fabio Castagna (INAF - Osservatorio Astronomico di Brera)

Abstract:The thermal Sunyaev-Zeldovich (SZ) effect and the X-ray emission offer separate and highly complementary probes of the thermodynamics of the intracluster medium. I will present JoXSZ, the first publicly available code designed to jointly fit SZ and X-ray data coming from various instruments to derive the thermodynamic profiles of galaxy clusters. JoXSZ follows a fully Bayesian forward-modelling approach and improves upon most current and not publicly available analyses. JoXSZ accounts for beam smearing and data analysis transfer function and adopts flexible parametrization for the thermodynamic profiles. The code is written in Python and the users are free to customise their analysis in accordance with their needs and requirements. JoXSZ is publicly available on GitHub (https://github.com/fcastagna/joxsz).

Non-thermal pressure support in the MOO J1142+1527 cluster @ z~1.2

• Iacopo Bartalucci (INAF)

MOO J1142+1527 is the most massive, M500= 6×1014 Msun at z = 1.2, IR-selected cluster detected in the MaDCoWS survey. According to the ΛCDM scenario, this type of object is expected to be extremely rare i.e. ∼ 7 objects as massive at z > 1.2 according to the Planck cosmology. The exceptional nature of this object and the large multi-wavelength data coverage represent an ideal laboratory to test our understanding of structure formation and evolution at such unprecedented redshift. Building on the results of the work that combines Chandra and NIKA2, we perform for the first time combined Xray-SZ analysis using a deep XMM observation tailored to obtain results up to R500. We present for the first time the investigation of the dynamical properties of this object up to R500 and the determination of the non-thermal pressure support at such redshift, combining high-resolution X-ray and SZ datasets.

Mapping the intracluster medium temperature in the era of NIKA2 and MUSTANG-2

• Florian Ruppin (MIT)

Up until recently, mapping the temperature of the intracluster medium (ICM) required high signal-to-noise observations in the X-ray domain to fit spectra extracted from several independent regions of the ICM. However, as the exploration of cluster formation extends to high redshifts, the cost of these observations becomes prohibitive. It is therefore essential to develop new procedures to characterize temperature fluctuations within the ICM at high redshift. In this context, high angular resolution SZ observations have a major role to play. Because of their respective dependence on the density and pressure of the ICM, the combination of X-ray and SZ observations allows us to map the temperature of the ICM without having to consider spectral information in X-ray data. With both a wide field of view and a high angular resolution, NIKA2 and MUSTANG-2 are very well suited instrument to map the SZ signal of high redshift clusters up to $R_{500}$. Moreover, they cover different frequency bands that can be exploited to estimate the different components of the SZ effect. Among them, the rSZ effect directly depends on the ICM temperature. Thus, the 2020 decade ushers in a new era for the characterization of high redshift clusters in which all thermodynamic properties of the ICM, including temperature, can be estimated via SZ observations alone. I will present recent results from two independent open time programs conducted with NIKA2 at the IRAM 30-m telescope. The first one takes advantage of the complementary of X-ray and SZ observations to map the ICM temperature of IR-detected galaxy clusters at z > 1 using $Chandra$ and NIKA2 data. The second one intends to perform the first ICM temperature mapping based on the resolved detection of the rSZ effect in the massive cluster RXJ J1347−1145 from the combination of NIKA2 and MUSTANG-2 data.

Measuring the Relativistic Sunyaev-Zeldovich Effect in Cluster RXJ1347.5-1145

• Victoria Butler (Rochester Institute of Technology)

Understanding the thermodynamic evolution of the intra-cluster medium (ICM) is vital for future cluster cosmological studies. Current studies are limited by the scatter intrinsic in observables such as X-ray luminosity and temperature. One key way to reduce this scatter is to externally calibrate the ICM temperature using an alternate technique. In recent years, the Sunyaev-Zeldovich (SZ) Effect has emerged as a viable complement to existing cluster surveys due to its redshift independence and linear dependence on the ICM density. This talk will describe a method for measuring the cluster temperature using the Relativistic SZ (rSZ) Effect which can be used to calibrate X-ray measurements and reduce the uncertainty on cosmological parameters. We use three *Herschel*-SPIRE bands with centers at wavelengths of roughly 250, 350 and 500 microns to measure the rSZ effect in the galaxy cluster RX J1347.5-1145, and estimate the Compton *y* and temperature of the ICM. The SZ effect at SPIRE frequencies is heavily correlated with the cosmic infrared background (CIB), cirrus, and other far-infrared emitters. Additionally, the SPIRE instrument is confusion-limited making it even more difficult to separate individual constituents. We efficiently model the CIB and other map components, as well as estimate the SZ spectra amplitude using the crowded field point source cataloger, PCAT, reducing one of the biggest limitations on high frequency rSZ measurements. The SZ effect spatial profile is estimated from Bolocam and *Planck* observations of the cluster. To calculate the uncertainty from other sub-mm components and understand the bias introduced by our pipeline, we create mock SPIRE 3-band maps. These are used with the PCAT SZ amplitude estimates to perform a maximum likelihood analysis on a grid of potential Compton *y* and temperature values. The method used to estimate rSZ to low significance in this cluster will be applied to a larger sample of 40 clusters to get an unambiguous detection.

Relativistic SZ maps and electron temperature spectroscopy

• Mathieu Remazeilles (University of Manchester)

While third-generation CMB experiments have allowed to release the first maps of the Compton-$y$ distortion due to thermal Sunyaev-Zeldovich (SZ) effect, next-generation CMB experiments should allow to map also the electron gas temperature, $T_{\rm e}$, across the sky through the detection of relativistic corrections to the thermal SZ effect. We will discuss about the experimental requirements to break the $y$-$T_{\rm e}$ degeneracy of the observed SZ intensity, and propose a new component separation approach based on moment expansion to disentangle the $y$ and $T_{\rm e}$ observables of the relativistic SZ effect while mitigating foregrounds. We will show that this approach offers a new spectroscopic view of the galaxy clusters not only across frequencies but now also across temperatures. We will also show how the relativistic electron temperature power spectrum provides a new cosmological observable which could complement the Compton-$y$ map power spectrum to break some of the parameter degeneracies in future cosmological SZ analyses.

Revisiting the Planck detected multiple-cluster system PLCK G214.6+36.9

• E. Lecoq

Several hundreds of clusters of galaxies have been discovered in the Planck data via the Sunyaev-Zel'dovich (SZ) effect. Among the first detected SZ sources confirmed with XMM-Newton, two were associated with multiple cluster systems. We will present a comprehensive X-ray analysis of the three clusters constituting the multiple system PLCK G214.6+36.9. Combined with the analysis of the associated VLT/VIMOS data, we find that PLCK G214.6+36.9 is most likely the projection of an individual cluster and a cluster pair.

Sunyaev Zel'dovich effect in galaxy clusters cavities: thermal or non-thermal origin?

• Paolo Marchegiani (Universita' Roma Sapienza)

Several galaxy clusters host x-ray cavities, often filled with relativist electrons emitting in the radio band. In the cluster MS 0735.6+7421 the cavities have been detected through the Sunyaev Zel'dovich (SZ) effect, but it has not been possibile to determine if this effect is thermal (produced by a very high temperature gas filling the cavity) or non-thermal (produced by the relativistic electrons producing the diffuse radio emission detected in the cavity). In this talk we discuss the role of the density of the high temperature gas inside the cavity in determining whether the dominant SZ effect is the thermal or the non-thermal one, and how it can be possible to distinguish between the two possibilities.

Sunyaev Zel’dovich high resolution view of filamentary structures between galaxy clusters pairs

• Federico Radiconi (Sapienza, University of Rome)

It is well known that about half of the baryons in the Universe must be in the galaxy clusters outskirts and in the form of hot and low-density filaments connecting galaxy clusters. Due to the low density, most of this filamentary plasma can not be detected by X-ray observatories. In particular cases of low redshift cluster pairs in the pre-merging phase, the Sunyaev Zel'dovich (SZ) effect can be used to observe the inter-cluster regions and detect the imprint of missing baryons. The Abell399-401 (A399-401) system is the perfect laboratory to test our ability to detect filamentary structures via the SZ effect with $< \sim 1^{\prime}$ angular resolution. This pair has been well studied at several frequencies: it exhibits double radio-halos, an excess of X-ray emission in the inter-cluster region and a synchrotron radio ‘ridge’ connecting the two clusters. Moreover the Planck satellite provided the first SZ detection of the gas between A399-401 despite the poor angular resolution ($\sim 10^{\prime}$) of its SZ map. We have used an Atacama Cosmology Telescope (ACT) and Planck satellite Compton-$y$ map ($1.65^{\prime}$ angular resolution) that combines ACT data from 2008 to 2019 with Planck maps and MUSTANG-2 at the Green Bank Telescope data (9$^{\prime \prime}$ angular resolution) to study the A399-401 system in detail. We present the data analysis and results.

Morphological analysis of SZ and X-ray maps of galaxy clusters with Zernike polynomials

• Valentina Capalbo (Sapienza, Università di Roma)

The study of the morphology of multiwavelength maps of galaxy clusters is largely used to evaluate, as possible, their dynamical state. We report about a new method of morphological analysis which consists in analytically modeling the maps with Zernike polynomials (ZPs), a complete basis of orthogonal functions defined on a unit circle. By using several ZPs it is possible to efficiently model the different shapes of the maps inside a circular aperture, highlighting the presence of inhomogeneities and/or small-scale structures that could be related to dynamically disturbed clusters. We have validated the method on mock high-resolution Compton maps (i.e. y-maps) for synthetic galaxy clusters in THE THREE HUNDRED catalogue. We verify that the contribution of the different ZPs in modelling the maps, quantified with a single parameter, results in a valuable tool to recognize various morphologies, and it is also correlated with a proper 3D dynamical-state indicator available for the synthetic clusters. We also show the early results of this analysis applied on real maps of clusters observed by the Planck satellite. We select a sample of low-redshift (z < 0.1) clusters in the Planck-SZ catalogue and model their y-maps with ZPs, inside a circular aperture of radius equal to R500. In the same way, we also analyse simulated Planck y-maps generated for the synthetic THREE HUNDRED clusters. Hence, we search for a correlation, if any, between the morphological analysis with ZPs and the proper dynamical classification of those simulated objects. The results allow us to evaluate the capability of the method to recognize different dynamical populations in the sample of real Planck-selected clusters. We also report about the preliminary results of the Zernike fitting on mock X-ray maps of the THREE HUNDRED clusters.

Multi-Wavelength Galaxy Cluster Cosmology with the South Pole Telescope and the Dark Energy Survey

• Sebastian Bocquet (LMU Munich)

The sample of galaxy clusters selected by the South Pole Telescope (SPT, combining the SPT-SZ and SPTpol surveys) now exceeds a thousand objects. The weak-lensing based mass calibration using Dark Energy Survey (DES) Y3 data will be better than 5%. The joint analysis of the cluster abundance and weak-lensing mass calibration is therefore expected to provide significantly tighter cosmological constraints than the current state of the art. In my talk, I will review the SPT cluster cosmology and mass calibration program. I will focus on the almost completed weak-lensing analysis using DES Y3 data and highlight the current status of the ongoing cosmological analysis.

Cosmology with galaxy clusters: impact of theoretical and observational systematic uncertainties.

• Laura Salvati

Galaxy clusters are a powerful cosmological probe, being able to track the evolution of large scale structure in the latest Universe. In this talk I will focus on how the modelling of the different ingredients entering the analysis (namely the mass-observable relation and the halo mass function) can impact the accuracy and precision of cosmological constraints inferred from galaxy clusters. I will start with a new analysis of clusters detected in mm wavelengths by the Planck satellite, highlighting the need of an improved description and calibration for the mass-observable relation. I will also show an independent point of view on the mass calibration problem, through a novel, still undergoing, analysis based on the combination of Planck and South Pole Telescope cluster catalogs. I will conclude my talk focusing on how to improve our analysis in view of future cluster surveys. In particular, I will show how the calibration of the halo mass function can strongly impact the results on cosmological parameters. This talk will be mainly based on the following papers: A&A 614, A13 (2018), A&A 626, A27 (2019), A&A 643, A20 (2020).

Joint contraints on the galaxy cluster pressure profile from Planck and SPT-SZ

• Jean-Baptiste Melin (CEA Paris-Saclay)

We present the average pressure profile of the 2500d South Pole Telescope galaxy cluster catalogue measured in the Planck and SPT-SZ data jointly. The joint measurement is performed in Fourier space for the first time and takes advantage of the high resolution of SPT (1.75 arcmin beam) and the observation of large angular scales by Planck (> 30 arcmin) simultaneously. The redshift leverage of the catalogue allows to study the evolution of the profile. We also constrain the profile shape in the outskirts.

Removing the giants and learning from the crowd: a new SZ power spectrum method and revised Compton y-map analysis

• Aditya Rotti (Jodrell Bank Centre for Astrophysics, University of Manchester)

The Sunyaev-Zeldovich (SZ) effect provides a powerful cosmological probe, which traditionally is approached independently as cluster number count (CNC) or power spectrum (PS) analysis. Here, we devise a new method for analysing the y-map by introducing the survey completeness function, conventionally only used in the CNC analysis, in the yy-PS modeling. This provides a systematic method, based mainly on SZ observables, for obtaining two complementary y-maps, one incorporating detected/resolved clusters and the other relying only on diffuse/unresolved SZ contributions. We use the catalogue of clusters obtained in the Planck CNC analysis to define the completeness function linking these two y-maps. The split depends on the chosen signal-to-noise detection threshold, which we vary in our discussion. We carefully propagate the effect of completeness cuts on the non-Gaussian error contributions in the yy-PS analysis, highlighting the benefits of masking massive clusters. Our analysis of the Planck yy-PS for the unresolved component yields a mass bias of b = 0.15 ± 0.04, consistent with the standard value (b ≈ 0.2), in comparison to b = 0.4 ± 0.05 for the total yy-PS. We find indications for this drift being driven by the CIB-tSZ cross correlation, which dominantly originates from clusters in the resolved component of the y-map. Another possible explanation is the presence of a mass-dependent bias, which has been theoretically motivated and can be quantified with our novel method. We furthermore find first hints for the presence of the 2-halo terms in the yy-PS. Finally, the proposed method provides a new framework for combining the complementary information of the CNC and PS analyses in upcoming SZ surveys.

Pressure profiles of galaxy clusters using Planck and ACT

• Etienne Pointecouteau (IRAP)

The pressure of hot gas in groups and clusters is directly linked to the total mass of the halo and several other thermodynamical properties. We have investigated a sample of 31 clusters detected in both the Planck and ACT-MBAC surveys. We reconstructed the average pressure profile over our sample making use of both Planck coverage of large scales and the ACT higher spatial resolution. Our profile covers a radial range going from 0.04 to 2.5xR500. It improves upon previous pressure-profile reconstruction based on SZ measurements. It is compatible, as well as competitive, with constraints derived from joint X-ray and SZ analysis. This work demonstrates the possibilities offered by the combination of multiple SZ experiments with different spatial resolutions and spectral coverages, such as ACT and Planck.

Pressure profiles of galaxy cluster from SPT and Planck observations.

• Filippo Oppizzi (Istituto Nazionale di Fisica Nucleare)

We present a full set of numerical tools to extract Galaxy Cluster pressure profiles from the joint analysis of Planck and South Pole Telescope (SPT) observations. Pressure profiles are powerful tracers of the thermodynamical properties and the internal structure of the clusters. Observations of nearby galaxy clusters show a remarkable self-similarity in the shape of the radial pressure profiles. This suggests that the intra-cluster gas resides in Hydrostatic Equilibrium within a self-similar gravitational potential. This relation may break in case of significant deviation from equilibrium, e.g. due to AGN feedback or mass accretion. Tracing the pressure over the cosmic times allows to constraints the evolution of the cluster structure and the contribution of astrophysical phenomena. SPT and Planck are complementary to constrain the cluster structure at various spatial scales. The high sensitivity of the Planck High-Frequency Instrument makes it ideal to observe the faint peripheries, while with its 1.75 arcmin resolution SPT can resolve the innermost regions. The SPT cluster catalogue from the 2500 square degree survey counts 677 cluster candidates up to redshift 1.7 with $M_{500}\geq 2\times10^{14} M_\odot$. It is a nearly mass limited sample, an ideal benchmark to test cluster evolution. We developed a pipeline to first separate the cluster signal from the background (CMB) and foreground (galactic emission) components and then jointly fit a parametric Nagai profile models on a combination of Planck and SPT data. In this work we validate our algorithm on a sub-sample of 6 clusters, comparing the results with the profiles obtained from X-ray observations with XMM-Newton. We check the consistency of the two observables, and we exploit the high resolution of X-ray data to study the impact of cluster substructure on their relation.

The $Y_{500}-M_{500}$ scaling relation from the NIKA2 SZ Large Program

• Florian Kéruzoré (LPSC, Grenoble, France)

The abundance of galaxy clusters in mass and redshift is a powerful cosmological probe, that enables the measurement of cosmological parameters in many parts of the electromagnetic spectrum. One of the key elements needed to perform the cosmological exploitation of a cluster survey is the relation between the survey observable and cluster masses. Among these observables, the integrated Compton parameter :math:`Y` is an observable of Sunyaev-Zeldovich (SZ) surveys, that tightly correlates with the thermal energy content of galaxy clusters, and therefore with their mass. The relation between the Compton parameter and the mass within $R_{500}$ is one of the goals of the NIKA2 SZ Large Program (LPSZ), also presented in this conference. In this talk, I will present ongoing studies to forecast the constraining power of this LPSZ, using mock simulated datasets that mimic the large program sample, selection function, and typical uncertainties on $Y_{500}$ and $M_{500}$ obtained for analyses of individual clusters.

Cosmology with the SZ spectrum: measuring the Universe’s temperature with galaxy clusters

• Gemma Luzzi (ASI Space Science Data Center)

The hot gas in clusters of galaxies creates a distinctive spectral distortion in the cosmic microwave background (CMB) via the Sunyaev-Zel'dovich (SZ) effect. The spectral signature of the SZ can be used to measure the CMB temperature at cluster redshift (T_CMB(z)) and to constrain the monopole of the y-type spectral distortion of the CMB spectrum. In this work, we start showing the measurements of T_CMB(z) for a sample extracted from the Second Catalog of galaxy clusters produced by Planck (PSZ2) and containing 75 clusters selected from the Heritage project of the ESA X-ray satellite XMM-Newton. Then we show the forecasts for future CMB experiments about the constraints on the monopole of the y-type spectral distortion of the CMB spectrum via the spectrum of the SZE.

Cosmology with cluster sizes: measuring the Hubble constant from Planck and XMM-Newton observations of galaxy clusters.

• Federico De Luca (Istituto Nazionale di Fisica Nucleare)

The most recent analyses of the expansion rate ($H_0$) of the Universe have approached the one-per cent accuracy during the last two decades. At that precision, however, early-Universe $H_0$ inferred from the Cosmic Microwave Background (CMB) and local estimation from cosmic distance ladder (Cepheid plus SNIa) significantly differ from one another. Galaxy clusters are alternative cosmic distance rulers that can help to enlighten the CMB-Cepheid tension on the value of the Hubble Constant. Taking advantage of the different dependence with the integrated density of the Intra-Cluster Medium (ICM) between the X-ray bremsstrahlung radiation (quadratic) and the thermal Sunyaev- Zel'dovich effect (tSZ, linear), it is possible to deduce the angular diameter distance of clusters --and the underlying cosmological parameters-- from the ratio of the X-ray surface brightness and the tSZ millimetre optical depths. We apply this technique to infer H0 from XMM-Newton and Planck observations of the CHEX-MATE cluster sample, a large tSZ signal-to-noise ratio limited sample of 120 galaxy clusters in the redshift range [0,0.6]. With respects to earlier results based on the Planck Early Release Compact SZ Source Catalogue, the size and selection function of this new sample will allow us in particular to better assess the systematics of the method, including some observational biases or the impact of cluster morphologies.

Constraining cosmological parameters and hydrostatic mass bias with the gas mass fraction in galaxy clusters

• Raphaël Wicker (IAS)

I will present my work on the use of the gas mass fraction in galaxy clusters as a cosmological probe as well as a probe for baryonic effects in these systems. Using X-ray follow-up observations of galaxy clusters, for instance those of the *Planck* Early SZ (ESZ) sample which has been observed with *Chandra* and XMM-*Newton*, it is possible to constrain the universal baryon fraction $\Omega_b/\Omega_m$, as well as other parameters like the matter density $\Omega_m$, the Hubble parameter $h$ or the Equation of State of Dark Energy $w$. The gas mass fraction in clusters is also sensitive to baryonic effects that need to be taken into account, and that translate into nuisance parameters. Two of them are the depletion factor $\Upsilon$, describing how baryons are depleted in clusters with respect to the universal gas fraction, and the hydrostatic mass bias $B = 1-b$, expressing the fact that the mass is deduced from X-ray observations under the hypothesis of hydrostatic equilibrium. I will show my preliminary results, obtained using *Planck* ESZ clusters, on both cosmological and cluster parameters. I will notably discuss the investigation on a possible redshift dependence of the mass bias, which is considered to be non-existent in hydrodynamic simulations based on $\Lambda$-CDM, and compare my results with other studies.

tSZ in high ell CMB data as cosmological probe: SPT+Planck

• Marian Douspis (IAS)

Small scale CMB data contain a lot of cosmological information hidden in the different components : primordial CMB, tSZ effect, kSZ effect, CIB. Standard analyses assume templates for non primordial CMB component and lose the cosmological signature of large scale structures contained in secondary anisotropies. I will present a new analysis of SPT data at small scales where the tSZ spectrum is derived from the halo model and bring additional constraints. I will show the cosmological and scaling relation parameter constraints obtained by combining SPT CMB data and Planck tSZ measurements.

Testing generalized scalar-tensor theories of gravity with the Sunyaev - Zel’dovich effect (pressure profile) of the galaxy clusters

• Balakrishna Sandeep Haridasu (SISSA)

Degenerate higher-order scalar-tensor (DHOST) theory is the most general scalar-tensor theory, which can be considered as a generalized framework for testing gravity. DHOST theory introduces modifications to $\Lambda$CDM in the background evolution as well as in the small-scale to the gravitational potential in static systems such as galaxy clusters. Assessing these small-scale predictions provides complimentary testing grounds for modifications to GR and so are of utmost importance. To this end, we utilize the well-compiled X-COP catalog consisting of 12 clusters with both the Sunyaev-Zeldovich (SZ) pressure and the X-ray temperature measurements in the radius range of 0.02 Mpc $\leq$ r $\leq$ 2 Mpc for each of the individual clusters. We perform a fully Bayesian analysis modeling NFW mass profile and allowing for the extra degrees of freedom(s), to constrain the DHOST parameter(s) which modifies the hydrostatic equilibrium. Carefully selecting suitable clusters to present our results, we find a mild to moderate, i.e, $\sim 2\sigma$ significance for a deviation from the GR scenario. However, in a comparison of Bayesian evidence, we find that GR remains to be the preferred theory of gravity, while the modifications are not ruled out. While individual clusters do not immediately suggest a modification to GR, we find that a tentative redshift-dependent behavior could be observed at a larger significance. This indeed makes it essential to test the current formalism against larger well-observed samples such as the NIKA2 SZ large program consisting of a larger sample size of 45 clusters, in a larger redshift range.

Galaxy cluster cosmology with the future Euclid sample

• Emmanuel Artis (LPSC)

The upcoming Euclid survey will increase the number of optically detected galaxy clusters by several orders of magnitude. In this work, we present a pipeline for the cosmological analysis of the future Euclid sample of galaxy clusters. We propose a framework including individual lensing mass estimates for the future galaxy cluster sample obtained with matched filtering. This method allows a joint calibration of the cosmological and scaling relation parameters, with the correlation between the richness and lensing mass estimates constrained blindly. We forecast Euclid's performances with this method for different cosmological scenarios (LambdaCDM, w0waCDM) and analyze the relative importance of the sources of uncertainty for a catalog of this size. Using a realistic selection function, we obtained competitive constraints, with the budget of errors dominated by halo mass function uncertainties and the observable-mass relation.

Calibrating Weak Lensing Biases in Galaxy Clusters

• Carlo Giocoli (INAF - OAS Bologna / Istituto Nazionale di Fisica Nucleare)

Recovering the projected mass density distribution of galaxy clusters represents one of the most important steps for future wide-field surveys. This will allow us to use clusters as a cosmological tool by measuring their abundance and clustering as a function of mass and redshift. In this talk, I will present the calibration of the weak lensing mass bias simulating space-based observations. The lens clusters are build up from the mass maps of the large data-set simulations of the 300 project. Obtaining the cluster-halo properties adopting a parametric method presents as a fast and efficient method; however, the mass and the concentration obtained are biased with respect to the true ones. Knowing with per cent accuracy the biases and distributions with regard to the truths will allow us to mitigate the systematics and uncertainties in future cluster surveys maximising the return of the observational experiment.

The LPSZ-CLASH galaxy cluster sample: combining lensing and hydrostatic mass estimates

• Miren Muñoz Echeverría (LPSC)

Starting from the clusters presented in the NIKA2 Sunyaev-Zeldovich Large Program (LPSZ) we have selected a common sample with the CLASH (Cluster Lensing And Supernova survey with Hubble) lensing data. For the LPSZ clusters we dispose both of high resolution thermal SZ and XMM-Newton observations from which hydrostatic mass estimates can be derived. In addition, the CLASH dataset provides lensing convergence maps that can be converted in lensing estimates of the total mass of the cluster. The study of one dimensional mass profiles obtained with these observables allows us to estimate systematics in the mass reconstruction (related to the observables, assumptions and/or modeling), as well as the dependency on the dynamical state of the cluster. Two-dimensional analysis of the maps can reveal substructures in the cluster and, therefore, inform us about the physical properties of each system. Moreover, we are able to study the hydrostatic mass to lensing mass bias, across different morphology and redshift clusters to give more insight about the hydrostatic mass bias.

Constraining the nature of dark matter through joint X-ray/SZ data

• Dominique Eckert (Department of Astronomy, University of Geneva)

The LambdaCDM model of cosmology makes clear predictions on the shape of collapsed halos in the Universe. The radial mass density profiles should follow a universal form across a wide range of halo masses and redshifts. Deviations from the predicted universal profile would provide us clues on fundamental properties of dark matter particles (e.g. self-interaction cross section, warm dark matter mass) and on any modification of the laws of gravity on large scales. Under the hydrostatic equilibrium assumption, precise constraints on the shape of the mass profiles can be obtained from a joint analysis of X-ray and SZ data. I will discuss how this technique can be used to determine the shape of the mass profiles across a wide radial range in the X-COP sample. The resulting profiles will then be used to set new constraints on the fundamental properties of dark matter.

X-ray, SZ and dark matter in galaxy clusters

• Stefano Ettori (INAF OA Bologna)

Galaxy clusters are dark-matter dominated systems enclosed in a volume that is a high-density microcosm of the rest of the universe. I will present the most recent results on the distribution of their gravitating and baryonic mass obtained from our projects XMM-Newton Cluster Outskirts Project (X-COP) and CLASH, and how we will improve these constraints with our ongoing XMM-Newton Heritage Cluster Project (CHEX-MATE; http://xmm-heritage.oas.inaf.it/), highlighting the role of X-ray (and SZ data) in resolving the astrophysics of the most massive collapsed halos in the universe and in studying the interplay between the hot plasma and the dark matter. I will conclude by discussing the role that the next generation of X-ray observatories (like Athena) will play to construct a consistent picture of the formation and composition of galaxy clusters.

Surface brightness profiles of the CHEX-MATE galaxy cluster sample

• Iacopo Bartalucci (INAF)

Galaxy clusters assembly through a hierarchical merging scenario. These processes leave an imprint on the gas which fills the cluster volume, namely the ICM. This component retains vital information on the cluster formation history. X-ray surface brightness profiles are the most simple and direct tool to probe this component and their properties have been extensively studied in the literature, but for limited and/or biased samples. The advent of SZ all sky surveys allowed us to construct unbiased and representative sample of cluster. We present the statistical properties of the surface brightness profiles of a representative sample of 118 clusters observed with high-quality and homogeneous XMM observations. We leverage this sample by studying for the first time the intrinsic scatter of the profiles for a real cluster population, contrasting our results with simulations. We also investigated the amount of dishomogeneity in the gas due to assembly processes in a unprecedented redshift and mass range.

2D thermodynamic maps: dynamical state, scatter, and systematics

• Lorenzo Lovisari

The ICM often shows significant two-dimensional structure generated by mergers and/or AGN feedback. The presence of temperature and density inhomogeneities can cause biases in the determination of the azimuthal profiles (key inputs in the mass estimate from X-ray analysis), and so on the X-ray measured mass distribution. Thus, the more disturbed the cluster is, the more underestimated the X-ray cluster mass is expected to be. Thanks to the high quality X-ray data available for the CHEX-MATE clusters we are in the position to obtain accurate thermodynamic 2D maps and investigate the systematics associated with the inhomogeneous gas distribution. We analyzed a pilot sample of 25 clusters to obtain information about the dynamical state of the clusters and to access the systematic errors in cluster mass measurements due to departures from HE. In the talk I will show how the maps can be used to complement the standard morphological analysis and to selectively remove the regions that significantly deviate from the azimuthal average value.

The dynamical state of the galaxy clusters in the CHEX-MATE sample

• Maria Giulia Campitiello (Unibo/INAF-OAS)

The characterisation of the dynamical state of clusters is crucial for both astrophysical and cosmological studies. On the one hand, the most relaxed systems should provide the cleanest reconstruction of the cluster’s intrinsic properties. On the other hand, disturbed systems are expected to bias (even significantly) this reconstruction. We use an analysis of the morphology of the X-ray emission, to assess the dynamical state of the clusters of the CHEX-MATE sample. This large, unbiased, signal-to-noise limited sample is composed of 118 objects and is built to become the reference for clusters in the local volume and in the high mass regime. With this study, we test the ability of a set of morphological parameters (concentration, centroid shift, smoothness, asymmetry, ellipticity and power-ratios) to determine the degree of relaxation or disturbance of clusters and we check our results applying the same procedure to a sample of simulated objects provided the Three Hundred collaboration. We present preliminary results of our analysis and a first assessment of the dynamical state in CHEX-MATE.

Tens of thousands of clusters of galaxies among few million X-Ray sources on the SRG/eRosita map of the whole sky: synergy and competition of X-Ray and microwave sky surveys

• Rashid Sunyaev (Space Research Institute, Moscow and Max Planck Institute for Astrophysics)

SRG spacecraft with eRosita and ART-XC X-ray telescopes is finishing the third all-sky survey, mapping millions of AGNs and quasars up to redshift z=6.2, hundreds of thousands of stars, and tens of thousands of extended X-Ray sources (mainly clusters of galaxies). We discover every day more than 5 celestial objects which increased during half a year their brightness more than 10 times. Some of them are good TDE candidates, some are flaring stars and AGNs. I plan to discuss the progress in X-ray observations of clusters of galaxies, including examples when current X-Ray and microwave sky surveys are providing useful information on the physical properties of the detected clusters of galaxies.

Chandra Observations of the Planck ESZ Sample: A Re-Examination of Masses and Mass Proxies

• Felipe Andrade-Santos (Center for Astrophysics | Harvard & Smithsonian)

Galaxy clusters reside in the highest ranges of the halo mass function. In the standard $\Lambda$CDM cosmology, massive halos form by the accretion of smaller sub-clumps. Under the influence of gravity, uncollapsed and collapsed sub-clumps fall into larger halos and, occasionally, objects of comparable mass merge with one another. A well established relation between the cluster mass and its observables (such as X-ray luminosity, gas temperature etc) is crucial to any work that explores the theoretical relation between the number density of collapsed halos (the mass function) and the underlying cosmological parameters. The second Planck catalogue (PSZ2), detected 1653 cluster candidates. The vast majority (>1200) of these candidates have been confirmed, making the PSZ2 catalog a reference for cluster studies. Among the many quantities provided by the PSZ2 catalog for each cluster, the mass estimate is arguably the most important. Using Chandra observations, we derived the $\rm Y_X$ proxy and associated total mass measurement, $\rm M_{Y_X}$, for 147 clusters with $z$ < 0.35 from the Planck Early Sunyaev-Zel’dovich catalog, and for 80 clusters with $z$ < 0.22 from an X-ray flux-limited sample. We re-extracted the Planck $\rm Y_{SZ}$ measurements and obtained the corresponding mass proxy, $\rm M_{Y_{SZ}}$, from the full Planck mission maps, minimizing the Malmquist bias due to observational scatter. In this talk, I will present new relations between the $\rm Y_X$ and $\rm Y_{SZ}$ quanties, as well as $\rm M_{Y_X}$ and $\rm M_{Y_{SZ}}$. I’ll also present results from extensive simulations to deal with selection effects, intrinsic scatter, and covariance between quantities. Finally, I’ll demonstrate analytically how the $\rm Y_X - Y_{SZ}$ relation changes when expressed in intrinsic quantities (units of $\rm Mpc^2$) instead of apparent flux (units of $\rm arcmin^2$).

Characterizing the bulk and turbulent gas motions in galaxy clusters

• Simon Dupourqué (IRAP)

We aim at characterizing the turbulent gas motions in the intracluster medium via the study of the statistics of the SZ distortion and X-ray surface brightness fluctuations. Our work is based on three complementary samples observed in SZ by Planck and/or NIKA2 and ACT, and in X by XMM-Newton, covering a wide range of redshifts and dynamical states of clusters. Characterizing the physical properties of these bulk and turbulent gas motions will help us to better understand the assembly of massive halos, hence the formation and the evolution of these large scale structures. We will present the results of our ongoing analysis from the X-ray and SZ data for a pilot sample of clusters. We will discuss the perspective of our work to the full LPSZ@NIKA2 sample.

The tumultuous evolution of a galaxy cluster captured close to its emergence from the cosmic web.

• Stefano Andreon

I will present the resolved thermodynamic of the most distant cluster for which such a measurement has ever been performed, IDCSJ1426 at z=1.75, which turned out also to be the more precise measurement for every high redshift cluster thanks to our joint use of both X-ray and SZ data. Profiting of the largest ever redshift baseline, I determined the evolution of the thermodynamic profiles of this cluster down to z=0.07, our reference local comparison sample, with unprecedent precision over a 10 Gyr baseline. In the talk, I will also introduce a new definition of the evolutionary rate to effectively compare ancestors and descendants. It turned out to have the advantage of separating cluster evolution, dependence on mass, pseudo-evolution and to return a number with unique interpretation, unlike other definitions.

Constraining AGN feedback model with the tSZ pressure profile

• Hideki Tanimura (Institut d'Astrophysique Spatiale)

Relativistic jets from AGN have a wide range of impacts on galaxy groups and clusters and are key for understanding their formation and physical properties. However, this non-gravitational process is not well understood. Galaxy groups with shallow gravitational potentials are ideal laboratories to study and constrain the AGN feedback model. I studied hot gas in ~66,000 SDSS LRG halos with an average halo mass of 3*10^13 Msun using the Planck tSZ map. I have detected their average tSZ radial profile at ~17σ and compared it with the cosmo-OWLS cosmological hydrodynamical simulations with different AGN feedback models. The best agreement has been obtained for the AGN8.0 model in the simulations. I have also compared my measured tSZ profile with the prediction from the universal pressure profile and found them consistent if the model accounts for the clustering of neighboring haloes via a two-halo term. I will present these results.

The variability of brightest cluster galaxies at high radio frequencies

• Tom Rose (Durham University)

The radio variability of AGN is a product of many underlying physical processes which connect the host galaxy to its supermassive black hole. These include the rate and manner of the black hole fuelling, spectral index changes due to interactions within the AGN, and evolving energy densities within radio jets. Studying and quantifying variability can therefore inform us about these processes. We report on an Owens Valley Radio Observatory (OVRO) campaign monitoring the high radio frequency variability of 20 nearby, cool-core brightest cluster galaxies. The observations are at 15 GHz, typically have an interval of 10 days, and span between 8 and 13 years. Using a range of variability detection techniques, we have analysed changes in the lightcurves on week to decade long timescales. Using additional observations from KVN, SCUBA2, and NIKA2, we also show how this variability relates to the sources' spectral properties at radio frequencies of up to 353 GHz.

The 300th-NIKA2 LPSZ twin samples: synthetic clusters to support real observations

• Aishwarya Paliwal (Sapienza Università di Roma)

Twin samples of synthetic clusters of galaxies with properties close to the targets of the NIKA2 Large program Sunyaev-Zeldovich effect (LPSZ) have been generated from the 300th simulations database. This Large SZ Program is observing a selection of galaxy clusters at intermediate and high redshift (0.5< z < 0.9), covering one order of magnitude in mass, with the NIKA2 camera at 30-m IRAM radiotelescope. These are SZ-selected clusters from the Planck and Atacama Cosmology Telescope (ACT) catalogs, where the selection is based on their integrated Compton parameter values, Y_500. The Three Hundred hydrodynamical simulations provide us hundreds of clusters satisfying these redshift, mass, and Y_500 requirements. This catalog exploited a large sample of simulated galaxy clusters with their environment modelled using a range of simulation packages and physics modules. In addition to the standard post-processing analysis, mock observational maps are available mimicking X-ray, optical, gravitational lensing, radio, and SZ observations. The primary goal of employing the twin samples is to compare different cluster mass proxies from synthetic X-ray emission, Sunayev-Zel'dovich effect and optical maps (by galaxy members velocity dispersion and lensing k-maps). We can then verify the impact that a limited sample of only 50 objects, could have on the final results. Scaling laws will be cross-correlated to reduce the scatter on the inferred mass and the mass bias will be related to various physical parameters.

The 300 cluster project -- the new GIZMO-Simba run

• Weiguang Cui (IfA, university of Ediburgh)

I will introduce the 300 galaxy project (https://the300-project.org/) with its new GIZMO-Simba run in this talk. Targeting at zoomed-in simulations of galaxy clusters with a very large sample (324 clusters with M_200>~6X10^{14} Msun/h), the 300 project provides varieties of analogues resulted from several semi-analytical models to hydrodynamical simulations with different baryon models. This new GIZMO-Simba run based on the successful Simba simulation (Dave et al. 2019) shows good agreements with observational results. I will show how Simba thinks the cluster, especially its brightest central galaxy, is formed with this set of galaxy clusters, and how Simba predicts the M_bh and M*/sigma relation at cluster scale.

Velocity dispersion vs cluster mass a new scaling law with The Three Hundred clusters

• Antonio Ferragamo (Sapienza Università di Roma)

The Planck Collaboration showed that the number of clusters as a function of their mass and redshift is an extremely powerful tool for Cosmological Analyses. However, the true cluster mass is not directly measurable. Therefore, we can estimate the cluster mass only through observables related to it called mass proxies. On the one hand, these observables are several and related to the various components of which a cluster is composed. On the other hand, the theoretical relations that allow the use of these proxies often do not take into account observational and physical biases, which makes difficult the determination of the cluster mass. Fortunately, Cosmological simulations are an extremely powerful tool to assess these problems. We present our calibration of the scaling relation between mass and velocity dispersion from the study of the simulated clusters of the THREE HUNDRED PROJECT with mass above 10^13 Msun. In order to investigate the redshift dependence of the parameter of the relation, we analyzed it in 19 different redshifts between z = 0 and z = 2. Finally, we investigated the effect of different AGN feedback models.

Cold atomic and molecular gas in simulations of early galaxy formation -- coldSIM

• Umberto Maio (INAF)

New results from advanced numerical modelling of galaxy formation in the early Universe (Maio et al., 2021 to be submitted) will be presented and discussed by means of hydro/chemistry simulations of cold gas (coldSIM), from the epoch of reionization to later times. Besides star formation, feedback effects, stellar evolution and metal spreading, the new modelling includes gas fine-structure mm/sub-mm transitions, accurate time-dependent "non-equilibrium" chemistry calculations extended to consider the relevant small-scale cold-gas physics (H2 formation channels, self-shielding, dust grain catalysis, photoelectric and cosmic-ray heating, etc.) and the interplay with different UV backgrounds. We will show that primordial haloes can host molecular-driven star and galaxy formation already at high redshift, when popIII stars are the dominat generation, quickly followed by popII-I. HI gas density parameters are found to decrease in time from z~6 to z~2, consistently with available data and under a broad range of conditions. On the contrary, H2 molecules are more sensitive to physical modelling and resulting H2 density parameters are in line with recent IR/mm observational determinations when time-dependent chemical abundances are consistently coupled to gas shielding and UV radiation. Large molecular fractions as high as ~60% (as reported lately) can be justifed by either three-body interactions in pristine media or dust grain catalysis in exceptionally enriched sites at those times. Differently from previous simulation-based studies, that did not include non-equilibrium chemistry and struggled to reproduce HI and H2 behaviours, our findings highligth the possibility to understand cosmic chemical evolution in different epochs by following detailed non-equilibrium calculations coupled to state-of-the-arte numerical simulations.

The Three Hundred Project: contrasting clusters galaxy density in hydrodynamical and dark matter simulations

• Alejandro Jimenez Muñoz (LPSC-CNRS)

Galaxy cluster detection algorithms for IR and optical surveys are usually tested and optimize using semi-analytical large-scale-structure simulations. However, the impact of baryonic physics in the abundance and structure of dark matter sub-haloes might be important and so lead to significant bias on the performance of those algorithms. Thus, it is important to carefully understand the differences between hydro-dynamical and dark-matter-only (DM-only) simulations. For this purpose, we use the Three Hundred Project sample of 324 galaxy clusters, which correspond to zoom regions re-simulated with full physics and for DM-only. We investigate the substructures of galaxy clusters for three type of simulations: low resolution and high resolution DM-only simulations, and low resolution hydro-dynamical simulations. We find that for equivalent resolution, the hydro-dynamical simulation present more substructures, specially at low mass, in compare with the dark-matter-only simulations, which underestimates the galaxy abundance. When increasing the DM-only resolution, this lack of galaxies is compensated. Nevertheless, when accounting for resolution effects we osbserve that hydro-dynamical simulations predict larger galaxy density towards the cluster core. A potential cause for this effect is the cooling effect of gas, which would make the stellar and gas cores more resistant to be stripped out and to tidal disruptions.

The Three Hundred Project: Dynamical state of galaxy clusters and morphology from multi-wavelength synthetic maps

• Federico De Luca (Istituto Nazionale di Fisica Nucleare)

Laying at the top of structures of matter on the largest scales, galaxy clusters formation and evolution can be studied to characterize the fundamental properties of the Universe itself. Their dynamical state plays a key role in such studies but in general from observations is not trivial its determination. Since clusters morphology is strictly related to their dynamical state, one way to establish it is through morphological analysis on cluster maps from different observations. We study the connection between morphology and dynamical state of the simulated galaxy clusters from The Three Hundred Project. We quantify cluster dynamical state using a combination, $\chi$, of dynamical indicators from theoretical measures. The dynamical state of the cluster sample shows a continuous distribution from dynamically relaxed, more abundant at lower redshift, to hybrid and disturbed. The dynamical state presents a clear dependence on the radius, with internal regions more relaxed than outskirts. The morphology from multi-wavelength mock observation of clusters in X-ray, optical, and Sunyaev–Zel’dovich (SZ) effect images, is quantified by $M$ -- a combination of six parameters for X-ray and SZ maps -- and the offsets between the optical position of the Brightest Central Galaxy (BCG) and the X-ray/SZ centroids. All the morphological parameters are highly correlated with each other, while they show a moderately strong correlation with the dynamical $\chi$ parameter. The principal source of contamination in the relaxed cluster fraction, inferred from morphological parameters, is due to dynamically hybrid clusters. Compared to individual parameters, which consider only one aspect of cluster property (e.g. only clumping or asymmetry), the combined morphological and dynamical parameters ($M$ and $\chi$) collect more information and provide a single and more accurate estimation of the cluster dynamical state.

HE mass bias in The Three Hundred clusters

• Giulia Gianfagna

Galaxy clusters are the most massive structures in the Universe and their mass plays a key role in the estimation of the cosmological parameters. The mass of these objects is estimated through X-rays and SZ (Sunyaev-Zeldovich) effect observations, from which the temperature, density and pressure profiles of the hot gas between the galaxies are extracted, then the hydrostatic equilibrium (HE) is used to estimate their mass. This method usually leads to an underestimation of the mass, as shown in numerical simulations. We use a set of almost 300 simulated clusters from The Three Hundred Project, in order to estimate the cluster hydrostatic mass, and the bias deriving from it. We study the dependence of the bias on several dynamical state indicators across a redshift range from 0.07 to 1.3. Moreover, some clusters experienced a merger in the redshifts of our interest, so we study the evolution of the bias during those events.

A Deep Learning Approach to Infer Galaxy Cluster Masses in Planck Compton parameter maps

• Daniel de Andres (Universidad Autonoma de Madrid)

In this work, we evaluate for the first time Convolutional Neural Networks(CNNs) to infer the masses of observed galaxy clusters in the Planck Compton parameter maps. We train our network using simulated maps from the THREE HUNDRED SIMULATION project up to redshiftz of order 1 and test our model on real Planck Sunyaev-Zel’dovich (SZ) maps. Our data set consists on 191862 mock maps, which are based on 7106 different clusters from our simulations, and 1094 observed SZ maps. Furthermore, we train 4 separate CNNs for different redshifts intervals between z=0 and z=1. We show that our results are compatible with Planck estimates of the mass and also with weak lensing measurements

Rotational kSZ effect in groups and clusters from the MACSIS and BAHAMAS simulations

• Edoardo Altamura (Jodrell Bank Centre for Astrophysics)

In recent years, research on the kinetic SZ (kSZ) effect has enabled observers with tools to study the kinematics of the hot IGM gas on a cosmological (>10 Mpc) scales and in virialised structures, i.e. groups and clusters. Due to its relation to the gas dynamics, the kSZ signal contains a signature from to the bulk rotation of structures, referred to as rotational kSZ effect (Chluba & Mannheim 2002; Cooray & Chen 2002). With an amplitude typically $10^4$ times smaller than the thermal SZ spectral distortion, observing the rotational kSZ effect is extremely challenging and, to date, has only been achieved by aligning and stacking Planck SZ maps (Baxter et al. 2019). In order to explore the gas kinematics using the rotational kSZ as a probe, hydrodynamic cosmological simulations offer some of the most comprehensive datasets for this study. Numerical models can be used to validate assumptions made in observational strategies, as well as providing useful predictions for future kSZ measurements from NIKA-2, Simons Observatory or other facilities. The rich halo statistics from the BAHAMAS sample, integrated with information from the most rare and massive MACSIS clusters, constitutes a unique simulations suite for making such predictions. In our work, we combine the BAHAMAS and MACSIS datasets to investigate the rotational kSZ effect across a wide range of group and cluster masses. Based on these models, we also test the the stacking approach and estimate the amplitude of the stacked signal with varying mass, redshift and map-alignment geometry.

Shape and connectivity of clusters: Impact of dynamical state and accretion history

• Celine Gouin (Institut d'Astrophysique Spatiale)

Matter distribution around clusters is highly anisotropic from their being the nodes of the cosmic web. Clusters' shape and the number of filaments they are connected to, i.e., their connectivity, should reflect the level of anisotropy in the matter distribution and must be, in principle, related to their physical properties. In this presentation, I investigate the influence of the dynamical state and the formation history on both the shape and local connectivity of about 2400 groups and clusters of galaxies from the large hydrodynamical simulation IllustrisTNG at z=0. I find that the mass of groups and clusters mainly influences the geometry of the matter distribution: massive halos are significantly more elliptical, and more connected to the cosmic web than low-mass ones. Beyond the mass-driven effect, ellipticity and connectivity appear to trace different dynamical states, and this is the sign of different accretion histories. Relaxed groups and clusters are mostly formed long time ago, and slowly accreting matter at the present time. They are rather spherical and weakly connected to their environment.This is mostly because they had enough time to relax and, hence, lost the connection with their preferential directions of accretion and merging. In contrast, late-formed unrelaxed groups and clusters are highly anisotropic with large connectivities and ellipticities. These objects are in formation phase and must be strongly affected by the infalling of materials from filaments.

Internal dark matter structure of the most massive galaxy clusters since redshift 1

• Amandine Le Brun (LUTh, Paris Observatory)

The evolution of the dark matter profiles of high-mass galaxy clusters from z~1 to the present day remains poorly constrained and is a powerful test of the LambdaCDM model. Such a test requires systematic confrontations of observations of a representative sample of the Universe's most massive clusters, preferably in several redshift bins, with tailor-made numerical simulations. To date, there exist no cosmological numerical simulations with the exceptionally large volume (required to simulate the rarest, most massive clusters) and the resolution (required to resolve their structure) necessary to undertake such a project. We will present the first results from a simulation campaign aimed at producing large cosmological simulations that are 1 Gpc/h on a side and have a medium mass and spatial resolution. They are being complemented with very-high resolution zoom simulations which are progressively including the non-gravitational physics of galaxy formation such as star formation, supernova and AGN feedback. The simulations are produced using the AMR code RAMSES. The first results are based on a subset of the systems, consisting of the 25 most massive galaxy clusters at each redshift (z=1, 0.8, 0.6 and 0) to study the evolution of their internal structure, finding that their dark matter profiles within r500 are strikingly similar from z ∼ 1 to the present day, exhibiting a low dispersion of 0.15 dex, and showing little evolution with redshift in the radial logarithmic slope and scatter. They have the running power law shape typical of the NFW-type profiles, but their inner structure shows no signs of converging to an asymptotic slope. This suggests that this type of profile is already in place at z > 1 in the highest-mass haloes in the Universe, and that it remains exceptionally robust to merging activity.

Bridging the gap between large and small scales in astronomical images through simultaneous modeling of point-like and diffuse emission

• Richard Feder (California Institute of Technology)

Many ground- and space-based photometric surveys are quickly approaching sensitivities where correlations between point-like and diffuse emission can lead to significant biases and mis-estimated uncertainties if ignored. Probabilistic cataloging (Portillo et *al*. 2017, Daylan et *al*. 2017) is a Bayesian hierarchical modeling framework where covariances due to blending can be explored by sampling from the (transdimensional) model space of catalogs consistent with a given image dataset. In this work, we extend the formalism of probabilistic cataloging to jointly model point-like and diffuse emission through a Fourier component template-based approach, implemented in the code Diffuse Background Cataloger (*DBCAT*). Using a combination of mock and real *Herschel*-SPIRE sub-millimeter multiband map data, we demonstrate that point source and diffuse emission can be reliably separated and estimated, including in the confusion-limited regime. This is validated using catalog- and field-based summary statistics of the reconstructed components. Beyond the set of global Fourier basis templates used by *DBCAT*, additional templates can be included to infer the contributions of unique extended emission components. As an example, we demonstrate that the thermal Sunyaev-Zel'dovich (tSZ) effect can be reliably estimated in cluster fields observed by SPIRE with contamination from cosmic infrared background (CIB) galaxies and cirrus dust, with proper marginalization over a CIB model in which the number of galaxies is unknown *a priori*.

A tale of two galaxies (and everything in between) inside a cluster progenitor at z~3

• Boris Sindhu Kalita (CEA-Saclay)

We report the results from a combination of very deep optical, near-IR (HST, Vista, Spitzer) and sub-mm (ALMA) data, that has provided a very comprehensive picture of the highest redshift galaxy-group to have an observationally characterised halo, RO-1001 at z=2.91. There is direct evidence of a massive Ly-alpha detected cold gas reservoir in this galaxy-cluster progenitor, being fed by accretion streams. This provides enough fuel for the extreme star formation in the three spectroscopically confirmed primary massive galaxies inside the group, that feature a total rate of ~1250 Msun/yr. However, based on a detailed photometric study, possibly within the same environment also exists an extremely old quiescent galaxy passively evolving for about 1.7 +/- 0.4 Gyr (mass-weighted stellar age). Such conflicting characteristics of similarly massive galaxies (≥10^11 Mstar) within the same group raises the question: HOW? We make a one-to-one comparison to answer this, using the quiescent galaxy and one of its star-forming counterparts. Adding another plot-twist is the ALMA detection of diffuse dust with a net flux of ~3 mJy, distributed over the intergalactic medium within the core of RO-1001. This, we propose, could be an additional channel for cooling the surrounding gas: through IR radiation from collisionally excited dust. This would further deepen the mystery of how a passive galaxy can exist in a gas-rich environment, while also initiating a discussion on this cooling mode that is usually not considered in studies of such galaxy-cluster progenitors or ‘protoclusters’.

Searching for high-z DSFGs with NIKA2 and NOEMA

• Longji Bing (Laboratoire d'Astrophysique de Marseille)

As the possible progenitors of passive galaxies at z=2-3, dusty star-forming galaxies(DSFGs) at z>4 provide a unique perspective to study the formation, assembly and early quenching of massive galaxies in the early Universe. The extreme obscuration in optical-IR makes (sub)mm spectral scans the most unambiguous way to confirm/exclude the high-z nature of candidate sources. In this talk, we will present a joint-analysis method to efficiently search for the most possible spectroscopic redshift in spectral scans on high-z DSFGs candidates. In addition to the (non)detections of lines in the spectra, the total IR luminosities estimated by the SED fitting are also used to predict the line fluxes and evaluate if the (non)detections are consistent with the expected line fluxes at given redshifts. We will show its power in identifying the redshift of high-z DSFGs found in NIKA2 science verification data, and discuss the possible implication of this framework to the ongoing IRAM 30m large program: NIKA2 Cosmological Legacy Survey(N2CLS).

Observations with KIDs Interferometer Spectrum Survey (KISS)

• Alessandro Fasano (LAM)

In the millimeter astronomy domain, there is a strong demand of the scientific community to develop multi-band instruments for component discrimination, foreground characterization and Cosmic Microwave Background spectral distortion mapping and line intensity mapping. An interesting instrumental candidate to fulfill such a necessity is the exploitation of Fourier Transform Spectrometers (FTSs). In particular, the case of ground-based experiments needs an additional requisite: the atmospheric fluctuations have to be addressed. For this purpose, FTSs have to be coupled with fast detectors, and Kinetic Inductance Detectors (KIDs) are the fastest available in large format array. In this scientific framework, we have developed the KIDs Interferometer Spectrum Survey (KISS), which uses two arrays of KIDs coupled to a Martin-Puplett interferometer. KISS allows a wide instantaneous Field of View (1 degree) and a spectral resolution up to 1.5 GHz in the 120–180 GHz electromagnetic band. The instrument is installed on the 2.25-meter Q-U-I JOint TEnerife (QUIJOTE) telescope in the Observatory of Teide, Tenerife, and it is currently operational. KISS has been the pathfinder of the new CarbON CII line in the post-rEionization and ReionizaTiOn epoch project (CONCERTO). I will give an overall description of the instrument and I will present recent results from the last year of observations.

CONCERTO at APEX: Installation and first phase of on-sky commissioning

• Andrea Catalano (LPSC - CNRS)

CONCERTO is a large field-of-view spectro-imager that has been installed in the Cassegrain Cabin of APEX telescope in April 2021. The scientific program of CONCERTO has many objectives: the main two programs are focused on mapping the fluctuations of the [CII] line intensity in the reionisation and post-reionisation epoch (4.5<z<8.5) and on studying galaxy clusters via the thermal and kinetic SZ effect. Also, CONCERTO will measure the dust and molecular gas contents of local and intermediate-redshift galaxies, it will study the Galactic star-forming clouds and finally it will observe the CO intensity fluctuations arising from 0.3<z<2 galaxies. From the instrumental point of view, with 2 focal planes and a total number of 4k KID detectors, CONCERTO will cover an instanteneous field of view of 20 arc-minutes in the range of electromagnetic frequencies 120-360 GHz. The spectral resolution is easily tunable up to 1 GHz depending on the scientific target. I will present the design of the instrument, the installation at Apex and the current status of the commissioning phase and science verification at the time of the talk.

MIllimetric Sardinia radio Telescope Receiver based on Array of Lumped elements kids

• Giuseppe D'Alessandro (Dipartimento di Fisica - Sapienza)

MISTRAL is a millimetric camera working in the W–band (77–103 GHz) which will take data from the Sardinia Radio Telescope, the Italian 64-m radio telescope located near Cagliari, at 600m above the sea level, in Sardinia. It is being built as a facility instrument by the Sapienza University for INAF, that manages the radio telescope, under a PON contract. It will consist of a compact cryostat hosting the re–imaging optics, cooled at 4 K, and a 408–pixel array of photon–noise limited lumped element kinetic inductance detectors fabricated at CNR-IFN and cooled at a base temperature lower than 300 mK. MISTRAL will be able to investigate a long list of scientific targets spanning from extragalactic astrophysics to solar system science, with high angular resolution (~13"), including Sunyaev Zel'dovich effect measurements and the study of the Cosmic Web.

Preliminary results on NIKA2 polarization observations of the Crab nebula at 260 GHz

• Alessia Ritacco (IAS, LPENS)

The Crab nebula is a supernova remnant exhibiting a highly polarized emission at millimetre wavelengths and commonly used as a standard candle for any experiment which aims to measure the polarization of the sky. Ritacco et al. 2018 have provided for the first time an estimation of its polarized spectral energy distribution (SED) in the frequency range of 23-353 GHz, confirming that a synchrotron radiation from a single population of relativistic electrons is responsible for the emission of the whole nebula. However, uncertainties remain in the frequency range of 200-353 GHz where high angular resolution and precise polarization observations are still missing. The information provided by NIKA2 at 260 GHz combined with NIKA observations at 150 GHz gives us the unique opportunity to disentangle the contribution of synchrotron and dust components at unprecedented angular scales inside the nebula. On another, but related, topic the NIKA2 Crab nebula polarized data will allow to improve the absolute calibration of Cosmic Microwave Experiments for the search of the imprint of the primordial gravitational waves (Aumont+2020). This contribution will show preliminary results on the Crab nebula obtained from the last commissioning campaign with NIKA2-Pol of November 2020. I will also discuss, depending on the progress of the analysis, the impact of these measurements on the understanding of the Crab nebula’s physics and as calibrator for future CMB experiments.

Probing the role of the magnetic field in star-forming filaments: NIKA2-Pol commissioning results on OMC-1

• Hamza AJEDDIG (Département d’Astrophysique (AIM), CEA Saclay, 91191 Gif-sur-Yvette, France)

Dust polarization observations are a powerful, practical tool to probe the geometry (and to some extent the strength) of magnetic fields in star-forming regions. In particular, Planck polarization data have revealed the importance of magnetic fields on large scales in molecular clouds. However, due to insufficient resolution, Planck observations are unable to constrain the B-field geometry on prestellar and protostellar scales. The high angular resolution of 11 arcsec provided by NIKA2-Pol 1.2 mm polarimetric imaging, corresponding to ∼0.02 pc at the distance of the Orion cloud (OMC), makes it possible to advance our understanding of the B-field morphology in star-forming filaments and dense cores (IRAM 30m large program B-FUN). The commissioning of the NIKA2-Pol instrument has led to several challenging issues which will be briefly addressed in the first part of the proposed presentation. In particular, we will present our current understanding of the instrumental polarization or intensity-topolarization "leakage" effect with NIKA2-Pol. We will show how this effect can be corrected for, leading to reliable exploitable data in a structured extended source such as OMC-1. We will present a statistical comparison between NIKA2-Pol and SCUBA2-Pol2 results in the OMC-1 region. We will also present tentative evidence of a local hourglass pattern centered on Orion-KL, in addition to a large-scale hourglass already seen by other instruments such as Pol2. Finally, we will discuss new estimates of the B-field strength in the OMC-1 region based on, e.g., the Davis-Chandrasekhar-Fermi (DCF) and structurefunction methods applied to NIKA2-Pol data, along with their associated limitations.

Candidate Cosmic Filament in the GJ526 Field Mapped with the NIKA2 Camera

• Jean-François Lestrade (Observatoire de Paris-LERMA-CNRS)

In the nearby universe, distinct large scale structures have been identified in the spatial distribution of optical galaxies. In the distant universe, the dust-obscured population of star forming galaxies should trace similar structures. Using the new NIKA2 dual band millimeter camera installed at the IRAM 30-meter radiotelescope, we have mapped a relatively large field (~70 arcmin^2) in the continuum at wavelengths 1.15~mm and 2.0~mm in the direction of the star GJ526 to investigate the nature of the quasi-alignement of five sources found with the camera MAMBO at 1.2mm ten years earlier. Our new NIKA2 map at 1.15~mm reveals additional sources and, in fact, an overdensity of dust-obscured star forming galaxies (SMGs) spatially distributed along a filament-like structure across the whole observed field. We discuss the hypothesis that these NIKA2 sources are actually located in a filament or in a sky-projected sheet-like structure of the cosmic web as predicted by theory and apparent in cosmological simulations. Our investigation at this stage shows the potential of deep survey in the continnum at millimeter wavelengths to study large scale structures of the distant universe.

Galactic Star Formation with NIKA2 (GASTON): First results from the Galactic plane survey

• Andrew Rigby (Cardiff University)

The formation of high-mass stars, with M > 8 solar masses, appears to require special conditions that are unnecessary for their lower-mass counterparts. A growing body of studies in the literature suggests that their precursors occur at the centres of networks of converging filaments, from which mass is channelled from globally-collapsing molecular clouds. However, it is not clear whether the so-called ‘hub-filament’ morphology is the exception or the rule for high-mass star formation, nor is it clear what the mass regime is at which such a setup becomes vital. The GASTON large programme at the IRAM 30m telescope is exploiting the high-angular resolution and mapping speed of NIKA2 to survey a large field of the inner Galactic plane (GP) at extremely high sensitivity in order to address these questions. In this talk, I will present the first science results obtained from the GASTON GP field, in which we have identified a large population of clumps of dense gas, of which a quarter have not been previously detected by Herschel. I will describe the steps taken to define distances to the clumps in the challenging GP environment, and to determine their physical properties. By dividing the sample into several groups based on their relative evolutionary age, we will show evidence that the most massive GASTON clumps are accreting material from their environment, supporting the scenario of globally-collapsing molecular clouds.

Galactic star formation with NIKA2 (GASTON): Quantifying interstellar filament convergence and its link to star formation

• Nicolas Peretto (Cardiff University)

Dusty filaments pervade the interstellar medium and their relation with the formation of stars is an active topic of research. In the past decade it has been shown that most prestellar and protostellar cores identified in nearby star forming regions (d<500pc) are located within dense interstellar filaments, suggesting a direct link between their evolution/fragmentation and the formation of star progenitors. In parallel, studies of individual Galactic plane (d~4kpc) hub filament systems, i.e. small networks of converging filaments, have shown that these structures might be systematically associated with massive star formation. Here, we make use of the Galactic plane observations of the GASTON large programme to systematically characterise and quantify filament convergence in order to identify an unbiased sample of hub filament systems. The relation between the increasing filament complexity of star-forming clumps and their ability to form massive stars will be investigated.

A Nearby Galaxy Perspective on Dust Evolution.

• Frédéric Galliano (AIM, CEA/Saclay, France)

The efficiency of the different processes responsible for the evolution of interstellar dust on the scale of a galaxy, are to date very uncertain, spanning several orders of magnitude in the literature. Yet, a precise knowledge of the grain properties is the key to addressing numerous open questions about the physics of the interstellar medium and galaxy evolution. In this talk, I will synthesize an empirical statistical study, aimed at quantifying the timescales of the main cosmic dust evolution processes, as a function of the global properties of a galaxy. We have modeled a sample of $\simeq$800 nearby galaxies, spanning a wide range of metallicity, gas fraction, specific star formation rate and Hubble stage. We have derived the dust properties of each object from its spectral energy distribution. Through an additional level of analysis, we have inferred the timescales of dust condensation in core-collapse supernova ejecta, grain growth in cold clouds and dust destruction by shock waves. We show that dust production by core-collapse supernovae is efficient only at very low-metallicity, a single supernova producing on average less than $\simeq$0.03 M$_\odot$/SN of dust. Our data indicate that grain growth is the dominant formation mechanism at metallicity above $\simeq$1/5 solar, with a grain growth timescale shorter than $\simeq$50 Myr at solar metallicity. Shock destruction is relatively efficient, a single supernova clearing dust on average in at least $\simeq$1200 M$_\odot$/SN of gas. Our results provide valuable constraints for galaxy evolution, and propose a framework for interpreting the dust masses of distant galaxies, derived from millimeter observations.

Exploring the millimetre emission in nearby galaxies

• Stavroula Katsioli

Emission of the nearby galaxies (distance < 30 Mpc) at millimetre wavelengths is a largely uncharted territory. This spectral region lies between the tail of the dust emission and the start of the radio emission (free-free and synchrotron radiation). Observing at these wavelengths is crucial to decompose the millimetre emission into the different emission mechanisms and to investigate if any excess emission, compared to realistic SED (Spectral Energy Distribution) models, exists. In this talk, we will present new observations at 1.15 and 2 mm using the IRAM 30-m telescope and the NIKA2 camera in the framework of the IMEGIN (Interpreting the Millimetre Emission of Galaxies with IRAM and NIKA2) Large Program. This is the first time that 22 nearby galaxies are being observed at high resolution (1.15 and 2mm beams are 11.1" and 17.6" respectively) at millimetre wavelengths. As a pilot study we present the observations of the edge-on galaxy NGC0891, and the spatially resolved SED analysis for the dust and radio emission. For the interpretation of the observations we make use of HerBIE (HiERarchical Bayesian Inference for dust Emission), a state-of-the-art SED fitting code which uses Hierarchical Bayesian statistics in order to eliminate the noise-induced correlations of the inferred parameters. Our analysis shows how the different emission components, at millimetre wavelengths, compare in different areas of the galaxy (disk, halo, star-forming sites) and how they correlate with the gas and dust mass.

Dust emission in millimeter wavelengths: Cooling of the interstellar medium in NGC6946

• Golshan Ejlali (IPM)

The interstellar dust plays an important role in the formation of molecular gas and its emission helps distinct the heating and cooling of the interstellar medium. Dust dominates the observed emission in galaxies over a wide spectral range reaching from the mid-IR to mm wavelengths. The spatial distribution of the mm-wave dust emission from galaxies is largely unexplored while we know that most of the gas and dust resides in relatively cold (10-20K) regions that are discernable from the warm dust emission near star-forming regions only with sufficient spatial resolution in face-on galaxies. The NIKA2 Guaranteed Time Project IMEGIN (Interpreting the Millimetre Emission of Galaxies with IRAM and NIKA2) has recently mapped the mm emission in a sample of nearby galaxies at high angular resolutions. As a pilot study, we present the observations of the face-on galaxy NGC6946. Subtracting the contributions from the free-free, synchrotron, and CO line emission, we map the distribution of the pure dust emission at 1.15 and 2mm. A relatively tight correlation is found between the CO and cool dust emission in star-forming regions. Separating the arm/interarm regions, we find a dominant emission from interarms indicating the significant role of the general interstellar radiation field in heating the cool dust. Finally, we present maps of the dust mass, temperature, and emissivity index using the Bayesian MCMC modeling of the spectral energy distribution in NGC6946.

The mm-to-cm SED of spiral galaxies: synergies between NIKA2 and SRT instruments.

• Simone Bianchi (INAF-OAA)

The mm-to-cm range of the Spectral Energy Distribution of spiral galaxies remains largely unexplored. Its coverage is required to disentangle the contribution of dust emission, free-free and synchrotron radiation and can provide constaints on dust models, star-formation rates and ISM properties. I present the case for a synergy between NIKA2 observations of nearby spirals and those from planned and current instrumentation at the Sardinia Radio Telescope, and report on a pilot K-band program to search for Anomalous Microwave Emission, an elusive emission component which is presumably related to dust.

Modelling the cold dust in nearby spirals galaxies with radiative transfer

• Angelos Nersesian (Ghent University)

Cosmic dust grains are one of the fundamental ingredients of the interstellar medium (ISM). Despite of their limited contribution to the total mass budget, dust grains play a significant role in the physical and chemical evolution of galaxies. Over the past decade, our knowledge on the cosmic dust in nearby galaxies has increased substantially thanks to the availability of observational data from UV to far-infrared wavelengths. However, one part of the spectrum, the mm range, has largely remained unexplored. We aim to take advantage of the new, high-resolution data in the mm range observed with the NIKA2 instrument. Combining these new observational data with our radiative transfer framework, would allow us to accurately model the interplay between starlight and dust in a sizeable sample of spatially-resolved nearby galaxies. I will present the methodology of our dust radiative transfer modelling and its application to a small group of face-on spiral galaxies. I will highlight which modelling steps need to be improved, and how the new NIKA2 data would allow us to firmly characterize the physical properties of the very cold dust (<15K), as well as to quantify the importance of different emission mechanisms in the mm.

Conclusions

• Frédéric Mayet (LPSC Grenoble)