# Observing the Universe at millimetre wavelengths

Europe/Paris
LPSC Grenoble

#### LPSC Grenoble

Description

The observations of the sky at millimetre wavelengths in the past years contributed to tremendous improvements in our understanding of a great variety of scientific topics ranging from the star formation in the Milky Way to the measurement of cosmological parameters.

The mm Universe conference series has started in 2019. The two first editions were mainly focused on NIKA2 although opened to the entire scientific community. Since then, the series evolved, and the name has been changed, in order to include all observations of the Universe at mm wavelength, at all scales from stellar to cosmological ones.  As multi-wavelength analysis is a key approach to understand astrophysical processes and cosmological issues, the conferences series is of course opened to results and observations at other wavelengths.

The first edition of the mm Universe conference was held at LPSC in Grenoble in June 2019 and the second edition was organized by the Department of Physics at Sapienza University in Rome and held online via Zoom due to the pandemic situation at that time.

The third edition will be held at LPSC in Grenoble in 2023 from June 26th to June 30th.

This international conference will bring together the scientific community working on science related to millimetre observations. It includes both theoretical and observational topics related to the mm Universe, from stellar to cosmological scales.

• mm Cosmology (CMB & clusters)
• Thermal & kinetic SZ
• Galaxy cluster physics (SZ, X, visible)
• Galaxy formation in the early Universe
• Nearby galaxies
• Galactic star formation
• From dust to planets
• mm instruments
• Simulations

Registration is closed.

### Registration Fees

• Registrations price, with conference dinner : 250 euros
• Registrations price, without conference dinner : 210 euros
• Conference dinner for accompanying person : 40 euros

Basic Registration (210 euros)  includes : coffee breaks, 5 lunches and one proceeding book.

### Financial Support

mm Universe acknowledges financial support from CNRS-IN2P3.

Participants
• Abhishek Sanjay Maniyar
• Aishwarya Paliwal
• Alejandro Jimenez Muñoz
• Aleksandra Kusiak
• Alessandro Fasano
• Alessandro Monfardini
• Alice Moyer
• Alina Sabyr
• Andrea Catalano
• Angelos Nersesian
• Anh DUONG Tuan
• Aniello Mennella
• Antonio Ferragamo
• Boris Bolliet
• Carsten Kramer
• Charles Romero
• Claudia Di Cesare
• Colin Hill
• Daisuke Nagai
• Damien Cherouvrier
• Daniel de Andrés Hernández
• Elenia Manzan
• Elia Stefano Battistelli
• Federico De Luca
• Federico Nati
• Fiona McCarthy
• Florian Kéruzoré
• Florian Ruppin
• François-Xavier Désert
• Frederic Mayet
• Gabriele Coppi
• Gaspard Aymerich
• Golshan Ejlali
• Gustavo Yepes
• Hélène Roussel
• Inigo Zubeldia
• Isabel Montoya Arroyave
• Itziar Aretxaga
• Ivanna Langan
• Jack Sayers
• Jason Austermann
• Jens Chluba
• Jianhang Chen
• Jonathan Gómez
• Joseph Golec
• Joshiwa van Marrewijk
• Juan MACIAS PEREZ
• Jyothis Chandran
• Kang Wang
• Kirsten Hall
• Kristen Surrao
• Lara Pantoni
• Laura Salvati
• Laurence Perotto
• Lindsey Bleem
• Louise Mousset
• Luca Di Mascolo
• Manon Ramel
• Marco De Petris
• Marian Douspis
• Mark Bishop
• Mathieu Remazeilles
• Melanie Kaasinen
• Michael McDonald
• Michał Michałowski
• Miguel Sánchez-Portal
• Miren Muñoz Echeverría
• Mohini Pachchigar
• Nabila Aghanim
• Nicolas Ponthieu
• Raagini Patki
• Raphaël Wicker
• Raven Gassis
• Sabrina Realini
• Samuel Leclercq
• Sandeep Kumar Acharya
• Sankalp Choudhuri
• Sara Santoni
• Sebastian Bocquet
• Sofia Savorgnano
• Srinivasan Raghunathan
• Stavroula Katsioli
• Stefano Andreon
• Stefano Berta
• Stefano Ettori
• Stefano Gallo
• Théo Lebeau
• Tony Mroczkowski
• Valentina Capalbo
• Xavier COULON
• Yvette Perrott
• +15
• Monday, June 26
• Monday A: Cluster-Cosmo
• Monday P: Cosmo
• 4:00 PM
Coffee break
• Monday P: Clusters
• 1
Status of the NIKA2 Sunyaev-Zeldovich Large Program

The NIKA2 camera operating at the IRAM 30-m telescope has unique performance for the resolved observation of the Sunyaev-Zel’dovich effect towards galaxy clusters. As part of the NIKA2 guaranteed-time, the SZ Large Program (LPSZ) is devoted to the high-angular resolution SZ mapping of a representative sample of about 40 galaxy clusters drawn from the SZ-selected catalogues of the Planck satellite and of the Atacama Cosmology Telescope, and also observed in X-ray with XMM-Newton or Chandra. The main goal of this program is to provide the community with unprecedented measurements of the mean pressure profile of galaxy clusters and of the scaling law between the SZ observable and the hydrostatic mass, extending previous measurements to higher redshifts and lower masses, in order to improve the accuracy of cosmological constraints with galaxy clusters. I will review the status of the LPSZ observation, present the standard analysis to go from NIKA2 raw data to the thermodynamical properties of galaxy clusters and offer a panorama of the studies of some interesting clusters drawn from the LPSZ sample.

Speaker: Laurence Perotto (LPSC)
• 2
panco2: ICM pressure profiles from tSZ observations in python

Measuring the distribution of gas pressure in galaxy clusters is a key ingredient of cluster science, both from a cosmological and an astrophysical standpoint. Millimeter-wave observations offer highly valuable datasets for these measurements thanks to the thermal Sunyaev-Zeldovich (tSZ) effect, a spectral distorsion of the CMB with an amplitude directly proportional to the line of sight-integrated pressure of the intracluster medium (ICM). To perform these measurements, we have developed panco2, a Python library using MCMC forward modeling to extract ICM pressure profile estimates from millimeter-wave datasets. The software uses very flexible inputs, allowing its user to take into account various systematics affecting millimeter-wave observations, such as point source contamination, spatial filtering, and colored noise.

In this talk, I will present panco2, its usage and validation. I will describe the algorithm used to perform the pressure profile estimation, the different observational features that can be taken into account, and the data required to perform the analysis. I will describe the validation framework that has been created for panco2, using mock clusters of different masses and redshifts, with simulated observations by different millimeter-wave instruments. Finally, I will discuss the code availability, from the public Github including the code and the validation products, to the online documentation.

Speaker: Florian Kéruzoré (Argonne National Laboratory)
• 3
NIKA2 observations of 3 low mass clusters at z ~ 1: P(r) and Y-M relation

Three galaxy clusters selected from the XXL X-ray survey at high redshift and low mass (z ~ 1 and M500 ~ 1-2 x 10^14 Msun) were observed with NIKA2 to image their Sunyaev-Zel'dovich effect (SZE) signal. They all present an SZE morphology, together with the comparison with X-ray and optical data, that indicates dynamical activity related to merging events. Despite their disturbed intracluster medium, their high redshifts and their low masses, the three clusters follow remarkably well the pressure profile and the SZE flux-mass relation expected from standard evolution. This suggests that the physics that drives cluster formation is already in place at z ~ 1 down to M500 ~ 10^14 Msun.

Speaker: Rémi Adam (Laboratoire Lagrange, Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Blvd de l'Observatoire, CS 34229, 06304 Nice cedex 4, France)
• Tuesday, June 27
• Tuesday A: High-z galaxies
• 10:30 AM
Coffee Break
• Tuesday A: Instrumentation
• 4
CONCERTO: instrument and first results

CONCERTO (CarbON CII line in post-rEionization and ReionizaTiOn) is a low-resolution spectrometer with an instantaneous field-of-view of 18.6 arcmin, operating in the 130–310 GHz transparent atmospheric window. It is installed on the 12-meter Atacama Pathfinder Experiment (APEX) telescope at 5 100 m above sea level.
The Fourier transform spectrometer (FTS) contains two focal planes hosting a total of 4 304 kinetic inductance detectors.
The FTS interferometric pattern is recorded on the fly while continuously scanning the sky.
One of the goals of CONCERTO is to characterize the large-scale structure of the Universe by observing the integrated emission from unresolved galaxies via the line intensity mapping technique.
In this presentation, I will introduce the CONCERTO instrument and show some first results.

Speaker: Alessandro Fasano (Laboratoire d'astrophysique de Marseille (LAM))
• Tuesday P1: High-z
• Tuesday P2: Cosmo-cluster
• 4:00 PM
Coffee Break
• Tuesday P1: High-z
• Tuesday P2: Clusters
• 5
Deep Learning Generative Models to Infer Mass Maps from SZ, X-ray and galaxy members Observations in Galaxy Clusters.

In our previews works, deep learning techniques have succeeded in estimating galaxy cluster masses in observations of Sunyaev Zel'dovich maps, e.g. in the Planck PSZ2 catalog and mass radial profiles from SZ mock maps. In the next step, we explore inferring 2D mass density from mock observations of SZ, X-ray and stars using THE THREE HUNDRED (The300) cosmological simulation. In order to do that, we investigate state-of-the-art deep learning models that have been proven to be successful for image generation in multiple areas of research including astrophysics and medical imaging. These models are conditioned to observations, e.g. SZ maps, to generate the most likely matter 2D distribution given our dataset, composed of around 70 thousand mock maps from The300. We show that these models can successfully infer the 2D matter distribution with a scatter of around $10\%$ in their mass radial profiles and reproduce the matter power spectrum when comparing the generated maps with the ground-truth from the simulations.

The next natural step of this project is to apply DL models on high resolution SZ observation, such as NIKA2, SPT and ACT. However, mock images needed for training deep learning models must fully take into consideration the observational impact of the telescopes in order to mimic real observations.

• 6
Towards the first mean pressure profile estimate with the NIKA2 Sunyaev-Zeldovich Large Program

As the largest gravitationally bound objects in the Universe, galaxy clusters are key tools to study large-scale structure formation processes and to constrain cosmological models. These studies, however, require a precise characterization of cosmological tools such as a mass-observable scaling relation and a mean electronic pressure profile. Systematic effects, in particular at high redshift, have an impact on these tools and are currently the main limitation of cluster-based cosmology.

NIKA2, a millimeter camera installed at the IRAM 30-m telescope is a major experiment to extend our understanding of galaxy clusters. Combining sub-arcminute (17.6’’ at 150 GHz) angular resolution and a 6.5 arcmin diameter field of view, NIKA2 can resolve and map the Sunyaev-Zel'dovich (SZ) effect towards clusters up to high redshifts. Combined with X-ray data from XMM-Newton satellite, we can infer with high precision the thermodynamical properties and the hydrostatic masses of such objects within the NIKA2 SZ Large Program (LPSZ), which covers a representative sample of about 40 galaxy clusters at 0.5<z<0.9.

In this talk I will present the first characterization of a sub-sample of the LPSZ and discuss the methodology to measure the mean pressure profile.

Speaker: Corentin Hanser
• 7
Systematics effects on the upcoming NIKA2 LPSZ scaling relation

In Sunyaev Zeldovich (SZ) cluster cosmology, one of the main parameter of interest is cluster mass. It is needed to constrain cosmological parameters through the cluster number count. As the mass is not an observable, a scaling relation is needed to link cluster masses to the integrated Compton parameters Y, i.e the SZ observable.

Current cosmological results use the Planck scaling relation obtained with clusters at low redshift (z<0.5) observed in SZ and X-ray.
In the SZ Large Program (LPSZ) of the NIKA2 collaboration, the scaling relation can be obtained with a sample of 45 clusters at high redshift (from z=0.5 to z=0.9) and observed at high resolution both in SZ and X-ray. From these data, it will be possible to study various systematic effects that can affect the scaling relation.

For this purpose, several galaxy cluster samples have been simulated with gNFW pressure profiles and Compton maps similar to the NIKA2 ones. In addition, to quantify the impact of the cluster dynamical state, different features have been applied to the simulated sample (overpressure, non-sphericity, substructures, …). Their impact on the scaling parameter estimation has been studied.

In this talk, I will present the various systematic effects that can affect the Y-M scaling relation used in SZ cluster cosmology.

Speaker: Mrs Alice Moyer (LPSC IN2P3)
• Wednesday, June 28
• Wednesday A: Simu
• 10:30 AM
Coffee Break
• Wednesday A: Clusters
• 8
The Cluster XMM-Heritage project CHEX-MATE: current results and future prospects

The Cluster HEritage project with XMM-Newton – Mass Assembly and Thermodynamics at the Endpoint of structure formation (CHEX-MATE)
is a three-mega-second Multi-Year Heritage Programme to obtain X-ray observations of a minimally-biased, signal-to-noise-limited sample of 118 galaxy clusters detected by Planck through the Sunyaev–Zeldovich effect. The program aims to study the ultimate products of structure formation in time and mass. We will present the most recent results obtained from our large international collaboration, 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 hot plasma and dark matter. These studies will pave the way for using the next generation of X-ray observatories, like XRISM and Athena, to construct a consistent picture of the formation and composition in mass and energy of galaxy clusters.

Speaker: Stefano Ettori (INAF-Osservatorio di Astrofisica e Scienza dello Spazio in Bologna)
• 9
X-ray absorption and molecular content of the interstellar medium toward CHEX-MATE galaxy clusters

The X-ray spectrum of extragalactic sources, such as galaxy clusters, is affected by the photo-absorption of various components of the Galactic InterStellar Medium (ISM). The resulting spectral distortion contributes to the systematics of cluster temperature measurements. It essentially depends on the total (atomic+molecular) Galactic hydrogen density column, N_H, which remains challenging to map across the sky in the lack of a straightforward tracer of the molecular gas phase in the ISM. Combining data from the Planck HFI and HI4PI sky surveys, we investigate the mass fraction of molecular gas across the line of sight of CHEX-MATE galaxy clusters by looking for thermal dust emission excesses with respects to the neutral atomic hydrogen density column, N_HI. Consistent with earlier studies of the ISM based on IRAS and Planck data, we detect dust emission excesses along the line of sight of some members of the CHEX-MATE cluster catalogue mostly localised in dense ISM regions. We find that the CHEX-MATE cluster catalogue can be divided in 40 % of members located behind low N_HI regions where the molecular mass fraction is negligible, 40% of members located in intermediate N_HI regions where the molecular gas fraction would reach 10% on average, and the remaining 20% of members located in high N_HI regions that locally exhibits even higher molecular gas fractions. The cluster temperature shifts associated with molecular content of the ISM is about 1% or less for most CHEX-MATE clusters, but can exceed 5% in the highest N_HI regions.

Speaker: Herve Bourdin (University of Rome "Tor vergata")
• Wednesday P1: Cosmo
• Wednesday P2: Clusters
• 10
An ALMA+ACA+ACT view on the z=2 galaxy cluster, XLSSC 122

In recent years there have been an increasing amount of studies on the overdensities of galaxies in the distant Universe, even beyond a redshift of z>4. However, how these so-called protoclusters evolve from a structure stretching several hundreds of Mpc to a bonafide galaxy cluster and how these distant clusters of galaxies differ from local ones are still open questions in modern astronomy. This is because there are only a handful of observational constraints of clusters at intermediate, z~2, redshifts.

Despite being named for their visible galaxy constituents, a galaxy cluster's main baryonic matter component is the thermalized, low-density plasma found between the galaxies, which is known as the intracluster medium (ICM). Therefore, observations of the ICM in distant clusters of galaxies are key to answering the above-mentioned questions. However, many sub-mm observations focus only on the cluster members.

In this talk, I will show you how to jointly model ALMA+ACA+ACT observations of the ICM observed through the Sunyaev-Zeldovich (SZ) effect via a bayesian forward-modeling technique implemented in the Fourier domain. With this routine, we detect and characterize the ICM of the most distant galaxy cluster found in current SZ-cluster catalogs, namely XLSSC 122. This case study will be the start of a high-resolution era for observations of the ICM in high-z systems as single-dish telescopes start finding more and more high-z galaxy clusters, which can be followed up and combined with ALMA Band 3 and future Band 1 and 2 observations.

Speaker: Joshiwa van Marrewijk (European Southern Observatory (ESO))
• 11
A HST dark galaxy merger at z~1 revealed by ALMA

Galaxy mergers are known to be one of the major paths through which galaxies evolve across cosmic time, therefore it is absolutely necessary to study such systems at different redshifts to further our understanding of galaxy evolution. Significant progress has been made in the last decades thanks to HST, although a remaining challenge is the presence of obscuring dust, which can make one or more individual components invisible and therefore, completely impossible to identify as a merger. This is where radio telescopes such as ALMA enter. Not only has ALMA recently opened a new window to observe rest-frame far-infrared emission, thus revealing dust obscured sources, but ALMA also provides high-resolution observations essential to distinguishing multiple components.
While studying CO(5-4) and CO(2-1) emission of a massive star-forming galaxy part of the COSMOS field, we revealed an adjacent companion which was totally invisible to HST, uncovering an ongoing major merger of galaxies at z=1.17. This redshift makes this merger particularly interesting as it is happening at the end of the peak of star formation activity in our Universe, also known as cosmic noon, where this class of mergers still remains unexplored.
In my talk, I will show our findings for this example of a so far poorly understood class of mergers, i.e., morphological and kinematics properties of the two galaxies, their stellar and gas budget as well as their ISM conditions. I will also discuss the importance of multi-wavelength studies to fully access all baryonic properties of galaxies, and include future plans to further explore similar systems.

Speaker: Ivanna Langan (ESO (Garching))
• 12
Probing the Ionized Gas Thermodynamics in unWISE Galaxies with the Sunyaev-Zel’dovich Effect

The Sunyaev-Zel’dovich Effect—the Doppler boost of low-energy Cosmic Microwave Background photons scattering off free electrons—is an excellent probe of ionized gas residing in distant galaxies. Its two constituents are the kinematic SZ effect (kSZ), where electrons have a non-zero line-of-sight (LOS) velocity and which probes the electron line-of-sight momentum, and the thermal SZ effect (tSZ), where electrons have high energies due to their temperature, and which probes the electron integrated pressure. These two effects provide complementary information to constrain the thermodynamic profile of the gas residing in distant galaxies, which can be further used to understand feedback processes, a necessary ingredient to describe the evolution of the large scale structure in our Universe. Both tSZ and kSZ can be measured in cross-correlation with large-scale structure.

In this talk, I will show my ongoing measurements of the tSZ-galaxy cross-correlation using unWISE galaxies with the newest ACT DR6 data, along with the measured kSZ signal of unWISE galaxies with Planck using the projected-field estimator (which does not require spectroscopic redshift information of the galaxy sample). unWISE is a galaxy catalog, which consists of three subsamples of mean redshifts z=0.5, 1.1, 1.5 and contains over 500 million galaxies on the full sky, and whose halo occupation distribution I have already constrained. The tSZ-galaxy cross-correlation measurement will be the highest SNR to date. I will also discuss the prospects of combining both measurements and applying the method to other galaxy samples.

Speaker: Aleksandra Kusiak (Columbia University)
• 13
Characterizing new low-z clusters with the CEREAL sample

In the coming years, we will use the latest generation of Sunyaev-Zel'dovich (SZ) detectors to discover galaxy clusters at lower masses---and therefore higher redshifts---than ever before. These high-z, low-mass clusters are the progenitors of low-z, high-mass clusters, and follow-up X-ray observations will reveal insight into the origin and evolution of clusters. However, our understanding of the properties of z$\sim$0 clusters is currently limited by selection biases, so we are in need of a statistically complete low-z sample to anchor our studies of high-z clusters.

To this end, we designed the Cluster Evolutionary Reference Ensemble At Low-z (CEREAL) to be a representative population of massive, nearby galaxy clusters. These 108 clusters were cleanly selected in mass and redshift from the Planck 2nd SZ Survey and followed up uniformly with Chandra. They have masses spanning the range between the evolutionary tracks of the Perseus cluster and the Coma cluster as well as a narrow redshift spread around z=0.2. They correspond to the descendants of the lowest mass clusters that we expect to observe at z$\sim$2 with the third-generation detector on the South Pole Telescope (SPT-3G).

We are using the CEREAL sample to completely characterize the population of low-z clusters. We study the cool core fraction, the merger rate, and other morphological properties, as well as the thermodynamic and chemical enrichment profiles. We also carefully examine each cluster in search of interesting phenomena like bubbles produced by AGN feedback or multiple mergers. Together with new high-z observations, the CEREAL sample will facilitate evolutionary studies of galaxy clusters.

Speaker: Laurel White (MIT)
• 14
Constraining the mass and redshift evolution of the hydrostatic mass bias using the gas mass fraction in galaxy clusters

The gas mass fraction in galaxy clusters is a convenient probe to use in cosmological studies, as it can help derive constraints on a collection of cosmological parameters.
It is however subject to various effects from the baryonic physics inside galaxy clusters, which may bias the obtained cosmological constraints.
Among different aspects of the baryonic physics, in this presentation I focus on the impact of the hydrostatic equilibrium assumption.
I analyse the hydrostatic mass bias $B$, constraining a possible mass and redshift evolution of this quantity and its impact on the cosmological constraints.
To that end I consider cluster observations of the $Planck$-ESZ sample and evaluate the gas mass fraction using X-ray counterpart observations.
I show a degeneracy between the redshift dependence of the bias and cosmological parameters.
In particular I find a $3.8 \sigma$ evidence for a redshift dependence of the bias when assuming a $Planck$ prior on $\Omega_m$.
On the other hand, assuming a constant mass bias would lead to the extreme large value of $\Omega_m > 0.860$.
I however show that these results are entirely dependent on the cluster sample I consider.
In particular, the mass and redshift trends that I find for the lowest mass-redshift and highest mass-redshift clusters of our sample are not compatible.
Nevertheless, in all the analyses I find a value for the amplitude of the bias that is consistent with $B \sim 0.8$, as expected from hydrodynamical simulations and local measurements, but still in tension with the low value of $B \sim 0.6$ derived from the combination of cosmic microwave background primary anisotropies with cluster number counts.
I will also discuss cosmological constraints obtained from gas fraction data, combined with other probes like cluster number counts.

Speaker: Raphaël Wicker (Institut d'Astropysique Spatiale)
• 15
Detection of forming intracluster gas in a galaxy protocluster at z~2.16

Until now, direct observations of the intracluster medium (ICM) have been limited only to mature clusters in the latter three-quarters of the history of the Universe, and we have been lacking a direct view of the hot, thermalised cluster atmosphere beyond z~2, the epoch when the first massive clusters formed. Probing the thermal evolution of cosmic structures through z~2 — the epoch when intracluster gas starts to assemble and virialise, and cosmic star formation and the activity of active galactic nuclei (AGN) manifest a concurrent peak — is however crucial for exploring the link between galaxy clusters and their over-dense progenitors, as well as finding the observational fingerprint of feedback effects that regulate the later coevolution of the galaxy and intracluster/circumgalactic medium ecosystems.
In my talk, I will present our recent detection of the thermal Sunyaev-Zeldovich (SZ) effect in the direction of the protocluster complex surrounding the famous Spiderweb Galaxy (z~2.16), made possible only thanks to the superior capabilities of the Atacama Large Millimeter/Submillimeter Array (ALMA). Such identification of a nascent intracluster halo represents the unambiguous proof that we are witnessing the transition through which a sparse overdensity of galaxies turns into a massive galaxy cluster. In my presentation, I will particularly focus on the observational challenges of extracting SZ information from ALMA measurements as well as on the astrophysical implications of such SZ detection.

Speaker: Luca Di Mascolo (Università degli Studi di Trieste)
• 4:00 PM
Coffee Break
• Wednesday P1: Nearby
• Wednesday P2: Simulation
• Thursday, June 29
• Thursday A: Observatories
• 10:30 AM
Coffee Break
• Thursday A: MW
• Thursday P1: Clusters
• 16
Biases in the estimation of the hydrostatic mass of the Virgo simulated clone

An accurate mass calibration of galaxy clusters is a crucial step towards precise constraints on the cosmological parameters $\sigma_8$ and $\Omega_m$ from clusters. In the millimeter, via the Sunyaev-Zel'dovich (SZ) effect, and X-rays domains, cluster masses can be estimated assuming hydrostatic equilibrium, but several physical and observational effects can alter this calculation. One of those are projection effects which are the focus of our present analysis.
As a matter of fact, any hot and ionised gas along the line of sight of clusters can contribute to the observed pressure and thus impact our analysis of the clusters' SZ or X-ray signals. Moreover, the usually assumed spherical symmetry of clusters is not always verified, so the observed properties may strongly depend on the direction of observation. Cosmological simulations permit us to study the clusters from any point of view, they are therefore well suited to study projection effects.
In this presentation, I will show the results of a case study of the simulated Virgo cluster, extracted from the CLONE constrained simulation. In this study, we analyse Virgo properties when they are projected along different directions, including along the Milky Way-Virgo axis which mimics our observation direction. By comparing the deduced hydrostatic mass and the hydrostatic mass bias from the different observation directions to the one derived from the 3D profiles, we will show and quantify the impact of projection effects on the determination of Virgo mass as a first analysis that will later be generalised to a large sample of simulated clone clusters.

Speaker: Théo Lebeau (Institut d'Astrophysique Spatiale, Université Paris-Saclay)
• 17
Reconstruction of Galaxy Cluster Physical Properties: a Non-parametric Bayesian Nodal Approach

I will present a nodal approach to recovering the fundamental properties of galaxy clusters like pressure, density, and temperature. The method involves constructing piecewise functions that describe the quantities of galaxy clusters through a set of control points, which are inferred using a non-parametric Bayesian analysis. I will show an application of this method to the analysis of Planck Sunyaev-Zel’dovich (SZ) observations. Unlike the traditional parametric approach, it gets rid of the assumptions about the specific model of the cluster. This work has the potential to facilitate unbiased translations from observations to fundamental properties such as the gas pressure profile and improve our understanding of the cluster.

Speaker: Kang Wang (Victoria University of Wellington)
• 18
Effects of observed projections on turbulence statistics in the intracluster medium

The total mass of a cluster is one of its most fundamental properties. Measurements of the galaxy cluster mass often relies upon assuming hydrostatic equilibrium. However, this is often invalidated as the intracluster medium (ICM) is continuously disturbed by mergers, feedback processes, and motions of galaxies. These processes generate gas motions that contribute nonthermal pressure; typically turbulence, that leads to an underestimation of the mass by as much as 30%. We can measure turbulence through indirect probes that come in the form of fluctuations in the X-ray surface brightness and Sunyaev-Zeldovich effect maps. These are projected characteristics, encoding the 3D structure of the turbulence in the ICM. I will present an analysis of the 3D to 2D projections of the intracluster medium and its effect on the retrieved statistical measures commonly used in turbulence analysis like the power spectrum by using numerical simulations appropriate to galaxy clusters.

Speaker: Mark Bishop (Victoria University of Wellington)
• 19
Probing the evolution of galaxy clusters using Sunyaev-Zel’dovich effect

Mass is the most fundamental property of galaxy clusters however measuring it is still a challenge. Calibrating mass from intracluster medium observables such as the Sunyaev-Zel’dovich (SZ) effect is subject to uncertainty and biases because of the hydrostatic equilibrium assumption. On the other hand, merging cluster systems have been shown to exhibit radio emission which implies a link with disturbances from hydrostatic equilibrium. I will present work on studying deviations of galaxy cluster gas pressure profile from the average (universal) pressure profile using a sample of clusters with SZ effect data from the Arcminute Microkelvin Imager and Planck. These clusters have also been observed at low radio frequency with the Murchison Widefield Array allowing the investigation of links between gas pressure profile deviations and the presence of radio emission.

Speaker: Mohini Pachchigar
• 20
Studying the impact of galaxy cluster morphologies on their detection through SZ effect

In any cosmological analysis based on the galaxy cluster number count, a very important ingredient is the selection function of the detection method used to produce the galaxy cluster catalog. Indeed, an incorrect determination of this function can lead to biases in the cosmological parameters estimated from the data. In this work we aim to study the possible impact of complex cluster morphology on the selection function of the matched multi-filter (MMF) algorithm, used to detect galaxy clusters through the Sunyaev-Zel’dovich (SZ) effect. For the determination of the selection function, we apply the same method as in Planck Collaboration XXVII (2015), using mock cluster images from hydrodynamical simulations injected in the Planck high frequency maps. We compare these results with the analytical form of the completeness derived from assuming gaussian noise, and with the same method of injection/detection using spherical clusters generated from a generalised NFW profile.

Speaker: Stefano Gallo
• 21
Morphology with Zernike polynomials: the first application on Planck-SZ galaxy clusters

The Zernike polynomials has been recently used to model 2D projection maps of galaxy clusters to recover their morphological features. The study of the morphology of clusters maps is, in fact, a well suited approach used to infer, from real data, the dynamical state of those systems. After the validation of the Zernike polynomials as suitable tools to constrain galaxy clusters morphologies, done on a set of mock maps of clusters in THE THREE HUNDRED project, we present here the first application of this method on real data. We analyzed Compton parameter maps of local ($z < 0.1$) galaxy clusters observed by the Planck satellite and we use a single parameter, defined from the Zernike modeling, to quantify morphological differences between them. A set of Planck-like Compton parameter maps, realized for THE THREE HUNDRED clusters, is also used to correlate our analysis with a proper dynamical state classification achievable, in that case, from 3D information. This approach allow to test the efficiency of the Zernike morphological analysis in discriminating different dynamical populations in the real Planck sample.

Speaker: Valentina Capalbo (Sapienza, University of Rome)
• Thursday P2: Observatories
• 4:00 PM
Coffee Break
• Thursday P1: Clusters
• Thursday P2: CMB
• Friday, June 30
• Friday A: Clusters
• 22
Temperature measurements with the relativistic Sunyaev-Zel'dovich effect

At temperatures above ~5 keV, the non-relativistic approximation used to derive the classical thermal Sunyaev-Zel'dovich effect spectrum begins to fail. When relativistic effects are included, the spectrum becomes temperature-dependent. This leads to both a problem and an opportunity: a problem, because when the temperature dependence is not accounted for the Compton-y estimate is biased; and an opportunity, because it represents a new way to measure the temperature of the intracluster medium independently of X-ray observations. I will present current results from recalibrating the Planck mass-observable scaling relation to include relativistic effects, and projections for future measurements of cluster temperatures using AtLAST.

Speaker: Yvette Perrott (Victoria University of Wellington)
• 23
Prospects for Kinematic Sunyaev-Zeldovich Measurements from South Pole Telescope data.

The Doppler boosting of cosmic microwave background (CMB) photons due to scattering off free electrons produces the Kinematic Sunyaev-Zeldovich (kSZ) effect. It offers a unique way to probe the epoch of reionisation. However, the kSZ signal is sub-dominant to other astrophysical signals, in particular the emission from dusty star forming galaxies that form the diffuse component of the cosmic infrared background (CIB) at millimetre wavelengths. In this talk, I will present results from an ongoing work that combines data from the South Pole Telescope (SPT) and the Herschel-SPIRE experiments to detect the kSZ power spectrum in a manner which is robust against the contamination from CIB. I will also discuss the future prospects for kSZ measurements and the constraints on the physics of reionisation expected from SPT-3G, the current camera on the South Pole Telescope, and its proposed successor SPT4. The forecasts indicate that the future kSZ measurements from SPT can constrain the optical depth to reionisation with \sigma(\tau) = 0.005, which is highly complementary to primary CMB-based constraints from Planck, and the duration of reionisation with \sigma(\Delta z_{\rm re}) = 0.42, which is currently unconstrained by Planck.

Speaker: Srinivasan Raghunathan (National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign)
• 24
The hydrostatic-to-lensing mass bias and its evolution with redshift

Accurate reconstruction of galaxy cluster masses is key to use this population of objects as cosmological probe. In this work we present a study on the hydrostatic to lensing mass scaling relation for a sample of 53 clusters, with redshifts from z = 0.05 to 1.07, for which masses have been reconstructed homogeneously. Masses for each individual cluster have been measured from reconstructed mass profiles from X-ray and lensing data, without using any observable-mass scaling relation. We calibrate the systematic scatter between the masses reconstructed with our reference analyses with respect to published results. Accounting for the systematic scatter does not change our main results, but allows propagating the uncertainties related to the mass reconstruction method or used data set. Our analysis gives an hydrostatic-to-lensing mass bias in the range of (1 − b) = 0.5 to 0.9 and a weak evidence of evolution with redshift.

Speaker: Miren Muñoz Echeverría (LPSC)
• 10:30 AM
Coffee Break
• Friday A: Nearby galaxies/MW
• Friday P: Clusters
• 25
Probing the Evolution of the Intracluster Medium with Joint X-ray+SZ Surveys

I will discuss the progress that has been made by coming SZ data from the South Pole Telescope (SPT) with X-ray data from Chandra and XMM-Newton. To date, we have followed up hundreds of SPT-selected clusters with these two X-ray telescopes, providing the strongest constraints on the enrichment history of the intracluster medium (ICM), the dynamical evolution of clusters, the cooling and feedback history of cluster cores, and the deviations from self-similar evolution in cluster cores. These observations have become extremely challenging as we discover clusters at z~2, and so I will also include a discussion of how a next generation of X-ray surveys with STAR-X and AXIS, coupled with resolved SZ experiments, could enable us to trace cluster evolution to the epoch of their formation.

Speaker: Michael McDonald (MIT)
• 26
First massive galaxy clusters emerging from the cosmic web at z~2

In this talk we report upon results the intracluster medium (ICM) of two galaxy clusters at the time the first objects start to emerge from the cosmic web, z~2. Results are derived from new high resolution, deep SZ and X-ray data providing us with the measurement of the two most distant resolved pressure profiles. IDCSJ1426 cluster at z=1.75 has a core whose properties has likely reached the final stage, while the remaining part of the cluster is experiencing a sizeable gas, heat and entropy transfer. JKCS041 at z=1.80 is caught just after a major merger event as evidenced by its SZ-X-ray peak offset, its low central pressure, and its low Compton-Y parameter compared to its WL mass. Comparison with plausible descendant shows that its ICM will experience major changes at all radii.

Speaker: Stefano Andreon (INAF-OA Brera)
• 27
Non-thermal pressure support in galaxy clusters: current constraints and perspective

I will discuss how current (with XMM-Newton) and future X-ray observations (with XRISM and Athena) will be able to characterize the non-thermal pressure support in galaxy clusters, and how we can convert it in an estimate of the hydrostatic mass bias, also for a cosmological purpose.

Speaker: Stefano Ettori (INAF-Osservatorio di Astrofisica e Scienza dello Spazio in Bologna)
• 28
Fluctuations in Galaxy Clusters at millimeter wavelengths

Cosmological constraints from galaxy clusters are currently limited by the precision of mass estimation. Non-thermal pressure support is suspected to be the primary culprit in biasing mass estimations from the intracluster medium (ICM). Moreover, (quasi-)turbulent gas motions are thought to be the dominant source of non-thermal pressure, in which case high resolution X-ray spectrographs on Hitomi and upcoming missions should greatly expand our knowledge. There is also an indirect approach which observes fluctuations in the surface brightness of clusters, accessed either in X-ray or Sunyaev-Zel’dovich (SZ) images. Exploring fluctuations in SZ images is relatively novel and should still be advantageous for probing turbulence in high-redshift clusters and cluster outskirts. I will present results of SZ (observed by SPT or MUSTANG-2) and X-ray (observations with XMM-Newton) fluctuations and the inferred pressure and density fluctuations.

Speaker: Charles Romero (Center for Astrophysics | Harvard & Smithsonian)
• 29
Galaxy cluster mass inference using weak lensing shear multipoles

Weak gravitational lensing is a powerful tool to probe the matter distribution around massive galaxy clusters. In general, such effect can be measured by estimating the averaged tangential shear of background galaxies in circular annuli around the lens center. In addition to the average tangential shear, valuable information on the underlying dark matter distribution can be extracted by using shear multipoles, sensitive to higher order moments of the projected matter distribution. By releasing the spherical hypothesis of halo dark matter density, joint analysis of shear multipoles can be used to improve weak lensing mass reconstruction of massive clusters. In this work, we use the data from the project {\sc The Three Hundred} (Cui et al. 2018), which allows to perform our weak lensing analysis for the different line of sight projections available in the simulation. We show that using shear multipoles enables not only to have constraints on halo triaxiality, but can also affects the mass reconstruction of individual massive clusters.

Speaker: Constantin Payerne (LPSC-IN2P3)
• 30
The South Pole Telescope Strong Lensing Cluster Sample

The strong gravitational lensing regime provides a unique probe of structure formation in the Universe. There has been significant effort to identify and characterize strong lensing clusters selected in the X-ray and optical wavelengths; here we extend such studies to a large sample of strong lensing clusters identified by the Sunyaev Zel'dovich (SZ) effect in >5,000 square degrees of South Pole Telescope (SPT) data. In this talk I will describe (i) the identification of the strong lensing subset of the SPT cluster sample using observations from the PISCO imager on the Magellan/Clay telescope and the Hubble Space Telescope, (ii) first constraints on the mass-concentration relation of massive clusters using this dataset, and (iii) simulation efforts using large cosmological simulations to both generate predictions for the abundances of strong lenses in the SPT sample as well as to extract constraints from the observational data.

Speaker: Lindsey Bleem (Argonne National Laboratory)