We investigate the impact of relativistic SZ corrections on Planck measurements of massive galaxy clusters, finding that they have a significant impact at the $\approx$5–15% and up to $\approx$ 3$\sigma$ level. We investigate the possibility of constraining temperature directly from these SZ measurements but find that only weak constraints are possible for the most significant detections; for most clusters, an external temperature measurement is required to correctly measure integrated Compton-y. We also investigate the impact of profile shape assumptions and find that these have a small but non-negligible impact on measured Compton-y, at the $\approx$ 5% level. Informed by the results of these investigations, we recalibrate the Planck SZ observable-mass scaling relation, using the updated NPIPE data release and a larger sample of X-ray mass estimates. Along with the expected change in the high-mass end of the scaling relation, which does not impact Planck mass estimation, we also find hints of a low-mass deviation, but this requires better understanding of the selection function in order to confirm.

The MAximum-entropy ReconStruction (MARS) method is a free-form strong-lensing (SL) reconstruction algorithm, which adopts the maximum cross-entropy as a regularization. MARS shows remarkable convergence of multiple images in both source (∼0.”02) and image planes (∼0.”05 – 0.”1) while suppressing spurious fluctuations. Although the reconstruction requires a large number of free parameters exceeding ∼19,000, our implementation through PyTorch can obtain the reconstruction within hours. From our test using the publicly available synthetic clusters, we have verified that the reconstructed radial mass profiles are consistent with the truth within 1 percent. This makes MARS one of the best-performing SL reconstruction methods. We apply MARS to the six Hubble Frontier Fields clusters and present new mass reconstruction results. We also reconstruct a mass model of Abell 2744 using both weak-lensing (WL) and SL data from the JWST observations, with the largest dataset of Abell 2744, including 286 SL multiple images and ∼350 arcmin−2 WL constraints.

The luminosity of the brightest stars (tip) of the red giant branch (TRGB) in the color–magnitude diagrams of old stars was used early on to introduce the ‘multiple stellar populations’ concept, in 1944, by Walter Baade. However, the precision and accuracy of the TRGB for distance estimation has not been known well for long. In the modern era, equipped with high spatial resolution imaging telescopes, the TRGB is considered an excellent standard candle for any type of resolved galaxies, thus representing a powerful probe for cosmology. The TRGB has several advantages over the classical Cepheids. I review how we can apply the TRGB in cosmology. Four science cases, from large to small scales, are presented: (1) the Hubble flow with Type Ia supernovae; (2) Virgo Cluster infall and dark matter; (3) dark galaxies; and (4) dark matter-free galaxies.

Integral field spectroscopic studies of galaxies in dense environments, such as clusters and groups of galaxies, have provided new insights for understanding how star formation proceeds, and quenches. I present the spatially resolved view of the star formation activity and its link with the multiphase gas in cluster galaxies based on MUSE and multi-wavelength data of the GASP survey. I discuss the link among the different scales (i.e. the link between the spatially resolved and the global star formation rate-stellar mass relation), the spatially resolved signatures and the quenching histories of jellyfish (progenitors) and post-starburst (descendants) galaxies in clusters. Finally, I discuss the multi-wavelength view of star-forming clumps both in galaxy disks and in the tails of stripped gas.

Magnetic fields originate small-scale instabilities in the plasma of the intra-cluster medium, and may have a key role to understand particle acceleration mechanisms. Recent observations at low radio frequencies have revealed that synchrotron emission from galaxy clusters is more various and complicated than previously thought, and new types of radio sources have been observed. In the last decade, big steps forward have been done to constrain the magnetic field properties in clusters thanks to a combined approach of polarisation observations and numerical simulations that aim to reproduce Faraday Rotation measures of sources observed through the intra-cluster medium. In this contribution, I will review the results on magnetic fields reached in the last years, and I will discuss the assumptions that have been done so far in light of new results obtained from cosmological simulations. I will also discuss how the next generation of radio instruments, as the SKA, will help improving our knowledge of the magnetic field in the intra-cluster medium.

The wealth of strong lensing features observed in the Frontier Fields clusters offers insights on the nature of dark energy. The large number of multiple-images systems with redshifts allows to simultaneously estimate the lens model parameters and the cosmological parameters involved in the distances calculations. In particular for the ΛCDM model, it is possible to estimate the matter density Ωm and the dark energy equations parameters wX. In this talk, I will present recent analyses of systematic errors based on Frontier Fields observed and simulated data.

By examining Herschel images in the HerMES & H-ATLAS surveys at the position of Planck Catalog of Compact Source sources we are able to determine the nature of the Planck sources. Most are simply nearby, known, dusty galaxies, while others are foreground galactic ‘cirrus’ dust. About 11% of sources, though, appear to be groups or clumps of fainter Herschel objects. Followup of a number of these indicates that they are galaxy clusters or protoclusters at z ~1-3 that contain a number of galaxies undergoing contemporaneous massive starbursts. These sources present challenges for current galaxy & cluster formation/evolution models.

We present the results of a multi-wavelength photometric study of the high redshift supercluster RCS2319+00. RCS2319+00 is a high-redshift (z ~ 0.9) supercluster comprising three spectroscopically confrmed cluster cores discovered in the Red Sequence Cluster Survey (RCS) (Gladders & Yee 2005). Core proximities and merger rates estimate coalescence into a 1015M⊙ cluster by z ~ 0.5 (Gilbank et al. 2008). Spectroscopic studies of the system have revealed over 300 supercluster members located in the cores and several infalling groups (Faloon et al. 2013). RCS2319 presents a diverse range of dynamical systems and densities making it an ideal laboratory in which to study the effects of environment on galaxy properties.

Imaging in optical and near infrared (griz' from MegaCam, JKs from WIRCam, both at CFHT), as well as 3.6 μm and 4.5μm from IRAC have enabled the assembly of a large photometric catalogue. Coupled with an extensive spectroscopic survey (Faloon et al. 2013) providing nearly 2400 redshifts across the field, photometric redshifts were determined using the template fitting code EAZY (Brammer et al. 2008). Nearly 80 000 photometric redshifts were measured providing a sample of nearly 3000 cluster members.

To investigate effects of global environment, analysis was done utilizing a friend-of-friends group finding algorithm identifying several large and small infalling groups along with the three cluster cores. The cores are found to be dominated by massive, red galaxies and the field galaxies are populated by low mass, blue galaxies, as is the case in the local universe. Interestingly, the large groups exhibit intermediate properties between field and core populations, suggesting possible pre-processing as they are being accreted into the core halos.

Relative fifth-nearest neighbour overdensity, log(1+δ5), is used as a proxy for local environment to investigate environmental dependence on galaxy colour. While there is an overall dependence of colour on local density, when controlled for stellar mass the dependence largely disappears. Indeed, galaxy mass is the dominant factor in determining colour, with local density a secondary effect only noticeable in lower mass galaxies at the 3 σ level for both colour and red fraction.

RCS2319+00 presents a rare opportunity to probe many different densities and environments all located within the same object. We're able to investigate how galaxy evolution is affected by the environment, from field galaxies to infalling to groups to dense cluster cores, as well as the different density regions within each environment.

In my talk I reviewed observations of the dark matter and total mass profiles in massive ETGs and clusters and their implications for ΛCDM. In this brief proceedings, I have extracted just a subset of material from my talk due to space limitations.

The Magneticum Pathfinder (www.magneticum.org) cosmological, hydro-dynamical simulation (896h-1Mpc)3 follows in detail the thermal and chemical evolution of the ICM as well as the evolution of SMBHs and their associated feedback processes. We demonstrate that assuming cosmological parameters inferred from the CMB, the thermal SZ power spectrum as observed by PLANCK is well matched by the deep light-cones constructed from these cosmological simulations. The thermal SZ prediction from the full SZ maps are significantly exceeding previous templates at large l (e.g., l > 1000) and therefore predict a significantly larger contribution to the signal at l = 3000 compared to previous findings. The excess of positive values within the probability distribution of the thermal SZ signal within the simulated light-cone agrees with the one seen by PLANCK. This excess signal follows a power law shape with an index of roughly -3.2. The bulk of the thermal SZ signal originates from clusters and groups which form between z = 0 and z ≈ 2 where at high redshift (z > 1) significant part of the signal originates from proto-cluster regions, which are not yet virialized. The simulation predicts a mean fluctuating Compton Y value of 1.18 × 10-6, with a remaining contribution of almost 5 ×10-7 when removing contribution from halos above a virial mass of 1013 M⊙/h.

Using the MHD version of Gadget3 (Stasyszyn, Dolag & Beck 2013) and a model for the seeding of magnetic fields by supernovae (SN), we performed simulations of the evolution of the magnetic fields in galaxy clusters and study their effects on the heat transport within the intra cluster medium (ICM). This mechanism – where SN explosions during the assembly of galaxies provide magnetic seed fields – has been shown to reproduce the magnetic field in Milky Way-like galactic halos (Beck et al. 2013). The build up of the magnetic field at redshifts before z = 5 and the accordingly predicted rotation measure evolution are also in good agreement with current observations. Such magnetic fields present at high redshift are then transported out of the forming protogalaxies into the large-scale structure and pollute the ICM (in a similar fashion to metals transport). Here, complex velocity patterns, driven by the formation process of cosmic structures are further amplifying and distributing the magnetic fields. In galaxy clusters, the magnetic fields therefore get amplified to the observed μG level and produce the observed amplitude of rotation measures of several hundreds of rad/m2. We also demonstrate that heat conduction in such turbulent fields on average is equivalent to a suppression factor around 1/20th of the classical Spitzer value and in contrast to classical, isotropic heat transport leads to temperature structures within the ICM compatible with observations (Arth et al. 2014).

We derive constraints on radio source clustering towards Planck-selected galaxy clusters using the NVSS point source catalog. The constraint can be used for making a more realistic Sunyaev-Zeldovich effect (SZE) mocks, calculating predictions of detectable clusters count and for quantifying source confusion in radio surveys.

The formation of the brightest cluster galaxies (BCG) is a challenge for galaxy formation theory. We performed high resolution cosmological hydrodynamical simulations with the AMR code RAMSES to study the properties of the BCG which forms at the center of a Virgo–like cluster. We compare the results of 2 galaxy formation scenarios, one in which only supernovae feedback is included, and one in which also AGN feedback is considered. Properties of the simulated BCG which are comparable with those of observed massive elliptical galaxies and BCGs cannot be obtained if AGN feedback is not considered. The stellar-to-halo mass ratio in simulations without AGN feedback appears too large when compared to observations, while it is compatible the observationally determined values when AGN feedback is included. The kinematical and structural properties of the BCG are extremely different in the two models. When we do not include AGN feedback, the BCG is quickly rotating, with high Sérsic index, a clear mass excess in the center and a very large stellar mass fraction. When AGN feedback is considered, the BCG is slowly rotating, with a significantly cored surface density profile and low stellar mass fraction.

Star forming galaxies often exhibit hot halos with structures that resemble chimneys and fountains extending for several kpc above the galaxy. Observations indicate that they are probably produced by supernovae (SNe) which blow superbubbles that carve holes in the disk. Through these holes, high speed material is injected and expands buoyantly up to a maximum height and then returns to the disk pulled by the galaxy gravity. This circulating gas in a fountain tends to condense out forming high-velocity clouds and filaments. Starburst galaxies also show evidence that the spectacular winds that arise from their disk are fed by SNe explosions. Similarly, at galaxy cluster scales, most massive clusters exhibit rich filamentary structure of ionized gas which is distributed all around the central galaxy. We discuss here the role that SNe bubbles play in driving outflows and filamentary structures both at galaxy and galaxy-cluster scales. With the help of HD and MHD numerical simulations, we show in particular that SN-driven turbulence may play a key role at helping a central AGN halting and ”isotropize” the cooling flow in the central regions of a galaxy cluster.

Distant planetary nebulae (PNe) are used to measure distances through the PN luminosity function, as kinematic tracers in determining the mass distribution in elliptical galaxies, and most recently, for measuring the kinematics of the diffuse stellar population in galaxy clusters. This article reviews the photometric and spectroscopic survey techniques that have been used to detect PNe beyond the Local Group, out to the Coma cluster at 100 Mpc distance. Contaminations by other emission sources and ways to overcome them will be discussed as well as some science highlights and future perspectives.