Marco De Petris

The music of galaxy clusters - III. properties, evolution and Y-M scaling relation of protoclusters of galaxies

ABSTRACT In this work we study the properties of protoclusters of galaxies by employing the MUSIC setof hydrodynamical simulations, featuring a mass-limited sample of 282 resimulated clusterswith available merger trees up to high redshift, and we trace the cluster formation back to z= 1.5, 2.3 and 4. We study the features and redshift evolution of the mass and the spatial dis-tribution for all the cluster progenitors and for the protoclusters, which we define as the mostmassive progenitors of the clusters identified at z = 0. A natural extension to redshifts largerthan 1 is applied to the estimate of the baryon content also in terms of gas and stars bud-gets: no remarkable variations with redshift are discovered. Furthermore, motivated by theproven potential of Sunyaev-Zel’dovich surveys to blindly search for faint distant objects, wefocus on the scaling relation between total object mass and integrated Compton y-parameter,and we check for the possibility to extend the mass-observable paradigm to the protoclusterregime, far beyond the redshift of 1, to account for the properties of the simulated objects.We find that the slope of this scaling law is steeper than what expected for a self-similarityassumption among these objects, and it increases with redshift mainly for the synthetic clus-ters where radiative processes, such as radiative cooling, heating processes of the gas due toUV background, star formation and supernovae feedback, are included. We use three differentcriteria to account for the dynamical state of the protoclusters, and find no significant depen-dence of the scaling parameters from the level of relaxation. Based on this, we exclude thatthe dynamical state is the cause of the observed deviations from self-similarity.Key words: methods: numerical – galaxies: clusters – cosmology – cosmology: theory –cosmology : miscellaneous

SAGACE : The spectroscopic active galaxies and clusters explorer

The SAGACE experiment consists of a mm/sub-mm telescope with a 3-m diameter primary mirror, coupled to a cryogenic multi-beam differential spectrometer. SAGACE explores the sky in the 100-760 GHz frequency range, using four diffraction-limited bolometer arrays. The instrument is designed to perform spectroscopic surveys of the Sunyaev- Zeldovich effects of thousands of galaxy clusters, of the spectral energy distribution of active galactic nuclei, and of the [CII] line of a thousand galaxies in the redshift desert. In 2008 a full phase-A study for a national small mission was completed and delivered to the Italian Space Agency (ASI). We have shown that taking advantage of the differential operation of the Fourier Transform Spectrometer, this ambitious instrument can operate from a Molniya orbit, and can be built and operated within the tight budget of a small mission. Copyright

High-performance wobbling subreflector for the Millimetre and Infrared Testa Grigia Observatory 2.6-m telescope.

The Millimetre and Infrared Testa Grigia Observatory 2.6-m Cassegrain telescope has been designed to allow high-sensitivity observations in the millimeter spectral range. For this purpose, in order to reduce unwanted contributions from local foregrounds, we adopted a sky-chopping technique, by wobbling the telescope subreflector. We describe the design and performance of the wobbling system, which can endure external forced two and three fields square-wave modulation and includes features such as high frequency, high amplitude, high duty cycle, low microphonics, and high stability.

On the coherent rotation of diffuse matter in numerical simulations of clusters of galaxies

We present a study on the coherent rotation of the intracluster medium and dark matter components of simulated galaxy clusters extracted from a volume-limited sample of the MUSIC project. The set is re-simulated with three different recipes for the gas physics:

LIMITATIONS TO THE ACCURACY OF COSMIC BACKGROUND RADIATION ANISOTROPY MEASUREMENTS: ATMOSPHERIC FLUCTUATIONS

(i)

Baffling and shielding system for a millimeter-wave balloonborne telescope

non-radiative,

Morphological estimators on Sunyaev–Zel'dovich maps of MUSIC clusters of galaxies

(ii)

The Three Hundred project: a large catalogue of theoretically modelled galaxy clusters for cosmological and astrophysical applications

radiative without AGN feedback, and

The MUSIC of galaxy clusters – I. Baryon properties and scaling relations of the thermal Sunyaev–Zel'dovich effect

(iii)

Mito measurements of the Sunyaev-Zeldovich effect in the Coma Cluster of galaxies

radiative with AGN feedback. Our analysis is based on the 146 most massive clusters identified as relaxed, 57 per cent of the total sample. We classify these objects as rotating and non-rotating according to the gas spin parameter, a quantity that can be related to cluster observations. We find that 4 per cent of the relaxed sample is rotating according to our criterion. By looking at the radial profiles of their specific angular momentum vector, we find that the solid body model is not a suitable description of rotational motions. The radial profiles of the velocity of the dark matter show a prevalence of the random velocity dispersion. Instead, the intracluster medium profiles are characterized by a comparable contribution from the tangential velocity and the dispersion. In general, the dark matter component dominates the dynamics of the clusters, as suggested by the correlation between its angular momentum and the gas one, and by the lack of relevant differences among the three sets of simulations.