A. Gardini

National Center for Supercomputing Applications

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S. A. Bonometto

University of Trieste

G. Tormen

University of Padua

G. Murante

Trieste Astronomical Observatory

L. Moscardini

University of Bologna

P. Mazzotta

University of Rome Tor Vergata

Elena Rasia

Trieste Astronomical Observatory

P. M. Ricker

University of Illinois Urbana-Champaign

Gustavo Yepes

Universidad Autónoma de Madrid

S. De Grandi

Brera Astronomical Observatory

Andrea V. Macciò

Max Planck Institute for Astronomy

Cooperative Institutions

National Institute for Astrophysics

Trieste Astronomical Observatory

University of Trieste

Istituto Nazionale di Fisica Nucleare, Sezione di Trieste

Istituto Nazionale di Fisica Nucleare, Sezione di Milano

University of Milano-Bicocca

University of Bologna

Institute for Fundamental Physics of the Universe

Max Planck Institute for Astronomy

Max Planck Society

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Buoyant bubbles in a cooling intracluster medium I. Hydrodynamic bubbles

Astronomy and Astrophysics (2007)

A. Gardini

Aims. Over the past several years, numerous examples of X-ray cavities coincident with radio sources have been observed in so-called cool core clusters of galaxies. Motivated by these observations, we explore the evolution and the effect of cavities on a cooling intracluster medium (ICM) numerically, adding relevant physics step by step. Methods. In this paper we present a first set of hydrodynamical, high resolution (1024 3 effective grid elements), three-dimensional simulations, together with two-dimensional test cases. The simulations follow the evolution of radio cavities, modeled as bubbles filled by relativistic plasma, in the cluster atmosphere, while the ICM is subject to cooling. Results. We find that the bubble rise retards the development of a cooling flow by inducing motions in the ICM, which repeatedly displace the material in the core. Even bubbles initially set significantly far from the cluster center affect the cooling flow, although much later than the beginning of the simulation. The effect is, however, modest: the cooling time is increased by at most only 25%. As expected, the overall evolution of pure hydrodynamic bubbles is at odds with observations, showing that some additional physics has to be considered to match the data.

Intracluster medium

Cooling flow

Radiative Cooling

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Buoyant Bubbles in the Intracluster Medium

American Astronomical Society Meeting Abstracts (2004)

A. Gardini P. M. Ricker

Intracluster medium

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Limber equation for luminosity dependent correlations

New Astronomy (1999)

A. Gardini

Spatial correlation

Constant (computer programming)

10.1016/s1384-1076(99)00046-9

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Constraining Λ Using Cluster Quadrupoles

The Astrophysical Journal (2002)

Andrea V. Macciò A. Gardini Sebastiano Ghigna S. A. Bonometto

We examine how the statistics of the quadrupoles of (projected) cluster masses can discriminate between flat cold dark matter (CDM) universes with or without a cosmological constant term. Even in the era of high precision cosmology that cosmic microwave background experiments should open soon, it is important to devise self consistency tests of cosmogonic theories tuned at the matter radiation decoupling epoch using data from the non--linear evolved universe. We build cluster catalogs from two large volume simulations of a ``tilted'' CDM model and a $Λ$CDM model with cosmic density parameter $Ω_m=0.35$ and cosmological constant contribution $Ω_Λ=0.65$. From the projected mass distribution of the clusters we work out the quadrupoles Q and examine their dependence on cluster mass and the cosmological model. We find that TCDM clusters have systematically larger quadrupoles than their \lcdm counterpart. The effect is mass dependent: massive clusters ($M\gsim 10^{15}\Msunh$) have quadrupoles differing by more than 30% in the two models, while for $M\lsim 4\times10^{14}\Msunh$ the difference rapidly drops to $\sim 1$%. Performing a K-S test of the Q distributions, we estimate that using just the 15 most massive clusters in the simulation volume ($360\Mpch$ a side) we can discriminate between TCDM and \lcdm at a confidence level better than 99.9%. In the volume probed by exhisting observations, there are potentially several hundred clusters with masses above the threshold for which the differences in the quadrupoles become relevant. Should weak lensing data become available for this whole set, a quadrupole analysis may be expected to discriminate among different values of $Λ$.

Cosmological constant

Cold dark matter

Decoupling (probability)

Cosmic background radiation

10.1086/324185

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Cluster Correlation in Mixed Models

The Astrophysical Journal (2000)

A. Gardini S. A. Bonometto G. Murante Gustavo Yepes

We evaluate the dependence of the cluster correlation length, rc, on the mean intercluster separation, Dc, for three models with critical matter density, vanishing vacuum energy (Λ = 0), and COBE normalization: a tilted cold dark matter (tCDM) model (n = 0.8) and two blue mixed models with two light massive neutrinos, yielding Ωh = 0.26 and 0.14 (MDM1 and MDM2, respectively). All models approach the observational value of σ8 (and hence the observed cluster abundance) and are consistent with the observed abundance of damped Lyα systems. Mixed models have a motivation in recent results of neutrino physics; they also agree with the observed value of the ratio σ8/σ25, yielding the spectral slope parameter Γ, and nicely fit Las Campanas Redshift Survey (LCRS) reconstructed spectra. We use parallel AP3M simulations, performed in a wide box (of side 360 h-1 Mpc) and with high mass and distance resolution, enabling us to build artificial samples of clusters, whose total number and mass range allow us to cover the same Dc interval inspected through Automatic Plate Measuring Facility (APM) and Abell cluster clustering data. We find that the tCDM model performs substantially better than n = 1 critical density CDM models. Our main finding, however, is that mixed models provide a surprisingly good fit to cluster clustering data.

Normalization

Cold dark matter

10.1086/309498

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Simulations of Galaxy Clusters observed by Chandra

arXiv (Cornell University) (2001)

A. Gardini

A software package able to simulate imaging observations of galaxy clusters by the Chandra X-ray telescope is here presented. We start from high resolution N-body hydrodynamical simulations of galaxy clusters and assign to each gas particle a spectrum of emissivity, after assuming the MeKaL model. We then construct spatial images of the source differential flux which are used to create lists of incoming X-ray photons, preserving information on photon direction and energy. The photon lists are passed on to the Chandra simulator (MARX) to produce the final observation events. Background events are added to complete the simulation. Data analysis is currently in progress and simulated observations by other telescopes will become available in the future.

10.48550/arxiv.astro-ph/0110233

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