Search results for "Galaxy groups and clusters"
showing 8 items of 8 documents
Pressure of the hot gas in simulations of galaxy clusters
2016
We analyze the radial pressure profiles, the ICM clumping factor and the Sunyaev-Zel'dovich (SZ) scaling relations of a sample of simulated galaxy clusters and groups identified in a set of hydrodynamical simulations based on an updated version of the TreePM-SPH GADGET-3 code. Three different sets of simulations are performed: the first assumes non-radiative physics, the others include, among other processes, AGN and/or stellar feedback. Our results are analyzed as a function of redshift, ICM physics, cluster mass and cluster cool-coreness or dynamical state. In general, the mean pressure profiles obtained for our sample of groups and clusters show a good agreement with X-ray and SZ observa…
Luminosity function for galaxy clusters
2014
AbstractWe constructed and studied the luminosity function of 6188 galaxy clusters. This was performed by counting brightness of galaxies belonging to clusters in the PF catalogue, taking galaxy data from MRSS. Our result shows that the investigated structures are characterized by a luminosity function different from that of optical galaxies and radiogalaxies (Machalski & Godłowski 2000). The implications of this result for theories of galaxy formation are briefly discussed.
Redshifts of southern clusters. II
1991
New redshifts are given for 21 clusters of galaxies from the Abell, Corwin, and Olowin Rich Cluster Catalogue. The redshift of the brightest cluster galaxy - where the brightest member is brighter than 15.5 - is employed as an indicator of the mean cluster redshift. The redshifts of first-, second-, and third-ranked galaxies are shown to agree, confirming the value of the survey procedure, although some clusters require more information than simply the redshift of the brightest cluster. 7 refs.
CCDuvbyβ photometry of the young open cluster NGC 663
2004
NGC 663 is a young, moderately rich open cluster, known to contain one of the largest fractions of Be stars among all galactic clusters. In this work we present CCD uvby-beta photometry for stars in its central area. We have used these data to obtain the main cluster physical parameters. We find that the reddening is highly variable, with values ranging from E(b-y)=0.639+/-0.032 in the central part to E(b-y)=0.555+/-0.038 in the south-east. The distance modulus is found to be 11.6+/-0.1 mag.(2.1 Kpc), and the age log t=7.4+/-0.1 years (25+7/-5 Myr). The age obtained is consistent with the interpretation of the Be phenomenon as an evolutionary effect.
Shell-like structures in our cosmic neighbourhood
2016
Signatures of the processes in the early Universe are imprinted in the cosmic web. Some of them may define shell-like structures characterised by typical scales. We search for shell-like structures in the distribution of nearby rich clusters of galaxies drawn from the SDSS DR8. We calculate the distance distributions between rich clusters of galaxies, and groups and clusters of various richness, look for the maxima in the distance distributions, and select candidates of shell-like structures. We analyse the space distribution of groups and clusters forming shell walls. We find six possible candidates of shell-like structures, in which galaxy clusters have maxima in the distance distribution…
EDGE: explorer of diffuse emission and gamma-ray burst explosions
2009
How structures on various scales formed and evolved from the early Universe up to present time is a fundamental question of astrophysical cosmology. EDGE will trace the cosmic history of the baryons from the early generations of massive star by Gamma-Ray Burst (GRB) explosions, through the period of cluster formation, down to very low redshifts, when between a third and one half of the baryons are expected to reside in cosmic filaments undergoing gravitational collapse by dark matter (Warm Hot Intragalactic Medium: WHIM). In addition EDGE, with its unprecedented observational capabilities, will provide key results on several other topics. The science is feasible with a medium class mission …
Mass-Metallicity Relation from Cosmological Hydrodynamical Simulations and X-ray Observations of Galaxy Groups and Clusters
2018
Recent X-ray observations of galaxy clusters show that the distribution of intra-cluster medium (ICM) metallicity is remarkably uniform in space and time. In this paper, we analyse a large sample of simulated objects, from poor groups to rich clusters, to study the dependence of the metallicity and related quantities on the mass of the systems. The simulations are performed with an improved version of the Smoothed-Particle-Hydrodynamics \texttt{GADGET-3} code and consider various astrophysical processes including radiative cooling, metal enrichment and feedback from stars and active galactic nuclei (AGN). The scaling between the metallicity and the temperature obtained in the simulations ag…
Is ram-pressure stripping an efficient mechanism to remove gas in galaxies?
2017
We study how the gas in a sample of galaxies (M* > 10e9 Msun) in clusters, obtained in a cosmological simulation, is affected by the interaction with the intra-cluster medium (ICM). The dynamical state of each elemental parcel of gas is studied using the total energy. At z ~ 2, the galaxies in the simulation are evenly distributed within clusters, moving later on towards more central locations. In this process, gas from the ICM is accreted and mixed with the gas in the galactic halo. Simultaneously, the interaction with the environment removes part of the gas. A characteristic stellar mass around M* ~ 10e10 Msun appears as a threshold marking two differentiated behaviours. Below this mas…