scholarly journals The 2001 Australian Galaxy Cluster Workshop

2002 ◽  
Vol 19 (2) ◽  
pp. 265-276
Author(s):  
Michael J. Drinkwater
Keyword(s):  
Galaxy Cluster ◽  
Clusters Of Galaxies ◽  
The Many ◽  
Cluster Workshop

AbstractThe first ‘Australian Cluster Workshop’ was held at the Australia Telescope National Facility in Sydney on 2001 February 6. The aim of the workshop was to bring together the many and varied groups working on clusters of galaxies in Australia, to forge new multi-disciplinary links, and to generate enthusiasm and support for new cluster work and further cluster meetings in Australia. In this paper I present a summary of the workshop as well as some additional review material intended to place current Australian research in a broader perspective, looking ahead to the major issues still to be addressed.

Imaging the Cosmic Microwave Background with the Arcminute Cosmology Bolometer Array Receiver

2005 ◽  
Vol 216 ◽  
pp. 43-50
Author(s):  
J. B. Peterson ◽  
A. K. Romer ◽  
P. L. Gomez ◽  
P. A. R. Ade ◽  
J. J. Bock ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Cosmic Microwave Background ◽  
Cosmological Parameters ◽  
Galaxy Cluster ◽  
Clusters Of Galaxies ◽  
Microwave Background ◽  
Bolometer Array ◽  
The Galaxy ◽  
Millimeter Wave Receiver ◽  
Array Receiver

The Arcminute Cosmology Bolometer Array Receiver (Acbar) is a multifrequency millimeter-wave receiver optimized for observations of the Cosmic Microwave Background (CMB) and the Sunyaev-Zel'dovich (SZ) effect in clusters of galaxies. Acbar was installed on the 2.1 m Viper telescope at the South Pole in January 2001 and the results presented here incorporate data through July 2002. The power spectrum of the CMB at 150 GHz over the range ℓ = 150 — 3000 measured by Acbar is presented along with estimates for the values of the cosmological parameters within the context of ΛCDM models. The inclusion of ΩΛ greatly improves the fit to the power spectrum. Three-frequency images of the SZ decrement/increment are also presented for the galaxy cluster 1E0657–67.

scholarly journals Clusters of Galaxies

1980 ◽  
Vol 5 ◽  
pp. 699-714 ◽  
Author(s):  
Neta A. Bahcall
Keyword(s):  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Clusters Of Galaxies ◽  
Groups Of Galaxies ◽  
Formation And Evolution ◽  
The Rich ◽  
The Many ◽  
The Universe

AbstractClusters and groups of galaxies contain the majority of galaxies in the universe. The rich clusters, while less numerous than the many poor groups, are the densest and largest systems known, and can be easily recognized and studied even at relatively large distances. Their study is important for understanding the formation and evolution of clusters and galaxies, and for a determination of the large-scale structure in the universe.

scholarly journals Deprojecting galaxy-cluster cold fronts: evidence for bulk, magnetized spiral flows

2020 ◽  
Vol 495 (4) ◽  
pp. 4392-4418 ◽  
Author(s):  
Yossi Naor ◽  
Uri Keshet ◽  
Qian H S Wang ◽  
Ido Reiss
Keyword(s):  
Mach Number ◽  
Galaxy Cluster ◽  
Clusters Of Galaxies ◽  
High Quality ◽  
Thermal Pressure ◽  
Cold Fronts ◽  
Significance Levels ◽  
The Mean ◽  
Tangential Discontinuities ◽  
Spiral Type

ABSTRACT Tangential discontinuities known as cold fronts (CFs) are abundant in groups and clusters of galaxies (GCs). The relaxed, spiral-type CFs were initially thought to be isobaric, but a significant, $10{{\ \rm per\ cent}}$–$20{{\ \rm per\ cent}}$ jump in the thermal pressure Pt was reported when deprojected CFs were stacked, interpreted as missing Pt below the CFs (i.e. at smaller radii r) due to a locally enhanced non-thermal pressure Pnt. We report a significant (∼4.3σ) deprojected jump in Pt across a single sharp CF in the Centaurus cluster. Additional seven CFs are deprojected in the GCs A2029, A2142, A2204, and Centaurus, all found to be consistent (stacked: ∼1.9σ) with similar pressure jumps. Combining our sample with high quality deprojected CFs from the literature indicates pressure jumps at significance levels ranging between 2.7σ and 5.0σ, depending on assumptions. Our nominal results are consistent with Pnt ≃ (0.1–0.3)Pt just below the CF. We test different deprojection and analysis methods to confirm that our results are robust, and show that without careful deprojection, an opposite pressure trend may incorrectly be inferred. Analysing all available deprojected data, we also find: (i) small variations around the mean density and temperature CF contrast q within each GC, monotonically increasing with the GC mass M200 as $q\propto M_{200}^{0.23\pm 0.04}$; (ii) hydrostatic mass discontinuities indicating fast bulk tangential flows below all deprojected CFs, with a mean Mach number ∼0.76; and (iii) the newly deprojected CFs are consistent (stacked: ∼2.9σ) with a $1.25^{+0.09}_{-0.08}$ metallicity drop across the CF. These findings suggest that GCs quite generally harbour extended spiral flows.

scholarly journals LOFAR detection of a low-power radio halo in the galaxy cluster Abell 990

2020 ◽  
Vol 501 (1) ◽  
pp. 576-586
Author(s):  
D N Hoang ◽  
T W Shimwell ◽  
E Osinga ◽  
A Bonafede ◽  
M Brüggen ◽  
...  
Keyword(s):  
Low Frequency ◽  
Galaxy Cluster ◽  
Clusters Of Galaxies ◽  
Radio Halo ◽  
The Galaxy ◽  
Major Merger ◽  
Murchison Widefield Array ◽  
Low X ◽  
Massive Clusters ◽  
Radio Power

ABSTRACT Radio haloes are extended (∼Mpc), steep spectrum sources found in the central region of dynamically disturbed clusters of galaxies. Only a handful of radio haloes have been reported to reside in galaxy clusters with a mass $M_{500}\lesssim 5\times 10^{14}\, \mathrm{ M}_\odot$. In this paper, we present a LOw Frequency ARray (LOFAR) 144 MHz detection of a radio halo in the galaxy cluster Abell 990 with a mass of $M_{500}=(4.9\pm 0.3)\times 10^{14}\, \mathrm{ M}_\odot$. The halo has a projected size of ${\sim} 700\, {\rm kpc}$ and a flux density of $20.2\pm 2.2\, {\rm mJy}$ or a radio power of $1.2\pm 0.1\times 10^{24}\, {\rm W\, Hz}^{-1}$ at the cluster redshift (z = 0.144) that makes it one of the two haloes with the lowest radio power detected to date. Our analysis of the emission from the cluster with Chandra archival data using dynamical indicators shows that the cluster is not undergoing a major merger but is a slightly disturbed system with a mean temperature of $5\, {\rm keV}$. The low X-ray luminosity of $L_{\mathrm{ X}}=(3.66\pm 0.08)\times 10^{44}\, {\rm erg\, s}^{-1}$ in the 0.1–2.4 keV band implies that the cluster is one of the least luminous systems known to host a radio halo. Our detection of the radio halo in Abell 990 opens the possibility of detecting many more haloes in poorly explored less massive clusters with low-frequency telescopes such as LOFAR, Murchison Widefield Array (MWA, Phase II), and upgraded Giant Metrewave Radio Telescope (uGMRT).

scholarly journals Galaxies and clusters of galaxies as peak patches of the density field

2019 ◽  
Vol 490 (2) ◽  
pp. 1693-1696 ◽  
Author(s):  
Masataka Fukugita ◽  
Hans Böhringer
Keyword(s):  
Gravitational Lensing ◽  
Mass Density ◽  
Galaxy Cluster ◽  
Mass Range ◽  
Mass Function ◽  
Clusters Of Galaxies ◽  
Density Fraction ◽  
The Galaxy ◽  
Consistent Picture ◽  
Low Mass

ABSTRACT The mass function of galaxies and clusters of galaxies can be derived observationally based on different types of observations. In this study we test if these observations can be combined to a consistent picture which is also in accord with structure formation theory. The galaxy data comprise the optical galaxy luminosity function and the gravitational lensing signature of the galaxies, while the galaxy cluster mass function is derived from the X-ray luminosity distribution of the clusters. We show the results of the comparison in the form of the mass density fraction that is contained in collapsed objects relative to the mean matter density in the Universe. The mass density fraction in groups and clusters of galaxies extrapolated to low masses agrees very well with that of the galaxies: both converge at the low mass limit to a mass fraction of about 28 per cent if the outer radii of the objects are taken to be r200. Most of the matter contained in collapsed objects is found in the mass range $M_{200} \sim 10^{12}\!-\!10^{14}\, h^{-1}_{70} \, \mathrm{M}_\odot$, while a larger amount of the cosmic matter resides outside of r200 of collapsed objects.

scholarly journals Galaxy and Mass Assembly (GAMA): Selection of the Most Massive Clusters

2014 ◽  
Vol 11 (S308) ◽  
pp. 215-216
Author(s):  
Héctor J. Ibarra-Medel ◽  
Maritza Lara-López ◽  
Omar López-Cruz
Keyword(s):  
Galaxy Cluster ◽  
Mass Range ◽  
Clusters Of Galaxies ◽  
The Galaxy ◽  
Sunyaev Zel'dovich Effect ◽  
Point Correlation ◽  
Point Correlation Function ◽  
Mass Assembly ◽  
Massive Clusters ◽  
Selection Of

AbstractWe have developed a galaxy cluster finding technique based on the Delaunay Tessellation Field Estimator (DTFE) combined with caustic analysis. Our method allows us to recover clusters of galaxies within the mass range of $10^{12}$ to $10^{16}\ \mathcal{M}_{\odot}$. We have found a total of 113 galaxy clusters in the Galaxy and Mass Assembly survey (GAMA). In the corresponding mass range, the density of clusters found in this work is comparable to the density traced by clusters selected by the thermal Sunyaev Zel'dovich Effect; however, we are able to cover a wider mass range. We present the analysis of the two-point correlation function for our cluster sample.

scholarly journals Quasar Activity in Rich Galaxy Clusters

1992 ◽  
Vol 9 ◽  
pp. 695-696
Author(s):  
H. K. C. Yee ◽  
E. Ellingson
Keyword(s):  
Spatial Distribution ◽  
Galaxy Clusters ◽  
Galaxy Cluster ◽  
Clusters Of Galaxies ◽  
Spatial Covariance ◽  
Class 1 ◽  
The Galaxy ◽  
Cluster Environment

We have carried out a number of imaging surveys of fields around quasars to study their global environments (e.g. Yee and Green 1987, Ellingson, Yee and Green 1991). The richness of the galaxy cluster environment of each quasar was determined using the galaxy-quasar spatial covariance amplitude, a quantity which is normalized for the expected luminosity and spatial distribution of galaxies (Longair and Seldner 1978, Yee and Green 1987). We find that ~40% of the brightest radio-loud quasars inhabit rich clusters of galaxies (Abell class 1 or higher) at z≳0.5 whereas only fainter AGN inhabit clusters at more recent epochs (Figure 1). This can be understood if quasars in rich clusters evolve much faster than those in poor environments.

scholarly journals Optical Identification of Rosat All-Sky Survey Galaxy Cluster Candidates

1994 ◽  
Vol 161 ◽  
pp. 653-657
Author(s):  
B.J. McLean ◽  
H. Böhringer ◽  
R. Burg ◽  
R. Giacconi ◽  
J.P. Huchra ◽  
...  
Keyword(s):  
Correlation Functions ◽  
Large Scale ◽  
Visual Inspection ◽  
Galaxy Cluster ◽  
Clusters Of Galaxies ◽  
Plate Material ◽  
Optical Identification ◽  
Luminosity Functions ◽  
Sky Survey ◽  
The Universe

Clusters of galaxies are used to study large scale structure and evolution in the universe. The luminosity functions of clusters can be used to investigate their evolutionary effects while their spatial and angular correlation functions are a measure of large-scale clustering. There are, however, many problems with the traditional cluster catalogues that were derived by visual inspection of plate material. The widely used Abell catalogue (Abell 1958) has been shown to have significant problems in homogeneity and completeness (Postman et al. 1986).

Clusters of galaxies associated with quasars. II - Galaxy cluster dynamics

1991 ◽  
Vol 378 ◽  
pp. 476 ◽  
Author(s):  
E. Ellingson ◽  
R. F. Green ◽  
H. K. C. Yee
Keyword(s):  
Galaxy Cluster ◽  
Clusters Of Galaxies

Clusters of galaxies and their outskirts: star formation rate and stellar mass

2021 ◽  
pp. 99-104
Author(s):  
F. G. KOPYLOVA ◽  
A .I. KOPYLOV
Keyword(s):  
Star Formation ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Galaxy Cluster ◽  
Stellar Mass ◽  
Clusters Of Galaxies ◽  
Cluster Centre ◽  
Data Release ◽  
The Galaxy ◽  
Central Regions

We investigate the specific star formation rate of galaxies as a function of distance from the cluster centre (R 3R200) in a sample of 40 groups and clusters of galaxies of the local Universe. Using the SDSS Data Release 10, we find that the fraction of galaxies with quenched star formation is maximal in the central regions of the galaxy clusters and equals, on the average, 0.81; it decreases to 0.44 outside of the projected "splashback" radius Rsp, which we found from the observed profile of galaxy cluster, but still remains higher than that in the field by 27%.

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