Simulations of self-interacting dark matter (SIDM) predict that dark matter should lag behind galaxies during a collision. If the interaction is mediated by a high-mass force carrier, the distribution of dark matter can also develop asymmetric dark matter tails. To search for this asymmetry, we compute the gravitational lensing properties of a mass distribution with a free {\em skewness} parameter. We apply this to the dark matter around the four central galaxies in cluster Abell~3827. In the galaxy whose dark matter peak has previously been found to be offset, we tentatively measure a skewness $s=0.23^{+0.05}_{-0.22}$ in the same direction as the peak offset. Our method may be useful in future gravitational lensing analyses of colliding galaxy clusters and merging galaxies.
We have made mass maps of three strong-lensing clusters, Abell 3827, Abell 2218 and Abell 1689, in order to test for mass-light offsets. The technique used is GRALE, which enables lens reconstruction with minimal assumptions, and specifically with no information about the cluster light being given. In the first two of these clusters, we find local mass peaks in the central regions that are displaced from the nearby galaxies by a few to several kpc. These offsets {\em could\/} be due to line of sight structure unrelated to the clusters, but that is very unlikely, given the typical levels of cha…
We measure alignments on scales of 1 Mpc $h^{-1}_{71}$ for galaxies in Abell 1689 ($z=0.18$) from an existing Hubble Space Telescope mosaic. We find evidence of galaxy alignment in the inner 500 $h^{-1}_{71}$ kpc. The alignment appears to be stronger towards the centre and is mostly present among the fainter galaxies, while bright galaxies are unaligned. This is consistent with a model where alignments originate from tidal locking.
We aim to obtain new insights into the internal dynamics of the cluster Abell 1240, showing the presence of two roughly symmetric radio relics, separated by ~2 h_70^-1 Mpc. Our analysis is mainly based on redshift data for 145 galaxies and on new photometric data. We also use X-ray data from the Chandra archive and photometric data from the SDSS (DR7). We combine galaxy velocities and positions to select 89 cluster galaxies and analyze the internal dynamics of the Abell 1237 + Abell 1240 cluster complex. We estimate similar redshifts for Abell 1237 and Abell 1240, <z>=0.1935 and <z>=0.1948, re…
The aim of the present work is to study the overall mass distribution of the galaxy clusters Abell 1351 and Abell 1995 using weak gravitational lensing. These clusters have got a very different mass structure and dynamical state, and are the two extremes from a larger sample of 38 X-ray luminous clusters of similar size and redshift. We measure shear values of faint background galaxies and correct for PSF anisotropies using the KSB+ method. Two-dimensional mass maps of the clusters are created using a finite-field mass reconstruction algorithm, and verified with aperture mass statistics. The m…
We present newly discovered radio emission in the galaxy cluster Abell 2443 which is (1) diffuse, (2) extremely steep spectrum, (3) offset from the cluster center, (4) of irregular morphology and (5) not clearly associated with any of the galaxies within the cluster. The most likely explanation is that this emission is a cluster radio relic, associated with a cluster merger. We present deep observations of Abell 2443 at multiple low frequencies (1425, 325 and 74 MHz) which help characterize the spectrum and morphology of this relic. Based on the curved spectral shape of the relic emission and …
We analyse the relation between the dynamical state of a cluster of galaxies and the activity (star formation and AGN) of its members. For the case of Abell 85 we find some evidence for an enhanced activity of both types in substructures which are in the early stage of merging with the cluster.
Abell 1995 is a puzzling galaxy cluster hosting a powerful radio halo, but it has not yet been recognized as a obvious cluster merger, as usually expected for clusters with diffuse radio emission. We aim at an exhaustive analysis of the internal structure of Abell 1995 to verify if this cluster is really dynamically relaxed, as reported in previous studies. We base our analysis on new and archival spectroscopic and photometric data for 126 galaxies in the field of Abell 1995. The study of the hot intracluster medium was performed on X-ray archival data. Based on 87 fiducial cluster members, we…
We present Suzaku observations of the galaxy cluster Abell 2029, which exploit Suzaku's low particle background to probe the ICM to radii beyond those possible with previous observations (reaching out to the virial radius), and with better azimuthal coverage. We find significant anisotropies in the temperature and entropy profiles, with a region of lower temperature and entropy occurring to the south east, possibly the result of accretion activity in this direction. Away from this cold feature, the thermodynamic properties are consistent with an entropy profile which rises, but less steeply th…
We used observations from the Giant Metrewave Radio Telescope to measure the atomic hydrogen gas content of 324 galaxies around the galaxy cluster Abell 370 at a redshift of z = 0.37 (a look-back time of ~4 billion years). The HI 21-cm emission from these galaxies was measured by coadding their signals using precise optical redshifts obtained with the Anglo-Australian Telescope. The average HI mass measured for all 324 galaxies is (6.6 +- 3.5)x10^9 solar masses, while the average HI mass measured for the 105 optically blue galaxies is (19.0 +- 6.5)x10^9 solar masses. The significant quantities…
We report on the detection of a giant radio halo in the cluster Abell 3404 as well as confirmation of the radio halo observed in Abell 141 (with linear extents $\sim 770$ kpc and $\sim 850$ kpc, respectively). We use the Murchison Widefield Array (MWA) in conjunction with the Australian Square Kilometre Array Pathfinder (ASKAP) and the Australia Telescope Compact Array (ATCA) to characterise the emission and intervening radio sources from $\sim100$-$1000$ MHz; power law models are fit to the spectral energy distributions with spectral indices $α_{88}^{1110} = -1.66 \pm 0.07$ and $α_{88}^{944} …
Abell 2146 ($z$ = 0.232) consists of two galaxy clusters undergoing a major merger. The system was discovered in previous work, where two large shock fronts were detected using the $\textit{Chandra X-ray Observatory}$, consistent with a merger close to the plane of the sky, caught soon after first core passage. A weak gravitational lensing analysis of the total gravitating mass in the system, using the distorted shapes of distant galaxies seen with ACS-WFC on $\textit{Hubble Space Telescope}$, is presented. The highest peak in the reconstruction of the projected mass is centred on the Brightes…
In large scale structure formation, massive systems assemble through the hierarchical merging of less massive ones. Galaxy clusters, being the most massive and thus the most recent collapsed structures, still grow by accreting smaller clusters and groups. In order to investigate the dynamical evolution of the intracluster medium, we perform a set of adiabatic hydrodynamical simulations of binary cluster mergers.
Observed galaxy clusters often exhibit X-ray morphologies suggestive of recent interaction with an infalling subcluster. Abell 3376 is a nearby (z=0.046) massive galaxy cluster whose bullet-shaped X-ray emission indicates that it may have undergone a recent collision. It displays a pair of Mpc-scale radio relics and its brightest cluster galaxy is located 970 h_70^-1 kpc away from the peak of X-ray emission, where the second brightest galaxy lies. We attempt to recover the dynamical history of Abell 3376. We perform a set of N-body adiabatic hydrodynamical simulations using the SPH code Gadget…
We present a deep and wide $I$ luminosity function for galaxies in Abell 1689 ($z=0.183$) from a mosaic of HST WFPC2 images covering $10'$ on the side. The main result of this work is the detection of a steep upturn in the dwarf galaxy LF, with $α\sim -2$. The dwarf to giant ratio appears to increase outwards, but this is because giant galaxies are missing in the cluster outskirts, indicating luminosity segregation. The red sequence LF has the same parameters, within errors, as the total LF, showing that the faint end upturn consists of red quiescent galaxies. We speculate that the upturn is c…
We present the first determination of the intrinsic triaxial shapes and tree-dimensional physical parameters of both dark matter (DM) and intra-cluster medium (ICM) for the galaxy cluster Abell 1689. We exploit the novel method we recently introduced (Morandi et al. 2010) in order to infer the tree-dimensional physical properties in triaxial galaxy clusters by combining jointly X-ray and strong lensing data. We find that Abell 1689 can be modeled as a triaxial galaxy cluster with DM halo axial ratios 1.24 +/- 0.13 and 2.37 +/- 0.11 on the plane of the sky and along the line of sight, respectiv…
We have discovered strong gravitational lensing features in the core of the nearby cluster Abell 3827 by analyzing Gemini South GMOS images. The most prominent strong lensing feature is a highly-magnified, ring-shaped configuration of four images around the central cD galaxy. GMOS spectroscopic analysis puts this source at z~0.2. Located ~20" away from the central galaxy is a secondary tangential arc feature which has been identified as a background galaxy with z~0.4. We have modeled the gravitational potential of the cluster core, taking into account the mass from the cluster, the BCG and oth…
In this paper we present new high sensitivity 153 MHz Giant Meterwave Radio Telescope follow-up observations of the diffuse steep spectrum cluster radio sources in the galaxy clusters Abell 521, Abell 697, Abell 1682. Abell 521 hosts a relic, and together with Abell 697 it also hosts a giant very steep spectrum radio halo. Abell 1682 is a more complex system with candidate steep spectrum diffuse emission. We imaged the diffuse radio emission in these clusters at 153 MHz, and provided flux density measurements of all the sources at this frequency. Our new flux density measurements, coupled with…
The dark matter in the galaxy cluster Abell 1689 is modelled as an isothermal sphere of neutrinos. New data on the $2d$ mass density allow an accurate description of its core and halo. The model has no "missing baryon problem" and beyond $2.1$ Mpc the baryons have the cosmic mass abundance. Combination of cluster data with the cosmic dark matter fraction -- here supposed to stem from the neutrinos -- leads to a solution of the dark matter riddle by left and right handed neutrinos with mass 1.847 +/- 0.016 eV. The thus far observed absence of neutrinoless double beta decay points to (quasi-) Di…
Combined LOFAR-uGMRT analysis of the diffuse radio emission in the massive clusters Abell 773 and Abell 1351
Istituto Nazionale di Astrofisica (INAF) - Istituto di Radioastronomia (IRA)（意大利国家天体物理研究所-射电天文研究所）；Dipartimento di Fisica e Astronomia (DIFA), Università di Bologna（博洛尼亚大学物理与天文学系）；Istituto Nazionale di Astrofisica – Istituto di Astrofisica Spaziale e Fisica Cosmica (IASF)（意大利国家天体物理研究所-空间天体物理学与宇宙物理学研究所）；University of Kashmir（克什米尔大学）；Hamburger Sternwarte, Universität Hamburg（汉堡天文台，汉堡大学）
Recent weak and strong lensing data of the galaxy cluster A1689 are modelled by dark fermions that are quantum degenerate within some core. The gas density, deduced from X-ray observations up to 1 Mpc and obeying a cored power law, is taken as input, while the galaxy mass density is modelled. An additional dark matter tail may arise from cold or warm dark matter, axions or non-degenerate neutrinos. The fit yields that the fermions are degenerate within a 430 kpc radius. The fermion mass is a few eV and the best case involves 3 active plus 3 sterile neutrinos of equal mass, for which we deduce …
We present a joint Suzaku and XMM-Newton analysis of the outskirts of the nearby galaxy cluster Abell 2199, the only nearby galaxy cluster to be observed with near complete azimuthal coverage with Suzaku. Using the XMM-Newton observations to correct for the effects of gas clumping, we find that the azimuthally averaged entropy profile in the outskirts follows a power law with a slope of $1.20 \pm 0.23$, statistically consistent with a slope of 1.1 predicted by non-radiative simulations for purely gravitational hierarchical structure formation. However, when divided into 10 sectors, the entropy…
We measure the local correlation between radio emission and Compton-$y$ signal across two galaxy clusters, Abell~399 and Abell~401, using maps from the Low-Frequency Array (LOFAR) and the Atacama Cosmology Telescope (ACT) + \Planck. These datasets allow us to make the first measurement of this kind at $\sim$arcminute resolution. We find that the radio brightness scales as $F_{\mathrm{radio}} \propto y^{1.5}$ for Abell~401 and $F_{\mathrm{radio}} \propto y^{2.8}$ for Abell~399. Furthermore, using \XMM data, we derive a sublinear correlation between radio and X-ray brightness for both the cluste…
Radio halos are faint radio sources usually located at the center of merging clusters of galaxies. These diffuse radio sources are rare, having so far been found only in about 30 clusters of galaxies, suggesting that particular conditions are needed to form and maintain them. It is interesting to investigate the presence of radio halos in close pairs of interacting clusters in order to possibly clarify their origin in relation to the evolutionary state of the merger. In this work, we study the case of the close pair of galaxy clusters A399 and A401. A401 is already known to contain a faint rad…
New high-resolution r band imaging of the brightest cluster galaxy (BCG) in Abell 85 (Holm 15A) was obtained using the Gemini Multi Object Spectrograph. These data were taken with the aim of deriving an accurate surface brightness profile of the BCG of Abell 85, in particular its central region. The new Gemini data show clear evidence of a previously unreported nuclear emission that is evident as a distinct light excess in the central kiloparsec of the surface brightness profile. We find that the light profile is never flat nor does it present a downward trend towards the center of the galaxy.…
We present a study of the luminosity and color properties of galaxies selected from a sample of 57 low-redshift Abell clusters. We utilize the non-parametric dwarf-to-giant ratio (DGR) and the blue galaxy fraction (fb) to investigate the clustercentric radial-dependent changes in the cluster galaxy population. Composite cluster samples are combined by scaling the counting radius by r200 to minimize radius selection bias. The separation of galaxies into a red and blue population was achieved by selecting galaxies relative to the cluster color-magnitude relation. The DGR of the red and blue gala…
Major mergers between massive clusters have a profound effect in the intracluster gas, which may be used as a probe of the dynamics of structure formation at the high end of the mass function. An example of such a merger is observed at the northern component of Abell 1758, comprised of two massive sub-clusters separated by approximately 750 kpc. One of the clusters exhibits an offset between the dark matter and the intracluster gas. We aim to determine whether it is possible to reproduce the specific morphological features of this cluster by means of a major merger. We perform dedicated SPH (s…
We present two new catalogues of superclusters of galaxies out to a redshit of z = 0.15, based on the Abell/ACO cluster redshift compilation maintained by one of us (HA). The first of these catalogues, the all-sky Main SuperCluster Catalogue (MSCC), is based on only the rich (A-) Abell clusters, and the second one, the Southern SuperCluster Catalogue (SSCC), covers declinations delta < -17 deg and includes the supplementary Abell S-clusters. A tunable Friends-of-Friends (FoF) algorithm was used to account for the cluster density decreasing with redshift and for different selection functions in…
Our ability to study the most remote supernova explosions, crucial for the understanding of the evolution of the high-redshift universe and its expansion rate, is limited by the light collection capabilities of telescopes. However, nature offers unique opportunities to look beyond the range within reach of our unaided instruments thanks to the light-focusing power of massive galaxy clusters. Here we report on the discovery of one of the most distant supernovae ever found, at redshift, z=1.703. Due to a lensing magnification factor of 4.3\pm0.3, we are able to measure a lightcurve of the supern…
We present a new 400ks Chandra X-ray observation and a GMRT radio observation at 325MHz of the merging galaxy cluster Abell 2146. The Chandra observation reveals detailed structure associated with the major merger event including the Mach M=2.1+/-0.2 bow shock located ahead of the dense subcluster core and the first known example of an upstream shock (M=1.6+/-0.1). Surprisingly, the deep GMRT observation at 325MHz does not detect any extended radio emission associated with either shock front. All other merging galaxy clusters with X-ray detected shock fronts, including the Bullet cluster, Abel…
Diffuse radio emission in galaxy clusters, and their connection with cluster mergers, are still debated. We seek to explore the internal dynamics of the radio halo cluster Abell 545. This cluster is also peculiar for hosting in its center a very bright, red, diffuse intracluster light due to an old, stellar population, so bright to be named as "star pile". Our analysis is based on redshift data for 110 galaxies. We identify 95 cluster members and analyze the cluster internal dynamics by combining galaxy velocities and positions. We also use both photometric and X-ray data. We estimate the clus…
We present original GMRT radio observations of the galaxy cluster Abell~725, at a redshift of 0.09, along with other archival observations. Our GMRT maps reveal two steep-spectrum diffuse filaments in the cluster, along with a previously reported arc-like structure, and a wide-angle tail (WAT) radio source associated with the Brightest Cluster Galaxy (BCG) at the periphery of the cluster. The bent morphology of the WAT indicates that its jets have been swept back by the dynamic pressure resulting from the motion of the BCG through the surrounding intracluster medium. The BCG associated with th…
Large-scale magnetic fields reveal themselves through diffuse synchrotron sources observed in galaxy clusters such as radio halos. Total intensity filaments of these sources have been observed in polarization as well, but only in three radio halos out of about one hundred currently known. In this paper we analyze new polarimetric Very Large Array data of the diffuse emission in the galaxy cluster Abell 523 in the frequency range 1-2 GHz. We find for the first time evidence of polarized emission on scales of ~ 2.5 Mpc. Total intensity emission is observed only in the central part of the source,…
We present VLA D-array HI observations of the RSCG42 and FGC1287 galaxy groups, in the outskirts of the Abell 1367 cluster. These groups are projected ~ 1.8 and 2.7 Mpc west from the cluster centre. The Arecibo Galaxy Environment survey provided evidence for HI extending over as much as 200kpc in both groups. Our new, higher resolution observations reveal that the complex HI features detected by Arecibo are in reality two extraordinary long HI tails extending for ~160 and 250 kpc, respectively, i.e., among the longest HI structures ever observed in groups of galaxies. Although in the case of R…
Abell 3667 is among the most well-studied galaxy clusters in the Southern Hemisphere. It is known to host two giant radio relics and a head-tail radio galaxy as the brightest cluster galaxy. Recent work has suggested the additional presence of a bridge of diffuse synchrotron emission connecting the North-Western radio relic with the cluster centre. In this work, we present full-polarization observations of Abell 3667 conducted with the Karoo Array Telescope at 1.33 and 1.82 GHz. Our results show both radio relics as well as the brightest cluster galaxy. We use ancillary higher-resolution data …
(Abstract abridged) The Abell 222 and 223 clusters are located at an average redshift z ~ 0.21 and are separated by 0.26 deg. Signatures of mergers have been previously found in these clusters, both in X-rays and at opticalwavelengths, thus motivating our study. In X-rays, they are relatively bright, and Abell 223 shows a double structure. A filament has also been detected between the clusters both at optical and X-ray wavelengths. We analyse the optical properties of these two clusters based on deep imaging in two bands, derive their galaxy minosity functions (GLFs) and correlate these proper…
A new step forward in realistic cluster lens mass modelling: Analysis of Hubble Frontier Field Cluster Abell S1063 from joint lensing, X-ray and galaxy kinematics data
We present an analysis of high-quality X-ray data out to the virial radius for the two galaxy clusters Abell 1246 and GMBCG J255.34805+64.23661 (J255) by means of our entropy-based SuperModel. For Abell 1246 we find that the spherically-averaged entropy profile of the intracluster medium (ICM) progressively flattens outwards, and that a nonthermal pressure component amounting to ~20% of the total is required to support hydrostatic equilibrium in the outskirts; there we also estimate a modest value C~1.6 of the ICM clumping factor. These findings agree with previous analyses on other cool-core,…
We report Chandra X-ray observations and optical weak-lensing measurements from Subaru/Suprime-Cam images of the double galaxy cluster Abell 2465 (z=0.245). The X-ray brightness data are fit to a beta-model to obtain the radial gas density profiles of the northeast (NE) and southwest (SW) sub-components, which are seen to differ in structure. We determine core radii, central temperatures, the gas masses within $r_{500c}$, and the total masses for the broader NE and sharper SW components assuming hydrostatic equilibrium. The central entropy of the NE clump is about two times higher than the SW.…
Massive galaxy clusters at intermediate redshift can magnify the flux of distant background sources by several magnitudes and we exploit this effect to search for lensed distant supernovae that may otherwise be too faint to be detected. A supernova search was conducted at near infrared wavelengths using the ISAAC instrument at the VLT. The galaxy clusters Abell 1689, Abell 1835 and AC114 were observed at multiple epochs of 2 hours of exposure time, separated by a month. Image-subtraction techniques were used to search for transient objects with light curve properties consistent with supernovae…
The connection of cluster mergers with the presence of extended, diffuse radio sources in galaxy clusters is still being debated. In this paper we aim to obtain new insights into the internal dynamics of Abell 959, showing evidence of a diffuse radio source, analyzing velocities and positions of member galaxies. Our analysis is based on redshift data for 107 galaxies in the cluster field acquired at the Telescopio Nazionale Galileo. We also use photometric data from the Sloan Digital Sky Survey (Data Release 6). We combine galaxy velocities and positions to select 81 galaxies recognized as clu…
We examine Suzaku, XMM-Newton, and Chandra observations of the Abell 2029/2033 system to investigate the nature of a bridge of X-ray emission joining the two galaxy clusters. By modelling the contributions from the outskirts of the two clusters, and excluding the emission from the southern infalling group and the background group LOS9, we find a significant excess of X-ray emission between the two clusters at the level of 6.5-7.0$σ$, depending on the choice of model, that cannot be explained by the overlap of the clusters. This excess component to the surface brightness is consistent with bein…
The pre-merging system of galaxy clusters Abell 3391-Abell 3395 located at a mean redshift of 0.053 has been observed at 1 GHz in an ASKAP/EMU Early Science observation as well as in X-rays with eROSITA. The projected separation of the X-ray peaks of the two clusters is $\sim$50$'$ or $\sim$ 3.1 Mpc. Here we present an inventory of interesting radio sources in this field around this cluster merger. While the eROSITA observations provide clear indications of a bridge of thermal gas between the clusters, neither ASKAP nor MWA observations show any diffuse radio emission coinciding with the X-ray…
Off-axis collisions between galaxy clusters may induce the phenomenon of sloshing, causing dense gas to be dragged from the cool core of a cluster, resulting in a spiral of enhanced X-ray emission. Abell 2199 displays signatures of sloshing in its core and it is possible that the orbital plane of the collision is seen nearly edge-on. We aim to evaluate whether the features of Abell 2199 can be explained by a sloshing spiral seen under a large inclination angle. To address this, we perform tailored hydrodynamical $N$-body simulations of a non-frontal collision with a galaxy group of $M_{200}=1.…
The intracluster plasma of Abell 2052 exhibits in X-rays a spiral structure extending more than 250 kpc, which is comprised of cool gas. This feature is understood to be the result of gas sloshing caused by the off-axis collision with a smaller subcluster. We aim to recover the dynamical history of Abell 2052 and to reproduce the broad morphology of the spiral feature. To this end, we perform hydrodynamical $N$-body simulations of cluster collisions. We obtain two regimes that adequately reproduce the desired features. The first scenario is a close encounter and a recent event (0.8 Gyr since p…
We present a new analysis of HST, Spitzer telescope imaging and VLT imaging and spectroscopic data of a bright lensed galaxy at $z$=1.0334 in the lensing cluster Abell~2667. Using this high-resolution imaging we present an updated lens model that allows us to fully understand the lensing geometry and reconstruct the lensed galaxy in the source plane. This giant arc gives a unique opportunity to peer into the structure of a high-redshift disk galaxy. We find that the lensed galaxy of Abell 2667 is a typical spiral galaxy with morphology similar to the structure of its counterparts at higher red…
The results of Suzaku observations of the outskirts of Abell 3395 including a large-scale structure filament toward Abell 3391 are presented. We measured temperature and abundance distributions from the southern outskirt of Abell 3395 to the north at the virial radius, where a filament structure has been found in the former X-ray and Sunyaev-Zel'dovich effect observations between Abell 3391 and 3395. The overall temperature structure is consistent with the universal profile proposed by Okabe et al.(2014) for relaxed clusters except for the filament region. A hint of the ICM heating is found be…
We present a strong-lensing analysis of four massive galaxy clusters imaged with the Hubble Space Telescope in the Reionization Lensing Cluster Survey. We use a Light-Traces-Mass technique to uncover sets of multiply images and constrain the mass distribution of the clusters. These mass models are the first published for Abell S295 and MACS J0159.8-0849, and are improvements over previous models for Abell 697 and MACS J0025.4-1222. Our analysis for MACS J0025.4-1222 and Abell S295 shows a bimodal mass distribution supporting the merger scenarios proposed for these clusters. The updated model f…
Self-interactions of dark matter particles can potentially lead to an observable separation between the dark matter halo and the stars of a galaxy moving through a region of large dark matter density. Such a separation has recently been observed in a galaxy falling into the core of the galaxy cluster Abell 3827. We estimated the DM self-interaction cross section needed to reproduce the observed effects and find that the sensitivity of Abell 3827 has been significantly overestimated in a previous study. Our corrected estimate is $\tildeσ/m_\text{DM} \sim 3\:\text{cm}^2\:\text{g}^{-1}$ when self…
Galaxy clusters with signs for a recent merger show in many cases extended diffuse radio features. This emission originates from relativistic electrons which suffer synchrotron losses due to the intra-cluster magnetic field. The mechanisms of the particle acceleration and the properties of the magnetic field are still poorly understood. We search for diffuse radio emission in galaxy clusters. Here, we study the complex galaxy cluster Abell 2069, for which X-ray observations indicate a recent merger. We investigate the cluster's radio continuum emission by deep Westerbork Synthesis Radio Telesc…
Based on an extensive redshift survey for galaxy cluster Abell 2029 and Coma, we measure the luminosity functions (LFs), stellar mass functions (SMFs) for the entire cluster member galaxies. Most importantly, we measure the velocity dispersion functions (VDFs) for quiescent members. The MMT/Hectospec redshift survey for galaxies in A2029 identifies 982 spectroscopic members; for 838 members we derive the central velocity dispersion from the spectroscopy. Coma is the only other cluster surveyed as densely. The LFs, SMFs and VDFs for A2029 and Coma are essentially identical. The SMFs of the clus…
We present results from an X-ray and radio study of the merging galaxy cluster Abell 115. We use the full set of 5 Chandra observations taken of A115 to date (360 ks total integration) to construct high-fidelity temperature and surface brightness maps. We also examine radio data from the Very Large Array at 1.5 GHz and the Giant Metrewave Radio Telescope at 0.6 GHz. We propose that the high X-ray spectral temperature between the subclusters results from the interaction of the bow shocks driven into the intracluster medium by the motion of the subclusters relative to one another. We have identi…
Galaxy clusters undergo mergers that can generate extended radio sources called radio relics. Radio relics are the consequence of merger-induced shocks that propagate in the intra cluster medium (ICM). In this paper we analyse the radio, optical and X-ray data from a candidate galaxy cluster that has been selected from the radio emission coming from a candidate radio relic detected in NRAO VLA Sky Survey (NVSS). Our aim is to clarify the nature of this source and prove that under certain conditions radio emission from radio relics can be used to trace relatively low-mass galaxy clusters. We ha…
The thermal and kinematic Sunyaev-Zeldovich effect in galaxy clusters and filaments using multifrequency temperature maps of the cosmic microwave background: Abell 399--Abell 401 cluster pair case study
We present the analysis of deep optical imaging of the galaxy cluster Abell 133 with the IMACS instrument on Magellan. Our multi-band photometry enables stellar mass measurements in the cluster member galaxies down to a mass limit of $M_\star=3\times10^8\,M_\odot$ ($\approx 0.1$ of the Large Magellanic Cloud stellar mass). We observe a clear difference in the spatial distribution of large and dwarf galaxies within the cluster. Modeling these galaxies populations separately, we can confidently track the distribution of stellar mass locked in the galaxies to the cluster's virial radius. The exte…
