The Abell 780 cluster, better known as the Hydra A cluster, has been thouroughly analyzed in X-rays. However, little is known on its optical properties. We derive the galaxy luminosity function (GLF) in this apparently relaxed cluster, and search for possible environmental effects by comparing the GLFs in various regions, and by looking at the galaxy distribution at large scale around Abell 780. Our study is based on optical images obtained with the ESO 2.2m telescope and WFI camera in the B and R bands, covering a total region of 67.22x32.94 arcmin^2, or 4.235x2.075 Mpc^2 for a cluster redshift of 0.0539. In a region of 500 kpc radius around the cluster centre, the GLF in the R band shows a double structure, with a broad and flat bright part and a flat faint end that can be fit by a power law with an index alpha=-0.85+-0.12 in the 20.25<R<21.75 interval. If we divide this 500 kpc radius region in North+South or East+West halves, we find no clear difference between the GLFs in these smaller regions. No obvious large scale structure is apparent within 5 Mpc from the cluster, based on galaxy redshifts and magnitudes collected from the NED database in a much larger region than that covered by our data, suggesting that there is no major infall of material in any preferential direction. However, the Serna-Gerbal method reveals the presence of a gravitationally bound structure of 27 galaxies, which includes the cD, and of a more strongly gravitationally bound structure of 14 galaxies. These optical results agree with the overall relaxed structure of Abell 780 previously derived from X-ray analyses.
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} …
We present here the weak gravitational lensing detection of four nearby galaxy clusters in the southern sky: Abell 2029, Abell 85, Abell 1606 and Abell 2457. The weak lensing detections of Abell 1606 and Abell 2457 are the first in the literature. This work capitalizes on the wide field of view of the Dark Energy Camera at the Cerro Tololo Inter-American Observatory, which we use to obtain deep, multi-wavelength imaging of all targets. We publish maps of the clusters' projected mass distributions, and obtain the $M_{200}$ of their clusters through NFW profile fits to the two-dimensional tangen…
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）
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…
Constraints from the Giant Arc in Abell 370. A New Framework for Understanding Systematic Errors in Cluster Lens Modeling. IV. Constraints from the Giant Arc in Abell 370
We present a detailed analysis of a cool-core galaxy cluster Abell 3017, at a redshift of z=0.219, which has been identified to be merging with its companion cluster Abell 3016. This study has made use of X-ray Chandra, UV (GALEX), optical (ESO/VLT), mid-infrared (WISE), and radio uGMRT observations of this cluster. Using various image processing techniques, such as unsharp masking, 2-d fits using Beta models, contour binning and the use of surface brightness profiles, we show the existence of a pair of X-ray cavities, at a projected distance of $\sim$20'' (70 kpc) and $\sim$16'' (57 kpc), res…
We examine Suzaku, XMM-Newton, and Chandra observations of the Abell 2029/2033 system to investigate the nature of a bridge of X-ray emission joining the two galaxy clusters. By modelling the contributions from the outskirts of the two clusters, and excluding the emission from the southern infalling group and the background group LOS9, we find a significant excess of X-ray emission between the two clusters at the level of 6.5-7.0$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…
Testing the interaction of dark energy to dark matter through the analysis of virial relaxation of clusters Abell Clusters A586 and A1689 using realistic density profiles
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…
We have selected Abell 3266 to search for ram-pressure induced star formation as a global property of a merging cluster. Abell 3266 (z = 0.0594) is a high mass cluster that features a high velocity dispersion, an infalling subcluster near to the line of sight, and a strong shock front. These phenomena should all contribute to making Abell 3266 an optimum cluster to see the global effects of RPS induced star formation. Using archival X-ray observations and published optical data, we cross-correlate optical spectral properties ([OII, H$β$]), indicative of starburst and post starburst, respective…
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…
We present the study of the internal dynamics of the intriguing galaxy cluster Abell 1703, a system hosting a probable giant radio halo whose dynamical status is still controversial. Our analysis is based on unpublished spectroscopic data acquired at the Italian Telescopio Nazionale Galileo and data publicly available in the literature. We also use photometric data from the Sloan Digital Sky Survey. We select 147 cluster members and compute the cluster redshift $\left<z\right>\sim 0.277$ and the global line-of-sight velocity dispersion $σ_{\rm v}\sim 1300$ km/s. We infer that Abell 1703 is a m…
We investigate gravitational lensing in the context of the MOG modified theory of gravity. Using a formulation of the theory with no adjustable or fitted parameters, we present the MOG equations of motion for slow, nonrelativistic test particles and for ultrarelativistic test particles, such as rays of light. We demonstrate how the MOG prediction for the bending of light can be applied to astronomical observations. Our investigation first focuses on a small set of strong lensing observations where the properties of the lensing objects are found to be consistent with the predictions of the theo…
The Velocity Dispersion Function of Very Massive Galaxy Clusters: Abell 2029 and Coma
基于对星系团Abell 2029和后发座星系团的广泛红移观测，我们测量了整个星系团成员星系的光度函数和恒星质量函数。最重要的是，我们测量的速度色散函数（VDFs）的静态成员。MMT/Hectospec红移调查的星系在A2029确定982光谱成员，838名成员，我们得出的中心速度色散的光谱。后发座是唯一一个被调查得如此密集的星团。A2029和Coma的LF、SMF和VDF基本相同。簇的SMF与模拟一致。静止星系的A2029和后发星系的速度色散比场星系的速度色散有一个明显更陡的斜率$\lesssim 100$ km s $^{-1}$。在速度色散$\gtrsim 250$ km s $^{-1}$时，星系团VDFs也超过了磁场。星系团VDF和场VDF之间的差异是对模拟和宇宙结构形成的潜在重要测试。
