A giant radio bridge connecting two clusters in Abell 1758
A. Botteon, R. J. van Weeren, G. Brunetti, F. de Gasperin, H. T. Intema, E. Osinga, G. Di Gennaro, T. W. Shimwell, A. Bonafede, M. Brüggen, R. Cassano, V. Cucit… 展开作者
A. Botteon, R. J. van Weeren, G. Brunetti, F. de Gasperin, H. T. Intema, E. Osinga, G. Di Gennaro, T. W. Shimwell, A. Bonafede, M. Brüggen, R. Cassano, V. Cuciti, D. Dallacasa, F. Gastaldello, S. Mandal, M. Rossetti, H. J. A. Röttgering
备注：
6 pages, 4 figures, 1 table. Accepted for publication in MNRAS Letters
Collisions between galaxy clusters dissipate enormous amounts of energy in the intra-cluster medium (ICM) through turbulence and shocks. In the process, Mpc-scale diffuse synchrotron emission in form of radio halos and relics can form. However, little is known about the very early phase of the collision. We used deep radio observations from 53 MHz to 1.5 GHz to study the pre-merging galaxy clusters A1758N and A1758S that are $\sim2$ Mpc apart. We confirm the presence of a giant bridge of radio emission connecting the two systems that was reported only tentatively in our earlier work. This is the second large-scale radio bridge observed to date in a cluster pair. The bridge is clearly visible in the LOFAR image at 144 MHz and tentatively detected at 53 MHz. Its mean radio emissivity is more than one order of magnitude lower than that of the radio halos in A1758N and A1758S. Interestingly, the radio and X-ray emissions of the bridge are correlated. Our results indicate that non-thermal phenomena in the ICM can be generated also in the region of compressed gas in-between infalling systems.
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 Hateful Eight: Connecting Massive Substructures in Galaxy Clusters like Abell 2744 to their Dynamical Assembly State using the Magneticum Simulations
Galaxy clusters are the most massive gravitationally bound structures in the Universe. They grow by accreting smaller structures in a merging process that produces shocks and turbulence in the intra-cluster gas. We observed a ridge of radio emission connecting the merging galaxy clusters Abell 0399 and Abell 0401 with the Low Frequency Array (LOFAR) at 140 MHz. This emission requires a population of relativistic electrons and a magnetic field located in a filament between the two galaxy clusters. We performed simulations to show that a volume-filling distribution of weak shocks may re-accelera…
Magnetic properties of the Abell 3391-3395 system revealed using wide-field MeerKAT polarimetry
Hamburger Sternwarte, University of Hamburg（汉堡天文台，汉堡大学）；GEPI, Observatoire de Paris, Université PSL, CNRS（巴黎天文台GEPI，巴黎文理研究大学，法国国家科学研究中心）；Department of Physics & Electronics, Rhodes University（罗德斯大学物理与电子系）；Departamento de Física de la Tierra y Astrofísica & IPARCOS-UCM, Universidad Complutense de Madrid（马德里康普顿斯大学地球与天体物理学系及IPARCOS-UCM）
We report a significant detection of the hot intergalactic medium in the filamentary bridge connecting the galaxy clusters Abell 399 and Abell 401. This result is enabled by a low-noise, high-resolution map of the thermal Sunyaev-Zeldovich signal from the Atacama Cosmology Telescope (ACT) and Planck satellite. The ACT data provide the $1.65'$ resolution that allows us to clearly separate the profiles of the clusters, whose centres are separated by $37'$, from the gas associated with the filament. A model that fits for only the two clusters is ruled out compared to one that includes a bridge co…
Radio halos and radio relics are diffuse synchrotron sources that extend over Mpc-scales and are found in a number of merger galaxy clusters. They are believed to form as a consequence of the energy that is dissipated by turbulence and shocks in the intra-cluster medium (ICM). However, the precise physical processes that generate these steep synchrotron spectrum sources are still poorly constrained. We present a new LOFAR observation of the double galaxy cluster Abell 1758. This system is composed of A1758N, a massive cluster hosting a known giant radio halo, and A1758S, which is a less massiv…
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 …
We present the first Murchison Widefield Array observations of the well-known cluster of galaxies Abell 3667 (A3667) between 105 and 241 MHz. A3667 is one of the best known examples of a galaxy cluster hosting a double radio relic and has been reported to contain a faint radio halo and bridge. The origins of radio halos, relics and bridges is still unclear, however galaxy cluster mergers seems to be an important factor. We clearly detect the North-West (NW) and South-East (SE) radio relics in A3667 and find an integrated flux density at 149 MHz of 28.1 +/- 1.7 and 2.4 +/- 0.1 Jy, respectively,…
We report new observations of Abell 2256 with the Karl G. Jansky Very Large Array (VLA) at frequencies between 1 and 8 GHz. These observations take advantage of the 2:1 bandwidths available for a single observation to study the spectral index, polarization and Rotation Measure as well as using the associated higher sensitivity to image total intensity features down to ~0.5" resolution. We find the Large Relic, which dominates the cluster, is made up of a complex of filaments which show correlated distributions in intensity, spectral index, and fractional polarization. The Rotation Measure vari…
We present new low-frequency ($ν= 88$-216 MHz) observations of the complex merging galaxy cluster Abell 3266. These new observations are taken with the Murchison Widefield Array (MWA) in its Phase II 'extended', long-baseline configuration, offering the highest-resolution low-frequency view of the cluster to date. We report on the detection of four steep spectrum ($α\lesssim -1$ for $S_ν\propto ν^α$) extended radio sources within the cluster. We confirm the detection of a $\sim 570$ kpc radio relic to the south of the cluster, and a possible bridge of emission connecting the relic to the clust…
We obtained SOAR telescope B and V photometry of 14 star clusters and 2 associations in the Bridge tidal structure connecting the LMC and SMC. These objects are used to study the formation and evolution of star clusters and associations under tidal stresses from the Clouds. Typical star clusters in the Bridge are not richly populated and have in general relatively large diameters (~30-35 pc), being larger than Galactic counterparts of similar age. Ages and other fundamental parameters are determined with field-star decontaminated photometry. A self-consistent approach is used to derive paramet…
We use MUSE/VLT to conduct a survey of $z\sim3$ physical quasar pairs at close separation with a fast observation strategy. Our aim is twofold: (i) explore the Ly$α$ glow around the faint-end of the quasar population; (ii) take advantage of the combined illumination of a quasar pair to unveil large-scale intergalactic structures extending between the two quasars. Here, we report the results for a quasar pair ($z=3.020,3.008$; $i=21.84,22.15$), separated by 11.6 arcsec (or 89 projected kpc). MUSE reveals filamentary Ly$α$ structures extending between the two quasars with an average surface brig…
The remnant radio galaxies in galaxy clusters are important sources of seed relativistic electron population in the intra-cluster medium (ICM). Their occurrence and spectral properties are poorly studied. In this work we present a broadband study of the radio relic in the galaxy cluster Abell 4038 using the Upgraded Giant Metrewave Radio Telescope (uGMRT). We present the uGMRT images in the bands 300 - 500 MHz and 1050 - 1450 MHz having rms noise $70\,μ$Jy beam$^{-1}$ and $30\,μ$Jy beam$^{-1}$, respectively, that are the deepest images of this field so far. A spectral analysis of the relic ove…
A New Perspective on Galactic Evolution: Studying the Outskirts of the Abell S1063 Galaxy Cluster
Università di Salerno（萨莱诺大学）；INAF – Osservatorio Astronomico di Capodimonte（意大利国家天体物理研究所卡波迪蒙特天文台）；INFN – Gruppo Collegato di Salerno - Sezione di Napoli（意大利国家核物理学院萨莱诺协作组-那不勒斯分部）；INAF – IASF Milano（意大利国家天体物理研究所米兰天文与空间物理研究所）；Dipartimento di Fisica dell’Università degli Studi di Trieste – Sezione di Astronomia（的里雅斯特大学物理系天文学分部）；INAF – Osservatorio Astronomico di Trieste（意大利国家天体物理研究所的里雅斯特天文台）；Institute of Cosmology and Gravitation, University of Portsmouth（朴茨茅斯大学宇宙学与引力研究所）
We present results from Chandra and XMM-Newton observations of Abell 98 (A98), a galaxy cluster with three major components: a relatively bright subcluster to the north (A98N), a disturbed subcluster to the south (A98S), and a fainter subcluster to the far south (A98SS). We find evidence for surface brightness and temperature asymmetries in A98N consistent with a shock-heated region to the south, which could be created by an early stage merger between A98N and A98S. Deeper observations are required to confirm this result. We also find that A98S has an asymmetric core temperature structure, lik…
The magnetic mayhem in Abell 2199: discovery of synchrotron threads and homogeneous diffuse radio lobes
Durham University（杜伦大学）；University of Minnesota（明尼苏达大学）；INAF - Instituto di Radioastronomia（意大利国家天体物理研究所射电天文研究所）；National Centre for Radio Astrophysics, Tata Institute of Fundamental Research（塔塔基础研究院国家射电天体物理学中心）
We present the results of a new Chandra study of the galaxy cluster A2626. The radio emission of the cluster shows a complex system of four symmetric arcs without known correlations with the X-ray emission. The mirror symmetry of the radio arcs toward the center and the presence of two optical cores in the central galaxy suggested that they may be created by pairs of precessing radio jets powered by dual AGNs inside the cD galaxy. However, previous observations failed to observe the second jetted AGN and the spectral trend due to radiative age along the radio arcs, thus challenging this interp…
The topology of the magnetic field in Abell 2255 out to its virial radius. Results from the LOFAR Galaxy Cluster Ultra-Deep Field
INAF - IRA（意大利国家天体物理研究所-博洛涅分院）；Leiden Observatory, Leiden University（莱顿大学莱顿天文台）；Institute for Advanced Study（普林斯顿高等研究院）；Dipartimento di Fisica e Astronomia, Università di Bologna（博洛尼亚大学物理与天文学系）；Center for Astrophysics Harvard & Smithsonian（哈佛&史密森尼天体物理中心）；Department of Astronomy, University of Wisconsin-Madison（威斯康星大学麦迪逊分校天文学系）；ASTRON, the Netherlands Institute for Radio Astronomy（荷兰射电天文研究所）；Hamburger Sternwarte, Universität Hamburg（汉堡大学汉堡天文台）；INAF - IASF Milano（意大利国家天体物理研究所-米兰天文物理研究所）
We report a large-scale ($r\approx 20^\circ$) X-ray and Sunyaev-Zeldovich (SZ)-bright diffuse enhancement toward M31, which might be a Local Hot Bridge connecting the Milky Way (MW) with M31. We subtract the Galactic emission from the all-sky O VII and O VIII emission line measurement survey, and find that the emission of these two ions is enhanced within $r\approx20^\circ$ around M31. The mean emission enhancements are $5.6\pm 1.3$ L.U., and $2.8\pm0.6$ L.U. for O VII and O VIII, respectively ($>4σ$ for both ions). We also extract the SZ signal around M31, which suggests a surface brightness …
Clusters of varying mass ratios can merge and the process significantly disturbs the cluster environments and alters their global properties. Active radio galaxies are another phenomenon that can also affect cluster environments. Radio jets can interact with the intra-cluster medium (ICM) and locally affect its properties. Abell~2384 (hereafter A2384) is a unique system that has a dense, hot X-ray filament or bridge connecting the two unequal mass clusters A2384(N) and A2384(S). The analysis of its morphology suggests that A2384 is a post-merger system where A2384(S) has already interacted wit…
Looking at the region connecting two clusters is a promising way to identify and study the Warm-Hot Intergalactic Medium. Observations show that the spectrum of the bridge between A3556 and A3558 has a stronger soft X-ray emission than the nearby region. Suzaku observations could not discriminate the origin of the extra emission. In this work we analyze a dedicated Chandra observation of the same target to identify point sources and characterize the background emission in the bridge. We find that the count number of the point sources is much higher than average field population (using CDFS~4~M…
Dwarf galaxies enable us to study the early phases of galaxy evolution and are key to many open questions about the hierarchical structure of the Universe. The Large and Small Magellanic Cloud (LMC and SMC) are the most luminous dwarf galaxy satellites of the Milky Way (MW). They are most likely gravitationally bound to each other, and their last interaction occurred about 200 Myr ago. Also, they are in an early phase of minor merging with the MW and will impact the Galactic structure in the future because of their relatively large mass. However, there are still major uncertainties regarding t…
In major galaxy mergers, the orbits of stars are violently perturbed, and gas is torqued to the centre, diluting the gas metallicity and igniting a starburst. In this paper, we study the gas dynamics in and around merging galaxies using a series of cosmological magneto-hydrodynamical (MHD) zoom-in simulations. We find that the gas bridge connecting the merging galaxies pre-coalescence is dominated by turbulent pressure, with turbulent Mach numbers peaking at values of 1.6-3.3. This implies that bridges are dominated by supersonic turbulence, and are thus ideal candidates for studying the impac…
