We present the detection of a bright 3mm continuum source in the Brightest Cluster Galaxy (BCG) in Abell 851 (z=0.411) with the NOrthern Extended Millimeter Array (NOEMA). When this detection is compared to other multi-frequency observations across 21cm-100um, including new Arcminute Microkelvin Imager 15GHz observations, we find evidence for a relatively flat, variable core source associated with the BCG. The radio power and amplitude of variability observed in this galaxy is consistent with the cores in lower redshift BCGs in X-ray-selected clusters, and the flat mm-cm spectrum is suggestive of the BCG being a low luminosity AGN archetype. The discovery of this system could provide a basis for a long-term study of the role of low luminosity radio mode 'regulatory' feedback in massive clusters.
A new radio map of the Abell 85 Brightest Cluster Galaxy (BCG) was obtained with the Karl G. Jansky Very Large Array (VLA). With a resolution of 0.02", this radio image shows two kiloparsec-scale bipolar jets emanating from the active galactic nucleus of the Abell 85 BCG. The galaxy core appears as a single entity on the new radio map. It has been assumed that the Abell 85 BCG contained a binary black hole in its core. However, Chandra X-ray data and the new high-resolution radio map show no evidence that the Abell 85 BCG harbors a binary black hole. The assumption that this galaxy contains a …
We have found that the brightest cluster galaxy (BCG) in Abell~85, Holm 15A, displays the largest core so far known. Its cusp radius, $r_γ = 4.57 \pm 0.06$ kpc ($4.26^{\prime\prime}\pm 0.06^{\prime\prime}$), is more than 18 times larger than the mean for BCGs, and $\geq1$ kpc larger than A2261-BCG, hitherto the largest-cored BCG (Postman, Lauer, Donahue, et al. 2012) Holm 15A hosts the luminous amorphous radio source 0039-095B and has the optical signature of a LINER. Scaling laws indicate that this core could host a supermassive black hole (SMBH) of mass $M_{\bullet}\thicksim (10^{9}-10^{11})…
We present an ALMA study of the ~180 brightest sources in the SCUBA-2 map of the COSMOS field from the S2COSMOS survey, as a pilot study for AS2COSMOS - a full survey of the ~1,000 sources in this field. In this pilot we have obtained 870-um continuum maps of an essentially complete sample of the brightest 182 sub-millimetre sources (S_850um=6.2mJy) in COSMOS. Our ALMA maps detect 260 sub-millimetre galaxies (SMGs) spanning a range in flux density of S_870um=0.7-19.2mJy. We detect more than one SMG counterpart in 34+/-2 per cent of sub-millimetre sources, increasing to 53+/-8 per cent for SCUB…
As a case study to understand the coevolution of Brightest Cluster Galaxies (BCGs) and their host clusters, we investigate the BCGs in dynamically young and old clusters, Abell 1139 (A1139) and Abell 2589 (A2589). We analyze the pixel color-magnitude diagrams (pCMDs) using deep g- and r-band images, obtained from the Canada-France-Hawaii Telescope observations. After masking foreground/background objects and smoothing pixels in consideration of the observational seeing size, detailed pCMD features are compared between the two BCGs. (1) While the overall shapes of the pCMDs are similar to those…
We present VLA images and HST/STIS spectra of sources within the center of the brightest cluster galaxy (BCG) in Abell 2261. These observations were obtained to test the hypothesis that its extremely large, flat core reflects the ejection of its supermassive black hole. Spectra of three of the four most luminous "knots" embedded in the core were taken to test whether one may represent stars bound to a displaced massive black hole. The three knots have radial velocity offsets dV < ~150 km/s from the BCG. Knots 2 and 3 show kinematics, colors, and stellar masses consistent with infalling low-mas…
Abell~1142 is a low-mass galaxy cluster at low redshift containing two comparable Brightest Cluster Galaxies (BCG) resembling a scaled-down version of the Coma Cluster. Our Chandra analysis reveals an X-ray emission peak, roughly 100 kpc away from either BCG, which we identify as the cluster center. The emission center manifests itself as a second beta-model surface brightness component distinct from that of the cluster on larger scales. The center is also substantially cooler and more metal rich than the surrounding intracluster medium (ICM), which makes Abell 1142 appear to be a cool core cl…
We use Chandra X-ray observations to look for evidence of a recoiling black hole from the brightest cluster galaxy in Abell 2261 (A2261-BCG). A2261-BCG is a strong candidate for a recoiling black hole because of its large, flat stellar core, revealed by Hubble Space Telescope imaging observations. We took 100-ksec observations with Chandra and combined it with 35 ksec of archival observations to look for low-level accretion onto a black hole of expected mass $M\sim10^{10}\ M_{\scriptscriptstyle \odot}$ that could possibly be located in one of four off-center stellar knots near the galaxy's cen…
Based on HST and MUSE data, we probe the stellar and gas properties (i.e. kinematics, stellar mass, star formation rate) of the radio-loud brightest cluster galaxy (BCG) located at the centre of the X-ray luminous cool core cluster Abell 2667 (z = 0.2343). The bi-dimensional modelling of the BCG surface brightness profile reveals the presence of a complex system of substructures extending all around the galaxy. Clumps of different size and shape plunged into a more diffuse component constitute these substructures, whose intense 'blue' optical colour hints to the presence of a young stellar pop…
We present high-resolution (synthesised beam size 0."088x0."083 or 25x23 pc$^2$) Atacama Large Millimetre/submillimetre Array (ALMA) $^{12}$CO(2-1) line and 236 GHz continuum observations, as well as 5 GHz enhanced Multi-Element Radio Linked Interferometer Network (e-MERLIN) continuum observations, of NGC 0708; the brightest galaxy in the low-mass galaxy cluster Abell 262. The line observations reveal a turbulent, rotating disc of molecular gas in the core of the galaxy, and a high-velocity, blue-shifted feature ~0."4 (~113 pc) from its centre. The sub-millimetre continuum emission peaks at th…
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 new deep photometry of the rich globular cluster (GC) systems around the Brightest Cluster Galaxies UGC 9799 (Abell 2052) and UGC 10143 (Abell 2147), obtained with the HST ACS and WFC3 cameras. For comparison, we also present new reductions of similar HST/ACS data for the Coma supergiants NGC 4874 and 4889. All four of these galaxies have huge cluster populations (to the radial limits of our data, comprising from 12000 to 23000 clusters per galaxy). The metallicity distribution functions (MDFs) of the GCs can still be matched by a bimodal-Gaussian form where the metal-rich and metal…
We present the first results from an integral field (IFU) spectroscopic survey of a 75kpc region around three Brightest Cluster Galaxies (BCGs), combining over 100 IFU fibres to study the intracluster light (ICL). We fit population synthesis models to estimate age and metallicity. For Abell 85 and Abell 2457, the ICL is best-fit with a fraction of old, metal-rich stars like in the BCG, but requires 30-50% young and metal-poor stars, a component not found in the BCGs. This is consistent with the ICL having been formed by a combination of interactions with less massive, younger, more metal-poor …
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 used the PdBI to map a sample of 15 SMGs in the COSMOS field at the wavelength of 1.3 mm. The target SMGs were originally discovered in the JCMT/AzTEC 1.1 mm continuum survey at S/N=4-4.5. This paper presents, for the first time, interferometric millimetre-wavelength observations of these sources. The angular resolution of our observations, 1.8", allowed us to accurately determine the positions of the target SMGs. Using a detection threshold of S/N>4.5 regardless of multiwavelength counterpart association, and 4<S/N<=4.5 if a multiwavelength counterpart within 1.5" is also present, the tota…
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…
A fraction of brightest cluster galaxies (BCGs) shows bright emission in the UV and the blue part of the optical spectrum, which has been interpreted as evidence of recent star formation. Most of these results are based on the analysis of broadband photometric data. Here, we study the optical spectra of a sample of 19 BCGs hosted by X-ray luminous galaxy clusters at 0.15 < z < 0.3, a subset from the Canadian Cluster Comparison Project (CCCP) sample. We identify plausible star formation histories of the galaxies by fitting Simple Stellar Populations (SSPs) as well as composite populations, cons…
Measurements of the intracluster light (ICL) are still prone to methodological ambiguities and there are multiple techniques in the literature for that purpose, mostly based on the binding energy, the local density distribution, or the surface brightness. A common issue with these methods is the a priori assumption of a number of hypotheses on either the ICL morphology, its surface brightness level or some properties of the brightest cluster galaxy (BCG). The discrepancy on the results is high, and numerical simulations just bound the ICL fraction in present-day galaxy clusters to the range 10…
Here we analyze radio, optical, and X-ray data for a peculiar cluster Abell 578. This cluster is not fully relaxed and consists of two merging sub-systems. The brightest cluster galaxy, CGPG 0719.8+6704, is a pair of interacting ellipticals with projected separation $\sim$10 kpc, the brighter of which hosts the radio source 4C +67.13. The Fanaroff-Riley type-II radio morphology of 4C +67.13 is unusual for central radio galaxies in local Abell clusters. Our new optical spectroscopy revealed that both nuclei of the CGPG 0719.8+6704 pair are active, albeit at low accretion rates corresponding to …
Abell 1201 is a massive galaxy cluster at z=0.169 with a brightest cluster galaxy (BCG) that acts as a gravitational lens to a background source at z=0.451. The lensing configuration is unusual, with a single bright arc formed at small radius $\sim$2 arcsec), where stars and dark matter are both expected to contribute substantially to the total lensing mass. Here, we present deep spectroscopic observations of the Abell 1201 BCG with MUSE, which reveal emission lines from a faint counter-image, opposite to the main arc, at a radius of 0.6 arcsec. We explore models in which the lensing mass is d…
Holm 15A, the brightest cluster galaxy (BCG) of the galaxy cluster Abell 85, has an ultra-diffuse central region, 2 mag fainter than the faintest depleted core of any early-type galaxy (ETG) that has been dynamically modelled in detail. We use orbit-based, axisymmetric Schwarzschild models to analyse the stellar kinematics of Holm 15A from new high-resolution, wide-field spectral observations obtained with MUSE at the VLT. We find a supermassive black hole (SMBH) with a mass of (4.0 +- 0.80) x 10^10 solar masses at the center of Holm 15A. This is the most massive black hole with a direct dynam…
Brightest Cluster Galaxies (BCGs) in massive dark matter halos are shaped by complex merging processes. We present a detailed stellar population analysis in the central region of Abell 3827 at $z\sim0.1$, including five-nucleus galaxies involved in a BCG assembly. Based on deep spectroscopy from Multi Unit Spectroscopic Explorer (MUSE), we fit the optical spectra of 13 early-type galaxies (ETGs) in the central 70 kpc of the cluster. The stellar populations in the central $R=1$ kpc of these ETGs are old (6-10 Gyr). Their [Fe/H] increases with $σ_{\star}$ and stellar mass. More importantly, [$α$…
Jellyfish are cluster galaxies that experience strong ram-pressure effects that strip their gas. Their H$α$ images reveal ionized gas tails up to 100 kpc, which could be hosting ongoing star formation. Here we report the ultraviolet (UV) imaging observation of the jellyfish galaxy JO201 obtained at a spatial resolution $\sim$ 1.3 kpc. The intense burst of star formation happening in the tentacles is the focus of the present study. JO201 is the "UV-brightest cluster galaxy" in Abell 85 ($z \sim$ 0.056) with knots and streams of star formation in the ultraviolet. We identify star forming knots b…
We present XSHOOTER observations with previous ALMA, MUSE and $HST$ observations to study the nature of radio-jet triggered star formation and the interaction of radio jets with the interstellar medium in the brightest cluster galaxy (BCG) in the Abell 1795 cluster. Using $HST$ UV data we determined an ongoing star formation rate of 9.3 M$_\odot$ yr$^{-1}$. The star formation follows the global Kennicutt-Schmidt law, however, it has a low efficiency compared to circumnuclear starbursts in nearby galaxies with an average depletion time of $\sim$1 Gyr. The star formation and molecular gas are of…
We study the impact of local environment on the transformation of spiral galaxies in three nearby ($z < 0.08$) Abell clusters: A85/A496/A2670. These systems were observed in HI with the Very Large Array, covering a volume extending beyond the virial radius and detecting 10, 58, 38 galaxies, respectively. High fractions (0.40--0.86) of bright spirals [log$(M_{*}/M_{\odot})=9-10$] are not detected in HI. We provide further evidence of environmental effects consisting in significant fractions (0.10--0.33) of abnormal objects and a number of red (passive) spirals, suggesting an ongoing process of …
We present the circumnuclear multi-phase gas properties of the brightest cluster galaxy (BCG) in the center of Abell 1644-South. A1644-S is the main cluster in a merging system, which is well known for X-ray hot gas sloshing in its core. The sharply peaked X-ray profile of A1644-S implies the presence of a strongly cooling gas core. In this study, we analyze ALMA CO (1-0) data, JVLA HI data, and KaVA 22 GHz data for the central region of A1644-S to probe the potential origin of the cool gas and its role in (re)powering the central active galactic nucleus (AGN). We find CO clumps distributed in…
X-ray and Radio Analysis of Abell 1644: Constraints on Cluster Dynamics
University of Kashmir（克什米尔大学）；National Centre for Radio Astrophysics, Tata Institute of Fundamental Research（塔塔基础研究所国家射电天体物理中心）；Univ. Lille, Univ. Artois, Univ. Littoral Côte d’Opale（里尔大学、阿图瓦大学、海岸-opal大学）
We report the detection of CO(2-1) emission coincident with the brightest cluster galaxy (BCG) of the high-redshift galaxy cluster SpARCS1049+56, with the Redshift Search Receiver (RSR) on the Large Millimetre Telescope (LMT). We confirm a spectroscopic redshift for the gas of z = 1.7091+/-0.0004, which is consistent with the systemic redshift of the cluster galaxies of z = 1.709. The line is well-fit by a single component Gaussian with a RSR resolution-corrected FWHM of 569+/-63 km/s. We see no evidence for multiple velocity components in the gas, as might be expected from the multiple image …
The study of low surface brightness light in large, deep imaging surveys is still uncharted territory as automated data reduction pipelines over-subtract or eliminate this light. Using archival data of the Abell 85 cluster of galaxies taken with Hyper Suprime-Cam on the Subaru Telescope, we show that using careful data processing can unveil the diffuse light within the cluster, the intracluster light. We reach surface brightness limits of $μ_{g}^{limit}$(3$σ$, 10"x10") = 30.9 mag/arcsec$^2$, and $μ_{i}^{limit}$(3$σ$, 10"x10") = 29.7 mag/arcsec$^2$. We measured the radial surface brightness pro…
Abell 2146 consists of two galaxy clusters that have recently collided close to the plane of the sky, and it is unique in showing two large shocks on $\textit{Chandra X-ray Observatory}$ images. With an early stage merger, shortly after first core passage, one would expect the cluster galaxies and the dark matter to be leading the X-ray emitting plasma. In this regard, the cluster Abell 2146-A is very unusual in that the X-ray cool core appears to lead, rather than lag, the Brightest Cluster Galaxy (BCG) in their trajectories. Here we present a strong lensing analysis of multiple image systems…
We analyse the stellar kinematics of the z=0.169 brightest cluster galaxy (BCG) in Abell 1201, using integral field observations with VLT/MUSE. This galaxy has a gravitationally-lensed arc located at unusually small radius ($\sim$5 kpc), allowing us to constrain the mass distribution using lensing and stellar dynamical information over the same radial range. We measure a velocity dispersion profile which is nearly flat at $σ$ $\approx$ 285 km/s in the inner $\sim$5 kpc, and then rises steadily to $σ$ $\approx$ 360 km/s at $\sim$30 kpc. We analyse the kinematics using axisymmetric Jeans models,…
Context. X-shaped radio galaxies (XRGs) exhibit a pair of bright primary lobes and a pair of weak secondary lobes (wings), which are oriented with an angle that gives the structure a cross-like shape. Though several theoretical models have been proposed to explain their origin, there is currently not a general consensus on a formation scenario. Aims. We analysed new multifrequency Karl G. Jansky Very Large Array (JVLA) radio data at 1.5, 5.5, 6, and 9 GHz of the candidate XRG in Abell 3670 (A3670) in order to characterise and classify it for the first time and to investigate its origin. Method…
We report the discovery of an extremely large (R_b ~ 2"77 ~ 4.2 kpc) core in the brightest cluster galaxy, IC 1101, of the rich galaxy cluster Abell 2029. Luminous core-Sérsic galaxies contain depleted cores---with sizes (R_b) typically 20 - 500 pc---that are thought to be formed by coalescing black hole binaries. We fit a (double nucleus) + (spheroid) + (intermediate-scale component) + (stellar halo) model to the HST surface brightness profile of IC 1101, finding the largest core size measured in any galaxy to date. This core is an order of magnitude larger than those typically measured for c…
[abridged] Here we present the analysis of multifrequency data gathered for the FRII radio galaxy PKS B1358-113, hosted in the brightest cluster galaxy of Abell 1836. The galaxy harbors one of the most massive black holes known to date and our analysis of the optical data reveals that this black hole is only weakly active. Based on new Chandra and XMM-Newton X-ray observations and archival radio data we derive the preferred range for the jet kinetic luminosity $\sim (0.5-3) \times 10^{45}$ erg s$^{-1}$. This is above the values implied by various scaling relations proposed for radio sources in…
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…
Extended, steep-spectrum radio synchrotron sources are pre-dominantly found in massive galaxy clusters as opposed to groups. LOFAR Two-Metre Sky Survey images have revealed a diffuse, ultra-steep spectrum radio source in the low-mass cluster Abell 1931. The source has a fairly irregular morphology with a largest linear size of about 550 kpc. The source is only seen in LOFAR observations at 143 MHz and GMRT observations at 325 MHz. The spectral index of the total source between 143 MHz and 325 MHz is $α_{143}^{325} = -2.86 \pm 0.36$. The source remains invisible in Very Large Array (1-2 GHz) ob…
We report on a spectral study at radio frequencies of the giant radio halo in A2142 (z=0.0909), which we performed to explore its nature and origin. A2142 is not a major merger and the presence of a giant radio halo is somewhat surprising. We performed deep radio observations with the GMRT at 608 MHz, 322 MHz, and 234 MHz and with the VLA in the 1-2 GHz band. We obtained high-quality images at all frequencies in a wide range of resolutions. The radio halo is well detected at all frequencies and extends out to the most distant cold front in A2142. We studied the spectral index in two regions: t…
We present a multiwavelength study of the massive galaxy cluster Abell 1763 at redshift z = 0.231. Image analysis of a 19.6 ks Chandra archival observation reveals a cluster-wide spiral of enhanced surface brightness in the intracluster medium (ICM). While such spirals are understood to form in clusters with sloshing strong cool cores (SCCs), the gas comprising the spiral's apex is of intermediate entropy ($\sim$ 110 keV cm$^{2}$) and cooling time ($\sim$ 6.8 Gyr), indicating core disruption is occurring throughout the spiral formation process. Two subclusters dominated by the second- and thir…
The radio source in Abell 980: A Detached-Double-Double Radio Galaxy?
UM-DAE Centre for Excellence in Basic Sciences, University of Mumbai（孟买大学基础科学卓越中心）；Department of Physics, Savitribai Phule Pune University（萨维特里巴伊·普勒浦那大学物理系）；INAF-Padova Astronomical Observatory（帕多瓦天文台）
We have observed 433 z<=0.08 brightest cluster galaxies (BCGs) in a full-sky survey of Abell clusters. The BCG Hubble diagram is consistent to within 2% of a Omega_m=0.3, Lambda=0.7 Hubble relation. The L_m-alpha relation for BCGs, which uses alpha, the log-slope of the BCG photometric curve of growth, to predict metric luminosity, L_m, has 0.27 mag residuals. We measure central stellar velocity dispersions, sigma, of the BCGs, finding the Faber-Jackson relation to flatten as the metric aperture grows to include an increasing fraction of the total BCG luminosity. A 3-parameter "metric plane" r…
We present multiwavelength photometric catalogues (HST, Spitzer and Hawk-I K band) for the first two of the Frontier Fields, Abell2744 and MACSJ0416 (plus their parallel fields). To detect faint sources even in the central regions of the clusters, we develop a robust and repeatable procedure that uses the public codes Galapagos and Galfit to model and remove most of the light contribution from both the brightest cluster members as well as the ICL. We perform the detection on the HST H160 processed image to obtain a pure H-selected sample. We also add a sample of sources which are undetected in…
We present a weak-lensing and dynamical study of the complex cluster Abell 1758 (A1758, z = 0.278) supported by hydrodynamical simulations. This cluster is composed of two main structures, called A1758N and A1758S. The Northern structure is composed of A1758NW & A1758NE, with lensing determined masses of 7.90_{-1.55}^{+1.89} X 10^{14} M_\odot and 5.49_{-1.33}^{+1.67} X 10^{14} M_\odot, respectively. They show a remarkable feature: while in A1758NW there is a spatial agreement among weak lensing mass distribution, intracluster medium and its brightest cluster galaxy (BCG) in A1758NE the X-ray p…
The galaxy cluster Abell 3733 (A3733) is a very suitable candidate in addressing dynamical processes throughout galaxy cluster mergers. This study shows structural analysis results of A3733 (z = 0.038) based on X-ray and optical data. According to X-ray luminosity map, A3733 hosts two sub-structures separated in the sky by $\sim$ 0.25 Mpc, and the two distinct clumps are located in the East (A3733E) and the West (A3733W) directions. Both sub-structures are centred on two different brightest cluster galaxies (BCGs), and the X-ray and optical centroids of both BCGs substantially coincide with ea…
Abell 407 (A407) is a unique galaxy cluster hosting a central compact group of nine galaxies (named as 'Zwicky's Nonet'; G1 - G9 in this work) within a 30 kpc radius region. The cluster core also hosts a luminous radio active galactic nucleus (AGN), 4C 35.06 with helically twisted jets extending over 200 kpc. With a 44 ks Chandra observation of A407, we characterize the X-ray properties of its intracluster medium (ICM) and central galaxies. The mean X-ray temperature of A407 is 2.7 keV and the $M_{200}$ is $1.9 \times 10^{14} {M_{\odot}}$. We suggest that A407 has a weak cool core at $r < 60$ …
