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In this work, we investigate the quasinormal modes for a massive scalar field with a nonminimal coupling with gravity in the spacetime of a loop quantum black hole, known as the Self-Dual Black Hole. In this way, we have calculated the characteristic frequencies using the 3rd order WKB approach, where we can verify a strong dependence with the mass of scalar field, the parameter of nonminimal coupling with gravity, and parameters of the Loop Quantum Gravity. From our results, we can check that the Self-Dual Black Hole is stable under the scalar perturbations when assuming small values for the parameters. Also, such results tell us that the quasinormal modes assume different values for the cases where the mass of field is null and the nonminimal coupling assumes $\xi=0$ and $\xi=1/6$, i.e., a possible breaking of the conformal invariance can be seen in the context of loop quantum black holes., Comment: 15 pages, 2 tables and 8 figures. arXiv admin note: text overlap with arXiv:2005.02208

We investigate the dust-obscured star formation properties of the massive, X-ray selected galaxy cluster MACS J1931.8-2634 at $z$=0.352. Using far-infrared (FIR) imaging in the range 100-500$\mu$m obtained with the \textit{Herschel} telescope, we extract 31 sources (2$\sigma$) within $r\sim$1 Mpc from the brightest cluster galaxy (BCG). Among these sources we identify six cluster members for which we perform an analysis of their spectral energy distributions (SEDs). We measure total infrared luminosity (L$_{IR}$), star formation rate (SFR) and dust temperature. The BCG, with L$_{IR}$=1.4$\times$10$^{12}$L$_\odot$ is an Ultra Luminous Infrared Galaxy and hosts a type II AGN. We decompose its FIR SED into AGN and starburst components and find equal contributions from AGN and starburst. We also recompute the SFR of the BCG finding SFR=150$\pm$15 M$_\odot$yr$^{-1}$. We search for an isobaric cooling flow in the cool core using {\sl Chandra} X-ray data, and find no evidence for gas colder than 1.8 keV in the inner 30 kpc, for an upper limit to the istantaneous mass-deposition rate of 58 M$_\odot$yr$^{-1}$ at 95 % c.l. This value is $3\times$ lower than the SFR in the BCG, suggesting that the on-going SF episode lasts longer than the ICM cooling events., Comment: 6 pages, 3 figures, MNRAS accepted

(Abridged) We present a spectral analysis of a deep (220 ks) XMM-Newton observation of the Phoenix cluster (SPT-CL J2344-4243), which we also combine with Chandra archival ACIS-I data. We extract CCD and RGS X-ray spectra from the core region to search for the signature of cold gas, and constrain the mass deposition rate in the cooling flow which is thought to be responsible of the massive star formation episode observed in the BCG. We find an average mass deposition rate of $\dot M = 620 (-190 +200)_{stat} (-50 +150)_{syst} M_\odot$/yr in the temperature range 0.3-3.0 keV from MOS data. A temperature-resolved analysis shows that a significant amount of gas is deposited only above 1.8 keV, while upper limits of the order of hundreds of $M_\odot$/yr can be put in the 0.3-1.8 keV temperature range. From pn data we obtain $\dot M = 210 (-80 +85)_{stat} ( -35 +60)_{syst} M_\odot$/yr, and the upper limits from the temperature-resolved analysis are typically a factor of 3 lower than MOS data. In the RGS spectrum, no line emission from ionization states below Fe XXIII is seen above $12 \AA$, and the amount of gas cooling below $\sim 3$ keV has a best-fit value $\dot M = 122_{-122}^{+343}$ $M_{\odot}$/yr. In addition, our analysis of the FIR SED of the BCG based on Herschel data provides $SFR = (530 \pm 50) M_\odot$/yr, significantly lower than previous estimates by a factor 1.5. Current data are able to firmly identify substantial amount of cooling gas only above 1.8 keV in the core of the Phoenix cluster. While MOS data analysis is consistent with values as high as $\dot M \sim 1000$ within $1 \sigma$, pn data provide $\dot M < 500 M_\odot$ yr$^{-1}$ at $3\sigma$ c.l. at temperature below 1.8 keV. At present, this discrepancy cannot be explained on the basis of known calibration uncertainties or other sources of statistical noise., Comment: A&A in press, typos corrected, revised text according to published version

We report the analysis of the Chandra observation of XDCP J0044.0-2033, a massive, distant (z=1.579) galaxy cluster discovered in the XDCP survey. The total exposure time of 380 ks with Chandra ACIS-S provides the deepest X-ray observation currently achieved on a massive, high redshift cluster. Extended emission from the Intra Cluster Medium (ICM) is detected at a very high significance level (S/N~20) on a circular region with a 44" radius, corresponding to $R_{ext}=375$ kpc at the cluster redshift. We perform an X-ray spectral fit of the ICM emission modeling the spectrum with a single-temperature thermal mekal model. Our analysis provides a global temperature $kT=6.7^{+1.3}_{-0.9}$ keV, and a iron abundance $Z_{Fe} = 0.41_{-0.26}^{+0.29}Z_{Fe_\odot}$ (error bars correspond to 1 $\sigma$). We fit the background-subtracted surface brightness profile with a single $\beta$-model out to 44", finding a rather flat profile with no hints of a cool core. We derive the deprojected electron density profile and compute the ICM mass within the extraction radius $R_{ext}=375$ kpc to be $M_{ICM}(r

We present APEX LABOCA 870 micron observations of the field around the high-redshift radio galaxy MRC1138-262 at z=2.16. We detect 16 submillimeter galaxies in this ~140 square arcmin bolometer map with flux densities in the range 3-11 mJy. The raw number counts indicate a density of submillimeter galaxies (SMGs) that is up to four times that of blank field surveys. Based on an exquisite multiwavelength database, including VLA 1.4 GHz radio and infrared observations, we investigate whether these sources are members of the protocluster structure at z=2.2. Using Herschel PACS+SPIRE and Spitzer MIPS photometry, we derive reliable far-infrared photometric redshifts for all sources. Follow-up VLT ISAAC and SINFONI near-infrared spectra confirm that four of these SMGs have redshifts of z=2.2. We also present evidence that another SMG in this field, detected earlier at 850 micron, has a counterpart that exhibits Halpha and CO(1-0) emission at z=2.15. Including the radio galaxy and two SMGs with far-IR photometric redshifts at z=2.2, we conclude that at least eight submm sources are part of the protocluster at z=2.16 associated with the radio galaxy MRC1138-262. We measure a star formation rate density SFRD ~1500 Msun yr^-1 Mpc^-3, four magnitudes higher than the global SFRD of blank fields at this redshift. Strikingly, these eight sources are concentrated within a region of 2 Mpc (the typical size of clusters in the local universe) and are distributed within the filaments traced by the Halpha emitters at z=2.2. This concentration of massive, dusty starbursts is not centered on the submillimeter-bright radio galaxy which could support the infalling of these sources into the cluster center. Approximately half (6/11) of the SMGs that are covered by the Halpha imaging data are associated with Halpha emitters, demonstrating the potential of tracing SMG counterparts with this population (abridged)., Comment: Accepted by A&A. ESO Press Release on 15 October 2014. 19 pages, 9 figures and 4 tables

We investigate various galaxy population properties of the massive X-ray luminous galaxy cluster XDCP J0044.0-2033 at z=1.58, which constitutes the most extreme matter density peak at this redshift currently known. We analyze deep VLT/HAWK-I NIR data in the J- and Ks-bands, complemented by Subaru imaging in i and V, Spitzer observations at 4.5 micron, and new spectroscopic observations with VLT/FORS2. We detect a cluster-associated excess population of about 90 galaxies, which follows a centrally peaked, compact NFW galaxy surface density profile with a concentration of c200~10. Based on the Spitzer 4.5 micron imaging data, we measure a stellar mass fraction of fstar,500=(3.3+-1.4)% consistent with local values. The total J- and Ks-band galaxy luminosity functions of the core region yield characteristic magnitudes J* and Ks* consistent with expectations from simple z_f=3 burst models. However, a detailed look at the morphologies and color distributions of the spectroscopically confirmed members reveals that the most massive galaxies are undergoing a very active mass assembly epoch through merging processes. Consequently, the bright end of the cluster red-sequence is not in place, while at intermediate magnitudes [Ks*,Ks*+1.6] a red-locus population is present, which is then sharply truncated at magnitudes fainter than Ks*+1.6. The dominant cluster core population comprises post-quenched galaxies transitioning towards the red-sequence at intermediate magnitudes, while additionally a significant blue cloud population of faint star-forming galaxies is present even in the densest central regions. Our observations lend support to the scenario in which the dominant effect of the dense z~1.6 cluster environment is an accelerated mass assembly timescale through merging activity that is responsible for driving core galaxies across the mass quenching threshold of log(Mstar/Msun)~10.4., Comment: 23 pages, 19 color figures, accepted for publication in A&A, v2 matches journal version

We present a comprehensive study of star-forming (SF) galaxies in the HST Frontier Field recent cluster merger A2744 (z=0.308). Wide-field, ultraviolet-infrared (UV-IR) imaging enables a direct constraint of the total star formation rate (SFR) for 53 cluster galaxies, with SFR{UV+IR}=343+/-10 Msun/yr. Within the central 4 arcmin (1.1 Mpc) radius, the integrated SFR is complete, yielding a total SFR{UV+IR}=201+/-9 Msun/yr. Focussing on obscured star formation, this core region exhibits a total SFR{IR}=138+/-8 Msun/yr, a mass-normalised SFR{IR} of Sigma{SFR}=11.2+/-0.7 Msun/yr per 10^14 Msun and a fraction of IR-detected SF galaxies f{SF}=0.080(+0.010,-0.037). Overall, the cluster population at z~0.3 exhibits significant intrinsic scatter in IR properties (total SFR{IR}, Tdust distribution) apparently unrelated to the dynamical state: A2744 is noticeably different to the merging Bullet cluster, but similar to several relaxed clusters. However, in A2744 we identify a trail of SF sources including jellyfish galaxies with substantial unobscured SF due to extreme stripping (SFR{UV}/SFR{IR} up to 3.3). The orientation of the trail, and of material stripped from constituent galaxies, indicates that the passing shock front of the cluster merger was the trigger. Constraints on star formation from both IR and UV are crucial for understanding galaxy evolution within the densest environments., Comment: Accepted by MNRAS. 12 pages, 7 figures (high resolution versions of Figs. 1 & 2 are available in the published PDF)

We report the serendipitous detection of a significant overdensity of Herschel-SPIRE 250 micron sources in the vicinity of MRC1138-26. We use an adaptive kernel density estimate to quantify the significance, including a comparison with other fields. The overdensity has a size of ~3.5-4' and stands out at ~5sigma with respect to the background estimate. No features with similar significance were found in four extragalactic control fields: GOODS-North, Lockman, COSMOS and UDS. The chance of having a similar overdensity in a field with the same number but randomly distributed sources is less than 2%. The clump is also visible as a low surface brightness feature in the Planck 857 GHz map. We detect 76 sources at 250 micron (with a signal-to-noise ratio greater than 3), in a region of 4' radius; 43 of those are above a flux density limit of 20 mJy. This is a factor of 3.6 in excess over the average in the four control fields, considering only the sources above 20 mJy. We also find an excess in the number counts of sources with 250 micron flux densities between 30 and 40 mJy, compared to deep extragalactic blank-field number counts. Assuming a fixed dust temperature (30 K) and emissivity (beta=1.5) a crude, blackbody-derived redshift distribution, zBB, of the detected sources is significantly different from the distributions in the control fields and exhibits a significant peak at zBB ~ 1.5, although the actual peak redshift is highly degenerate with the temperature. We tentatively suggest, based on zBB and the similar S250/S350 colours of the sources within the peak, that a significant fraction of the sources in the clump may be at a similar redshift. Since the overdensity lies ~7' south of the z=2.16 Spiderweb protocluster MRC1138-26, an intriguing possibility (that is presently unverifiable given the data in hand) is that it lies within the same large-scale structure.(abridged), Comment: 10 pages, 8 figures, accepted for publication in MNRAS

We performed a thorough analysis of the star formation activity in the young massive galaxy cluster RXJ1257+4738 at z=0.866, with emphasis on the relationship between the local environment of the cluster galaxies and their star formation activity. We present an optical and IR study that benefited from the large amount of data available for this cluster, including new OSIRIS/GTC and Herschel imaging observations. Using a optical-to-NIR multi-wavelength catalogue, we measured photometric redshifts through a chi2 SED-fitting procedure. We implemented a reliable and carefully chosen cluster membership selection criterion including Monte Carlo simulations and derived a sample of 292 reliable cluster member galaxies for which we measured the following properties: optical colours, stellar masses, ages, ultraviolet luminosities and local densities. Using the MIPS 24um and Herschel data, we measured total IR luminosities and SFR. Of the sample of 292 cluster galaxies, 38 show FIR emission with an SFR between 0.5 and 45 Msun/yr. The spatial distribution of the FIR emitters within the cluster density map and the filament-like overdensities observed suggest that RXJ1257 is not virialised, but is in the process of assembly. The average star formation as a function of the cluster environment parametrised by the local density of galaxies does not show any clear trend. However, the fraction of SF galaxies unveils that the cluster intermediate-density regions is preferred for the SF activity to enhance, since we observe a significant increase of the FIR-emitter fraction in this environment. Focusing on the optically red SF galaxies, we can support the interpretation of this population as dusty red galaxies, since we observe an appreciable difference in their extinction compared with the blue population., Comment: 16 pages, 14 figures, accepted for publication in A&A

Star-formation in the galaxy populations of local massive clusters is reduced with respect to field galaxies, and tends to be suppressed in the core region. Indications of a reversal of the star-formation--density relation have been observed in a few z >1.4 clusters. Using deep imaging from 100-500um from PACS and SPIRE onboard Herschel, we investigate the infrared properties of spectroscopic and photo-z cluster members, and of Halpha emitters in XMMU J2235.3-2557, one of the most massive, distant, X-ray selected clusters known. Our analysis is based mostly on fitting of the galaxies spectral energy distribution in the rest-frame 8-1000um. We measure total IR luminosity, deriving star formation rates (SFRs) ranging from 89-463 Msun/yr for 13 galaxies individually detected by Herschel, all located beyond the core region (r >250 kpc). We perform a stacking analysis of nine star-forming members not detected by PACS, yielding a detection with SFR=48 Msun/yr. Using a color criterion based on a star-forming galaxy SED at the cluster redshift we select 41 PACS sources as candidate star-forming cluster members. We characterize a population of highly obscured SF galaxies in the outskirts of XMMU J2235.3-2557. We do not find evidence for a reversal of the SF-density relation in this massive, distant cluster., Comment: 14 pages, accepted for publication in MNRAS

(Abridged) We report the discovery of CXO J1415.2+3610, a distant (z~1.5) galaxy cluster serendipitously detected in a deep, high-resolution Chandra observation targeted to study the cluster WARP J1415.1+3612 at z=1.03. This is the highest-z cluster discovered with Chandra so far. Moreover, the total exposure time of 280 ks with ACIS-S provides the deepest X-ray observation currently achieved on a cluster at z>1.5. We perform an X-ray spectral fit of the extended emission of the intracluster medium (ICM) with XSPEC, and we detect at a 99.5% confidence level the rest frame 6.7-6.9 keV Iron K_\alpha line complex, from which we obtain z_X=1.46\pm0.025. The analysis of the z-3.6\mu m color-magnitude diagram shows a well defined sequence of red galaxies within 1' from the cluster X-ray emission peak with a color range [5 < z-3.6 \mu m < 6]. The photometric redshift obtained by spectral energy distribution (SED) fitting is z_phot=1.47\pm 0.25. After fixing the redshift to z=1.46, we perform the final spectral analysis and measure the average gas temperature with a 20% error, kT=5.8^{+1.2}_{-1.0} keV, and the Fe abundance Z_Fe = 1.3_{-0.5}^{+0.8}Z_\odot. We fit the background subtracted surface brightness with a single beta--model out to 35" and derive the deprojected electron density profile. The ICM mass is 1.09_{-0.2}^{+0.3}\times 10^{13} M_\odot within 300 kpc. The total mass is M_{2500}= 8.6_{-1.7}^{+2.1} \times 10 ^{13} M_\odot for R_{2500}=(220\pm 55) kpc. Extrapolating the profile at larger radii we find M_{500}= 2.1_{-0.5}^{+0.7} \times 10 ^{14} M_\odot for R_{500} = 510_{-50}^{+55}$ kpc. This analysis establishes CXOJ1415.2+3610 as one of the best characterized distant galaxy clusters based on X-ray data alone., Comment: 12 pages, 9 figures, A\&A in press, minor modifications in the text

We present a detailed study of the infrared spectral energy distribution of the high-redshift radio galaxy MRC 1138-26 at z = 2.156, also known as the Spiderweb Galaxy. By combining photometry from Spitzer, Herschel and LABOCA we fit the rest-frame 5-300 um emission using a two component, starburst and active galactic nucleus (AGN), model. The total infrared (8 - 1000 um) luminosity of this galaxy is (1.97+/-0.28)x10^13 Lsun with (1.17+/-0.27) and (0.79+/-0.09)x10^13 Lsun due to the AGN and starburst components respectively. The high derived AGN accretion rate of \sim20% Eddington, and the measured star formation rate (SFR) of 1390pm150 Msun/yr, suggest that this massive system is in a special phase of rapid central black hole and host galaxy growth, likely caused by a gas rich merger in a dense environment. The accretion rate is sufficient to power both the jets and the previously observed large outflow. The high SFR and strong outflow suggest this galaxy could potentially exhaust its fuel for stellar growth in a few tens of Myr, although the likely merger of the radio galaxy with nearby satellites suggest bursts of star formation may recur again on time scales of several hundreds of Myr. The age of the radio lobes implies the jet started after the current burst of star formation, and therefore we are possibly witnessing the transition from a merger-induced starburst phase to a radio-loud AGN phase. We also note tentative evidence for [CII]158um emission. This paper marks the first results from the Herschel Galaxy Evolution Project (Project HeRGE), a systematic study of the evolutionary state of 71 high redshift, 1 < z < 5.2, radio galaxies., Comment: 11 pages, 2 figures, accepted for publication in ApJ

The XMM-Newton Distant Cluster Project is a serendipitous survey for clusters of galaxies at redshifts z>=0.8 based on deep archival XMM-Newton observations. ... Low-significance candidate high-z clusters are followed up with the seven-channel imager GROND (Gamma-Ray Burst Optical and Near-Infrared Detector) that is mounted at a 2m-class telescope. ... The test case is XMMU J0338.7+0030, suggested to be at z~1.45+/-0.15 from the analysis of the z-H vs H colour-magnitude diagram obtained from the follow-up imaging. Later VLT-FORS2 spectroscopy enabled us to identify four members, which set this cluster at z=1.097+/-0.002. To reach a better knowledge of its galaxy population, we observed XMMU J0338.7+0030 with GROND for about 6 hr. The publicly available photo-z code le Phare was used. The Ks-band number counts of the non-stellar sources out of the 832 detected down to z'~26 AB-mag in the 3.9x4.3 square arcmin region of XMMU J0338.7+0030 imaged at all GROND bands clearly exceed those computed in deep fields/survey areas at ~20.5 - 22.5 AB-mag. The photo-z's of the three imaged spectroscopic members yield z=1.12+/-0.09. The spatial distribution and the properties of the GROND sources with a photo-z in the range 1.01 - 1.23 confirm the correspondence of the X-ray source with a galaxy over-density at a significance of at least 4.3 sigma. Candidate members that are spectro-photometrically classified as elliptical galaxies define a red locus in the i'-z' vs z' colour-magnitude diagram that is consistent with the red sequence of the cluster RDCS J0910+5422 at z=1.106. XMMU J0338.7+0030 hosts also a population of bluer late-type spirals and irregulars. The starbursts among the photometric members populate both loci, consistently with previous results. The analysis of the available data set indicates that XMMU J0338.7+0030 is a low-mass cluster (M_200 ~ 1E14 M_sun) at z=1.1. (Abridged), Comment: accepted for publication in Astronomy & Astrophysics Main Journal, 27 pages, 24 figures, 1 table

We present the largest sample of spectroscopically confirmed X-ray luminous high-redshift galaxy clusters to date comprising 22 systems in the range 0.9\sim0.9. We present first details of two newly identified clusters, XDCP J0338.5+0029 at z=0.916 and XDCP J0027.2+1714 at z=0.959, and investigate the Xray properties of SpARCS J003550-431224 at z=1.335, which shows evidence for ongoing major merger activity along the line-of-sight. We provide X-ray properties and luminosity-based total mass estimates for the full sample, which has a median system mass of M200\simeq2\times10^14M\odot. In contrast to local clusters, the z>0.9 systems do mostly not harbor central dominant galaxies coincident with the X-ray centroid position, but rather exhibit significant BCG offsets from the X-ray center with a median value of about 50 kpc in projection and a smaller median luminosity gap to the second-ranked galaxy of \sim0.3mag. We estimate a fraction of cluster-associated NVSS 1.4GHz radio sources of about 30%, preferentially located within 1' from the X-ray center. The galaxy populations in z>\sim1.5 cluster environments show first evidence for drastic changes on the high-mass end of galaxies and signs for a gradual disappearance of a well-defined cluster red-sequence as strong star formation activity is observed in an increasing fraction of massive galaxies down to the densest core regions., Comment: 61 pages, 13 color figures, accepted for publication in New Journal of Physics for the focus issue on 'Galaxy Clusters'

Context: Multi-wavelength surveys for clusters of galaxies are opening a window on the elusive high-redshift (z>1) cluster population. Well controlled statistical samples of distant clusters will enable us to answer questions about their cosmological context, early assembly phases and the thermodynamical evolution of the intracluster medium. Aims: We report on the detection of two z>1 systems, XMMU J0302.2-0001 and XMMU J1532.2-0836, as part of the XMM-Newton Distant Cluster Project (XDCP) sample. We investigate the nature of the sources, measure their spectroscopic redshift and determine their basic physical parameters. Methods: The results of the present paper are based on the analysis of XMM-Newton archival data, optical/near-infrared imaging and deep optical follow-up spectroscopy of the clusters. Results: We confirm the X-ray source XMMU J0302.2-0001 as a gravitationally bound, bona fide cluster of galaxies at spectroscopic redshift z=1.185. We estimate its M500 mass to (1.6+/-0.3) times 10^{14} Msun from its measured X-ray luminosity. This ranks the cluster among intermediate mass system. In the case of XMMU J1532.2-0836 we find the X-ray detection to be coincident with a dynamically bound system of galaxies at z=1.358. Optical spectroscopy reveals the presence of a central active galactic nucleus, which can be a dominant source of the detected X-ray emission from this system. We provide upper limits of X-ray parameters for the system and discuss cluster identification challenges in the high-redshift low-mass cluster regime. A third, intermediate redshift (z=0.647) cluster, XMMU J0302.1-0000, is serendipitously detected in the same field as XMMU J0302.2-0001. We provide its analysis as well., Comment: Accepted to A&A, 13/04/2011. 15 pages, 18 figures, 5 tables, 2 appendices

[Abridged] XMMU J2235.3-2557 is one of the most distant X-ray selected clusters, spectroscopically confirmed at z=1.39. We characterize the galaxy populations of passive members, the thermodynamical properties of the hot gas, its metal abundance and the total mass of the system using imaging data with HST/ACS (i775 and z850 bands) and VLT/ISAAC (J and K_s bands), extensive spectroscopic data obtained with VLT/FORS2, and deep Chandra observations. Out of a total sample of 34 spectroscopically confirmed cluster members, we selected 16 passive galaxies within the central 2' (or 1 Mpc) with ACS coverage, and inferred star formation histories for a sub-sample of galaxies inside and outside the core by modeling their spectro-photometric data with spectral synthesis models, finding a strong mean age radial gradient. Chandra data show a regular elongated morphology, closely resembling the distribution of core galaxies, with a significant cool core. We measure a global X-ray temperature of kT=8.6(-1.2,+1.3) keV (68% c.l.). By detecting the rest-frame 6.7 keV Iron K line, we measure a metallicty Z= 0.26(+0.20,-0.16) Zsun. In the likely hypothesis of hydrostatic equilibrium, we obtain a total mass of Mtot(<1 Mpc)=(5.9+-1.3)10^14 Msun. Overall, our analysis implies that XMM2235 is the hottest and most massive bona-fide cluster discovered to date at z>1, with a baryonic content, both its galaxy population and intra-cluster gas, in a significantly advanced evolutionary stage at 1/3 of the current age of the Universe., Comment: 9 pages, 8 figures, accepted for publication in A&A (v2: typos/language style corrections, updated references)

X-ray luminous clusters of galaxies at z~1 are emerging as major cosmological probes and are fundamental tools to study the cosmic large-scale structure and environmental effects of galaxy evolution at large look-back times. We present details of the newly-discovered galaxy cluster XMMU J0104.4-0630 at z=0.947 and a probable associated system in the LSS environment. The clusters were found in a systematic study for high-redshift systems using deep archival XMM-Newton data for the serendipitous detection and the X-ray analysis, complemented by optical/NIR imaging observations and spectroscopy of the main cluster. We find a well-evolved, intermediate luminosity cluster with Lx=(6.4+-1.3)x10^43 erg/s (0.5-2.0 keV) and strong central 1.4 GHz radio emission. The cluster galaxy population exhibits a pronounced transition toward bluer colors at cluster-centric distances of 1-2 core radii, consistent with an age difference of 1-2 Gyr for a single burst solar metallicity model. The second, less evolved X-ray cluster at a projected distance of 6.4 arcmin (~3 Mpc) and a concordant red-sequence color likely forms a cluster-cluster bridge with the main target as part of its surrounding large-scale structure at z~0.95., Comment: 5 pages, 4 figures, accepted for publication in A&A