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Register a new userA BeppoSAX observation of the merging cluster Abell 3266
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We present results from a BeppoSAX observation of the rich cluster Abell 3266. The broad band spectrum (2-50 keV) of the cluster, when fitted with an optically thin thermal emission model, yields a temperature of 8.1 +/- 0.2 keV and a metal abundance of 0.17 +/- 0.02 in solar units, and with no evidence of a hard X-ray excess in the PDS spectrum. By performing a spatially resolved spectral analysis we find that the projected temperature drops with increasing radius, going from ~ 10 keV at the cluster core to ~ 5 keV at about 1.5 Mpc. Our BeppoSAX temperature profile is in good agreement with the ASCA temperature profile of Markevitch et al. (1998). From our two-dimensional temperature map we find that the gradient is observed in all azimuthal directions. The temperature gradient may have been caused by a recent merger event also responsible for a velocity dispersion gradient measured in the optical band. The projected metal abundance profile and two-dimensional map are both consistent with being constant.
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The galaxy cluster Abell 3266 is one of the X-ray brightest in the sky and is a well-known merging system. Using the ability of the eROSITA telescope onboard SRG (Spectrum Rontgen Gamma) to observe a wide field with a single pointing, we analyse a new observation of the cluster out to a radius of R_200. The X-ray images highlight substructures present in the cluster, including the northeast-southwest merger seen in previous ASCA, Chandra and XMM-Newton data, a merging group towards the northwest and filamentary structures between the core and one or more groups towards the west. We compute spatially-resolved spectroscopic maps of the thermodynamic properties of the cluster, including the metallicity. The merging subclusters are seen as low entropy material within the cluster. The filamentary structures could be the rims of a powerful AGN outburst, or most likely material stripped from the western group(s) as they passed through the cluster core. Seen in two directions is a pressure jump at a radius of 1.1 Mpc consistent with a shock with a Mach number of ~1.5-1.7. The eROSITA data confirm that the cluster is not a simple merging system, but is made up of several subclusters which are merging or will shortly merge. For the first time we find a radio halo associated with the system detected in GLEAM data. We compute a hydrostatic mass from the eROSITA data, finding good agreement with a previous XMM-Newton result. With this pointing we detect several extended sources, where we find for seven of them secure associations between z=0.36-1.0; i.e., background galaxy groups and clusters, highlighting the power of eROSITA to find such systems.
We report new results on the cluster of galaxies Abell 970 obtained from X-ray observation with BeppoSAX. Our analysis of the BeppoSAX MECS and LECS data in the range [0.15-10] keV reveals a mean cluster gas temperature of kT = 4.46_{-0.15}^{+0.14}, a metallicity of Z = 0.31_{-0.04}^{+0.05} Z_odot, and an interstellar hydrogen absorption density column of N_H = 6.05_{-0.97}^{+1.29} 10^20 cm^-2. Moreover, we obtained azimuthally averaged radial profiles of these quantities. Our results are consistent with the hypothesis that Abell 970 has been disturbed by a past merger or by the ongoing merger process of a substructure, that put the cluster out of equilibrium. This is also demonstrated by the offset between the gas and galaxy distributions. Combining the X-ray data with a recently published analysis of new galaxy radial velocities, we conclude that a subcluster 8 arcmin to the NW is falling into Abell 970 and will merge in a few Gigayears, thus disturbing Abell 970s newly acquired equilibrium. The high alpha-elements/iron ratio that we derive for this cluster supports the hypothesis of early intracluster medium enrichment by Type II supernovae.
We report the observation of the Intra-Cluster Medium (ICM) of Abell 85 by the X-ray satellite BeppoSAX. We have both analysed the spectrum obtained in the central 8 arcmin circular region centred on the Very Steep Spectrum Radio Source (VSSRS) and the spectra from a number of sub-regions. Analysis of the spectra allowed us to independently obtain new estimates of the temperature, metallicity and line-of-sight hydrogen density column, both globally (T=6.6pm0.3 keV, Z = 0.38pm0.06 Z_odot and N_H = 5.5^+0.9_-0.7 10^20 cm^-2) and locally. These measures are in good agreement with previous measures based on ROSAT and ASCA data. In the region of the VSRSS, we have tried to disentangle the thermal from the non-thermal X-ray emission. Although we could not do this unambiguously, we have nonetheless estimated the extended magnetic field using the radio spectrum available for this region. We obtain a lower limit intensity of 0.9 mu G, consistent with our previous estimate. We also derive alpha-elements/iron abundance ratios that turn out to be higher than 1. Such a result tends to support the burst model for elliptical galaxies, where a strong galactic wind develops early in the galaxy history and type II supernovae (SN) may have the main role in the enrichment of the ICM. A two-temperature ICM model was fitted in the central region yielding a main component with roughly the mean cluster temperature and a cooler component with temperature less than 0.1 keV.
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$beta$]), indicative of starburst and post starburst, respectively with ram-pressure, $rho$v$^{2}$, calculated from the X-ray and optical data. We find that post-starburst galaxies, classified as E+A, occur at a higher frequency in this merging cluster than in the Coma cluster and at a comparable rate to intermediate redshift clusters. This is consistent with increased star formation due to the merger. However, both starburst and post-starburst galaxies are equally likely to be in a low or high ram pressure environment. From this result we infer that the duration of the starburst phase must be very brief so that: (1) at any time only a small fraction of the galaxies in a high ram pressure environment show this effect, and (2) most post-starburst galaxies are in an environment of low ram pressure due too their continued orbital motion in the cluster.
We present an analysis of BeppoSAX observations of the IC1262 galaxy cluster and report the first temperature and abundance measurements, along with preliminary indications of diffuse, nonthermal emission. By fitting a 6 (~360 h_50^-1 kpc) region with a single Mewe-Kaastra-Liedahl model with photoelectric absorption, we find a temperature of 2.1 - 2.3 keV, and abundance of 0.45 - 0.77 (both 90% confidence). We find the addition of a power-law component provides a statistically significant improvement (F-test = 90%) to the fit. The addition of a second thermal component also improves the fit but we argue that it is physically implausible. The power-law component has a photon index (Gamma_X) of 0.4 - 2.8 and a nonthermal flux of (4.1 - 56.7) x 10-5 photons cm^-2 s^-1 over the 1.5 - 10.5 keV range in the Medium Energy Concentrator spectrometer detector. An unidentified X-ray source found in the ROSAT High Resolution Imager observation (~0.9 from the center of the cluster) is a possible explanation for the nonthermal flux; however, additional evidence of diffuse, nonthermal emission comes from the NRAO VLA Sky Survey and the Westerbork Northern Sky Survey radio measurements, in which excess diffuse, radio flux is observed after point-source subtraction. The radio excess can be fitted to a simple power law with a spectral index of ~1.8, which is consistent with the nonthermal X-ray emission spectral index. The steep spectrum is typical of diffuse emission and the size of the radio source implies that it is larger than the cD galaxy and not due to a discreet source.
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