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We analyze archival Chandra X-ray Observatory observations of Jupiter to search for emission from the Galilean moons. X-ray emission has previously been reported from Io and Europa using a subset of these data. We confirm this detection, and marginally detect X-ray emission from both Ganymede and Callisto as well. The X-ray spectrum of Europa is strongly peaked around the neutral oxygen fluorescence line (525 eV), while Io's has peaks at both oxygen and sulfur (2308 eV) plus a broad continuum between 350 and 5000 eV. Ganymede's spectrum is similar to Io's, but without the sulfur peak. A few events, mostly clustered around the oxygen line, are detected from Callisto. Using measurements by the Galileo mission of the specific intensity of ambient protons and electrons, we model the X-ray spectra and flux of the moons from two processes: particle-induced X-ray emission (PIXE) from the impact of energetic protons and X-ray emission from electron bremsstrahlung. With uncertainties of a factor of a few, the electron bremsstrahlung and PIXE models overestimate the X-ray flux from Europa, preventing us from making a definitive statement about the origin of the X-ray emission. The PIXE model of Io predicts emission lines at O and S similar to those observed, but underestimates their flux by nearly two orders of magnitude. Based on this discrepancy in the PIXE flux, combined with the detected broadband continuum in the spectrum, we conclude that the X-ray emission from Io is due to electron bremsstrahlung. Likewise, because of Ganymede's broad continuum, we tentatively conclude that its X-ray emission is also due to electron bremsstrahlung. Callisto is too faint in the X-rays to draw any conclusion. Obtaining in situ X-ray observations of the moons would provide a direct measurement of their elemental composition. [ABSTRACT FROM AUTHOR]

We report our analysis of MACS J0717.5+3745 using 140 and 268 GHz Bolocam data collected at the Caltech Submillimeter Observatory. We detect extended Sunyaev-Zel'dovich (SZ) effect signal at high significance in both Bolocam bands, and we employ Herschel-SPIRE observations to subtract the signal from dusty background galaxies in the 268 GHz data. We constrain the two-band SZ surface brightness toward two of the sub-clusters of MACS J0717.5+3745: the main sub-cluster (named C), and a sub-cluster identified in spectroscopic optical data to have a line-of-sight velocity of +3200 km s–1 (named B). We determine the surface brightness in two separate ways: via fits of parametric models and via direct integration of the images. For both sub-clusters, we find consistent surface brightnesses from both analysis methods. We constrain spectral templates consisting of relativistically corrected thermal and kinetic SZ signals, using a jointly-derived electron temperature from Chandra and XMM-Newton under the assumption that each sub-cluster is isothermal. The data show no evidence for a kinetic SZ signal toward sub-cluster C, but they do indicate a significant kinetic SZ signal toward sub-cluster B. The model-derived surface brightnesses for sub-cluster B yield a best-fit, line-of-sight velocity of vz = +3450 ± 900 km s–1, with (1 – Prob[vz ⩾ 0]) = 1.3 × 10–5 (4.2σ away from 0 for a Gaussian distribution). The directly integrated sub-cluster B SZ surface brightnesses provide a best-fit vz = +2550 ± 1050 km s–1, with (1 – Prob[vz ⩾ 0]) = 2.2 × 10–3 (2.9σ). [ABSTRACT FROM AUTHOR]

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, likely due to a separate ongoing merger. Evidence for this is also seen in optical data. A98S hosts a wide-angle tail radio source powered by a central active galactic nucleus (AGN). We find evidence for a cavity in the intracluster medium that has been evacuated by one of the radio lobes, suggesting that AGN feedback is operating in this system. Examples of cavities in non-cool core clusters are relatively rare. The three subclusters lie along a line in projection, suggesting the presence of a large-scale filament. We observe emission along the filament between A98N and A98S, and a surface brightness profile shows emission consistent with the overlap of the subcluster extended gas halos. We find the temperature of this region is consistent with the temperature of the gas at similar radii outside this bridge region. Lastly, we examine the cluster dynamics using optical data. We conclude A98N and A98S are likely bound to one another with a 67% probability, while A98S and A98SS are not bound at a high level of significance. [ABSTRACT FROM AUTHOR]