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[en] Large fluxes of high-energy electrons are responsible for the non-thermal radio fluxes and probably the optical continua from compact sources in quasi-stellar objects. If they are accompanied by energetic fluxes of protons with energies > approximately 100 MeV, we expect that interaction with the gas will lead to spallation. Among the primary spallation products boron is the element which would be detectable in QSO spectra. The corresponding lines are absent, and by analyzing the ionization structure of the emitting and absorbing regions we find that the limit to the boron to carbon ratio is <= 1/15. Different models for explaining these results are discussed. (orig./BJ)
[de]Grosse, hochenergetische Elektronenfluesse sind fuer den nichtthermischen Radiofluss und wahrscheinlich fuer das optische Kontinuum von kompakten Quellen in quasistellaren Objekten verantwortlich. Wenn sie sie von Protonenfluessen mit Energien > approximately 100 MeV begleitet werden, erwarten wir, dass die Wechselwirkung mit dem Gas zur Spallation fuehrt. Unter den primaeren Spallationsprodukten ist Bor das Element, welches in QSO-Spektren messbar sein wuerde. Die entsprechenden Linien treten nicht auf. Die Untersuchung der Ionisationsstruktur der emittierenden und absorbierenden Bereiche liefert fuer das Bor zu Kohlenstoff-Verhaeltnis den Wert <= 1/15. Verschiedene Modelle, die dieses Ergebnis erklaeren koennen, werden diskutiert. (orig./BJ)
[en] Laming predicted that the narrow Balmer line core of the ∼3000 km s"−"1 shock in the SN 1006 remnant would be significantly polarized due to electron and proton impact polarization. Here, based on deep spectrally resolved polarimetry obtained with the European Southern Observatory (ESO)’s Very Large Telescope (VLT), we report the discovery of polarized line emission with a polarization degree of 1.3% and position angle orthogonal to the SNR filament. Correcting for an unpolarized broad line component, the implied narrow line polarization is ≈2.0%, close to the predictions of Laming. The predicted polarization is primarily sensitive to shock velocity and post-shock temperature equilibration. By measuring polarization for the SN 1006 remnant, we validate and enable a new diagnostic that has important applications in a wide variety of astrophysical situations, such as shocks, intense radiation fields, high energy particle streams, and conductive interfaces
[en] Gas at intermediate temperatures between the hot X-ray-emitting coronal gas in galaxies at the centers of galaxy clusters and the much cooler optical line emitting filaments yields information on transport processes and plausible scenarios for the relationship between X-ray cool cores and other galactic phenomena such as mergers or the onset of an active galactic nucleus. Hitherto, detection of intermediate temperature gas has proven elusive. Here, we present FUV imaging of the 'low excitation' emission filaments of M87 and show strong evidence for the presence of C IV 1549 A emission which arises in gas at temperature ∼105 K co-located with Hα+[N II] emission from cooler ∼104 K gas. We infer that the hot and cool phases are in thermal communication, and show that quantitatively the emission strength is consistent with thermal conduction, which in turn may account for many of the observed characteristics of cool-core galaxy clusters.
[en] The physical relationship between low-excitation gas filaments at ∼104 K, seen in optical line emission, and diffuse X-ray emitting coronal gas at ∼107 K in the centers of many galaxy clusters is not understood. It is unclear whether the ∼104 K filaments have cooled and condensed from the ambient hot (∼107 K) medium or have some other origin such as the infall of cold gas in a merger, or the disturbance of an internal cool reservoir of gas by nuclear activity. Observations of gas at intermediate temperatures (∼105-106 K) can potentially reveal whether the central massive galaxies are gaining cool gas through condensation or losing it through conductive evaporation and hence identify plausible scenarios for transport processes in galaxy cluster gas. Here we present spectroscopic detection of ∼105 K gas spatially associated with the Hα filaments in a central cluster galaxy, M87, in the Virgo Cluster. The measured emission-line fluxes from triply ionized carbon (C IV 1549 Å) and singly ionized helium (He II 1640 Å) are consistent with a model in which thermal conduction determines the interaction between hot and cold phases.
[en] The nature of the interaction between low-excitation gas filaments at ∼104 K, seen in optical line emission, and diffuse X-ray emitting coronal gas at ∼107 K in the centers of galaxy clusters remains a puzzle. The presence of a strong, empirical correlation between the two gas phases is indicative of a fundamental relationship between them, though as yet of undetermined cause. The cooler filaments, originally thought to have condensed from the hot gas, could also arise from a merger or the disturbance of cool circumnuclear gas by nuclear activity. Here, we have searched for intrinsic line emission polarization in cool core galaxy clusters as a diagnostic of fundamental transport processes. Drawing on developments in solar astrophysics, direct energetic particle impact induced polarization holds the promise to definitively determine the role of collisional processes such as thermal conduction in the ISM physics of galaxy clusters, while providing insight into other highly anisotropic excitation mechanisms such as shocks, intense radiation fields, and suprathermal particles. Under certain physical conditions, theoretical calculations predict of the order of 10% polarization. Our observations of the filaments in four nearby cool core clusters place stringent upper limits (≲ 0.1%) on the presence of emission line polarization, requiring that if thermal conduction is operative, the thermal gradients are not in the saturated regime. This limit is consistent with theoretical models of the thermal structure of filament interfaces.
[en] We report two detections of deuterated molecular hydrogen (HD) in QSO absorption-line systems at z>2. Toward J2123-0500, we find N(HD) =13.84 ± 0.2 for a sub-Damped Lyman Alpha system (DLA) with metallicity ≅0.5Zsun and N(H2) = 17.64 ± 0.15 at z = 2.0594. Toward FJ0812+32, we find N(HD) =15.38 ± 0.3 for a solar-metallicity DLA with N(H2) = 19.88 ± 0.2 at z = 2.6265. These systems have ratios of HD to H2 above that observed in dense clouds within the Milky Way disk and apparently consistent with a simple conversion from the cosmological ratio of D/H. These ratios are not readily explained by any available model of HD chemistry, and there are no obvious trends with metallicity or molecular content. Taken together, these two systems and the two published z>2 HD-bearing DLAs indicate that HD is either less effectively dissociated or more efficiently produced in high-redshift interstellar gas, even at low molecular fraction and/or solar metallicity. It is puzzling that such diverse systems should show such consistent HD/H2 ratios. Without clear knowledge of all the aspects of HD chemistry that may help determine the ratio HD/H2, we conclude that these systems are potentially more revealing of gas chemistry than of D/H itself and that it is premature to use such systems to constrain D/H at high redshift.