Correlation between X-ray and radio absorption in compact radio galaxies

Compact radio galaxies with a GHz-peaked spectrum (GPS) and/or compact-symmetric-object (CSO) morphology (GPS/CSOs) are increasingly detected in the X-ray domain. Their radio and X-ray emissions are affected by significant absorption. However, the locations of the X-ray and radio absorbers are still debated. We investigated the relationship between the column densities of the total ($N_{\mathrm{H}}$) and neutral ($N_{\mathrm{HI}}$) hydrogen to statistically constrain the picture. We compiled a sample of GPS/CSOs including both literature data and new radio data that we acquired with the Westerbork Synthesis Radio Telescope for sources whose X-ray emission was either established or under investigation. In this sample, we compared the X-ray and radio hydrogen column densities, and found that $N_{\mathrm{H}}$ and $N_{\mathrm{HI}}$ display a significant positive correlation, with $N_{\mathrm{HI}} \propto N_{\mathrm{H}}^b$, where $b=0.47$ and $b=0.35$, depending on the subsample. The $N_{\mathrm{H}}$ - $N_{\mathrm{HI}}$ correlation suggests that the X-ray and radio absorbers are either co-spatial or different components of a continuous structure. The correlation displays a large intrinsic spread that we suggest to originate from fluctuations, around a mean value, of the ratio between the spin temperature and the covering factor of the radio absorber, $T_{\rm s}/C_{\rm f}$.Comment: 18 pages, 5 figures, 6 tables; final version: a few typos corrected, minor style change

First detection in gamma-rays of a young radio galaxy: Fermi-LAT observations of the Compact Symmetric Object PKS 1718-649

We report the $\gamma$-ray detection of a young radio galaxy, PKS 1718$-$649, belonging to the class of Compact Symmetric Objects (CSOs), with the Large Area Telescope (LAT) on board the {\it Fermi} satellite. The third {\it Fermi} Gamma-ray LAT catalog (3FGL) includes an unassociated $\gamma$-ray source, 3FGL J1728.0$-$6446, located close to PKS 1718$-$649. Using the latest Pass 8 calibration, we confirm that the best fit $1 \sigma$ position of the $\gamma$-ray source is compatible with the radio location of PKS 1718$-$649. Cross-matching of the $\gamma$-ray source position with the positions of blazar sources from several catalogs yields negative results. Thus, we conclude that PKS 1718$-$649 is the most likely counterpart to the unassociated LAT source. We obtain a detection test statistics TS$\sim 36$ ($>$5$\sigma$) with a best fit photon spectral index $\Gamma=$2.9$\pm$0.3 and a 0.1-100 GeV photon flux density $F_{\rm 0.1-100GeV}=$(11.5$\pm$0.3)$\times{\rm 10^{-9}}$ ph cm$^{-2}$ s$^{-1}$. We argue that the linear size ($\sim$2 pc), the kinematic age ($\sim$100 years), and the source distance ($z=0.014$) make PKS 1718$-$649 an ideal candidate for $\gamma$-ray detection in the framework of the model proposing that the most compact and the youngest CSOs can efficiently produce GeV radiation via inverse-Compton scattering of the ambient photon fields by the radio lobe non-thermal electrons. Thus, our detection of the source in $\gamma$-rays establishes young radio galaxies as a distinct class of extragalactic high-energy emitters, and yields an unique insight on the physical conditions in compact radio lobes interacting with the interstellar medium of the host galaxy.Comment: 7 pages, 2 figures, accepted for publication in ApJ Letter

Multi-frequency VLBA study of the blazar S5 0716+714 during the active state in 2004: I. Inner jet kinematics

We observed the blazar \object{0716+714} with the VLBA during its active state in 2003-2004. In this paper we discuss multi-frequency analysis of the inner jet (first 1 mas) kinematics. The unprecedentedly dense time sampling allows us to trace jet components without misidentification and to calculate the component speeds with good accuracy. In the smooth superluminal jet we were able to identify and track three components over time moving outwards with relatively high apparent superluminal speeds (8.5-19.4 $c$), which contradicts the hypothesis of a stationary oscillating jet in this source. Component ejections occur at a relatively high rate (once in two months), and they are accompanied by mm-continuum outbursts. Superluminal jet components move along wiggling trajectories, which is an indication of actual helical motion. Fast proper motion and rapid decay of the components suggest that this source should be observed with the VLBI at a rate of at least once in one or two months in order to trace superluminal jet components without confusion.Comment: 4 pages, 3 figures, Astronomy & Astrophysics Letter, language corrections adde

Alain Boureau, Satan hérétique. Naissance de la démonologie dans l'Occident médiéval (1280-1330)

L'un des buts du nouvel ouvrage d'Alain Boureau est de montrer comment la chasse aux sorcières qui émerge dès 1430 est en continuité avec la démonologie scolastique développée un siècle plus tôt, entre 1280 et 1330. La rationalité scolastique, par son travail constant d'interrogation et d'exploration intellectuelle, a ouvert de dangereux champs de réflexion, en redéfinissant les rapports entre l'homme et les démons : elle a en partie rendu possible l'émergence du sabbat. L'hypothèse de l'aute..

Comment communiquer et diffuser le 'crime' de sorcellerie et le sabbat au XVe siècle ? L'exemple des Errores gazariorum et du Flagellum hereticorum fascinariorum de Nicolas Jacquier

Der anonyme Traktat der Errores Gazariorum (ca. 1436) und der Flagellum hereticorum fascinariorum (1458) des burgundischen Inquisitors Nicolas Jacquier bieten interessante Beispiele für kulturellen Austausch: diese Texte sind in zwei verschiedenen Sprachräumen verbreitet, dem französischen und den deutschen, und erreichen auch das Heilige Römische Reich deutscher Nation, wo sie auf unterschiedliche Interessenten stossen. Die Errores Gazariorum wandern von ihrem Ursprungsort, dem Aostatal, nach der Französischen Schweiz und nach Basel, und von da aus bis in die Pfalz, wo sie ins Deutsche übersetzt werden. Hier finden sie auch Eingang in eine ganz andere narrative Gattung, nämlich die Chronik, was ihnen eine noch weitere Verbreitung sichert. Was die Verbreitung der Schriften und der Ideen des Nicolas Jacquier betrifft, so wird diese durch die Reisen dieses Inquisitors zwischen Lyon, dem burgundischen Staat, dem Reich und dem Königreich Böhmen begünstigt, insbesondere durch die diplomatischen Missionen, die dieser im Dienst des Herzogs von Burgund, Philipps des Guten, unternimmt. Die Orte, wo seine Texte benützt werden, sind häufig Orte, wo Hexenverfolgungen stattfinden oder über den Sabbat diskutiert wird. In der einen oder anderen Weise sind die hier besprochenen Texte auch mit dem Konzil von Basel (1431-1449) verbunden, welches für die Vernetzung von Personen und die Verbreitung von Ideen und Texten über die Vorstellungswelt des Sabbats einen idealen Nährboden bietet