A candidate supermassive binary black hole system in the brightest cluster galaxy of RBS 797

The radio source at the center of the cool core galaxy cluster RBS 797 (z=0.35) is known to exhibit a misalignment of its radio jets and lobes observed at different VLA-scale, with the innermost kpc-scale jets being almost orthogonal to the radio emission which extends for tens of kpc filling the X-ray cavities. Gitti et al. suggested that this peculiar radio morphology may indicate a recurrent activity of the central radio source, where the jet orientation is changing between the different outbursts due to the effects of supermassive binary black holes (SMBBHs). We aim at unveiling the nuclear radio properties of the brightest cluster galaxy (BCG) in RBS 797 and at investigating the presence of a SMBBH system in its center. We have performed new high-resolution observations at 5 GHz with the European VLBI Network (EVN), reaching an angular resolution of 9x5 mas^2 and a sensitivity of 36 microJy/beam. We report the EVN detection of two compact components in the BCG of RBS 797, with a projected separation of ~77 pc. We can envisage two possible scenarios: the two components are two different nuclei in a close binary system, or they are the core and a knot of its jet. Both interpretations are consistent with the presence of SMBBHs. Our re-analysis of VLA archival data seems to favor the first scenario, as we detect two pairs of radio jets misaligned by ~90 degrees on the same kpc scale emanating from the central radio core. If the two outbursts are almost contemporaneous, this is clear evidence of the presence of two active SMBHs, whose radio nuclei are unresolved at VLA resolution. The nature of the double source detected by our EVN observations in the BCG of RBS 797 can be established only by future sensitive, multi-frequency VLBI observations. If confirmed, RBS 797 would be the first SMBBH system observed at medium-high redshift at VLBI resolution. (abridged)Comment: 4 pages, 2 figures, A&A Letter in pres

3D INTEGRATED SURVEYS AND STRATIGRAPHIC METHODS FOR A DEEPER UNDERSTANDING OF HISTORICAL BUILDINGS. A CASE-STUDY OF THE FRANCISCAN MONASTERY AND THE IMMACOLATA CHURCH IN TROINA, SICILY

Abstract. The study presents the results of the application of a multidisciplinary methodology for a deeper understanding of historical buildings. 3D integrated surveys and stratigraphic methods can together make it possible to date the principle construction and evolution phases of historical buildings for which a thorough historical documentation does not exist for our time.The case-study presented involves the Franciscan monastery and adjacent Immacolata church in Troina, which is a small medieval town located in the north-eastern part of Sicily.The small number of historical records has only allowed for the dating of the monastery's foundation and of a few of transformation phases. Contrarily to this, various markings on the surfaces of the walls indicate rather the presence of numerous construction phases.The inaccessibility of parts of the internal spaces, as well as the existence of a sharp incline of the road and of very high walls along scant sections of the road, are the reasons for having chosen to carry out a 3D laser-scanning survey campaign. It made it possible to document the overall area and the relationship between the different parts of the complex. The integration between 3D laser scanning and photo-modelling methods made it possible to highlight the details, anomalies, traces and signs of the stratifications over time. The results of this integrated survey were explained in a series of graphic elaborations in support to the following stratigraphic investigation, to put in order the numerous traces discovered.</p

First evidence of an egg-laying attempt of feral trachemys scripta (Schoepff, 1792) in sicily (lake pergusa, Italy)

First evidence of an egg-laying attempt of feral Trachemys scripta (Schoepff, 1792) in Sicily (Lake Pergusa, Italy

A COMBINED APPROACH FOR SURVEYING COMPLEX COASTAL SITES

Abstract. This study presents an integrated approach for reading coastal sites. A process aimed at protecting and enhancing these sites must be developed alongside a targeted interdisciplinary strategy, closely linked to the fields of archaeology, survey, landscape reading, morphology of the territory and geology. These must no longer be managed as individual cognitive elements, but within a single comprehensive analytical interpretation model.The experiment activity carried out along the rocky area of Aci Castello, on the eastern coast of Sicily, was developed using a methodological approach based on the integration of 3D data coming from various survey technologies &amp;ndash; 3D laser scanning, mobile mapping and echo sounder systems. The aim of the experiment was to create a complete three-dimensional model of the studied area, focused on obtaining a dynamic understanding, that is punctual and comprehensive, of the site's value and fragility.</p