New results from the HRX BL Lac sample

We present results for the Hamburg BL Lac sample, based on data provided by the RASS-BSC. By fitting a single power law to the X-ray data we find, in a number of objects, an additional absorbing component to the galactic value of NH, which might be attributed to intrinsic absorption. A more probable cause seems however to be a curvature in the X-ray spectra in the sense that they are more curved for steeper slopes. The known relation between the X-ray spectral slope and the ratio between optical and X-ray flux alpha_ox also applies to this BL Lac sample, even though less significant than in previous works. We also find a dependence of X-ray luminosity on alpha_ox.Comment: 4 pages, 3 figures, Proceedings of the Conference X-ray Astronomy'99: Stellar Endpoints, AGN and Diffuse Background. To appear in Astrophysical Letters and Communication

Radio spectra of a sample of X-ray selected BL Lacs

We present simultaneous multifrequency radio observations for a complete subsample of 26 XBLs from the Einstein Extended Medium-Sensitivity Survey, obtained with the Very Large Array (VLA). Spectra are computed using fluxes at 20, 6 and 3.6 cm. Unlike many radio selected samples, the EMSS did not impose any criterion on the radio spectrum to identify BL Lac objects. It is therefore possible to investigate the intrinsic radio spectral slope distribution and to determine the effect produced by this selection criterion. We find that 15% of the observed objects do not meet the flat-spectrum criterion imposed on some other BL Lac samples. A dataset that includes non-simultaneous data (that are also taken with different VLA configurations) shows an even higher percentage of steep spectrum sources. This effect can be ascribed to a larger fraction of extended flux detected with the more compact VLA configuration.Possible biases introduced by the flat--radio-spectrum criterion in the radio-selected BL Lac samples cannot explain the discrepancies observed in the evolutionary properties of Radio and X-ray selected samples of BL Lacs.Comment: 9 pages, 5 figures, to be published in Astronomy and Astrophysic

Galaxies as High-Resolution Telescopes

Recent observations show a population of active galaxies with milliarcseconds offsets between optical and radio emission. Such offsets can be an indication of extreme phenomena associated with supermassive black holes including relativistic jets, binary supermassive black holes, or even recoiling supermassive black holes. However, the multi-wavelength structure of active galaxies at a few milliarcseconds cannot be fathomed with direct observations. We propose using strong gravitational lensing to elucidate the multi-wavelength structure of sources. When sources are located close to the caustic of lensing galaxy, even small offset in the position of the sources results in a drastic difference in the position and magnification of mirage images. We show that the angular offset in the position of the sources can be amplified more than 50 times in the observed position of mirage images. We find that at least 8% of the observed gravitationally lensed quasars will be in the caustic configuration. The synergy between SKA and Euclid will provide an ideal set of observations for thousands of gravitationally lensed sources in the caustic configuration, which will allow us to elucidate the multi-wavelength structure for a large ensemble of sources, and study the physical origin of radio emissions, their connection to supermassive black holes, and their cosmic evolution.Comment: Accepted for publication in Ap

The Tiered Radio Extragalactic Continuum Simulation (T-RECS)

We present the Tiered Radio Extragalactic Continuum Simulation (T-RECS): a new simulation of the radio sky in continuum, over the 150 MHz-20 GHz range. T-RECS models two main populations of radio galaxies: Active Galactic Nuclei (AGNs) and Star-Forming Galaxies (SFGs), and corresponding sub-populations. Our model also includes polarized emission over the full frequency range, which has been characterised statistically for each population using the available information. We model the clustering properties in terms of probability distributions of hosting halo masses, and use lightcones extracted from a high-resolution cosmological simulation to determine the positions of haloes. This limits the sky area for the simulations including clustering to a 25deg2 field of view. We compare luminosity functions, number counts in total intensity and polarization, and clustering properties of our outputs to up-to-date compilations of data and find a very good agreement. We deliver a set of simulated catalogues, as well as the code to produce them, which can be used for simulating observations and predicting results from deep radio surveys with existing and forthcoming radio facilities, such as the Square Kilometre Array (SKA).Comment: 20 pages, 11 figures, accepted by MNRA

Gravitational Lenses as High-Resolution Telescopes

The inner regions of active galaxies host the most extreme and energetic phenomena in the universe including, relativistic jets, supermassive black hole binaries, and recoiling supermassive black holes. However, many of these sources cannot be resolved with direct observations. I review how strong gravitational lensing can be used to elucidate the structures of these sources from radio frequencies up to very high energy gamma rays. The deep gravitational potentials surrounding galaxies act as natural gravitational lenses. These gravitational lenses split background sources into multiple images, each with a gravitationally-induced time delay. These time delays and positions of lensed images depend on the source location, and thus, can be used to infer the spatial origins of the emission. For example, using gravitationally-induced time delays improves angular resolution of modern gamma-ray instruments by six orders of magnitude, and provides evidence that gamma-ray outbursts can be produced at even thousands of light years from a supermassive black hole, and that the compact radio emission does not always trace the position of the supermassive black hole. These findings provide unique physical information about the central structure of active galaxies, force us to revise our models of operating particle acceleration mechanisms, and challenge our assumptions about the origin of compact radio emission. Future surveys, including LSST, SKA, and Euclid, will provide observations for hundreds of thousands of gravitationally lensed sources, which will allow us to apply strong gravitational lensing to study the multi-wavelength structure for large ensembles of sources. This large ensemble of gravitationally lensed active galaxies will allow us to elucidate the physical origins of multi-wavelength emissions, their connections to supermassive black holes, and their cosmic evolution.Comment: Invited (Accepted) review for Physics Report

BeppoSAX Observations of 1 Jy BL Lacertae Objects. I

We present new BeppoSAX observations of seven BL Lacertae objects selected from the 1 Jy sample plus one additional source. The collected data cover the energy range 0.1 - 10 keV (observer's frame), reaching ~ 50 keV for one source (BL Lac). All sources characterized by a peak in their multifrequency spectra at infrared/optical energies (i.e., of the LBL type) display a relatively flat (alpha_x ~ 0.9) X-ray spectrum, which we interpret as inverse Compton emission. Four objects (2/3 of the LBL) show some evidence for a low-energy steepening which is likely due to the synchrotron tail merging into the inverse Compton component around ~ 1 - 3 keV. If this were generally the case with LBL, it would explain why the 0.1 - 2.4 keV ROSAT spectra of our sources are systematically steeper than the BeppoSAX ones (by ~ 0.5 in alpha_x). The broad-band spectral energy distributions fully confirm this picture and a synchrotron inverse Compton model allows us to derive the physical parameters (intrinsic power, magnetic field, etc.) of our sources. Combining our results with those obtained by BeppoSAX on BL Lacs covering a wide range of synchrotron peak frequencies, we confirm and clarify the dependence of the X-ray spectral index on synchrotron peak frequency originally found in ROSAT data.Comment: 14 pages, 7 figures. Accepted for publication in MNRAS. Postscript file also available at http://icarus.stsci.edu/~padovani/xrayspectra_papers.htm

Estimation of the flooded area over the pantanal, a South American floodplain, using modis data

Tropical floodplains, such as Pantanal in Central South America, are important features for land-atmosphere interactions. Schemes to account for floodplains should therefore be included in Earth System Models, but this requires observations of flooded area for validation. Satellite data is a possible solution to estimate the flooded area but it is important to evaluate the different flood detection algorithms available in order to use the most efficient for the region. This work explores different methods to estimate the flooded area from the MODIS MOD09A1 satellite surface reflectance product using spectral indexes (mNDWI, NDMI, NDMI-NDVI) to detect the presence of water. We include the traditional threshold-based methods but also some unsupervised classification methods such as the k-means and the Principal Component Analysis applied on the water-related spectral indexes. The calibration and validation of these methods are based on the hydrological knowledge of the region, coming from land surface models, river discharge observation and from previous satellite estimations of the flooded area. The NDMI index seems too sensible to the vegetation which leads to error in the estimation of the flooded area. The other methods were spatially and temporally consistent with previous studies over the Pantanal.Las llanuras aluviales tropicales, como el Pantanal en el centro de América del Sur, son características importantes para las interacciones tierra-atmósfera. Por lo tanto, los esquemas para dar cuenta de las llanuras aluviales deberían incluirse en los modelos del sistema terrestre, pero esto requiere observaciones del área inundada para su validación. Los datos satelitales son una posible solución para estimar el área inundada, pero es importante evaluar los diferentes algoritmos de detección de inundaciones disponibles para utilizar el más eficiente para la región. Este trabajo explora diferentes métodos para estimar el área inundada a partir del producto de reflectancia de superficie del satélite MODIS MOD09A1 utilizando índices espectrales (mNDWI, NDMI, NDMI-NDVI) para detectar la presencia de agua. Incluimos los métodos tradicionales basados ​​en umbrales, pero también algunos métodos de clasificación no supervisados, como las k-medias y el Análisis de Componentes Principales aplicados a los índices espectrales relacionados con el agua. La calibración y validación de estos métodos se basan en el conocimiento hidrológico de la región, proveniente de modelos de superficie terrestre, observación de caudales de ríos y de estimaciones satelitales previas del área inundada. El índice NDMI parece demasiado sensible a la vegetación, lo que induce a errores en la estimación de la superficie inundada. Los otros métodos fueron espacial y temporalmente consistentes con estudios previos sobre el Pantanal.Fil: Schrapffer, Anthony. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina. Instituto Franco-Argentino sobre Estudios del Clima y sus Impactos; ArgentinaFil: Cappelletti, Lucía María. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina. Instituto Franco-Argentino sobre Estudios del Clima y sus Impactos; ArgentinaFil: Sörensson, Anna. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina. Instituto Franco-Argentino sobre Estudios del Clima y sus Impactos; Argentin

Planning Wastescapes Through Collaborative Processes

The chapter is focused on collaborative processes through which the functions and spatial hierarchies of public or public use areas are redefined. The field of action is: on the one hand the urban metabolism, interpreted as a study of the life cycle of the city, including wastescapes; on the other, collaborative processes, aimed at defining the uses of tailored, place-based, and collective services. In this sense, the research moves from the analysis of places born for public use, but abandoned over time or never actually completed; disused places waiting to reenter the urban metabolism. Among those, there are also Italian “planning standards,” publicly designed in compliance with the quantities defined by law, and often partially used or not properly managed. The proposal of new uses and services for these contexts is based on criteria of flexibility, not fixed once and for all, not predetermined in time, but in progress in order to overcome the limits of the implementation of policies and programs of the past. These integrated processes can activate a dialogue between public institutions, privates, local associations and citizens’ groups. The research also intends to cross-reference the issue of spatial inequalities in access to spaces and services, with the evolution of the public actor from provider to service enabler, in a wider redefinition of welfare and welfare spaces concept, as an effect of global economic and financial crisis. The question needs non-sectoral responses, which take into account environmental, social, spatial issues. Welfare can no longer be provided as a self-sufficiency device: contextual services, for everyone, can be realized by recapitalizing wastescapes, co-creating “planning standards” through the recovery of degraded local contexts, collectively investing in the use and care of public, and open services. The paper will focus on: (a) the case of the former NATO area in Naples (in Bagnoli neighborhood) which is the subject of a Plan for urban renewal, adopted by the Municipality of Naples in 2020. The area, owned by a public company whose purpose is the assistance of children in the disadvantaged segment (Fondazione Campania Welfare), has been redesigned as a public facility on a metropolitan scale, within a public consultation process between the ownership, the Municipality of Naples and several local stakeholders (third sector organizations, citizens, cultural associations, etc.). As an effect of this collaborative process, the reuse of the area started before the adoption of the Plan; (b) the case of Horizon2020 research REPAiR in which the issue of circular economy applied to the recovery of wastescapes for public purposes has been investigated in living labs, working on waste perception and awareness as key factors for regenerating wastelands. The co-creation process partly resumed a strategy foreseen in 2013 by the Campania Region in the Plan of waste prevention, for the implementation of Integrated Centres for the reuse of durable goods, originally excluded by the Regional Waste Law