Aims. Evidence is mounting that the main ingredients of the unification models of active galactic nuclei may behave differently from expectations, and be intimately related to fundamental physical parameters. The availability of high signal-to-noise broad-band X-ray spectra provides us with the opportunity to study in detail all the contributions from the materials invoked in these models, and infer their general properties, including whether their presence or absence is related to other quantities. Methods. We present a long (100 ks) Suzaku observation of one of the X-ray brightest AGN, MCG+8-11-11. These data are complemented with the 54-month Swift BAT spectrum, allowing us to perform a broad-band fit to the 0.6-150 keV range. Results. The fits performed in the 0.6-10 keV band provide results consistent with those of a a previous XMM-Newton observation, i.e. a lack of a soft excess, warm absorption along the line of sight, a large Compton reflection component (R 1), and an absence of a relativistic component of the neutral iron Kα emission line. However, when the PIN and Swift BAT data are included, the reflection amount drops significantly (R 0.2−0.3), and a relativistic iron line is required, the latter being confirmed by a phenomenological analysis in a restricted energy band (3-10 keV). When a self-consistent model is applied to the whole broad-band data, the observed reflection component appears to be entirely associated with the relativistic component of the iron Kα line. Conclusions. The implied scenario, though strongly model-dependent, requires that all the reprocessing spectral components from Compton-thick material be associated with the accretion disc, and no evidence of a classical pc-scale torus is found. The narrow core of the neutral iron Kα line is therefore produced in Compton-thin material, such as the BLR, similarly to what is found in another Seyfert galaxy, NGC 7213, but with the notable difference that MCG+8-11-11 presents spectral signatures from an accretion disc. The very low accretion rate of NGC 7213 could explain the lack of relativistic signatures in its spectrum, but the absence of the torus in both sources is more difficult to explain, since their luminosities are comparable, and their accretion rates are completely different.
Teaching modern physics in high school is of increasingly importance as it can offer students a more realistic and updated vision of the world, and can provide an opportunity to understand the most recent scientific discoveries. In this context, general relativity (GR) occupies a prominent place, since it is related to astonishing scientific results, such as the first image of a black hole or the discovery of gravitational waves. In this paper we describe an educational proposal aimed at teaching GR in high schools in a fun and playful way using the so-called rubber sheet analogy. We present a set of instructions to build a simple and low-cost space-time simulator, and a series of related educational cards that guide the teacher in the implementation of the activities step by step. This work is the result of a long and productive debate among Italian high school teachers who have collaborated for many years with the Department of Mathematics and Physics of Roma Tre University in Rome. As our proposal relies on the collaboration with the final users, we believe that it will meet their needs and expectations, and it will help to treat GR in high school more and more over time.
General relativity (GR) represents the most recent theory of gravity, on which all modern astrophysics is based, including some of the most astonishing results of physics research. Nevertheless, its study is limited to university courses, while being ignored at high-school level. To introduce GR in high school, one of the approaches that can be used is the so-called rubber sheet analogy (RSA), i.e. comparing space-time to a rubber sheet that deforms under a weight. In this paper, we analyse the efficacy of an activity for high-school students held at the Department of Mathematics and Physics of Roma Tre University that adopts the RSA to address several topics related to gravity. We present the results of the questionnaires we administered to over 150 Italian high-school students to investigate their understanding of the topics treated.
A relatively low geographical mobility of students in the Centre and North of the country and a large incidence of movers from southern regions to universities located in the Centre and North are well-established features of the Italian academic system. Exploiting a novel administrative dataset on academic enrolments, this paper shows that the interregional mobility of Italian students has increased in recent years. We highlight that the increase in mobility, which has occurred in a period of declining entry rates, is not attributable to a change in the composition of the enrolling students. We investigate some of the main drivers of student mobility by relating regional flows to the attractiveness of universities and show that mobility is positively associated with the quality of research and teaching and with the job prospects offered by the hosting university. Student flows are instead negatively correlated with the distance between the university and the region of origin and with drop-out rates. The empirical evidence also suggests that in recent years the distance from the university of destination has become less relevant in explaining mobility, whereas the role played by university quality has increased. JEL Classification: I20, I23.
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