Water megamaser emission in hard X-ray selected AGN

Water megamaser emission at 22 GHz has proven to be a powerful tool for astrophysical studies of AGN allowing an accurate determination of the central black hole mass and of the accretion disc geometry and dynamics. However, after searches among thousands of galaxies, only ~ 200 of them have shown such spectroscopic features, most of them of uncertain classification. In addition, the physical and geometrical conditions under which maser activates are still unknown. In this work we aim at characterizing the occurrence of water maser emission in an unbiased sample of AGN, investigating the relation with the X-ray properties and the possible favorable geometry needed to detect water maser. We have searched for 22 GHz maser emission in a hard X-ray selected sample of AGN, taken from the INTEGRAL/IBIS survey above 20 keV. Of the 380 sources in the sample, only half have water maser data. We have also considered a sub-sample of 87 sources, volume limited, for which we obtained new Green Bank Telescope and Effelsberg observations (for 35 sources), detecting one new maser and increasing its radio coverage to 75%. The detection rate of water maser emission in the total sample is 15+/-3%, this fraction raises up to 19+/-5% for the complete sub-sample, especially if considering type 2 and Compton thick AGN. These results demonstrate that the hard X-ray selection may significantly enhance the maser detection efficiency over comparably large optical/infrared surveys. A possible decline of the detection fraction with increasing luminosity might suggest that an extreme luminous nuclear environment does not favour maser emission. The large fraction of CT AGN with water maser emission could be explained in terms of geometrical effects, being the maser medium the very edge-on portion of the obscuring medium.Comment: 21 pages, 3 figures. Accepted for publication in A&A June 202

The Influence of Teaching Approach on Students’ Conceptual Learning in Physics

Physics is fundamental to secure future needs for scientific and technological competence (Angell et al., 2004), but many countries experience a drop in students’ performances in international assessments (Organisation for Economic Co-operation Development [OECD], 2018), as well as in rates of enrolment in undergraduate programs in scientific disciplines (STEM). Socio-constructivist theories have produced a reforming movement in several educational systems, in particular in the area of sciences, but teacher often consider them an idealistic view of education and do not consider themselves metacognitively competent enough to foster thinking in the classroom. In this study, we investigated the efficacy of different teaching methods on high-school students’ conceptual knowledge of physics, after the effect of science-related beliefs and critical thinking skills was controlled. We adopted a mixed-method with sequential design, in which quantitative and qualitative data flow are inter-mixed. In specific, we interviewed four high school physics teachers to identify teaching approaches (qualitative approach) and compared them in terms of efficacy on students’ performances (quantitative approach). Four teachers and 77 10th grade students participated. Teachers were interviewed during the school years and asked questions about their teaching experience, their teaching approach (Kang and Wallace, 2005) and their epistemic beliefs (Tsai, 2002). Students performances in Science-related beliefs (Conley et al., 2004), critical thinking (Cornell Critical Thinking Test Level X, Millman et al., 2005), and conceptual knowledge in physics (The Force and Motion Conceptual Evaluation, Ramlo, 2002) were evaluated twice, at the beginning and at the end of the school year. The independent-sample t-tests on pre-test variables did not reveal any statistically significant difference between groups. Results from the complex samples GLM revealed statistically significant differences on post-test scores in conceptual knowledge in physics, after the effect of covariates was controlled. Overall, the study contributes to our understanding on current teaching practices in school, and their effect on students’ conceptual understanding of physics concepts

Predictive value of preoperative albumin-bilirubin score and other risk factors for short-term outcomes after open pancreatoduodenectomy

Background: Pancreatoduodenectomy represents a complex procedure involving extensive organ resection and multiple alimentary reconstructions. It is still associated with high morbidity, even in high-volume centres. Prediction tools including preoperative patient-related factors to preoperatively identify patients at high risk for postoperative complications could enable tailored perioperative management and improve patient outcomes. Aim: To evaluate the clinical significance of preoperative albumin-bilirubin score and other risk factors in relation to short-term postoperative outcomes in patients after open pancreatoduodenectomy. Methods: This retrospective study included all patients who underwent open pancreatic head resection (pylorus-preserving pancreatoduodenectomy or Whipple resection) for various pathologies during a five-year period (2017-2021) in a tertiary care setting at University Medical Centre Ljubljana, Slovenia and Cattinara Hospital, Trieste, Italy. Short-term postoperative outcomes, namely, postoperative complications, postoperative pancreatic fistula, reoperation, and mortality, were evaluated in association with albumin-bilirubin score and other risk factors. Multiple logistic regression models were built to identify risk factors associated with these short-term postoperative outcomes. Results: Data from 347 patients were collected. Postoperative complications, major postoperative complications, postoperative pancreatic fistula, reoperation, and mortality were observed in 52.7%, 22.2%, 23.9%, 21.3%, and 5.2% of patients, respectively. There was no statistically significant association between the albumin-bilirubin score and any of these short-term postoperative complications based on univariate analysis. When controlling for other predictor variables in a logistic regression model, soft pancreatic texture was statistically significantly associated with postoperative complications [odds ratio (OR): 2.09; 95% confidence interval (95%CI): 1.19-3.67]; male gender (OR: 2.12; 95%CI: 1.15-3.93), soft pancreatic texture (OR: 3.06; 95%CI: 1.56-5.97), and blood loss (OR: 1.07; 95%CI: 1.00-1.14) were statistically significantly associated with major postoperative complications; soft pancreatic texture was statistically significantly associated with the development of postoperative pancreatic fistula (OR: 5.11; 95%CI: 2.38-10.95); male gender (OR: 1.97; 95%CI: 1.01-3.83), soft pancreatic texture (OR: 2.95; 95%CI: 1.42-6.11), blood loss (OR: 1.08; 95%CI: 1.01-1.16), and resection due to duodenal carcinoma (OR: 6.58; 95%CI: 1.20-36.15) were statistically significantly associated with reoperation. Conclusion: The albumin-bilirubin score failed to predict short-term postoperative outcomes in patients undergoing pancreatoduodenectomy. However, other risk factors seem to influence postoperative outcomes, including male sex, soft pancreatic texture, blood loss, and resection due to duodenal carcinoma

A new jet/outflow maser in the nucleus of the Compton-thick AGN IRAS 15480-0344

Investigations of H2O maser galaxies at X-ray energies reveal that most harbor highly absorbed AGN. Possible correlations between the intrinsic X-ray luminosity and the properties of water maser emission have been suggested. With the aim of looking into these correlations on a more solid statistical basis, we have search for maser emission in a well-defined sample of Compton-thick AGN. Here we report the results of the survey, which yielded a surprisingly high maser detection rate, with a particular focus on the newly discovered luminous water maser in the lenticular (field) S0 galaxy IRAS 15480-0344. Recently, VLBI observations have been obtained to image the line and continuum emission in the nucleus of this galaxy. The radio continuum emission at VLBI scales is resolved into two compact components that are interpreted as jet knots. Based on the single-dish profile, the variability of the maser emission, and the position of the maser spots with respect to these continuum sources, we favor of a jet/outflow origin for the maser emission, consistent with similar cases found in other radio-quiet AGN. This scenario is consistent with the hypothesis of the presence of strong nuclear winds recently invoked to explain the main characteristics of field S0 galaxies

FPGA-based digital back-ends for the Sardinia Radio Telescope

The Sardinia Radio Telescope (SRT), located in San Basilio, about 35 km north of Cagliari, is the largest (64-m diameter) radio telescope in Italy. It is a general-purpose, fully-steerable radio telescope designed to operate in the 300 MHz - 116 GHz frequency range, which allows it to perform a wide variety of scientific studies. The advanced electronic digital platforms that are installed at SRT play a key role, in particular those based on FPGAs (Field Programmable Gate Array), both because of their processing capability and their reconfigurability. In this paper, we present an overview of the digital back-ends available at SRT, as well as the ones under development; it is important to underline that, for all of them, FPGAs are the beating heart

The 1.4-GHz radio properties of hard X-ray-selected AGN

We have analysed the NRAO Very Large Array Sky Survey and Sydney University Molonglo Sky Survey data at 1.4 GHz and 843 MHz for a well-defined complete sample of hard X-ray AGN observed by INTEGRAL. A large number (70/79) of sources are detected in the radio band, showing a wide range of radio morphologies, from unresolved or slightly resolved cores to extended emission over several hundreds of kpc scales. The radio fluxes have been correlated with the 2-10 keV and 20-100 keV emission, revealing significant correlations with slopes consistent with those expected for radiatively efficient accreting systems. The high-energy emission coming from the inner accretion regions correlates with the radio emission averaged over hundreds of kpc scales (i.e. thousands of years)

The spectral imaging facility: Setup characterization

The SPectral IMager (SPIM) facility is a laboratory visible infrared spectrometer developed to support space borne observations of rocky bodies of the solar system. Currently, this laboratory setup is used to support the DAWN mission, which is in its journey towards the asteroid 1-Ceres, and to support the 2018 Exo-Mars mission in the spectral investigation of the Martian subsurface. The main part of this setup is an imaging spectrometer that is a spare of the DAWN visible infrared spectrometer. The spectrometer has been assembled and calibrated at Selex ES and then installed in the facility developed at the INAF-IAPS laboratory in Rome. The goal of SPIM is to collect data to build spectral libraries for the interpretation of the space borne and in situ hyperspectral measurements of planetary materials. Given its very high spatial resolution combined with the imaging capability, this instrument can also help in the detailed study of minerals and rocks. In this paper, the instrument setup is first described, and then a series of test measurements, aimed to the characterization of the main subsystems, are reported. In particular, laboratory tests have been performed concerning (i) the radiation sources, (ii) the reference targets, and (iii) linearity of detector response; the instrumental imaging artifacts have also been investigated. <P /

The Sardinia Radio Telescope . From a technological project to a radio observatory

Context. The Sardinia Radio Telescope (SRT) is the new 64 m dish operated by the Italian National Institute for Astrophysics (INAF). Its active surface, comprised of 1008 separate aluminium panels supported by electromechanical actuators, will allow us to observe at frequencies of up to 116 GHz. At the moment, three receivers, one per focal position, have been installed and tested: a 7-beam K-band receiver, a mono-feed C-band receiver, and a coaxial dual-feed L/P band receiver. The SRT was officially opened in September 2013, upon completion of its technical commissioning phase. In this paper, we provide an overview of the main science drivers for the SRT, describe the main outcomes from the scientific commissioning of the telescope, and discuss a set of observations demonstrating the scientific capabilities of the SRT. Aims: The scientific commissioning phase, carried out in the 2012-2015 period, proceeded in stages following the implementation and/or fine-tuning of advanced subsystems such as the active surface, the derotator, new releases of the acquisition software, etc. One of the main objectives of scientific commissioning was the identification of deficiencies in the instrumentation and/or in the telescope subsystems for further optimization. As a result, the overall telescope performance has been significantly improved. Methods: As part of the scientific commissioning activities, different observing modes were tested and validated, and the first astronomical observations were carried out to demonstrate the science capabilities of the SRT. In addition, we developed astronomer-oriented software tools to support future observers on site. In the following, we refer to the overall scientific commissioning and software development activities as astronomical validation. Results: The astronomical validation activities were prioritized based on technical readiness and scientific impact. The highest priority was to make the SRT available for joint observations as part of European networks. As a result, the SRT started to participate (in shared-risk mode) in European VLBI Network (EVN) and Large European Array for Pulsars (LEAP) observing sessions in early 2014. The validation of single-dish operations for the suite of SRT first light receivers and backends continued in the following year, and was concluded with the first call for shared-risk early-science observations issued at the end of 2015. As discussed in the paper, the SRT capabilities were tested (and optimized when possible) for several different observing modes: imaging, spectroscopy, pulsar timing, and transients