1,721,054 research outputs found
Accretion and ejection at work in the Narrow Line Seyfert 1 galaxy 1H 0323+342: A case of intermittent activity?
Full text linkContext. We present a comprehensive investigation into the properties of 1H 0323+342, a prominent jetted narrow-line Seyfert 1 galaxy. Aims. The primary objective is to understand the interplay between the relativistic jet, the hot corona, and the accretion disk around the supermassive black hole. Methods. This study spans the years 2006 to 2023, incorporating a rich dataset with 172 Swift observations, including the optical, UV, and X-ray bands, integrated with Fermi Large Area Telescope (LAT) observations. Spectral analysis was conducted on the X-ray observations using the XSPEC software, and the results were compared with optical, UV, and gamma-ray flux measurements and photon index values. Results. Our key findings include the identification of three distinct zones in the X-ray photon index-flux plot, characterized by high flux and a hard photon index (zone 1), high flux and a soft photon index (zone 2), and low flux and a soft photon index (zone 3). Before similar to 2017, 1H 0323 + 342 moved back and forth between zones 1 and 2; after that epoch, it transitioned to zones 2 and 3. Correspondingly, we observed a decreasing jet activity in the Fermi/LAT data and a reduction in the accretion rate in optical/UV data from Swift/UVOT. Conclusions. We interpret these observations in the framework of an intermittent jet scenario, driven by radiation-pressure instability in the accretion disk
Teaching physics through astronomy in secondary school: the Asiago Teachers' Network on Astrophysics
Full text linkWe present the development and outcomes of the ATENA - Asiago Teachers' Network on Astrophysics project. The initiative encompassed a professional development program and learning community for physics teachers, grounded in authentic collaboration and action research. The group's collective inquiry centred on the integration of Astronomy into the secondary school curriculum, with the goal of fostering a comprehensive understanding of the physics of the Universe. Four physics topics spanning various grades were selected, and teaching-learning sequences informed by Physics and Astronomy Education Research were collaboratively developed by participants. Here, we present the development of the professional development program and highlight the main elements of three out of the four teaching-learning sequences. These results aim to support physics educators in incorporating astronomy into their physics teaching
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
A host galaxy study of southern narrow-line Seyfert 1 galaxies
Full text linkWe studied seven nearby narrow-line Seyfert 1 (NLS1) galaxies in J and Ks bands with redshifts varying from 0.019 to 0.092. This is the first multi-source study targeting the hosts of southern NLS1 galaxies. Our data were obtained with the FourStar instrument of the 6.5 m Magellan Baade telescope at the Las Campanas Observatory (Chile). The aim of our study is to determine the host galaxy morphologies of these sources by using GALFIT. We were able to model six out of the seven sources reliably. Our conclusion is that all of the reliably modelled sources are disk-like galaxies, either spirals or lenticulars. None of these sources present an elliptical morphology. Our findings are in agreement with the hypothesis that disk-like galaxies are the main host of jetted NLS1 galaxies. Taking advantage of observations in two bands, we also produced a J − Ks colour map of each source. Five of the six colour maps show significant dust extinction near the core of the galaxy - a feature often seen in gamma-ray-detected jetted NLS1 galaxies, and interpreted to be a consequence of a past minor merger
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Jetted narrow-line Seyfert 1 galaxies breaking the jet paradigm: A comprehensive study of host-galaxy morphologies
Full text linkNarrow-line Seyfert 1 (NLS1) galaxies are unevolved active galactic nuclei (AGNs) that exist predominantly in spiral galaxies. However, mostly due to the small number of sources studied, it has been under debate whether also the hosts of jetted NLS1 galaxies, a particular subclass of these sources hosting a relativistic jet, are disk-like or elliptical, as the hosts of more powerful jetted AGNs. We studied the host morphologies of 14 NLS1 galaxies, 11 of which have been detected at 37 GHz, indicating that these sources harbour relativistic jets. The J- and Ks-band data used in this study were obtained with the Nordic Optical Telescope (NOT). We performed the photometric decomposition of the host galaxy using the band that gave a better fit and additionally created colour maps of all sources that had both a J- and a Ks-band observation. We were able to successfully model 12 sources, nine of which most likely have disk-like morphologies. Of the remaining sources, one source could possibly be hosted either in a disk-like or a dwarf galaxy, and in two cases the results are inconclusive. Only one of our sources shows clear signs of interaction, but the colour maps of most of our sources hint at ample dust in the nuclei, possibly indicating earlier minor mergers, which can go unnoticed due to the limited resolution of these observations. Our results further support disk-like galaxies as the predominant host type of jetted NLS1 galaxies. Most importantly, with the number of modelled hosts of jetted NLS1s now exceeding 50, with only a few elliptical hosts, it seems to be safe to conclude that also disk-like galaxies are able to launch and maintain relativistic jets, and that the traditional jet paradigm stating that only massive elliptical galaxies are capable of hosting relativistic jets is severely outdated
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