Detection of (15)NNH+ in L1544: non-LTE modelling of dyazenilium hyperfine line emission and accurate (14)N/(15)N values

Samples of pristine Solar System material found in meteorites and interplanetary dust particles are highly enriched in (15)N. Conspicuous nitrogen isotopic anomalies have also been measured in comets, and the (14)N/(15)N abundance ratio of the Earth is itself larger than the recognised pre-solar value by almost a factor of two. Ion--molecules, low-temperature chemical reactions in the proto-solar nebula have been repeatedly indicated as responsible for these (15)N-enhancements. We have searched for (15)N variants of the N2H+ ion in L1544, a prototypical starless cloud core which is one of the best candidate sources for detection owing to its low central core temperature and high CO depletion. The goal is the evaluation of accurate and reliable (14)N/(15)N ratio values for this species in the interstellar gas. A deep integration of the (15)NNH+ (1-0) line at 90.4 GHz has been obtained with the IRAM 30 m telescope. Non-LTE radiative transfer modelling has been performed on the J=1-0 emissions of the parent and (15)N-containing dyazenilium ions, using a Bonnor--Ebert sphere as a model for the source. A high-quality fit of the N2H+ (1--0) hyperfine spectrum has allowed us to derive a revised value of the N2H+ column density in L1544. Analysis of the observed N(15)NH+ and (15)NNH+ spectra yielded an abundance ratio N[N(15)NH+]/N[(15)NNH+] = 1.1 +/- 0.3. The obtained (14)N/(15)N ratio is ~ 1000 +/- 200, suggestive of a sizeable (15)N depletion in this molecular ion. Such a result is not consistent with the prediction of present nitrogen chemical models. As chemical models predict large (15)N fractionation of N2H+, we suggest that (15)N(14)N, or (15)N in some other molecular form, is preferentially depleted onto dust grains.Comment: 12 pages, 9 figures, manuscript accepted in A&

What is in a radio loud NLS1?

A fraction of Narrow Line Seyfert 1 galaxies (NLS1) are hosted by galaxies that present a disturbed morphology, in some cases hinting for merger processes, that are putative sources of gas replenishment. We have been investigating the poorly studied population of radio loud NLS1 (RL-NLS1) showing a flat radio spectrum, assumed to be the manifestation of the presence of a radio jet. In some of the objects the infrared emission is well fitted by a combination of an AGN component and an "active" host galaxy component like M82, the estimate SFR being in the LIRG/ULIRG range (10-500 Msun/year). In order to better characterize that component, we have been investigating the sub-millimeter/millimeter emission of the sources using APEX. Here we present the results concerning a pilot sample of 2 representative objects.Comment: 5 pages, published on Proceedings of Science - volume "Revisiting narrow-line Seyfert 1 galaxies and their place in the Universe

Lucia Marcucci e la poesia visiva: pratica artistica e critica

Questa tesi ha lo scopo di analizzare la personalità e l’opera di Lucia Marcucci, artista fiorentina nata nel 1933 e tutt’oggi ancora in attività. Il nome della Marcucci viene giustamente associato a quello della poesia visiva e in particolare al Gruppo 70, primo nucleo costitutivo della stessa, formatosi a Firenze nel 1963. L’esperienza di gruppo, sommando i cinque anni di sopravvivenza del Gruppo 70 e i due del successivo Gruppo dei Nove, nato nel 1971 e di impianto internazionale, occupò tuttavia meno di un decennio, per quanto ricco di avvenimenti, del lungo percorso artistico della Marcucci. In questa tesi ho dunque cercato di ricostruire l’intera attività dell’artista: le sue importanti teorizzazioni, il ruolo da lei avuto in eventi o azioni collettive e, in particolare, le sue sperimentazioni personali, condotte indipendentemente dall’esperienza di gruppo. A grandi linee, tali obiettivi corrispondono ai tre capitoli in cui ho diviso il lavoro: nel primo capitolo ho analizzato le principali caratteristiche della poesia visiva, rivolgendo particolare attenzione alle interessanti posizioni della Marcucci, in aggiunta a quelle dei suoi colleghi. Il secondo capitolo, che ricostruisce le varie fasi dell’esperienza giovanile e di gruppo dell’artista, ha invece un’impostazione biografica e più propriamente cronologica. Infine, nel terzo capitolo, ho analizzato l’evoluzione linguistica dell’artista, intendendo con questo termine i differenti mezzi e le differenti “forme” alle quali la Marcucci ha, di volta in volta, affidato il suo messaggio contestatario, provocatorio e ironico, comunque libero da dogmi predefiniti. Per la mia ricerca ha assunto particolare importanza il materiale, in parte inedito, raccolto nell’archivio della Marcucci, catalogato e riorganizzato dal collezionista Carlo Palli e da lui attualmente conservato

First measurements of 15N fractionation in N2H+ toward high-mass star forming cores

We report on the first measurements of the isotopic ratio 14N/15N in N2H+ toward a statistically significant sample of high-mass star forming cores. The sources belong to the three main evolutionary categories of the high-mass star formation process: high-mass starless cores, high-mass protostellar objects, and ultracompact HII regions. Simultaneous measurements of 14N/15N in CN have been made. The 14N/15N ratios derived from N2H+ show a large spread (from ~180 up to ~1300), while those derived from CN are in between the value measured in the terrestrial atmosphere (~270) and that of the proto-Solar nebula (~440) for the large majority of the sources within the errors. However, this different spread might be due to the fact that the sources detected in the N2H+ isotopologues are more than those detected in the CN ones. The 14N/15N ratio does not change significantly with the source evolutionary stage, which indicates that time seems to be irrelevant for the fractionation of nitrogen. We also find a possible anticorrelation between the 14N/15N (as derived from N2H+) and the H/D isotopic ratios. This suggests that 15N enrichment could not be linked to the parameters that cause D enrichment, in agreement with the prediction by recent chemical models. These models, however, are not able to reproduce the observed large spread in 14N/15N, pointing out that some important routes of nitrogen fractionation could be still missing in the models.Comment: 2 Figures, accepted for publication in ApJ

The observed chemical structure of L1544

Prior to star formation, pre-stellar cores accumulate matter towards the centre. As a consequence, their central density increases while the temperature decreases. Understanding the evolution of the chemistry and physics in this early phase is crucial to study the processes governing the formation of a star. We aim at studying the chemical differentiation of a prototypical pre-stellar core, L1544, by detailed molecular maps. In contrast with single pointing observations, we performed a deep study on the dependencies of chemistry on physical and external conditions. We present the emission maps of 39 different molecular transitions belonging to 22 different molecules in the central 6.25 arcmin$^2$ of L1544. We classified our sample in five families, depending on the location of their emission peaks within the core. Furthermore, to systematically study the correlations among different molecules, we have performed the principal component analysis (PCA) on the integrated emission maps. The PCA allows us to reduce the amount of variables in our dataset. Finally, we compare the maps of the first three principal components with the H$_2$ column density map, and the T$_{dust}$ map of the core. The results of our qualitative analysis is the classification of the molecules in our dataset in the following groups: (i) the $c$-C$_3$H$_2$ family (carbon chain molecules), (ii) the dust peak family (nitrogen-bearing species), (iii) the methanol peak family (oxygen-bearing molecules), (iv) the HNCO peak family (HNCO, propyne and its deuterated isotopologues). Only HC$^{18}$O$^+$ and $^{13}$CS do not belong to any of the above mentioned groups. The principal component maps allow us to confirm the (anti-)correlations among different families that were described in a first qualitative analysis, but also points out the correlation that could not be inferred before.Comment: 29 pages, 19 figures, 2 appendices, accepted for publication in A&A, arXiv abstract has been slightly modifie

O2 signature in thin and thick O2-H2O ices

Aims. In this paper we investigate the detectability of the molecular oxygen in icy dust grain mantles towards astronomical objects. Methods. We present a systematic set of experiments with O2-H2O ice mixtures designed to disentangle how the molecular ratio affects the O2 signature in the mid- and near-infrared spectral regions. All the experiments were conducted in a closed-cycle helium cryostat coupled to a Fourier transform infrared spectrometer. The ice mixtures comprise varying thicknesses from 8 $\times$ 10$^{-3}$ to 3 $\mu$m. The absorption spectra of the O2-H2O mixtures are also compared to the one of pure water. In addition, the possibility to detect the O2 in icy bodies and in the interstellar medium is discussed. Results. We are able to see the O2 feature at 1551 cm$^{-1}$ even for the most diluted mixture of H2O : O2 = 9 : 1, comparable to a ratio of O2/H2O = 10 % which has already been detected in situ in the coma of the comet 67P/Churyumov-Gerasimenko. We provide an estimate for the detection of O2 with the future mission of the James Webb Space Telescope (JWST).Comment: 11 pages, 10 figures, article in press, to appear in A&A 201

Close Reading Oblivion: Character Believability and Intelligent Personalization in Games

This paper investigates issues of character believability and intelligent personalization through a reading of the Elder Scrolls: Oblivion. Oblivion’s opening sequence simultaneously trains players in the function of the game, and allows them to customize their character class through the choices and actions they take. Oblivion makes an ambitious attempt at intelligent personalization in the character creation process. Its strategy is to track early gameplay decisions and “stereotype” players into one of 21 possible classes. This approach has two advantages over a less adaptive system. First, it supports the illusion of the game world as a real world by embedding the process of character creation within a narrativised game-play context. Second, the intelligent recommendation system responds to the player’s desire to believe that the game “knows” something about her personality. This leads the players to conceptualize the system as an entity with autonomous, humanlike knowledge. Through the analysis of multiple replayings of the opening sequence, this paper considers ways in which Oblivion both succeeds and fails at mapping player behaviour to appropriate class assignments. The paper documents places where the dialogue between player and game breaks down, and argues for alternative techniques to customize the play experience within the desires of the player

Editorial: Exploring the Chemical Universe

Editorial on the Research Topi

Time and Space in Digital Game Storytelling

The design and representation of time and space are important in any narrative form. Not surprisingly there is an extensive literature on specific considerations of space or time in game design. However, there is less attention to more systematic analyses that examine both of these key factors—including their dynamic interrelationship within game storytelling. This paper adapts critical frameworks of narrative space and narrative time drawn from other media and demonstrates their application in the understanding of game narratives. In order to do this we incorporate fundamental concepts from the field of game studies to build a game-specific framework for analyzing the design of narrative time and narrative space. The paper applies this framework against a case analysis in order to demonstrate its operation and utility. This process grounds the understanding of game narrative space and narrative time in broader traditions of narrative discourse and analysis