Detection of the buckminsterfullerene cation (C60+) in space

In the early 90s, C60+ was proposed as the carrier of two diffuse interstellar bands (DIBs) at 957.7 and 963.2 nm, but a firm identification still awaits gas-phase spectroscopic data. Neutral C60, on the other hand, was recently detected through its infrared emission bands in the interstellar medium and evolved stars. In this contribution, we present the detection of C60+ through its infrared vibrational bands in the NGC 7023 nebula, based on spectroscopic observations with the Spitzer space telescope, quantum chemistry calculation, and laboratory data from the literature. This detection supports the idea that C60+ could be a DIB carrier, and provides robust evidence that fullerenes exist in the gas-phase in the interstellar medium. Modeling efforts to design specific observations, combined with new gas-phase data, will be essential to confirm this proposal. A definitive attribution of the 957.7 and 963.2 nm DIBs to C60+ would represent a significant step forward in the field.Comment: To appear in "Proceedings of IAU 297 symposium on the Diffuse Interstellar Bands", eds. J. Cami and N. Cox (5 pages

The infrared signatures of very small grains in the Universe seen by JWST

The near- and mid-IR spectrum of many astronomical objects is dominated by emission bands due to UV-excited polycyclic aromatic hydrocarbons (PAH) and evaporating very small grains (eVSG). Previous studies with the ISO, Spitzer and AKARI space telescopes have shown that the spectral variations of these features are directly related to the local physical conditions that induce a photo-chemical evolution of the band carriers. Because of the limited sensitivity and spatial resolution, these studies have focused mainly on galactic star-forming regions. We discuss how the advent of JWST will allow to extend these studies to previously unresolved sources such as near-by galaxies, and how the analysis of the infrared signatures of PAHs and eVSGs can be used to determine their physical conditions and chemical composition.Comment: To appear in the Proceedings of the annual meeting of the French society of astronomy and astrophysics (SF2A 2015

Evaporating Very Small Grains as tracers of the UV radiation field in Photo-dissociation Regions

Context. In photo-dissociation regions (PDRs), Polycyclic Aromatic Hydrocarbons (PAHs) could be produced by evaporation of Very Small Grains (VSGs) by the impinging UV radiation field from a nearby star. Aims. We investigate quantitatively the transition zone between evaporating Very Small Grains (eVSGs) and PAHs in several PDRs. Methods. We study the relative contribution of PAHs and eVSGs to the mid-IR emission in a wide range of excitation conditions. We fit the observed mid-IR emission of PDRs by using a set of template band emission spectra of PAHs, eVSGs and gas lines. The fitting tool PAHTAT (PAH Toulouse Astronomical Templates) is made available to the community as an IDL routine. From the results of the fit, we derive the fraction of carbon f_eVSG locked in eVSGs and compare it to the intensity of the local UV radiation field. Results. We show a clear decrease of f_eVSG with increasing intensity of the local UV radiation field, which supports the scenario of photo-destruction of eVSGs. Conversely, this dependence can be used to quantify the intensity of the UV radiation field for different PDRs, including non resolved ones. Conclusions. PAHTAT can be used to trace the intensity of the local UV radiation field in regions where eVSGs evaporate, which correspond to relatively dense (nH = [100, 10^5 ] cm-3) and UV irradiated PDRs (G0 = [100, 5x10^4]) where H2 emits in rotational lines.Comment: 13 pages, 11 figures. Accepted for publication in A&A. Typos correcte

Interstellar C60+

Buckminsterfullerene (C60) was recently detected through its infrared emission bands in the interstellar medium (ISM), including in the proximity of massive stars, where physical conditions could favor the formation of the cationic form, C60+. In addition, C60+ was proposed as the carrier of two diffuse interstellar bands in the near-IR, although a firm identification still awaits for gas-phase spectroscopic data. We examined in details the Spitzer IRS spectra of the NGC 7023 reflection nebula, at a position close (7.5") to the illuminating B star HD 200775, and found four previously unreported bands at 6.4, 7.1, 8.2 and 10.5 \mu m in addition to the classical bands attributed to Polycylic Aromatic Hydrocarbons (PAHs) and neutral C60. These 4 bands are observed only in this region of the nebula, while C60 emission is still present slightly further away from the star, and PAH emission even further away. Based on this observation, on theoretical calculations we perform, and on laboratory studies, we attribute these bands to C60+. The detection of C60+ confirms the idea that large carbon molecules exist in the gas-phase in these environments. In addition, the relative variation of the C60, and C60+, band intensities constitutes a potentially powerful probe of the physical conditions in highly UV-irradiated regions.Comment: Accepted for publication in A&A, v2: minor corrections of typos and language and additional reference include

Random mixtures of polycyclic aromatic hydrocarbon spectra match interstellar infrared emission

The mid-infrared (IR; 5-15~$\mu$m) spectrum of a wide variety of astronomical objects exhibits a set of broad emission features at 6.2, 7.7, 8.6, 11.3 and 12.7 $\mu$m. About 30 years ago it was proposed that these signatures are due to emission from a family of UV heated nanometer-sized carbonaceous molecules known as polycyclic aromatic hydrocarbons (PAHs), causing them to be referred to as aromatic IR bands (AIBs). Today, the acceptance of the PAH model is far from settled, as the identification of a single PAH in space has not yet been successful and physically relevant theoretical models involving ``true'' PAH cross sections do not reproduce the AIBs in detail. In this paper, we use the NASA Ames PAH IR Spectroscopic Database, which contains over 500 quantum-computed spectra, in conjunction with a simple emission model, to show that the spectrum produced by any random mixture of at least 30 PAHs converges to the same 'kernel'-spectrum. This kernel-spectrum captures the essence of the PAH emission spectrum and is highly correlated with observations of AIBs, strongly supporting PAHs as their source. Also, the fact that a large number of molecules are required implies that spectroscopic signatures of the individual PAHs contributing to the AIBs spanning the visible, near-infrared, and far infrared spectral regions are weak, explaining why they have not yet been detected. An improved effort, joining laboratory, theoretical, and observational studies of the PAH emission process, will support the use of PAH features as a probe of physical and chemical conditions in the nearby and distant Universe

Mapping PAH sizes in NGC 7023 with SOFIA

NGC 7023 is a well-studied reflection nebula, which shows strong emission from polycyclic aromatic hydrocarbon (PAH) molecules in the form of aromatic infrared bands (AIBs). The spectral variations of the AIBs in this region are connected to the chemical evolution of the PAH molecules which, in turn, depends on the local physical conditions. We use the capabilities of SOFIA to observe a 3.2' x 3.4' region of NGC 7023 at wavelengths that we observe with high spatial resolution (2.7") at 3.3 and 11.2 um. We compare the SOFIA images with existing images of the PAH emission at 8.0 um (Spitzer), emission from evaporating very small grains (eVSG) extracted from Spitzer-IRS spectral cubes, the ERE (HST and CFHT), and H_2 (2.12 um). We create maps of the 11.2/3.3 um ratio to probe the morphology of the PAH size distribution and the 8.0/11.2 um ratio to probe the PAH ionization. We make use of an emission model and of vibrational spectra from the NASA Ames PAHdb to translate the 11.2/3.3 um ratio to PAH sizes. The 11.2/3.3 um map shows the smallest PAH concentrate on the PDR surface (H_2 and extended red emission) in the NW and South PDR. We estimated that PAHs in the NW PDR bear, on average, a number of carbon atoms (N_c) of ~70 in the PDR cavity and ~50 at the PDR surface. In the entire nebula, the results reveal a factor of 2 variation in the size of the PAH. We relate these size variations to several models for the evolution of the PAH families when they traverse from the molecular cloud to the PDR. The PAH size map enables us to follow the photochemical evolution of PAHs in NGC 7023. Small PAHs result from the photo-evaporation of VSGs as they reach the PDR surface. Inside the PDR cavity, the PAH abundance drops as the smallest PAH are broken down. The average PAH size increases in the cavity where only the largest species survive or are converted into C_60 by photochemical processing.Comment: accepted for publication in A&

Direct and indirect tourism online channels. Do they have a different potential for customer loyalty?

To manage their competitive goals, e-tourism service companies, in direct and in indirect channels respectively, need to know the antecedents of customer loyalty. Customer loyalty, generated by satisfaction in its various forms, is the cornerstone of the company''s assets and financial sustainability. Current literature does not provide a comparative analysis on this issue. To fill this gap, this research presents a model that includes customer satisfaction and participation as the main drivers of customer loyalty. The empirical research relies on one survey conducted by a market research company addressed to Internet users in Spain with experience in online purchases of tourism products. The estimation method is 3SLS (Three-Stage Least Squares), a simultaneous equations model applied to the database obtained. The results reveal a different potential of the two types of e-channels in producing higher levels of loyalty through customer participation. Increasing the participation of customers in indirect e-tourism channels results in higher returns on loyalty while the impact is lower in the direct channels. These findings are especially interesting for tourism service providers

Factores de desarrollo de las televisiones autonómicas públicas desde las percepciones de los grupos de interés: el caso de Aragón Televisión

La actual crisis económica, junto a los recientes cambios tecnológicos, legales y sociales producidos en la industria de la televisión, impulsa nuevos retos y oportunidades que deben ser abordados por todos los agentes que participan en la industria. Sin embargo, la literatura especializada carece de aportaciones que identifiquen grupos de interés y determinan la estructura de relaciones entre los mismos a través de puntos de interés común. Ante esta situación, el presente trabajo desarrolla una investigación cualitativa, con entrevistas en profundidad a expertos de la industria de la televisión autonómica pública de Aragón (cadena Aragón Televisión, ATV). Los resultados obtenidos permiten cubrir los objetivos del estudio descubriendo los factores de desarrollo a futuro de la industria audiovisual, en particular, para el caso de Aragón.The public television industry is confronting the current economic crisis and its financial problems related. This situation, joined to the technological, social and legal changes happening, derives in new challenges, which should be taken by every implied agent. However, the specialized literature falls in the identification of stakeholders and determining the relationships structure among them through common interest points. In this way, we develop a qualitative research, based on interviews to the experts, in the Aragon context (the study case of Aragon Television –ATV-, Spanish region). We use a qualitative methodology based on interviews to the experts of the audiovisual industry. Our results provide a better understanding of the audiovisual industry by identifying their stakeholders and the relationships between stakeholders and the regional public media. We obtain the development factors of this industry from stakeholders’ perceptions

The PAH hypothesis after 25 years

The infrared spectra of many galactic and extragalactic objects are dominated by emission features at 3.3, 6.2, 7.7, 8.6 and 11.2 \mu m. The carriers of these features remained a mystery for almost a decade, hence the bands were dubbed the unidentified infrared (UIR) bands. Since the mid-80's, the UIR bands are generally attributed to the IR fluorescence of Polycyclic Aromatic Hydrocarbon molecules (PAHs) upon absorption of UV photons -- the PAH hypothesis. Here we review the progress made over the past 25 years in understanding the UIR bands and their carriers.Comment: 13 pages, 7 figures. To appear in the proceedings of IAU symposium 280 "The Molecular Universe

Analysing cross-cutting competencies learning in an online entrepreneurship context

Research in teaching innovation encourages leveraging the evolution of digital technologies from using the device to learning with the device, which means a change from using information and communicational technologies to learning and knowledge technologies. Nevertheless, although the feasibility of implementing active and interactive methodologies to improve education is widely recognised, more research is needed to obtain evidence on the subjects and contents with the most significant potential for success. In addition, the most recent literature claims greater attention to the improvement of transversal skills, as they are critical in the student’s professional future. Thus, the main objective of this study is to contribute to the development of immersive learning aimed at improving the cross-cutting skills of university students. Developing a teaching activity where the student acts as an entrepreneur in electronic distribution channels faces the research question. The student-company-university collaboration is the basis for enhancing the transversal skills of the Degree in Marketing and Market Research at the University of Zaragoza (Spain). The student participates in each step of the program as an active agent. The teacher tutors the work teams in each process step, and the Palbin Company provides the necessary technical support. The students give the information to analyse the success of the experience through two surveys -pre and post-workshop, following the methodology used in previous literature. While the activity planning is complex, the students show an excellent mood during the experience. The comparison between expectations and performance offers significant success from the student’s point of view. As a result, the student improves cross-cutting competencies and gains confidence, satisfaction with their learning at university, and professional experience