The dust masses of powerful radio galaxies: clues to the triggering of their activity

We use deep Herschel Space Observatory observations of a 90% complete sample of 32 intermediate-redshift 2Jy radio galaxies (0.05 < z < 0.7) to estimate the dust masses of their host galaxies and thereby investigate the triggering mechanisms for their quasar-like AGN. The dust masses derived for the radio galaxies (7.2x10^5 < M_d < 2.6x10^8 M_sun) are intermediate between those of quiescent elliptical galaxies on the one hand, and ultra luminous infrared galaxies (ULIRGs) on the other. Consistent with simple models for the co-evolution of supermassive black holes and their host galaxies, these results suggest that most of the radio galaxies represent the late time re-triggering of AGN activity via mergers between the host giant elliptical galaxies and companion galaxies with relatively low gas masses. However, a minority of the radio galaxies in our sample (~20%) have high, ULIRG-like dust masses, along with evidence for prodigious star formation activity. The latter objects are more likely to have been triggered in major, gas-rich mergers that represent a rapid growth phase for both their host galaxies and their supermassive black holes.Comment: 5 pages, 2 figures, accepted for publication in MNRAS Letter

Cities, systems and structures: an ontological approach to urban studies

Ontological issues lie at the heart of the epistemological, methodological and theoretical discussions over the workings and operations of cities – however, as Castells and Zukin point out, they often find themselves mired in the midst of the praxis of urban studies, for reasons not entirely clear. In this work we attempt to trace a path through the ontology of urban studies, attempting to show the reasons for this apparent omission, as well as showing a possible line of convergence through the lens of systems theory, for a common ontology. We propose a set of analytical classes drawn from the literature, drawn from the need to discuss social phenomena, tracing some of the ontological compromises made in light of such entities. In line with that, we argue there is a need for a transparent phenomenological epistemology, tracing some methodological implications of such processes. We conclude by drawing some scientific and practical implications of these debates for a more general discussion of ontology in urban studies and research

From heritage interpretation to cultural systems: outline of an urban semiotics of culture

Urban and social realities have always been marked by researchers as "complex" and on the edge of chaos, with phenomena involving hundreds of thousands of different processes converging towards the dynamics of city life. However, attempts to harness this complexity into the very lines of study have remained relatively modest, with researchers opting for relatively linear explanations, or failing to integrate their findings into theoretical considerations into dynamical models. In this study we focus on the meanings of heritage, their evolution and distribution throughout individuals who experience it, in the city of Tomar, Portugal, as mediated by the presence of specialized information that can be thought of as “imposing” a certain view of the location. We use this as a starting point for multiple lines of inquiry: how to estimate the impact of elements such as information on cultural systems; how to conceptualize the ontology of urban reality with its differential agents and their respective teleologies; how to attempt to visualize different theoretical explanations for such motions with the help of Agent Based Modelling, and possible analytical considerations taken from these models. The study aims to provide theoretical and empirical guidelines for policy-making in the context, with a view to integrate semiotic concerns into the design and management of cities, as well as developing an academic research program articulated by middle-range systems theory.info:eu-repo/semantics/publishedVersio

Signs of heritage - an agent-based model of the dynamics of heritage categories

In recent times, heritage has become a key focus of socio-economic concern due to its connections to history, nationalism and especially tourism. It has been highlighted as having major consequences for the sociocultural engagement of local populations. The notion that tourism transforms local heritage through its categorising of local realities has become particularly widespread. However, the specific mechanism through which these transformations occur has remained unformalised in cultural heritage studies. This has lead to a lack of computational approaches to the issue of heritage categorization, which can articulate with other issues of tourism promotion and management. In this paper we conceptualise the cultural dynamics of heritage, such as the changes in categories used to signify heritage, designing and analysing a dedicated computational Agent-Based Model of heritage engagement. In it we seek to explore the role of communicative strategies, as they tie to social groups, as well as the specific topologies of interaction networks. With this, we seek to understand what role mediation, such as that produced by online platforms, can play in producing different levels of consensus between tourists. Results suggest that topology plays the greatest role in generating consensus in the evolution of heritage meaning, with different patterns emerging according to the communicative strategies undertaken. These results have implications for future directions of study of heritage and heritage modelling, placing emphasis on the need to analyse tourist communication contents, as well as being potentially useful for public policy on heritage management.info:eu-repo/semantics/acceptedVersio