32 research outputs found
A measurement of the millimetre emission and the Sunyaev-Zel'dovich effect associated with low-frequency radio sources
We present a statistical analysis of the millimetre-wavelength properties of 1.4GHz-selected sources and a detection of the Sunyaev–Zel’dovich (SZ) effect associated with the haloes that host them. We stack data at 148, 218 and 277GHz from the Atacama Cosmology Telescope at the positions of a large sample of radio AGN selected at 1.4GHz. The thermal SZ effect associated with the haloes that host the AGN is detected at the 5σ level through its spectral signature, representing a statistical detection of the SZ effect in some of the lowest mass haloes (average M 200 ≈ 10 13 M. h −1 70 ) studied to date. The relation between the SZ effect and mass (based on weak lensing measurements of radio galaxies) is consistent with that measured by Planck for local bright galaxies. In the context of galaxy evolution models, this study confirms that galaxies with radio AGN also typically support hot gaseous haloes. Adding Herschel observations allows us to show that the SZ signal is not significantly contaminated by dust emission. Finally, we analyse the contribution of radio sources to the angular power spectrum of the cosmic microwave background
The environment of radio galaxies: a signature of AGN feedback at high redshifts
We use the semi-analytical model of galaxy formation GALFORM to characterize an indirect signature of active galactic nucleus (AGN) feedback in the environment of radio galaxies at high redshifts. The predicted environment of radio galaxies is denser than that of radio-quiet galaxies with the same stellar mass. This is consistent with observational results from the CARLA survey. Our model shows that the differences in environment are due to radio galaxies being hosted by dark matter haloes that are ∼1.5 dex more massive than those hosting radio-quiet galaxies with the same stellar mass. By running a control simulation in which AGN feedback is switched off, we identify AGN feedback as the primary mechanism affecting the build up of the stellar component of radio galaxies, thus explaining the different environment in radio galaxies and their radio-quiet counterparts. The difference in host halo mass between radio-loud and radio-quiet galaxies translates into different galaxies populating each environment. We predict a higher fraction of passive galaxies around radio-loud galaxies compared to their radio-quiet counterparts. Furthermore, such a high fraction of passive galaxies shapes the predicted infrared luminosity function in the environment of radio galaxies in a way that is consistent with observational findings. Our results suggest that the impact of AGN feedback at high redshifts and environmental mechanisms affecting galaxies in high halo masses can be revealed by studying the environment of radio galaxies, thus providing new constraints on galaxy formation physics at high redshifts
Claiming Rights Warily
Abstract Planners concerned with cultivating the moral capacity of local communities should be wary of claiming rights that stem from deontological principles or from the norms of superordinate associations
Ethics in planning, edited by Martin Wachs. New Brunswick, NJ: State University of New Jersey Press, 1985, 372 pp. Price: $14.95 paper
Cities and communication : The limits of community
The synthetic idea of an urban communication infrastructure and policy agenda has not entered deeply into political discussions or practice in the USA. It has been blocked by a reluctance to treat cities as deep communities of mutual obligation. This article discusses the role of communication as part of the technical infrastructure of urban life.
Explorations d'une histoire imaginaire. Villes et communication
Explorations in an imaginary history. Cities and communication.
Not until recently have city decision makers been asked to imagine an urban communication infrastructure as an object of design and policy.
This paper explores the implication of the historical absence of this idea in the United States and assesses the uses, limitations, and difficulties of embedding of communication components within the broader concept of an urban infrastructure.C'est tout récemment qu'on a demandé aux édiles d'imaginer une infrastructure de communication urbaine comme un objet relevant à la fois de l'esthétique et de la politique.
Cette étude s'efforce de trouver les raisons pour lesquelles, aux Etats-Unis, une telle conception a toujours été historiquement absente. Elle évalue les usages, les limites, les difficultés qu'on peut éprouver à inclure les différents composants de la communication à l'intérieur d'un concept plus vaste, celui d'infrastructure urbaine.Exploraciónes de una historia imaginaria. Las ciudades y la comunicación.
Es muy reciente haber pedido a los ediles, imaginar una infraestructura de comunicación urbana como un objeto que comprende al mismo tiempo lo estético y la político.
Este estudio se esfuerza por descubrir las razones por las cuales, en los Estados Unidos, tal concepción ha estado históricamente ausente. Evalúa los usos, los límites y las dificultades que se pueden experimentar, incluyendo los diferentes componentes de la comunicación dentro de un concepto más vasto, el de infraestructura urbana.Mandelbaum Seymour J., Loyer Béatrice. Explorations d'une histoire imaginaire. Villes et communication. In: Les Annales de la recherche urbaine, N°23-24, 1984. Les réseaux techniques urbains. pp. 170-178