The formation of galaxy disks in a hierarchical universe

The formation of galactic discs and the efficiency of star formation within them are issues central to our understanding of galaxy formation. We have developed a detailed and versatile model of disc formation which combines the strengths of previous studies of isolated discs with those of hierarchical galaxy formation models. Disc structure is inferred from the distribution of angular momentum in hot halo gas and the hierarchical build-up of dark matter, leading to theoretically generated systems where the evolution of surface density, rotation, velocity dispersion, stability and metallicity is predicted for annular regions of width 20-100 pc. The model will be used to establish whether the accepted theory of large-scale structure formation in the universe is consistent with observed trends in the properties of disc galaxies. This first paper explicitly examines the importance of embedding such calculations within a merging hierarchy of dark matter haloes, finding that this leads to dramatically different formation histories compared to models in which discs grow in isolation. Different models of star formation are explored, and are found to have only a secondary influence on the properties of the resulting galaxy discs, the main governing factor being the infalling gas supply from the hot halo.Comment: 13 pages, 9 figures, accepted by MNRA

Australian Consumers' Concerns and Preferences for Food Policy Alternatives

Results from a 2007 Australian consumer survey conducted at a large farmers market are used to explore the hypothesis that consumers who are more concerned about certain types of food labeling information, particularly information related to food production attributes, are more likely to support policies which help develop farmers markets and support mandatory labeling policies. Product information and attributes such as Country-of-Origin, No Growth Hormones Used, Free Range and Animals Treated Humanely and Environmentally-friendly appear to be very important to consumers. It appears that respondents want increased government involvement in developing consistent food labelling standards for these attributes and support mandatory food labelling policies, however, respondents are split between whether third-parties or the Australian government should oversee regulation of the program. Some respondents appear to view a mandatory labelling policy as a method to improve competitiveness and sustainability of small food producers who want to use labelling to differentiate themselves. Respondents also tended to support the government subsidizing the development of farmers markets. Respondents viewed FM as an opportunity to gain additional information or purchase foods that have credence attributes such as pesticide-free. Thus, policies supporting FM may help alleviate market failures related to asymmetric information and lack of choice.market failure, consumers, farmers markets, labelling, Agricultural and Food Policy,

Galaxy size trends as a consequence of cosmology

We show that recently documented trends in galaxy sizes with mass and redshift can be understood in terms of the influence of underlying cosmic evolution; a holistic view which is complimentary to interpretations involving the accumulation of discreet evolutionary processes acting on individual objects. Using standard cosmology theory, supported with results from the Millennium simulations, we derive expected size trends for collapsed cosmic structures, emphasising the important distinction between these trends and the assembly paths of individual regions. We then argue that the observed variation in the stellar mass content of these structures can be understood to first order in terms of natural limitations of cooling and feedback. But whilst these relative masses vary by orders of magnitude, galaxy and host radii have been found to correlate linearly. We explain how these two aspects will lead to galaxy sizes that closely follow observed trends and their evolution, comparing directly with the COSMOS and SDSS surveys. Thus we conclude that the observed minimum radius for galaxies, the evolving trend in size as a function of mass for intermediate systems, and the observed increase in the sizes of massive galaxies, may all be considered an emergent consequence of the cosmic expansion.Comment: 14 pages, 13 figures. Accepted by MNRA

Application of satellite remote-sensing data to land selection and management

A pilot project conducted to demonstrate the utility and economy of satellite data in preparing thematic maps of a wilderness area emphasizing those resources of greatest interest to the potential owner is described. Vegetation maps delineating potential commercial timber and maps of suggested mineral prospecting areas of seven scattered regions were prepared by interpretation of LANDSAT images, coupled with a limited amount of ground truth. Images acquired both in winter and summer seasons were registered to township maps and used in making interpretations of the areal extent of commercial timber potentials. The amount of snow cover visible through the forest canopies was found to be a useful indicator of timber potentials. Identification was made of characteristic topographic features which are typical of flood plain deposits or of the well developed trellis drainage patterns which can indicate the strike of structural grain of underlying Cretaceous sedimentary rocks. The presence of igneous and mixed igneous and metamorphic rocks were indicated by combinations of spectral differences and anomalous interruptions of local radial drainage patterns

Teachers observing classroom communication: An application of the Communicating Supporting Classroom Observation Tool for children aged 4-7 years

The nature of ‘Teacher talk’ is likely to have a considerable bearing on the child’s learning but measuring the communication environment in the classroom can present challenges. One tool which does this is the Communication Supporting Classroom Observation Tool (CSCOT). Initial use suggested that it was valid and reliably used by specialists (psychologists and speech and language therapists) and special educational needs coordinators (SENCOs). A key question is whether it can be used routinely by classroom teachers and whether results coincide with those in earlier studies. CSCOT observations were carried out by teachers in 33 schools (32 Reception classrooms, 25 in Year 1 and 25 in Year 2) in two local authorities in the North East of England and teachers were asked afterwards to reflect on their experiences using the tool. Scores were in line with those in earlier studies and were consistently higher on all dimensions for reception compared to Year 2, but there was no difference between other year groups. Results were mostly consistent with the original studies. Language learning environment was higher relative to both language learning opportunities and interactions across all years (which again did not differ). There was a moderate interaction between language learning environment where scores were significantly higher in the Reception group and lower in the Year 2 group. Teachers supported the use of the CSCOT in their feedback, suggesting that CSCOT was easy to use and useful in informing practice. The CSCOT clearly has utility as a starting point in auditing classroom communication. It allows teachers to compare between classrooms and year groups and potentially fosters collaboration between teachers and specialist practitioners who focus on communication such as speech and language therapists. Further work could link the observation tool into an intervention program co-constructed with teachers

Analytic and numerical realisations of a disk galaxy

Recent focus on the importance of cold, unshocked gas accretion in galaxy formation -- not explicitly included in semi-analytic studies -- motivates the following detailed comparison between two inherently different modelling techniques: direct hydrodynamical simulation and semi-analytic modelling. By analysing the physical assumptions built into the Gasoline simulation, formulae for the emergent behaviour are derived which allow immediate and accurate translation of these assumptions to the Galform semi-analytic model. The simulated halo merger history is then extracted and evolved using these equivalent equations, predicting a strikingly similar galactic system. This exercise demonstrates that it is the initial conditions and physical assumptions which are responsible for the predicted evolution, not the choice of modelling technique. On this level playing field, a previously published Galform model is applied (including additional physics such as chemical enrichment and feedback from active galactic nuclei) which leads to starkly different predictions.Comment: 15 pages, 15 figure