A near-infrared and optical photometric study of the Sculptor dwarf spheroidal galaxy: implications for the metallicity spread

We present here a detailed study of the Sculptor dSph galaxy red giant branch (RGB) and horizontal branch (HB) morphology, combining new near-infrared photometry from CIRSI, with optical data from the ESO WFI. For a Sculptor-like old and generally metal-poor system, the position of RGB stars on the colour-magnitude diagram is mainly metallicity dependent. The advantage of using optical-NIR colours is that the position of the RGB locus is much more sensitive to metallicity than with optical colours alone. In contrast the horizontal branch (HB) morphology is strongly dependent on both metallicity and age. Therefore a detailed study of both the RGB in optical-NIR colours and the HB can help break the age-metallicity degeneracy. Our measured photometric width of the Sculptor giant branch corresponds to a range in metallicity of 0.75 dex. We detect the RGB and AGB bumps in both the NIR and optical luminosity functions, and derive from them a mean metallicity of [M/H] = -1.3 +/- 0.1. From isochrone fitting we derive a mean metallicity of [Fe/H] = -1.42 with a dispersion of 0.2 dex. These photometric estimators are for the first time consistent with individual metallicity measurements derived from spectroscopic observations. No spatial gradient is detected in the RGB morphology within a radius of 13 arcmin, twice the core radius. On the other hand, a significant gradient is observed in the HB morphology index, confirming the `second parameter problem' present in this galaxy. These observations are consistent with an early extended period of star formation continuing in time for a few Gyr. (Abridged)Comment: 9 pages, 10 figures. Accepted for publication in MNRA

Wall Street vs. Main Street: What are the Benefits and Costs of Wal-Mart to Local Communities?

Community/Rural/Urban Development, L81, R52, R58,

Sagittarius: The Nearest Dwarf Galaxy

We have discovered a new Galactic satellite galaxy in the constellation of Sagittarius. The Sagittarius dwarf galaxy is the nearest galaxy known, subtends an angle of $> 10$ degrees on the sky, lies at a distance of 24 \kpc from the Sun, \sim 16 \kpc from the centre of the Milky Way. Itis comparable in size and luminosity to the largest dwarf spheroidal, has a well populated red horizontal branch with a blue HB extension; a substantial carbon star population; and a strong intermediate age stellar component with evidence of a metallicity spread. Isodensity maps show it to be markedly elongated along a direction pointing towards the Galactic centre and suggest that it has been tidally distorted. The close proximity to the Galactic centre, the morphological appearance and the radial velocity of 140 km/s indicate that this system must have undergone at most very few close orbital encounters with the Milky Way. It is currently undergoing strong tidal disruption prior to being integrated into the Galaxy. Probably all of the four globular clusters, M54, Arp 2, Ter 7 and Ter 8, are associated with the Sagittarius dwarf galaxy, and will probably share the fate of their progenitor.Comment: MNRAS in press, 22pp uuencoded PS file, 26 printed figures available on request from [email protected]

HETEROGENEITY IN THE HINTERLAND: A TYPOLOGICAL ANALYSIS OF OHIO EXURBAN AREAS

Located between suburban and rural regions, exurban areas are among the fastest growing regions in the U.S. To better understand exurban changes and their policy implications, we develop a typology of rural-urban places and use statistical methods to examine township patterns of exurban change in Ohio.Community/Rural/Urban Development,

Generic advertising impacts on demands for orange juice in fifty Nielsen metropolitan regions

Agribusiness, Demand and Price Analysis,

Optimization of MLS receivers for multipath environments

Optimal design studies of MLS angle-receivers and a theoretical design-study of MLS DME-receivers are reported. The angle-receiver results include an integration of the scan data processor and tracking filter components of the optimal receiver into a unified structure. An extensive simulation study comparing the performance of the optimal and threshold receivers in a wide variety of representative dynamical interference environments was made. The optimal receiver was generally superior. A simulation of the performance of the threshold and delay-and-compare receivers in various signal environments was performed. An analysis of combined errors due to lateral reflections from vertical structures with small differential path delays, specular ground reflections with neglible differential path delays, and thermal noise in the receivers is provided

Incorporating Spatial Complexity into Economic Models of Land Markets and Land Use Change

Recent work in regional science, geography, and urban economics has advanced spatial modeling of land markets and land use by incorporating greater spatial complexity, including multiple sources of spatial heterogeneity, multiple spatial scales, and spatial dynamics. Doing so has required a move away from relying solely on analytical models to partial or full reliance on computational methods that can account for these added features of spatial complexity. In the first part of the paper, we review economic models of urban land development that have incorporated greater spatial complexity, focusing on spatial simulation models with spatial endogenous feedbacks and multiple sources of spatial heterogeneity. The second part of the paper presents a spatial simulation model of exurban land development using an auction model to represent household bidding that extends the traditional Capozza and Helsley (1990) model of urban growth to account for spatial dynamics in the form of local land use spillovers and spatially heterogeneous land characteristics.urban growth, urbanization, land development, spatial dynamics, heterogeneity, agent-based models, spatial interactions, Land Economics/Use, Research Methods/ Statistical Methods,

Using Regression Discontinuity Design to Identify the Effect of Zoning

We test the effect of minimum lot zoning on rural-to-urban land use conversion using Regression Discontinuity Design (RDD), a technique that exploits natural discontinuities in the data to identify causal effects. Observations are drawn from either size of a discontinuous minimum lot size zoning boundary. Using these selected sub-samples, a binary discrete choice model of residential land use change is estimated using parcel-level data and other spatially explicit data from an exurban county that lies on the fringes of Cleveland, Ohio. Results show that controlling for unobserved correlation in the data clearly identifies a negative and significant effect of larger minimum lot size zoning on the probability of conversion to a residential use.Land Economics/Use,

A Dynamic Model of Household Location, Regional Growth and Endogenous Natural Amenities with Cross-Scale Interactions

We develop a coupled model of regional migration and lake ecology to study the influence of ecological-economic interactions and relative time scales on transient and asymptotic dynamics. Cross-scale interactions fundamentally change system dynamics by eliminating steady states that are present in the decoupled economic model and introduce important time dependence. We find that the relative time scales of interacting variables are a key determinant in system dynamics and resilience and that the system's asymptotic behavior cannot be determined without considering the full dynamics of the system. Other time-dependent effects are found to matter, e.g., when households base their perceptions of environmental amenities on past observation, a path dependence is introduced that can lead to oscillations or decline in transient population. Finally, interactions are found to multiply the costs and benefits of policy by inducing a positive feedback between the ecological and economic components that can reinforce or offset the direct effect of the policy. Such effects imply that the economic and ecological costs of getting the policy wrong can be large. Our findings underscore the critical importance of accounting for multiple time scales and time dependence and suggest that models that ignore such complications can be quite misleading. At best, such models will fail to capture the full dynamics of the system and at worst, could provide a misleading characterization of the basic dynamical structure of these systems.Community/Rural/Urban Development, Resource /Energy Economics and Policy,