Source extraction and photometry for the far-infrared and sub-millimeter continuum in the presence of complex backgrounds

(Abridged) We present a new method for detecting and measuring compact sources in conditions of intense, and highly variable, fore/background. While all most commonly used packages carry out the source detection over the signal image, our proposed method builds from the measured image a "curvature" image by double-differentiation in four different directions. In this way point-like as well as resolved, yet relatively compact, objects are easily revealed while the slower varying fore/background is greatly diminished. Candidate sources are then identified by looking for pixels where the curvature exceeds, in absolute terms, a given threshold; the methodology easily allows us to pinpoint breakpoints in the source brightness profile and then derive reliable guesses for the sources extent. Identified peaks are fit with 2D elliptical Gaussians plus an underlying planar inclined plateau, with mild constraints on size and orientation. Mutually contaminating sources are fit with multiple Gaussians simultaneously using flexible constraints. We ran our method on simulated large-scale fields with 1000 sources of different peak flux overlaid on a realistic realization of diffuse background. We find detection rates in excess of 90% for sources with peak fluxes above the 3-sigma signal noise limit; for about 80% of the sources the recovered peak fluxes are within 30% of their input values.Comment: Accepted on A&

Credit Merchandising in the Postbellum American South: Information and Barriers to Entry

Roger Ransom and Richard Sutch's research on the social and institutional changes in the postbellum American South, summarized in their One Kind of Freedom, raised many controversies. One of them concerns the degree of competition among the advancing merchants of the rural South. Ransom and Sutch's assertion that such merchants held a 'territorial monopoly'' is usually criticized as being at odds with the high level of postbellum entry in the rural merchandising sector and the absence of significant costs to entry. The question is still open, as shown by a recent special issue of Explorations in Economic History. This paper offers a contribution to this controversy by showing that high level of entry in the market and excessively high prices need not to be in conflict. In particular, using the theory of incomplete information games to study the competition between an advancing merchant and a potential entrant, the practice of over-pricing is shown to be an equilibrium behavior if interpreted as a way of signaling information about the market riskiness.credit merchandising, asymmetric information

Electromagnetic design search and optimisation of photonic bandgap devices on distributed computational resources

Photonic crystals are devices with periodically modulated dielectric constant, designed to exhibit band gaps in a frequency spectrum in which electromagnetic waves cannot propagate. Tuning the properties of these structures to achieve precise band gaps before fabrication is of high interest to photonic crystal manufacturers. In this paper, we present the process of finding and optimising a photonic crystal design using a high-throughput Condor-based compute cluster and transparent database technology for easy storage, retrieval and reuse of the created designs. We also demonstrate how a band gap diagram can easily be obtained on a compute cluster when using the developed user interface technology. The optimisation process can easily be adapted to other problem area

Microsoft institute for high performance computing

An overview of the Microsoft Institute for High Performance Computing at the University of Southampto

Proof-of-concept engineering workflow demonstrator

When Microsoft needed a proof-of-concept implementation of bespoke engineering workflow software for their customer, BAE Systems, it called on the software engineering skills and experience of the Microsoft Institute for High Performance Computing. BAE Systems was looking into converting their in-house SOLAR software suite to run on the MS Compute Cluster Server product with 64-bit MPI support in conjunction with an extended Windows Workflow environment for use by their engineer

Universality of the Tearing Phase in Matrix Models

The spontaneous symmetry breaking associated to the tearing of a random surface, where large dynamical holes fill the surface, was recently analized obtaining a non-universal critical exponent on a border phase. Here the issue of universality is explained by an independent analysis. The one hole sector of the model is useful to manifest the origin of the (limited) non-universal behaviour, that is the existence of two inequivalent critical points.Comment: 9 pages, 1 figure non include