Soft clustering analysis of galaxy morphologies: A worked example with SDSS

Context: The huge and still rapidly growing amount of galaxies in modern sky surveys raises the need of an automated and objective classification method. Unsupervised learning algorithms are of particular interest, since they discover classes automatically. Aims: We briefly discuss the pitfalls of oversimplified classification methods and outline an alternative approach called "clustering analysis". Methods: We categorise different classification methods according to their capabilities. Based on this categorisation, we present a probabilistic classification algorithm that automatically detects the optimal classes preferred by the data. We explore the reliability of this algorithm in systematic tests. Using a small sample of bright galaxies from the SDSS, we demonstrate the performance of this algorithm in practice. We are able to disentangle the problems of classification and parametrisation of galaxy morphologies in this case. Results: We give physical arguments that a probabilistic classification scheme is necessary. The algorithm we present produces reasonable morphological classes and object-to-class assignments without any prior assumptions. Conclusions: There are sophisticated automated classification algorithms that meet all necessary requirements, but a lot of work is still needed on the interpretation of the results.Comment: 18 pages, 19 figures, 2 tables, submitted to A

Deconvolution with Shapelets

We seek to find a shapelet-based scheme for deconvolving galaxy images from the PSF which leads to unbiased shear measurements. Based on the analytic formulation of convolution in shapelet space, we construct a procedure to recover the unconvolved shapelet coefficients under the assumption that the PSF is perfectly known. Using specific simulations, we test this approach and compare it to other published approaches. We show that convolution in shapelet space leads to a shapelet model of order $n_{max}^h = n_{max}^g + n_{max}^f$ with $n_{max}^f$ and $n_{max}^g$ being the maximum orders of the intrinsic galaxy and the PSF models, respectively. Deconvolution is hence a transformation which maps a certain number of convolved coefficients onto a generally smaller number of deconvolved coefficients. By inferring the latter number from data, we construct the maximum-likelihood solution for this transformation and obtain unbiased shear estimates with a remarkable amount of noise reduction compared to established approaches. This finding is particularly valid for complicated PSF models and low $S/N$ images, which renders our approach suitable for typical weak-lensing conditions.Comment: 9 pages, 9 figures, submitted to A&

The Data Processing Pipeline for the Herschel-HIFI Instrument

The HIFI data processing pipeline was developed to systematically process diagnostic, calibration and astronomical observations taken with the HIFI science instrumentas part of the Herschel mission. The HIFI pipeline processed data from all HIFI observing modes within the Herschel automated processing environment, as well as, within an interactive environment. A common software framework was developed to best support the use cases required by the instrument teams and by the general astronomers. The HIFI pipeline was built on top of that and was designed with a high degree of modularity. This modular design provided the necessary flexibility and extensibility to deal with the complexity of batch-processing eighteen different observing modes, to support the astronomers in the interactive analysis and to cope with adjustments necessary to improve the pipeline and the quality of the end-products. This approach to the software development and data processing effort was arrived at by coalescing the lessons learned from similar research based projects with the understanding that a degree of foresight was required given the overall length of the project. In this article, both the successes and challenges of the HIFI software development process are presented. To support future similar projects and retain experience gained lessons learned are extracted.Comment: 18 pages, 5 figure

Preliminary vegetation map of the Espenberg Peninsula, Alaska, based on an Earth Resources Technology Satellite image

There are no author-identified significant results in this report

The moral terrains of ecotourism and the ethics of consumption

In this chapter, we provide a brief overview of Western philosophical ethics as they may peliain to tourism. Our discussion then turns to one of the most popular attempts to address sustainability across the globe: ecotourism. Ecotourism as distinct from tourism writ large is earmarked by appeals to concepts and ethical practices peliaining to sustainability (in all its varied meanings), consumption, preservation, and the politics of colonialism and the dynamics of global development strategies. In order to bring the ethics of consumption into the context of ecotourism, we provide a case account of ecotourism that represents one of the more popular versions, national park tourism, and the exchanges that occur over what we call the \u27moral terrains\u27 of ecotourism. At Uluru-Kata Tju!a National Park ecotourism pertains to market dynamics, colonialism, adjacent and conflicting heritage, challenges to environmental identity, micro-management strategies aimed at cultural reconciliation and political agency, as well as the cthics of entertainment that plagues tourism as a human form of consumption. We conclude with sections addressing the elevation of the ethics of ecotourism to a quandary of global environmental justice and utilize the controversy of the Uluru-climb to exemplify nOlmative demands on today\u27s quest for sustainable tourism

Optimal Microlensing Observations

One of the major limitations of microlensing observations toward the Large Magellanic Cloud (LMC) is the low rate of event detection. What can be done to improve this rate? Is it better to invest telescope time in more frequent observations of the inner high surface-brightness fields, or in covering new, less populated outer fields? How would a factor 2 improvement in CCD sensitivity affect the detection efficiency? Would a series of major (factor 2--4) upgrades in telescope aperture, seeing, sky brightness, camera size, and detector efficiency increase the event rate by a huge factor, or only marginally? I develop a simplified framework to address these questions. With observational resources fixed at the level of the MACHO and EROS experiments, the biggest improvement (factor ~2) would come by reducing the time spent on the inner ~25 deg^2 and applying it to the outer ~100 deg^2. By combining this change with the characteristics of a good medium-size telescope (2.5 m mirror, 1" point spread function, thinned CCD chips, 1 deg^2 camera, and dark sky), it should be possible to increase the detection of LMC events to more than 100 per year (assuming current estimates of the optical depth apply to the entire LMC).Comment: Submitted to ApJ, 13 pages plus 3 figure

Coarse Projective kMC Integration: Forward/Reverse Initial and Boundary Value Problems

In "equation-free" multiscale computation a dynamic model is given at a fine, microscopic level; yet we believe that its coarse-grained, macroscopic dynamics can be described by closed equations involving only coarse variables. These variables are typically various low-order moments of the distributions evolved through the microscopic model. We consider the problem of integrating these unavailable equations by acting directly on kinetic Monte Carlo microscopic simulators, thus circumventing their derivation in closed form. In particular, we use projective multi-step integration to solve the coarse initial value problem forward in time as well as backward in time (under certain conditions). Macroscopic trajectories are thus traced back to unstable, source-type, and even sometimes saddle-like stationary points, even though the microscopic simulator only evolves forward in time. We also demonstrate the use of such projective integrators in a shooting boundary value problem formulation for the computation of "coarse limit cycles" of the macroscopic behavior, and the approximation of their stability through estimates of the leading "coarse Floquet multipliers".Comment: Submitted to Journal of Computational Physic

Low absorption InP/InGaAs-MQW phase shifters for optical switching

InP/InGaAs-MQW phase shifters with low absorption loss and low electroabsorption loss have been realized. Phase shift efficiency for TE-polarized light at lambda =1.55 mu m was 6.8 degrees V/sup -1/ mm/sup -1/ with negligible absorption loss and at lambda =1.51 mu m the efficiency was 8.9 degrees V/sup -1/ mm/sup -1/ with 5 dB/cm absorption los

AGAPE, an experiment to detect MACHO's in the direction of the Andromeda galaxy

The status of the Agape experiment to detect Machos in the direction of the andromeda galaxy is presented.Comment: 4 pages, 1 figure in a separate compressed, tarred, uuencoded uufile. In case ofproblem contact [email protected]

AgapeZ1: a Large Amplification Microlensing Event or an Odd Variable Star Towards the Inner Bulge of M31

AgapeZ1 is the brightest and the shortest duration microlensing candidate event found in the Agape data. It occured only 42" from the center of M31. Our photometry shows that the half intensity duration of the event6 is 4.8 days and at maximum brightness we measure a stellar magnitude of R=18.0 with B-R=0.80 mag color. A search on HST archives produced a single resolved star within the projected event position error box. Its magnitude is R=22.Comment: 4 pages with 5 figure