A century of warfare shoots holes in anti-Caulerpa campaign

Effort to have all varieties of the marine alga Caulerpa taxifolia listed as noxious weeds hinges on the argument that the alga's proliferation in the Mediterranean Sea is a cause and not a consequence of environmental degradation. Until now, the occurrence of two populations in a pristine part of the northern Mediterranean near the island of Porquerolles has upheld this claim. Here we show that the alga's development at Porquerolles is indeed a consequence of environmental degradation caused by military weapons' impacts on seagrass beds during the last century. The available data show that substratum enrichment plays a key role in fostering development of Caulerpa, irrespective of whether this results directly from pollution or from the impacts of pollution and other anthropogenic factors on benthic vegetation cover

The Mid-Infrared Instrument for the James Webb Space Telescope, VIII: The MIRI Focal Plane System

We describe the layout and unique features of the focal plane system for MIRI. We begin with the detector array and its readout integrated circuit (combining the amplifier unit cells and the multiplexer), the electronics, and the steps by which the data collection is controlled and the output signals are digitized and delivered to the JWST spacecraft electronics system. We then discuss the operation of this MIRI data system, including detector readout patterns, operation of subarrays, and data formats. Finally, we summarize the performance of the system, including remaining anomalies that need to be corrected in the data pipeline

Measuring Cluster Temperature Profiles with XMM/EPIC

Using the PV observation of A1795, we illustrate the capability of XMM-EPIC to measure cluster temperature profiles, a key ingredient for the determination of cluster mass profiles through the equation of hydrostatic equilibrium. We develop a methodology for spatially resolved spectroscopy of extended sources, adapted to XMM background and vignetting characteristics. The effect of the particle induced background is discussed. A simple unbiased method is proposed to correct for vignetting effects, in which every photon is weighted according to its energy and location on the detector. We were able to derive the temperature profile of A1795 up to 0.4 times the virial radius. A significant and spatially resolved drop in temperature towards the center (r<200 kpc) is observed, which corresponds to the cooling flow region of the cluster. Beyond that region, the temperature is constant with no indication of a fall-off at large radii out to 1.2 Mpc.Comment: 7 pages, 8 figures, Accepted for publication in A&A (special Letter issue on XMM

Comparison of source detection procedures for XMM-Newton images

Procedures based on current methods to detect sources in X-ray images are applied to simulated XMM images. All significant instrumental effects are taken into account, and two kinds of sources are considered -- unresolved sources represented by the telescope PSF and extended ones represented by a b-profile model. Different sets of test cases with controlled and realistic input configurations are constructed in order to analyze the influence of confusion on the source analysis and also to choose the best methods and strategies to resolve the difficulties. In the general case of point-like and extended objects the mixed approach of multiresolution (wavelet) filtering and subsequent detection by SExtractor gives the best results. In ideal cases of isolated sources, flux errors are within 15-20%. The maximum likelihood technique outperforms the others for point-like sources when the PSF model used in the fit is the same as in the images. However, the number of spurious detections is quite large. The classification using the half-light radius and SExtractor stellarity index is succesful in more than 98% of the cases. This suggests that average luminosity clusters of galaxies (L_[2-10] ~ 3x10^{44} erg/s) can be detected at redshifts greater than 1.5 for moderate exposure times in the energy band below 5 keV, provided that there is no confusion or blending by nearby sources. We find also that with the best current available packages, confusion and completeness problems start to appear at fluxes around 6x10^{-16} erg/s/cm^2 in [0.5-2] keV band for XMM deep surveys.Comment: 20 pages, 16 figures. Accepted for publication in A&

Statistical Model of Shape Moments with Active Contour Evolution for Shape Detection and Segmentation

This paper describes a novel method for shape representation and robust image segmentation. The proposed method combines two well known methodologies, namely, statistical shape models and active contours implemented in level set framework. The shape detection is achieved by maximizing a posterior function that consists of a prior shape probability model and image likelihood function conditioned on shapes. The statistical shape model is built as a result of a learning process based on nonparametric probability estimation in a PCA reduced feature space formed by the Legendre moments of training silhouette images. A greedy strategy is applied to optimize the proposed cost function by iteratively evolving an implicit active contour in the image space and subsequent constrained optimization of the evolved shape in the reduced shape feature space. Experimental results presented in the paper demonstrate that the proposed method, contrary to many other active contour segmentation methods, is highly resilient to severe random and structural noise that could be present in the data

XMM- Newton Observation of the Coma Galaxy Cluster: The temperature structure in the central region

We present a temperature map and a temperature profile of the central part (r < 20' or 1/4 virial radius) of the Coma cluster. We combined 5 overlapping pointings made with XMM/EPIC/MOS and extracted spectra in boxes of 3.5' X 3.5'. The temperature distribution around the two central galaxies is remarkably homogeneous (r<10'), contrary to previous ASCA results, suggesting that the core is actually in a relaxed state. At larger distance from the cluster center we do see evidence for recent matter accretion. We confirm the cool area in the direction of NGC 4921, probably due to gas stripped from an infalling group. We find indications of a hot front in the South West, in the direction of NGC4839, probably due to an adiabatic compression

The Mid-Infrared Instrument for the James Webb Space Telescope, III: MIRIM, The MIRI Imager

In this article, we describe the MIRI Imager module (MIRIM), which provides broad-band imaging in the 5 - 27 microns wavelength range for the James Webb Space Telescope. The imager has a 0"11 pixel scale and a total unobstructed view of 74"x113". The remainder of its nominal 113"x113" field is occupied by the coronagraphs and the low resolution spectrometer. We present the instrument optical and mechanical design. We show that the test data, as measured during the test campaigns undertaken at CEA-Saclay, at the Rutherford Appleton Laboratory, and at the NASA Goddard Space Flight Center, indicate that the instrument complies with its design requirements and goals. We also discuss the operational requirements (multiple dithers and exposures) needed for optimal scientific utilization of the MIRIM.Comment: 29 pages, 9 figure