Automatic classification of grassland herbs in close-range sensed digital colour images

The broad-leaved dock (Rumex obtusifolius L. (RUMOB)) is one of the most harmful and persistent weed species on European grassland and it has been spread into the temperate grassland regions throughout the world. Large dry matter contributions of Rumex obtusifolius L. reduce the quality of the standing forage considerably because of the poor palatability of leaves and tillers and withdraw water and nutrient from surrounding plants. For Central Europe it is estimated that more than 80% of all herbicides used in conventional grassland farming are used to control Rumex species. Until today, herbicides are applied over the whole field, even if Rumex plants are not homogeneously distributed area-wide. Recently developed precision farming techniques based on weed mapping that use mainly image processing, enable site-specific spraying of weeds in arable crops. Until today those techniques have not been applied to grassland weed sensing. Compared to the identification of isolated individual plants on a rather uniform soil background in arable crops, image processing for a more complex environment as grassland requires a different approach. The aim of the thesis was to develop an image processing procedure for automatic detection of grassland weeds using close-range digital colour images, focussing on the detection of RUMOB. A field experiment has been established with grassland plots populated with RUMOB and the other typical broad leaved grassland weeds Taraxacum officinale Web. (TAROF) and Plantago major L. (PLAMA). Digital colour images have been taken from around 1.5 m above ground at three dates in 2005. Image acquisition was done automatically by a vehicle driven on rails alongside to the experimental plots, whereby nearly constant recording geometry conditions were guaranteed. Images were taken during cloud cover in order to avoid direct sunlight. Using the images from 2005 an object-oriented image classification has been developed. Thereby, the leaves of the weeds were separated from the background using parameters of homogeneity and morphology, resulting in a binary image. The remaining image objects in the binary image were contiguous regions of neighbouring pixels related to the object classes of the weed species, soil, and residue objects. Geometrical-, colour and texture features were calculated for each of these objects. Discriminant analysis exhibited that colour and texture features contribute most to the discriminating of objects into the different classes. In a Maximum Likelihood classification these features were used to differentiate the objects into their respective classes. High overall accuracies and even higher RUMOB detection rates were achieved. The algorithm has been modified and applied to images of varying image resolutions. High classification accuracies have been achieved with all image resolutions, whereby the processing time could be improved for images with lowest resolutions. Images were taken at 13 dates over the two grassland growths in 2006. In all the images the plant species were classified automatically using the developed image classification integrated in a graphical user interface software. The coordinates of the objects classified as RUMOB were transformed into Gauss-Krueger system to generate distribution maps of this weed. The combination of object density and area further decreased its misclassifications. RUMOB classification rates across the season were analysed and phenological stages have been identified on which classification performed best. The results demonstrate high potential of machine vision for weed detection in grassland. A classification procedure based on image analysis and Geographic Information System (GIS) post-processing has been developed for detecting Rumex obtusifolius L. and other weeds in grassland with high accuracy. Future projects might focus on the application to real grassland conditions and the derivation of RUMOB distribution maps. Thus, herbicide application maps can be calculated, utilized for site-specific weed control. The development of an image acquisition unit to be mounted on a driving vehicle along with a standardization of image recording is going to be the main focus

Web services enabled architecture coupling data and functional resources

Web services are the backbone of WISDOM system, an information and visualisation system supporting decision makers in the fields of water related management processes based on open source technologies. They enable the distributed and loosely coupled, component based architecture of the system. In cooperating OGC compliant web services for data access, visualisation and data processing the system is extendible to external data resources and other proprietary software solutions. The base idea behind the designed and prototypically implemented WISDOM techniques is the orchestration of decoupled web resources representing data sets and functionality to model more complex business processes quite easily. The system covers most aspects of administrative business processes including spatial and non-spatial data ingestion and dissemination, necessary data processing and visualisation techniques. In combination with a semantics enabled data management WISDOM system is capable to produce value added information products to water management related tasks autonomously. These compound data and processing resource chains are implemented to facilitate certain identified business processes in regional administration. Clients like data and information explorers supporting manual interaction as human machine interfaces or automated data access of value adding operations accomplish, respectively trigger these integrative chains. As an example the same data and processing infrastructure is used to visualise data in map clients as WMS or access data as WCS, resp. WFS for further processing which can furthermore trigger additional actions like feeding reports or requesting auxiliary data

Comoving Space Density and Obscured Fraction of High-Redshift Active Galactic Nuclei in the Subaru/{\it XMM-Newton} Deep Survey

We study the comoving space density of X-ray-selected luminous active galactic nuclei (AGNs) and the obscured AGN fraction at high redshifts ($3 < z < 5$) in the Subaru/{\it XMM-Newton} Deep Survey (SXDS) field. From an X-ray source catalog with high completeness of optical identification thanks to deep optical images, we select a sample of 30 AGNs at $z > 3$ with intrinsic (de-absorbed and rest-frame 2--10 keV) luminosities of $L_{\rm X} = 10^{44-45}$ erg s$^{-1}$ detected in the 0.5--2 keV band, consisting of 20 and 10 objects with spectroscopic and photometric redshifts, respectively. Utilizing the $1/V_{\rm max}$ method, we confirm that the comoving space density of luminous AGNs decreases with redshift above $z > 3$. When combined with the {\it Chandra}-COSMOS result of Civano et al.\ (2011), the density decline of AGNs with $L_{\rm X} = 10^{44-45}$ erg s$^{-1}$ is well represented by a power law of $(1 + z)^{-6.2 \pm 0.9}$. We also determine the fraction of X-ray obscured AGNs with $N_{\rm H} > 10^{22}$ cm$^{-2}$ in the Compton-thin population to be 0.54$^{+0.17}_{-0.19}$, by carefully taking into account observational biases including the effects of photon statistics for each source. This result is consistent with an independent determination of the type-2 AGN fraction based on optical properties, for which the fraction is found to be 0.59$\pm$0.09. Comparing our result with that obtained in the local Universe, we conclude that the obscured fraction of luminous AGNs increases significantly from $z=0$ to $z>3$ by a factor of 2.5$\pm$1.1.Comment: 12 pages, 12 figures, 1 table. Accepted for publication in Ap

Evidence for an intermediate line region in AGN's inner torus region and its evolution from narrow to broad line Seyfert I galaxies

A two-components model for Broad Line Region (BLR) of Active Galactic Nuclei (AGN) has been suggested for many years but not widely accepted (e.g., Hu et al. 2008; Sulentic et al. 2000; Brotherton et al. 1996; Mason et al. 1996). This model indicates that the broad line can be described with superposition of two Gaussian components (Very Broad Gaussian Component (VBGC) and InterMediate Gaussian Component (IMGC)) which are from two physically distinct regions; i.e., Very Broad Line Region (VBLR) and InterMediate Line Region (IMLR). We select a SDSS sample to further confirm this model and give detailed analysis to the geometry, density and evolution of these two regions. Micro-lensing result of BLR in J1131-1231 and some unexplained phenomena in Reverberation Mapping (RM) experiment provide supportive evidence for this model. Our results indicate that the radius obtained from the emission line RM normally corresponds to the radius of the VBLR, and the existence of the IMGC may affect the measurement of the black hole masses in AGNs. The deviation of NLS1s from the M-sigma relation and the Type II AGN fraction as a function of luminosity can be explained in this model in a coherent way. The evolution of the two emission regions may be related to the evolutionary stages of the broad line regions of AGNs from NLS1s to BLS1s. Based on the results presented here, a unified picture of hierarchical evolution of black hole, dust torus and galaxy is proposed.Comment: 58 pages, 19 figures, 1 table. Matches the published versio

Why are AGN found in High Mass Galaxies?

We use semi-analytic models implemented in the Millennium Simulation to analyze the merging histories of dark matter haloes and of the galaxies that reside in them. We assume that supermassive black holes only exist in galaxies that have experienced at least one major merger. Only a few percent of galaxies with stellar masses less than $M_* < 10^{10} M_{\odot}$ are predicted to have experienced a major merger and to contain a black hole. The fraction of galaxies with black holes increases very steeply at larger stellar masses. This agrees well with the observed strong mass dependence of the fraction of nearby galaxies that contain either low-luminosity (LINER-type) or higher-luminosity (Seyfert or composite-type) AGN. We then investigate when the major mergers that first create the black holes are predicted to occur. High mass galaxies are predicted to have formed their black holes at very early epochs. The majority of low mass galaxies never experience a major merger and hence do not contain a black hole, but a significant fraction of the supermassive black holes that do exist in low mass galaxies are predicted to have formed recently.Comment: 7 pages,7 figures, MNRAS submitte

A Chandra view of NGC 3621: a bulgeless galaxy hosting an AGN in its early phase?

We report the detection of a weak X-ray point source coincident with the nucleus of the bulgeless disk galaxy NGC 3621, recently discovered by Spitzer to display high ionization mid-infrared lines typically associated with AGN. These Chandra observations provide confirmation for the presence of an AGN in this galaxy, adding to the growing evidence that black holes do form and grow in isolated bulgeless disk galaxies. Although the low signal-to-noise ratio of the X-ray spectrum prevents us from carrying out a detailed spectral analysis of the nuclear source, the X-ray results, combined with the IR and optical spectroscopic results, suggests that NGC 3621 harbors a heavily absorbed AGN, with a supermassive black hole of relatively small mass accreting at a high rate. Chandra also reveals the presence of two bright sources straddling the nucleus located almost symmetrically at 20" from the center. Both sources have X-ray spectra that are well-fitted by an absorbed power-law model. Assuming they are at the distance of NGC 3621, these two sources have luminosities of the order of 1.e39 erg/s, which make them ULXs and suggest that they are black hole systems. Estimates of the black hole mass based on the X-ray spectral analysis and scaling laws of black hole systems suggest that the 2 bright sources might be intermediate mass black holes with M_BH of the order of a few thousand solar masses. However, higher quality X-ray data combined with multi-wavelength observations are necessary to confirm these conclusions.Comment: 12 pages, 9 figures, 1 table, accepted for publication in Ap

X-ray Properties of Intermediate-Mass Black Holes in Active Galaxies. II. X-ray-Bright Accretion and Possible Evidence for Slim Disks

We present X-ray properties of optically-selected intermediate-mass (~10^5--10^6 M_Sun) black holes (BHs) in active galaxies (AGNs), using data from the Chandra X-Ray Observatory. Our observations are a continuation of a pilot study by Greene & Ho (2007). Of the 8 objects observed, 5 are detected with X-ray luminosities in the range L_0.5-2 keV = 10^41--10^43 erg s^-1, consistent with the previously observed sample. Objects with enough counts to extract a spectrum are well fit by an absorbed power law. We continue to find a range of soft photon indices 1 < \Gamma_s < 2.7, where N(E) \propto E^-\Gamma_s, consistent with previous AGN studies, but generally flatter than other narrow-line Seyfert 1 active nuclei (NLS1s). The soft photon index correlates strongly with X-ray luminosity and Eddington ratio, but does not depend on BH mass. There is no justification for the inclusion of any additional components, such as a soft excess, although this may be a function of the relative inefficiency of detecting counts above 2 keV in these relatively shallow observations. As a whole, the X-ray-to-optical spectral slope \alpha_ox is flatter than in more massive systems, even other NLS1s. Only X-ray-selected NLS1s with very high Eddington ratios share a similar \alpha_ox. This is suggestive of a physical change in the accretion structure at low masses and at very high accretion rates, possibly due to the onset of slim disks. Although the detailed physical explanation for the X-ray loudness of these intermediate-mass BHs is not certain, it is very striking that targets selected on the basis of optical properties should be so distinctly offset in their broader spectral energy distributions.Comment: 11 pages, 6 figures, submitted to ApJ, emulateap

On the Anticorrelation Between Galaxy Light Concentration and X-ray-to-Optical Flux Ratio

Active Galactic Nuclei (AGN) play an important role in many aspects of the modern cosmology, and of particular interest is the issue of the interplay between AGN and their host galaxy. Using X-ray and optical data sets, we have explored the properties of a large sample of AGNs in the Subaru/XMM-Newton Deep Survey (SXDS) field, and studied their evolution in relation with the evolution of their host galaxy. We present here an anticorrelation between X-ray-to-optical flux ratio (X/O) and galaxy light concentration (C), which has been found for the first time and might suggest that early type galaxies, having poor matter supply to feed the AGN activity, have lower Eddington rates than those of late type galaxies.Comment: 9 pages, 3 figures, accepted for publication in ApJ Letter

Determining Quasar Black Hole Mass Functions from their Broad Emission Lines: Application to the Bright Quasar Survey

We describe a Bayesian approach to estimating quasar black hole mass functions (BHMF) when using the broad emission lines to estimate black hole mass. We show how using the broad line mass estimates in combination with statistical techniques developed for luminosity function estimation leads to statistically biased results. We derive the likelihood function for the BHMF based on the broad line mass estimates, and derive the posterior distribution for the BHMF, given the observed data. We develop our statistical approach for a flexible model where the BHMF is modelled as a mixture of Gaussian functions. Statistical inference is performed using markov chain monte carlo (MCMC) methods. Our method has the advantage that it is able to constrain the BHMF even beyond the survey detection limits at the adopted confidence level, accounts for measurement errors and the intrinsic uncertainty in broad line mass estimates, and provides a natural way of estimating the probability distribution of any quantities derived from the BHMF. We conclude by using our method to estimate the local active BHMF using the z < 0.5 Bright Quasar Survey sources. At z = 0.2, the quasar BHMF falls off approximately as a power law with slope ~ 2 for M_{BH} > 10^8. Our analysis implies that z < 0.5 broad line quasars have a typical Eddington ratio of ~ 0.4 and a dispersion in Eddington ratio of < 0.5 dex (abridged).Comment: 25 pages, 14 figures, emulate ApJ style, accepted by Ap

Efficient laser-driven proton acceleration from cylindrical and planar cryogenic hydrogen jets.

We report on recent experimental results deploying a continuous cryogenic hydrogen jet as a debris-free, renewable laser-driven source of pure proton beams generated at the 150 TW ultrashort pulse laser Draco. Efficient proton acceleration reaching cut-off energies of up to 20 MeV with particle numbers exceeding 109 particles per MeV per steradian is demonstrated, showing for the first time that the acceleration performance is comparable to solid foil targets with thicknesses in the micrometer range. Two different target geometries are presented and their proton beam deliverance characterized: cylindrical (∅ 5 μm) and planar (20 μm × 2 μm). In both cases typical Target Normal Sheath Acceleration emission patterns with exponential proton energy spectra are detected. Significantly higher proton numbers in laser-forward direction are observed when deploying the planar jet as compared to the cylindrical jet case. This is confirmed by two-dimensional Particle-in-Cell (2D3V PIC) simulations, which demonstrate that the planar jet proves favorable as its geometry leads to more optimized acceleration conditions