Classification and analysis of emission-line galaxies using mean field independent component analysis

We present an analysis of the optical spectra of narrow emission-line galaxies, based on mean field independent component analysis (MFICA). Samples of galaxies were drawn from the Sloan Digital Sky Survey (SDSS) and used to generate compact sets of `continuum' and `emission-line' component spectra. These components can be linearly combined to reconstruct the observed spectra of a wider sample of galaxies. Only 10 components - five continuum and five emission line - are required to produce accurate reconstructions of essentially all narrow emission-line galaxies; the median absolute deviations of the reconstructed emission-line fluxes, given the signal-to-noise ratio (S/N) of the observed spectra, are 1.2-1.8 sigma for the strong lines. After applying the MFICA components to a large sample of SDSS galaxies we identify the regions of parameter space that correspond to pure star formation and pure active galactic nucleus (AGN) emission-line spectra, and produce high S/N reconstructions of these spectra. The physical properties of the pure star formation and pure AGN spectra are investigated by means of a series of photoionization models, exploiting the faint emission lines that can be measured in the reconstructions. We are able to recreate the emission line strengths of the most extreme AGN case by assuming the central engine illuminates a large number of individual clouds with radial distance and density distributions, f(r) ~ r^gamma and g(n) ~ n^beta, respectively. The best fit is obtained with gamma = -0.75 and beta = -1.4. From the reconstructed star formation spectra we are able to estimate the starburst ages. These preliminary investigations serve to demonstrate the success of the MFICA-based technique in identifying distinct emission sources, and its potential as a tool for the detailed analysis of the physical properties of galaxies in large-scale surveys.Comment: MNRAS accepted. 29 pages, 24 figures, 3 table

Interpreting the Ionization Sequence in AGN Emission-Line Spectra

We investigate the physical cause of the great range in the ionization level seen in the spectra of narrow lined active galactic nuclei (AGN). Mean field independent component analysis identifies examples of individual SDSS galaxies whose spectra are not dominated by emission due to star formation (SF), which we designate as AGN. We assembled high S/N ratio composite spectra of a sequence of these AGN defined by the ionization level of their narrow-line regions (NLR), extending down to very low-ionization cases. We used a local optimally emitting cloud (LOC) model to fit emission-line ratios in this AGN sequence. These included the weak lines that can be measured only in the co-added spectra, providing consistency checks on strong line diagnostics. After integrating over a wide range of radii and densities our models indicate that the radial extent of the NLR is the major parameter in determining the position of high to moderate ionization AGN along our sequence, providing a physical interpretation for their systematic variation. Higher ionization AGN contain optimally emitting clouds that are more concentrated towards the central continuum source than in lower ionization AGN. Our LOC models indicate that for the objects that lie on our AGN sequence, the ionizing luminosity is anticorrelated with the NLR ionization level, and hence anticorrelated with the radial concentration and physical extent of the NLR. A possible interpretation that deserves further exploration is that the ionization sequence might be an age sequence where low ionization objects are older and have systematically cleared out their central regions by radiation pressure. We consider that our AGN sequence instead represents a mixing curve of SF and AGN spectra, but argue that while many galaxies do have this type of composite spectra, our AGN sequence appears to be a special set of objects with negligible SF excitation.Comment: 57 pages; 18 figures, accepted by MNRA

Leech Parasitism of the Gulf Coast Box Turtle, Terrapene carolina major (Testudines:Emydidae) in Mississippi, USA

Ten leeches were collected from a Gulf Coast box turtle, Terrapene carolina major, found crossing a road in Gulfport, Harrison County, Mississippi, USA. Eight of the leeches were identified as Placobdella multilineata and 2 were identified as Helobdella europaea. This represents the second vouchered report of leeches from a box turtle. Helobdella europaea is reported for the first time associated with a turtle and for the second time from the New World

Restrictions of generalized Verma modules to symmetric pairs

We initiate a new line of investigation on branching problems for generalized Verma modules with respect to complex reductive symmetric pairs (g,k). Here we note that Verma modules of g may not contain any simple module when restricted to a reductive subalgebra k in general. In this article, using the geometry of K_C orbits on the generalized flag variety G_C/P_C, we give a necessary and sufficient condition on the triple (g,k, p) such that the restriction X|_k always contains simple k-modules for any g-module $X$ lying in the parabolic BGG category O^p attached to a parabolic subalgebra p of g. Formulas are derived for the Gelfand-Kirillov dimension of any simple k-module occurring in a simple generalized Verma module of g. We then prove that the restriction X|_k is multiplicity-free for any generic g-module X \in O if and only if (g,k) is isomorphic to a direct sum of (A_n,A_{n-1}), (B_n,D_n), or (D_{n+1},B_n). We also see that the restriction X|_k is multiplicity-free for any symmetric pair (g, k) and any parabolic subalgebra p with abelian nilradical and for any generic g-module X \in O^p. Explicit branching laws are also presented.Comment: 31 pages, To appear in Transformation Group

The Nature of the H2-Emitting Gas in the Crab Nebula

Understanding how molecules and dust might have formed within a rapidly expanding young supernova remnant is important because of the obvious application to vigorous supernova activity at very high redshift. In previous papers, we found that the H2 emission is often quite strong, correlates with optical low-ionization emission lines, and has a surprisingly high excitation temperature. Here we study Knot 51, a representative, bright example, for which we have available long slit optical and NIR spectra covering emission lines from ionized, neutral, and molecular gas, as well as HST visible and SOAR Telescope NIR narrow-band images. We present a series of CLOUDY simulations to probe the excitation mechanisms, formation processes and dust content in environments that can produce the observed H2 emission. We do not try for an exact match between model and observations given Knot 51's ambiguous geometry. Rather, we aim to explain how the bright H2 emission lines can be formed from within the volume of Knot 51 that also produces the observed optical emission from ionized and neutral gas. Our models that are powered only by the Crab's synchrotron radiation are ruled out because they cannot reproduce the strong, thermal H2 emission. The simulations that come closest to fitting the observations have the core of Knot 51 almost entirely atomic with the H2 emission coming from just a trace molecular component, and in which there is extra heating. In this unusual environment, H2 forms primarily by associative detachment rather than grain catalysis. In this picture, the 55 H2-emitting cores that we have previously catalogued in the Crab have a total mass of about 0.1 M_sun, which is about 5% of the total mass of the system of filaments. We also explore the effect of varying the dust abundance. We discuss possible future observations that could further elucidate the nature of these H2 knots.Comment: 51 pages, 15 figures, accepted for publication in MNRAS, revised Figure 12 results unchange

Exploring the movement dynamics of deception

Both the science and the everyday practice of detecting a lie rest on the same assumption: hidden cognitive states that the liar would like to remain hidden nevertheless influence observable behavior. This assumption has good evidence. The insights of professional interrogators, anecdotal evidence, and body language textbooks have all built up a sizeable catalog of non-verbal cues that have been claimed to distinguish deceptive and truthful behavior. Typically, these cues are discrete, individual behaviors—a hand touching a mouth, the rise of a brow—that distinguish lies from truths solely in terms of their frequency or duration. Research to date has failed to establish any of these non-verbal cues as a reliable marker of deception. Here we argue that perhaps this is because simple tallies of behavior can miss out on the rich but subtle organization of behavior as it unfolds over time. Research in cognitive science from a dynamical systems perspective has shown that behavior is structured across multiple timescales, with more or less regularity and structure. Using tools that are sensitive to these dynamics, we analyzed body motion data from an experiment that put participants in a realistic situation of choosing, or not, to lie to an experimenter. Our analyses indicate that when being deceptive, continuous fluctuations of movement in the upper face, and somewhat in the arms, are characterized by dynamical properties of less stability, but greater complexity. For the upper face, these distinctions are present despite no apparent differences in the overall amount of movement between deception and truth. We suggest that these unique dynamical signatures of motion are indicative of both the cognitive demands inherent to deception and the need to respond adaptively in a social context

Fungicides for Potato Blight Control

South Dakota has an important potato- growing area in Clark, Codington, Hamlin and Deuel counties. Production of certified seed has become one of the important phases of the potato industry in South Dakota. In addition to the main commercial seed and table stock production areas indicated above, smaller producing areas are located in various sections of the state, not to mention the familiar potato patch in most home gardens. Likewise, with the coming of irrigation in the James River Valley of South Dakota, potato production will probably increase further. Losses in yield and quality of potatoes are severe in seasons favorable to the development of foliage diseases. While these diseases do not occur in serious amounts every season in South Dakota, the profits may be wiped out in those years when they are prevalent. When these diseases strike in epidemic proportions, one of the important effects which they have on the crop is the prevention of normal sizing of the tubers, thereby resulting in a reduction of U. S. No. 1 potatoes. For this reason, it is important to know what control measures are effective and can be easily and quickly applied when these diseases strike the crop. An effective fungicide, properly applied, can control these foliage diseases, and by removing another crop hazard can thereby add to the stability of commercial and certified seed potato production in South Dakota. Chemical fungicides, applied as sprays or dusts, differ in their effectiveness in controlling crop diseases. A particular fungicide might be highly effective in combating one type of disease, but may not be very effective against another. Consequently, it becomes necessary to test many chemicals over a period of several years to determine their effectiveness as well as the dosage rate and the proper time of the season to apply them. The most prevalent fungus diseases affecting potato foliage in the state are early blight, caused by Alternaria solcmi, and late blight, caused by Phytophthora infestans. Early blight is present to some extent every season in South Dakota, and causes losses through reduced grade and yield. The disease first appears as small oval or angular brown spots on the leaves with characteristic target-like markings. As the spots increase in size and number the affected leaves die. As a result of this defoliation the yield, especially of U. S. No. 1 grade potatoes, is reduced. During those seasons when conditions are favorable for the development of late blight, losses through reduced yields and tuber rot become costly to potato growers. Late blight is favored by cool temperatures and relatively good moisture conditions. This disease first appears on the leaves as pale green, water-soaked, irregular-shaped spots which may enlarge rapidly, turn brown or black, and show a white mildew-like appearance on the lower surface of diseased leaves. The stems can become infected and the entire plant may be killed in a few days. Under conditions favorable for the disease (moderate temperatures, with high humidity, heavy clews or frequent rains), it can spread rapidly throughout a field. Spores from diseased foliage washed down to the tubers by rain or brought in contact with them during digging operations can expose tubers to infection with late blight. Late blight-infected tubers develop what is known as late blight tuber rot, either in the field or in storage. To protect potato plants from these fungus diseases, it is necessary to keep the foliage coated with an effective fungicide. It has been shown experimentally that fungicides applied as sprays provide better coverage and disease control than those applied as dusts. A series of field experiments were initiated in 1945 at the Experiment Station at Brookings with the object of developing a potato spray program adapted to South Dakota conditions. In 1946, these tests formed a part of a regional potato fungicide trial in which six states in the upper Mississippi Valley participated. From 1947 to 1949 the tests were included in the national cooperative fungicide experiments sponsored by a Special Committee on the Coordination of Field Tests with New Fungicidal Sprays and Dusts, appointed by the American Phytopathological Society

Tomato Leaf Spot Control

The most important plant disease affecting tomatoes during the past 10 years in South Dakota has been a fungus disease known as Septoria leaf spot (Septoria lycopersici). Other diseases have been of minor importance, namely late blight, Alternaria leaf spot, wilt and virus troubles. Septoria leaf spot frequently develops rapidly and may, under favorable conditions, completely defoliate the crop within a few weeks. When defoliation by the disease occurs, the yield may be markedly reduced. Fruit produced on such plants becomes flabby and the flavor is of low quality. The tomato is one of our most important vegetable crops. It is grown by virtually every home gardener and is high in certain vitamins which are important in the family diet, though it is not grown extensively on a commercial scale in the state at the present time. Septoria leaf spot may be recognized by the characteristic spots (see cover) on the leaves and stems which are approximately one-eighth inch in diameter. The margins of the spots usually become dark reddish- brown in color while the centers are light grey with a few scattered tiny black specks. When the spots become very numerous the affected leaves turn from light green to brown, die and drop from the plants. When the leaves are killed by the disease the fruits ripen prematurely and have an insipid flavor. These symptoms should distinguish Septoria leaf spot from other fungus diseases affecting the foliage. Early blight (Alternaria solani) forms larger irregular spots onefourth to one-half inch in diameter with numerous inconspicuous concentric rings within the diseased spot. Late blight (Phytophthora infestans) forms larger patches on the leaves which may, under certain weather conditions, involve entire leaves. The lesions appear water-soaked at first, but later become light brown to dark brown and in moist weather show a white mildew-like growth on the lower side of the leaves. This disease also causes a characteristic brown rot of the fruit which may result in heavy losses in yield of marketable fruit. Tomato plants can be protected from these fungus diseases by repeated applications with an effective fungicide. The first application should be made when the leaf spots first appear, and then repeated at 10-day intervals. It has been shown experimentally that sprays provide better coverage and protection than dusts. The lower as well as the upper surfaces of the leaves should be covered. In order to determine the most effective fungicide for the control of tomato foliage diseases in South Dakota a series of field experiments was started in 1944 at the State College Experiment Station

Belief propagation algorithm for computing correlation functions in finite-temperature quantum many-body systems on loopy graphs

Belief propagation -- a powerful heuristic method to solve inference problems involving a large number of random variables -- was recently generalized to quantum theory. Like its classical counterpart, this algorithm is exact on trees when the appropriate independence conditions are met and is expected to provide reliable approximations when operated on loopy graphs. In this paper, we benchmark the performances of loopy quantum belief propagation (QBP) in the context of finite-tempereture quantum many-body physics. Our results indicate that QBP provides reliable estimates of the high-temperature correlation function when the typical loop size in the graph is large. As such, it is suitable e.g. for the study of quantum spin glasses on Bethe lattices and the decoding of sparse quantum error correction codes.Comment: 5 pages, 4 figure