Distribution by Scientific Domains
Distribution within Physics and Astronomy

Kinds of Observatory

  • astronomical observatory
  • bird observatory
  • chandra x-ray observatory
  • european southern observatory
  • national observatory
  • southern observatory
  • x-ray observatory

  • Selected Abstracts


    BJU INTERNATIONAL, Issue 4 2009
    Benjamin E. Ayres
    No abstract is available for this article. [source]

    Eine Grenze für die Zwerge

    Article first published online: 24 JUN 200
    Die NASA nennt es eines ihrer "Great Observatories" , neben dem Hubble Space Telescope und dem Compton Gamma Ray Observatory. Gestartet wurde es am 23. Juli 1999 und umkreist die Erde seitdem auf einer stark elliptischen Bahn einmal in 64 Stunden. [source]

    Right-wing authoritarianism, Big Five and perceived threat to safety

    Francesca Dallago
    Abstract Using structural equations modelling, we performed a secondary analysis of the data collected by the Italian Observatory of the North West (Italian national sample, N,=,976) to investigate the direct, mediated and moderated relations connecting the Big Five personality factors and perceived personal and societal threat to safety with right-wing authoritarianism (RWA). Openness, Conscientiousness and perceived societal threat to safety exerted additive effects on RWA; the relation between Openness and RWA was partially mediated by societal threat to safety and that between societal threat to safety and RWA was moderated by Openness. Limitations and possible developments of this research are discussed. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    The Swedish Deep Drilling Program: the quest for the Earth's inner secrets

    GEOLOGY TODAY, Issue 6 2009
    Henning Lorenz
    The Swedish Deep Drilling Program (SDDP) has been initiated to study fundamental problems of the dynamic Earth system, its natural history and evolution. Many key scientific questions can be addressed through in situ investigations only, requiring deep continental drilling. Some are unique to Scandinavia, most are of international interest and significance. At present, five core projects (Fig. 1) with international teams are integrating scientific problems with societal and industrial applications. If SDDP succeeds to attract the funding required, Sweden will have a number of world-class boreholes at key locations by 2020. Figure 1. Locations of SDDP drilling project proposals. PFDP,Postglacial Fault Drilling Project; PaMVAS,Palaeoproterozoic mineralized volcanic arc systems: the Skellefte District; COSC,Collisional Orogeny in the Scandinavian Caledonides; DRL,The Dellen Impact Crater, a geoscientific deep rock laboratory; SELHO,Svecofennian accretion, an example of the early structural evolution in a large hot orogen; CISP,Concentric Impact Structures in the Palaeozoic: the Lockne and Siljan craters. Background and inset image from Blue Marble Next Generation data set (NASA Earth Observatory, http://earthobservatory.nasa.gov/Features/BlueMarble/). [source]

    Multiyear to daily radon variability from continuous monitoring at the Amram tunnel, southern Israel

    S. M. Barbosa
    SUMMARY Radon is a naturally occurring radioactive noble gas generated within mineral grains of uranium bearing rocks by alpha decay from radium. The Amram tunnel (A. Bloch Geophysical Observatory) is a particularly suitable location for the investigation of radon variability. Located in the arid environment of the Arava desert, near Elat, the 170 m tunnel that constitutes the observatory enables radon monitoring in a desert environment and under fairly stable environmental conditions. The analysis of the temporal variability of continuous measurements of radon and environmental parameters at the Amram tunnel over a period of several years shows a complex temporal pattern characterized by non-stationary and multiscale features. Radon concentrations exhibit multiyear variability in the form of a increasing trend of ,1000 Bq m,3 yr,1 in the mean and much larger trends up to ,2500 Bq m,3 yr,1 in the maximum radon levels. Radon concentrations also display strong seasonal patterns, with maxima in summer and minima in winter, ranging from 2.5 kBq m,3 in winter to 35 kBq m,3 in summer. Intraseasonal variability is characterized by very large radon anomalies, with sharp increases of more than 20 kBq m,3 relative to the base level, that occur in spring and summer and last for several days. Daily periodic variability with maxima around midnight appears also in spring and summer, being absent in the cold months. Radon variability at seasonal, intraseasonal and daily timescales is associated with the air temperature outside the tunnel, specifically the temperature gradient between the external environment and the more stable environment inside the tunnel where the measurements are performed. [source]

    Network-magnetotelluric method and its first results in central and eastern Hokkaido, NE Japan

    Makoto Uyeshima
    Summary A new field observation technique based on the magnetotelluric (MT) method has been developed to determine deep and large-scale 3-D electrical conductivity distributions in the Earth. The method is named ,Network-MT', and employs a commercial telephone network, to measure voltage differences with long dipole lengths ranging from 10 to several tens of kilometres. This observation configuration enables us to obtain the telluric field distribution with nearly continuous coverage over a target region. Response functions are estimated between the respective voltage differences and the horizontal magnetic fields at a reference point. Owing to the long electrode spacing, the observed responses are relatively free from the effects of small-scale near-surface heterogeneity with a scalelength shorter than the typical electrode spacing. Therefore, physically meaningful direct comparison between the observations and model responses is feasible even if the fine-scale features of near-surface heterogeneity are ignored. This extensively reduces the difficulty, especially in 3-D MT interpretation. The first Network-MT experiment was performed in central and eastern Hokkaido, NE Japan, in 1989. It took about five months to complete all of the measurements, and used 209 dipoles to cover the target area of 200(EW) × 200(NS) km2. The long electrode spacing enabled us to obtain the voltage differences with a high signal-to-noise ratio. For 175 dipoles, the squared multiple coherency between the voltage difference and the horizontal magnetic field at Memambetsu Geomagnetic Observatory was determined to be more than 0.9 in the period from 102 to 104 s. 193 MT impedances were computed in tensor form by linear combination of the response functions. The estimated impedances generally possessed smooth period dependence throughout the period range. No drastic spatial change was observed in the characteristics of the tensors for neighbouring sites, and some regional trend could be detected in the spatial distribution. Thus, we confirmed the merit of the Network-MT method, that its responses are little affected by small-scale near-surface structures. The regional feature of the response implied a significant influence of the coast effect, and was well correlated with the regional geological setting in Hokkaido. Conventional Groom,Bailey tensor decomposition analysis revealed that the target region is not regionally one- or two-dimensional. Therefore, we developed a 3-D forward modelling scheme specially designed for the Network-MT experiment, and tried to reproduce the Network-MT responses directly. In the 3-D model, a realistic land,sea distribution was considered. The resistivity of sea water was fixed to be 0.25 , m and, as a first trial of 3-D modelling, the resistivity of the land was assumed to be uniform and its value was determined to be 200 , m by a simple one-parameter inversion. Overall agreements between the observations and the best-fit model responses indicated the importance of the 3-D coast effect in the target region. However, there remained significant discrepancies, especially in the phase of the responses, which provide a clue to determining a regional deep 3-D structure. [source]

    Changes in the timing of spring and autumn migration in North American migrant passerines during a period of global warming

    IBIS, Issue 2 2005
    Butler (2003) used first arrival dates (FADs) of 103 migrant birds in northeastern USA and found that both long-distance migrants (LDMs; wintering south of the USA) and short-distance migrants (SDMs; wintering in the southern USA) arrived earlier in the second half of the 20th century than they had in the first, consistent with scenarios of global warming; the trend was stronger in SDMs. Using FADs to characterize migration systems can be problematic because they are data from one tail of a distribution, they comprise a mostly male population and they may not correlate well with the balance of the migration period. FADs also provide no information about autumn migration. This paper uses a banding dataset from Long Point Bird Observatory, Ontario, for 14 passerines for a period of global warming (1975,2000), taking these issues into account. The data were filtered to minimize effects of unequal netting effort (147 491 resulting records), and the passage dates then calculated in each season of each year for the 1st, 2nd and 3rd quartiles for regression analysis. Only two of 13 species analysed in the spring showed significantly earlier passage times, although the overall trend was towards earlier spring migration, especially among SDMs. Autumn responses were more prevalent, however, and in some cases more dramatic with six of 13 species showing delayed migration (four SDMs, two LDMs). Two LDMs exhibited earlier autumn migration. Where earlier spring migration occurred, both sexes appeared to contribute to the change. Where delayed migration occurred in autumn, both sexes and both adults and hatch-year birds appeared to contribute in at least some cases. The spring FAD results are consistent with those of Butler, but when the whole migration is considered, change is far from universal in spring and is in fact more substantial and complex in autumn. [source]

    Air temperatures at Armagh Observatory, Northern Ireland, from 1796 to 2002

    C. J. Butler
    Abstract Three independent mean temperature series for Armagh Observatory, covering the period 1796,2002 have been calibrated and corrected for the time of reading and exposure. Agreement between the three series is good in regions of overlap. With a short gap in the Armagh data from 1825 to 1833 filled by data from two stations in Dublin, the resulting series is the longest for the island of Ireland and one of the longest for any single site in the British Isles. Over the past 207 years, we note that temperatures in Armagh, in all seasons, show a gradual overall trend upwards. However, there are seasonal differences: summer and spring temperatures have increased by only half as much as those in autumn and winter. This is partly due to the exceptionally cold winters and autumns experienced prior to 1820. Relative to the overall trend, warm periods occurred in Ireland, as in other parts of Europe, in the mid-19th century, in the mid-20th century and at the end of the 20th century. Relatively cool temperatures prevailed in the early 19th century, in the 1880s and in the 1970s. Thus, if the baseline against which current temperatures are compared were moved from the late 19th century to include the earlier warm period, the apparent warming at the end of the late 20th century would be correspondingly reduced. A gradual decline in the daily temperature range at Armagh since 1844 may have resulted from higher minimum temperatures associated with increased cloudiness. A 7.8 year periodicity is identified in winter and spring mean temperatures at Armagh, which is probably a consequence of the North Atlantic oscillation. Copyright © 2005 Royal Meteorological Society [source]

    A predictive model for psychological reactions to crime in Italy: an analysis of fear of crime and concern about crime as a social problem

    Piero Amerio
    Abstract In this study a model for predicting fear of crime (FC) and concern about crime as a social problem (CC) in Italy has been built, using three sets of independent variables concerning: (a) the sociodemographic and criminal victimization domain; (b) the psychosocial domain; and (c) the mass media. A secondary analysis on data gathered by the Observatory of the North-West (N,=,3262, a mail panel that is representative of the Italian population over 18) has been performed. Results showed that FC and CC are related yet distinct constructs: FC is less widespread than CC, and has different predictors. FC predictors are sociodemographic, psychosocial and, above all, victimization variables; whereas mass media and psychosocial variables predict CC. Results were compared with the literature on the topic. Implications, limitations, and future directions are discussed. Copyright © 2004 John Wiley & Sons, Ltd. [source]

    How long does victimization foster fear of crime?

    A longitudinal study
    We studied the relationship between victimization and fear of crime longitudinally, analyzing data from the Observatory of the North-West (Italian national sample, N=1,701, two waves: January 2006 and January 2007). We modeled fear of crime at T2 using as independent variables: (a) the main sociodemographic variables and fear of crime, as assessed at T1; (b) direct victimization; and (c) indirect victimization. Recent direct victimization was the most effective victimization predictor of both concrete and abstract fears, followed by multiple or repeat direct victimization. On the other hand, direct victimization occurring in the 12 months before the first wave did not influence fear. Recent indirect victimization and, above all, multiple or repeat indirect victimization influenced concrete, but not abstract, fear of crime, while direct victimization occurring in the 12 months before the first wave did not foster fear. We discuss the limits of this work and possible further directions. © 2010 Wiley Periodicals, Inc. [source]

    Within night correlations between radar and ground counts of migrating songbirds

    Michael L. Peckford
    ABSTRACT Studies comparing numbers of nocturnal migrants in flight with numbers of migrants at stopover sites have produced equivocal results. In 2003, we compared numbers of nocturnal migrants detected by radar to numbers of passerines observed at the Atlantic Bird Observatory in southwestern Nova Scotia, Canada. Numbers of nocturnal migrants detected by radar were positively correlated with numbers of migrants as determined by mist-netting, censuses, and daily estimated totals (daily estimates of birds present based netting and census results and casual observations) the following day. On nights with winds favorable for migration (tailwinds), the peak correlation between ground counts and radar counts the night before occurred just after sunset. On nights with unfavorable winds (headwinds), the correlation increased through the night, with a peak just before sunrise. The patterns of correlation are consistent with a scenario where birds accumulate at the coastline during periods of unfavorable wind, likely because they are not willing to cross a major ecological barrier, the Gulf of Maine. On nights with favorable winds, many birds departed, but some, possibly after testing wind conditions, apparently decided not to cross the Gulf of Maine and returned. Our results suggest that combining data collected using different methods to generate a daily estimated total provides the best estimate of the number of migrants present at a stopover site. Simultaneous studies at multiple locations where different census methods are used, making more effective use of temporal data (both from radar and diurnal counts), will more clearly elucidate patterns of flight behavior by migratory songbirds and the relationship between ground counts and counts of birds aloft. SINOPSIS Estudios cuales comparan los números de aves migratorias en vuelo durante la noche con los números de aves migratorias en sitios de reposo han producido resultados desiguales. En el 2003, comparamos los números de aves migratorias nocturnas detectadas por radar con los números de aves de Passeriformes observadas en el Atlantic Bird Observatory en el sudoeste de Nueva Escocia, Canadá. Los números de aves migratorias detectadas por radar fueron positivamente correlacionados con los números de aves migratorias detectadas mediante la captura con redes de neblina, por censos y por estimaciones diarias totales (el número de aves migratorias basado en capturas, censos y observaciones no-estandarizadas) durante el próximo día. En noches con vientos favorables para la migración (vientos de cola), el punto máximo de la correlación entre los conteos hechos en la tierra con los conteos hechas mediante radar durante la noche anterior ocurrió justo después de la puesta del sol. En noches con vientos no-favorables para la migración (vientos de frente), la correlación incrementó durante la noche, con un punto máximo justo antes del amanecer. Los patrones de las correlaciones son consistentes con una situación en la cual las aves se acumulan sobre la costa del mar durante periodos de viento no-favorables, probablemente porque no están dispuestos a cruzar una barrera ecológica de mayor tamaño, cual es el Golfo de Maine. En noches con vientos favorables, muchas aves partieron, pero algunos, posiblemente después de probar las condiciones de viento, aparentemente decidieron no cruzar el Golfo de Maine y retornaron. Nuestros resultados sugieren que una combinación de datos colectados utilizando diferentes métodos para generar una estimación diaria total provee la mejor estimación del número de aves migratorias presentes en un sitio de reposo. Estudios simultáneos hechos en múltiples sitios donde diferentes métodos de censo son utilizados, realizando un uso mas efectivo de los datos tomados a través del tiempo (provenientes de conteos mediante radar así como de observadores durante el día), mostrarán mas claramente cuales son los patrones del vuelo de las aves migratorias y la relación entre los conteos hechos en la tierra y los conteos de aves en alto vuelo. [source]

    Epidemiology and clinical classification of onychomycosis

    I Effendy
    ABSTRACT Objectives, To review recent data , what is new in the epidemiology of onychomycoses? To identify the most relevant diagnostic criteria for effective therapy. Methods, The preliminary results of the European Onychomycosis Observatory (EUROO) study were analysed. In this international study, physicians completed questionnaires concerning patient profile and the disease. Results, One of the most interesting novel findings was that sampling requests were often not made [only 3.4% of general physicians (GPs) and 39.6% of dermatologists]. This means that no information about causative agent(s) was available, hindering appropriate treatment choice. Furthermore, contrary to previous findings, 70.7% of participants did not practice sports. Lastly, these preliminary findings showed that treatment strategy depends largely on the type of treating physician, with GPs preferring monotherapy and dermatologists preferring combination therapy. Conclusions, A consensus was reached that treatment strategy should depend on the severity of nail involvement and the causative fungus. It is thus important to promote the importance of sampling. To simplify the choice of an appropriate treatment, onychomycosis may be divided into just two clinical groups: onychomycosis with and without nail matrix area involvement. However, the distinct clinical findings (number and type of affected nails, multimorbidity, drug interaction, etc.) in each individual case must be taken into account to ensure an appropriate treatment decision. [source]

    Dynamic emission properties of pulsars B0943+10 and B1822,09 , I. Comparison, and the discovery of a ,Q'-mode precursor

    Isaac Backus
    ABSTRACT This paper reports new observations of pulsars B0943+10 and B1822,09 carried out with the Arecibo Observatory and the Giant Metrewave Radio Telescope, respectively. Both stars exhibit two stable emission modes. We report the discovery in B0943+10 of a highly linearly polarized ,precursor' (PC) component that occurs primarily in only one mode. This emission feature closely resembles B1822,09's PC which also occurs brightly in only one mode. B0943+10's other mode is well known for its highly regular drifting subpulses that are apparently produced by a rotating ,carousel' system of 20 ,beamlets.' Similarly, B1822,09 exhibits subpulse-modulation behaviour only in the mode where its PC is absent. We survey our 18 h of B0943+10 observations and find that the ,sideband'-modulation features, from which the carousel-rotation time can be directly determined, occur rarely , less than 5 per cent of the time , but always indicating 20 ,beamlets'. We present an analysis of B1822,09's modal modulation characteristics at 325 MHz and compare them in detail with B0943+10. The pulsar never seems to null, and we find a 43-rotation-period P3 feature in the star's ,Q' mode that modulates the interpulse (IP) as well as the conal features in the main pulse (MP). We conclude that B1822,09 must have a nearly orthogonal geometry and that its carousel circulation time is long compared to the modal subsequences available in our observations, and the MP/IP separation is almost exactly 180°. We conclude the PCs for both stars are incompatible with core,cone emission. We assess the interesting suggestion by Dyks et al. that downward-going radiation produces B1822,09's PC emission. [source]

    Orbital and physical parameters of eclipsing binaries from the All-Sky Automated Survey catalogue , I. A sample of systems with components' masses between 1 and 2 M,

    K. G. He, miniak
    ABSTRACT We derive the absolute physical and orbital parameters for a sample of 18 detached eclipsing binaries from the All-Sky Automated Survey (ASAS) data base based on the available photometry and our own radial velocity (RV) measurements. The RVs are computed using spectra we collected with the 3.9-m Anglo-Australian Telescope (AAT) and its University College London Echelle Spectrograph (UCLES), and the 1.9-m Radcliffe telescope and its Grating Instrument for Radiation Analysis with a Fibre-Fed Echelle (GIRAFFE) at the South African Astronomical Observatory (SAAO). In order to obtain as precise RVs as possible, most of the systems were observed with an iodine cell available at the AAT/UCLES and/or analysed using the two-dimensional cross-correlation technique (TODCOR). The RVs were measured with TODCOR using synthetic template spectra as references. However, for two objects we used our own approach to the tomographic disentangling of the binary spectra to provide observed template spectra for the RV measurements and to improve the RV precision even more. For one of these binaries, AI Phe, we were able to the obtain an orbital solution with an RV rms of 62 and 24 m s,1 for the primary and secondary, respectively. For this system, the precision in M sin3i is 0.08 per cent. For the analysis, we used the photometry available in the ASAS data base. We combined the RV and light curves using phoebe and jktebop codes to obtain the absolute physical parameters of the systems. Having precise RVs, we were able to reach ,0.2 per cent precision (or better) in masses in several cases but in radii, due to the limited precision of the ASAS photometry, we were able to reach a precision of only 1 per cent in one case and 3,5 per cent in a few more cases. For the majority of our objects, the orbital and physical analysis is presented for the first time. [source]

    The Monitor project: rotation periods of low-mass stars in M50

    Jonathan Irwin
    ABSTRACT We report on the results of a time-series photometric survey of M50 (NGC 2323), a ,130 Myr open cluster, carried out using the Cerro Tololo Inter-American Observatory (CTIO) 4-m Blanco telescope and Mosaic-II detector as part of the Monitor project. Rotation periods were derived for 812 candidate cluster members over the mass range 0.2 ,M/M,, 1.1. The rotation period distributions show a clear mass-dependent morphology, statistically indistinguishable from those in NGC 2516 and M35 taken from the literature. Due to the availability of data from three observing runs separated by ,10 and 1 month time-scales, we are able to demonstrate clear evidence for evolution of the photometric amplitudes, and hence spot patterns, over the 10 month gap. We are not able to constrain the time-scales for these effects in detail due to limitations imposed by the large gaps in our sampling, which also prevent the use of the phase information. [source]

    E+A and companion galaxies , I. A catalogue and statistics

    Chisato Yamauchi
    ABSTRACT Based on our intensive spectroscopic campaign with the GoldCam spectrograph on the Kitt Peak National Observatory (KPNO) 2.1-m telescope, we have constructed the first catalogue of E+A galaxies with spectroscopic companion galaxies, and investigated a probability that an E+A galaxy has close companion galaxies. We selected 660 E+A galaxies with 4.0 Å < H, EW at a redshift of <0.167 from the Data Release 5 of the Sloan Digital Sky Survey (SDSS). We selected their companion candidates from the SDSS imaging data, and classified them into true companions, fore/background galaxies and companion candidates using the SDSS and our KPNO spectra. We observed 26 companion candidates of E+A galaxies at the KPNO to measure their redshifts. Their spectra showed that 17 targets are true companion galaxies. The number of spectroscopically confirmed E+A's companions is now 34. This becomes the first catalogue of E+A galaxies with spectroscopic companion systems. We found that E+A galaxies have 54 per cent larger probability of having companion galaxies (7.88 per cent) as compared to the comparison sample of normal galaxies (5.12 per cent). A statistical test shows that the probabilities are different with 99.7 per cent significance. Our results based on spectroscopy tighten the connection between the dynamical merger/interaction and the origin of E+A galaxies. [source]

    LOLAS: an optical turbulence profiler in the atmospheric boundary layer with extreme altitude resolution

    R. Avila
    ABSTRACT We report the development and first results of an instrument called Low Layer SCIDAR (Scintillation Detection and Ranging) (LOLAS) which is aimed at the measurement of optical-turbulence profiles in the atmospheric boundary layer with high altitude resolution. The method is based on the Generalized SCIDAR (GS) concept, but unlike the GS instruments which need a 1-m or larger telescope, LOLAS is implemented on a dedicated 40-cm telescope, making it an independent instrument. The system is designed for widely separated double-star targets, which enables the high altitude resolution. Using a 200-arcsec-separation double star, we have obtained turbulence profiles with unprecedented 12-m resolution. The system incorporates necessary novel algorithms for autoguiding, autofocus and image stabilization. The results presented here were obtained at Mauna Kea Observatory. They show LOLAS capabilities but cannot be considered as representative of the site. A forthcoming paper will be devoted to the site characterization. The instrument was built as part of the Ground Layer Turbulence Monitoring Campaign on Mauna Kea for Gemini Observatory. [source]

    Imaging and spectroscopy of ultrasteep spectrum radio sources,

    Carlos G. Bornancini
    ABSTRACT We present a sample of 40 ultrasteep spectrum (USS; ,,, 1.3, S,,,,) radio sources selected from the Westerbork in the Southern Hemisphere (WISH) catalogue. The USS sources have been imaged in K band at the Cerro Tololo Inter-American Observatory (CTIO) and with the Very Large Telescope (VLT) at Cerro Paranal. We also present VLT, Keck and William Herschel Telescope (WHT) optical spectroscopy of 14 targets selection from four different USS samples. For 12 sources, we have been able to determine the redshifts, including four new radio galaxies at z > 3. We find that most of our USS sources have predominantly small (<6 arcsec) radio sizes and faint magnitudes (K, 18). The mean K -band counterpart magnitude is . The expected redshift distribution estimated using the Hubble K,z diagram has a mean of , which is higher than the predicted redshift obtained for the Sydney University Molonglo Sky Survey,NRAO VLA Sky Survey (SUMSS,NVSS) sample and the expected redshift obtained in the 6C** survey. The compact USS sample analysed here may contain a higher fraction of galaxies which are high redshift and/or are heavily obscured by dust. Using the 74, 352 and 1400 MHz flux densities of a subsample, we construct a radio colour,colour diagram. We find that all but one of our USS sources have a strong tendency to flatten below 352 MHz. We also find that the highest redshift source from this paper (at z= 3.84) does not show evidence for spectral flattening down to 151 MHz. This suggests that very low frequency selected USS samples will likely be more efficient to find high redshift galaxies. [source]

    The NOAO Fundamental Plane Survey , III.

    Variations in the stellar populations of red-sequence galaxies from the cluster core to the virial radius
    ABSTRACT We analyse absorption line-strength indices for ,3000 red-sequence galaxies in 94 nearby clusters to investigate systematic variations of their stellar content with location in the host cluster. The data are drawn from the National Optical Astronomy Observatory (NOAO) Fundamental Plane Survey. Our adopted method is a generalization of that introduced by Nelan et al. to determine the global age,mass and metallicity,mass relations from the same survey. We find strong evidence for a change in galaxy properties, at fixed mass, over a range from the cluster centre to the virial radius, R200. For example, red-sequence galaxies further out in the clusters have weaker Mgb5177 (at ,8, significance) and stronger H, and H, absorption (,3,, ,4,) than galaxies of the same velocity dispersion in the cluster cores. The Fe5270 and Fe5335 indices show only very weak trends with radius. Using a total of 12 indices, the pattern of cluster-centric gradients is considered in light of their different dependences on stellar age and chemical composition. The measured gradients for all 12 indices can be reproduced by a model in which red-sequence galaxies at ,1 R200 have on average younger ages (by 15 ± 4 per cent) and lower ,-element abundance ratios (by 10 ± 2 per cent) than galaxies of the same velocity dispersion but located near the cluster centres. For the total metallicity, Z/H, no significant gradient is found (2 ± 3 per cent larger at R200 than in the cores). There are hints that the age trend may be stronger for galaxies of lower mass and/or for galaxies with more discy morphology. We show, however, that the trends cannot be driven primarily by changes in the morphological mix as a function of radius. The cluster-centric age and [,/Fe] gradients are in the sense expected if galaxies in the cluster core were accreted at an earlier epoch than those at larger radii, and if this earlier accretion contributed to an earlier cessation of star formation. The size of the observed age trend is comparable to predictions from semi-analytic models of hierarchical galaxy formation. [source]

    The 1,1000 ,m spectral energy distributions of far-infrared galaxies

    A. Sajina
    ABSTRACT Galaxies selected at 170 ,m by the Infrared Space Observatory (ISO) Far-IR BACKground (FIRBACK) survey represent the brightest ,10 per cent of the cosmic infrared background. Examining their nature in detail is therefore crucial for constraining models of galaxy evolution. Here, we combine Spitzer archival data with previous near-infrared (near-IR), far-IR, and submillimetre (submm) observations of a representative sample of 22 FIRBACK galaxies spanning three orders of magnitude in IR luminosity. We fit a flexible, multicomponent, empirical SED model of star-forming galaxies designed to model the entire ,1,1000 ,m wavelength range. The fits are performed with a Markov Chain Monte Carlo (MCMC) approach, allowing for meaningful uncertainties to be derived. This approach also highlights degeneracies such as between Td and ,, which we discuss in detail. From these fits and standard relations we derive: LIR, LPAH, star formation rate (SFR), ,V, M*, Mdust, Td, and ,. We look at a variety of correlations between these and combinations thereof in order to examine the physical nature of these galaxies. Our conclusions are supplemented by morphological examination of the sources, and comparison with local samples. We find the bulk of our sample to be consistent with fairly standard size and mass disc galaxies with somewhat enhanced star formation relative to local spirals, but likely not bona fide starbursts. A few higher- z luminous infrared galaxies (LIGs) and ultraluminous infrared galaxies (ULIGs) are also present, but contrary to expectation, they are weak mid-IR emitters and overall are consistent with star formation over an extended cold region rather than concentrated in the nuclear regions. We discuss the implications of this study for understanding populations detected at other wavelengths, such as the bright 850-,m Submillimetre Common-User Bolometer Array (SCUBA) sources or the faint Spitzer 24-,m sources. [source]

    GRS 1915+105: the distance, radiative processes and energy-dependent variability

    Andrzej A. Zdziarski
    ABSTRACT We present an exhaustive analysis of five broad-band observations of GRS 1915+105 in two variability states, , and ,, observed simultaneously by the Proportional Counter Array (PCA) and High-Energy X-ray Timing Experiment (HEXTE) detectors aboard the Rossi X-ray Timing Explorer, and the Oriented Scintillation Spectrometer Experiment (OSSE) detector aboard the Compton Gamma-ray Observatory. We find all the spectra well fitted by Comptonization of disc blackbody photons, with very strong evidence for the presence of a non-thermal electron component in the Comptonizing plasma. Both the energy and the power spectra in the , state are typical of the very high/intermediate state of black hole binaries. The spectrum of the , state is characterized by a strong blackbody component Comptonized by thermal electrons and a weak non-thermal tail. We then calculate rms spectra (fractional variability as functions of energy) for the PCA data. We accurately model the rms spectra by coherent superposition of variability in the components implied by the spectral fits, namely a less variable blackbody and more variable Comptonization. The latter dominates at high energies, resulting in a flattening of the rms at high energies in most of the data. This is also the case for the spectra of the quasi-periodic oscillations present in the , state. Then, some of our data require a radial dependence of the rms of the disc blackbody. We also study the distance to the source, and find d, 11 kpc as the most likely value, contrary to a recent claim of a much lower value. [source]

    Infrared mergers and infrared quasi-stellar objects with galactic winds , III.

    Mrk 231: an exploding young quasi-stellar object with composite outflow/broad absorption lines (and multiple expanding superbubbles)
    ABSTRACT We present a study of outflow (OF) and broad absorption line (BAL) systems in Mrk 231, and in similar infrared (IR) quasi-stellar objects (QSOs). This study is based mainly on one-dimensional and two-dimensional spectroscopy (obtained at La Palma/William Herschel Telescope, Hubble Space Telescope, International Ultraviolet Explorer, European Southern Observatory/New Technology Telescope, Kitt Peak National Observatory, Apache Point Observatory and Complejo Astronomico El Leoncito observatories) plus Hubble Space Telescope images. For Mrk 231, we report evidence that the extreme nuclear OF process has at least three main components on different scales, which are probably associated with: (i) the radio jet, at parsec scale; (ii) the extreme starburst at parsec and kiloparsec scale. This OF has generated at least four concentric expanding superbubbles and the BAL systems. Specifically, inside and very close to the nucleus the two-dimensional spectra show the presence of an OF emission bump in the blend H,+[N ii], with a peak at the same velocity of the main BAL-I system (VEjection BAL-I,,4700 km s,1). This bump was more clearly detected in the area located at 0.6,1.5 arcsec (490,1220 pc), to the south-west of the nucleus core, showing a strong and broad peak. In addition, in the same direction [at position angle (PA) ,,120°, i.e. close to the PA of the small-scale radio jet] at 1.7,2.5 arcsec, we also detected multiple narrow emission-line components, with ,greatly' enhanced [N ii]/H, ratio (very similar to the spectra of jets bow shocks). These results suggest that the BAL-I system is generated in OF clouds associated with the parsec-scale jet. The Hubble Space Telescope images show four (or possibly five) nuclear superbubbles or shells with radii r, 2.9, 1.5, 1.0, 0.6 and 0.2 kpc. For these bubbles, the two-dimensional H, velocity field map and two-dimensional spectra show the following. (i) At the border of the more extended bubble (S1), a clear expansion of the shell with blueshifted velocities (with circular shape and at a radius r, 5.0 arcsec). This bubble shows a rupture arc , to the south , suggesting that the bubble is in the blowout phase. The axis of this rupture or ejection (at PA , 00°) is coincident with the axis of the intermediate and large-scale structures detected at radio wavelengths. (ii) In addition, in the three more external bubbles (S1, S2, S3), the two-dimensional William Herschel Telescope spectra show multiple emission-line components with OF velocities, of ,VOF Bubble, S1, S2 and S3 =[,(650 , 420) ± 30], [,500 ± 30] and [,230 ± 30] km s,1. (iii) In the whole circumnuclear region (1.8 < r < 5 arcsec), the [N ii]/H, and [S ii]/H, narrow emission-line ratios show high values (>0.8), which are consistent with low-ionization nuclear emission-line region/OF processes associated with fast velocity shocks. Therefore, we suggest that these giant bubbles are associated with the large-scale nuclear OF component, which is generated , at least in part , by the extreme nuclear starburst: giant supernova/hypernova explosions. The variability of the short-lived BAL-III Na i D system was studied, covering almost all the period in which this system appeared (between ,1984 and 2004). We have found that the BAL-III light curve is clearly asymmetric with a steep increase, a clear maximum and an exponential fall (similar to the shape of a supernova light curve). The origin of this BAL-III system is discussed, mainly in the framework of an extreme explosive event, probably associated with giant supernova/hypernova explosions. Finally, the IR colour diagram and the ultraviolet BAL systems of IR + GW/OF + Fe ii QSOs are analysed. This study shows two new BAL IR QSOs and suggests/confirms that these objects could be nearby young BAL QSOs, similar to those detected recently at z, 6.0. We propose that the phase of young QSOs is associated with accretion of a large amount of gas (by the supermassive black hole) + extreme starbursts + extreme composite OFs/BALs. [source]

    A Chandra observation of the disturbed cluster core of Abell 2204

    J. S. Sanders
    ABSTRACT We present results from an observation of the luminous cluster of galaxies Abell 2204 using the Chandra X-ray Observatory. We show the core of the cluster has a complex morphological structure, made up of a high-density core (ne, 0.2 cm,3) with flat surface brightness, a surrounding central plateau, a tail-like feature, wrapping around to the east, and an unusual radio source. A temperature map and deprojected profile shows that the temperature rises steeply outside these regions, until around ,100 kpc where it drops, then rises again. Abundance maps and profiles show that there is a corresponding increase in abundance at the same radius as where the temperature drops. In addition, there are two cold fronts at radii of ,28 and 54.5 kpc. The disturbed morphology indicates that the cluster core may have undergone a merger. However, despite this disruption, the mean radiative cooling time in the centre is short (,230 Myr) and the morphology is regular on large scales. [source]

    Correlations between diffuse interstellar bands and atomic lines

    G. A. Galazutdinov
    ABSTRACT We present and discuss correlations between strengths of the well-known, strong interstellar atomic lines of K i and Ca ii, and four selected, strong unidentified diffuse interstellar bands (DIBs): 5780, 5797, 5850 and 6614. In order to analyse a homogeneous sample of echelle high-resolution spectra it has been chosen to use measurements from Terskol Observatory in Northern Caucasus plus a selected number of higher resolution observations performed using other instruments. We demonstrate that the strength of certain DIBs correlate well with neutral potassium lines and to a much lower degree with ionized calcium lines. This fact suggests that the degree of irradiation of a cloud with UV photons, capable to ionize interstellar atoms, plays a crucial role in the formation/maintenance of certain molecular species: possible carriers of DIBs. [source]

    The nature, evolution, clustering and X-ray properties of extremely red galaxies in the Chandra Deep Field South/Great Observatories Origins Deep Survey field

    Nathan D. Roche
    ABSTRACT We identify a very deep sample of 198 extremely red objects (EROs) in the Chandra Deep Field South, selected on the basis of I775,Ks > 3.92, to a limit Ks, 22 using the public European Southern Observatory (ESO)/Great Observatories Origins Deep Survey (GOODS) survey. The ERO number counts flatten from a slope of ,, 0.59 to 0.16 at K > 19.5, where they remain below the predictions for pure luminosity evolution, and fall below even a non-evolving model. This suggests there is a significant decrease with redshift in the comoving number density of passive/very red galaxies. We investigate the angular correlation function, ,(,), of these EROs and detect positive clustering for Ks= 20.5,22.0 sources. The EROs show stronger clustering than other galaxies at the same magnitudes. The ,(,) amplitudes are best-fitted by models in which the EROs have a comoving correlation radius r0, 12.5 ± 1.2 h,1 Mpc, or r0, 21.4 ± 2.0 h,1 Mpc in a stable clustering model. We find a 40-arcsec diameter overdensity of 10 EROs, centred on the Chandra X-ray source (and ERO) XID:58. On the basis of colours we estimate that about seven, including XID:58, belong to a cluster of EROs at z, 1.5. The 942-ks Chandra survey detected 73 X-ray sources in the area of our ERO sample, 17 of which coincide with EROs. Of these sources, 13 have X-ray properties indicative of obscured active galactic nuclei (AGN), while the faintest four may be starbursts. In addition, we find evidence that Chandra sources and EROs are positively cross-correlated at non-zero (,2,20 arcsec) separations, implying that they tend to trace the same large-scale structures. In conclusion, these findings appear consistent with a scenario where EROs are the z > 1 progenitors of elliptical/S0 galaxies, some forming very early as massive spheroids, which are strongly clustered and may evolve via an AGN phase, others more recently from mergers of disc galaxies. [source]

    GLITP optical monitoring of QSO 0957+561: VR light curves and variability

    A. Ullán
    ABSTRACT The Gravitational Lenses International Time Project (GLITP) collaboration observed the first gravitational lens system (QSO 0957+561) from 2000 February 3 to March 31. The daily VR observations were made with the 2.56-m Nordic Optical Telescope at Roque de los Muchachos Observatory, La Palma, Spain. We have derived detailed and robust VR light curves of the two components Q0957+561A and Q0957+561B. In spite of the excellent sampling rate, we have not found evidence in favour of true daily variability. With respect to variability on time-scales of several weeks, we measure VR gradients of about ,0.8 mmag d,1 in Q0957+561A and +0.3 mmag d,1 in Q0957+561B. The gradients are very probably originated in the far source. Thus, adopting this reasonable hypothesis (intrinsic variability), we compare them to the expected gradients during the evolution of a compact supernova remnant at the redshift of the source quasar. The starburst scenario is roughly consistent with some former events, but the new gradients do not seem to be caused by supernova remnant activity. [source]

    The space density of low-redshift active galactic nuclei

    D. Londish
    We present a new determination of the optical luminosity function (OLF) of active galactic nuclei (AGN) at low redshifts (z<0.15) based on Hubble Space Telescope (HST) observations of X-ray-selected AGN. The HST observations have allowed us to derive a true nuclear luminosity function for these AGN. The resulting OLF illustrates a two power-law form similar to that derived for quasi-stellar objects (QSOs) at higher redshifts. At bright magnitudes, MB<,20, the OLF derived here exhibits good agreement with that derived from the Hamburg/European Southern Observatory (ESO) QSO survey. However, the single power-law form for the OLF derived from the Hamburg/ESO survey is strongly ruled out by our data at MB>,20. Although the estimate of the OLF is best fitted by a power-law slope at MB<,20.5 that is flatter than the slope of the OLF derived at z>0.35, the binned estimate of the low-redshift OLF is still consistent with an extrapolation of the z>0.35 OLF based on pure luminosity evolution. [source]

    H2 reformation in post-shock regions

    H. M. Cuppen
    ABSTRACT H2 formation is an important process in post-shock regions, since H2 is an active participant in the cooling and shielding of the environment. The onset of H2 formation therefore has a strong effect on the temperature and chemical evolution in the post-shock regions. We recently developed a model for H2 formation on a graphite surface in warm conditions. The graphite surface acts as a model system for grains containing large areas of polycyclic aromatic hydrocarbon structures. Here, this model is used to obtain a new description of the H2 formation rate as a function of gas temperature that can be implemented in molecular shock models. The H2 formation rate is substantially higher at high gas temperatures as compared to the original implementation of this rate in shock models, because of the introduction of H atoms which are chemically bonded to the grain (chemisorption). Since H2 plays such a key role in the cooling, the increased rate is found to have a substantial effect on the predicted line fluxes of an important coolant in dissociative shocks [O i] at 63.2 and 145.5 ,m. With the new model, a better agreement between the model and observations is obtained. Since one of the goals of Herschel/PACS will be to observe these lines with higher spatial resolution and sensitivity than the former observations by Infrared Space Observatory -LWS, this more accurate model is very timely to help with the interpretation of these future results. [source]

    SDSS J150634.27+013331.6: the second compact elliptical galaxy in the NGC 5846 group,

    Igor V. Chilingarian
    ABSTRACT We report the discovery of the second compact elliptical (cE) galaxy SDSS J150634.27+013331.6 in the nearby NGC 5846 group by the Virtual Observatory (VO) workflow. This object (MB=,15.98 mag, Re= 0.24 kpc) becomes the fifth cE where the spatially resolved kinematics and stellar populations can be obtained. We used archival HST WFPC2 images to demonstrate that its light profile has a two-component structure, and integrated photometry from GALEX, SDSS, UKIDSS and Spitzer to build the multiwavelength spectral energy distribution to constrain the star formation history (SFH). We observed this galaxy with the PMAS IFU spectrograph at the Calar-Alto 3.5-m telescope and obtained two-dimensional maps of its kinematics and stellar population properties using the full-spectral fitting technique. Its structural, dynamical and stellar population properties suggest that it had a massive progenitor heavily tidally stripped by NGC 5846. [source]

    On active galactic nuclei as sources of ultra-high energy cosmic rays

    M. R. George
    ABSTRACT We measure the correlation between sky coordinates of the Swift Burst Alert Telescope (BAT) catalogue of active galactic nuclei (AGN) with the arrival directions of the highest energy cosmic rays detected by the Auger Observatory. The statistically complete, hard X-ray catalogue helps to distinguish between AGN and other source candidates that follow the distribution of local large-scale structure. The positions of the full catalogue are marginally uncorrelated with the cosmic ray arrival directions, but when weighted by their hard X-ray flux, AGN within 100 Mpc are correlated at a significance level of 98 per cent. This correlation sharply decreases for sources beyond ,100 Mpc, suggestive of a GZK suppression. We discuss the implications for determining the mechanism that accelerates particles to these extreme energies in excess of 1019 eV. [source]