Measuring the impact of observations on the predictability of the Kuroshio Extension in a shallow-water model

In this paper sequential importance sampling is used to assess the impact of observations on a ensemble prediction for the decadal path transitions of the Kuroshio Extension (KE). This particle filtering approach gives access to the probability density of the state vector, which allows us to determine the predictive power — an entropy based measure — of the ensemble prediction. The proposed set-up makes use of an ensemble that, at each time, samples the climatological probability distribution. Then, in a post-processing step, the impact of different sets of observations is measured by the increase in predictive power of the ensemble over the climatological signal during one-year. The method is applied in an identical-twin experiment for the Kuroshio Extension using a reduced-gravity shallow water model. We investigate the impact of assimilating velocity observations from different locations during the elongated and the contracted meandering state of the KE. Optimal observations location correspond to regions with strong potential vorticity gradients. For the elongated state the optimal location is in the first meander of the KE. During the contracted state of the KE it is located south of Japan, where the Kuroshio separates from the coast

Dust Attenuation in Late-Type Galaxies. I. Effects on Bulge and Disk Components

We present results of new Monte Carlo calculations made with the DIRTY code of radiative transfer of stellar and scattered radiation for a dusty giant late-type galaxy like the Milky Way, which illustrate the effect of the attenuation of stellar light by internal dust on the integrated photometry of the individual bulge and disk components. Here we focus on the behavior of the attenuation function, the color excess, and the fraction of light scattered or directly transmitted towards the outside observer as a function of the total amount of dust and the inclination of the galaxy, and the structure of the dusty interstellar medium (ISM) of the disk. We confirm that dust attenuation produces qualitatively and quantitatively different effects on the integrated photometry of bulge and disk, whatever the wavelength. In addition, we find that the structure of the dusty ISM affects more sensitively the observed magnitudes than the observed colors of both bulge and disk. Finally, we show that the contribution of the scattered radiation to the total monochromatic light received by the outside observer is significant, particularly at UV wavelengths, even for a two-phase, clumpy, dusty ISM. Thus understanding dust scattering properties is fundamental for the interpretation of extragalactic observations in the rest-frame UV.Comment: 62 pages, 28 eps-figures, 1 table, accepted for publication in ApJ Main Journa

Quaternary marine and continental unconformity-bounded stratigraphic units of the NW Sicily coastal belt

In the coastal sector of NW Sicily, the regional correlation of relevant unconformities recognised within the Quaternary sedimentary successions allowed the mapping of seven unconformitybounded stratigraphic units (UBSUs). The regional unconformities are marine or subaerial erosional surfaces, as well as non-depositional surfaces, locally marked by paleosoils. The erosional surfaces were produced from marine abrasion, surface water overland/ concentrated flow, river erosion, karst solution, mass movement, or wind erosion. The main lithofacies of the Quaternary UBSUs consist of: (a) marine and coastal bioclastic calcarenites, (b) aeolian sandstones, (c) river deposits, (d) colluvial deposits, (e) talus slope deposits, (f) landslide deposits, and (g) chemical carbonates (travertines and speleothems). Quaternary environmental changes, due to tectonics, climate, and sea-level oscillations, are the causes that favoured the development of erosion/deposition processes responsible for the genesis of unconformities and deposits. As a result, through the UBSU map of the NW Sicilian coastal belt, it is possible to: (i) recognise stratigraphic units controlled by tectonic, climatic, and environmental processes (and their interplay) and (ii) detect Quaternary sedimentary evolution

Recent star formation in clusters of galaxies: extreme compact starbursts in A539 and A634

We report on the detection of two Halpha-emitting extreme compact objects from deep images of the Abell 634 and Abell 539 clusters of galaxies at z ~ 0.03. Follow up long slit spectroscopy of these two unresolved sources revealed that they are members of their respective clusters showing HII type spectra. The luminosity and the extreme equivalent width of Halpha+[NII] measured for these sources, together with their very compact appearance, has raised the question about the origin of these intense starbursts in the cluster environment. We propose the compact starburst in Abell 539 resulted from the compression of the interstellar gas of a dwarf galaxy when entering the cluster core; while the starburst galaxy in Abell 634 is likely to be the result of a galaxy-galaxy interaction, illustrating the preprocessing of galaxies during their infall towards the central regions of clusters. The contribution of these compact star-forming dwarf galaxies to the star formation history of galaxy clusters is discussed, as well as a possible link with the recently discovered early-type ultra-compact dwarf galaxies. We note that these extreme objects will be rarely detected in normal magnitude-limited optical or NIR surveys, mainly due to their low stellar masses (of the order of 10^6 solar masses), whereas they will easily show up in dedicated Halpha surveys given the high equivalent width of their emission lines.Comment: Accepted for publication in the Astronomical Journal. 31 pages, 10 fig

XMM-Newton detection of two clusters of galaxies with strong SPT Sunyaev-Zel'dovich effect signatures

We report on the discovery of two galaxy clusters, SPT-CL J2332-5358 and SPT-CL J2342-5411, in X-rays. These clusters were also independently detected through their Sunyaev-Zel'dovich effect by the South Pole Telescope, and confirmed in the optical band by the Blanco Cosmology Survey. They are thus the first clusters detected under survey conditions by all major cluster search approaches. The X-ray detection is made within the frame of the XMM-BCS cluster survey utilizing a novel XMM-Newton mosaic mode of observations. The present study makes the first scientific use of this operation mode. We estimate the X-ray spectroscopic temperature of SPT-CL J2332-5358 (at redshift z=0.32) to T = 9.3 (+3.3/-1.9) keV, implying a high mass, M_{500} = 8.8 +/- 3.8 \times 10^{14} M_{sun}. For SPT-CL J2342-5411, at z=1.08, the available X-ray data doesn't allow us to directly estimate the temperature with good confidence. However, using our measured luminosity and scaling relations we estimate that T = 4.5 +/- 1.3 keV and M_{500} = 1.9 +/- 0.8 \times 10^{14} M_{sun}. We find a good agreement between the X-ray masses and those estimated from the Sunyaev-Zel'dovich effect.Comment: Submitted to A&A, 8 pages, 5 figures, 1 tabl

Quasar Feedback: the Missing Link in Structure Formation

We consider the impact of quasar outflows on structure formation. Such outflows are potentially more important than galactic winds, which appear insufficient to produce the level of preheating inferred from X-ray observations of galaxy clusters. Using a simple analytical model for the distribution of quasars with redshift, coupled with a one-dimensional Sedov-Taylor model for outflows, we are able to make robust statements about their impact of on structure formation. As large regions of the IGM are heated above a critical entropy of approximately 100 keV cm^2, cooling become impossible within them, regardless of changes in density. On quasar scales, this has the effect of inhibiting further formation, resulting in the observed fall-off in their number densities below z = 2. On galaxy scales, quasar feedback fixes the turn-over scale in the galaxy luminosity function (L_*) as the nonlinear scale at the redshift of strong feedback. The galaxy luminosity function then remains largely fixed after this epoch, consistent with recent observations and in contrast to the strong evolution predicted in more standard galaxy-formation models. Finally, strong quasar feedback explains why the intracluster medium is observed to have been pre-heated to entropy levels just above S_crit, the minimum excess that would not have been erased by cooling. The presence of such outflows is completely consistent with the observed properties of the Lyman-alpha forest at z ~ 2, but is expected to have a substantial and detectable impact on Compton distortions observed in the microwave background and the multiphase properties of the "warm-hot" (z=0) circumgalactic medium.Comment: 20 pages, 11 figures, ApJ, accepted (minor changes made, two plots updated

PACS photometry of the Herschel Reference Survey - Far-infrared/sub-millimeter colours as tracers of dust properties in nearby galaxies

We present Herschel/PACS 100 and 160 micron integrated photometry for the 323 galaxies in the Herschel Reference Survey (HRS), a K-band-, volume-limited sample of galaxies in the local Universe. Once combined with the Herschel/SPIRE observations already available, these data make the HRS the largest representative sample of nearby galaxies with homogeneous coverage across the 100-500 micron wavelength range. In this paper, we take advantage of this unique dataset to investigate the properties and shape of the far-infrared/sub-millimeter spectral energy distribution in nearby galaxies. We show that, in the stellar mass range covered by the HRS (8<log(M*/Msun)<12), the far-infrared/sub-millimeter colours are inconsistent with a single modified black-body having the same dust emissivity index beta for all galaxies. In particular, either beta decreases, or multiple temperature components are needed, when moving from metal-rich/gas-poor to metal-poor/gas-rich galaxies. We thus investigate how the dust temperature and mass obtained from a single modified black-body depend on the assumptions made on beta. We show that, while the correlations between dust temperature, galaxy structure and star formation rate are strongly model dependent, the dust mass scaling relations are much more reliable, and variations of beta only change the strength of the observed trends.Comment: 26 pages, 8 figures, 2 tables. Accepted for publication in MNRA

Marine Mammals and Megafauna in Irish Waters - Behaviour, Distribution and Habitat Use- WP 2: Developing Acoustic Monitoring Techniques

*Lead Partner: Galway-Mayo Institute of Technology *Project Partners: Irish Whale and Dolphin Group *Author(s): O’Brien, J., Beck, S., Wall, D. and Pierini, A. *Contributors: Joanne O’Brien, Suzanne Beck, Dave Wall, Sophie Hansen, Alessandro Pierini, Simon Berrow, Barry McGovern, Ian O’Connor and Dave McGrath. *Project Duration: 01 February 2008 to 31 August 2011All cetaceans and their habitats are protected under Irish and international law. The research termed Marine Mammals and Megafauna in Irish Waters – behaviour, distribution and habitat use was delivered under six Work Packages. Cetacean line transect surveys were conducted under Work Package 1 with the following goals: 1. Providing a baseline cetacean distribution and relative abundance data set for the Irish EEZ; 2. Filling spatial and temporal gaps identified in cetacean survey effort within the EEZ; 3. Preparing an Atlas of cetacean distribution and relative abundance for Irish waters; 4. Assessing the temporal use of marine habitats by cetaceans in Irish waters.This project (Grant Aid Agreement No. PBA/ME/07/005(02)) was carried out under the Sea Change Strategy with the support of the Marine Institute and the Marine Research Sub-Programme of the National Development Plan 2007–2013, and through funding from the Department of Arts, Heritage and the Gaeltacht.Funder: Marine Institut