Primordial non-Gaussianity from LAMOST surveys

The primordial non-Gaussianity (PNG) in the matter density perturbation is a very powerful probe of the physics of the very early Universe. The local PNG can induce a distinct scale-dependent bias on the large scale structure distribution of galaxies and quasars, which could be used for constraining it. We study the detection limits of PNG from the surveys of the LAMOST telescope. The cases of the main galaxy survey, the luminous red galaxy (LRG) survey, and the quasar survey of dif- ferent magnitude limits...     

Intraspecific cleaning by juvenile Cape white seabream Diplodus capensis (Sparidae) off eastern South Africa

Juveniles of the Cape white seabream Diplodus capensis were observed cleaning adult conspecifics in a large tidepool off Sodwana Bay, South Africa. Although nine other tropical fish species were present and interacted with a nearby pair of Labroides cleaner wrasses, only adults of D. capensis posed for and were cleaned by the D. capensis juveniles. Such cleaning interactions have not been reported previously for this species or among marine fishes off South Africa, and thus add to the growing list of facultative cleaners globally.     

A hard X-ray telescope/concentrator design based on graded period multilayer coatings

It is shown that compact designs of multifocus, conical approximations to highly nested Wolter I telescopes, as well as single reflection concentrators, employing realistic graded period W/Si or Ni/C multilayer coatings, allow one to obtain more than 1000 cm² of on-axis effective area at 40 keV and up to 200 cm² at 100 keV. The degree of concentration is defined by a focusing factor i.e., the effective area divided by the half power focal area. For the cases studied, this is 400 at 40 keV and 200 at 100 keV for a 2 arcmin imaging resolution. This result is quite insensitive to the specifics of the telescope configuration provided that mirrors can be coated to an inner radius of 3 cm. Specifically we find that a change of focal length from 5 to 12 m affects the effective area by less than 10%. In addition the result is insensitive to the thickness of the individual mirror shell provided that it is smaller than roughly 1 mm. The design can be realized with foils as thin (0.4 mm) as used for ASCA and SODART or with closed, slightly thicker (1.0 mm) mirror shells as used for JET-X and XMM. The effect of an increase of the inner radius is quantified on the effective area for multilayered mirrors up to 9 cm. The calculated Field of View (full width at half maximum), ranges from 9 arcmin at 1 keV to 5 arcmin at 60 keV. Finally, the continuum sensitivity of the design assuming a signal to noise ratio of 5 and a 10% energy bandwidth has been calculated. For a balloon flight observation of 10⁴ sec. with a telescope having 2 arcmin imaging resolution the point source sensitivity is 3 · 10^–6 photons/cm²/s/keV up to 70 keV for a W/Si coated telescope and up to 100 keV for a Ni/C coated telescope. For a satellite observation time of 10⁵ sec and an imaging resolution of 1 arcmin the sensitivity is 10^–7 photons/cm²/s/keV which demonstrates the great potential of this hard X-ray imaging telescope in the energy range up to 100 keV.     

The CZT X-ray Imager on AXO

DSRI has initiated a development program of CZT X-ray and gamma raydetectors employing strip readout techniques. A dramatic improvement ofthe energy response was found operating the detectors as so-called driftdetectors. For the electronic readout, modern ASIC chips wereinvestigated. Modular design and the low power electronics will make largearea detectors using the drift strip method feasible. The performance of aprototype CZT system will be presented and discussed. One such detector system has been proposed for future space missions: TheX-Ray Imager (XRI) on the Atmospheric X-ray Observatory (AXO), whichis a mission proposed to the Danish Small Satellite Program and is dedicatedto observations of X-ray generating processes in the Earth's atmosphere. Ofspecial interest will be simultaneous optical and X-ray observations of spritesthat are flashes appearing directly above an active thunderstorm system.Additional objective is a detailed mapping of the auroral X-ray and opticalemission. XRI comprises a coded mask and a 20 cm × 40 cm CZTdetector array covering an energy range from 5 to 200 keV.     

Phylogeny of the Sepia officinalis species complex in the eastern Atlantic extends the known distribution of Sepia vermiculata across the Benguela upwelling region

Accurate species identification and biogeographic characterisation are fundamental for appropriate management of expanding cephalopod fisheries. This study addresses this topic within the common cuttlefish Sepia officinalis species complex (S. officinalis, S. hierredda and S. vermiculata), with an emphasis on occurrence in African waters. Tissue samples from the currently presumed distributions of S. vermiculata and S. hierredda (from South Africa and Ghana/Angola, respectively) were sequenced for the cytochrome c oxidase subunit I (COI) and the cytochrome b (cytb) genes of the mitochondrial genome and then compared to existing S. officinalis sequences. Three highly divergent and reciprocally monophyletic clades, corresponding to S. officinalis, S. hierredda and S. vermiculata, were resolved, representing the first molecular confirmation of the distinct species status of S. hierredda and S. vermiculata. The sequences also revealed that, contrary to expectations based on presently published information, all samples from southern Angola were S. vermiculata. These results indicate that the range of S. vermiculata extends beyond the currently described northern limit and that S. hierredda and S. vermiculata may be indiscriminately harvested in Angolan waters. Finer-scale patterns within S. vermiculata phylogeography also indicate that the Benguela Current System and/or other environmental factors serve to isolate northern and southern stocks.     

Photo's from Proceedings of the Third MicroQuasar Workshop; Granada Worshop on Galactic Relativistic Jet Sources – Granada,Spain, 11–13 September 2000

The X-Ray Spectroscopic Explorer (XRASE) has a unique combination of features that will make it possible to address many of NASA's scientific goals. These include how galaxy clusters form, the physics and chemistry of the ISM, the heating of stellar coronae, the amount and content of intergalactic baryonic matter, the mass of black holes and the formation of disks and jets in AGN and galactic binaries. XRASE has a thin foil, multilayered telescope with a large collecting area up to 10 keV, especially in the Fe K region (1100 cm²). Its microcalorimeter array combines high energy resolution (7 eV at 6 keV) and efficiency with a field-of-view of 26 arcmin² . A deep orbit allows for long, continuous observations. Monitoring instruments in the optical (WOM-X), UV (TAUVEX) and hard X-RAY (GRAM) bands will offer exceptional opportunities to make simultaneous multi-wavelength observations.     

Observing the reconnection region in a transequatorial loop system

A vertical current sheet is a crucial element in many flare/coronal mass ejection (CME) models. For the first time, Liu et al. reported a vertical current sheet directly imaged during the flare rising phase with the EUV Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SOHO). As a follow-up study, here we present the comprehensive analysis and detailed physical interpretation of the observation. The current sheet formed due to the gradual rise of a transequatorial loop system. As the l...     

Dusky dolphin movement patterns: short-term effects of tourism

Cetacean-oriented tourism has experienced rapid growth in the last two decades, accompanied by increasing concerns about the effects of tourism on target species. Here, we used shore-based observations of dusky dolphin (Lagenorhynchus obscurus) groups near Kaikoura, New Zealand, and generalised additive models to quantify changes in group speed, reorientation and linearity relative to natural and anthropogenic factors. Summer months were characterised by slower speeds and more changes in direction than winter months. Group speeds were higher at the beginning and end of the day, with slower speeds at midday. Speeds were slower when vessels were present, and dolphin groups changed direction more often when aircraft circled overhead. Effects were positively correlated with number of vessels present within 300 m. Short-term changes have potential to lead to long-term impacts, and further acoustic and energetic studies are proposed to elucidate whether these effects are likely to reduce individual fitness.     

Soft X-ray Focusing Telescope Aboard AstroSat: Design,Characteristics and Performance

The Soft X-ray focusing Telescope (SXT), India’s first X-ray telescope based on the principle of grazing incidence, was launched aboard the AstroSat and made operational on October 26, 2015. X-rays in the energy band of 0.3–8.0 keV are focussed on to a cooled charge coupled device thus providing medium resolution X-ray spectroscopy of cosmic X-ray sources of various types. It is the most sensitive X-ray instrument aboard the AstroSat. In its first year of operation, SXT has been used to observe objects ranging from active stars, compact binaries, supernova remnants, active galactic nuclei and clusters of galaxies in order to study its performance and quantify its characteriztics. Here, we present an overview of its design, mechanical hardware, electronics, data modes, observational constraints, pipeline processing and its in-orbit performance based on preliminary results from its characterization during the performance verification phase.     

Electrons in a closed galaxy model of cosmic rays

We consider the consistency of positrons and electrons with a propagation model in which the cosmic rays are stopped by nuclear collisions or energy losses before they can escape from the Galaxy (the closed-galaxy model). The fact that we find no inconsistency between the predictions and the data implies that the protons which produce the positrons by nuclear reactions could have their origin in a large number of distant sources, as opposed to the heavier nuclei which in this model come from a more limited set of sources. The closed-galaxy model predicts steep electron and positron spectra at high energies. None of these are inconsistent with present measurements; but future measurements of the spectrum of high-energy positrons could provide a definite test for the model. The closed-galaxy model also predicts that the interstellar electron intensity below a few GeV is larger than that implied by other models. The consequence of this result is that electron brems-strahlung is responsible for about 50% of the galactic gamma-ray emission at photon energies greater than 100 MeV.