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101.
The extremely red galaxies (ERGs) are defined in terms of their very red optical-to-near IR colours (as R − K >5 or I − K >4). Originally this selection was aimed at selecting old (>1 Gyr) passively evolving elliptical galaxies at intermediate redshift (1< z <2), but it was soon discovered that young star-forming dusty galaxies can show similar colours and therefore be selected in the same surveys. It is crucial to distinguish between these two populations because they have very different consequences on the models of galaxy formation. Here we show that old ellipticals and dusty starbursts are expected to show different colours in the ( I − K ) versus ( J − K ) diagram for redshift range 1< z <2, thus providing a useful tool to classify ERGs in large samples up to K <20. This is mainly owing to the fact that old galaxies at these redshifts have a strong 4000-Å break at λ <1.2 μm ( J band), while dusty galaxies show smoother spectral energy distributions and therefore redder J − K colours. We discuss this difference in detail both in the framework of the stellar population synthesis models and by using observed spectra. The selection criterion is also compared with the properties of ERGs of known nature. We also show that this colour selection criterion is also useful to separate the ERGs from brown dwarf stars showing similar optical-to-IR colours. 相似文献
102.
V. D'Odorico G. Cupani S. Cristiani R. Maiolino P. Molaro M. Nonino A. Cimatti S. di Serego Alighieri F. Fiore A. Fontana S. Gallerani E. Giallongo F. Mannucci A. Marconi L. Pentericci M. Viel G. Vladilo 《Astronomische Nachrichten》2011,332(3):315-318
X‐shooter, with its characteristics of resolution, spectral coverage and efficiency, provides a unique opportunity to obtain spectra of the highest‐redshift quasars (z ∼ 6) that will allow us to carry out successful investigations on key cosmological issues, from the details of the re‐ionization process, to the evolution of the first galaxies and AGNs. In this paper, we present the spectra of three z ∼ 6 quasars: one obtained during the commissioning of X‐shooter and two in the context of our ongoing GTO programme. Combining this sample with data in the literature, we update the value of the C IV cosmic mass density in the range 4.5 ≤ z ≤ 5, confirming the constant trend with redshift between 2.5 and 5 (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
103.
Exhumation of the Dora Maira ultrahigh‐pressure unit by buoyant uprise within a low‐viscosity mantle oblique‐slip shear zone 下载免费PDF全文
The Brossasco‐Isasca subunit (BIU) of the Dora Maira massif is currently the only known continental crustal ultrahigh‐pressure (UHP) unit in the Western Alps. The peak pressure/temperature conditions are 3.5–4.5 GPa/~730 °C; exhumation from ~3.5 GPa to ~1 GPa occurred within 2.2 ± 1.8 Ma, but the exhumation mechanism is incompletely understood. We present a conceptual model for the buoyancy‐driven exhumation of the BIU inside a low‐viscosity, dense mantle shear zone weakened by increased strain rates due to simultaneous strike‐slip and subduction (oblique‐slip) of the European plate. Two‐dimensional thermo‐mechanical models simulate such a buoyant uprise of an ellipse inside an inclined layer. Simulations (i) show the feasibility of the conceptual model, (ii) fit the pressure/temperature/time record and (iii) constrain effective viscosities. The model is compatible with the (i) small volume of continental crustal UHP rock in the Western Alps, (ii) minor erosion during exhumation and (iii) strike‐slip deformation during the exhumation period. 相似文献
104.
Flooding scenarios due to land subsidence and sea‐level rise: a case study for Lipari Island (Italy) 下载免费PDF全文
Marco Anzidei Alessandro Bosman Roberto Carluccio Daniele Casalbore Francesca D'Ajello Caracciolo Alessandra Esposito Iacopo Nicolosi Grazia Pietrantonio Antonio Vecchio Cosmo Carmisciano Massimo Chiappini Francesco Latino Chiocci Filippo Muccini Vincenzo Sepe 《地学学报》2017,29(1):44-51
Archaeological and instrumental data indicate that the southern sector of the volcanic island of Lipari has been subsiding for the last 2100 years due to isostatic and tectonic factors, at variable rates of up to ~11 mm a?1. Based on this data, a detailed marine flooding scenario for 2100 AD is provided for the bay of Marina Lunga in the eastern part of the island from (1) an ultra‐high‐resolution Digital Terrain and Marine Model (DTMM) generated from multibeam bathymetry (MB) and Unmanned Aerial Vehicles (UAV), (2) the rate of land subsidence from Global Positioning System (GPS) data and (3) the regional sea‐level projections of the International Panel on Climate Change (IPCC). When land subsidence is considered, the upper bound of sea‐level rise is estimated at 1.36 m and 1.60 m for RCP4.5 and RCP8.5 climate change scenarios, respectively. Here, we show the expected impact of marine flooding at Lipari for the next 85 years and discuss the hazard implications for the population living along the shore. 相似文献
105.
Rosalba Napoli Gilda Currenti Ciro Del Negro Agnese Di Stefano Filippo Greco Enzo Boschi 《Bulletin of Volcanology》2011,73(9):1311-1322
Significant changes in the local magnetic field marked the resumption of eruptive activity at Stromboli volcano on February
27, 2007. After differential magnetic fields were obtained by filtering out external noise using adaptive filters and seasonal
thermal noise using temperature data, we identified step-like changes of 1–4 nT coincident with the opening of eruptive fissures
in the upper part of the Sciara del Fuoco. The magnetic variations detected at two stations are closely related to the propagation
of a shallow NE–SW magmatic intrusion extending beyond the summit craters area. These observations are consistent with those
calculated using piezomagnetic models in which stress-induced changes in rock magnetization are produced by the magmatic intrusion.
No significant magnetic changes were observed when the first fractures opened along the NE crater rim. Indeed, the stress-induced
magnetization caused by this magmatic activity is expected to be too low because of the structural weakness and/or thermal
state of the summit area. The continuous long-term decay characterizing the post-eruptive magnetic pattern can be related
to a time-dependent relaxation process. A Maxwell rheology was assumed and the temporal evolution of the piezomagnetic field
was evaluated. This allowed us to estimate the rheological properties of the medium; in particular, an average viscosity ranging
between 1016 and 1017 Pa⋅s was a relaxation time τ of about 38 days. 相似文献
106.
Climate Change over China in the 21st Century as Simulated by BCC_CSM1.1-RegCM4.0 总被引:1,自引:0,他引:1 下载免费PDF全文
Driven by the global model,Beijing Climate Center Climate System Model version 1.1(BCC_CSM1.1),climate change over China in the 21st century is simulated by a regional climate model(RegCM4.0)under the new emission scenarios of the Representative Concentration Pathways—RCP4.5 and RCP8.5.This is based on a period of transient simulations from 1950 to2099,with a grid spacing of 50 km.The present paper focuses on the annual mean temperature and precipitation in China over this period,with emphasis on their future changes.Validation of model performance reveals marked improvement of the RegCM4.0 model in reproducing present day temperature and precipitation relative to the driving BCC_CSM1.1 model.Significant warming is simulated by both BCC_CSM1.1 and RegCM4.0,however,spatial distribution and magnitude differ between the simulations.The high emission scenario RCP8.5 results in greater warming compared to RCP4.5.The two models project different precipitation changes,characterized by a general increase in the BCC_CSM1.1,and broader areas with decrease in the RegCM4.0 simulations. 相似文献
107.
Andreas Bechtold Gerhard Paar Filippo Garolla Rebecca Nowak Laura Fritz Christoph Traxler Oliver Sidla Christian Koeberl 《Meteoritics & planetary science》2023,58(9):1274-1286
Past, present, and forthcoming planetary rover missions to Mars and other planetary bodies are equipped with a large number of scientific cameras. The very large number of images resulting from this, combined with tight time constraints for navigation, measurements, and analyses, pose a major challenge for the mission teams in terms of scientific target evaluation. Shatter cones are the only macroscopic evidence for impact-induced shock metamorphism and therefore impact craters on Earth. The typical features of shatter cones, such as striations and horsetail structures, are particularly suitable for machine learning methods. The necessary training images do not exist for such a case; therefore, we pursued the approach of producing them artificially. Using PRo3D, a viewer developed for the interactive exploration and geologic analysis of high-resolution planetary surface reconstructions, we virtually placed shatter cones in 3-D background scenes processed from true Mars rover imagery. We use PRo3D-rendered images of such scenes as training data for machine learning architectures. Terrestrial analog studies in Ethiopia supported our lab work and were used to test the resulting neural network of this feasibility study. The result showed that our approach with shatter cones in artificial Mars rover scenes is suitable to train neural networks for automatic detection of shatter cones. In addition, we have identified several aspects that can be used to improve the training of the neural network and increase the recognition rate. For example, using background data with a higher resolution in order to have equal resolution of object (shatter cone) and Martian background and increase the number of objects that can be placed in the training data set. Also using better lighting reconstructions and a better radiometric adaption between object and Martian background would further improve the results. 相似文献
108.
Regional climate model projections over the Mediterranean region are analysed for the presence of intense, warm-core lows that share some of the characteristics of tropical cyclones. The results indicate that the number of such systems decreases in a warmer world, particularly in winter. Comparison of the simulated numbers to changes in relevant climate diagnostics suggests that numbers decrease due to an increasingly hostile environment for storm formation, combined with a general poleward shift in the incidence of wintertime lows over western Europe. 相似文献
109.
Marta Llopart Erika Coppola Filippo Giorgi Rosmeri P. da Rocha Santiago V. Cuadra 《Climatic change》2014,125(1):111-125
We analyze the local and remote impacts of climate change on the hydroclimate of the Amazon and La Plata basins of South America (SA) in an ensemble of four 21st century projections (1970–2100, RCP8.5 scenario) with the regional climate model RegCM4 driven by the HadGEM, GFDL and MPI global climate models (GCMs) over the SA CORDEX domain. Two RegCM4 configurations are used, one employing the CLM land surface and the Emanuel convective schemes, and one using the BATS land surface and Grell (over land) convection schemes. First, we find considerable sensitivity of the precipitation change signal to both the driving GCM and the RegCM4 physics schemes (with the latter even greater than the first), highlighting the pronounced uncertainty of regional projections over the region. However, some improvements in the simulation of the annual cycle of precipitation over the Amazon and La Plata basins is found when using RegCM4, and some consistent change signals across the experiments are found. One is a tendency towards an extension of the dry season over central SA deriving from a late onset and an early retreat of the SA monsoon. The second is a dipolar response consisting of reduced precipitation over the broad Amazon and Central Brazil region and increased precipitation over the La Plata basin and central Argentina. An analysis of the relative influence on the change signal of local soil-moisture feedbacks and remote effects of Sea Surface Temperature (SST) over the Niño 3.4 region indicates that the former is prevalent over the Amazon basin while the latter dominates over the La Plata Basin. Also, the soil moisture feedback has a larger role in RegCM4 than in the GCMs. 相似文献
110.
Filippo Ridolfi Alberto Renzulli Antonio Acosta-Vigil 《Contributions to Mineralogy and Petrology》2014,167(4):1-20
In this work, we have reviewed a large compositional dataset (571 analyses) for natural and experimental glasses to understand the physico-chemical and compositional conditions of magmatic cordierite crystallization. Cordierite crystallizes in peraluminous liquids (A/CNK ≥1) at temperatures ≥750 °C, pressures ≤700 MPa, variable H2O activity (0.1–1.0) and relatively low fO2 conditions (≤NNO ? 0.5). In addition to A/CNK ratio ≥1, a required condition for cordierite crystallization is a Si + Al cation value of the rhyolite liquid of 4 p8O (i.e. calculated on the 8 oxygen anhydrous basis), which is consistent with low Fe3+ contents and the absence or low content of non-bridging oxygens (NBO). This geochemical condition is strongly supported by the rare, if not unique, structure of cordierite where the tetrahedral framework is composed almost exclusively of Si and Al cations the sum of which is equal to 4 p8O [i.e. (Mg,Fe)8/9Al16/9Si20/9O8], indicating that aluminium (and cordierite) saturation is limited by rhyolite liquids with Al = 4 ? Si. Indeed, synthetic or natural systems with Al > 4 ? Si always show metastable glass-in-glass separation or crystallization of refractory minerals such as corundum (Al16/3O8) and aluminosilicates (Al16/5Si8/5O8). Multivariate regression analyses of literature data for experimental glasses coexisting with magmatic cordierite produced two empirical equations to independently calculate the T (±13 °C; ME, maximum error = 29 °C) and P (±16 %; ME% = 27 %) conditions of cordierite saturation. The greatest influence on the two equations is exerted by H2Omelt and Al concentrations, respectively. Testing of these equations with other thermobarometric constraints (e.g. feldspar-liquid, GASP, Grt–Bt and Grt–Crd equilibria) and thermodynamic models (NCKFMASHTO and NCKFMASH systems) was successfully performed for Crd-bearing rhyolites and residual enclaves from San Vincenzo (Tuscany, Italy), Morococala Field (Bolivia) and El Hoyazo (Spain). The reliability of each calculated P–T pair was graphically evaluated using the minimum and maximum P–T–H2O relationships for peraluminous rhyolite liquids modified after the metaluminous relationships in this work. Both P–T calculations and checking can be easily performed with the attached user-friendly spreadsheet (i.e. Crd-sat_TB). 相似文献