Dark matter haloes in interacting isolated galaxy pairs: The Importance of the Hα rotation curve     

Isaura Fuentes-Carrera  Philippe Amram  Margarita Rosado 《Astrophysics and Space Science》2002,281(1-2):411-414

We present Hα scanning Fabry-Perot observations of the interacting galaxy pair NGC 3893/96 (Kar 302), an M51-type galaxy pair. The velocity field and rotation curve of the main galaxy (NGC 3893) were derived. These show the galaxy follows a rather axisymmetric behaviour. Together with HI observations, several mass models were adjusted in order to study the nature of the dark halo as well as the mass-to-light ratio of the galaxy. We find that in order to constrain these models, it is important to have a high resolution Hα rotation curve for the inner parts of the galaxy. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   

Distances on Cosmological Scales with VLTI     

Margarita Karovska  Martin Elvis  Massimo Marengo 《Astrophysics and Space Science》2003,286(1-2):261-266

We present here a new method using interferometric measurements of quasars, that allows the determination of direct geometrical distances on cosmic scales. Quasar Broad Emission Line Regions sizes provide a `meter rule' with which to measure the metric of the Universe. This method is less dependent of model assumptions, and even of variations in the fundamental constants (other than c).We discuss the spectral and spatial requirements on the VLTI observations needed to carry out these measurements. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The origin of presolar nova grains     

Jordi JOs  Margarita Hernanz 《Meteoritics & planetary science》2007,42(7-8):1135-1143

Abstract— Infrared observations reveal that classical novae often form dust in their expanding shells ejected into the interstellar medium as a consequence of violent outbursts. Recent experimental efforts have led to the identification of presolar nova candidate grains from the Acfer 094 and Murchison meteorites. Recently, however, concerns have been raised about the stellar paternity of these grains by new measurements on another sample of SiC grains: these grains are characterized by ¹²C/¹³C and ¹⁴N/¹⁵N ratios similar to the ones reported for the nova grains, but a number of different imprints suggest that a possible supernova origin cannot be excluded. Here we review the predicted nucleosynthetic imprints accompanying nova explosions and discuss the chances to synthesize heavier species, such as titanium, in nova‐like events.  相似文献   

A DUAL mission for nuclear astrophysics     

Peter von Ballmoos  Jose Alvarez  Nicolas Barrière  Steve Boggs  Andrei Bykov  Juan Manuel Del Cura Velayos  Filippo Frontera  Lorraine Hanlon  Margarita Hernanz  Emmanuel Hinglais  Jordi Isern  Pierre Jean  Jürgen Kn?dlseder  Lucien Kuiper  Mark Leising  Beno?t Pirard  Jean-Pierre Prost  Rui M. Curado da Silva  Tadayuki Takahashi  John Tomsick  Roland Walter  Andreas Zoglauer 《Experimental Astronomy》2012,34(2):583-622

DUAL will study the origin and evolution of the elements and explores new frontiers of physics: extreme energies that drive powerful stellar explosions and accelerate particles to macroscopic energies; extreme densities that modify the laws of physics around the most compact objects known; and extreme fields that influence matter in a way that is unknown on Earth. The variability of these extreme objects requires continuous all-sky coverage, while detailed study demands an improvement in sensitivity over previous technologies by at least an order of magnitude. The DUAL payload is composed of an All-Sky Compton Imager (ASCI), and two optical modules, the Laue-Lens Optic (LLO) and the Coded-Mask Optic (CMO). The ASCI serves dual roles simultaneously, both as an optimal focal-plane sensor for deep observations with the optical modules and as a sensitive true all-sky telescope in its own right for all-sky surveys and monitoring. While the optical modules are located on the main satellite, the All-Sky Compton Imager is situated on a deployable structure at a distance of 30?m from the satellite. This configuration not only permits to maintain the less massive payload at the focal distance, it also greatly reduces the spacecraft-induced detector background, and, above all it provides ASCI with a continuous all-sky exposure.  相似文献   

The Stellar Imager (SI) project: a deep space UV/Optical Interferometer (UVOI) to observe the Universe at 0.1 milli-arcsec angular resolution     

Kenneth G. Carpenter  Carolus J. Schrijver  Margarita Karovska 《Astrophysics and Space Science》2009,320(1-3):217-223

The Stellar Imager (SI) is a space-based, UV/Optical Interferometer (UVOI) designed to enable 0.1 milli-arcsecond (mas) spectral imaging of stellar surfaces and of the Universe in general. It will also probe via asteroseismology flows and structures in stellar interiors. SI’s science focuses on the role of magnetism in the Universe and will revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magneto-hydrodynamically controlled processes, such as accretion, in the Universe. The ultra-sharp images of SI will revolutionize our view of many dynamic astrophysical processes by transforming point sources into extended sources, and snapshots into evolving views. SI is a “Flagship and Landmark Discovery Mission” in the 2005 Heliophysics Roadmap and a potential implementation of the UVOI in the 2006 Science Program for NASA’s Astronomy and Physics Division. We present here the science goals of the SI Mission, a mission architecture that could meet those goals, and the technology development needed to enable this mission. Additional information on SI can be found at: http://hires.gsfc.nasa.gov/si/.  相似文献   

Ar-Ar Geochronology in a gneiss dome within the Zagros Orogénic Belt     

Akram Alizadeh  Margarita López Martínez  Khalil Sarkarinejad 《Comptes Rendus Geoscience》2010,342(11):837-846

Exhumation of the Tutak mantled gneiss dome without significant cooling has taken place in a doubly plunging anticline within the Sanandaj-Sirjan HP-LT metamorphic belt in the Zagros Thrust System of Iran. Reconstruction of structural evolution of the Tutak gneiss dome at the contact between Arabian and Iranian plates by ⁴⁰Ar/³⁹Ar geochronology exhibits history of the closure of Neo-Tethyan Ocean. There are two granites of different ages in the core of dome; the oldest corresponds to the central Iranian continental crust and was deformed at about 180 Ma. The younger granite was emplaced in the NE–SW transpression system. The timing of strain-related fabrics and exhumation history of the region illustrates the closure of Neo-Tethys and beginning of continent-continent collision at about 77 Ma, as constrained by a well defined plateau ⁴⁰Ar/³⁹Ar age obtained on biotite. Then, the biotite age corresponds to the second stage of emplacement of the Bendenow granite-gneiss which illustrating repeated orogenic events. Continuing deformation without interruption that by now has been created at about 77 Ma, was largely restricted to the transpression and high proportion of simple shear components relative to the pure shear components along the NE–SW.  相似文献   

Precious-metal distribution and fluid-inclusion petrography of the Elatsite porphyry copper deposit,Bulgaria   总被引：4，自引：2，他引：2  

Mahmud?TarkianEmail author  Ulf?Hünken  Margarita?Tokmakchieva  Kamen?Bogdanov 《Mineralium Deposita》2003,38(3):261-281

The Elatsite porphyry copper deposit occurs in an island-arc setting hosted by Late Cretaceous monzonitic-monzodioritic porphyry stocks which were emplaced into Precambrian-Cambrian phyllites. Trace element data of the Late Cretaceous intrusive rocks suggest that they are I-type volcanic arc granitoids. Two main ore mineral assemblages are distinguished: (1) magnetite-bornite-chalcopyrite, and (2) chalcopyrite-pyrite. The first one is linked to potassic-propylitic, and the second to phyllic-argillic alteration. Minor ore minerals are hematite, molybdenite, sphalerite, pyrrhotite, marcasite, hessite, and solid solutions of linnaeite-siegenite-carrollite, tetrahedrite-tennantite, clausthalite-galena, gold-electrum and merenskyite-moncheite. Precious-metal contents are relatively high throughout the deposit but Au, Pd and Pt are concentrated more strongly in the magnetite-bornite-chalcopyrite assemblage. Average grades of Au, Ag, Pd and Pt calculated for the 0.33% Cu ore body are 0.96, 0.19, 0.007 and 0.002 g/t respectively. Analyses of flotation concentrates revealed 25.6% Cu, and Ag, Au, Pd and Pt contents of 33.0, 13.6, 0.72 and 0.15 g/t respectively. The copper mineralisation at Elatsite took place at pressures of 120 to 300 bar, corresponding to depths of formation of 1 to 3 km under hydrostatic conditions. The precious metals were probably transported jointly as chloride complexes in highly saline magmatic-hydrothermal solutions. The fluids had temperatures of 340 to >700 °C and salinities of 28 to 64% NaCl, and mixed with meteoric water.  相似文献   

Present Limnological Conditions and Recent (ca. 340 yr) Palaeolimnology of a Tropical Lake in the Sierra de Los Tuxtlas, Eastern Mexico     

Margarita Caballero  Gabriela Vázquez  Socorro Lozano-García  Alejandro Rodríguez  Susana Sosa-Nájera  Ana Carolina Ruiz-Fernández  Beatriz Ortega 《Journal of Paleolimnology》2006,35(1):83-97

The Sierra de Los Tuxtlas is a recently active volcanic field, with eruptions in 1664 and 1792. It holds one of the reserves of tropical evergreen forest in Mexico, as well as several maar lakes. One of them, Lago Verde, was chosen for a three-fold study (1) on its present limnological conditions, (2) on the algal community living in the water column and preserved in the surface sediments; and (3) on its recent history (ca. 340 yr). The palaeolimnological study was based on multiproxy analyses on core material dated by ²¹⁰Pb, ¹³⁷Cs and ¹⁴C. Lago Verde is a small, shallow lake with dilute, slightly alkaline water (CO₃²⁻ + HCO₃⁻ > Cl⁻ > SO₄²⁻, Na⁺ + K⁺ > Ca²⁺ > Mg²⁺). It is turbid, eutrophic, with high phosphorus levels. It is a warm polymictic lake, with thermal and oxygen stratification establishing by midday during the warm months. The lake does not stratify in winter. Diatoms dominate the phytoplankton community in the cold ‘nortes’ season, Cyanobacteria in summer, and Chlorophyta in autumn. Cyanobacteria (Chroococcales) are not well preserved in the surface sediments while Chlorophyta are better preserved. Sedimentary diatoms are well preserved, dominated by the three most abundant species in the water column: Achnanthidium minutissimum, Fragilaria capucina and Aulacoseira granulata. The base of the studied sequences is constrained by the historic eruption of 1664. The period from 1664 to 1963 is characterised by a meso-eutrophic lake. Tropical Forest vegetation reaches maximum values between ca. 1800 and 1963. Between ca. 1785 and 1885 the lake was slightly shallower than in the rest of the 1664–1963 period, probably recording climatic variability. An early pulse of anthropogenic disturbance was recorded by ca. 1921 and after ca. 1963 intense forest clearance and high erosion rates led to a more turbid, more productive, nutrient-rich lake. The highest anthropogenic impact was reached by ca. 1988; afterwards the lake and its basin reached a new balance, with the establishment of the present modern conditions.  相似文献   

Pb chronology and trace metal geochemistry at Los Tuxtlas, Mexico, as evidenced by a sedimentary record from the Lago Verde crater lake     

Ana Carolina Ruiz-Fernández  Claude Hillaire-Marcel  Federico Páez-Osuna  Bassam Ghaleb  Margarita Caballero 《Quaternary Research》2007,67(2):181-192

Lago Verde is a fresh-water maar found on the lower slopes of San Martin volcano, at the Sierra de Los Tuxtlas, Mexico, currently the northernmost remnant of the tropical rain forest in America. ²¹⁰Pb and ¹³⁷Cs analyzed in a sediment core were used to reconstruct the historical fluxes of Ag, Cd, Cu, Pb, Hg and Zn to the site during the last ∼ 150 yr. The ²¹⁰Pb_xs-derived sediment accumulation rates, the magnetic susceptibility, C/N ratios and δ¹³C data evidenced background conditions at the lake until 1960s, when enhanced erosion related to the clearing of large forested areas at Los Tuxtlas promoted higher accumulation rates of a heavier and more magnetic sedimentary material. Recent sediments from Lago Verde were found enriched by Pb (26-fold natural concentration level [NCLs]) and moderately enriched by Cd > Cu > Zn and Hg (6-, 5-, 4- and 4-fold corresponding NCLs, respectively). The fluxes of Cu, Hg, Pb and Zn have significantly increased since 1940s, with peak ratios of total modern to pre-industrial fluxes of 11, 11, 19 and 49, respectively. The lake occupies a relatively pristine, non-industrialized basin, and therefore the increased metal fluxes might be related to long-distance aeolian transport of trace metals.  相似文献   

Satellite remote sensing of the optical depth and mean crystal size of thin cirrus and contrails     

Margarita Betancor Gothe  H. Graßl 《Theoretical and Applied Climatology》1993,48(2-3):101-113

Summary Crystal size and optical depth of optically thin cirrus clouds and contrails over the North Sea and Adriatic Sea on the 18^th of October 1989 are retrieved by comparison of NOAA AVHRR/2 brightness temperatures of channel 4 (9.97 µm–11.56 µm) and channel 5 (11.075 µm–12.76 µm) with one dimensional radiative transfer calculations. Measured brightness temperatures in all three infrared channels and their differences show higher values for contrails than for cirrus. The radiative properties of young contrails are consistent only, if smaller crystal size than those given for natural cirrus are adopted for the calculations. However, there is a continuous transition in radiative parameters between clouds classified as natural cirrus or contrails. For the test areas ice clouds are classified with respect to optical depth and mean crystal size. Finally infrared fluxes and heating rates in the spectral range 4 µm–40 µm are calculated for an atmosphere with a 500 m thick contrail or cirrus uncinus. At given ice content a far stronger atmospheric warming is found for a contrail with relatively small ice crystals: up to 80 K/day at cloud base for an ice content of 0.05 gm^–3 compared to 10 K/day for a cirrus uncinus with large crystals.With 11 Figures  相似文献