Sedimentary climatic record in the Galician Internal Basin: sediment provenance, transport time and hydrodynamics over the last 60.000 years

The sediments of the Galician Interior Basin are influenced by the Atlantic Meridional Overturning Circulation (AMOC) and by their proximity to the Western Iberia continental landmass, and thus provide an adequate archive to study the peculiarities of the last glacial‐interglacial dynamics and the transition into present day conditions. The aim of this study has been to analyse the sedimentary expression of climatic processes and forcings derived from the relation between the last North Atlantic glacial cycle and the local regional components -including abrupt climate changes and local events- since the end of the last glacial period in this area. We have attempted to establish the rates and magnitudes of change of this system to understand its climate dynamics, processes and feedbacks, and hence its role on a local to sub‐regional scale from a palaeoclimatic proxies perspective. The inference of these climatic mechanisms encrypted in the deep-sea sedimentary record needs to constrain the spatial and temporal scales of the sedimentary processes involved, in particular the identification of source areas, pathways and transport, storage times and hydrodynamic conditions. In order to achieve these goals we have used a twofold approach; an initial effort to constrain the current sedimentary conditions to their associated local hydrography conditions by means of a mooring, which will be used to later infer the palaeoenvironmental conditions from sediment cores. The location of the mooring and the 5 coring locations has been based on the acquisition of new geophysical data: a precise 20 x 20 m bathymetry covering an area of 9860 km2 and 690 km of high-resolution seismic profiles distributed in 10 transects that allow to investigate the main sedimentary units in the region. The mooring comprised 2 sediment traps located at 500 and 1400 m below the sea surface. These depths are under the influence of the Eastern North Atlantic Central Water (ENACW) and Mediterranean Water (MW). The sediment traps also target sediments from the shelf and the upper slope. Sediments were collected monthly for a 9 month period, whilst hydrographic conditions such as current speed, salinity, oxygen and turbidity were continuously recorded in associated instruments at the same depths. Finally, a multidisciplinary study combining resolution scans, including geochemistry (ITRAX), physical properties (GEOTEK) and enviromagnetic properties (2G cryogenic magnetometer), has been constrained using a very robust geochronology framework. Further analyses comprised grain size distributions, S͞S, SEM, XRD, stable and high-precision radioactive isotopes. The area consists mostly of generally autochthonous hemipelagic and terrigenous muds and sandy to silty muds with high clay content, showing abundant bioturbation and early diagenesis. Allochthonous material of different provenances (characterized by 143Nd/144Nd and 87Sr/ 86Sr isotopic ratios) occurs interbedded within the hemipelagic sediments associated to Heinrich Stadials HS1 to HS6. The sediments also show significant changes in the vigour of bottom-currents (based on the S͞S proxy) both within and between the HS. The combination of these sedimentological, geochemical and geophysical data has provided a new insight into the role of current strength, circulation and sediment provenance changes in the area, and allowed to establish across vs. along margin transport balances in the sedimentary record of the Galician Internal basin over the last 60 Ky

SOPHIE velocimetry of Kepler transit candidates XVII. The physical properties of giant exoplanets within 400 days of period

While giant extrasolar planets have been studied for more than two decades now, there are still some open questions such as their dominant formation and migration process, as well as their atmospheric evolution in different stellar environments. In this paper, we study a sample of giant transiting exoplanets detected by the Kepler telescope with orbital periods up to 400 days. We first defined a sample of 129 giant-planet candidates that we followed up with the SOPHIE spectrograph (OHP, France) in a 6-year radial velocity campaign. This allow us to unveil the nature of these candidates and to measure a false-positive rate of 54.6 +/- 6.5 % for giant-planet candidates orbiting within 400 days of period. Based on a sample of confirmed or likely planets, we then derive the occurrence rates of giant planets in different ranges of orbital periods. The overall occurrence rate of giant planets within 400 days is 4.6 +/- 0.6 %. We recover, for the first time in the Kepler data, the different populations of giant planets reported by radial velocity surveys. Comparing these rates with other yields, we find that the occurrence rate of giant planets is lower only for hot jupiters but not for the longer period planets. We also derive a first measurement on the occurrence rate of brown dwarfs in the brown-dwarf desert with a value of 0.29 +/- 0.17 %. Finally, we discuss the physical properties of the giant planets in our sample. We confirm that giant planets receiving a moderate irradiation are not inflated but we find that they are in average smaller than predicted by formation and evolution models. In this regime of low-irradiated giant planets, we find a possible correlation between their bulk density and the Iron abundance of the host star, which needs more detections to be confirmed.Comment: To appear in Astronomy and Astrophysic

The SOPHIE search for northern extrasolar planets. XI. Three new companions and an orbit update: Giant planets in the habitable zone

We report the discovery of three new substellar companions to solar-type stars, HD191806, HD214823, and HD221585, based on radial velocity measurements obtained at the Haute-Provence Observatory. Data from the SOPHIE spectrograph are combined with observations acquired with its predecessor, ELODIE, to detect and characterise the orbital parameters of three new gaseous giant and brown dwarf candidates. Additionally, we combine SOPHIE data with velocities obtained at the Lick Observatory to improve the parameters of an already known giant planet companion, HD16175 b. Thanks to the use of different instruments, the data sets of all four targets span more than ten years. Zero-point offsets between instruments are dealt with using Bayesian priors to incorporate the information we possess on the SOPHIE/ELODIE offset based on previous studies. The reported companions have orbital periods between three and five years and minimum masses between 1.6 Mjup and 19 Mjup. Additionally, we find that the star HD191806 is experiencing a secular acceleration of over 11 \ms\ per year, potentially due to an additional stellar or substellar companion. A search for the astrometric signature of these companions was carried out using Hipparcos data. No orbit was detected, but a significant upper limit to the companion mass can be set for HD221585, whose companion must be substellar. With the exception of HD191806 b, the companions are located within the habitable zone of their host star. Therefore, satellites orbiting these objects could be a propitious place for life to develop.Comment: 12 pages + tables, 7 figures. Accepted for publication in Astronomy & Astrophysic

The SOPHIE search for northern extrasolar planets VIII. A warm Neptune orbiting HD164595

High-precision radial velocity surveys explore the population of low-mass exoplanets orbiting bright stars. This allows accurately deriving their orbital parameters such as their occurrence rate and the statistical distribution of their properties. Based on this, models of planetary formation and evolution can be constrained. The SOPHIE spectrograph has been continuously improved in past years, and thanks to an appropriate correction of systematic instrumental drift, it is now reaching 2 m/s precision in radial velocity measurements on all timescales. As part of a dedicated radial velocity survey devoted to search for low-mass planets around a sample of 190 bright solar-type stars in the northern hemisphere, we report the detection of a warm Neptune with a minimum mass of 16.1 +- 2.7 Mearth orbiting the solar analog HD164595 in 40 +- 0.24 days . We also revised the parameters of the multiplanetary system around HD190360. We discuss this new detection in the context of the upcoming space mission CHEOPS, which is devoted to a transit search of bright stars harboring known exoplanets.Comment: 11 pages, 9 figure

Late Holocene climatic oscillations traced by clay mineral assemblages and other palaeoceanographic proxies in Ria de Vigo (NW Spain)

This work aims to study recent climatic oscillations and their influence on sedimentation in the Ria de Vigo, a coastal embayment in Galicia, NW Spain. It is based on the study of clay mineral assemblages, in conjunction with other proxies (granulometric, geochemical, geochronological and microfaunal), in the core KSGX 24. A Benthic Foraminifera High Productivity (BFHP) proxy was used to determine changes in the flux of organic matter (OM) at the bottom of the study area. Total organic carbon (TOC) content is not a suitable proxy to estimate changes in the past supply of OM due to diagenetic processes.The sedimentation was finest in 3 sections: ~ 230–214 cm, ~ 185–73 cm and ~ 20–0 cm. These muddy sections are characterised, in general, by higher proportions of detrital minerals, concentrations of several chemical elements related to lithogenic sources and BFHP values. In addition, these sections are impoverished in carbonates, Ca, Sr and La when compared with the layers with the highest sand content.The clay mineral assemblage of the studied site, characterised by the dominance of illite, intermediate concentrations of kaolinite and minor amounts of smectite and chlorite, reveals the prevalence of a typical temperate humid climate in the last 3 ka BP, the estimated age for the core base. However, the quantities of illite and chlorite increase in the muddy layers. The characteristics of these muddy layers were interpreted as representing relatively cold climatic oscillations associated with the strengthening of northerly winds and the prevalence of an upwelling regime corresponding to wellknown periods, such as the first cold period of the Upper Holocene (~ 2.9 ka cal BP), the Dark Ages (between ~ 2.2 - 1.2 ka cal BP) and the Little Ice Age (~ 0.6 ka cal BP)

The SOPHIE search for northern extrasolar planets VIII. Follow-up of ELODIE candidates: long-period brown-dwarf companions

Long-period brown dwarf companions detected in radial velocity surveys are important targets for direct imaging and astrometry to calibrate the mass-luminosity relation of substellar objects. Through a 20-year radial velocity monitoring of solar-type stars that began with ELODIE and was extended with SOPHIE spectrographs, giant exoplanets and brown dwarfs with orbital periods longer than ten years are discovered. We report the detection of five new potential brown dwarfs with minimum masses between 32 and 83 Jupiter mass orbiting solar-type stars with periods longer than ten years. An upper mass limit of these companions is provided using astrometric Hipparcos data, high-angular resolution imaging made with PUEO, and a deep analysis of the cross-correlation function of the main stellar spectra to search for blend effects or faint secondary components. These objects double the number of known brown dwarf companions with orbital periods longer than ten years and reinforce the conclusion that the occurrence of such objects increases with orbital separation. With a projected separation larger than 100 mas, all these brown dwarf candidates are appropriate targets for high-contrast and high angular resolution imaging.Comment: 17 pages, 9 figures, accepted in A&

Chemical factors controlling the steady-state distribution of mixed carbonate-siliciclastic sediments in Bayona Bay (northwest Spain)

The relative space distributions of single mineral constituents in mixed terrigenous-carbonated sediments of the Bayona Bay have been analysed. In order to determine the existence of different mixing mechanisms, a study comparing the general sedimentary trends resulting from the average patterns and the single mineral behaviour, reflected in the single-mineral mapping, was carried out. The relative abundance of all mineral phases in surface sediment samples was first determined by quantitative X-ray powder diffraction data, using the Rietveld method. This procedure enabled us to create specific maps for both the minerals forming the terrigenous fraction and the different calcium carbonate polymorphs involved in the carbonatic component. A cross-linked behaviour between the carbonate facies and the terrigenous minerals involved in the calcium carbonate generation was found, suggesting the existence of a chemical control mechanism which, through dissolution-crystallization processes, constrains the mixed environment's long-term evolution. In the general framework of the region studied, these relations operate for the relative amount of plagioclase to calcium carbonate. The existence of dissolution and growth between both minerals, favoured by the high rate of removal, is proposed, yielding a final crossed pattern, representative of the steady-state. Furthermore, a specific analysis, restricted to the region of low rate of material removal and maximum amount of intermixed sediments, clearly shows an anisotropic distribution for every calcium carbonate polymorph (calcite and aragonite). These correlate with the biotite distribution, and can be connected to local variations in seawater Mg/Ca ratio, induced by biotite weathering.En este trabajo se analiza de forma específica la distribución espacial de cada uno de los minerales involucrados en sedimentos mixtos terrígenos-carbonatados de la bahía de Bayona y se compara con la distribución global de sedimentos, tal como resulta de análisis granulométricos, con el fin de determinar la existencia de diferentes mecanismos de mezcla entre los minerales de ambas fracciones. El contenido porcentual en peso de cada fase mineral, en muestras superficiales de sedimento, se determinó a partir de datos cuantitativos de DRX, empleando el método de Rietveld. Este procedimiento nos ha permitido realizar mapas específicos de distribución, tanto para cada mineral de la fracción terrígena como para cada uno de los diferentes polimorfos de carbonato cálcico en la componente carbonatada. Como resultado de este estudio comparativo, se ha encontrado una correlación, en la distribución espacial y granulométrica, de las facies carbonatadas y los minerales terrígenos implicados en la generación de carbonato cálcico. Un posterior análisis de este resultado sugiere la presencia de mecanismos químicos de control que regulan la interacción entre siliciclastos y carbonatos mediante procesos de disolución-cristalización mediados por el agua del mar. El estudio se ha realizado a dos escalas. En el ámbito general de la bahía de Bayona, las relaciones de distribución observadas entre plagioclasas y carbonato cálcico pueden ser explicadas, dentro del balance global del Ca³⁺ disuelto en el agua del mar, mediante la meteorización química de las plagioclasas y la consiguiente generación de carbonatos. En este caso, los patrones de distribución reflejan la aproximación a un estado estacionario mediante sucesivos eventos de mezcla asociados a la alta removilización material en el medio, tanto para la distribución porcentual en peso como para la distribución granulométrica entre ambos minerales. Finalmente, se realiza un análisis particularizado en una región con baja tasa de removilización y donde la interacción entre sedimentos de ambas fracciones es máxima. El resultado muestra claramente una distribución espacial anisótropa para cada uno de las fases de carbonato cálcico (calcita y aragonito). La abundancia relativa de cada uno de los polimorfos, así como el contenido en Mg³⁺ de la calcita, ha sido correlacionado con la distribución de la biotita y explicado a partir de las diferencias de solubilidad en función de la alta relación Mg³⁺ /Ca³⁺ en el agua de mar que resulta, localmente, de la meteorización química de dicho mineral.Instituto Español de Oceanografí

Cooling in strongly correlated optical lattices: prospects and challenges

Optical lattices have emerged as ideal simulators for Hubbard models of strongly correlated materials, such as the high-temperature superconducting cuprates. In optical lattice experiments, microscopic parameters such as the interaction strength between particles are well known and easily tunable. Unfortunately, this benefit of using optical lattices to study Hubbard models come with one clear disadvantage: the energy scales in atomic systems are typically nanoKelvin compared with Kelvin in solids, with a correspondingly miniscule temperature scale required to observe exotic phases such as d-wave superconductivity. The ultra-low temperatures necessary to reach the regime in which optical lattice simulation can have an impact-the domain in which our theoretical understanding fails-have been a barrier to progress in this field. To move forward, a concerted effort to develop new techniques for cooling and, by extension, techniques to measure even lower temperatures. This article will be devoted to discussing the concepts of cooling and thermometry, fundamental sources of heat in optical lattice experiments, and a review of proposed and implemented thermometry and cooling techniques.Comment: in review with Reports on Progress in Physic