Photometry and long-slit spectroscopy are presented for 14 S0 and spiral galaxies of the Fornax, Eridanus and Pegasus cluster, and NGC 7582 group. The structural parameters of the galaxies are ...derived from the R-band images by performing a two-dimensional photometric decomposition of the surface brightness distribution. This is assumed to be the sum of the contribution of a bulge and disc component characterized by elliptical and concentric isophotes with constant (but possibly different) ellipticity and position angles. The rotation curves and velocity dispersion profiles are measured from the spectra obtained along the major axis of galaxies. The radial profiles of the Hβ, Mg and Fe line-strength indices are presented too. Correlations between the central values of Mg2, 〈Fe〉, Hβ and σ are found. The age, metallicity and α/Fe enhancement of the stellar population in the centre and at the radius where bulge and disc give the same contribution to the total surface brightness are obtained using stellar population models with variable element abundance ratios. Three classes of bulges are identified. The youngest bulges (∼2 Gyr) with ongoing star formation, intermediate-age bulges (4-8 Gyr) have solar metallicity, and old bulges (∼10 Gyr) have high metallicity. Most of the sample bulges display solar α/Fe enhancement, no gradient in age and a negative gradient of metallicity. The presence of negative gradient in the metallicity radial profile favours a scenario with bulge formation via dissipative collapse. This implies strong inside-out formation that should give rise to a negative gradient in the α/Fe enhancement too. But, no gradient is measured in the α/Fe radial profiles for all the galaxies, except for NGC 1366. In this galaxy there is a kinematically decoupled component, which is younger than the rest of host bulge. It possibly formed by enriched material probably acquired via interaction or minor merging. The bulge of NGC 1292 is the most reliable pseudo-bulge of our sample. The properties of its stellar population are consistent with a slow build-up within a scenario of secular evolution.
We report the discovery of four super-Earth planets around HD 215152, with orbital periods of 5.76, 7.28, 10.86, and 25.2 d, and minimum masses of 1.8, 1.7, 2.8, and 2.9 M⊕ respectively. This ...discovery is based on 373 high-quality radial velocity measurements taken by HARPS over 13 yr. Given the low masses of the planets, the signal-to-noise ratio is not sufficient to constrain the planet eccentricities. However, a preliminary dynamical analysis suggests that eccentricities should be typically lower than about 0.03 for the system to remain stable. With two pairs of planets with a period ratio lower than 1.5, with short orbital periods, low masses, and low eccentricities, HD 215152 is similar to the very compact multi-planet systems found by Kepler, which is very rare in radial-velocity surveys. This discovery proves that these systems can be reached with the radial-velocity technique, but characterizing them requires a huge amount of observations.
Recently, special attention has been given to low-cost technologies for water treatment, with the aim of serving remote communities and thus enabling everyone to have access to drinking water and ...basic sanitation. In that context, the ecological filter is an alternative for treating water for human consumption. Some studies show that climate change and meteorological parameters can influence the water quality of water bodies and the water supply system. However, most of the papers deal with model projections and therefore do not show real situations. The aim of this study was to determine the impact of meteorological variables (e.g. atmospheric pressure, evaporation, wind speed, radiation, precipitation) on the physico-chemical and biological parameters (e.g. turbidity, apparent colour, pH, total coliforms,
Escherichia coli
) of Lobo reservoir water treated by 22 ecological filters during a period of 4 months. Statistically significant correlations were found between the water from the Lobo reservoir and the weather variables, and between the water quality parameters of the 22 ecological filters and the average weather variables. The results from the statistical analysis indicate that climatic variations may influence treatment performance.
Deep surface photometry in the K band was obtained for 54 normal spiral galaxies, with the aim of quantifying the percentage of faint bars and studying the morphology of spiral arms. The sample was ...chosen to cover a wider range of morphological types while inclination angles and distances were limited to allow a detailed investigation of the internal structure of their disks and future observations and studies of the disk kinematics. An additional constraint for a well defined subsample was that no bar structure was seen on images in the visual bands. Accurate sky projection parameters were determined from the K maps comparing several different methods. The surface brightness distribution was decomposed into axisymmetric components while bars and spiral structures were analyzed using Fourier techniques. Bulges were best represented by a Sersic r super(1/n) law with an index in the typical range of 1-2. The central surface brightness of the exponential disk and bulge-to-disk ratio only showed weak correlation with Hubble type. Indications of a central point source were found in many of the galaxies. An additional central, steep, exponential disk improved the fit for more than 80% of the galaxies suggesting that many of the bulges are oblate. Bars down to the detection level at a relative amplitude of 3% were detected in 26 of 30 galaxies in a subsample classified as ordinary SA spirals. This would correspond to only 5% of all spiral galaxies being non-barred at this level. In several cases, bars are significantly offset compared to the starting points of the main spiral pattern which indicates that bar and spiral have different pattern speeds. A small fraction ( similar to 10%) of the sample has complex central structures consisting of several sets of bars, arcs or spirals. A majority of the galaxies ( similar to 60%) displays a two-armed, grand-design spiral pattern in their inner parts which often breaks up into multiple arms in their outer regions. Phase shifts between the inner and outer patterns suggest in some cases that they belong to different spiral modes. The pitch angles of the main two-armed symmetric spiral pattern in the galaxies have a typical range of 5-30 degree . The sample shows a lack of strong, tight spirals which could indicate that such patterns are damped by non-linear, dynamical effects due to their high radial force perturbations.
Three galaxy clusters selected from the XXL X-ray survey at high redshift and low mass (z ~ 1 and M500 ~ 1 – 2 × 1014 M⊙) were observed with NIKA2 to image their Sunyaev-Zel'dovich effect (SZ) ...signal. They all present an SZ morphology, together with the comparison with X-ray and optical data, that indicates dynamical activity related to merging events. Despite their disturbed intracluster medium, their high redshifts, and their low masses, the three clusters follow remarkably well the pressure profile and the SZ flux-mass relation expected from standard evolution. This suggests that the physics that drives cluster formation is already in place at z ~ 1 down to M500 ~ 1014 M⊙.
The southern long-period Cepheid RS Pup is surrounded by a large circumstellar dusty nebula reflecting the light from the central star. Due to the changing luminosity of the central source, light ...echoes propagate into the nebula. This remarkable phenomenon was the subject of Paper I. The goal is to determine the three-dimensional structure of the light-scattering nebula, and estimate its mass. This will bring us new clues on the origin of the nebula. Knowing the geometrical shape of the nebula will also allow us to retrieve the distance of RS Pup in an unambiguous manner using a model of its light echoes. The high mass of the dusty nebula excludes that it was created by mass-loss from the star. However, the thinness of the dust distribution is an indication that the Cepheid participated to the shaping of the nebula, e.g. through its radiation pressure or stellar wind.
Aims. It has been widely recognized that processes taking place inside group environment could be important drivers of galaxy evolution. Compact groups of galaxies in particular are excellent ...laboratories for studying galaxy interactions and their effects on the evolution of galaxies due to their high density and low velocity dispersion. SCG0018-4854 is a remarkably high galaxy density and low velocity dispersion group with evidence of a recent interaction. It has been detected and analyzed at different wavelengths, but its kinematics have never been studied in detail. Methods. We obtained VLT FORS2 optical observations and present spectroscopic and photometric evidence to illustrate how dramatically galaxy interactions have affected each of the four group member galaxies. Results. For each galaxy, we detected peculiar kinematics and evidence of recent star formation. In particular, the gas and stellar radial velocity curves of two galaxies are irregular with a level of asymmetry similar to that of other interacting galaxies. We discovered a bar inside NGC 92 thereby revising a previous morphological classification, and we obtained spectroscopic confirmation of the galactic-scale outflow within NGC 89. Conclusions. The peculiar kinematics and dynamical considerations provide a rough estimate of the age of the latest interaction of τ ≈ 0.2-0.7 Gyr, suggesting that SCG0018-4854 is a young and dynamical group.
We present the analysis of the entire HARPS observations of three stars that host planetary systems: HD 1461, HD 40307, and HD 204313. The data set spans eight years and contains more than 200 ...nightly averaged velocity measurements for each star. This means that it is sensitive to both long-period and low-mass planets and also to the effects induced by stellar activity cycles. We modelled the data using Keplerian functions that correspond to planetary candidates and included the short- and long-term effects of magnetic activity. A Bayesian approach was taken both for the data modelling, which allowed us to include information from activity proxies such as log R'HK in the velocity modelling, and for the model selection, which permitted determining the number of significant signals in the system. The Bayesian model comparison overcomes the limitations inherent to the traditional periodogram analysis. We report an additional super-Earth planet in the HD 1461 system. Four out of the six planets previously reported for HD 40307 are confirmed and characterised. We discuss the remaining two proposed signals. In particular, we show that when the systematic uncertainty associated with the techniques for estimating model probabilities are taken into account, the current data are not conclusive concerning the existence of the habitable-zone candidate HD 40307 g. We also fully characterise the Neptune-mass planet that orbits HD 204313 in 34.9 days.
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