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VANDELS is a deep spectroscopic survey, performed with the VIMOS instrument at VLT, aimed at studying in detail the physical properties of high-redshift galaxies. VANDELS targeted about 2100 sources at 1

We study the mean properties of a large representative sample of 217 galaxies showing CIII] emission at $2

The estimate of stellar metallicities (Z*) of high-z galaxies are of paramount importance in order to understand the complexity of dust effects and the reciprocal interrelations among stellar mass, dust attenuation, stellar age, and metallicity. Benefiting from uniquely deep FUV spectra of >500 star-forming galaxies at redshifts 2

Aims. Our aim is to estimate the intergalactic medium transmission towards UV-selected star-forming galaxies at redshift 4 and above and study the effect of the dust attenuation on these measurements. Methods. The ultra-violet spectrum of high redshift galaxies is a combination of their intrinsic emission and the effect of the Inter-Galactic medium (IGM) absorption along their line of sight. Using data coming from the unprecedented deep spectroscopy from the VANDELS ESO public survey carried out with the VIMOS instrument we compute both the dust extinction and the mean transmission of the IGM as well as its scatter from a set of 281 galaxies at z>3.87. Because of a degeneracy between the dust content of the galaxy and the IGM, we first estimate the stellar dust extinction parameter E(B-V) and study the result as a function of the dust prescription. Using these measurements as constraint for the spectral fit we estimate the IGM transmission Tr(Lyalpha). Both photometric and spectroscopic SED fitting are done using the SPectroscopy And photometRy fiTting tool for Astronomical aNalysis (SPARTAN) that is able to fit the spectral continuum of the galaxies as well as photometric data. Results. Using the classical Calzetti's attenuation law we find that E(B-V) goes from 0.11 at z=3.99 to 0.08 at z=5.15. These results are in very good agreement with previous measurements from the literature. We estimate the IGM transmission and find that the transmission is decreasing with increasing redshift from Tr(Lyalpha)=0.53 at z=3.99 to 0.28 at z=5.15. We also find a large standard deviation around the average transmission that is more than 0.1 at every redshift. Our results are in very good agreement with both previous measurements from AGN studies and with theoretical models., Comment: Accepted for publication in A&A

Strong He II emission is produced by low-metallicity stellar populations. Here, we aim to identify and study a sample of He II $\lambda 1640$-emitting galaxies at redshifts of $z \sim 2.5-5$ in the deep VANDELS spectroscopic survey.. We identified a total of 33 Bright He II emitters (S/N > 2.5) and 17 Faint emitters (S/N < 2.5) in the VANDELS survey and used the available deep multi-wavelength data to study their physical properties. After identifying seven potential AGNs in our sample and discarding them from further analysis, we divided the sample of \emph{Bright} emitters into 20 \emph{Narrow} (FWHM < 1000 km s$^{-1}$) and 6 \emph{Broad} (FWHM > 1000 km s$^{-1}$) He II emitters. We created stacks of Faint, Narrow, and Broad emitters and measured other rest-frame UV lines such as O III] and C III] in both individual galaxies and stacks. We then compared the UV line ratios with the output of stellar population-synthesis models to study the ionising properties of He II emitters. We do not see a significant difference between the stellar masses, star-formation rates, and rest-frame UV magnitudes of galaxies with He II and no He II emission. The stellar population models reproduce the observed UV line ratios from metals in a consistent manner, however they under-predict the total number of \heii ionising photons, confirming earlier studies and suggesting that additional mechanisms capable of producing He II are needed, such as X-ray binaries or stripped stars. The models favour subsolar metallicities ($\sim0.1Z_\odot$) and young stellar ages ($10^6 - 10^7$ years) for the He II emitters. However, the metallicity measured for He II emitters is comparable to that of non-He II emitters at similar redshifts. We argue that galaxies with He II emission may have undergone a recent star-formation event, or may be powered by additional sources of He II ionisation., Comment: 21 pages, 11 figures (including appendix), Accepted for publication in A&A

We present the results of a study utilising ultra-deep, rest-frame UV, spectroscopy to quantify the relationship between stellar mass and stellar metallicity for 681 star-forming galaxies at $2.5

We present a Bayesian full-spectral-fitting analysis of 75 massive ($M_* > 10^{10.3} M_\odot$) UVJ-selected galaxies at redshifts of $1.0 < z < 1.3$, combining extremely deep rest-frame ultraviolet spectroscopy from VANDELS with multi-wavelength photometry. By the use of a sophisticated physical plus systematic uncertainties model, constructed within the Bagpipes code, we place strong constraints on the star-formation histories (SFHs) of individual objects. We firstly constrain the stellar mass vs stellar age relationship, finding a steep trend towards earlier average formation with increasing stellar mass of $1.48^{+0.34}_{-0.39}$ Gyr per decade in mass, although this shows signs of flattening at $M_* > 10^{11} M_\odot$. We show that this is consistent with other spectroscopic studies from $0 < z < 2$. This relationship places strong constraints on the AGN-feedback models used in cosmological simulations. We demonstrate that, although the relationships predicted by Simba and IllustrisTNG agree well with observations at $z=0.1$, they are too shallow at $z=1$, predicting an evolution of $<0.5$ Gyr per decade in mass. Secondly, we consider the connections between green-valley, post-starburst and quiescent galaxies, using our inferred SFH shapes and the distributions of galaxy physical properties on the UVJ diagram. The majority of our lowest-mass galaxies ($M_* \sim 10^{10.5} M_\odot$) are consistent with formation in recent ($z<2$), intense starburst events, with timescales of $\lesssim500$ Myr. A second class of objects experience extended star-formation epochs before rapidly quenching, passing through both green-valley and post-starburst phases. The most massive galaxies in our sample are extreme systems: already old by $z=1$, they formed at $z\sim5$ and quenched by $z=3$. However, we find evidence for their continued evolution through both AGN and rejuvenated star-formation activity., Comment: 25 pages, 13 figures, MNRAS accepted

We investigate the physical properties of a sample of 52 Ly{\alpha} emitting galaxies in the VANDELS survey, with particular focus on the role of kinematics and neutral hydrogen column density in the escape and spatial distribution of Ly{\alpha} photons. For these galaxies, we derive different physical properties and characterize the Ly{\alpha} emission in terms of kinematics, EW, FWHM and spatial extension and then estimate the velocity of the neutral outflowing gas. We reproduce some of the well known correlations between Ly{\alpha} EW and stellar mass, dust extinction and UV \b{eta} slope, in the sense that the emission line appears brighter in lower mass, less dusty and bluer galaxies. We do not find any correlation with the SED-derived star formation rate, while we find that galaxies with brighter Ly{\alpha} tend to be more compact both in UV and in Ly{\alpha}. Our data reveal a new interesting correlation between the Ly{\alpha} velocity and the offset of the inter-stellar absorption lines with respect to the systemic redshift, in the sense that galaxies with larger inter-stellar medium (ISM) out-flow velocities show smaller Ly{\alpha} velocity shifts. We interpret this relation in the context of the shell-model scenario, where the velocity of the ISM and the HI column density contribute together in determining the Ly{\alpha} kinematics. In support to our interpretation, we observe that galaxies with high HI column densities have much more extended Ly{\alpha} spatial profiles, a sign of increased scattering. However, we do not find any evidence that the HI column density is related to any other physical properties of the galaxies, although this might be due in part to the limited range of parameters that our sample spans., Comment: submitted to A&A

We establish a robust statistical description of the star-forming galaxy population at the end of cosmic HI reionization ($5.0\le{}z\le6.6$) from a large sample of 52 galaxies with spectroscopically confirmed redshifts from the VIMOS UltraDeep Survey. We identify galaxies with Ly$\alpha$ either in absorption or in emission, at variance with most spectroscopic samples in the literature where Ly$\alpha$ emitters dominate. We find that star-forming galaxies at these redshifts are distributed along a main sequence in the stellar mass vs. SFR plane. We report a flat evolution of the sSFR(z) in 32. The bright end of the Ly$\alpha$ luminosity function has a high number density, indicating a significant star formation activity concentrated in the brightest Ly$\alpha$ emitters (LAE) at these redshifts. LAE with EW>25\AA ~contribute to about 75\% of the total UV-derived SFRD. While our analysis favors a low dust content in 5.0

We present the results of CANDELSz7, an ESO large program aimed at confirming spectroscopically a homogeneous sample of z~6 and z~7 star forming galaxies. The candidates were selected in the GOODS-South, UDS and COSMOS fields using the official CANDELS catalogs based on H160-band detections. Standard color criteria, which were tailored depending on the ancillary multi-wavelength data available for each field, were applied to select more than 160 candidate galaxies at z~6 and z~7. Deep medium resolution FORS2 spectroscopic observations were then conducted with integration times ranging from 12 to 20 hours, to reach a Lyalpha flux limit of approximately 1-3x 10-18 erg/s/cm^2 at 3sigma. For about 40% of the galaxies we could determine a spectroscopic redshift, mainly through the detection of a single emission line that we interpret as Lyalpha emission, or for some of the brightest objects (H160< 25.5) from the presence of faint continuum and sharp drop that we interpret as a Lyman break. In this paper we present the redshifts and main properties of 65 newly confirmed high redshift galaxies. Adding previous proprietary and archival data we assemble a sample of ~260 galaxies that we use to explore the evolution of the Lyalpha fraction in Lyman break galaxies and the change in the shape of the emission line between z~6 and z~7. We also discuss the accuracy of the CANDELS photometric redshifts in this redshift range., Comment: Accepted for publication in Astronomy & Astrophysics

We present deep spectroscopic follow-up observations of the Bremer Deep Field (BDF) where the two $z\sim$7 bright Ly$\alpha$ emitters (LAE) BDF521 and BDF3299 were previously discovered by Vanzella et al. (2011) and where a factor of $\sim$3-4 overdensity of faint LBGs has been found by Castellano et al. (2016). We confirm a new bright Ly$\alpha$ emitter, BDF2195, at the same redshift of BDF521, $z=7.008$, and at only $\sim$90 kpc physical distance from it, confirming that the BDF area is likely an overdense, reionized region. A quantitative assessment of the Ly$\alpha$ fraction shows that the number of detected bright emitters is much higher than the average found at z$\sim$7, suggesting a high Ly$\alpha$ transmission through the inter-galactic medium (IGM). However, the line visibility from fainter galaxies is at odds with this finding, since no Ly$\alpha$ emission is found in any of the observed candidates with $M_{UV}>$-20.25. This discrepancy can be understood either if some mechanism prevents Ly$\alpha$ emission from fainter galaxies within the ionized bubbles from reaching the observer, or if faint galaxies are located outside the reionized area and bright LAEs are solely responsible for the creation of their own HII regions. A thorough assessment of the nature of the BDF region and of its sources of re-ionizing radiation will be made possible by JWST spectroscopic capabilities., Comment: Accepted for publication in The Astrophysical Journal Letters. 6 pages, 3 figures

We report the discovery of the most distant radio galaxy to date, TGSS1530 at a redshift of $z=5.72$ close to the presumed end of the Epoch of Reionisation. The radio galaxy was selected from the TGSS ADR1 survey at 150 MHz for having to an ultra-steep spectral index, $\alpha^{\textrm{150 MHz}}_{\textrm{1.4 GHz}} = -1.4$ and a compact morphology obtained using VLA imaging at 1.4 GHz. No optical or infrared counterparts for it were found in publicly available sky surveys. Follow-up optical spectroscopy at the radio position using GMOS on Gemini North revealed the presence of a single emission line. We identify this line as Lyman alpha at $z=5.72$, because of its asymmetric line profile, the absence of other optical/UV lines in the spectrum and a high equivalent width. With a Ly$\alpha$ luminosity of $5.7 \times 10^{42}$ erg s$^{-1}$ and a FWHM of $370$ km s$^{-1}$, TGSS1530 is comparable to `non-radio' Lyman alpha emitters (LAEs) at a similar redshift. However, with a radio luminosity of $\log L_{\textrm{150 MHz}} = 29.1$ W Hz$^{-1}$ and a deconvolved physical size $3.5$ kpc, its radio properties are similar to other known radio galaxies at $z>4$. Subsequent $J$ and $K$ band imaging using LUCI on the Large Binocular Telescope resulted in non-detection of the host galaxy down to $3\sigma$ limits of $J>24.4$ and $K>22.4$ (Vega). The $K$ band limit is consistent with $z>5$ from the $K-z$ relation for radio galaxies, suggesting stellar mass limits using simple stellar population models of $M_{\textrm{stars}}< 10^{10.5}$ $M_\odot$. Its high redshift coupled with relatively small radio and Ly$\alpha$ sizes suggest that TGSS1530 may be a radio galaxy in an early phase of its evolution., Comment: 11 pages, 7 figures. Latest published version 10 October 2018

This paper describes the observations and the first data release (DR1) of the ESO public spectroscopic survey "VANDELS, a deep VIMOS survey of the CANDELS CDFS and UDS fields". VANDELS' main targets are star-forming galaxies at 2.4

VANDELS is a uniquely-deep spectroscopic survey of high-redshift galaxies with the VIMOS spectrograph on ESO's Very Large Telescope (VLT). The survey has obtained ultra-deep optical (0.48 < lambda < 1.0 micron) spectroscopy of ~2100 galaxies within the redshift interval 1.0 < z < 7.0, over a total area of ~0.2 sq. degrees centred on the CANDELS UDS and CDFS fields. Based on accurate photometric redshift pre-selection, 85% of the galaxies targeted by VANDELS were selected to be at z>=3. Exploiting the red sensitivity of the refurbished VIMOS spectrograph, the fundamental aim of the survey is to provide the high signal-to-noise ratio spectra necessary to measure key physical properties such as stellar population ages, masses, metallicities and outflow velocities from detailed absorption-line studies. Using integration times calculated to produce an approximately constant signal-to-noise ratio (20 < t_int < 80 hours), the VANDELS survey targeted: a) bright star-forming galaxies at 2.4 < z < 5.5, b) massive quiescent galaxies at 1.0 < z < 2.5, c) fainter star-forming galaxies at 3.0 < z < 7.0 and d) X-ray/Spitzer-selected active galactic nuclei and Herschel-detected galaxies. By targeting two extragalactic survey fields with superb multi-wavelength imaging data, VANDELS will produce a unique legacy data set for exploring the physics underpinning high-redshift galaxy evolution. In this paper we provide an overview of the VANDELS survey designed to support the science exploitation of the first ESO public data release, focusing on the scientific motivation, survey design and target selection., Comment: 19 pages, 9 figures, accepted for publication in MNRAS

We present the results of a new study of dust attenuation at redshifts $3 < z < 4$ based on a sample of $236$ star-forming galaxies from the VANDELS spectroscopic survey. Motivated by results from the First Billion Years (FiBY) simulation project, we argue that the intrinsic spectral energy distributions (SEDs) of star-forming galaxies at these redshifts have a self-similar shape across the mass range $8.2 \leq$ log$(M_{\star}/M_{\odot}) \leq 10.6$ probed by our sample. Using FiBY data, we construct a set of intrinsic SED templates which incorporate both detailed star formation and chemical abundance histories, and a variety of stellar population synthesis (SPS) model assumptions. With this set of intrinsic SEDs, we present a novel approach for directly recovering the shape and normalization of the dust attenuation curve. We find, across all of the intrinsic templates considered, that the average attenuation curve for star-forming galaxies at $z\simeq3.5$ is similar in shape to the commonly-adopted Calzetti starburst law, with an average total-to-selective attenuation ratio of $R_{V}=4.18\pm0.29$. We show that the optical attenuation ($A_V$) versus stellar mass ($M_{\star}$) relation predicted using our method is consistent with recent ALMA observations of galaxies at $2

We analyze the CIII]-1908\AA emission properties in a sample of 3899 star-forming galaxies (SFGs) at 23\AA, including 20% with 310\AA. A significant fraction of 1.2% of SFGs presents strong CIII] emission 2010^10 MSun at z~3 into the population of quiescent galaxies observed at redshift z~1-2., Comment: 19 pages, 14 figures, submitted to A&A

To identify the galaxies responsible for the reionization of the Universe, we must rely on the investigation of the Lyman Continuum (LyC) properties of z<5 star-forming galaxies, where we can still directly observe their ionizing radiation. We selected a sample of 201 star-forming galaxies from the Vimos Ultra Deep Survey at 3.570{\AA}, Lya(ext)<5.7kpc, rUV<0.3kpc and |Dv Lya|<200km/s, stacked all the galaxies in each subsample and measured the flux density ratio fnu(895)/fnu(1470), that we consider to be a proxy for LyC emission. We compared these ratios to those obtained for the complementary samples. We find that the stacks of galaxies which are UV compact (rUV<0.3kpc) and have bright Lya emission (EWLya>70{\AA}), have much higher LyC fluxes compared to the rest of the galaxy population in agreement with theoretical studies and previous observational works. We also find that galaxies with low Lya(ext) have the highest LyC flux: this new correlation seems even stronger than the correlations with high EWLya and small rUV. These results assume that the stacks from all the subsamples present the same statistical contamination from lower redshift interlopers. If we subtract a statistical contamination from low redshift interlopers obtained with dedicated Monte Carlo simulations, from the flux density ratios (fnu(895)/fnu(1470)) of the significant subsamples we find that these samples contain real LyC leaking flux with a very high probability, but the true average escape fractions remain uncertain. Our work indicates that galaxies with very high EWLya, small Lya(ext) and small rUV are very likely the best candidates to show LyC radiation at z=4 and could therefore be the galaxies that contributed more to reionization., Comment: Accepted by A&A

We selected a sample of 76 Lya emitting galaxies from the VIMOS Ultra Deep Survey (VUDS) at 2300km/sec. An ISM with this value of NHI would favour a large amount of scattering events, especially when the medium is static, so it can explain large values of Ext(Lya-C) and small EW(Lya). On the contrary, an ISM with a lower NHI, but large velocity outflows would lead to a Lya spatial profile peaked at the galaxy center (i.e. low values of Ext(Lya-C)) and to a large EW(Lya), as we see in our data. Our results and their interpretation via radiative-transfer models tell us that it is possible to use Lya to study the properties of the HI gas., Comment: Accepted on May 2017

The reionization of the Universe is one of the most important topics of present day astrophysical research. The most plausible candidates for the reionization process are star-forming galaxies, which according to the predictions of the majority of the theoretical and semi-analytical models should dominate the HI ionizing background at z~3. We aim at measuring the Lyman continuum escape fraction, which is one of the key parameters to compute the contribution of star-forming galaxies to the UV background. We have used ultra-deep U-band imaging (U=30.2mag at 1sigma) by LBC/LBT in the CANDELS/GOODS-North field, as well as deep imaging in COSMOS and EGS fields, in order to estimate the Lyman continuum escape fraction of 69 star-forming galaxies with secure spectroscopic redshifts at 3.27L*), while for the faint population (L=0.2L*) the limit to the escape fraction is ~10%. We have computed the contribution of star-forming galaxies to the observed UV background at z~3 and we have found that it is not enough to keep the Universe ionized at these redshifts, unless their escape fraction increases significantly (>10%) at low luminosities (M1500>-19). We compare our results on the Lyman continuum escape fraction of high-z galaxies with recent estimates in the literature and discuss future prospects to shed light on the end of the Dark Ages. In the future, strong gravitational lensing will be fundamental to measure the Lyman continuum escape fraction down to faint magnitudes (M1500~-16) which are inaccessible with the present instrumentation on blank fields., Comment: Accepted for publication in A&A, 16 pages, 6 figures

Determining the average fraction of Lyman continuum (LyC) photons escaping high redshift galaxies is essential for understanding how reionization proceeded in the z>6 Universe. We want to measure the LyC signal from a sample of sources in the Chandra Deep Field South (CDFS) and COSMOS fields for which ultra-deep VIMOS spectroscopy as well as multi-wavelength Hubble Space Telescope (HST) imaging are available. We select a sample of 46 galaxies at $z\sim 4$ from the VIMOS Ultra Deep Survey (VUDS) database, such that the VUDS spectra contain the LyC part of the spectra, that is, the rest-frame range $880-910\AA$. Taking advantage of the HST imaging, we apply a careful cleaning procedure and reject all the sources showing nearby clumps with different colours, that could potentially be lower-redshift interlopers. After this procedure, the sample is reduced to 33 galaxies. We measure the ratio between ionizing flux (LyC at $895\AA$) and non-ionizing emission (at $\sim 1500 \AA$) for all individual sources. We also produce a normalized stacked spectrum of all sources. Assuming an intrinsic average $L_{\nu}(1470)/L_{\nu}(895)$ of 3, we estimate the individual and average relative escape fraction. We do not detect ionizing radiation from any individual source, although we identify a possible LyC emitter with very high Ly$\alpha$ equivalent width (EW). From the stacked spectrum and assuming a mean transmissivity for the sample, we measure a relative escape fraction $f_{esc}^{rel}=0.09\pm0.04$. We also look for correlations between the limits in the LyC flux and source properties and find a tentative correlation between LyC flux and the EW of the Ly$\alpha$ emission line. Our results imply that the LyC flux emitted by $V=25-26$ star-forming galaxies at z$\sim$4 is at most very modest, in agreement with previous upper limits from studies based on broad and narrow band imaging., Comment: accepted by A&A updated fesc,rel value

This paper presents 1463 times of minima for 455 objects acquired by 46 members and cooperating observers of the Variable Star and Exoplanet Section of the Czech Astronomical Society (B.R.N.O. Observing project). Observations were carried out between October 2013 - September 2014. Some neglected southern eclipsing binaries and newly discovered stars by the observers of project B.R.N.O. are included in the list., Comment: Published in OEJV, 66 pages, 1 figure

LISA Pathfinder is a mission planned by the European Space Agency to test the key technologies that will allow the detection of gravitational waves in space. The instrument on-board, the LISA Technology package, will undergo an exhaustive campaign of calibrations and noise characterisation campaigns in order to fully describe the noise model. Data analysis plays an important role in the mission and for that reason the data analysis team has been developing a toolbox which contains all the functionalities required during operations. In this contribution we give an overview of recent activities, focusing on the improvements in the modelling of the instrument and in the data analysis campaigns performed both with real and simulated data., Comment: Plenary talk presented at the 9th International LISA Symposium, 21-25 May 2012, Paris

Searches for planetary transits carried out in open and globular clusters have yielded to date only a handful of weak, unconfirmed candidates. These results have been interpreted either as being insignificant, or as evidence that the cluster chemical or dynamical environment inhibits the planetary formation or survival. Most campaigns were limited by small sample statistics or systematics from ground-based photometry. In this work we performed a search for transiting planets and variables in a deep stellar field of NGC 6397 imaged by HST-ACS for 126 orbits. We analyzed 5,078 light curves, including a pure sample of 2,215 cluster-member M0-M9 dwarfs. The light curves have been corrected for systematic trends and inspected with several tools. No high-significance planetary candidate is detected. We compared this null detection with the most recent results from Kepler, showing that no conclusive evidence of lower planet incidence can be drawn. However, a very small photometric jitter is measured for early-M cluster members (<~2 mmag on 98% of them), which may be worth targeting in the near future with more optimized campaigns. Twelve variable stars are reported for the first time., Comment: 10 pages, 6 figures, 1 table; accepted for publication in A&A on February 16, 2012. Typos corrected. One figure and a short final note added

The precursor ESA mission LISA-Pathfinder, to be flown in 2013, aims at demonstrating the feasibility of the free-fall, necessary for LISA, the upcoming space-born gravitational wave observatory. LISA Technology Package (LTP) is planned to carry out a number of experiments, whose main targets are to identify and measure the disturbances on each test-mass, in order to reach an unprecedented low-level residual force noise. To fulfill this plan, it is then necessary to correctly design, set-up and optimize the experiments to be performed on-flight and do a full system parameter estimation. Here we describe the progress on the non-linear analysis using the methods developed in the framework of the \textit{LTPDA Toolbox}, an object-oriented MATLAB Data Analysis environment: the effort is to identify the critical parameters and remove the degeneracy by properly combining the results of different experiments coming from a closed-loop system like LTP., Comment: 6 pages, 2 figures, 1 table, Proceedings of the 8th International LISA Symposium

LISA is the upcoming space-based Gravitational Wave telescope. LISA Pathfinder, to be launched in the coming years, will prove and verify the detection principle of the fundamental Doppler link of LISA on a flight hardware identical in design to that of LISA. LISA Pathfinder will collect a picture of all noise disturbances possibly affecting LISA, achieving the unprecedented pureness of geodesic motion necessary for the detection of gravitational waves. The first steps of both missions will crucially depend on a very precise calibration of the key system parameters. Moreover, robust parameters estimation is of fundamental importance in the correct assessment of the residual force noise, an essential part of the data processing for LISA. In this paper we present a maximum likelihood parameter estimation technique in time domain being devised for this calibration and show its proficiency on simulated data and validation through Monte Carlo realizations of independent noise runs. We discuss its robustness to non-standard scenarios possibly arising during the real-life mission, as well as its independence to the initial guess and non-gaussianities. Furthermore, we apply the same technique to data produced in mission-like fashion during operational exercises with a realistic simulator provided by ESA., Comment: 16 pages (two columns), 15 figures, 5 tables, submitted to Phys. Rev. D

This paper presents a quantitative assessment of the performance of the upcoming LISA Pathfinder geodesic explorer mission. The findings are based on the results of extensive ground testing and simulation campaigns using flight hardware and flight control and operations algorithms. The results show that, for the central experiment of measuring the stray differential acceleration between the LISA test masses, LISA Pathfinder will be able to verify the overall acceleration noise to within a factor two of the LISA requirement at 1 mHz and within a factor 6 at 0.1 mHz. We also discuss the key elements of the physical model of disturbances, coming from LISA Pathfinder and ground measurement, that will guarantee the LISA performance., Comment: Proceedings of the 8th LISA Symposium. To appear Class. Quantum Grav. 28 (2011)

We calculate the effect of the Earth-Moon (EM) system on the free-fall motion of LISA test masses. We show that the periodic gravitational pulling of the EM system induces a resonance with fundamental frequency 1 yr^-1 and a series of periodic perturbations with frequencies equal to integer harmonics of the synodic month (9.92 10^-7 Hz). We then evaluate the effects of these perturbations (up to the 6th harmonics) on the relative motions between each test masses couple, finding that they range between 3mm and 10pm for the 2nd and 6th harmonic, respectively. If we take the LISA sensitivity curve, as extrapolated down to 10^-6 Hz, we obtain that a few harmonics of the EM system can be detected in the Doppler data collected by the LISA space mission. This suggests that the EM system gravitational near field could provide an absolute calibration for the LISA sensitivity at very low frequencies., Comment: 15 pages, 5 figures

Context. We present a photometric and astrometric catalog of 187963 stars located in the field around the old super-metal-rich Galactic open cluster NGC 6253. The total field-of-view covered by the catalog is 34' x 33'. In this field, we provide CCD BVRI photometry. For a smaller region close to the cluster's center, we also provide near-infrared JHK photometry. Aims. We analyze the properties of NGC 6253 by using our new photometric data and astrometric membership. Methods. In June 2004, we targeted the cluster during a 10 day multi-site campaign, which involved the MPG/ESO 2.2m telescope with its wide-field imager and the Anglo-Australian 3.9m telescope, equipped with the IRIS2 near-infrared imager. Archival CCD images of NGC 6253 were used to derive relative proper motions and to calculate the cluster membership probabilities. Results. We have refined the cluster's fundamental parameters, deriving (V_0-M_v)=11.15, E(B - V)=0.15, E(V - I)=0.25, E(V - J)=0.50, and E(V - H)=0.55. The color excess ratios obtained using both the optical and near infrared colors indicate a normal reddening law in the direction of NGC 6253. The age of NGC 6253 at 3.5 Gyr, determined from our best-fitting isochrone appears to be slightly older than the previous estimates. Finally, we estimated the binary fraction among the cluster members to be \sim20%-30% and identified 11 blue straggler candidates., Comment: 16 pages, 13 figures, 11 tables. Accepted for publication in A&A. Catalog avaiable via CDS

We consider the problem of oscillation damping in air of a thermally actuated microlever as it is gradually approached towards an infinite wall in parallel geometry. As the gap is decreased from 20 nm down to 400 nm, we observe the increasing damping of the lever Brownian motion in the fluid laminar regime. This manifests itself as a linear decrease with distance of the lever quality factor accompanied by a dramatic softening of its resonance, and eventually leads to the freezing of the CL oscillation. We are able to quantitatively explain this behavior by analytically solving the Navier-Stokes equation with perfect slip boundary conditions. Our findings may have implications for microfluidics and micro- nano-electromechanical applications., Comment: Phys. Rev. Lett.: submitted 6 February 2009 ; Editorially approved for publication 3 June 2009

Aims: This work presents a high--precision variability survey in the field of the old, super metal-rich open cluster NGC 6791. Methods: The data sample consists of more than 75,000 high-precision CCD time series measurements in the V band obtained mainly at the Canada-France-Hawaii Telescope, with additional data from S. Pedro Martir and Loiano observatories, over a time span of ten nights. The field covers an area of 42x28 arcmin^2. Results: We have discovered 260 new variables and re-determined periods and amplitudes of 70 known variable stars. By means of a photometric evaluation of the membership in NGC 6791, and a preliminary membership based on the proper motions, we give a full description of the variable content of the cluster and surrounding field in the range 16