Abstracts of Large Programmes scheduled in Period 92



Le Fevre

We are proposing a Legacy survey of 12,000 galaxies in 1deg$^2$ with VIMOS to study the formation and evolution of galaxies at the key epoch $2.5 \leq z \leq 6.7$, the next frontier beyond the VVDS or zCOSMOS surveys now being finished. This will increase by about one order of magnitude the total number of spectral measurements obtained so far in this redshift range, including $>$300 new galaxies with $z>5$. We will select galaxies in 3 fields (COSMOS, ECDFS, VVDS-02h) to minimise cosmic variance, using a conservative yet efficient set of selection criteria to produce magnitude selected samples at $23 \leq i_{AB} \leq 25$, and flux limited for Lyman$\alpha$ emitters with $1.5\times 10^{-18}$erg.cm$^{-2}$s$^{-1}$. This large sample of galaxies with secure spectroscopic redshifts will enable a number of detailed studies from 3$\times10^9$ to 5$\times10^8$ years after the BigBang, most importantly: (i) the evolution of the global star formation rate and the build up of the mass function for different galaxy populations, (ii) the study of very young galaxies and search for the long sought PopIII stellar populations, (iii) a measurement of the clustering of galaxies to infer the mass growth of underlying dark matter halos, (iv) a measurement of the merger rate to evaluate the contribution of mergers to the mass growth of galaxies at these early epochs. These measurements will be used to build a clear and comprehensive picture describing the physical processes which regulate star formation and stellar mass assembly in galaxies in their early phases of evolution.




The Yarkovsky-O?Keefe-Radzievskii-Paddack (YORP) effect is a torque due to both incident solar radiation pressure and the recoil effect from the anisotropic emission of thermal photons on small bodies in the solar system. It can modify their rotation rates and spin-axis orientations or obliquities. YORP can explain many observed phenomena in asteroidal science. Despite its importance there has only been three YORP detections achieved to date. We propose to use the NTT+EFOSC2 to monitor a large sample of Near-Earth Asteroids to detect the YORP effect. Such a large sample will provide valuable constraints on asteroid surface and shape evolution models as well as models of spin-orbit interactions. We will also use EFOSC2 to acquire optical spectroscopy of all targets for surface characterizations. For a selections of targets we will obtain VLT+VISIR thermal IR imaging, to constrain surface albedos, which in turn will provide more accurate shape models, critical for the YORP analysis.




We propose a four year radial velocity planet search targeting 66 so-called ``solar twin'' stars using HARPS. We have recently shown as a result of our five-fold increase in chemical abundance accuracy that the Sun is chemically unusual compared with the majority of solar-type stars, a signature that we attribute to planet formation proceeding more efficiently in the solar system than around other stars. The proposed planet search will exploit the advantage offered by solar twins to obtain abundances of unmatched accuracy, allowing thus to study the stellar composition -- planet connection to a level that was unthinkable before. Our HARPS survey will quadruple the number of solar twins being searched for planets at high precision, illuminating the relation between chemical anomalies and planet formation in a variety of systems, ranging from stars with no planets detected in their inner regions (systems similar to our own Solar System) to stars with gas and ice giants, and probably super Earths. We are complementing the planet search by measuring with unprecedented accuracy chemical abundances for all sample stars using the 6.5m Magellan telescope. The project will ultimately yield a statistically robust sample of solar twins with homogeneous and tight constraints on both their chemical composition and planetary systems, providing novel insights on the still unknown mechanisms of planet formation.




We want to investigate directly the ``critical metallicity'', i.e.\ the minimum metallicity sufficient for the formation of low-mass stars. Only four of Ultra metal-poor stars are known (UMP stars with [Fe/H]$<$--4) and only about 100 extremely metal-poor stars (EMP stars with [Fe/H]$<$--3). This project has three main goals: {\bf i)~}to determine the metal-weak tail of the Halo metallicity distribution function, below [M/H]=--3.5, where the low resolution SDSS spectra are inadequate; {\bf ii)~}to determine the relative abundance of the elements in EMP-UMP stars, signature of the massive first stars. {\bf iii)~}to determine the trend of the lithium abundance in the matter at the beginning of the Galaxy. The Sloan Digital Sky Survey already gave us the chance to discover the most primordial star known to date, with $\rm [Fe/H]\approx -5$ and NO evidence of enhancement in C and N. The large number of stars observed in SDSS provides a large sample of candidates of extremely low metallicity. X-Shooter has the potentiality of performing the necessary follow-up spectroscopy providing for these stars accurate metallicities and abundance ratios for several key elements (Li, Na, Mg, Al, Ca, Ti, Cr, Sr... ) down to V$=20$.




We are building a new, moderate-resolution stellar spectral library, the X-Shooter Spectral Library (XSL), for use in stellar population modelling. Stellar populations preserve the fossil record of galaxy formation and evolution. We propose here to complete our development of XSL, observing the final 418 of nearly 650 stars. X-Shooter's unique capabilities -- tremendous simultaneous wavelength coverage, and high spectral resolution -- make it possible for the first time to obtain a spectral library of observed stars covering all relevant stars needed for stellar population synthesis of external galaxies, from the ultraviolet all the way to the thermal infrared. The fact that these spectra can be obtained at a resolution of $>$8000 means that stellar population models created from XSL can be used to analyse extragalactic objects ranging from young star clusters to distant globular clusters to galaxies out to significant redshifts. XSL will provide a vital tool for extragalactic astronomers to extract even information from their observations than previously possible.




The detection of extra-solar planets with masses in the super-earth and neptune mass regime represents a benchmark for planet surveys. With the number of detections growing at a steady pace, the properties and true frequency of such systems are slowly being accessed. However, due to selection biases, the frequency of neptune and super-earth planets has not been systematically probed in its whole extent. This is particularly true for the the metal-poor regime, where no specific major survey aiming at the detection of very low mass planets was carried out. Interestingly, however, planet formation models strongly suggest that neptunes and super-earths should be frequent around stars with low metallicity, contrarily to the case for giant planets. Here we propose to complete a previously started survey to test this theoretical finding, by using the HARPS spectrograph to search for very low mass exoplanets around a sample of 109 southern solar-type stars with metallicities ([Fe/H]) below $-$0.4\,dex. Results from P82, P85, and P86 revealed several very good candidates, but the available data is insufficient to allow for a confident detection. Here we aim at obtaining a number of measurements that allows us to compare the statistics of low mass planets orbiting metal-poor stars to the results from the HARPS high precision GTO program (aimed at the solar metallicity regime).




The poor knowledge about how the metallicity of classical Cepheids affects their absolute magnitudes in optical and particularly near-infrared bands has so far prevented an accurate determination of the Hubble constant by using the HST Key Project approach to build the distance ladder out to 20 Mpc with Cepheids. An accurate (1-2\%) measurement of the Hubble constant via Cepheids however is fundamental to avoid degeneracies in $H_{0}$ determinations from the cosmic microwave background. We propose an independent approach to measure the metallicity sensitivity of the Cepheid PL relation by determining accurate distances to 30 SMC Cepheids from the Infrared Surface Brightness Method. Combining the resulting absolute magnitudes of these Cepheids with those for samples of LMC and Milky Way Cepheids whose distances we have already measured in exactly the same way, we will determine the metallicity effect with very high accuracy and pave the way for a truly accurate determination of $H_{0}$ using Cepheids.




The long-standing quest for galaxies in the reionization epoch may be close to an end: ultra-deep IR surveys with HST, VLT and Subaru are finally providing convincing samples of z$\sim$7 candidate galaxies. We have recently spectroscopically confirmed a small sample of galaxies at z$\sim$7, providing the first possible evidence of a decrease in the transmission of Ly$\alpha$ photons compared to z$\sim$6, a predicted signature of an incomplete reionization of the Universe. To provide a definite answer on when and how reionization occurred we now propose to conduct a much larger survey over more than 200 Lyman break galaxies, selected in a homogeneous way from the superb CANDELS data-set, in 3 different fields. Spectroscopic observations will allow us to assess the continuous evolution of the Ly$\alpha$ emission over the range $6 < z < 7.3$, and determine when and how the Ly$\alpha$ started to be quenched by the neutral IGM. From a comparison to models that combine radiative transfer physics with large-scale seminumeric simulations, we will determine the neutral hydrogen fraction of the IGM that is needed to explain the observed evolution at each redshift, and we will assess if the transition to fully reionized IGM was smooth or sharp in time. The observations will also give us a first order view of the complex topology of the reionization process.




Massive stars are key agents in the Universe, driving the evolution of star forming galaxies through their photons, winds and violent deaths at all redshifts. The community devotes large efforts to characterize those processes which have been identified to affect the evolution of massive stars: rotation and stellar winds. Recently, important effects of magnetic fields in massive stars are suggested by observations and by models, and spectacular objects such as gamma-ray bursts and magnetars can not be understood without their consideration. But what is their frequency and field strength distribution, their origin, and what are the evolutionary consequences of magnetic fields in massive stars? We aim at directly addressing these questions through the study of a systematically selected sample of massive OB stars of different ages, considering their spin and their hard X-ray emission. We want to measure the polarization induced in spectral lines by the Zeeman effect. Recent observations showed that FORS\,2 and HARPS are ideal instrument for this. Through (funded) parallel theory projects, we aim to clarify the role of magnetic fields in the advanced stages of massive stars, including their fate as supernova or gamma-ray burst.




The XXL survey, covering 50 deg$^{2}$ , is the largest deep and contiguous XMM-Newton X-ray survey to be carried out. The survey is designed to detect hundreds of galaxy clusters out to $z>1$, with a uniquely well-determined selection function. The combination of a large number of clusters with the availability of X-ray, lensing and S-Z data, will enable robust cluster mass determinations. Added to the precise knowledge of the selection function, {\bf this will provide competitive constraints on the equation of state of dark energy, many years before surveys such as LSST or EUCLID, paving the way for these later surveys}. Furthermore, we will be able to follow the physical processes involved in cluster evolution with unprecedented data quality. Cluster spectroscopic confirmation is crucial for these aims, including the determination of the cluster correlation function which contributes about one half of the dark energy constraints. {\bf We propose to achieve complete redshift measurements for the C1 cluster sample at z$\leq$1,} i.e. $\sim$240 high S/N X-ray clusters. Approximately half of these will be provided by GAMA and VIPERS. To cover the rest will use NTT/EFOSC2 ($\sim$74 z$\leq$0.6 candidates) and VLT/FORS2 ($\sim$45 0.6$\leq$z$\leq$1 candidates) over the 4 next periods. This proposal is a continuation of the current VLT/FORS2 pilot allocation (089.A-0666, cat. A).




We will obtain high-cadence observations with HARPS on a sample of M dwarfs. New data analysis techniques developed by our group and implemented in the HARPS-TERRA software, can achieve sub-m/s RV precisions on M dwarfs and enable a suit of additional new observables. This allows to investigate three fundamental aspects of low mass stars and their planetary systems in a single observational program: 1) Characterization of compact planetary systems with sub-Earth mass objects, 2) Time-resolved analysis of stellar activity and its Doppler signatures, and 3) detection of pulsations and asteroseismic studies. Compact planetary systems will be searched using high precision Doppler measurements. This program can provide the first minimum mass determinations of sub-Earth sized objects, dynamical characterization and first population studies of these peculiar systems. Time-resolved stellar activity analyses combined with wavelength dependent Doppler measurements (also enabled by HARPS-TERRA) will provide important clues to elucidate the connection between Doppler variability, activity and stellar magnetic fields. Pulsations in M dwarfs have recently been theoretical predicted but none have been yet observed. Such detection will enable the use of asteroseismic techniques on cool stars. Given this is uncharted territory, unanticipated discoveries are expected.




We have exploited the widest extragalactic {\it Herschel} imaging surveys to define a uniquely large sample of galaxies that are both faint ({\it ergo} unlensed) and extremely red ({\it ergo} rare and very distant, $z > 4$). We have begun to obtain shallow imaging of 100 of these ultra-red galaxies with LABOCA at 870\,$\mu$m (50\,hr, P90, priority A, via Max Planck). Here, we seek to exploit a representative, securely-detected subset of these SMGs to act as signposts to over-densities in the early dark matter distribution, and hence to the most distant known proto-clusters. Deeper, wider LABOCA imaging will make us sensitive to colder and/or less luminous dusty starbursts in their vicinity, and via deep FORS2 imaging and spectroscopy (of the same area) to less obscured, less dramatic, more numerous galaxy populations (LBGs). Via this comprehensive, joint approach we can determine the relative mean over-densities of their environments, which the Millennium-XXL simulation suggest is required to tell us with any certainty about the subsequent fate (mass at $z=0$) of their super-structures. We will explore 8 such environments, defining the early stages in the evolution of the most massive structures in the Universe, a key phase in their evolution that until now has only been studied in detail by modelling and theory. In total we request 46 and 34\,hr/semester with APEX and VLT, respectively, over P91--94.




The number of planets orbiting M dwarfs increases very steeply with decreasing planetary mass or radius. At small orbital separations, M dwarfs seem to host more super-Earths than FGK stars do, and their super-Earths have a high occurence rate in the habitable zone (Bonfils et al. 2012, A\&A in press.; Howard et al. 2012, ApJS 201, 15). In that context, observing even a small sample of M dwarfs with sensitivity to Earth-mass planets on short to moderate orbital periods will give important new insight on planetary formation. {\bf We thus focus our new \textsc{Harps} Large program on the Earth-mass regime of planet formation. We propose to intensively observe 30 M dwarfs over 3.5 years}, to reach completeness: $-$ for Earth-mass planets with orbital period up to 5 days $-$ for few Earth-mass planets with orbital periods up to the outer edge of the habitable zone ($P<50$ days). In that course, we expect to detect 20$\pm$5 new super-Earths, of which ~2-3 are Earth-mass planets and 4$\pm$2 are habitable zone super-Earths, with one planet likely to transit across its star.




This proposal is a placeholder for extra PESSTO observing runs.




We propose a HARPS radial velocity survey dedicated to the search for close-in ($\leq$ 5 AU) giant planets (GP) around young (from a few Myr to 300 Myr) stars. This survey will bring unique information on the processes at work to form GPs and the timescales associated to planet dynamical evolution, which is thought to play a major role in the early building of planetary systems and could e.g. explain the existence of Hot Jupiters. Combined with other techniques, especially direct imaging with VLT/SPHERE, and also Gaia, our survey will constrain, for the first time, the occurence of giant planets at {\it all separations} to get a unique view of GP systems architectures, test their formation and evolution processes, and to calibrate the luminosity-mass relationship of giant planets.




In recent years multi-colour and transient surveys have lead to a large increase in the number of eclipsing white dwarf plus main-sequence star binaries. These binaries offer us a chance to test some of the fundamental concepts underpinning a wide range of astrophysical problems, ranging from exoplanet studies and supernova Ia, to compact binary evolution and the age of the Galaxy. Lately we have shown that extremely precise mass and radius measurements can be made in these systems, good enough to test models of stellar structure as well as binary evolution. We now intend to extend these studies by measuring the fundamental physical parameters of a large group of eclipsing white dwarf plus main-sequence star binaries using x-shooter on the VLT. This large, uniform sample of binaries will allow us to test the evolutionary models of low-mass stars across the fully convective boundary, and test white dwarf models across their entire permitted mass range. Furthermore, it will allow us to make an accurate white dwarf luminosity function, right back to the formation of the Galaxy, and reveal whether white dwarfs in cataclysmic variables are able to grow and hence are potential supernova Ia sources.




The cold molecular gas reservoirs fueling star-formation in distant galaxies are most effectively studied through observations of \loj CO line emission. Being the second most abundant molecule after H$_2$, \co and \cotwo line emission has been used to infer cold molecular gas masses and measure the kinematic properties of galaxies that existed all the way back to the first billion years after the big bang. Over the past 37 years, studies of nearby galaxies have led to significant samples of CO line emitters being assembled, however, many of these surveys have focused on the most massive galaxies ($M_{*} > 10^{10}$~M$_{\odot}$), while the bulk of the molecular gas in the present-day Universe is contained in lower-mass objects. Here, we propose a large APEX survey of \cotwo line emission in a subsample of 69 galaxies with stellar masses $8.5 < \log{(M_{*}/M_{\odot})} < 10.0$ and redshifts, $0.010 < z < 0.015$. We request 300~hours of poor weather observing time ($PWV < 4$~mm) over the next four semesters (2~years). This survey is designed to detect molecular gas masses as low as $M_{gas} \ga 6.4 \times 10^7$~M$_{\odot}$, allowing us to estimate gas mass fractions ($f \equiv \frac{M_{gas}}{M_{gas} + M_{*}}$) for `normal' galaxies, and determine how these relate to properties such as stellar mass and metallicity. Our proposed survey of Southern galaxies will provide an ideal sample for high-resolution follow-up studies with ALMA, and data would be made public immediately.



van Kempen

The molecular clouds in the Small Magellanic Cloud are the most metal-poor nearby clouds we can observe individually. Therefor they provide a unique laboratory for star formation in low metallicity environments ($<$20$\%$ solar), likely similar to the environments that existed in the early Universe. The MAGMA survey on Mopra surveyed all known molecular clouds with CO in the SMC. Although almost all clouds were detected, these observations were not sufficient to determine the molecular cloud properties. It limited itself as an indicator to the presence of molecular gas and the relation to the dust and [HI] gas. To derive other basic properties of the molecular gas, such as density, temperature and column density , one needs to determine the actual excitation conditions of the molecular gas, including the influence of the high ISRF present in the SMC. As a full complement to the MAGMA survey, we therefor propose to use APEX to observe the entire molecular cloud population in the SMC. This new survey, targetting large maps in $^{12}$CO 2--1 and deep single pointings in $^{13}$CO 2--1 allow us to determine the full excitation conditions in the entire SMC clouds and subsequently draw unique but statistically significant conclusions about the conditions of individual molecular clouds at low metallicity that can be applied to high-z star formation.




The Planck survey is the first all-sky survey capable of blind cluster detection since the ROSAT All Sky Survey (RASS). Recently released to the general community, the Planck catalogue of Sunyaev-Zeldovich sources (PSZ) provides us with a unique sample of objects including a complete census of massive clusters ($M\ga 5\times10^{14}\,M\odot$) out to z$\sim$1 distributed across the sky. Using ESO facilities, NTT/EFOSC2 and VLT/FORS2, in a well coordinated follow-up programme including Northern telescopes, we propose to achieve the full redshift determination of the whole PSZ clusters over the 65\% cleanest sky area. Combining the redshift measurement with the SZ flux from Planck, we will estimate cluster masses for the whole catalogue, filling a unique window in the $M-z$ space with the most massive high-redshift clusters. The evolution of the mass function of this well understood catalogue will be used to put constraints on cosmological parameters, in particular $\sigma_8$ and $\Omega_{\mathrm{m}}$, with an accuracy better than 1\%. With such tight constraints, and in combination with CMB, SZ-selected clusters may put the most stringent limits on the neutrino mass. ESO-NTT and VLT are key facilities for the success of this programme, and their spectroscopic and photometric data will allow us to construct a lasting legacy catalogue of massive clusters for studies of galaxy clusters and the evolution of their constituent galaxies.




A 10-years continuous effort of sub-m/s RV measurements of quiet stars with HARPS led to a breakthrough in the field of exoplanets, unveiling a large population of Neptunes and super-Earths within $\sim$0.5\,AU for more than 50\,\% of solar-type stars in the solar vicinity. We will build upon this past experience, fully exploiting the previous observational effort, to develop a complete view of the architecture of planetary systems from compact close-in systems out to Neptunes at the ice line limit. Intensively observed stars are treasure troves in this context. The large number of observations allows for a deep census of the planetary content, a crucial aspect for the modelling of the dynamical evolution of the systems. We propose a Large Program to focus on 117 of the brightest, quiet G-K dwarfs, closest to the Sun. Our goals are 1) to characterise the full planetary content from close-in Earth mass planets to Neptunes at several AUs, 2) to improve the estimated frequency and mass distribution of terrestrial planets, a key comparison with Kepler results; 3) to derive properties of the lowest mass planets to constrain planet-formation models; 4) to provide priceless targets for space-based transit searches around bright stars with warm Spitzer and CHEOPS, and for potential further characterisation with the E-ELT; and 5) to better understand stellar phenomena. This program is only possible with HARPS.



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Last update: OPO - July 03, 2013