R. Bacon

University of Lyon, Lyons, Rhône-Alpes, France

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Publications (146)251.55 Total impact

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    ABSTRACT: We observed the Hubble Deep Field South with the new panoramic integral field spectrograph MUSE that we built and just commissioned at the VLT. The data cube resulting from 27 hours of integration covers one arcmin^2 field of view at an unprecedented depth with a 1 sigma emission line surface brightness limit of 1x$10^{-19}$ erg/s/cm$^2$/arcsec$^2$ and contains ~90,000 spectra. We present the combined and calibrated data cube, and we perform a first-pass analysis of the sources detected in the HDF-S imaging. We measured the redshifts of 189 sources up to a magnitude F814W = 29.5, increasing by more than an order of magnitude the number of known spectroscopic redshifts in this field. We also discovered 26 Lya emitting galaxies which are not detected in the HST WFPC2 deep broad band images. The intermediate spectral resolution of 2.3{\AA} allows us to separate resolved asymmetric Lya emitters, [O II] emitters, and C III] emitters and the large instantaneous wavelength range of 4500{\AA} helps to identify single emission lines. We also show how the three dimensional information of MUSE helps to resolve sources which are confused at ground-based image quality. Overall, secure identifications are provided for 83% of the 227 emission line sources detected in the MUSE data cube and for 32% of the 586 sources identified in the HST catalog of Casertano et al 2000. The overall redshift distribution is fairly flat to z=6.3, with a reduction between z=1.5 to 2.9, in the well-known redshift desert. The field of view of MUSE also allowed us to detect 17 groups within the field. We checked that the number counts of [O II] and Ly-a emitters are roughly consistent with predictions from the literature. Using two examples we demonstrate that MUSE is able to provide exquisite spatially resolved spectroscopic information on intermediate redshift galaxies present in the field.
    11/2014;
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    ABSTRACT: We present new observations of the lensing cluster SMACSJ2031.8-4036 obtained with the MUSE integral field spectrograph as part of its commissioning on the Very Large Telescope. By providing medium-resolution spectroscopy over the full 4750-9350 Angstroms domain and a 1x1 arcmin2 field of view, MUSE is ideally suited for identifying lensed galaxies in the cluster core, in particular multiple-imaged systems. We perform a redshift analysis of all sources in the datacube and identify a total of 12 systems ranging from $z=1.46$ to $z=6.4$, with all images of each system confirmed by a spectroscopic redshift. This allows us to accurately constrain the cluster mass profile in this region. We foresee that future MUSE observations of cluster cores should help us discover very faint Lyman-alpha emitters thanks to the strong magnification and the high sensitivity of this instrument.
    09/2014;
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    ABSTRACT: MUSE, the Multi Unit Spectroscopic Explorer, is a 2nd generation integral-field spectrograph under final assembly to see first light at the Very Large Telescope in 2013. By capturing ~ 90000 optical spectra in a single exposure, MUSE represents a challenge for data reduction and analysis. We summarise here the main features of the Data Reduction System, as well as some of the tools under development by the MUSE consortium and the DAHLIA team to handle the large MUSE datacubes (about 4x?10^8 pixels) to recover the original astrophysical signal.
    Journées de la Société Française d'Astronomie & d'Astrophysique (SF2A), Nice, France; 10/2012
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    ABSTRACT: MUSE (Multi Unit Spectroscopic Explorer) is an integral-field spectrograph which will be mounted on the Very Large Telescope (VLT). MUSE is being built for ESO by a European consortium under the supervision of the Centre de Recherche Astrophysique de Lyon (CRAL). In this context, CRAL is responsible for the development of dedicated software to help MUSE users prepare and submit their observations. This software, called MUSE-PS, is based on the ESO SkyCat tool that combines visualization of images and access to catalogs and archive data for astronomy. MUSE-PS has been developed as a plugin to SkyCat to add new features specific to MUSE observations. In this paper, we present the MUSE observation preparation tool itself and especially its specific functionalities: definition of the center of the MUSE field of view and orientation, selection of the VLT guide star for the different modes of operations (Narrow Field Mode or Wide Field Mode, with or without AO). We will also show customized displays for MUSE (zoom on specific area, help with MUSE mosaïcing and generic offsets, finding charts …).
    Proc SPIE 09/2012;
  • Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series; 09/2012
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    ABSTRACT: Optical coatings are one of the key elements of the VLT’s second generation instrument MUSE. The Multi Unit Spectroscopic Explorer is developed for the European Southern Observatory (ESO) and will be installed in 2013 at the VLT (Very Large Telescope). MUSE is a panoramic integral field spectrograph (1x1arcmin² Field of View) operating in the visible wavelength range (465 nm - 930 nm). The throughput, which strongly depends on the optical coatings, is one of the most important parameters of the MUSE instrument, which aims at observing very faint objects. This article focuses on the different refractions and reflections required by the optical design of MUSE. Between the output of the VLT and the final detectors of MUSE, photons are typically reflected 7 times by mirrors and transmitted 26 times through antireflective coatings. A comparison between metallic and multi-dielectric coatings is presented here in order to explain the best compromise that has been chosen for MUSE purpose. High reflective multi-dielectric coatings of large bandwidth are rather thick and induce significant stress on the substrate which may bend the substrate. This deformation of mirrors is simulated and compared to measurements on MUSE optics. Finally, systematic optical coating tests have been conducted, so as to check the durability under severe conditions such as humidity, temperature change, abrasion. In the end, the choice of high quality optical coatings should allow MUSE to reach a global throughput higher than 40%.
    Proc SPIE 09/2012;
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    ABSTRACT: MUSE (Multi Unit Spectroscopic Explorer) is a second generation VLT panoramic integral field spectrograph developed for the European Southern Observatory (ESO), operating in the visible wavelength range (0.465-0.93 &#956m). The MUSE instrument is currently under integration and the commissioning is expected to start at the beginning of year 2013. The scientific and technical capabilities of MUSE are described in a series of 19 companion papers. The Fore-Optics (FO), situated at the entrance of MUSE, is used to de-rotate and provide an anamorphic magnification (x 5 / x 2.5) of the 1 arc minute square field of view from the F/15.2 VLT Nasmyth focal plane (Wide Field Mode, WFM). Additional optical elements can be inserted in the optical beam to further increase the magnification by a factor 8 (Narrow Field Mode, NFM). An atmospheric dispersion corrector is also added in the NFM. Two image stabilization units have been developed to ensure a stabilization of the field of view (1/20 of a resolved element) for each observation mode. Environmental values such as temperature and hygrometry are monitored to inform about the observation conditions. All motorized functions and sensors are remote-controlled from the VLT Software via the CAN bus with CANOpen protocol. In this paper, we describe the FO optical, mechanical and control/command electronic concept, development and performance.
    Proc SPIE 09/2012;
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    The Messenger. 03/2012; 147:4-6.
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    ABSTRACT: The ATLAS3D sample includes all nearby ETGs observable fr northern Earth hemisphere, and for this reason we hope its homogeneous data set will ultimately constitute a legacy for future studies. We trust that our and other groups will exploit our data and sample well beyond what we had originally envisioned. Our first steps in the directions outlined above are presented in the following papers, while the other aspects will be presented in subsequent papers of this series. (2 data files).
    VizieR Online Data Catalog. 11/2011;
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    ABSTRACT: We propose a simple model for the origin of fast and slow rotator early-type galaxies (ETG) within the hierarchical Λcold dark matter (ΛCDM) scenario, that is based on the assumption that the mass fraction of stellar discs in ETGs is a proxy for the specific angular momentum expressed via λR. Within our model we reproduce the fraction of fast and slow rotators as a function of magnitude in the ATLAS3D survey, assuming that fast-rotating ETGs have at least 10 per cent of their total stellar mass in a disc component. In agreement with ATLAS3D observations we find that slow rotators are predominantly galaxies with M* > 1010.5 M⊙ contributing ∼20 per cent to the overall ETG population. We show in detail that the growth histories of fast and slow rotators are different, supporting the classification of ETGs into these two categories. Slow rotators accrete between ∼50 and 90 per cent of their stellar mass from satellites and their most massive progenitors have on average up to three major mergers during their evolution. Fast rotators in contrast accrete less than 50 per cent and have on average less than one major merger in their past.We find that the underlying physical reason for the different growth histories is the slowing down and ultimately complete shut-down of gas cooling in massive galaxies. Once cooling and associated star formation in disc stop, galaxies grow via infall from satellites. Frequent minor mergers thereby destroy existing stellar discs via violent relaxation and also tend to lower the specific angular momentum of the main stellar body, lowering λR into the slow rotator regime.On average, the last gas-rich major merger interaction in slow rotators happens at z > 1.5, followed by a series of minor mergers. These results support the idea that kinematically decoupled cores (KDC) form during gas-rich major mergers at high z followed by minor mergers, which build-up the outer layers of the remnant, and make remnants that are initially too flat compared to observations become rounder. Fast rotators are less likely to form such KDCs due to the fact that they have on average less than one major merger in their past.Fast rotators in our model have different formation paths. The majority, 78 per cent, has bulge-to-total stellar mass ratios (B/T) > 0.5 and managed to grow stellar discs due to continued gas cooling or bulges due to frequent minor mergers. The remaining 22 per cent live in high-density environments and consist of low B/T galaxies with gas fractions below 15 per cent, that have exhausted their cold gas reservoir and have no hot halo from which gas can cool. These fast rotators most likely resemble the flattened disc-like fast rotators in the ATLAS3D survey.Our results predict that ETGs can change their state from fast to slow rotator and vice versa, while the former is taking place predominantly at low z (z < 2), the latter is occurring during cosmic epochs when cooling times are short and galaxies gas-rich. We predict that the ratio of the number density of slow to fast rotators is a strong function of redshift, with massive (>1010 M⊙) fast rotators being more than one order of magnitude more frequent at z∼ 2.
    Monthly Notices of the Royal Astronomical Society 10/2011; 417(2):845 - 862. · 5.52 Impact Factor
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    ABSTRACT: The second generation instrument MUSE for the VLT has been designed to profit of the ESO Adaptive Optics Facility (AOF). The two Adaptive Optics (AO) modes (GLAO in Wide Field Mode [WFM] and LTAO in Narrow Field Mode [NFM]) will be used. To achieve its key science goals, MUSE will require information on the full system (Atmosphere, AO, telescope and instrument) image quality and its variation with Field position and wavelength. For example, optimal summation of a large number of deep field exposures in WFM will require a good knowledge of the PSF. In this paper, we will present an exhaustive analysis of the MUSE Wide Field Mode PSF evolution both spatially and spectrally. For that purpose we have coupled a complete AO simulation tool developed at ONERA with the MUSE instrumental PSF simulation. Relative impact of atmospheric and system parameters (seeing, Cn^2, LGS and NGS positions etc ...) with respect to differential MUSE aberrations per channel (i.e. slicer and IFU) is analysed. The results allow us (in close collaboration with astronomers) to define pertinent parameters (fit parameters using a Moffat function) for a PSF reconstruction process (estimation of this parameters using GLAO telemetry) and to propose an efficient and robust algorithm to be implemented in the MUSE pipeline. The extension of the spatial and spectral PSF analysis to the NFM case is discussed and preliminary results are given. Some specific requirements for the generalisation of the GLAO PSF reconstruction process to the LTAO case are derived from these early results.
    09/2011;
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    ABSTRACT: The HARMONI integral field spectrograph concept is one of the two instruments chosen to form the first-light instrument complement at the E-ELT. HARMONI is a work-horse instrument, operating over a large wavelength range (V to K), with many different spatial scales (diffraction limited to seeing limited) and moderate to high spectral resolving power (5000 to 20000). It is designed to work in conjunction with several different AO systems at the E-ELT: GLAO provided by the telescope, LTAO provided by the dedicated facility ATLAS, and SCAO incorporated within the instrument itself. We present the conceptual design of HARMONI, and discuss the challenges involved in working with many different flavours of AO, over a wide range of spatial resolutions. We briefly present the science cases that drive the instrument design, and highlight the innovative aspects of the design, operation and calibration of HARMONI.
    09/2011;
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    ABSTRACT: [Abridged] We present ground-based MDM V-band and Spitzer/IRAC 3.6um-band photometric observations of the 72 representative galaxies of the SAURON Survey. In combination with the SAURON stellar velocity dispersion measured within an effective radius (se), this allows us to explore the location of our galaxies in the main scaling relations. We investigate the dependence of these relations on our recent kinematical classification of early-type galaxies (i.e. Slow/Fast Rotators) and the stellar populations. Slow Rotator and Fast Rotator E/S0 galaxies do not populate distinct locations in the scaling relations, although Slow Rotators display a smaller intrinsic scatter. Surprisingly, extremely young objects do not display the bluest (V-[3.6]) colours in our sample, as is usually the case in optical colours. This can be understood in the context of the large contribution of TP-AGB stars to the infrared, even for young populations, resulting in a very tight (V-[3.6]) - se relation that in turn allows us to define a strong correlation between metallicity and velocity dispersion. Many Sa galaxies appear to follow the Fundamental Plane defined by E/S0 galaxies. Galaxies that appear offset from the relations correspond mostly to objects with extremely young populations, with signs of on-going, extended star formation. We correct for this effect in the Fundamental Plane, by replacing luminosity with stellar mass using an estimate of the stellar mass-to-light ratio, so that all galaxies are part of a tight, single relation. The new estimated coefficients are consistent in both photometric bands and suggest that differences in stellar populations account for about half of the observed tilt with respect to the virial prediction. After these corrections, the Slow Rotator family shows almost no intrinsic scatter around the best-fit Fundamental Plane.
    Monthly Notices of the Royal Astronomical Society 07/2011; 417(3). · 5.52 Impact Factor
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    ABSTRACT: The Multi Unit Spectroscopic Explorer (MUSE) is a second-generation integral-field spectrograph currently in development for the Very Large Telescope (VLT), consisting of 24 Integral Field Units (IFU). This paper presents the methodology for sky subtraction to be used in the MUSE data reduction pipeline. The method is based on the parameterized simulation of the night sky emission processes and the instrument response. In most cases, this method makes a separate sky exposition obsolete. The approach is described and illustrated here using simulated data.
    07/2011;
  • P. Weilbacher, R. Bacon
    07/2011;
  • 07/2011;
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    ABSTRACT: The ATLAS3D project is a multiwavelength survey combined with a theoretical modelling effort. The observations span from the radio to the millimetre and optical, and provide multicolour imaging, two-dimensional kinematics of the atomic (H i), molecular (CO) and ionized gas (Hβ, [O iii] and [N i]), together with the kinematics and population of the stars (Hβ, Fe5015 and Mg b), for a carefully selected, volume-limited (1.16 × 105 Mpc3) sample of 260 early-type (elliptical E and lenticular S0) galaxies (ETGs). The models include semi-analytic, N-body binary mergers and cosmological simulations of galaxy formation. Here we present the science goals for the project and introduce the galaxy sample and the selection criteria. The sample consists of nearby (D < 42 Mpc, |δ− 29°| < 35°, |b| > 15°) morphologically selected ETGs extracted from a parent sample of 871 galaxies (8 per cent E, 22 per cent S0 and 70 per cent spirals) brighter than MK < −21.5 mag (stellar mass M★≳ 6 ×109 M⊙). We analyse possible selection biases and we conclude that the parent sample is essentially complete and statistically representative of the nearby galaxy population. We present the size–luminosity relation for the spirals and ETGs and show that the ETGs in the ATLAS3D sample define a tight red sequence in a colour–magnitude diagram, with few objects in the transition from the blue cloud. We describe the strategy of the SAURON integral field observations and the extraction of the stellar kinematics with the ppxf method. We find typical 1σ errors of ΔV≈ 6 km s−1, Δσ≈ 7 km s−1, Δh3≈Δh4≈ 0.03 in the mean velocity, the velocity dispersion and Gauss–Hermite (GH) moments for galaxies with effective dispersion σe≳ 120 km s−1. For galaxies with lower σe (≈40 per cent of the sample) the GH moments are gradually penalized by ppxf towards zero to suppress the noise produced by the spectral undersampling and only V and σ can be measured. We give an overview of the characteristics of the other main data sets already available for our sample and of the ongoing modelling projects.
    Monthly Notices of the Royal Astronomical Society 05/2011; 413(2):813 - 836. · 5.52 Impact Factor
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    ABSTRACT: We report recent results from the photometric follow-up study we are conducting in the context of the SAURON project. We use ground-based MDM V -band and Spitzer/IRAC 3.6 mum imaging to characterise our sample of E, S0 and Sa galaxies photometrically. Combined with SAURON integral-field spectroscopic observations, this information allows us to explore and understand the location of these galaxies on the Fundamental Plane relation, providing an important diagnostic tool to study their formation and evolution.
    EAS Publications Series 01/2011; 48:411-412.
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    ABSTRACT: MUSE (Multi Unit Spectroscopic Explorer) is a second generation instrument developed for ESO (European Southern Observatory) and will be assembled to the VLT (Very Large Telescope) in 2012. The MUSE instrument can simultaneously record 90.000 spectra in the visible wavelength range (465-930nm), across a 1*1arcmin2 field of view, thanks to 24 identical Integral Field Units (IFU). A collaboration of 7 institutes has successfully passed the Final Design Review and is currently working on the first sub-assemblies. The sharing of performances has been based on 5 main functional sub-systems. The Fore Optics sub-system derotates and anamorphoses the VLT Nasmyth focal plane image, the Splitting and Relay Optics associated with the Main Structure are feeding each IFU with 1/24th of the field of view. Each IFU is composed of a 3D function insured by an image slicer system and a spectrograph, and a detection function by a 4k*4k CCD cooled down to 163°K. The 5th function is the calibration and data reduction of the instrument. This article depicts the breakdown of performances between these sub-systems (throughput, image quality...), and underlines the constraining parameters of the interfaces either internal or with the VLT. The validation of all these requirements is a critical task started a few months ago which requires a clear traceability and performances analysis.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
    07/2010;

Publication Stats

2k Citations
251.55 Total Impact Points

Institutions

  • 2003–2011
    • University of Lyon
      Lyons, Rhône-Alpes, France
  • 2010
    • Claude Bernard University Lyon 1
      Villeurbanne, Rhône-Alpes, France
  • 2007–2010
    • Ecole normale supérieure de Lyon
      Lyons, Rhône-Alpes, France
  • 2007–2009
    • French National Centre for Scientific Research
      • Centre de Recherche Astrophysique de Lyon (CRAL)
      Lutetia Parisorum, Île-de-France, France
  • 2004–2008
    • Cancer Research Center of Lyon
      Lyons, Rhône-Alpes, France
  • 2006
    • University of Hertfordshire
      • Centre for Astrophysics Research (CAR)
      Hatfield, ENG, United Kingdom
  • 2000–2001
    • Johns Hopkins University
      Baltimore, Maryland, United States
  • 1987
    • Max Planck Institute for Astronomy
      Heidelburg, Baden-Württemberg, Germany