34 research outputs found

    The Planetary Mass Companion 2MASS1207-3932 B: Temperature, Mass and Evidence for an Edge-On Disk

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    We present J-band imaging and H+K-band low-resolution spectroscopy of 2MASS1207-3932 AB, obtained with VLT NACO. For the putative planetary mass secondary, we find J = 20.0+/-0.2 mag. The HK spectra of both components imply low gravity, and a dusty atmosphere for the secondary. Comparisons to synthetic spectra yield Teff_A ~ 2550+/-150K, and Teff_B ~ 1600+/-100K, consistent with their late-M and mid-to-late L types. For these Teff, and an age of 5-10 Myrs, evolutionary models imply M_A ~ 24+/-6 M_Jup and M_B ~ 8+/-2 M_Jup. Independent comparisons of these models to the observed colors, spanning ~I to L', also yield the same masses and temperatures. Our primary mass agrees with other recent analyses; however, our secondary mass, while still in the planetary regime, is 2-3 times larger than claimed previously. This discrepancy can be traced to the luminosities: while the absolute photometry and Mbol of the primary agree with theoretical predictions, the secondary is ~ 2.5+/-0.5 mag fainter than expected in all bands from I to L' and in Mbol. This accounts for the much lower secondary mass (and temperature) derived earlier. We argue that this effect is highly unlikely to result from a variety of model-related problems, and is instead real. This conclusion is bolstered by the absence of any luminosity problems in either the primary, or in AB Pic B which we also analyse. We therefore suggest grey extinction in 2M1207B, due to occlusion by an edge-on circum-secondary disk. This is consistent with the observed properties of edge-on disks around T Tauri stars, and with the known presence of a high-inclination evolved disk around the primary. Finally, the system's implied mass ratio of ~0.3 suggests a binary-like formation scenario. (abridged)Comment: Accepted by The Astrophysical Journal, 43 pages text + 16 figs + 1 tabl

    The Next Generation Virgo cluster Survey. V. modelling the dynamics of M87 with the Made-to-Measure method

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    We study the dynamics of the giant elliptical galaxy M87 from the central to the outermost regions with the made-to-measure (M2M) method. We use a new catalogue of 922 globular cluster line-of- sight velocities extending to a projected radius of 180 kpc (equivalent to 25 M87 effective radii), and SAURON integral field unit data within the central 2.4 kpc. 263 globular clusters, mainly located beyond 40 kpc, are newly observed by the Next Generation Virgo Survey (NGVS). For the M2M modelling, the gravitational potential is taken as a combination of a luminous matter potential with a constant stellar mass-to-light ratio and a dark matter potential modelled as a logarithmic potential. Our best dynamical model returns a stellar mass-to-light ratio in the I band of M/LI = 6.0(+ -0.3) M_sun/L_sun with a dark matter potential scale velocity of 591(+ -50) km/s and scale radius of 42(+ -10) kpc. We determine the total mass of M87 within 180 kpc to be (1.5 + - 0.2) 10^13 M_sun. The mass within 40 kpc is smaller than previous estimates determined using globular cluster kinematics that did not extend beyond 45 kpc. With our new globular cluster velocities at much larger radii, we see that globular clusters around 40 kpc show an anomalously large velocity dispersion which affected previous results. The mass we derived is in good agreement with that inferred from ROSAT X-ray observation out to 180 kpc. Within 30 kpc our mass is also consistent with that inferred from Chandra and XMM-Newton X-ray observations, while within 120 kpc it is about 20% smaller. The model velocity dispersion anisotropy beta parameter for the globular clusters in M87 is small, varying from -0.2 at the centre to 0.2 at 40 kpc, and gradually decreasing to zero at 120 kpc.Comment: 20 pages, 16 figures, Accepted by Ap

    The Next Generation Virgo Cluster Survey. VI. The Kinematics of Ultra-compact Dwarfs and Globular Clusters in M87

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    The origin of ultra-compact dwarfs (UCDs)--objects larger and more massive than typical globular clusters (GCs), but more compact than typical dwarf galaxies--has been hotly debated in the 15 years since their discovery. Even whether UCDs should be considered galactic in origin, or simply the most extreme GCs, is not yet settled. We present the dynamical properties of 97 spectroscopically confirmed UCDs (rh >~10 pc) and 911 GCs associated with central cD galaxy of the Virgo cluster, M87. Our UCDs, of which 89% have M_star > ~2X10^6 M_sun and 92% are as blue as the classic blue GCs, nearly triple the sample of previous confirmed Virgo UCDs, providing by far the best opportunity for studying the global dynamics of a UCD system. We found that (1) UCDs have a surface number density profile that is shallower than that of the blue GCs in the inner ~ 70 kpc and as steep as that of the red GCs at larger radii; (2) UCDs exhibit a significantly stronger rotation than the GCs, and the blue GCs seem to have a velocity field that is more consistent with that of the surrounding dwarf ellipticals than with that of UCDs; (3) UCDs have a radially increasing orbital anisotropy profile, and are tangentially-biased at radii < ~ 40 kpc and radially-biased further out. In contrast, the blue GCs become more tangentially-biased at larger radii beyond ~ 40 kpc; (4) GCs with M_star > 2X10^6 M_sun have rotational properties indistinguishable from the less massive ones, suggesting that it is the size, instead of mass, that differentiates UCDs from GCs as kinematically distinct populations. We conclude that most UCDs in M87 are not consistent with being merely the most luminous and extended examples of otherwise normal GCs. The radially-biased orbital structure of UCDs at large radii is in general agreement with the "tidally threshed dwarf galaxy" scenario.Comment: 27 pages, 21 figures. To appear in The Astrophysical Journa

    The Next Generation Virgo Cluster Survey. X. Properties of Ultra-Compact Dwarfs in the M87, M49 and M60 Regions

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    We use imaging from the Next Generation Virgo cluster Survey (NGVS) to present a comparative study of ultra-compact dwarf (UCD) galaxies associated with three prominent Virgo sub-clusters: those centered on the massive, red-sequence galaxies M87, M49 and M60. We show how UCDs can be selected with high completeness using a combination of half-light radius and location in color-color diagrams (uiKsu^*iK_s or ugzu^*gz). Although the central galaxies in each of these sub-clusters have nearly identical luminosities and stellar masses, we find large differences in the sizes of their UCD populations, with M87 containing ~3.5 and 7.8 times more UCDs than M49 and M60, respectively. The relative abundance of UCDs in the three regions scales in proportion to sub-cluster mass, as traced by X-ray gas mass, total gravitating mass, number of globular clusters, and number of nearby galaxies. We find that the UCDs are predominantly blue in color, with ~85% of the UCDs having colors similar to blue GCs and stellar nuclei of dwarf galaxies. We present evidence that UCDs surrounding M87 and M49 may follow a morphological sequence ordered by the prominence of their outer, low surface brightness envelope, ultimately merging with the sequence of nucleated low-mass galaxies, and that envelope prominence correlates with distance from either galaxy. Our analysis provides evidence that tidal stripping of nucleated galaxies is an important process in the formation of UCDs.Comment: 37 pages, 40 figures. To appear in The Astrophysical Journa

    A Roadmap for HEP Software and Computing R&D for the 2020s

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    Particle physics has an ambitious and broad experimental programme for the coming decades. This programme requires large investments in detector hardware, either to build new facilities and experiments, or to upgrade existing ones. Similarly, it requires commensurate investment in the R&D of software to acquire, manage, process, and analyse the shear amounts of data to be recorded. In planning for the HL-LHC in particular, it is critical that all of the collaborating stakeholders agree on the software goals and priorities, and that the efforts complement each other. In this spirit, this white paper describes the R&D activities required to prepare for this software upgrade.Peer reviewe

    Etude de la production inclusive de pi0 de grandes impulsions transverses aupres du collisionneur pp du CERN

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    CNRS T 58461 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

    Measurement of the ratio of the W and Z cross sections with exactly one associated jet in pp collisions at s=7 TeV with ATLAS

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    Dans cette thèse la mesure du rapport des sections efficaces de production de bosons W et Z en association avec un jet au LHC est effectuée.Le rapport des sections efficaces est mesuré à l'aide des données issues de collisions proton-proton au LHC à une énergie dans le centre de masse de 7 TeV, recueillies par l'expérience ATLAS en 2010, correspondant à une luminosité intégrée d'environ 40 pb-1. L'analyse est effectuée à l aide de bosons W et Z se désintégrant dans le canal muon.Il s'agit de la première mesure du rapport des taux de production de bosons W et Z associés à un jet réalisée à une si haute énergie dans le centre de masse, la mesure est la également la première effectuée au LHC. Cette mesure constitue un test très important des calculs théoriques perturbatifs et tire avantage des annulations partielles ou totales de diverses incertitudes expérimentales.La mesure sert aussi pour les recherches de nouveaux phénomènes de physique au LHC à contraindre les bruits de fonds ayant les mêmes signatures topologiques.La valeur du rapport de mesuré est présentée en fonction de différents seuils d impulsion transverse de jet cumulatifs et est trouvé, a l intérieur de la précision statistique, en bon accord avec prédictions pertubatives de QCD aux LO et NLO.In this thesis an investigation of the ratio of the production cross section of W and Z bosons in association with one jet at LHC is performed.The cross-section ratio is measured with LHC proton-proton collision data at a center-of-mass energy of 7 TeV, collected by the ATLAS experiment in 2010, corresponding to an integrated luminosity of approximately 40 pb-1. The analysis is performed selecting W and Z bosons decaying in the muon channel.It is the first time the ratio of W and Z bosons production associated with one jet is measured at such a high center-of-mass energy, the measurement is the first one at the LHC. This measurement constitutes a very important test of perturbative theoretical calculations based on the advantage of the partial and full cancellations of various uncertainties.It also serves as constraining backgrounds with similar topological signatures in the search for new physics phenomena at the LHC. The measured ratio value is presented as a function of cumulative jet transverse momentum thresholds and found, within statistical precision, to agree well with perturbative LO and NLO QCD predictions.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF
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