Mostrando recursos 1 - 20 de 3.326

  1. L'astronomie dans le monde - 06/2016

    Manfroid, Jean
    Chocs d’amas - Amas de galaxies - Halos sur Pluton - Makémaké - Comète sans queue – Titan – Planètes Kepler - Transit de Mercure - Quatre lasers au-dessus de Paranal – NGC 1332 - Eau sur Mars

  2. HerMES: Halo Occupation Number and Bias Properties of Dusty Galaxies from Angular Clustering Measurements

    Cooray, Asantha; Amblard, A.; Wang, L.; Altieri, B.; Arumugam, V.; Auld, R.; Aussel, H.; Babbedge, T.; Blain, A.; Bock, J.; Boselli, A.; Buat, V.; Burgarella, D.; Castro-Rodriguez, N.; Cava, A.; Chanial, P.; Clements, D. L.; Conley, A.; Conversi, L.; Dowell, C. D.; Dwek, E.; Eales, S.; Elbaz, D.; Farrah, D.; Fox, M.; Franceschini, A.; Gear, W.; Glenn, J.; Griffin, M.; Halpern, M.; Hatziminaoglou, E.; Ibar, E.; Isaak, K.; Ivison, R. J.; Khostovan, A. A.; Lagache, G.; Levenson, L.; Lu, N.; Madden, S.; Maffei, B.; Mainetti, G.; Marchetti, L.; Marsden, G.; Mitchell-Wynne, K.; Mortier, A. M. J.; Nguyen, H. T.; O'Halloran, B.; Oliver, S. J.; Omont, A.; Page, M. J.; Panuzzo, P.; Papageorgiou, A.; Pearson, C. P.; Pérez-Fournon, I.; Pohlen, M.; Rawlings, J. I.; Raymond, G.; Rigopoulou, D.; Rizzo, D.; Roseboom, I. G.; Rowan-Robinson, M.; Portal, M. Sanchez; Schulz, B.; Scott, Douglas; Serra, P.; Seymour, N.; Shupe, D. L.; Smith, A. J.; Stevens, J. A.; Symeonidis, M.; Trichas, M.; Tugwell, K. E.; Vaccari, M.; Valtchanov, I.; Vieira, J. D.; Vigroux, L.; Ward, R.; Wright, G.; Xu, C. K.; Zemcov, M.
    5 pages; accepted for publication in A&A Special Issue on Herschel First Science Results (July 2010). HerMES information available at http://hermes.sussex.ac.uk/

  3. Evidence for Dynamically Driven Formation of the GW170817 Neutron Star Binary in NGC 4993

    Palmese, A.; Eifler, T. F.
    We present a study of NGC 4993, the host galaxy of the GW170817 gravitational-wave event, the GRB 170817A short gamma-ray burst (sGRB), and the AT 2017gfo kilonova. We use Dark Energy Camera imaging, AAT spectra, and publicly available data, relating our findings to binary neutron star (BNS) formation scenarios and merger delay timescales. NGC 4993 is a nearby early-type galaxy, with an i-band Sérsic index n = 4.0 and low asymmetry (A = 0.04 ± 0.01). These properties are unusual for sGRB hosts. However, NGC 4993 presents shell-like structures and dust lanes indicative of a recent galaxy merger, with the...

  4. How to distinguish starbursts and quiescently star-forming galaxies: the ‘bimodal’ submillimetre galaxy population as a case study

    Hayward, Christopher C.; Jonsson, Patrik; Kere?, Du?an; Magnelli, Benjamin; Hernquist, Lars Eric; Cox, T. J.
    In recent work, we have suggested that the high-redshift (z∼ 2–4) bright submillimetre galaxy (SMG) population is heterogeneous, with major mergers contributing both at early stages, where quiescently star-forming discs are blended into one submm source (‘galaxy-pair SMGs’), and at late stages, where mutual tidal torques drive gas inflows and cause strong starbursts. Here we combine hydrodynamic simulations of major mergers with 3D dust radiative transfer calculations to determine observational diagnostics that can distinguish between quiescently star-forming SMGs and starburst SMGs via integrated data alone. We fit the far-infrared (FIR) spectral energy distributions of the simulated galaxies with the optically...

  5. Modeling Mid-Infrared Diagnostics of Obscured Quasars and Starbursts

    Snyder, Gregory; Hayward, Christopher C.; Sajina, Anna; Jonsson, Patrik; Cox, Thomas J.; Hernquist, Lars Eric; Hopkins, Philip F.; Yan, Lin
    We analyze the link between active galactic nuclei (AGNs) and mid-infrared flux using dust radiative transfer calculations of starbursts realized in hydrodynamical simulations. Focusing on the effects of galaxy dust, we evaluate diagnostics commonly used to disentangle AGN and star formation in ultraluminous infrared galaxies (ULIRGs). We examine these quantities as a function of time, viewing angle, dust model, AGN spectrum, and AGN strength in merger simulations representing two possible extremes of the ULIRG population: one is a typical gas-rich merger at z ~ 0, and the other is characteristic of extremely obscured starbursts at z ~ 2-4. This highly...

  6. Submillimetre galaxies in a hierarchical universe: number counts, redshift distribution and implications for the IMF

    Hayward, C. C.; Narayanan, D.; Keres, D.; Jonsson, P.; Hopkins, P. F.; Cox, T. J.; Hernquist, Lars Eric
    High-redshift submillimetre galaxies (SMGs) are some of the most rapidly star-forming galaxies in the Universe. Historically, galaxy formation models have had difficulty explaining the observed number counts of SMGs. We combine a semi-empirical model with 3D hydrodynamical simulations and 3D dust radiative transfer to predict the number counts of unlensed SMGs. Because the stellar mass functions, gas and dust masses, and sizes of our galaxies are constrained to match observations, we can isolate uncertainties related to the dynamical evolution of galaxy mergers and the dust radiative transfer. The number counts and redshift distributions predicted by our model agree well with...

  7. Simulated Galaxy Interactions as Probes of Merger Spectral Energy Distributions

    Lanz, Lauranne; Hayward, Christopher C.; Zezas, Andreas; Smith, Howard A.; Ashby, Matthew L N; Brassington, Nicola; Fazio, Giovanni Gene; Hernquist, Lars Eric
    We present the first systematic comparison of ultraviolet-millimeter spectral energy distributions (SEDs) of observed and simulated interacting galaxies. Our sample is drawn from the Spitzer Interacting Galaxy Survey and probes a range of galaxy interaction parameters. We use 31 galaxies in 14 systems which have been observed with Herschel, Spitzer, GALEX, and 2MASS. We create a suite of GADGET-3 hydrodynamic simulations of isolated and interacting galaxies with stellar masses comparable to those in our sample of interacting galaxies. Photometry for the simulated systems is then calculated with the SUNRISE radiative transfer code for comparison with the observed systems. For most...

  8. The total infrared luminosity may significantly overestimate the star formation rate of quenching and recently quenched galaxies

    Hayward, C. C.; Lanz, L.; Ashby, Matthew L N; Fazio, Giovanni Gene; Hernquist, Lars Eric; Martinez-Galarza, J. R.; Noeske, K.; Smith, Howard A.; Wuyts, S.; Zezas, Andreas
    The total infrared (IR) luminosity is very useful for estimating the star formation rate (SFR) of galaxies, but converting the IR luminosity into an SFR relies on assumptions that do not hold for all galaxies. We test the effectiveness of the IR luminosity as an SFR indicator by applying it to synthetic spectral energy distributions generated from three-dimensional hydrodynamical simulations of isolated disc galaxies and galaxy mergers. In general, the SFR inferred from the IR luminosity agrees well with the true instantaneous SFR of the simulated galaxies. However, for the major mergers in which a strong starburst is induced, the...

  9. On the assembly of dwarf galaxies in clusters and their efficient formation of globular clusters

    Mistani, Pouria A.; Sales, Laura V.; Pillepich, Annalisa; Sanchez-Janssen, Rubén; Vogelsberger, Mark; Nelson, Dylan; Rodriguez-Gomez, Vicente; Torrey, Paul; Hernquist, Lars Eric
    Galaxy clusters contain a large population of low-mass dwarf elliptical galaxies whose exact origin is unclear: their colours, structural properties and kinematics differ substantially from those of dwarf irregulars in the field. We use the Illustris cosmological simulation to study differences in the assembly histories of dwarf galaxies (3 × 108 < M*/M⊙ < 1010) according to their environment. We find that cluster dwarfs achieve their maximum total and stellar mass on average ∼8 and ∼4.5 Gyr ago (or redshifts z = 1.0 and 0.4, respectively), around the time of infall into the clusters. In contrast, field dwarfs not subjected...

  10. Recoiling black holes: prospects for detection and implications of spin alignment

    Blecha, Laura; Sijacki, Debora; Kelley, Luke Zoltan; Torrey, Paul; Vogelsberger, Mark; Nelson, Dylan; Springel, Volker; Snyder, Gregory; Hernquist, Lars Eric
    Supermassive black hole (BH) mergers produce powerful gravitational wave emission. Asymmetry in this emission imparts a recoil kick to the merged BH, which can eject the BH from its host galaxy altogether. Recoiling BHs could be observed as offset active galactic nuclei (AGN). Several candidates have been identified, but systematic searches have been hampered by large uncertainties regarding their observability. By extracting merging BHs and host galaxy properties from the Illustris cosmological simulations, we have developed a comprehensive model for recoiling AGN. Here, for the first time, we model the effects of BH spin alignment and recoil dynamics based on...

  11. Modelling galactic conformity with the colour–halo age relation in the Illustris simulation

    Bray, Aaron; Pillepich, Annalisa; Sales, Laura V.; Zhu, Emily Chengxi; Genel, Shy; Rodriguez-Gomez, Vicente; Torrey, Paul; Nelson, Dylan; Vogelsberger, Mark; Springel, Volker; Eisenstein, Daniel James; Hernquist, Lars Eric
    Comparisons between observational surveys and galaxy formation models find that dark matter haloes’ mass can largely explain their galaxies’ stellar mass. However, it remains uncertain whether additional environmental variables, known as assembly bias, are necessary to explain other galaxy properties. We use the Illustris simulation to investigate the role of assembly bias in producing galactic conformity by considering 18 000 galaxies with Mstellar > 2 × 109 M⊙. We find a significant signal of galactic conformity: out to distances of about 10 Mpc, the mean red fraction of galaxies around redder galaxies is higher than around bluer galaxies at fixed stellar...

  12. Galactic Angular Momentum in the Illustris Simulation: Feedback and the Hubble Sequence

    Genel, Shy; Fall, S. Michael; Hernquist, Lars Eric; Vogelsberger, Mark; Snyder, Gregory F.; Rodriguez-Gomez, Vicente; Sijacki, Debora; Springel, Volker
    We study the stellar angular momentum of thousands of galaxies in the Illustris cosmological simulation, which captures gravitational and gas dynamics within galaxies, as well as feedback from stars and black holes. We find that the angular momentum of the simulated galaxies matches observations well, and in particular two distinct relations are found for late-type versus early-type galaxies. The relation for late-type galaxies corresponds to the value expected from full conservation of the specific angular momentum generated by cosmological tidal torques. The relation for early-type galaxies corresponds to retention of only ~30% of that, but we find that those early-type...

  13. Mapping galaxy encounters in numerical simulations: the spatial extent of induced star formation

    Moreno, J.; Torrey, P; Ellison, S. L.; Patton, D. R.; Bluck, A. F. L.; Bansal, G.; Hernquist, Lars Eric
    We employ a suite of 75 simulations of galaxies in idealized major mergers (stellar mass ratio ∼2.5:1), with a wide range of orbital parameters, to investigate the spatial extent of interaction-induced star formation. Although the total star formation in galaxy encounters is generally elevated relative to isolated galaxies, we find that this elevation is a combination of intense enhancements within the central kpc and moderately suppressed activity at larger galactocentric radii. The radial dependence of the star formation enhancement is stronger in the less massive galaxy than in the primary, and is also more pronounced in mergers of more closely...

  14. The colours of satellite galaxies in the Illustris simulation

    Sales, L. V.; Vogelsberger, M.; Genel, S.; Torrey, P; Nelson, D.; Rodriguez-Gomez, Vicente; Wang, W.; Pillepich, A.; Sijacki, D.; Springel, V.; Hernquist, Lars Eric
    Observationally, the fraction of blue satellite galaxies decreases steeply with host halo mass, and their radial distribution around central galaxies is significantly shallower in massive (M* ≥ 1011 M⊙) than in Milky Way-like systems. Theoretical models, based primarily on semi-analytical techniques, have had a long-standing problem with reproducing these trends, instead predicting too few blue satellites in general but also estimating a radial distribution that is too shallow, regardless of primary mass. In this Letter, we use the Illustris cosmological simulation to study the properties of satellite galaxies around isolated primaries. For the first time, we find good agreement between theory...

  15. Interstellar medium conditions in z ~ 0.2 Lyman-break analogs

    Contursi, A.; Baker, A. J.; Berta, S.; Magnelli, B.; Lutz, D.; Fischer, J.; Verma, A.; Nielbock, M.; Carpio, J. Grácia; Veilleux, S.; Sturm, E.; Davies, R.; Genzel, R.; Hailey-Dunsheath, S.; Herrera-Camus, R.; Janssen, A.; Poglitsch, A.; Sternberg, A.; Tacconi, L. J.
    We present an analysis of far–infrared (FIR) [CII] and [OI] fine structure line and continuum observations obtained with Herschel/PACS, and ^(12)CO(1–0) observations obtained with the IRAM Plateau de Bure Interferometer, of Lyman-break analogs (LBAs) at z ~ 0.2. The principal aim of this work is to determine the typical interstellar medium (ISM) properties of z ~ 1−2 main sequence (MS) galaxies, with stellar masses between 10^(9.5) and 10^(11)M⊙, which are currently not easily detectable in all these lines even with ALMA and NOEMA. We perform PDR modeling and apply different infared diagnostics to derive the main physical parameters of the...

  16. Interstellar medium conditions in z ~ 0.2 Lyman-break analogs

    Contursi, A.; Baker, A. J.; Berta, S.; Magnelli, B.; Lutz, D.; Fischer, J.; Verma, A.; Nielbock, M.; Grácia Carpio, J.; Veilleux, S.; Sturm, E.; Davies, R.; Genzel, R.; Hailey-Dunsheath, S.; Herrera-Camus, R.; Janssen, A.; Poglitsch, A.; Sternberg, A.; Tacconi, L. J.
    We present an analysis of far–infrared (FIR) [CII] and [OI] fine structure line and continuum observations obtained with Herschel/PACS, and ^(12)CO(1–0) observations obtained with the IRAM Plateau de Bure Interferometer, of Lyman-break analogs (LBAs) at z ~ 0.2. The principal aim of this work is to determine the typical interstellar medium (ISM) properties of z ~ 1−2 main sequence (MS) galaxies, with stellar masses between 10^(9.5) and 10^(11)M⊙, which are currently not easily detectable in all these lines even with ALMA and NOEMA. We perform PDR modeling and apply different infared diagnostics to derive the main physical parameters of the...

  17. HI content and other structural properties of galaxies in the Virgo cluster from the Arecibo Legacy Fast ALFA Survey

    Gavazzi, Giuseppe; Giovanelli, Riccardo; Haynes, Martha P.; Fabello, Silvia; Fumagalli, Michele; Kent, Brian R.; Koopmann, Rebecca A.; Brosch, Noah; Hoffman, G. Lyle; Salzer, John J.; Boselli, Alessandro
    10 pages, 10 Postscript figures, accepted for publication in Astronomy and Astrophysics (25/01/2008) - Replaced to fit A&A vers. 6.1

  18. Rotation Curves and Dark Matter

    Lipovka, Anton,
    In present paper we argue that to explain the shape of the Rotation Curves (RC) of galaxies, there is no need to involve the concept of dark matter. Rotation curves are completely determined by the distribution of baryon matter and gas kinetics. Such parameters of the galaxy as barion mass and its distribution can be easily calculated from the observed RC. We show the extended parts of RCs to be just a wind tails, formed by gas of the outer disks in assumption that it obeys the laws of gas kinetics. As examples, the Galaxy, NGC7331 and NGC3198 are considered....

  19. Submillimetre galaxies reside in dark matter haloes with masses greater than 3 × 10 11 solar masses

    Amblard, Alexandre; Cooray, Asantha; Serra, Paolo; Altieri, B.; Arumugam, V.; Aussel, H.; Blain, A.; Bock, J.; Boselli, A.; Buat, V.; Castro-Rodríguez, N.; Cava, A.; Chanial, P.; Chapin, E.; L. Clements, D.; Conley, A.; Conversi, L.; D. Dowell, C.; Dwek, E.; Eales, S.; Elbaz, D.; Farrah, D.; Franceschini, A.; Gear, W.; Glenn, J.; Griffin, M.; Halpern, M.; Hatziminaoglou, E.; Ibar, E.; Isaak, K.; J. Ivison, R.; A. Khostovan, A.; Lagache, G.; Levenson, L.; Lu, N.; Madden, S.; Maffei, B.; Mainetti, G.; Marchetti, L.; Marsden, G.; Mitchell-Wynne, K.; T. Nguyen, H.; O'Halloran, B.; J. Oliver, S.; Omont, A.; J. Page, M.; Panuzzo, P.; Papageorgiou, A.; P. Pearson, C.; Pérez-Fournon, I.; Pohlen, M.; Rangwala, N.; G. Roseboom, I.; Rowan-Robinson, M.; Sánchez Portal, M.; Schulz, B.; Scott, Douglas; Seymour, N.; L. Shupe, D.; J. Smith, A.; A. Stevens, J.; Symeonidis, M.; Trichas, M.; Tugwell, K.; Vaccari, M.; Valiante, E.; Valtchanov, I.; D. Vieira, J.; Vigroux, L.; Wang, L.; Ward, R.; Wright, G.; K. Xu, C.; Zemcov, M.
    International audience

  20. La galaxie "Ecole de la rénovation urbaine" et son offre de formation

    Carriou, Claire; Fijalkow, Yankel
    International audience

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