Astrophysics of Galaxies Publications (50)

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Astrophysics of Galaxies Publications

Observations of star-forming galaxies in the distant Universe (z > 2) are starting to confirm the importance of massive stars in shaping galaxy emission and evolution. Inevitably, these distant stellar populations are unresolved, and the limited data available must be interpreted in the context of stellar population synthesis models. With the imminent launch of JWST and the prospect of spectral observations of galaxies within a gigayear of the Big Bang, the uncertainties in modelling of massive stars are becoming increasingly important to our interpretation of the high redshift Universe. Read More


The escape mechanism of orbits in a star cluster rotating around its parent galaxy in a circular orbit is investigated. A three degrees of freedom model is used for describing the dynamical properties of the Hamiltonian system. The gravitational field of the star cluster is represented by a smooth and spherically symmetric Plummer potential. Read More


We report on the detection at $>$98% confidence of an optical counterpart to AGC 249525, an Ultra-Compact High Velocity Cloud (UCHVC) discovered by the ALFALFA blind neutral hydrogen survey. UCHVCs are compact, isolated HI clouds with properties consistent with their being nearby low-mass galaxies, but without identified counterparts in extant optical surveys. Analysis of the resolved stellar sources in deep $g$- and $i$-band imaging from the WIYN pODI camera reveals a clustering of possible Red Giant Branch stars associated with AGC 249525 at a distance of 1. Read More


We compute the star formation rate (SFR) in molecular clouds (MCs) that originate {\it ab initio} in a new, higher-resolution simulation of supernova-driven turbulence. Because of the large number of well-resolved clouds with self-consistent boundary and initial conditions, we obtain a large range of cloud physical parameters with realistic statistical distributions, an unprecedented sample of star-forming regions to test SFR models and to interpret observational surveys. We confirm the dependence of the SFR per free-fall time, $SFR_{\rm ff}$, on the virial parameter, $\alpha_{\rm vir}$, found in previous simulations, and compare a revised version of our turbulent fragmentation model with the numerical results. Read More


Here we present the evidence for periodicity of an optical emission detected in several AGN. Significant periodicity is found in light curves and radial velocity curves. We discuss possible mechanisms that could produce such periodic variability and their implications. Read More


This is a written version of the closing talk at the 22nd Los Alamos Stellar pulsation conference on wide field variability surveys. It comments on some of the issues which arise from the meeting. These include the need for attention to photometric standardization (especially in the infrared) and the somewhat controversial problem of statistical bias in the use of parallaxes (and other methods of distance determination). Read More


We present a chemical abundance analysis of a metal-poor star, ROA 276, in the stellar system omega Centauri. We confirm that this star has an unusually high [Sr/Ba] abundance ratio. Additionally, ROA 276 exhibits remarkably high abundance ratios, [X/Fe], for all elements from Cu to Mo along with normal abundance ratios for the elements from Ba to Pb. Read More


Ten weeks' daily imaging of the giant elliptical galaxy M87 with the Hubble Space Telescope has yielded 41 nova light curves of unprecedented quality for extragalactic cataclysmic variables. We have recently used these light curves to demonstrate that the observational scatter in the so-called Maximum-Magnitude Rate of Decline (MMRD) relation for classical novae is so large as to render the nova-MMRD useless as a standard candle. Here we demonstrate that the Buscombe - de Vaucouleurs hypothesis, that all novae converge to nearly the same absolute magnitude about two weeks after maximum light, is strongly supported by our M87 nova data. Read More


We present a detailed analysis of the white dwarf luminosity functions derived from the local 40 pc sample and the deep proper motion catalog of Munn et al (2014, 2017). Many of the previous studies ignored the contribution of thick disk white dwarfs to the Galactic disk luminosity function, which results in an erronous age measurement. We demonstrate that the ratio of thick/thin disk white dwarfs is roughly 20\% in the local sample. Read More


Ultra-high-energy cosmic rays (UHECRs) can be accelerated by tidal disruption events of stars by black holes. Encounters between white dwarfs with intermediate-mass black holes (IMBHs) provide a natural environment for acceleration, as tidal forces can ignite nuclear burn and lead to a supernova explosion. The numbers of IMBHs may be substantially augmented once account is taken of their likely presence in dwarf galaxies. Read More


We present K-band Multi-Object Spectrograph (KMOS) observations of 18 Red Supergiant (RSG) stars in the Sculptor Group galaxy NGC 55. Radial velocities are calculated and are shown to be in good agreement with previous estimates, confirming the supergiant nature of the targets and providing the first spectroscopically confirmed RSGs in NGC 55. Stellar parameters are estimated for 14 targets using the $J$-band analysis technique, making use of state-of-the-art stellar model atmospheres. Read More


We present three-dimensional hydrodynamical simulations showing the effect of kinetic and radiative AGN feedback on a model galaxy representing a massive quiescent low-redshift early-type galaxy of $M_* = 8.41\times 10^{10} M_\odot$, harbouring a $M_\mathrm{BH} = 4\times 10^8 M_\odot $ black hole surrounded by a cooling gaseous halo. We show that, for a total baryon fraction of $\sim 20\%$ of the cosmological value, feedback from the AGN can keep the galaxy quiescent for about 4. Read More


Massive black-hole binaries, formed when galaxies merge, are among the primary sources of gravitational waves targeted by ongoing Pulsar Timing Array (PTA) experiments and the upcoming space-based LISA interferometer. However, their formation and merger rates are still highly uncertain. Recent upper limits on the stochastic gravitational-wave background obtained by PTAs are starting being in marginal tension with theoretical models for the pairing and orbital evolution of these systems. Read More


(Abridged) Our sensitive ($\sigma_{\rm n} = 572\,{\rm nJy\,beam}^{-1}$), high-resolution (FWHM $\theta_{1/2} = 220\,{\rm mas} \approx2\mathrm{\,kpc~at~}z\gtrsim1$) 10$\,$GHz image covering a single Karl G.~Jansky Very Large Array (VLA) primary beam (FWHM $\Theta_{1/2} = 4.25'$) in the GOODS-N field contains 32 sources with $S_{\rm p}\gtrsim2\,\mu{\rm Jy~beam}^{-1}$ and optical and/or near-infrared (OIR) counterparts. Read More


2017Feb
Affiliations: 1CRAL, 2CRAL, 3CRAL, 4CRAL, 5AIP, 6CRAL, 7IRAP, 8CRAL, 9IRAP, 10Leiden, 11Leiden, 12CRAL, 13ETH, 14CRAL, 15CRAL, 16AIP

We present an analysis of MUSE observations obtained on the massive Frontier Fields cluster Abell 2744. This new dataset covers the entire multiply-imaged region around the cluster core. We measure spectroscopic redshifts for HST-selected continuum sources together with line emitters blindly detected in the datacube. Read More


We present a library of empirical stellar spectra created using spectra from the Sloan Digital Sky Survey's Baryon Oscillation Spectroscopic Survey (BOSS). The templates cover spectral types O5 through L3, are binned by metallicity from -2.0 dex through +1. Read More


2017Feb
Affiliations: 1University of New Hampshire, 2IRAP, France, 3Peking University, China, 4IRAP, France, 5IRAP, France, 6University of Alabama

The X-ray source 2XMM J123103.2+110648 was previously found to show pure thermal X-ray spectra and a ~3.8 hr periodicity in three XMM-Newton X-ray observations in 2003-2005, and the optical spectrum of the host galaxy suggested it as a type 2 active galactic nucleus candidate. Read More


2017Feb
Authors: MAGIC Collaboration, M. L. Ahnen1, S. Ansoldi2, L. A. Antonelli3, P. Antoranz4, C. Arcaro5, A. Babic6, B. Banerjee7, P. Bangale8, U. Barres de Almeida9, J. A. Barrio10, W. Bednarek11, E. Bernardini12, A. Berti13, B. Biasuzzi14, A. Biland15, O. Blanch16, S. Bonnefoy17, G. Bonnoli18, F. Borracci19, T. Bretz20, S. Buson21, A. Carosi22, A. Chatterjee23, R. Clavero24, P. Colin25, E. Colombo26, J. L. Contreras27, J. Cortina28, S. Covino29, P. Da Vela30, F. Dazzi31, A. De Angelis32, B. De Lotto33, E. de Oña Wilhelmi34, F. Di Pierro35, M. Doert36, A. Domínguez37, D. Dominis Prester38, D. Dorner39, M. Doro40, S. Einecke41, D. Eisenacher Glawion42, D. Elsaesser43, M. Engelkemeier44, V. Fallah Ramazani45, A. Fernández-Barral46, D. Fidalgo47, M. V. Fonseca48, L. Font49, K. Frantzen50, C. Fruck51, D. Galindo52, R. J. García López53, M. Garczarczyk54, D. Garrido Terrats55, M. Gaug56, P. Giammaria57, N. Godinović58, D. Gora59, D. Guberman60, D. Hadasch61, A. Hahn62, M. Hayashida63, J. Herrera64, J. Hose65, D. Hrupec66, G. Hughes67, W. Idec68, K. Kodani69, Y. Konno70, H. Kubo71, J. Kushida72, A. La Barbera73, D. Lelas74, E. Lindfors75, S. Lombardi76, F. Longo77, M. López78, R. López-Coto79, P. Majumdar80, M. Makariev81, K. Mallot82, G. Maneva83, M. Manganaro84, N. Mankuzhiyil85, K. Mannheim86, L. Maraschi87, B. Marcote88, M. Mariotti89, M. Martínez90, D. Mazin91, U. Menzel92, J. M. Miranda93, R. Mirzoyan94, A. Moralejo95, E. Moretti96, D. Nakajima97, V. Neustroev98, A. Niedzwiecki99, M. Nievas Rosillo100, K. Nilsson101, K. Nishijima102, K. Noda103, L. Nogués104, S. Paiano105, J. Palacio106, M. Palatiello107, D. Paneque108, R. Paoletti109, J. M. Paredes110, X. Paredes-Fortuny111, G. Pedaletti112, M. Peresano113, L. Perri114, M. Persic115, J. Poutanen116, P. G. Prada Moroni117, E. Prandini118, I. Puljak119, J. R. Garcia120, I. Reichardt121, W. Rhode122, M. Ribó123, J. Rico124, T. Saito125, K. Satalecka126, S. Schroeder127, T. Schweizer128, S. N. Shore129, A. Sillanpää130, J. Sitarek131, I. Snidaric132, D. Sobczynska133, A. Stamerra134, M. Strzys135, T. Surić136, L. Takalo137, H. Takami138, F. Tavecchio139, P. Temnikov140, T. Terzić141, D. Tescaro142, M. Teshima143, D. F. Torres144, T. Toyama145, A. Treves146, G. Vanzo147, V. Verguilov148, I. Vovk149, J. E. Ward150, M. Will151, M. H. Wu152, R. Zanin153, Fermi-LAT collaboration154, :155, J. Becerra González156, B. Rani157, F. Krauss158, M. Perri159, F. Verrecchia160, R. Reinthal161
Affiliations: 1ETH Zurich, 2Università di Udine, INFN Trieste, 3INAF National Institute for Astrophysics, 4Università di Siena, INFN Pisa, 5Università di Padova and INFN, 6Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka, University of Split and University of Zagreb, Croatia, 7Saha Institute of Nuclear Physics, 1/AF Bidhannagar, 8Max-Planck-Institut für Physik, 9Max-Planck-Institut für Physik, 10Universidad Complutense, 11University of Łódź, 12Deutsches Elektronen-Synchrotron, 13Università di Udine, INFN Trieste, 14Università di Udine, INFN Trieste, 15ETH Zurich, 16Institut de Fisica d'Altes Energies, 17Universidad Complutense, 18Università di Siena, INFN Pisa, 19Max-Planck-Institut für Physik, 20Universität Würzburg, 21Università di Padova and INFN, 22INAF National Institute for Astrophysics, 23Saha Institute of Nuclear Physics, 1/AF Bidhannagar, 24Inst. de Astrofísica de Canarias, Universidad de La Laguna, Dpto. Astrofísica, 25Max-Planck-Institut für Physik, 26Inst. de Astrofísica de Canarias, Universidad de La Laguna, Dpto. Astrofísica, 27Universidad Complutense, 28Institut de Fisica d'Altes Energies, 29INAF National Institute for Astrophysics, 30Università di Siena, INFN Pisa, 31Max-Planck-Institut für Physik, 32Università di Padova and INFN, 33Università di Udine, INFN Trieste, 34Institute for Space Sciences, 35INAF National Institute for Astrophysics, 36Technische Universität Dortmund, 37Universidad Complutense, 38Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka, University of Split and University of Zagreb, Croatia, 39Universität Würzburg, 40Università di Padova and INFN, 41Technische Universität Dortmund, 42Universität Würzburg, 43Technische Universität Dortmund, 44Technische Universität Dortmund, 45Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Astronomy Division, University of Oulu, Finland, 46Institut de Fisica d'Altes Energies, 47Universidad Complutense, 48Universidad Complutense, 49Unitat de Física de les Radiacions, Departament de Física, and CERES-IEEC, Universitat Autònoma de Barcelona, 50Technische Universität Dortmund, 51Max-Planck-Institut für Physik, 52Universitat de Barcelona, ICC, 53Inst. de Astrofísica de Canarias, Universidad de La Laguna, Dpto. Astrofísica, 54Deutsches Elektronen-Synchrotron, 55Unitat de Física de les Radiacions, Departament de Física, and CERES-IEEC, Universitat Autònoma de Barcelona, 56Unitat de Física de les Radiacions, Departament de Física, and CERES-IEEC, Universitat Autònoma de Barcelona, 57INAF National Institute for Astrophysics, 58Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka, University of Split and University of Zagreb, Croatia, 59Deutsches Elektronen-Synchrotron, 60Institut de Fisica d'Altes Energies, 61Japanese MAGIC Consortium, ICRR, The University of Tokyo, Department of Physics and Hakubi Center, Kyoto University, Tokai University, The University of Tokushima, 62Max-Planck-Institut für Physik, 63Japanese MAGIC Consortium, ICRR, The University of Tokyo, Department of Physics and Hakubi Center, Kyoto University, Tokai University, The University of Tokushima, 64Inst. de Astrofísica de Canarias, Universidad de La Laguna, Dpto. Astrofísica, 65Max-Planck-Institut für Physik, 66Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka, University of Split and University of Zagreb, Croatia, 67ETH Zurich, 68University of Łódź, 69Japanese MAGIC Consortium, ICRR, The University of Tokyo, Department of Physics and Hakubi Center, Kyoto University, Tokai University, The University of Tokushima, 70Japanese MAGIC Consortium, ICRR, The University of Tokyo, Department of Physics and Hakubi Center, Kyoto University, Tokai University, The University of Tokushima, 71Japanese MAGIC Consortium, ICRR, The University of Tokyo, Department of Physics and Hakubi Center, Kyoto University, Tokai University, The University of Tokushima, 72Japanese MAGIC Consortium, ICRR, The University of Tokyo, Department of Physics and Hakubi Center, Kyoto University, Tokai University, The University of Tokushima, 73INAF National Institute for Astrophysics, 74Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka, University of Split and University of Zagreb, Croatia, 75Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Astronomy Division, University of Oulu, Finland, 76INAF National Institute for Astrophysics, 77Università di Udine, INFN Trieste, 78Universidad Complutense, 79Institut de Fisica d'Altes Energies, 80Saha Institute of Nuclear Physics, 1/AF Bidhannagar, 81Inst. for Nucl. Research and Nucl. Energy, 82Deutsches Elektronen-Synchrotron, 83Inst. for Nucl. Research and Nucl. Energy, 84Inst. de Astrofísica de Canarias, Universidad de La Laguna, Dpto. Astrofísica, 85Università di Udine, INFN Trieste, 86Universität Würzburg, 87INAF National Institute for Astrophysics, 88Universitat de Barcelona, ICC, 89Università di Padova and INFN, 90Institut de Fisica d'Altes Energies, 91Max-Planck-Institut für Physik, 92Max-Planck-Institut für Physik, 93Università di Siena, INFN Pisa, 94Max-Planck-Institut für Physik, 95Institut de Fisica d'Altes Energies, 96Max-Planck-Institut für Physik, 97Japanese MAGIC Consortium, ICRR, The University of Tokyo, Department of Physics and Hakubi Center, Kyoto University, Tokai University, The University of Tokushima, 98Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Astronomy Division, University of Oulu, Finland, 99University of Łódź, 100Universidad Complutense, 101Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Astronomy Division, University of Oulu, Finland, 102Japanese MAGIC Consortium, ICRR, The University of Tokyo, Department of Physics and Hakubi Center, Kyoto University, Tokai University, The University of Tokushima, 103Max-Planck-Institut für Physik, 104Institut de Fisica d'Altes Energies, 105Università di Padova and INFN, 106Institut de Fisica d'Altes Energies, 107Università di Udine, INFN Trieste, 108Max-Planck-Institut für Physik, 109Università di Siena, INFN Pisa, 110Universitat de Barcelona, ICC, 111Universitat de Barcelona, ICC, 112Deutsches Elektronen-Synchrotron, 113Università di Udine, INFN Trieste, 114INAF National Institute for Astrophysics, 115Università di Udine, INFN Trieste, 116Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Astronomy Division, University of Oulu, Finland, 117Università di Pisa, and INFN Pisa, 118ETH Zurich, 119Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka, University of Split and University of Zagreb, Croatia, 120Max-Planck-Institut für Physik, 121Università di Padova and INFN, 122Technische Universität Dortmund, 123Universitat de Barcelona, ICC, 124Institut de Fisica d'Altes Energies, 125Japanese MAGIC Consortium, ICRR, The University of Tokyo, Department of Physics and Hakubi Center, Kyoto University, Tokai University, The University of Tokushima, 126Deutsches Elektronen-Synchrotron, 127Technische Universität Dortmund, 128Max-Planck-Institut für Physik, 129Università di Pisa, and INFN Pisa, 130Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Astronomy Division, University of Oulu, Finland, 131University of Łódź, 132Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka, University of Split and University of Zagreb, Croatia, 133University of Łódź, 134INAF National Institute for Astrophysics, 135Max-Planck-Institut für Physik, 136Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka, University of Split and University of Zagreb, Croatia, 137Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Astronomy Division, University of Oulu, Finland, 138Japanese MAGIC Consortium, ICRR, The University of Tokyo, Department of Physics and Hakubi Center, Kyoto University, Tokai University, The University of Tokushima, 139INAF National Institute for Astrophysics, 140Inst. for Nucl. Research and Nucl. Energy, 141Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka, University of Split and University of Zagreb, Croatia, 142Università di Padova and INFN, 143Max-Planck-Institut für Physik, 144ICREA and Institute for Space Sciences, 145Max-Planck-Institut für Physik, 146Università di Udine, INFN Trieste, 147Inst. de Astrofísica de Canarias, Universidad de La Laguna, Dpto. Astrofísica, 148Inst. for Nucl. Research and Nucl. Energy, 149Max-Planck-Institut für Physik, 150Institut de Fisica d'Altes Energies, 151Inst. de Astrofísica de Canarias, Universidad de La Laguna, Dpto. Astrofísica, 152Institute for Space Sciences, 153Universitat de Barcelona, ICC, 154Inst. de Astrofísica de Canarias, Universidad de La Laguna, Dpto. Astrofísica, 155Inst. de Astrofísica de Canarias, Universidad de La Laguna, Dpto. Astrofísica, 156Inst. de Astrofísica de Canarias, Universidad de La Laguna, Dpto. Astrofísica, 157NASA Goddard Space Flight Center, 158GRAPPA and Anton Pannekoek Institute for Astronomy, University of Amsterdam, 159INAF National Institute for Astrophysics, 160INAF National Institute for Astrophysics, 161Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Astronomy Division, University of Oulu, Finland

We present the first detection of the nearby (z=0.084) low-luminosity BL Lac object 1ES 1741+196 in the very high energy (VHE: E$>$100 GeV) band. This object lies in a triplet of interacting galaxies. Read More


2017Feb
Affiliations: 1Institut fuer Astro- und Teilchen-Physik, Universitaet Innsbruck, 2Institute for Astronomy, University of Hawaii

Blue supergiant stars of B and A spectral types are amongst the visually brightest non-transient astronomical objects. Their intrinsic brightness makes it possible to obtain high quality optical spectra of these objects in distant galaxies, enabling the study not only of these stars in different environments, but also to use them as tools to probe their host galaxies. Quantitative analysis of their optical spectra provide tight constraints on their evolution in a wide range of metallicities, as well as on the present-day chemical composition, extinction laws and distances to their host galaxies. Read More


We present gas kinematics based on the [OIII] $\lambda$5007 line and their connection to galaxy gravitational potential, active galactic nucleus (AGN) energetics, and star formation, using a large sample of ~110,000 AGNs and star-forming (SF) galaxies at z<0.3. Gas and stellar velocity dispersions are comparable to each other in SF galaxies, indicating that the ionized gas kinematics can be accounted by the gravitational potential of host galaxies. Read More


The formation of relativistic jets in active galactic nuclei (AGN) is related to accretion on to their central supermassive black holes, and magnetic fields are believed to play a central role in launching, collimating and accelerating the jet streams from very compact regions out to kiloparsec or megaparsec scales. In the presence of helical or toroidal magnetic fields threading the AGN jets and their immediate vicinity, gradients in the observed Faraday rotation measures are expected due to the systematic change in the line-of-sight component of the magnetic field across the jet. We have analysed total intensity, linear polarization, fractional polarization and Faraday rotation maps based on Very Long Baseline Array data obtained at four wavelengths in the 18-22 cm range for six AGN (OJ 287, 3C 279, PKS 1510-089, 3C 345, BL Lac and 3C 454. Read More


In extending our spectroscopic program, which targets sources drawn from the International Celestial Reference Frame (ICRF) Catalog, we have obtained spectra for about 160 compact flat-spectrum radio sources and determined redshifts for 112 quasars and radio galaxies. A further 14 sources with featureless spectra have been classified as BL Lac objects. Spectra were obtained at three telescopes: the 3. Read More


The W51 cloud complex is one of the best laboratories in our Galaxy to study high-mass star formation. At a distance of about 5 kpc, it is the closest region containing a high-mass protocluster, and it has two. The cloud includes a long infrared-dark cloud, is interacting with a supernova remnant, and contains a variety of unique massive protostellar sources. Read More


In the past years several authors studied the abundance of satellites around galaxies in order to better estimate the halo masses of host galaxies. To investigate this connection, we analyze galaxies with $M_\mathrm{star}\geq\,10^{10}\,M_{\odot}$ from the hydrodynamical cosmological simulation Magneticum. We find that the satellite fraction of centrals is independent of their morphology. Read More


We describe a method to identify inclined water maser disks orbiting massive black holes and to potentially use them to measure black hole masses. Due to the geometry of maser amplification pathways, the minority of water maser disks are observable: only those viewed nearly edge-on have been identified, suggesting that an order of magnitude additional maser disks exist. We suggest that inward-propagating masers will be gravitationally deflected by the central black hole, thereby scattering water maser emission out of the disk plane and enabling detection. Read More


The role of major mergers in galaxy evolution is investigated through a detailed characterization of the stellar populations, ionized gas properties, and star formation rates (SFR) in the early-stage merger LIRGs IC 1623 W and NGC 6090, by analysing optical Integral Field Spectroscopy (IFS) and high resolution HST imaging. The spectra were processed with the Starlight full spectral fitting code, and the emission lines measured in the residual spectra. The results are compared with control non-interacting spiral galaxies from the CALIFA survey. Read More


We propose a novel explanation for the Hercules stream consistent with recent measurements of the extent and pattern speed of the Galactic bar. We have adapted a made-to-measure dynamical model tailored for the Milky Way to investigate the kinematics of the Solar neighborhood. The model matches the 3D density of the Red Clump Giant stars (RCGs) in the bulge and bar as well as stellar kinematics in the inner Galaxy, with a pattern speed of $39$ km s$^{-1}$ kpc$^{-1}$. Read More


We present the HST WFC3/F275W UV imaging observations of A2218-Flanking, a lensed compact dwarf galaxy at redshift $z\approx2.5$. The stellar mass of A2218-Flanking is $\log(M/M_{\odot}=9. Read More


Accurate measurement of galaxy structures is a prerequisite for quantitative investigation of galaxy properties or evolution. Yet, the impact of galaxy inclination and dust on commonly used metrics of galaxy structure is poorly quantified. We use infrared data sets to select inclination-independent samples of disc and flattened elliptical galaxies. Read More


Context. Ultra-compact dwarfs (UCDs) are stellar systems displaying colours and metallicities between those of globular clusters (GCs) and early-type dwarf galaxies, as well as sizes of Reff <= 100 pc and luminosities in the range -13.5 < MV < -11 mag. Read More


The propagation of cosmic rays in turbulent magnetic fields is a diffusive process driven by the scattering of the charged particles by random magnetic fluctuations. Such fields are usually highly intermittent, consisting of intense magnetic filaments and ribbons surrounded by weaker, unstructured fluctuations. Studies of cosmic ray propagation have largely overlooked intermittency, instead relying on Gaussian random magnetic fields. Read More


Vibration-rotation lines of H$_{2}$ from highly excited levels approaching the dissociation limit have been detected at a number of locations in the shocked gas of the Orion Molecular Cloud (OMC-1), including in a Herbig-Haro object near the tip of one of the OMC-1 "fingers." Population diagrams show that while the excited H$_{2}$ is almost entirely at a kinetic temperature of $\sim$1,800 K, (typical for vibrationally shock-excited H$_{2}$), as in the previously reported case of Herbig-Haro object HH 7 up to a few percent of the H$_{2}$ is at a kinetic temperature of $\sim$5,000~K. The location with the largest fraction of hot H$_{2}$ is the Herbig-Haro object, where the outflowing material is moving at a higher speed than at the other locations. Read More


We investigate the far-infrared properties of galaxies selected via deep, narrow-band imaging of the H$\alpha$ emission line in four redshift slices from $z=0.40$--$2.23$ over $\sim 1$deg$^2$ as part of the High-redshift Emission Line Survey (HiZELS). Read More


We explore the correlations between velocity and metallicity and the possible distinct chemical signatures of the velocity over-densities of the local Galactic neighbourhood. We use the large spectroscopic survey RAVE and the Geneva Copenhagen Survey. We compare the metallicity distribution of regions in the velocity plane ($v_R,v_\phi$) with that of their symmetric counterparts ($-v_R,v_\phi$). Read More


We carried out the deep spectroscopic observations of the nearby cluster A2151 with AF2/WYFFOS@WHT. The caustic technique enables us to identify 360 members brighter than $M_r = -16$ and within 1.3$R_{200}$. Read More


A large fraction of active galactic nuclei (AGN) are "invisible" in extant optical surveys due to either distance or dust-obscuration. The existence of this large population of dust-obscured, infrared-bright AGN is predicted by models of galaxy - supermassive black hole coevolution and is required to explain the observed X-ray and infrared backgrounds. Recently, infrared colour-cuts with WISE have identified a portion of this missing population. Read More


2017Feb
Affiliations: 1Caltech, 2Davis, 3UCSD, 4Northwestern, 5Berkeley, 6Austin, 7CITA, 8Flatiron, 9Caltech, 10Caltech, 11Zurich, 12MIT, 13Caltech, 14Northwestern, 15Caltech, 16Caltech, 17Caltech, 18Caltech, 19Caltech, 20Caltech, 21Northwestern, 22Stanford, 23Austin, 24Irvine, 25Caltech, 26UCSD, 27Irvine, 28Florida

The Feedback In Realistic Environments (FIRE) project explores the role of feedback in cosmological simulations of galaxy formation. Previous FIRE simulations used an identical source code (FIRE-1) for consistency. Now, motivated by the development of more accurate numerics (hydrodynamic solvers, gravitational softening, supernova coupling) and the exploration of new physics (e. Read More


In two recent arXiv postings, Maji et al. argue against the existence of a spatially thin, kinematically coherent Disk of Satellites (DoS) around the Milky Way (MW), and suggest that the DoS is "maybe a misinterpretation of the data". These claims are in stark contrast to previous works, and indeed we show that the conclusions of Maji et al. Read More


We use adaptive-mesh magnetohydrodynamic simulations to study the effect of magnetic fields on ram pressure stripping of galaxies in the intracluster medium (ICM). Although the magnetic pressure in typical clusters is not strong enough to affect the gas mass loss rate from galaxies, magnetic fields can affect the morphology of stripped galaxies. ICM magnetic fields are draped around orbiting galaxies and aligned with their stripped tails. Read More


Star formation in our Galaxy occurs in molecular clouds that are self-gravitating, highly turbulent, and magnetized. We study the conditions under which cloud cores inherit large-scale magnetic field morphologies and how the field is governed by cloud turbulence. We present four moving-mesh simulations of supersonic, turbulent, isothermal, self-gravitating gas with a range of magnetic mean-field strengths characterized by the Alfv\'enic Mach number $\mathcal{M}_{{\rm A}, 0}$, resolving pre-stellar core formation from parsec to a few AU scales. Read More


Motivated by the stellar fossil record of Local Group (LG) dwarf galaxies, we show that the star-forming ancestors of the faintest ultra-faint dwarf galaxies (UFDs; ${\rm M}_{\rm V}$ $\sim -2$ or ${\rm M}_{\star}$ $\sim 10^{2}$ at $z=0$) had ultra-violet (UV) luminosities of ${\rm M}_{\rm UV}$ $\sim -3$ to $-6$ during reionization ($z\sim6-10$). The existence of such faint galaxies has substantial implications for early epochs of galaxy formation and reionization. If the faint-end slopes of the UV luminosity functions (UVLFs) during reionization are steep ($\alpha\lesssim-2$) to ${\rm M}_{\rm UV}$ $\sim -3$, then: (i) the ancestors of UFDs produced $>50$% of UV flux from galaxies; (ii) galaxies can maintain reionization with escape fractions that are $>$2 times lower than currently-adopted values; (iii) direct HST and JWST observations may detect only $\sim10-50$% of the UV light from galaxies; (iv) the cosmic star formation history increases by $\gtrsim4-6$ at $z\gtrsim6$. Read More


In this paper, we use stacking analysis to trace the mass-growth, colour evolution, and structural evolution of present-day massive galaxies ($\log(M_{*}/M_{\odot})=11.5$) out to $z=5$. We utilize the exceptional depth and area of the latest UltraVISTA data release, combined with the depth and unparalleled seeing of CANDELS to gather a large, mass-selected sample of galaxies in the NIR (rest-frame optical to UV). Read More


Since the beginning of the new millennium, more than 100 $z\sim 6$ quasars have been discovered through several surveys and followed-up with multi-wavelength observations. These data provided a large amount of information on the growth of supermassive black holes at the early epochs, the properties of quasar host galaxies and the joint formation and evolution of these massive systems. We review the properties of the highest-$z$ quasars known so far, especially focusing on some of the most recent results obtained in (sub-)millimeter bands. Read More


Galaxies with Milky Way-like stellar masses have a wide range of bulge and black hole masses; in turn, these correlate with other properties such as star formation history. While many processes may drive bulge formation, major and minor mergers are expected to play a crucial role. Stellar halos offer a novel and robust measurement of galactic merger history; cosmologically-motivated models predict that mergers with larger satellites produce more massive, higher metallicity stellar halos, reproducing the recently-observed stellar halo metallicity-mass relation. Read More


We use Gaia-ESO Survey iDR4 data to explore the Mg-Al anti-correlation in globular clusters, that were observed as calibrators, as a demonstration of the quality of Gaia-ESO Survey data and analysis. The results compare well with the available literature, within 0.1 dex or less, after a small (compared to the internal spreads) offset between the UVES and the GIRAFFE data of 0. Read More


We present a new study concerning the application of the Schwarzschild orbit superposition method to model spherical galaxies. The method aims to recover the mass and the orbit anisotropy parameter profiles of the objects using measurements of positions and line-of-sight velocities usually available for resolved stellar populations of dwarf galaxies in the Local Group. To test the reliability of the method, we used different sets of mock data extracted from four numerical realizations of dark matter haloes. Read More


The jets from active galactic nuclei exhibit stability which seems to be far superior compared to that of terrestrial and laboratory jets. They manage to propagate over distances up to a billion of initial jet radii. Yet this may not be an indication of some exotic physics but mainly a reflection of the specific environment these jets propagate through. Read More


We present long-slit optical spectra of 12 edge-on low surface brightness galaxies (LSBGs) positioned along their major axes. After performing reddening corrections for the emission-line fluxes measured from the extracted integrated spectra, we measured the gas-phase metallicities of our LSBG sample using both the [NII]/Ha and the R_23 diagnostics. Both sets of oxygen abundances show good agreement with each other, giving a median value of 12 + log(O/H) = 8. Read More