TY - JOUR A1 - Hani, Maan H. A1 - Ellison, Sara L. A1 - Sparre, Martin A1 - Grand, Robert J. J. A1 - Pakmor, Rüdiger A1 - Gómez, Facundo A. A1 - Springel, Volker T1 - The diversity of the circumgalactic medium around z=0 Milky Way-mass galaxies from the Auriga simulations JF - Monthly notices of the Royal Astronomical Society N2 - Galaxies are surrounded by massive gas reservoirs ( i.e. the circumgalactic medium; CGM) which play a key role in their evolution. The properties of the CGM, which are dependent on a variety of internal and environmental factors, are often inferred from absorption line surveys which rely on a limited number of single lines-of-sight. In this work we present an analysis of 28 galaxy haloes selected from the Auriga project, a cosmological magneto-hydrodynamical zoom-in simulation suite of isolated MilkyWay-mass galaxies, to understand the impact of CGM diversity on observational studies. Although the Auriga haloes are selected to populate a narrow range in halo mass, our work demonstrates that the CGM of L-star galaxies is extremely diverse: column densities of commonly observed species span similar to 3-4 dex and their covering fractions range from similar to 5 to 90 per cent. Despite this diversity, we identify the following correlations: 1) the covering fractions ( CF) of hydrogen and metals of the Auriga haloes positively correlate with stellar mass, 2) the CF of H I, C IV, and Si II anticorrelate with active galactic nucleus luminosity due to ionization effects, and 3) the CF of H I, C IV, and Si II positively correlate with galaxy disc fraction due to outflows populating the CGM with cool and dense gas. The Auriga sample demonstrates striking diversity within the CGM of L-star galaxies, which poses a challenge for observations reconstructing CGM characteristics from limited samples, and also indicates that long-term merger assembly history and recent star formation are not the dominant sculptors of the CGM. KW - methods: numerical KW - galaxies: evolution KW - galaxies: haloes Y1 - 2019 U6 - https://doi.org/10.1093/mnras/stz1708 SN - 0035-8711 SN - 1365-2966 VL - 488 IS - 1 SP - 135 EP - 152 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Meyer, Dominique M.-A. A1 - Kreplin, Alexander A1 - Kraus, S. A1 - Vorobyov, E. I. A1 - Haemmerlé, Lionel A1 - Eislöffel, Jochen T1 - On the ALMA observability of nascent massive multiple systems formed by gravitational instability JF - Monthly notices of the Royal Astronomical Society N2 - Massive young stellar objects (MYSOs) form during the collapse of high-mass pre-stellar cores, where infalling molecular material is accreted through a centrifugally balanced accretion disc that is subject to efficient gravitational instabilities. In the resulting fragmented accretion disc of the MYSO, gaseous clumps and low-mass stellar companions can form, which will influence the future evolution of massive protostars in the Hertzsprung-Russell diagram. We perform dust continuum radiative transfer calculations and compute synthetic images of disc structures modelled by the gravito-radiation-hydrodynamics simulation of a forming MYSO, in order to investigate the Atacama Large Millimeter/submillimeter Array (alma) observability of circumstellar gaseous clumps and forming multiple systems. Both spiral arms and gaseous clumps located at similar or equal to a few from the protostar can be resolved by interferometric alma Cycle 7 C43-8 and C43-10 observations at band 6 (), using a maximal 0.015 aracsec beam angular resolution and at least exposure time for sources at distances of . Our study shows that substructures are observable regardless of their viewing geometry or can be inferred in the case of an edge-viewed disc. The observation probability of the clumps increases with the gradually increasing efficiency of gravitational instability at work as the disc evolves. As a consequence, large discs around MYSOs close to the zero-age-main-sequence line exhibit more substructures than at the end of the gravitational collapse. Our results motivate further observational campaigns devoted to the close surroundings of the massive protostars S255IR-NIRS3 and NGC 6334I-MM1, whose recent outbursts are a probable signature of disc fragmentation and accretion variability. KW - radiative transfer KW - methods: numerical KW - stars: circumstellar matter Y1 - 2019 U6 - https://doi.org/10.1093/mnras/stz1585 SN - 0035-8711 SN - 1365-2966 VL - 487 IS - 4 SP - 4473 EP - 4491 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Seiler, Michael A1 - Seiß, Martin A1 - Hoffmann, Holger A1 - Spahn, Frank T1 - Hydrodynamic Simulations of Asymmetric Propeller Structures in Saturn's Rings JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Supplement series N2 - The observation of the non-Keplerian behavior of propeller structures in Saturn's outer A ring raises the question: how does the propeller respond to the wandering of the central embedded moonlet? Here, we study numerically how the structural imprint of the propeller changes for a libration of the moonlet. It turns out that the libration induces an asymmetry in the propeller, which depends on the libration period and amplitude of the moonlet. Further, we study the dependence of the asymmetry on the libration period and amplitude for a moonlet with a 400 m Hill radius, which is located in the outer A ring. This allows us to apply our findings to the largest known propeller Blériot, which is expected to be of a similar size. For Blériot, we can conclude that, supposing the moonlet is librating with the largest observed period of 11.1 yr and an azimuthal amplitude of about 1845 km, a small asymmetry should be measurable but depends on the moonlet's libration phase at the observation time. The longitude residuals of other trans-Encke propellers (e.g., Earhart) show amplitudes similar to Blériot, which might allow us to observe larger asymmetries due to their smaller azimuthal extent, allowing us to scan the whole gap structure for asymmetries in one observation. Although the librational model of the moonlet is a simplification, our results are a first step toward the development of a consistent model for the description of the formation of asymmetric propellers caused by a freely moving moonlet. KW - Hydrodynamics KW - methods: data analysis KW - methods: numerical KW - planets and satellites: dynamical evolution and stability KW - planets and satellites: individual (Saturn) KW - planets and satellites: rings Y1 - 2019 U6 - https://doi.org/10.3847/1538-4365/ab26b0 SN - 0067-0049 SN - 1538-4365 VL - 243 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Despali, Giulia A1 - Sparre, Martin A1 - Vegetti, Simona A1 - Vogelsberger, Mark A1 - Zavala, Jesús A1 - Marinacci, Federico T1 - The interplay of self-interacting dark matter and baryons in shaping the halo evolution JF - Monthly notices of the Royal Astronomical Society N2 - We use high-resolution hydrodynamical simulation to test the difference of halo properties in cold dark matter (CDM) and a self-interacting dark matter (SIDM) scenario with a constant cross-section of sigma(T)/m(x) = 1 cm(2) g(-1). We find that the interplay between dark matter self-interaction and baryonic physics induces a complex evolution of the halo properties, which depends on the halo mass and morphological type, as well as on the halo mass accretion history. While high-mass haloes, selected as analogues of early-type galaxies, show cored profiles in the SIDM run, systems of intermediate mass and with a significant disc component can develop a profile that is similar or cuspier than in CDM. The final properties of SIDM haloes - measured at z = 0.2 - correlate with the halo concentration and formation time, suggesting that the differences between different systems are due to the fact that we are observing the impact of self-interaction. We also search for signatures of SIDM in the lensing signal of the main haloes and find hints of potential differences in the distribution of Einstein radii, which suggests that future wide-field survey might be able to distinguish between CDM and SIDM models on this basis. Finally, we find that the subhalo abundances are not altered in the adopted SIDM model with respect to CDM. KW - gravitational lensing: strong KW - methods: numerical KW - galaxies: haloes KW - dark matter Y1 - 2019 U6 - https://doi.org/10.1093/mnras/stz273 SN - 0035-8711 SN - 1365-2966 VL - 484 IS - 4 SP - 4563 EP - 4573 PB - Oxford University Press CY - Oxford ER - TY - JOUR A1 - Thomas, T. A1 - Pfrommer, Christoph T1 - Cosmic-ray hydrodynamics BT - alfvén-wave regulated transport of cosmic rays JF - Monthly notices of the Royal Astronomical Society N2 - Star formation in galaxies appears to be self-regulated by energetic feedback processes. Among the most promising agents of feedback are cosmic rays (CRs), the relativistic ion population of interstellar and intergalactic plasmas. In these environments, energetic CRs are virtually collisionless and interact via collective phenomena mediated by kinetic-scale plasma waves and large-scale magnetic fields. The enormous separation of kinetic and global astrophysical scales requires a hydrodynamic description. Here, we develop a new macroscopic theory for CR transport in the self-confinement picture, which includes CR diffusion and streaming. The interaction between CRs and electromagnetic fields of Alfvenic turbulence provides the main source of CR scattering, and causes CRs to stream along the magnetic field with the Alfven velocity if resonant waves are sufficiently energetic. However, numerical simulations struggle to capture this effect with current transport formalisms and adopt regularization schemes to ensure numerical stability. We extent the theory by deriving an equation for the CRmomentum density along the mean magnetic field and include a transport equation for the Alfven-wave energy. We account for energy exchange of CRs and Alfven waves via the gyroresonant instability and include other wave damping mechanisms. Using numerical simulations, we demonstrate that our new theory enables stable, self-regulated CR transport. The theory is coupled to magnetohydrodynamics, conserves the total energy and momentum, and correctly recovers previous macroscopic CR transport formalisms in the steady-state flux limit. Because it is free of tunable parameters, it holds the promise to provide predictable simulations of CR feedback in galaxy formation. KW - hydrodynamics KW - radiative transfer KW - methods: analytical KW - methods: numerical KW - cosmic rays Y1 - 2019 U6 - https://doi.org/10.1093/mnras/stz263 SN - 0035-8711 SN - 1365-2966 VL - 485 IS - 3 SP - 2977 EP - 3008 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Bohdan, Artem A1 - Niemiec, Jacek A1 - Pohl, Martin A1 - Matsumoto, Yosuke A1 - Amano, Takanobu A1 - Hoshino, Masahiro T1 - Kinetic Simulations of Nonrelativistic Perpendicular Shocks of Young Supernova Remnants BT - I. Electron Shock-surfing Acceleration JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - Electron injection at high Mach number nonrelativistic perpendicular shocks is studied here for parameters that are applicable to young SNR shocks. Using high-resolution large-scale two-dimensional fully kinetic particle-in-cell simulations and tracing individual particles, we in detail analyze the shock-surfing acceleration (SSA) of electrons at the leading edge of the shock foot. The central question is to what degree the process can be captured in 2D3V simulations. We find that the energy gain in SSA always arises from the electrostatic field of a Buneman wave. Electron energization is more efficient in the out-of-plane orientation of the large-scale magnetic field because both the phase speed and the amplitude of the waves are higher than for the in-plane scenario. Also, a larger number of electrons is trapped by the waves compared to the in-plane configuration. We conclude that significant modifications of the simulation parameters are needed to reach the same level of SSA efficiency as in simulations with out-of-plane magnetic field or 3D simulations. KW - acceleration of particles KW - instabilities KW - ISM: supernova remnants KW - methods: numerical KW - plasmas KW - shock waves Y1 - 2019 U6 - https://doi.org/10.3847/1538-4357/ab1b6d SN - 0004-637X SN - 1538-4357 VL - 878 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER -