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Describing how the properties of the interstellar medium combine across size-scales is crucial for understanding star formation scaling laws and connecting Galactic and extragalactic data of molecular clouds. We describe how the statistical…

Astrophysics of Galaxies · Physics 2021-09-15 Andri Spilker , Jouni Kainulainen , Jan Orkisz

This study is aimed to contribute to a more comprehensive understanding of the molecular hydrogen distribution in the galaxy M33 by introducing novel methods for generating high angular resolution (18.2$''$, equivalent to 75 pc) column…

We study the probability distribution function (PDF) of mass surface densities, $\Sigma$, of infrared dark cloud (IRDC) G028.37+00.07 and its surrounding giant molecular cloud. This PDF constrains the physical processes, such as turbulence,…

Astrophysics of Galaxies · Physics 2016-09-23 Wanggi Lim , Jonathan C. Tan , Jouni Kainulainen , Bo Ma , Michael J. Butler

We present three-dimensional astrochemical simulations and synthetic observations of magnetised, turbulent, self-gravitating molecular clouds. We explore various galactic interstellar medium environments, including cosmic-ray ionization…

Astrophysics of Galaxies · Physics 2021-01-20 Thomas G. Bisbas , Jonathan C. Tan , Kei E. I. Tanaka

We present a far-IR survey of the entire Mon R2 GMC with $Herschel-SPIRE$ cross-calibrated with $Planck-HFI$ data. We fit the SEDs of each pixel with a greybody function and an optimal beta value of 1.8. We find that mid-range column…

Astrophysics of Galaxies · Physics 2016-06-07 R. Pokhrel , R. Gutermuth , B. Ali , T. Megeath , J. Pipher , P. Myers , W. J. Fischer , T. Henning , S. J. Wolk , L. Allen , J. J. Tobin

We report on a comparison between 21 cm rotation measure (RM) and the optically-thin atomic hydrogen column density (N_HI) measured towards unresolved extragalactic sources in the Galactic plane of the northern sky. HI column densities…

Astrophysics of Galaxies · Physics 2015-06-16 Tyler Foster , Roland Kothes , Joanne Brown

In this contribution, we test our previously published one-dimensional PDR model for deriving total hydrogen volume densities from HI column density measurements in extragalactic regions by applying it to the Taurus molecular cloud, where…

Astrophysics of Galaxies · Physics 2015-06-12 J. S. Heiner , E. Vázquez-Semadeni

(Abridged) We discuss the probability distribution function (PDF) of column density resulting from density fields with lognormal PDFs, applicable to isothermal gas (e.g., probably molecular clouds). We suggest that a ``decorrelation…

Astrophysics · Physics 2009-11-06 Enrique Vazquez-Semadeni , Nieves Garcia

Radiative transfer models in a spherical, turbulent interstellar medium (ISM) in which the photon source is situated at the center are calculated to investigate the correlation between the scattered light and the dust column density. The…

Astrophysics of Galaxies · Physics 2015-06-17 Kwang-Il Seon , Adolf N. Witt

We analyze the evolution of shock waves in high-resolution 3D radiative MHD simulations of the quiet Sun and their synthetic emission characteristics. The simulations model the dynamics of a 12.8x12.8x15.2 Mm quiet-Sun region (including a…

Solar and Stellar Astrophysics · Physics 2021-03-16 Viacheslav M. Sadykov , Irina N. Kitiashvili , Alexander G. Kosovichev , Alan A. Wray

We study the high column density regime of the HI column density distribution function and argue that there are two distinct features: a turnover at NHI ~ 10^21 cm^-2 which is present at both z=0 and z ~ 3, and a lack of systems above NHI ~…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-03 Denis Erkal , Nickolay Y. Gnedin , Andrey V. Kravtsov

The efforts for comparing dust polarization measurements with synthetic observations from MHD models have previously concentrated on the scale of molecular clouds. Here we extend the model comparisons to kiloparsec scales, taking into…

Astrophysics of Galaxies · Physics 2018-06-27 Miikka S. Väisälä , Frederick A. Gent , Mika Juvela , Maarit J. Käpylä

Current data suggest that the central mass densities $\rho_0$ and phase-space densities $Q\equiv\rho_0/\sigma_V^3$ of cosmological halos in the present universe are correlated with their velocity dispersions $\sigma_V$ over a very wide…

Astrophysics · Physics 2009-11-06 Paul R. Shapiro , Ilian T. Iliev

The probability density function (PDF) of the gas density in turbulent supersonic flows is investigated with high-resolution numerical simulations. In a systematic study, we compare the density statistics of compressible turbulence driven…

Astrophysics · Physics 2009-11-13 Christoph Federrath , Ralf S. Klessen , Wolfram Schmidt

We analyze circumgalactic medium (CGM) in a suite of high-resolution cosmological re-simulations of a Milky-Way size galaxy and show that CGM properties are quite sensitive to details of star formation--feedback loop modelling. The…

Astrophysics of Galaxies · Physics 2016-03-09 Cameron J. Liang , Andrey V. Kravtsov , Oscar Agertz

We investigate physical properties of molecular clouds in disc galaxies with different morphology: a galaxy without prominent structure, a spiral barred galaxy and a galaxy with flocculent structure. Our $N$-body/hydrodynamical simulations…

Astrophysics of Galaxies · Physics 2016-03-02 S. A. Khoperskov , E. O. Vasiliev , D. A. Ladeyschikov , A. M. Sobolev , A. V. Khoperskov

Stars form in cold molecular clouds. However, molecular gas is difficult to observe because the most abundant molecule (H2) lacks a permanent dipole moment. Rotational transitions of CO are often used as a tracer of H2, but CO is much less…

The linewidth (sigma) - size (R) relationship has been extensively measured and analysed, in both the local ISM and in nearby normal galaxies. Generally, a power-law describes the relationship well with an index ranging from 0.2-0.6, now…

Astrophysics of Galaxies · Physics 2015-06-05 Rahul Shetty , Christopher N. Beaumont , Michael G. Burton , Brandon C. Kelly , Ralf S. Klessen

We carry out an extensive study of the cosmic Mach number (\mach) on scales of R=5, 10 and 20h^-1Mpc using an LCDM hydrodynamical simulation. We particularly put emphasis on the environmental dependence of \mach on overdensity, galaxy mass,…

Astrophysics · Physics 2009-10-31 Kentaro Nagamine , Jeremiah P. Ostriker , Renyue Cen

Three-dimensional (3D) radiative magnetohydrodynamics (MHD) simulations are the only way to model stellar atmospheres without any ad hoc parameterisations. Several 3D radiative MHD codes have achieved good quantitative agreement with…

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