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Molecular-line observations of filaments in star-forming regions have revealed the existence of elongated coherent features within the filaments; these features are termed fibres. Here we caution that, since fibres are traced in PPV space,…

Astrophysics of Galaxies · Physics 2018-07-11 S. D. Clarke , A. P. Whitworth , R. L. Spowage , A. Duarte-Cabral , S. T. Suri , S. E. Jaffa , S. Walch , P. C. Clark

We performed synthetic observations of the Ulrich, Cassen, and Moosman (UCM) model to understand the relation between the physical structures of the infalling envelope around a protostar and their observational features in molecular lines,…

Solar and Stellar Astrophysics · Physics 2024-01-15 Shoji Mori , Yuri Aikawa , Yoko Oya , Satoshi Yamamoto , Nami Sakai

We employ the Delta-variance analysis and study the turbulent gas dynamics of simulated molecular clouds (MCs). Our models account for a simplified treatment of time-dependent chemistry and the non-isothermal nature of the gas. We…

Solar and Stellar Astrophysics · Physics 2015-08-06 Erik Bertram , Ralf S. Klessen , Simon C. O. Glover

The virial ratio between kinetic and gravitational terms provides key insight into the balance of forces that confine a molecular cloud, but the clumpy and filamentary structures of resolved clouds make it difficult to evaluate this ratio…

Astrophysics of Galaxies · Physics 2019-06-17 Ayushi Singh , Christopher D. Matzner , Peter H. Jumper

The structure and star formation activity of a molecular cloud are fundamentally linked to its internal turbulence. However, accurately measuring the turbulent velocity dispersion is challenging due to projection effects and observational…

Astrophysics of Galaxies · Physics 2021-12-22 Madeleine Stewart , Christoph Federrath

Molecular line observations using a variety of tracers are often used to investigate the kinematic structure of molecular clouds. However, measurements of cloud velocity dispersions with different lines, even in the same region, often yield…

Astrophysics of Galaxies · Physics 2020-09-30 Yuxuan Yuan , Mark R. Krumholz , Blakesley Burkhart

We compute structure functions and Fourier spectra of 2D centroid velocity (CV) maps in order to study the gas dynamics of typical molecular clouds (MCs) in numerical simulations. We account for a simplified treatment of time-dependent…

Solar and Stellar Astrophysics · Physics 2015-06-23 Erik Bertram , Lukas Konstandin , Rahul Shetty , Simon C. O. Glover , Ralf S. Klessen

Observations of molecular lines are a key tool to determine the main physical properties of prestellar cores. However, not all the information is retained in the observational process or easily interpretable, especially when a larger number…

Astrophysics of Galaxies · Physics 2025-10-08 T. Grassi , M. Padovani , D. Galli , N. Vaytet , S. S. Jensen , E. Redaelli , S. Spezzano , S. Bovino , P. Caselli

We leverage the 1 pc spatial resolution of the Leike et al. 2020 3D dust map to characterize the three-dimensional structure of nearby molecular clouds ($d \lesssim 400$ pc). We start by "skeletonizing" the clouds in 3D volume density space…

I review recent results derived from numerical simulations of the turbulent interstellar medium (ISM), in particular concerning the nature and formation of turbulent clouds, methods for comparing the structure in simulations and…

Astrophysics · Physics 2018-03-28 Enrique Vázquez-Semadeni

The energy cascade rate of turbulence can be measured with the structure function. In practice, the 3D velocity of the gas in molecular cloud is hard to measure, which makes the measurement of structure function difficult. In the case of…

Astrophysics of Galaxies · Physics 2021-06-16 Lei Qian

Context: Understanding how protostars accrete their mass is a central question of star formation. One aspect of this is trying to understand whether the time evolution of accretion rates in deeply embedded objects is best characterised by a…

Solar and Stellar Astrophysics · Physics 2016-02-17 Søren Frimann , Jes K. Jørgensen , Paolo Padoan , Troels Haugbølle

We present a comparison of molecular clouds (MCs) from a simulation of supernova-driven interstellar medium (ISM) turbulence with real MCs from the Outer Galaxy Survey. The radiative transfer calculations to compute synthetic CO spectra are…

Astrophysics of Galaxies · Physics 2016-08-03 Paolo Padoan , Mika Juvela , Liubin Pan , Troels Haugbølle , Åke Nordlund

Non-ideal MHD effects are thought to be a crucial component of the star-formation process. Numerically, several complications render the study of non-ideal MHD effects in 3D simulations extremely challenging and hinder our efforts of…

Astrophysics of Galaxies · Physics 2025-02-12 E. Agianoglou , A. Tritsis , K. Tassis

With ALMA making it possible to resolve giant molecular clouds (GMCs) in other galaxies, it is becoming necessary to quantify the observational bias on measured GMC properties. Using a hydrodynamical simulation of a barred spiral galaxy, we…

Star formation has long been known to be an inefficient process, in the sense that only a small fraction $\epsilon_{\rm ff}$ of the mass of any given gas cloud is converted to stars per cloud free-fall time. However, developing a successful…

Astrophysics of Galaxies · Physics 2021-02-17 Zipeng Hu , Mark R. Krumholz , Christoph Federrath , Riwaj Pokhrel , Robert A. Gutermuth

Particle Image Velocimetry (PIV) estimates velocities through correlations of particle images within interrogation windows, leading to a spatial modulation of the velocity field. Although in principle Particle Tracking Velocimetry (PTV)…

Fluid Dynamics · Physics 2023-02-14 Iacopo Tirelli , Andrea Ianiro , Stefano Discetti

Velocity fields of molecular clouds (MCs) can provide crucial information on the merger and split between clouds, as well as their internal kinematics and maintenance, energy injection and redistribution, even star formation within clouds.…

Astrophysics of Galaxies · Physics 2024-03-12 Lixia Yuan , Ji Yang , Xuepeng Chen , Yang Su , Shaobo Zhang , Xin Zhou , Zhiwei Chen , Qing-Zeng Yan , Min Fang , Fujun Du , Yan Sun , Hongchi Wang , Ye Xu

Polarimeric maps have been used on the characterization of the magnetic field in molecular clouds. However, it is difficult to determine the 3-dimensional properties of these regions from the projected maps. In that case, numerical…

Astrophysics · Physics 2008-12-23 D. Falceta-Goncalves , A. Lazarian , G. Kowal

Polytropic models are reasonably successful in acounting for the observed features of molecular clouds. Multi-pressure polytropes include the various pressure components that are important in molecular clouds, whereas composite polytropes…

Astrophysics · Physics 2007-05-23 Christopher F. McKee