Kinematics Of Molecular Clouds Research Articles

3D Morphology and Motions of the Canis Major Region from Gaia DR3

The Canis Major (CMa) region is known for its prominent arc-shaped morphology, visible at multiple wavelengths. This study integrates molecular gas data with high-precision astrometric parameters of young stellar objects (YSOs) from Gaia DR3 to provide the first three-dimensional (3D) insights into the dynamical evolution and star formation history of the CMa region. By utilizing the average distances and proper motions of the YSOs as proxies for those of the molecular clouds (MCs), we confirm the presence of a slowly expanding shell-like morphology in the CMa region, with an estimated radius of 47 ± 11 pc and expansion velocity of 1.6 ± 0.7 km s−1. Further, the dynamical evolution of the shell supports its expansion, with an expansion timescale of ∼4.4 Myr obtained by the traceback analysis assuming constant velocities. Finally, a momentum estimate suggests that at least two supernova explosions are needed to power the observed expanding shell, reinforcing the previous hypothesis of multiple supernova events. This study effectively combines CO data with the astrometric data of YSOs from Gaia, offering significant support for future studies of the 3D morphology and kinematics of MCs.

A supersonic turbulence origin of Larson's laws

We revisit the origin of Larson's scaling laws describing the structure and kinematics of molecular clouds. Our analysis is based on recent observational measurements and data from a suite of six simulations of the interstellar medium, including effects of self-gravity, turbulence, magnetic field, and multiphase thermodynamics. Simulations of isothermal supersonic turbulence reproduce observed slopes in linewidth-size and mass-size relations. Whether or not self-gravity is included, the linewidth-size relation remains the same. The mass-size relation, instead, substantially flattens below the sonic scale, as prestellar cores start to form. Our multiphase models with magnetic field and domain size 200 pc reproduce both scaling and normalization of the first Larson law. The simulations support a turbulent interpretation of Larson's relations. This interpretation implies that: (i) the slopes of linewidth-size and mass-size correlations are determined by the inertial cascade; (ii) none of the three Larson laws is fundamental; (iii) instead, if one is known, the other two follow from scale invariance of the kinetic energy transfer rate. It does not imply that gravity is dynamically unimportant. The self-similarity of structure established by the turbulence breaks in star-forming clouds due to the development of gravitational instability in the vicinity of the sonic scale. The instability leads to the formation of prestellar cores with the characteristic mass set by the sonic scale. The high-end slope of the core mass function predicted by the scaling relations is consistent with the Salpeter power-law index.

Smoothed Particle Hydrodynamic Simulations of Galactic Gaseous Disk with Bar: Distribution and Kinematic Structure of Molecular Clouds toward the Galactic Center

We have performed smoothed particle hydrodynamic (SPH) simulations to study the response of molecular clouds in the Galactic disk to a rotating bar and their subsequent evolution in the Galactic center (GC) region. The Galactic potential in our models is contributed by three axisymmetric components (massive halo, exponential disk, compact bulge) and a nonaxisymmetric bar. These components are assumed to be invariant in time in the frame corotating with the bar. Some noticeable features such as an elliptical outer ring, spiral arms, a gas-depletion region, and a central concentration have been developed due to the influence of the bar. The rotating bar induces noncircular motions of the SPH particles, but hydrodynamic collisions tend to suppress the random components of the velocity. The velocity field of the SPH particles is consistent with the kinematics of molecular clouds observed in HCN (1-0) transition; these clouds are thought to be very dense clouds. However, the longitude-velocity (l-v) diagram of the clouds traced by CO is quite different from that of our SPH simulation, being more similar to that obtained from simulations using collisionless particles. The l-v diagram of a mixture of collisional and collisionless particles gives better reproduction of the kinematic structures of the GC clouds observed in the CO line. The fact that the kinematics of HCN clouds can be reproduced by the SPH particles suggests that the dense clouds in the GC are formed via cloud collisions induced by the rotating bar.

On the structure and kinematics of molecular clouds from large scale mapping of mm-lines

Molecular gas in the interior of the Orion superbubble consists of sheets, filaments, and partial shells in which the active star forming dense cloud cores are embedded. The main body of the Orion A and B clouds and at least 14 smaller clouds in Orion region are cometary in appearance suggesting strong interaction with massive stars in the Orion OB association. While the small scale (< 1 pc) structure of the clouds may be determined primarily by internal magnetic fields, gravity, and the effects of outflows from young stellar objects, the large scale morphology and kinematics is affected by the energy injected by massive stars. Supernovae, stellar winds, and radiation have compressed, accelerated, ablated, and dispersed molecular gas over the last 107 years. Most GMC/OB star complexes in the Solar neighborhood exhibit morphological and kinematic properties similar to the Orion region. We argue that energy injection by massive stars plays a vital role in the evolution of the ISM and may be responsible for much of the observed large-scale structure and kinematics of molecular clouds.

On the structure and kinematics of molecular clouds from large scale mapping of mm-lines

Molecular gas in the interior of the Orion superbubble consists of sheets, filaments, and partial shells in which the active star forming dense cloud cores are embedded. The main body of the Orion A and B clouds and at least 14 smaller clouds in Orion region are cometary in appearance suggesting strong interaction with massive stars in the Orion OB association. While the small scale (< 1 pc) structure of the clouds may be determined primarily by internal magnetic fields, gravity, and the effects of outflows from young stellar objects, the large scale morphology and kinematics is affected by the energy injected by massive stars. Supernovae, stellar winds, and radiation have compressed, accelerated, ablated, and dispersed molecular gas over the last 107 years. Most GMC/OB star complexes in the Solar neighborhood exhibit morphological and kinematic properties similar to the Orion region. We argue that energy injection by massive stars plays a vital role in the evolution of the ISM and may be responsible for much of the observed large-scale structure and kinematics of molecular clouds.

Kinematics of molecular clouds. II - New data on nearby giant molecular clouds

view Abstract Citations (121) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Kinematics of Molecular Clouds. II. New Data on Nearby Giant Molecular Clouds Stark, Antony A. ; Brand, Jan Abstract The best currently available data on positions, distances, and velocities of giant molecular clouds within 3 kpc of the sun are analyzed to yield a one-dimensional rms cloud-to-cloud velocity dispersion of 7.8 +0.6, -0.5. Velocity dispersion is defined here as the root mean square of cloud peculiar velocities, a quantity which includes small-scale streaming. It is argued that this value for the velocity dispersion is pausible, based on examples of clouds whose velocities cannot be explained purely by galactic rotation. The mean motion of nearby molecular clouds is drifting by about 4 km/s with respect to the LSR. Publication: The Astrophysical Journal Pub Date: April 1989 DOI: 10.1086/167334 Bibcode: 1989ApJ...339..763S Keywords: Computational Astrophysics; Milky Way Galaxy; Molecular Clouds; Kinematics; Radial Velocity; Velocity Distribution; Astrophysics; GALAXIES: INTERNAL MOTIONS; INTERSTELLAR: MOLECULES; RADIAL VELOCITIES full text sources ADS | data products SIMBAD (108)

Kinematics of molecular clouds. I - Velocity dispersion in the solar neighborhood

Kinematics of molecular clouds. I - Velocity dispersion in the solar neighborhood

Radiation transport and the kinematics of molecular clouds

view Abstract Citations (43) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Radiation transport and the kinematics of molecular clouds. Kwan, J. Abstract The large widths of millimeter molecular lines have been interpreted as being due to either systematic motion or local turbulence in molecular clouds. This paper evaluates the merits of each interpretation by comparing line profiles produced in either a systematic motion or a turbulent motion under the same conditions of temperature and density with the stipulation that both temperature and density decrease with increasing distance from a central point. Molecular-line observations of the M17 SW region and the Kleinmann-Low (KL) nebula are analyzed, particularly with respect to various CO and CS lines. It is found that the observations of M17 SW are best explained by a model in which turbulence dominates the central part of the molecular region but collapse prevails in the outer part, while the observations of the KL nebula can be equally well explained by either of two models. The first model postulates that KL is at the front face of the molecular cloud and turbulence gives rise to the line broadening; the second places KL deep within the molecular cloud and attributes only the CO line widths to systematic motion about the nebula. Publication: The Astrophysical Journal Pub Date: July 1978 DOI: 10.1086/156245 Bibcode: 1978ApJ...223..147K Keywords: Interstellar Matter; Molecular Spectra; Nebulae; Radiative Transfer; Astronomical Models; Carbon Monoxide; Kinematics; Millimeter Waves; Spectral Line Width; Astrophysics; Kinematics:Molecular Clouds; Line Profiles:Molecular Clouds; Molecular Clouds:Radiative Transfer full text sources ADS |

Kinematics of Molecular Clouds Near the Galactic Center

Kinematics of Molecular Clouds Near the Galactic Center