scholarly journals Dynamically Driven Inflow onto the Galactic Center and its Effect upon Molecular Clouds

2021 ◽  
Vol 922 (1) ◽  
pp. 79
Author(s):  
H Perry Hatchfield ◽  
Mattia C. Sormani ◽  
Robin G. Tress ◽  
Cara Battersby ◽  
Rowan J. Smith ◽  
...  
Keyword(s):  
Molecular Clouds ◽  
Galactic Center ◽  
Critical Role ◽  
Average Density ◽  
Gas Flows ◽  
Hydrodynamic Simulations ◽  
Tracer Particles ◽  
Formation And Evolution ◽  
Self Gravity ◽  
Total Inflow

Abstract The Galactic bar plays a critical role in the evolution of the Milky Way’s Central Molecular Zone (CMZ), driving gas toward the Galactic Center via gas flows known as dust lanes. To explore the interaction between the CMZ and the dust lanes, we run hydrodynamic simulations in arepo, modeling the potential of the Milky Way’s bar in the absence of gas self-gravity and star formation physics, and we study the flows of mass using Monte Carlo tracer particles. We estimate the efficiency of the inflow via the dust lanes, finding that only about a third (30% ± 12%) of the dust lanes’ mass initially accretes onto the CMZ, while the rest overshoots and accretes later. Given observational estimates of the amount of gas within the Milky Way’s dust lanes, this suggests that the true total inflow rate onto the CMZ is 0.8 ± 0.6 M ⊙ yr−1. Clouds in this simulated CMZ have sudden peaks in their average density near the apocenter, where they undergo violent collisions with inflowing material. While these clouds tend to counter-rotate due to shear, co-rotating clouds occasionally occur due to the injection of momentum from collisions with inflowing material (∼52% are strongly counter-rotating, and ∼7% are strongly co-rotating of the 44 cloud sample). We investigate the formation and evolution of these clouds, finding that they are fed by many discrete inflow events, providing a consistent source of gas to CMZ clouds even as they collapse and form stars.

scholarly journals On a Possible Origin of the Gamma-ray Excess around the Galactic Center

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1432
Author(s):  
Dmitry O. Chernyshov ◽  
Andrei E. Egorov ◽  
Vladimir A. Dogiel ◽  
Alexei V. Ivlev
Keyword(s):  
Dark Matter ◽  
Gamma Rays ◽  
Molecular Clouds ◽  
Alternative Explanation ◽  
Gamma Ray ◽  
Galactic Center ◽  
The Self ◽  
Large Area ◽  
Mhd Turbulence ◽  
The Standard Model

Recent observations of gamma rays with the Fermi Large Area Telescope (LAT) in the direction of the inner galaxy revealed a mysterious excess of GeV. Its intensity is significantly above predictions of the standard model of cosmic rays (CRs) generation and propagation with a peak in the spectrum around a few GeV. Popular interpretations of this excess are that it is due to either spherically distributed annihilating dark matter (DM) or an abnormal population of millisecond pulsars. We suggest an alternative explanation of the excess through the CR interactions with molecular clouds in the Galactic Center (GC) region. We assumed that the excess could be imitated by the emission of molecular clouds with depleted density of CRs with energies below ∼10 GeV inside. A novelty of our work is in detailed elaboration of the depletion mechanism of CRs with the mentioned energies through the “barrier” near the cloud edge formed by the self-excited MHD turbulence. This depletion of CRs inside the clouds may be a reason for the deficit of gamma rays from the Central Molecular Zone (CMZ) at energies below a few GeV. This in turn changes the ratio between various emission components at those energies and may potentially absorb the GeV excess by a simple renormalization of key components.

scholarly journals A new way to conserve total energy for Eulerian hydrodynamic simulations with self-gravity

New Astronomy ◽  
2013 ◽  
Vol 19 ◽  
pp. 48-55 ◽  
Author(s):  
Yan-Fei Jiang ◽  
Mikhail Belyaev ◽  
Jeremy Goodman ◽  
James M. Stone
Keyword(s):  
Total Energy ◽  
Hydrodynamic Simulations ◽  
Self Gravity

scholarly journals ALMA view of the circumnuclear disk of the Galactic Center: tidally disrupted molecular clouds falling to the Galactic Center

2018 ◽  
Vol 70 (5) ◽  
Author(s):  
Masato Tsuboi ◽  
Yoshimi Kitamura ◽  
Kenta Uehara ◽  
Takahiro Tsutsumi ◽  
Ryosuke Miyawaki ◽  
...  
Keyword(s):  
Molecular Clouds ◽  
Galactic Center ◽  
Circumnuclear Disk

Molecular Clouds in the Central 100-pc of the Galactic Center

1989 ◽  
pp. 135-140 ◽  
Author(s):  
M. Tsuboi ◽  
T. Handa ◽  
M. Inoue ◽  
J. Inatani ◽  
N. Ukita
Keyword(s):  
Molecular Clouds ◽  
Galactic Center

scholarly journals CO and OH in the Galactic Center Region

1980 ◽  
Vol 87 ◽  
pp. 111-112
Author(s):  
Junji Inatani ◽  
Nobuharu Ukita
Keyword(s):  
Emission Line ◽  
Intensity Ratio ◽  
Molecular Clouds ◽  
Galactic Center ◽  
Point Of View ◽  
The Other ◽  
Kinetic Temperature ◽  
Two Dimensional ◽  
Center Region ◽  
Dimensional Distribution

The two-dimensional distribution of molecular clouds in the galactic center region has been investigated in the CO 115 GHz line and in the OH 1665 and 1667 MHz lines. As the former is an emission line, we can find molecular clouds without the unavoidable bias to continuum sources which is inherent in a survey of OH absorption lines. Because the CO line is usually optically thick, the brightness temperature of the line is directly related to the kinetic temperature of the cloud. On the other hand, the real optical depth of the OH line can be obtained from the intensity ratio between 1665 and 1667 MHz lines (assuming LTE). From this point of view we have compared the CO and OH observational results.

scholarly journals 4.15. Dynamics of the Galactic center molecular clouds

1998 ◽  
Vol 184 ◽  
pp. 197-199
Author(s):  
C. W. Lee ◽  
H. M. Lee ◽  
H.B. Ann ◽  
K.H. Kwon
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Molecular Clouds ◽  
Galactic Center ◽  
Combined Effects ◽  
Gravitational Perturbation ◽  
Particle Hydrodynamics ◽  
Smoothed Particle

We have performed Smoothed Particle Hydrodynamics (SPH) simulations in order to understand the dynamical structures of Galactic Center molecular clouds. In our study it was found that the structures of GC molecular clouds could be induced by the combined effects of a gravitational perturbation by rotating bar potential and the hydrodynamic collisions between the clouds.

scholarly journals Spiral-arm instability – III. Fragmentation of primordial protostellar discs

2019 ◽  
Vol 491 (1) ◽  
pp. L24-L28 ◽  
Author(s):  
Shigeki Inoue ◽  
Naoki Yoshida
Keyword(s):  
Gravitational Instability ◽  
Finite Thickness ◽  
Linear Perturbation ◽  
Gas Cooling ◽  
Formation And Evolution ◽  
Linear Perturbation Theory ◽  
The Stability ◽  
Protostellar Discs ◽  
Self Gravity ◽  
Spiral Arm

ABSTRACT We study the gravitational instability and fragmentation of primordial protostellar discs by using high-resolution cosmological hydrodynamics simulations. We follow the formation and evolution of spiral arms in protostellar discs, examine the dynamical stability, and identify a physical mechanism of secondary protostar formation. We use linear perturbation theory based on the spiral-arm instability (SAI) analysis in our previous studies. We improve the analysis by incorporating the effects of finite thickness and shearing motion of arms, and derive the physical conditions for SAI in protostellar discs. Our analysis predicts accurately the stability and the onset of arm fragmentation that is determined by the balance between self-gravity and gas pressure plus the Coriolis force. Formation of secondary and multiple protostars in the discs is explained by the SAI, which is driven by self-gravity and thus can operate without rapid gas cooling. We can also predict the typical mass of the fragments, which is found to be in good agreement with the actual masses of secondary protostars formed in the simulation.

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