Synthetic observations of molecular clouds in a galactic center environment: I. Studying maps of column density and integrated intensity

Abstract

We run numerical simulations of molecular clouds (MCs), adopting properties similar to those found in the Central Molecular Zone (CMZ) of the Milky Way. For this, we employ the moving mesh code Arepo and perform simulations which account for a simplified treatment of time-dependent chemistry and the non-isothermal nature of gas and dust. We perform simulations using an initial density of n_0 = 10^3 cm^{-3} and a mass of 1.3x10^5 M_sun. Furthermore, we vary the virial parameter, defined as the ratio of kinetic and potential energy, alpha = E_{kin} / |E_{pot}|, by adjusting the velocity dispersion. We set it to alpha = 0.5, 2.0 and 8.0, in order to analyze the impact of the kinetic energy on our results. We account for the extreme conditions in the CMZ and increase both the interstellar radiation field (ISRF) and the cosmic-ray flux (CRF) by a factor of 1000 compared to the values found in the solar neighbourhood. We use the radiative transfer code RADMC-3D to compute synthetic images in various diagnostic lines. These are [CII] at 158 micron, [OI] (145 micron), [OI] (63 micron), 12CO (J = 1 -> 0) and 13CO (J = 1 -> 0) at 2600 micron and 2720 micron, respectively. When alpha is large, the turbulence disperses much of the gas in the cloud, reducing its mean density and allowing the ISRF to penetrate more deeply into the cloud's interior. This significantly alters the chemical composition of the cloud, leading to the dissociation of a significant amount of the molecular gas. On the other hand, when alpha is small, the cloud remains compact, allowing more of the molecular gas to survive. We show that in each case the atomic tracers accurately reflect most of the physical properties of both the H2 and the total gas of the cloud and that they provide a useful alternative to molecular lines when studying the ISM in the CMZ.

17 pages, 11 figures, accepted for publication in MNRAS (Version 1.1)

References in corpus (15)

• Astrophysics Source Code Library
• Modeling Collapse and Accretion in Turbulent Gas Clouds: Implementation and Comparison of Sink Particles in AMR and SPH
• Simulating the formation of molecular clouds. I. Slow formation by gravitational collapse from static initial conditions
• Herschel Survey of Galactic OH+, H2O+, and H3O+: Probing the Molecular Hydrogen Fraction and Cosmic-Ray Ionization Rate
• GREAT: the SOFIA high-frequency heterodyne instrument
• CO-dark gas and molecular filaments in Milky Way type galaxies
• On the nature of star-forming filaments: I. Filament morphologies
• Effective destruction of CO by cosmic rays: implications for tracing H${}_2$ gas in the Universe
• A cluster in the making: ALMA reveals the initial conditions for high-mass cluster formation
• G0.253+0.016: A centrally condensed, high-mass protocluster
• Cosmic-Ray Heating of Molecular Gas in the Nuclear Disk: Low Star Formation Efficiency
• The dynamics and star-forming potential of the massive Galactic centre cloud G0.253+0.016
• A multi-wavelength view of the Galactic center dust ridge reveals little star formation
• Does the CO-to-H2 conversion factor depend on the star formation rate?
• Star formation efficiencies of molecular clouds in a galactic center environment

Cited by in corpus (15)

• Science with e-ASTROGAM (A space mission for MeV-GeV gamma-ray astrophysics)
• SILCC-Zoom: The dynamical and chemical evolution of molecular clouds
• The dynamical evolution of molecular clouds near the Galactic Centre - II. Spatial structure and kinematics of simulated clouds
• Cosmic rays, gas and dust in nearby anticentre clouds : I -- CO-to-H2 conversion factors and dust opacities
• The HI/OH/Recombination line survey of the inner Milky Way (THOR)
• Gamma rays as probes of cosmic-ray propagation and interactions in galaxies
• How well does CO emission measure the H${}_2$ mass of MCs?
• Synthetic [CII] emission maps of a simulated molecular cloud in formation
• Cosmic-rays, gas, and dust in nearby anticentre clouds : II -- Interstellar phase transitions and the Dark Neutral Medium
• Kinematics and properties of the Central Molecular Zone as probed with [C II]
• Cosmic-rays, gas, and dust in nearby anti-centre clouds : III -- Dust extinction, emission, and grain properties
• An Exploration of the Statistical Signatures of Stellar Feedback
• A study of methanol and silicon monoxide production through episodic explosions of grain mantles in the Central Molecular Zone
• Dust destruction by the supernova remnant forward shock in a turbulent interstellar medium
• Cosmic rays, gas and dust in the Central Molecular Zone I -- $X_{CO}$ factors, cosmic-ray densities and dust opacities