The Pressure of an Equilibrium Interstellar Medium in Galactic Disks

Abstract

Based on an axisymmetric galactic disk model, we estimate the equilibrium gas pressure P/k in the disk plane as a function of the galactocentric distance R for several galaxies (MW, M33, M51, M81, M100, M101, M106, and the SMC). For this purpose, we solve a self-consistent system of equations by taking into account the gas self-gravity and the presence of a dark pseudo-isothermal halo. We assume that the turbulent velocity dispersions of the atomic and molecular gases are fixed and that the velocity dispersion of the old stellar disk corresponds to its marginal stability (except for the Galaxy and the SMC). We also consider a model with a constant disk thickness. Of the listed galaxies, the SMC and M51 have the highest pressure at a given relative radius R/R_25, while M81 has the lowest pressure. The pressure dependence of the relative molecular gas fraction confirms the existence of a positive correlation between these quantities, but it is not so distinct as that obtained previously when the pressure was estimated very roughly. This dependence breaks down for the inner regions of M81 and M106, probably because the gas pressure has been underestimated in the bulge region. We discuss the possible effects of factors other than the pressure affecting the relative content of molecular gas in the galaxies under consideration.

10 pages, 5 figures

References in corpus (5)

• The Role of Pressure in GMC Formation II: The H_2 - Pressure Relation
• Simulating the formation of molecular clouds. II. Rapid formation from turbulent initial conditions
• The Spitzer Survey of the Small Magellanic Cloud: FIR Emission and Cold Gas in the SMC
• Spectroscopic Survey of Red Giants in the SMC. I: Kinematics
• Spiral shocks and the formation of molecular clouds in a two phase medium

Cited by in corpus (11)

• Non-Thermal Insights on Mass and Energy Flows Through the Galactic Centre and into the Fermi Bubbles
• Pressure Relations and Vertical Equilibrium in the Turbulent, Multiphase ISM
• Magnetic fields in nearby normal galaxies: Energy equipartition
• The Interstellar Medium and Star Formation in Edge-On Galaxies. I. NGC 891
• The portrait of Malin 2: a case study of a giant low surface brightness galaxy
• Magnetic fields near the peripheries of galactic discs
• A High-Resolution, Dust-Selected Molecular Cloud Catalogue of M33, the Triangulum Galaxy
• On the star-forming ability of Molecular Clouds
• Atomic and Molecular Gas Components in Spiral Galaxies of the Virgo Cluster
• Can molecular clouds live long?
• Molecular cloud matching in CO and dust in M33 II. Physical properties of giant molecular clouds