Magnetically Regulated Gas Accretion in High-Redshift Galactic Disks

Abstract

Disk galaxies are in hydrostatic equilibrium along their vertical axis. The pressure allowing for this configuration consists of thermal, turbulent, magnetic and cosmic ray components. For the Milky Way(MW) the thermal pressure contributes ~10% of the total pressure near the plane, with this fraction dropping towards higher altitudes. Out of the rest, magnetic fields contribute ~1/3 of the pressure to distances of ~3kpc above the disk plane. In this letter we attempt to extrapolate these local values to high redshift, rapidly accreting, rapidly star forming disk galaxies and study the effect of the extra pressure sources on the accretion of gas onto the galaxies. In particular, magnetic field tension may convert a smooth cold-flow accretion to clumpy, irregular star formation regions and rates. The infalling gas accumulates on the edge of the magnetic fields, supported by magnetic tension. When the mass of the infalling gas exceeds some threshold mass, its gravitational force cannot be balanced by magnetic tension anymore, and it falls toward the disk's plane, rapidly making stars. Simplified estimations of this threshold mass are consistent with clumpy star formation observed in SINS, UDF, GOODS and GEMS surveys. We discuss the shortcomings of pure hydrodynamic codes in simulating the accretion of cold flows into galaxies, and emphasize the need for magneto-hydrodynamic simulations

12 pages, 3 figures, accepted to ApJL

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Cited by in corpus (8)

• Rotational Support of Giant Clumps in High-z Disc Galaxies
• The growth of dark matter halos: evidence for significant smooth accretion
• IMAGINE: A comprehensive view of the interstellar medium, Galactic magnetic fields and cosmic rays
• Introducing SPHINX-MHD: The Impact of Primordial Magnetic Fields on the First Galaxies, Reionization, and the Global 21cm Signal
• Magnetic fields in the Galactic halo restrict fountain-driven recycling and accretion
• The Sagittarius dwarf galaxy: Where did all the gas go?
• The Magellanic System: the puzzle of the leading gas stream
• Galactic magnetic fields and hierarchical galaxy formation