Magnetic Fields and Galactic Star Formation Rates

Abstract

The regulation of galactic-scale star formation rates (SFRs) is a basic problem for theories of galaxy formation and evolution: which processes are responsible for making observed star formation rates so inefficient compared to maximal rates of gas content divided by dynamical timescale? Here we study the effect of magnetic fields of different strengths on the evolution of giant molecular clouds (GMCs) within a kiloparsec patch of a disk galaxy and resolving scales down to $\simeq 0.5\mathrm{pc}$. Including an empirically motivated prescription for star formation from dense gas ($n_{\mathrm{H}}>10^5{\mathrm{cm}}^{-3}$) at an efficiency of 2\% per local free-fall time, we derive the amount of suppression of star formation by magnetic fields compared to the nonmagnetized case. We find GMC fragmentation, dense clump formation and SFR can be significantly affected by the inclusion of magnetic fields, especially in our strongest investigated $B$-field case of $80\mu$G. However, our chosen kpc-scale region, extracted from a global galaxy simulation, happens to contain a starbursting cloud complex that is only modestly affected by these magnetic fields and likely requires internal star formation feedback to regulate its SFR.

7 pages, 5 figures. Accepted by ApJ Letters

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Cited by in corpus (7)

• Cooling, AGN Feedback and Star Formation in Simulated Cool-Core Galaxy Clusters
• GMC Collisions as Triggers of Star Formation. III. Density and Magnetically Regulated Star Formation
• Ab initio Simulations of a Supernova Driven Galactic Dynamo in an Isolated Disk Galaxy
• The Interstellar Medium and Star Formation of Galactic Disks. I. ISM and GMC properties with Diffuse FUV and Cosmic Ray Backgrounds
• Constraining the magnetic field properties of Bok globule B335 using SOFIA/HAWC+
• Magnetic Fields, Star Formation Rates and Gas Densities at Sub-kpc Scales in a Pilot Sample of Nearby Galaxies
• Magnetic fields in star forming environments: how does field strength affect gas on spiral arm and cloud scales?