The impact of magnetic fields on the IMF in star-forming clouds near a supermassive black hole

Abstract

Star formation in the centers of galaxies is thought to yield massive stars with a possibly top-heavy stellar mass distribution. It is likely that magnetic fields play a crucial role in the distribution of stellar masses inside star-forming molecular clouds. In this context, we explore the effects of magnetic fields, with a typical field strength of 38 microG, such as in RCW 38, and a field strength of 135 microG, similar to NGC 2024 and the infrared dark cloud G28.34+0.06, on the initial mass function (IMF) near (< 10 pc) a 10^7 solar mass black hole. Using these conditions, we perform a series of numerical simulations with the hydrodynamical code FLASH to elucidate the impact of magnetic fields on the IMF and the star-formation efficiency (SFE) emerging from an 800 solar mass cloud. We find that the collapse of a gravitationally unstable molecular cloud is slowed down with increasing magnetic field strength and that stars form along the field lines. The total number of stars formed during the simulations increases by a factor of 1.5-2 with magnetic fields. The main component of the IMF has a lognormal shape, with its peak shifted to sub-solar (< 0.3 M_sun) masses in the presence of magnetic fields, due to a decrease in the accretion rates from the gas reservoir. In addition, we see a top-heavy, nearly flat IMF above ~2 solar masses, from regions that were supported by magnetic pressure until high masses are reached. We also consider the effects of X-ray irradiation if the central black hole is active. X-ray feedback inhibits the formation of sub-solar masses and decreases the SFEs even further. Thus, the second contribution is no longer visible. We conclude that magnetic fields potentially change the SFE and the IMF both in active and inactive galaxies, and need to be taken into account in such calculations.

arXiv comment10 pages, 10 figures. Accepted for publication in Astronomy and Astrophysics. 2 more references added

References in corpus (47)

• Galactic Stellar and Substellar Initial Mass Function
• The Initial Mass Function of Stars: Evidence for Uniformity in Variable Systems
• A Substantial Population of Low Mass Stars in Luminous Elliptical Galaxies
• The Universality of Turbulence in Galactic Molecular Clouds
• Diagnostics of irradiated gas in galaxy nuclei. I: A Far-ultraviolet and X-ray dominated region code
• Modeling Collapse and Accretion in Turbulent Gas Clouds: Implementation and Comparison of Sink Particles in AMR and SPH
• Burgers Turbulence
• Diagnostics of irradiated dense gas in galaxy nuclei. II. A grid of XDR and PDR models
• Outflow Feedback Regulated Massive Star Formation in Parsec-Scale Cluster Forming Clumps
• Black hole accretion and star formation as drivers of gas excitation and chemistry in Mrk231
• Extensible Component Based Architecture for FLASH, A Massively Parallel, Multiphysics Simulation Code
• Embedding Lagrangian Sink Particles in Eulerian Grids
• Mach Number Dependence of Turbulent Magnetic Field Amplification: Solenoidal versus Compressive Flows
• Clump morphology and evolution in MHD simulations of molecular cloud formation
• Magnetically Regulated Star Formation in 3D: The Case of Taurus Molecular Cloud Complex
• Collapse, outflows and fragmentation of massive, turbulent and magnetized prestellar barotropic cores
• Small-scale dynamo action during the formation of the first stars and galaxies. I. The ideal MHD limit
• The effect of magnetic fields on star cluster formation
• Star Formation in Extreme Environments: The Effects of Cosmic Rays and Mechanical Heating
• Molecular Gas Disk Structures around AGNs
• Hierarchical Fragmentation and Jet-like Outflows in IRDC G28.34+0.06, a Growing Massive Protostar Cluster
• Magnetic fields in barred galaxies. IV. NGC 1097 and NGC 1365
• New OH Zeeman measurements of magnetic field strengths in molecular clouds
• The massive star initial mass function of the Arches cluster
• Magnetic fields during the early stages of massive star formation - I. Accretion and disk evolution
• Comparing Numerical Methods for Isothermal Magnetized Supersonic Turbulence
• Quiescent Cores and the Efficiency of Turbulence-Accelerated, Magnetically Regulated Star Formation
• Extreme Cosmic-Ray-Dominated-Regions: a new paradigm for high star formation density events in the Universe
• The Jeans mass and the origin of the knee in the IMF
• Confirmation of Enhanced Dwarf-sensitive Absorption Features in the Spectra of Massive Elliptical Galaxies: Further Evidence for a Non-universal Initial Mass Function
• Mechanical feedback in the molecular ISM of luminous IR galaxies
• The Origin of the Arches Stellar Cluster Mass Function
• Protostellar Outflow Heating in a Growing Massive Protocluster
• HNC, HCN and CN in Seyfert galaxies
• The Complete Initial Mass Function Down to the Sub-Solar Regime in the Large Magellanic Cloud with Hubble Space Telescope ACS Observations
• The star formation efficiency and its relation to variations in the initial mass function
• On the Detection of High Redshift Black Holes with ALMA through CO and H2 Emission
• Lowering the Characteristic Mass of Cluster Stars by Magnetic Fields and Outflow Feedback
• Probing high-redshift quasars with ALMA. I. Expected observables and potential number of sources
• Dissipation of Magnetic Flux in Primordial Gas Clouds
• The Quintuplet Cluster III. Hertzsprung-Russell diagram and cluster age
• Dissipation of Magnetic Flux in Primordial Star Formation: From Run-away Phase to Mass Accretion Phase
• Probing X-ray irradiation in the nucleus of NGC 1068 with observations of high-J lines of dense gas tracers
• The impact of X-rays on molecular cloud fragmentation and the IMF
• Star formation near an obscured AGN: Variations in the initial mass function
• Magnetic fields in barred galaxies. V. Modelling NGC 1365
• The Embedded Massive Star Forming Region RCW 38

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