Physical Processes in Star Formation

Abstract

Star formation is a complex multi-scale phenomenon that is of significant importance for astrophysics in general. Stars and star formation are key pillars in observational astronomy from local star forming regions in the Milky Way up to high-redshift galaxies. From a theoretical perspective, star formation and feedback processes (radiation, winds, and supernovae) play a pivotal role in advancing our understanding of the physical processes at work, both individually and of their interactions. In this review we will give an overview of the main processes that are important for the understanding of star formation. We start with an observationally motivated view on star formation from a global perspective and outline the general paradigm of the life-cycle of molecular clouds, in which star formation is the key process to close the cycle. After that we focus on the thermal and chemical aspects in star forming regions, discuss turbulence and magnetic fields as well as gravitational forces. Finally, we review the most important stellar feedback mechanisms.

86 pages, 4 figures. To appear in Space Science Reviews, topical collection Star formation

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• Efficiently Cooled Stellar Wind Bubbles in Turbulent Clouds I. Fractal Theory and Application to Star-Forming Clouds
• JADES: Detecting [OIII]$\lambda 4363$ Emitters and Testing Strong Line Calibrations in the High-$z$ Universe with Ultra-deep JWST/NIRSpec Spectroscopy up to $z\sim 9.5$
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• From diffuse gas to dense molecular cloud cores
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• Photochemistry and Heating/Cooling of the Multiphase Interstellar Medium with UV Radiative Transfer for Magnetohydrodynamic Simulations
• PHANGS-JWST First Results: Rapid Evolution of Star Formation in the Central Molecular Gas Ring of NGC1365
• Simulations of cosmic ray propagation
• Massive star cluster formation I. High star formation efficiency while resolving feedback of individual stars
• Effects of initial density profiles on massive star cluster formation in giant molecular clouds
• The Simons Observatory: Galactic Science Goals and Forecasts
• The in situ formation of molecular and warm ionised gas triggered by hot outflows
• Gravity Versus Magnetic Fields in Forming Molecular Clouds
• Atomic and molecular gas from the epoch of reionization down to redshift 2
• Early-Forming Massive Stars Suppress Star Formation and Hierarchical Cluster Assembly
• Alignment of the magnetic field in star forming regions and why it might be difficult to observe
• Magnetic Field Orientation in Self-Gravitating Turbulent Molecular Clouds
• Quantifying the energy balance between the turbulent ionised gas and young stars
• Constraining the cosmic-ray ionization rate and their spectrum with NIR spectroscopy of dense clouds -- A test-bed for JWST
• Monotonicity of the cores of massive stars
• HI-to-H${}_2$ Transitions in Dust-Free Interstellar Gas
• PHANGS-MeerKAT and MHONGOOSE HI observations of nearby spiral galaxies: physical drivers of the molecular gas fraction, $R_{\mathrm{mol}}$
• On the maximum accretion rate of supermassive stars
• Unravelling the structure of magnetised molecular clouds with SILCC-Zoom: sheets, filaments and fragmentation
• A comparison of the Milky Way's recent star formation revealed by dust thermal emission and high-mass stars
• On the distribution of the Cold Neutral Medium in galaxy discs
• The Energy and Dynamics of Trapped Radiative Feedback with Stellar Winds
• Gravitational Fragmentation of Extremely Metal-poor Circumstellar Discs
• The CO universe: Modelling CO emission and H${}_2$ abundance in cosmological galaxy formation simulations
• Effects of stellar feedback on cores in STARFORGE
• HI Self-absorption toward the Cygnus X North: From Atomic Filament to Molecular Filament
• Escaping the maze: a statistical sub-grid model for cloud-scale density structures in the interstellar medium
• Dust-Evacuated Zones Near Massive Stars: Consequences of Dust Dynamics on Star-forming Regions
• Reconciling extragalactic star formation efficiencies with theory: insights from PHANGS
• Dynamic role of dust in formation of molecular clouds
• ALMAGAL VI. The spatial distribution of dense cores during the evolution of cluster-forming massive clump
• Gradient dynamics approach to reactive thin-film hydrodynamics
• The BLAST Observatory: A Sensitivity Study for Far-IR Balloon-borne Polarimeters
• A Global Census of Metals in the Universe
• The role of shocks and the velocity gradient in the relative orientation of the magnetic field and dense gas clouds
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• Measuring Young Stars in Space and Time -- I. The Photometric Catalog and Extinction Properties of N44
• The Drag Instability in a 2D Isothermal C-shock
• Revealing the drag instability in one-fluid nonideal MHD simulations of a 1D isothermal C-shock
• The Cygnus Allscale Survey of Chemistry and Dynamical Environments: CASCADE III. The large scale distribution of DCO+, DNC and DCN in the DR21 filament
• Transferring Data from a Voronoi Mesh to an Adaptive Cartesian Grid in Pursuit of Self-consistent Top-down Star Formation