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69. Physical Processes in Star Formation

Author

Girichidis, Philipp, primary, Offner, Stella S. R., additional, Kritsuk, Alexei G., additional, Klessen, Ralf S., additional, Hennebelle, Patrick, additional, Kruijssen, J. M. Diederik, additional, Krause, Martin G. H., additional, Glover, Simon C. O., additional, and Padovani, Marco, additional

Published
2020
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70. The Physics of Star Cluster Formation and Evolution

Author

Krause, Martin G. H., primary, Offner, Stella S. R., additional, Charbonnel, Corinne, additional, Gieles, Mark, additional, Klessen, Ralf S., additional, Vázquez-Semadeni, Enrique, additional, Ballesteros-Paredes, Javier, additional, Girichidis, Philipp, additional, Diederik Kruijssen, J. M., additional, Ward, Jacob L., additional, and Zinnecker, Hans, additional

Published
2020
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71. Impact of Low-Energy Cosmic Rays on Star Formation

Author

Padovani, Marco, primary, Ivlev, Alexei V., additional, Galli, Daniele, additional, Offner, Stella S. R., additional, Indriolo, Nick, additional, Rodgers-Lee, Donna, additional, Marcowith, Alexandre, additional, Girichidis, Philipp, additional, Bykov, Andrei M., additional, and Kruijssen, J. M. Diederik, additional

Published
2020
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73. Cosmic Ray Electrons in Galaxy Formation

Author

Winner, Georg, Pfrommer, Christoph, and Girichidis, Philipp

Subjects
Hardware_MEMORYSTRUCTURES, MHD, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Cosmology and Extragalactic Astrophysics, shock waves, radiation mechanisms: non-thermal, Computer Science::Digital Libraries, methods: numerical, Computer Science::Graphics, cosmic rays, Hardware_GENERAL, ComputingMilieux_MISCELLANEOUS, Astrophysics::Galaxy Astrophysics, acceleration of particles
Abstract

Poster contribution for the conference "New Perspectives on Galactic Magnetism", {"references":["Caprioli, D and Spitkovsky, A , 2014 ApJ, 783, 91","Pfrommer, C. et al., 2017, MNRAS, 465, 4500","Riquelme, M. A. and Spitkovsky, A., 2011, ApJ, 733, 63","Sarazin, C., 1999, ApJ, 520, 529","Selig, M. et al., 2015, A&A, 581, A126","Springel, V., 2010, MNRAS, 401, 791","Winner, G. et al., arXiv:1903.01467"]}

Published
2019
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77. Spectrally resolved cosmic ray hydrodynamics – I. Spectral scheme.

Author

Girichidis, Philipp, Pfrommer, Christoph, Hanasz, Michał, and Naab, Thorsten

Subjects
*PLASMA astrophysics, *MOMENTUM distributions, *FOKKER-Planck equation, *HYDRODYNAMICS, *DISTRIBUTION (Probability theory), *COSMIC rays, *MOMENTUM transfer
Abstract

Cosmic ray (CR) protons are an important component in many astrophysical systems. Processes like CR injection, cooling, adiabatic changes as well as active CR transport through the medium strongly modify the CR momentum distribution and have to be taken into account in hydrodynamical simulations. We present an efficient novel numerical scheme to accurately compute the evolution of the particle distribution function by solving the Fokker–Planck equation with a low number of spectral bins (10–20), which is required to include a full spectrum for every computational fluid element. The distribution function is represented by piecewise power laws and is not forced to be continuous, which enables an optimal representation of the spectrum. The Fokker–Planck equation is solved with a two-moment approach evolving the CR number and energy density. The low numerical diffusion of the scheme reduces the numerical errors by orders of magnitude in comparison to classical schemes with piecewise constant spectral representations. With this method not only the spectral evolution of CRs can be computed accurately in magnetohydrodynamic simulations but also their dynamical impact as well as CR ionization. This allows for more accurate models for astrophysical plasmas, like the interstellar medium, and direct comparisons with observations. [ABSTRACT FROM AUTHOR]

Published
2020
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84. The SILCC project – III. Regulation of star formation and outflows by stellar winds and supernovae

Author

Gatto, Andrea, primary, Walch, Stefanie, additional, Naab, Thorsten, additional, Girichidis, Philipp, additional, Wünsch, Richard, additional, Glover, Simon C. O., additional, Klessen, Ralf S., additional, Clark, Paul C., additional, Peters, Thomas, additional, Derigs, Dominik, additional, Baczynski, Christian, additional, and Puls, Joachim, additional

Published
2016
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85. The SILCC project – IV. Impact of dissociating and ionizing radiation on the interstellar medium and Hα emission as a tracer of the star formation rate

Author

Peters, Thomas, primary, Naab, Thorsten, additional, Walch, Stefanie, additional, Glover, Simon C. O., additional, Girichidis, Philipp, additional, Pellegrini, Eric, additional, Klessen, Ralf S., additional, Wünsch, Richard, additional, Gatto, Andrea, additional, and Baczynski, Christian, additional

Published
2016
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86. The SILCC (SImulating the LifeCycle of molecular Clouds) project – II. Dynamical evolution of the supernova-driven ISM and the launching of outflows

Author

Girichidis, Philipp, primary, Walch, Stefanie, additional, Naab, Thorsten, additional, Gatto, Andrea, additional, Wünsch, Richard, additional, Glover, Simon C. O., additional, Klessen, Ralf S., additional, Clark, Paul C., additional, Peters, Thomas, additional, Derigs, Dominik, additional, and Baczynski, Christian, additional

Published
2016
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87. LAUNCHING COSMIC-RAY-DRIVEN OUTFLOWS FROM THE MAGNETIZED INTERSTELLAR MEDIUM

Author

Girichidis, Philipp, primary, Naab, Thorsten, additional, Walch, Stefanie, additional, Hanasz, Michał, additional, Low, Mordecai-Mark Mac, additional, Ostriker, Jeremiah P., additional, Gatto, Andrea, additional, Peters, Thomas, additional, Wünsch, Richard, additional, Glover, Simon C. O., additional, Klessen, Ralf S., additional, Clark, Paul C., additional, and Baczynski, Christian, additional

Published
2016
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89. Importance of the initial conditions for star formation

Author

Girichidis, Philipp

Subjects
Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 520 Astronomy and allied sciences, Astrophysics::Galaxy Astrophysics
Abstract

This thesis investigates the impact of the initial conditions on present-day star formation. Using numerical simulations, we follow the gravitational collapse of dense molecular clouds under different initial turbulent motions and initial density distributions. Our analysis focuses on the morphology of the cloud, the time and location of the formation of stars, the energetics during the collapse, the formation of clusters including their internal structure, their accretion behaviour as well as their mass distribution. The morphology of the cloud and the total number of stars are strongly influenced by the initial type of turbulence and the initial density profile. The results range from almost unperturbed cores with a single star to strongly filamentary cores with hundreds of stars in disconnected clusters. The internal structure of protostellar clusters is systematically but not significantly influenced by the initial conditions. Concerning the accretion rates as well as the dynamical interactions of stars within the clusters, we observe a fairly uniform behaviour, not reflecting the large variations in the initial conditions. The simulations presented in this thesis were performed using the grid-based code FLASH, developed mainly at the University of Chicago.

Published
2012
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91. The SILCC project -- IV. Impact of dissociating and ionizing radiation on the interstellar medium and Hα emission as a tracer of the star formation rate.

Author

Peters, Thomas, Naab, Thorsten, Walch, Stefanie, Glover, Simon C. O., Girichidis, Philipp, Pellegrini, Eric, Klessen, Ralf S., Wünsch, Richard, Gatto, Andrea, and Baczynski, Christian

Subjects
IONIZING radiation, STAR formation, INTERSTELLAR medium, STELLAR structure, STELLAR winds
Abstract

We present three-dimensional radiation-hydrodynamical simulations of the impact of stellar winds, photoelectric heating, photodissociating and photoionizing radiation, and supernovae on the chemical composition and star formation in a stratified disc model. This is followed by a sink-based model for star clusters with populations of individual massive stars. Stellar winds and ionizing radiation regulate the star formation rate at a factor of ~10 below the simulation with only supernova feedback due to their immediate impact on the ambient interstellar medium after star formation. Ionizing radiation (with winds and supernovae) significantly reduces the ambient densities for most supernova explosions to ρ < 10-25 g cm-3, compared to 10-23g cm-3 for the model with only winds and supernovae. Radiation from massive stars reduces the amount of molecular hydrogen and increases the neutral hydrogen mass and volume filling fraction. Only this model results in a molecular gas depletion time-scale of 2 Gyr and shows the best agreement with observations. In the radiative models, the Hα emission is dominated by radiative recombination as opposed to collisional excitation (the dominant emission in non-radiative models), which only contributes ~1-10 per cent to the total Hα emission. Individual massive stars (M ≥ 30M☉) with short lifetimes are responsible for significant fluctuations in the Hα luminosities. The corresponding inferred star formation rates can underestimate the true instantaneous star formation rate by a factor of ~10. [ABSTRACT FROM AUTHOR]

Published
2017
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96. Importance of the initial conditions for star formation - II. Fragmentation-induced starvation and accretion shielding.

Author

Girichidis, Philipp, Federrath, Christoph, Banerjee, Robi, and Klessen, Ralf S.

Subjects
*STAR formation, *NUCLEAR fragmentation, *ACCRETION (Astrophysics), *RADIATION shielding, *DENSITY of stars, *MOLECULAR clouds, *SIMULATION methods & models
Abstract

ABSTRACT We investigate the impact of different initial conditions for the initial density profile and the initial turbulence on the formation process of protostellar clusters. We study the collapse of dense molecular cloud cores with three-dimensional adaptive mesh refinement simulations. We focus our discussion on the distribution of the gas among the protostellar objects in the turbulent dynamical cores. Despite the large variations in the initial configurations and the resulting gas and cluster morphology we find that all stellar clusters follow a very similar gas accretion behaviour. Once secondary protostars begin to form, the central region of a cluster is efficiently shielded from further accretion. Hence, objects located close to the centre are starved of material, as indicated by a strong decrease of the central accretion rate. This fragmentation-induced starvation occurs not only in rotationally supported discs and filaments, but also in more spherically symmetric clusters with complex chaotic motions. [ABSTRACT FROM AUTHOR]

Published
2012
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