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Your search keyword '"Klessen, Ralf S."' showing total 20 results
Start Over Author "Klessen, Ralf S." Publication Type Conference Materials
20 results on '"Klessen, Ralf S."'

1. Invertible Neural Networks in Astrophysics.

Author

Klessen, Ralf S.

Subjects
ARTIFICIAL neural networks, ASTROPHYSICS, MACHINE learning, ASTRONOMICAL photometry, PREDICTION models
Abstract

Modern machine learning techniques have become indispensable in many fields of astronomy and astrophysics. Here we introduce a specific class of methods, invertible neural networks, and discuss two specific applications, the prediction of stellar parameters from photometric observations and the study of stellar feedback processes from on emission lines. [ABSTRACT FROM AUTHOR]

Published
2022
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2. The first generations of stars

Author

Caffau, Elisabetta, primary, Gallagher, Andy, additional, Bonifacio, Piercarlo, additional, Cayrel, Roger, additional, Christlieb, Norbert, additional, Clark, Paul C., additional, Francois, Patrick, additional, Glover, Simon, additional, Klessen, Ralf S., additional, Koch, Andreas, additional, Ludwig, Hans G., additional, Monaco, Lorenzo, additional, Plez, B., additional, Sbordone, Luca, additional, Spite, Monique, additional, Spite, Francois, additional, Steffen, Matthias, additional, and Zaggia, Simone, additional

Published
2015
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7. Black hole feedback on the first galaxies

Author

Jeon, Myoungwon, primary, Pawlik, Andreas H., additional, Greif, Thomas H., additional, Glover, Simon C. O., additional, Bromm, Volker, additional, Milosavljević, Miloš, additional, and Klessen, Ralf S., additional

Published
2012
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20. The First Stellar Cluster.

Author

Clark, Paul C., Glover, Simon C. O., and Klessen, Ralf S.

Subjects
STAR clusters, GALACTIC halos, ASTROPHYSICS, STAR formation, HYDRODYNAMICS, MILKY Way
Abstract

We report results from numerical simulations of star formation in the early universe that focus on gas at very high densities and very low metallicities. We argue that the gas in the central regions of protogalactic halos will fragment as long as it carries sufficient angular momentum. Rotation leads to the build-up of massive disk-like structures which fragment to form protostars. At metallicities Z≈10-5 Z⊙, dust cooling becomes effective and leads to a sudden drop of temperature at densities above n = 1012 cm-3. This induces vigorous fragmentation, leading to a very densely-packed cluster of low-mass stars. This is the first stellar cluster. The mass function of stars peaks below 1 M⊙, similar to what is found in the solar neighborhood, and comparable to the masses of the very-low metallicity subgiant stars recently discovered in the halo of our Milky Way. We find that even purely primordial gas can fragment at densities 1014 cm-3<=n<=1016 cm-3, although the resulting mass function contains only a few objects (at least a factor of ten less than the Z = 10-6 Z⊙. mass function), and is biased towards higher masses. A similar result is found for gas with Z = 10-6 Z⊙. Gas with Z <=10-6 Z⊙ behaves roughly isothermally at these densities (with polytropic exponent γ≈1.06) and the massive disk-like structures that form due to angular momentum conservation will be marginally unstable. As fragmentation is less efficient, we expect stars with Z<=10-6 Z⊙ to be massive, with masses in excess of several tens of solar masses, consistent with the results from previous studies. [ABSTRACT FROM AUTHOR]

Published
2008
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