Star formation at high redshift
Abstract
The importance of detailed chemical models to understand low-metallicity star formation is widely recognized, as reflected also in recent investigations. We present here a three-dimensional hydrodynamical simulation for star formation. Our aim is to explore the effect of the metal-line cooling on the thermodynamics of the star-formation process. We explore the effect of changing the metallicity of the gas from to . Furthermore, we explore the implications of using the observational abundance pattern of a CEMP-no star, which have been considered to be the missing second-generation stars. In order to pursue our aim, we modeled the microphysics by employing the public astrochemistry package KROME, using a chemical network which includes sixteen chemical species (H i, H ii, H, He i, He ii, He iii, e, H i, H ii, C i, C ii, O i, O ii, Si i, Si ii, and Si iii). We couple KROME with the fully three-dimensional, smoothed-particle hydrodynamics (SPH) code GRADSPH. With this framework we investigate the collapse of a metal-enhanced cloud, exploring the fragmentation process and the formation of stars. We found that the metallicity has a clear impact on the thermodynamics of the collapse, allowing the cloud to reach the CMB temperature floor for a metallicity , which is in agreement with previous works. Moreover, we found that adopting the abundance pattern given by the Keller star, the thermodynamics behavior is very similar to simulations with a metallicity of , due to the high carbon abundance. As long as only metal line cooling is considered, our results support the metallicity threshold proposed by previous works, which will very likely regulate the first episode of fragmentation and potentially determine the masses of the resulting star clusters. For a complete modeling of the IMF and its evolution, we expect that also dust cooling needs to be taken into account.
- Publication:
-
Boletin de la Asociacion Argentina de Astronomia La Plata Argentina
- Pub Date:
- August 2019
- Bibcode:
- 2019BAAA...61...66F
- Keywords:
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- cosmology: early universe;
- stars: formation;
- stars: carbon;
- stars: Population III;
- stars: abundances