The statistical properties of stars at redshift, z=5, compared with the present epoch

Matthew R. Bate

We report the statistical properties of stars and brown dwarfs obtained from three radiation hydrodynamical simulations of star cluster formation with metallicities of 1, 1/10 and 1/100 of the solar value. The star-forming clouds are subjected to cosmic microwave background radiation that is appropriate for star formation at a redshift z=5. The results from the three calculations are compared to each other, and to similar previously published calculations that had levels of background radiation appropriate for present-day (z=0) star formation. Each of the calculations treat dust and gas temperatures separately and include a thermochemical model of the diffuse interstellar medium. We find that whereas the stellar mass distribution is insensitive to the metallicity for present-day star formation, at z=5 the characteristic stellar mass increases with increasing metallicity and the mass distribution has a deficit of brown dwarfs and low-mass stars at solar metallicity compared to the Galactic initial mass function. We also find that the multiplicity of M-dwarfs decreases with increasing metallicity at z=5. These effects are a result of metal-rich gas being unable to cool to as low temperatures at z=5 compared to at z=0 due to the hotter cosmic microwave background radiation, which inhibits fragmentation at high densities.

Refereed Scientific Papers

"The statistical properties of stars at redshift, z=5, compared with the present epoch"
Bate, M. R., 2022, MNRAS, in press. (Or preprint from astro-ph/2211.XXXX)

Tables 3 and 4 that are provided as Additional Supporting Information for the paper can be downloaded as this zip file: Bate2022_Tables3_4.zip (12 kB). These files contain the data necessary to construct Figs. 8 to 15, and to produce Table 2.

The dataset that includes the initial conditions and input files for the 3 SPH calculations, and the dump files that were used to produce Figs. 3 to 7 and the output files that were used to produce Fig.2 and Tables 1, 3 and 4 are available from the University of Exeter's Open Research Exeter (ORE) archive: https://doi.org/10.24378/exe.4324

Animations

Simulations & visualisations by Matthew Bate, University of Exeter unless stated otherwise.

Copyright: The material on this page is the property of Matthew Bate. Movies and images are released under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.

For each of the three calculations, there are 4 movies.
The first uses my typical red-yellow-white colour scheme to visualise the column density through the star-forming cloud.
Movies 2-4 use a black-blue-red-yellow-white colour scheme to visualise the temperature (mass weighted) through the star-forming cloud. Movie 2 gives gas temperature, Movie 3 gives dust temperature, and Movie 4 gives the temperature of the radiation field generated by the protostars.

On large scales, few differences are apparent in the column density animations (the structure is smoother in clouds with lower metallicity due to the generally warmer gas), but the temperature movies differ substantially from one another.

Click on the images to view the animations (in Quicktime format).

Redshift z=5, 1/100 of solar metallicity (1280x720p)


Redshift z=5, 1/10 of solar metallicity (1280x720p)


Redshift z=5, Solar metallicity (1280x720p)

Copyright: The material on this page is the property of Matthew Bate. Movies and images are released under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.