# The properties of the first galaxies in the BLUETIDES simulation

## TL;DR

This study uses the BLUETIDES simulation to predict properties of early galaxies during reionisation, matching observational data and revealing insights into star formation, dust attenuation, and black hole activity at high redshift.

## Contribution

First large-scale hydrodynamical simulation to predict detailed properties of galaxies during reionisation, aligning with observations and exploring black hole contributions.

## Key findings

- Galaxy population matches observed stellar mass and UV luminosity functions.
- Star formation rates increase rapidly and are largely independent of stellar mass.
- Active SMBHs contribute around 3% to galaxy UV luminosities on average.

## Abstract

We employ the very large cosmological hydrodynamical simulation BLUETIDES to investigate the predicted properties of the galaxy population during the epoch of reionisation ($z>8$). BLUETIDES has a resolution and volume ($(400/h\approx 577)^{3}\,{\rm cMpc^3}$) providing a population of galaxies which is well matched to depth and area of current observational surveys targeting the high-redshift Universe. At $z=8$ BLUETIDES includes almost 160,000 galaxies with stellar masses $>10^{8}\,{\rm M_{\odot}}$. The population of galaxies predicted by BLUETIDES closely matches observational constraints on both the galaxy stellar mass function and far-UV ($150\,{\rm nm}$) luminosity function. Galaxies in BLUETIDES are characterised by rapidly increasing star formation histories. Specific star formation rates decrease with redshift though remain largely insensitive to stellar mass. As a result of the enhanced surface density of metals more massive galaxies are predicted to have higher dust attenuation resulting in a significant steepening of the observed far-UV luminosity function at high luminosities. The contribution of active SMBHs to the UV luminosities of galaxies with stellar masses $10^{9-10}\,{\rm M_{\odot}}$ is around $3\%$ on average. Approximately $25\%$ of galaxies with $M_{*}\approx 10^{10}\,{\rm M_{\odot}}$ are predicted to have active SMBH which contribute $>10\%$ of the total UV luminosity.