# Formation of carbon-enhanced metal-poor stars as a consequence of inhomogeneous metal mixing

## TL;DR

This paper proposes a new mechanism for forming carbon-enhanced metal-poor stars based on inhomogeneous metal mixing, where carbon-rich regions cool faster and form stars earlier, explaining observed CEMP stars.

## Contribution

It introduces a novel formation scenario for CEMP stars driven by inhomogeneous metal mixing, differing from previous supernova-based explanations.

## Key findings

- 8% of CEMP-no stars explained by the model
- Inhomogeneous mixing creates conditions for early star formation in carbon-rich gas
- Scenario aligns with observed properties of CEMP stars

## Abstract

We present a novel scenario for the formation of carbon-enhanced metal-poor (CEMP) stars. Carbon enhancement at low stellar metallicities is usually considered a consequence of faint or other exotic supernovae. An analytical estimate of cooling times in low-metallicity gas demonstrates a natural bias, which favours the formation of CEMP stars as a consequence of inhomogeneous metal mixing: carbon-rich gas has a shorter cooling time and can form stars prior to a potential nearby pocket of carbon-normal gas, in which star formation is then suppressed due to energetic photons from the carbon-enhanced protostars. We demonstrate that this scenario provides a natural formation mechanism for CEMP stars from carbon-normal supernovae, if inhomogeneous metal mixing provides carbonicity differences of at least one order of magnitude separated by >10pc. In our fiducial (optimistic) model, 8% (83%) of observed CEMP-no stars ([Ba/Fe]<0) can be explained by this formation channel. This new scenario may change our understanding of the first supernovae and thereby our concept of the first stars. Future 3D simulations are required to assess the likelihood of this mechanism to occur in typical high-redshift galaxies.