Formation of carbon-enhanced metal-poor stars as a consequence of inhomogeneous metal mixing. (arXiv:1812.01820v1 [astro-ph.GA])

Formation of carbon-enhanced metal-poor stars as a consequence of inhomogeneous metal mixing. (arXiv:1812.01820v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Hartwig_T/0/1/0/all/0/1">Tilman Hartwig</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yoshida_N/0/1/0/all/0/1">Naoki Yoshida</a>

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, 11% (89%) 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.

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, 11% (89%) 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.

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