Revisiting long-standing puzzles of the Milky Way: the Sun and its vicinity as typical outer disk chemical evolution. (arXiv:1903.03188v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Haywood_M/0/1/0/all/0/1">M. Haywood</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Snaith_O/0/1/0/all/0/1">O. N. Snaith</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lehnert_M/0/1/0/all/0/1">M. D. Lehnert</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Matteo_P/0/1/0/all/0/1">P. Di Matteo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Khoperskov_S/0/1/0/all/0/1">S. Khoperskov</a>
We present a scenario of the chemical enrichment of the solar neighborhood
that solves the G-dwarf problem by taking into account constraints on a larger
scale. We argue that the Milky Way disk within 10 kpc has been enriched to
solar metallicity by a massive stellar population: the thick disk, which itself
formed from a massive turbulent gaseous disk. The key new consideration is that
the pre-enrichment provided by the thick disk is not related to the mass
fraction of this stellar population at the solar radius, as is classically
assumed in inside-out scenarios, but is actually related to the formation of
the entire massive thick disk, due to the vigorous gas phase mixing that
occurred during its formation. Hence, the fact that this population represents
only 15-25% of the local stellar surface density today is irrelevant for
`solving’ the G-dwarf problem. The only condition for this scenario to work is
that the thick disk was formed from a turbulent gaseous disk that permitted a
homogeneous — not radially dependent — distribution of metals, allowing the
solar ring to be enriched to solar metallicity. At the solar radius, the gas
flowing from the outer disk combined with the solar metallicity gas left over
from thick disk formation, providing the fuel necessary to form the thin disk
at the correct metallicity to solve the G-dwarf problem. Chemical evolution at
R$>$6 kpc, and in particular beyond the solar radius, can be reproduced with
the same scheme. These results imply that the local metallicity distribution is
not connected to the gas accretion history of the Milky Way. Finally, we argue
that the Sun is the result of the evolution typical of stars in the disk beyond
$sim$6 kpc (i.e., also undergoing dilution), and has none of the
characteristics of inner disk stars. [Abridged]
We present a scenario of the chemical enrichment of the solar neighborhood
that solves the G-dwarf problem by taking into account constraints on a larger
scale. We argue that the Milky Way disk within 10 kpc has been enriched to
solar metallicity by a massive stellar population: the thick disk, which itself
formed from a massive turbulent gaseous disk. The key new consideration is that
the pre-enrichment provided by the thick disk is not related to the mass
fraction of this stellar population at the solar radius, as is classically
assumed in inside-out scenarios, but is actually related to the formation of
the entire massive thick disk, due to the vigorous gas phase mixing that
occurred during its formation. Hence, the fact that this population represents
only 15-25% of the local stellar surface density today is irrelevant for
`solving’ the G-dwarf problem. The only condition for this scenario to work is
that the thick disk was formed from a turbulent gaseous disk that permitted a
homogeneous — not radially dependent — distribution of metals, allowing the
solar ring to be enriched to solar metallicity. At the solar radius, the gas
flowing from the outer disk combined with the solar metallicity gas left over
from thick disk formation, providing the fuel necessary to form the thin disk
at the correct metallicity to solve the G-dwarf problem. Chemical evolution at
R$>$6 kpc, and in particular beyond the solar radius, can be reproduced with
the same scheme. These results imply that the local metallicity distribution is
not connected to the gas accretion history of the Milky Way. Finally, we argue
that the Sun is the result of the evolution typical of stars in the disk beyond
$sim$6 kpc (i.e., also undergoing dilution), and has none of the
characteristics of inner disk stars. [Abridged]
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