HR 1614 is not a dissolving cluster. (arXiv:2005.05054v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kushniruk_I/0/1/0/all/0/1">Iryna Kushniruk</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bensby_T/0/1/0/all/0/1">Thomas Bensby</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Feltzing_S/0/1/0/all/0/1">Sofia Feltzing</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sahlholdt_C/0/1/0/all/0/1">Christian L. Sahlholdt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Feuillet_D/0/1/0/all/0/1">Diane Feuillet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Casagrande_L/0/1/0/all/0/1">Luca Casagrande</a>
The HR 1614 overdensity in velocity space and has for a long time been known
as an old (~2 Gyr) and metal-rich ([Fe/H]~0.2) nearby moving group that has a
dissolving cluster origin. The existence of such old and metal-rich groups in
the solar vicinity is quite unexpected since the vast majority of nearby moving
groups are known to be young. In the light of new and significantly larger data
sets we aim to re-investigate the properties and origin of the HR 1614 moving
group.
To identify and characterise the HR 1614 moving group we use astrometric data
from Gaia DR2; distances, extinction, and reddening corrections from the
StarHorse code; elemental abundances from the GALAH and APOGEE spectroscopic
surveys; and photometric metallicities from the SkyMapper survey. Bayesian ages
were estimated for the SkyMapper stars. Since the Hercules stream is the
closest kinematical structure to the HR 1614 moving group in velocity space, we
use it for comparison purposes. Stars that are likely to be members of the two
groups were selected based on their space velocities.
The HR 1614 moving group is located mainly at negative U velocities, does not
form an arch of constant energy in the U-V space and is tilted in V. The
overdensity is not chemically homogeneous but that its stars exist at a wide
range of both metallicities, ages, and elemental abundance ratios. They are
essentially similar to what is observed in the Galactic thin and thick disks, a
younger population (~3 Gyr) that is metal-rich (-0.2<[Fe/H]<0.4) and
alpha-poor. It should therefore not be considered as a dissolving open cluster,
or an accreted population. We suggest that HR 1614 has a complex origin that
could be explained by combining several different mechanisms such as resonances
with the Galactic bar and spiral structure, phase-mixing of dissolving spiral
structure, and phase-mixing due to an external perturbation.
The HR 1614 overdensity in velocity space and has for a long time been known
as an old (~2 Gyr) and metal-rich ([Fe/H]~0.2) nearby moving group that has a
dissolving cluster origin. The existence of such old and metal-rich groups in
the solar vicinity is quite unexpected since the vast majority of nearby moving
groups are known to be young. In the light of new and significantly larger data
sets we aim to re-investigate the properties and origin of the HR 1614 moving
group.
To identify and characterise the HR 1614 moving group we use astrometric data
from Gaia DR2; distances, extinction, and reddening corrections from the
StarHorse code; elemental abundances from the GALAH and APOGEE spectroscopic
surveys; and photometric metallicities from the SkyMapper survey. Bayesian ages
were estimated for the SkyMapper stars. Since the Hercules stream is the
closest kinematical structure to the HR 1614 moving group in velocity space, we
use it for comparison purposes. Stars that are likely to be members of the two
groups were selected based on their space velocities.
The HR 1614 moving group is located mainly at negative U velocities, does not
form an arch of constant energy in the U-V space and is tilted in V. The
overdensity is not chemically homogeneous but that its stars exist at a wide
range of both metallicities, ages, and elemental abundance ratios. They are
essentially similar to what is observed in the Galactic thin and thick disks, a
younger population (~3 Gyr) that is metal-rich (-0.2<[Fe/H]<0.4) and
alpha-poor. It should therefore not be considered as a dissolving open cluster,
or an accreted population. We suggest that HR 1614 has a complex origin that
could be explained by combining several different mechanisms such as resonances
with the Galactic bar and spiral structure, phase-mixing of dissolving spiral
structure, and phase-mixing due to an external perturbation.
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