Metallicity estimates of young clusters in the Magellanic Clouds from Stromgren photometry of supergiant stars. (arXiv:1812.07911v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Piatti_A/0/1/0/all/0/1">A.E. Piatti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pietrzynski_G/0/1/0/all/0/1">G. Pietrzyński</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Narloch_W/0/1/0/all/0/1">W. Narloch</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gorski_M/0/1/0/all/0/1">M. Górski</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Graczyk_D/0/1/0/all/0/1">D. Graczyk</a>
We present results obtained from Stromgren photometry of 13 young (~30-220
Myr) Magellanic Cloud (MC) clusters, most of them lacking in the literature
from direct metallicity measurements. We derived for them [Fe/H] values from a
high-dispersion spectroscopy-based empirical calibration of the Stromgren
metallicity sensitive index m1 for yellow and red supergiants (SGs). Particular
care was given while estimating their respective uncertainties. In order to
obtain the mean cluster metallicities, we used [Fe/H] values of selected SGs
for which we required to be located within the cluster radii, placed in the
expected SG region in the cluster colour-magnitude diagrams, and with [Fe/H]
values within the FWHM of the observed cluster metallicity distributions. The
resulting metallicities for nearly 75 per cent of the cluster sample agree well
with the most frequently used values of the mean MCs’ present-day
metallicities. The remaining clusters have mean [Fe/H] values that fall near
the edge of the MC present-day metallicity distributions. When comparing the
cluster metallicities with their present positions, we found evidence that
supports the claimed recent interaction of the MCs with the Milky Way, that
could have caused that some clusters were scattered from their birthplaces.
Indeed, we show examples of clusters with metal contents typical of the galaxy
inner regions placed outward them. Likewise, we found young clusters, at
present located in the inner regions of both MCs, formed out of gas that has
remained unmixed since several Gyr ago.
We present results obtained from Stromgren photometry of 13 young (~30-220
Myr) Magellanic Cloud (MC) clusters, most of them lacking in the literature
from direct metallicity measurements. We derived for them [Fe/H] values from a
high-dispersion spectroscopy-based empirical calibration of the Stromgren
metallicity sensitive index m1 for yellow and red supergiants (SGs). Particular
care was given while estimating their respective uncertainties. In order to
obtain the mean cluster metallicities, we used [Fe/H] values of selected SGs
for which we required to be located within the cluster radii, placed in the
expected SG region in the cluster colour-magnitude diagrams, and with [Fe/H]
values within the FWHM of the observed cluster metallicity distributions. The
resulting metallicities for nearly 75 per cent of the cluster sample agree well
with the most frequently used values of the mean MCs’ present-day
metallicities. The remaining clusters have mean [Fe/H] values that fall near
the edge of the MC present-day metallicity distributions. When comparing the
cluster metallicities with their present positions, we found evidence that
supports the claimed recent interaction of the MCs with the Milky Way, that
could have caused that some clusters were scattered from their birthplaces.
Indeed, we show examples of clusters with metal contents typical of the galaxy
inner regions placed outward them. Likewise, we found young clusters, at
present located in the inner regions of both MCs, formed out of gas that has
remained unmixed since several Gyr ago.
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