On the Color-Metallicity Relation of the Red Clump and the Reddening Toward the Magellanic Clouds. (arXiv:2006.03603v2 [astro-ph.SR] UPDATED)

On the Color-Metallicity Relation of the Red Clump and the Reddening Toward the Magellanic Clouds. (arXiv:2006.03603v2 [astro-ph.SR] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Nataf_D/0/1/0/all/0/1">David M. Nataf</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cassisi_S/0/1/0/all/0/1">Santi Cassisi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Casagrande_L/0/1/0/all/0/1">Luca Casagrande</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yuan_W/0/1/0/all/0/1">Wenlong Yuan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Riess_A/0/1/0/all/0/1">Adam G. Riess</a>

The zero point of the reddening toward the Large Magellanic Cloud (LMC) has
been the subject of some dispute. Its uncertainty propagates as a systematic
error for methods which measure the extragalactic distance scale through
knowledge of the absolute extinction of LMC stars. In an effort to resolve this
issue, we used three different methods to calibrate the most widely-used metric
to predict LMC extinction, the intrinsic color of the red clump,
$(V-I)_{RC,0}$, for the inner $sim$3 degrees of that galaxy. The first
approach was to empirically calibrate the color zeropoints of the BaSTI
isochrones over a wide metallicity range of ${Delta}rm{[Fe/H]} approx 1.10$
using measurements of red clump stars in 47 Tuc, the Solar Neighborhood, and
NGC 6791.

From these efforts we also measure these properties of the Solar Neighborhood
red clump, ($V-I$, $G_{BP}-K_{s}$, $G-K_{s}$, $G_{RP}-K_{s}$, $J-K_{s}$,
$H-K_{s}$, $M_{I}$, $M_{Ks}$)$_{RC,0} =$ (1.02, 2.75, 2.18, 1.52, 0.64, 0.15,
$-$0.23, $-$1.63). The second and third methods were to compare the observed
colors of the red clump to those of Cepheids and RR Lyrae in the LMC. With
these three methods, we estimated the intrinsic color of the red clump of the
LMC to be $(V-I)_{RC,0,rm{LMC}} = { approx 0.93,0.91 pm 0.02,0.89 pm
0.02}$ respectively, and similarly using the first and third method we
estimated $ (V-I)_{RC,0,rm{SMC}} = {approx 0.85,0.84 pm 0.02 }$
respectively for the Small Magellanic Cloud. We estimate the luminosities to be
$M_{I,RC,rm{LMC}}=-0.26$ and $M_{I,RC,rm{SMC}}=-0.37$. We show that this has
important implications for recent calibrations of the tip of the red giant
branch in the Magellanic Clouds used to measure $H_0$.

The zero point of the reddening toward the Large Magellanic Cloud (LMC) has
been the subject of some dispute. Its uncertainty propagates as a systematic
error for methods which measure the extragalactic distance scale through
knowledge of the absolute extinction of LMC stars. In an effort to resolve this
issue, we used three different methods to calibrate the most widely-used metric
to predict LMC extinction, the intrinsic color of the red clump,
$(V-I)_{RC,0}$, for the inner $sim$3 degrees of that galaxy. The first
approach was to empirically calibrate the color zeropoints of the BaSTI
isochrones over a wide metallicity range of ${Delta}rm{[Fe/H]} approx 1.10$
using measurements of red clump stars in 47 Tuc, the Solar Neighborhood, and
NGC 6791.

From these efforts we also measure these properties of the Solar Neighborhood
red clump, ($V-I$, $G_{BP}-K_{s}$, $G-K_{s}$, $G_{RP}-K_{s}$, $J-K_{s}$,
$H-K_{s}$, $M_{I}$, $M_{Ks}$)$_{RC,0} =$ (1.02, 2.75, 2.18, 1.52, 0.64, 0.15,
$-$0.23, $-$1.63). The second and third methods were to compare the observed
colors of the red clump to those of Cepheids and RR Lyrae in the LMC. With
these three methods, we estimated the intrinsic color of the red clump of the
LMC to be $(V-I)_{RC,0,rm{LMC}} = { approx 0.93,0.91 pm 0.02,0.89 pm
0.02}$ respectively, and similarly using the first and third method we
estimated $ (V-I)_{RC,0,rm{SMC}} = {approx 0.85,0.84 pm 0.02 }$
respectively for the Small Magellanic Cloud. We estimate the luminosities to be
$M_{I,RC,rm{LMC}}=-0.26$ and $M_{I,RC,rm{SMC}}=-0.37$. We show that this has
important implications for recent calibrations of the tip of the red giant
branch in the Magellanic Clouds used to measure $H_0$.

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