Astrophys. J., 865, 47-47 (2018/September-3)
The Mira-based distance to the Galactic Center.
QIN W., NATAF D.M., ZAKAMSKA N., WOOD P.R. and CASAGRANDE L.
Abstract (from CDS):
Mira variables are useful distance indicators, due to their high luminosities and well-defined period-luminosity relation. We select 1863 Miras from SAAO and MACHO observations to examine their use as distance estimators in the Milky Way. We measure a distance to the Galactic center of R0 = 7.9 ± 0.3 kpc, which is in good agreement with other literature values. The uncertainty has two components of ∼0.2 kpc each: the first is from our analysis and predominantly due to interstellar extinction, the second is due to zero-point uncertainties extrinsic to our investigation, such as the distance to the Large Magellanic Cloud (LMC). In an attempt to improve existing period-luminosity calibrations, we use theoretical models of Miras to determine the dependence of the period-luminosity relation on age, metallicity, and helium abundance, under the assumption that Miras trace the bulk stellar population. We find that at a fixed period of logP=2.4, changes in the predicted Ks magnitudes can be approximated by ΔMKs~-0.109(Δ[Fe/H]) + 0.033(Δt/Gyr)+0.021(ΔY/0.01), and these coefficients are nearly independent of period. The expected overestimate in the Galactic center distance from using an LMC-calibrated relation is ∼0.3 kpc. This prediction is not validated by our analysis; a few possible reasons are discussed. We separately show that while the predicted color-color diagrams of solar-neighborhood Miras work well in the near-infrared; though, there are offsets from the model predictions in the optical and mid-infrared.
© 2018. The American Astronomical Society. All rights reserved.
Galaxy: bulge - Galaxy: center - infrared: stars - Magellanic Clouds - stars: AGB and post-AGB - stars: variables: general
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