TY - JOUR
T1 - The Mira-based Distance to the Galactic Center
AU - Qin, Wenzer
AU - Nataf, David M.
AU - Zakamska, Nadia
AU - Wood, Peter R.
AU - Casagrande, Luca
N1 - Publisher Copyright:
© 2018. The American Astronomical Society. All rights reserved.
PY - 2018/9/20
Y1 - 2018/9/20
N2 - 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 R 0 = 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 log P = 2.4, changes in the predicted K s 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.
AB - 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 R 0 = 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 log P = 2.4, changes in the predicted K s 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.
KW - Galaxy: bulge
KW - Galaxy: center
KW - Magellanic Clouds
KW - infrared: stars
KW - stars: AGB and post-AGB
KW - stars: variables: general
UR - http://www.scopus.com/inward/record.url?scp=85053880786&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/aad7fb
DO - 10.3847/1538-4357/aad7fb
M3 - Article
SN - 0004-637X
VL - 865
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 47
ER -