Preprint
The Mira-based distance to the Galactic centre
arXiv.org
Cornell University
08/03/2018
DOI: 10.48550/arxiv.1808.01294
Abstract
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 centre 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 centre 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-neighbourhood Miras work well in the near-infrared, though there are offsets from the model predictions in the optical and mid-infrared.
Details
- Title: Subtitle
- The Mira-based distance to the Galactic centre
- Creators
- Wenzer QinDavid M NatafNadia ZakamskaPeter R WoodLuca Casagrande
- Resource Type
- Preprint
- Publication Details
- arXiv.org
- DOI
- 10.48550/arxiv.1808.01294
- eISSN
- 2331-8422
- Publisher
- Cornell University; Ithaca, New York
- Language
- English
- Date posted
- 08/03/2018
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984701810602771
Metrics
17 Record Views