A High-Precision Trigonometric Parallax to an Ancient Metal-Poor Globular Cluster

Autor:	Brown, T. M., Casertano, S., Strader, J., Riess, A., VandenBerg, D. A., Soderblom, D. R., Kalirai, J., Salinas, R.
Rok vydání:	2018
Předmět:	Astrophysics - Solar and Stellar Astrophysics Astrophysics - Astrophysics of Galaxies Astrophysics - Instrumentation and Methods for Astrophysics
Druh dokumentu:	Working Paper
DOI:	10.3847/2041-8213/aab55a
Popis:	Using the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST), we have obtained a direct trigonometric parallax for the nearest metal-poor globular cluster, NGC 6397. Although trigonometric parallaxes have been previously measured for many nearby open clusters, this is the first parallax for an ancient metal-poor population -- one that is used as a fundamental template in many stellar population studies. This high-precision measurement was enabled by the HST/WFC3 spatial-scanning mode, providing hundreds of astrometric measurements for dozens of stars in the cluster and also for Galactic field stars along the same sightline. We find a parallax of 0.418 +/- 0.013 +/- 0.018 mas (statistical, systematic), corresponding to a true distance modulus of 11.89 +/- 0.07 +/- 0.09 mag (2.39 +/- 0.07 +/- 0.10 kpc). The V luminosity at the stellar main sequence turnoff implies an absolute cluster age of 13.4 +/- 0.7 +/- 1.2 Gyr. Comment: Accepted for publication in The Astrophysical Journal Letters. Version 2 includes minor revisions to proof
Databáze:	arXiv
Externí odkaz:	http://arxiv.org/abs/1803.02927 Zobrazit plný text záznamu View this record from Arxiv