Absolute Magnitude Calibration for Dwarfs Based on the Colour-Magnitude Diagrams of Galactic Clusters

Abstract

We present two absolute magnitude calibrations for dwarfs based on colour-magnitude diagrams of Galactic clusters. The combination of the $M_g$ absolute magnitudes of the dwarf fiducial sequences of the clusters M92, M13, M5, NGC 2420, M67 and NGC 6791 with the corresponding metallicities provides absolute magnitude calibration for a given $(g-r{)}_0$ colour. The calibration is defined in the colour interval $0.25\le (g-r{)}_0\le 1.25$ mag and it covers the metallicity interval $-2.15\le [Fe/H]\le +0.37$ dex. The absolute magnitude residuals obtained by the application of the procedure to another set of Galactic clusters lie in the interval $-0.15\le \Delta M_g\le +0.12$ mag. The mean and standard deviation of the residuals are $<\Delta M_g>=-0.002$ and $\sigma =0.065$ mag, respectively. The calibration of the $M_J$ absolute magnitude in terms of metallicity is carried out by using the fiducial sequences of the clusters M92, M13, 47 Tuc, NGC 2158 and NGC 6791. It is defined in the colour interval $0.90\le (V-J{)}_0\le 1.75$ mag and it covers the same metallicity interval of the $M_g$ calibration. The absolute magnitude residuals obtained by the application of the procedure to the cluster M5 ($[Fe/H]=-1.40$ dex) and 46 solar metallicity, $-0.45\le [Fe/H]\le +0.35$ dex, field stars lie in the interval -0.29 and +0.35 mag. However, the range of 87 per cent of them is rather shorter, $-0.2\le \Delta M_J\le +0.2$ mag. The mean and standard deviation of all residuals are $<\Delta M_J>=0.05$ and $\sigma$=0.13 mag, respectively. The derived relations are applicable to stars older than 4 Gyr for the $M_g$ calibration, and older than 2 Gyr for the $M_J$ calibration. The cited limits are the ages of the youngest calibration clusters in the two systems.

arXiv comment31 pages, including 13 figures and 20 tables, accepted for publication in PASA. arXiv admin note: text overlap with arXiv:1206.2752

References in corpus (20)

• The Sloan Digital Sky Survey: Technical Summary
• Ages of Globular Clusters from Hipparcos Parallaxes of Local Subdwarfs
• Simulation of Stellar Objects in SDSS Color Space
• Starcounts Redivivus. IV. Density Laws Through Photometric Parallaxes
• Younger and brighter - New distances to globular clusters based on Hipparcos parallax measurements of local subdwarfs
• The SEGUE Stellar Parameter Pipeline. IV. Validation with an Extended Sample of Galactic Globular and Open Clusters
• Galactic Globular and Open Clusters in the Sloan Digital Sky Survey. I. Crowded Field Photometry and Cluster Fiducial Sequences in ugriz
• Setting UBVRI Photometric Zero-Points Using Sloan Digital Sky Survey ugriz Magnitudes
• RR Lyrae stars in Galactic globular clusters.III. Pulsational predictions for metal content Z=0.0001 to Z=0.006
• Transformations between 2MASS, SDSS and BVRI photometric systems: bridging the near infrared and optical
• The intermediate-age open cluster NGC 2158
• New colour-transformations for the Sloan photometry and revised metallicity calibration and equations for photometric parallax estimation
• The age of the oldest globular clusters
• Exploring the variable stars in the globular cluster NGC5024 (M53): New RR Lyrae and SX Phoenicis stars
• WIYN Open Cluster Study XI: WIYN 3.5m Deep Photometry of M35 (NGC 2168)
• Lithium Abundances of the Super-Metal-Rich Open Cluster NGC 6253
• Fiducial Stellar Population Sequences for the VJKs Photometric System
• WIYN Open Cluster Study. XIX. Main Sequence Fitting Distances to Open Clusters Using V-K Color-Magnitude Diagrams
• A New Procedure for the Photometric Parallax Estimation
• Absolute Magnitude Calibration for Red Giants based on the Colour-Magnitude Diagrams of Galactic Clusters. I- Calibration with V and (B-V)