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

Karaali S., Gokce E., Bilir S., Guctekin S. T.

PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF AUSTRALIA, vol.31, 2014 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 31
  • Publication Date: 2014
  • Doi Number: 10.1017/pasa.2014.26
  • Journal Name: PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF AUSTRALIA
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Keywords: globular clusters: individual (M5, M13, M92, 47 Tuc), (Galaxy:) open clusters: individual (M67, NGC 2158, NGC 2420, NGC 6791), (stars:) dwarfs, stars: general, stars: late-type, techniques: photometric (Galaxy:), WIYN OPEN CLUSTER, PHOTOMETRIC PARALLAX ESTIMATION, DIGITAL SKY SURVEY, GLOBULAR-CLUSTERS, STELLAR POPULATION, LOCAL SUBDWARFS, STAR COUNTS, MILKY-WAY, RR-LYRAE, DISTANCES
  • Istanbul University Affiliated: Yes

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 <= (g - r)(0) <= 1.25 mag and it covers the metallicity interval -2.15 <= [Fe/H] <= +0.37 dcx. The absolute magnitude residuals obtained by the application of the procedure to another set of Galactic clusters lie in the interval -0.15 <= Delta M-g <= +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 <= (V - J)(0) <= 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 <= [Fe/H] <= +0.35 dex, field stars lie in the interval -0.29 and +0.35 mag. However, the range of 87% of them is rather shorter, -0.20 <= Delta M-J <= +0.20 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.