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2000ApJ...539..732A - Astrophys. J., 539, 732-741 (2000/August-3)

K-band calibration of the red clump luminosity.


Abstract (from CDS):

The average near-infrared (K-band) luminosity of 238 Hipparcos red clump giants is derived and then used to measure the distance to the Galactic center. These Hipparcos red clump giants have been previously employed as I-band standard candles. The advantage of the K-band is a decreased sensitivity to reddening and perhaps a reduced systematic dependence on metallicity. In order to investigate the latter, and also to refer our calibration to a known metallicity zero point, we restrict our sample of red clump calibrators to those with abundances derived from high-resolution spectroscopic data. The mean metallicity of the sample is [Fe/H]=-0.18 dex (σ=0.17 dex). The data are consistent with no correlation between MK and [Fe/H] and only weakly constrain the slope of this relation. The luminosity function of the sample peaks at MK=-1.61±0.03 mag. Next, we assemble published optical and near-infrared photometry for ∼20 red clump giants in a Baade's window field with a mean metallicity of [Fe/H]=-0.17±0.09 dex, which is nearly identical to that of the Hipparcos red clump. Assuming that the average (V-I)0 and (V-K)0 colors of these two red clumps are the same, the extinctions in the Baade's window field are found to be AV=1.56, AI=0.87, and AK=0.15, in agreement with previous estimates. We derive the distance to the Galactic center: (m-M)0=14.58±0.11 mag, or R=8.24±0.42 kpc. The uncertainty in this distance measurement is dominated by the small number of Baade's window red clump giants examined here.

Abstract Copyright:

Journal keyword(s): Cosmology: Distance Scale - Galaxies: Distances and Redshifts - Galaxy: Center - Stars: Hertzsprung-Russell Diagram - Stars: Distances

Simbad objects: 286

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