2000/02/04 by Valentin D. Ivanov, V. D. Ivanov, Jordanka Borissova +8
Earth and Planetary Sciences · Physics and Astronomy · #Atmospheric Ozone and Climate #History and Developments in Astronomy #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0002118
22 pages, 5 figures. accepted to AJ; scheduled for May 2000
arxiv created 2000/02/04 · arxiv updated 2009/12/01
Infrared JKs-band photometry of the Galactic globular clusters M15 and, for the first time, M56 is presented. We estimated the reddening (E(B-V)=0.18+/-0.08 mag) and distance modulus ((m-M)V=15.43+/-0.30 mag) towards the poorly studied globular cluster M56. We combined our data with observations of other clusters from the literature (12 in total) to extend the [Fe/H] vs. Red Giant Branch (RGB) slope relation towards metal-poor clusters. Our best fit yields to [Fe/H]=-3.40(+/-0.22)-27.74(+/-2.35)x(RGB Slope), with an r.m.s.=0.20. The broader metallicity baseline greatly reduced the uncertainties compared to other existing calibrations. We confirmed a previously obtained calibration of the relation between the RGB color (J-Ks)0(RGB) at MKs=-5.5 vs. [Fe/H]: [Fe/H]=-6.90(+/-0.99)+6.63(+/-1.05)x(J-Ks)0(RGB) with an r.m.s.=0.33. Finally, using the new RGB slope calibration we estimated the abundance of the super metal-rich cluster Liller 1 [Fe/H]=+0.34+/-0.22.