中国科学院研究生院博士学位论文 - BATC home page

ivM31for M31 GCs. Using the photometry from the Revised Bologna Catalogue (RBC),we derived the reddening values of 443 GCs, and 209 metallicities of individualclusters without spectroscopy based on the color-metallicity relations and thereddening-free parameters. Combining the spectroscopic metallicities from thereferences with our color-derived metallcities, we obtained the largest metallicitycatalogue of M31 GCs. The results imply that (1) The metallicity distributionis bimodal with peaks at [Fe/H] ≈ −1.6 and −0.6 dex, although it is not assignificant as that in the Milky Way; (2) The spatial distributions show that themetal-rich GCs appear to be more centrally concentrated than the metal-poorones; (3) The V 0 ∼ [Fe/H] shows that the self-enrichment effect can be ignored inthe formations of GCs in M31; (4)The mean reddening is E(B − V ) = 0.28 +0.23−0.14for our sample GCs, and the northwestern side of the M31 disk is nearer to us.(IV). We present the photometry of 30 GCs and GC candidates, whichnearly do not have any photometry in RBC V.3.5, in BATC 15 intermediatebandfilters. Combining the broadband photometry in RBC V.3.5 with our newphotometry, we investigated the color distributions, luminosity functions, color– color diagrams, color magnitude diagrams of GCs and GC candidates in M31.For the first time, we discovered the “blue-tilt” of M31 in I ∼ (B − I) diagramswith a high confidence at 99.95% or 3.47σ for confirmed GCs, and > 99.99% or4.87σ for all the GCs and GC candidates.Keywords:– MetallicityGalaxies: evolution–Andromeda (M31) – Globular Clusters – Age