Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Stellar Populations in Deep Sky Survey

In this study we have separated stars from galaxies via the criterions HLR  2.82 and 17 < i’ < 21, by using MegaCam ug′r′i′z′ photometry in D4 field. We have studied the metal abundance and metallicity gradient of Galactic stellar populations in CFHTLS D4 field. Our mean abundance values, which are derived from the metallicty distribution of 834 distant F and G type stars are -0.72  0.39 dex for the thick disk, -1.35 0.96 dex for stellar halo, and -2.22  0.66 dex for VMP stars, respectively. Metal abundance value, -0.72 dex for the thick disk is in concordance well with the ones of (Trefzger et al. 1989 ; [Fe/H]  -0.60), (Gilmore and Wyse 1985; [Fe/H] = -0.60), (Allende Prieto et al. 2006; [Fe/H] = -0.70) . No vertical abundance gradient for the thick disk at the distance of z =[2.5, 6.5] kpc is detected.

Derived abundance value -1.35 dex for stellar halo is in agreement well with the one of(Allende Prieto et al. 2006; [Fe/H] = -1.40). There does not exist any change in mean metal abundance for inner halo, z = [4, 8.5] kpc. A metallicity peak around -2.22 dex for VMP stars is in good agreement with the -2.2 dex, given by Carollo et al. (2007) from the spectroscopic and kinematic data of SDSS DR5.

The two mean metal abundances -1.35 dex (inner halo) and -2.2 dex (outer halo) support an idea that halo is two broadly overlapping structural components - inner and outer halo.

As can be seen from Figure 4.13, which shows the relation of [Fe/H]- (g′-r′) in terms of age, three stars with the values of (1.55  [Fe/H]  -1.95 ; < 11 Gyr; (g′-r′) < 0.2; z  14 - 17 kpc) may be accreted via the collisional processes between dwarf galaxies such as Sagittarius, Carina and our Galaxy ( Searle ve Zinn 1978). Only one star with (g′-r < 0.2; [Fe/H] = -0.73 ; < 6 Gyr; z  22 kpc) may be Blue Straggler candidate, according to the work of Carney et al 1994.
ÖNAL Özgecan
Danışman : Doç. Dr. A. Talât SAYGAÇ

Anabilim Dalı : Astronomi ve Uzay Bilimleri

Mezuniyet Yılı : 2008

Tez Savunma Jürisi : Doç.Dr.A.Talat SAYGAÇ (Danışman)

Prof. Dr. Şehsuvar ZEBİTAY

Prof. Dr. Türker ÖZKAN

Doç Dr. A. Talât SAYGAÇ

Doç Dr. Serap Güngör AK

Doç Dr. Ersin GÖĞÜŞ