Color-Magnitude Diagram Constraints on the Metallicities, Ages, and Star Formation History of the Stellar Populations in the Carina Dwarf Spheroidal Galaxy

摘要: Victoria-Regina isochrones for $-0.4 \le$ [alpha/Fe] $\le +0.4$ and a wide range in [Fe/H], along with complementary zero-age horizontal branch (ZAHB) loci, have been applied to the color-magnitude diagram (CMD) of Carina. The color transformations that we used "calibrated" so provide excellent fits $[(B-V)_0,\,M_V]$-diagrams M3 M92, when well supported estimates globular cluster (GC) reddenings metallicities are assumed. adopted distance moduli, both GCs Carina, based on our ZAHB models, which able reproduce old HB component (as as luminosity clump) dwarf spheroidal galaxy quite --- even if it spans [Fe/H] ~ 1.5 dex, provided varies approximately way has derived spectroscopically. Ages here agree reasonably those found previously intermediate-age turnoff stars, period negligible star formation (SF) activity (~ 6-10 Gyr ago). CMD simulations carried out faintest subgiant stars. They indicate clear preference SF lasted several instead short burst, some indication ages decrease increasing [Fe/H]. In general, stellar models assume spectroscopic satisfactory observations, including thin giant though higher oxygen abundances than implied by values would favorable consequences.