Extragalactic Xray Binary Stars Beacons for Stellar and河外星系的X射线双星的恒星和信标.pptVIP

Recent Progress in Understanding X-ray Emission From Early-type Galaxies: The Hot Gas Component Introduction Origin of hot gas and metals in ellipticals - stellar mass loss + accretion of gas during/after formation - metal-enriched by Type Ia/II supernovae Temperature: kT ~ 0.3-1 keV Mass ~ up to 1010 M? Metallicity: ~solar for gas-rich systems Major outstanding problems: LX vs. Lopt relation metallicity of hot gas LX vs. Lopt Relation X-ray Bright vs. X-ray Faint NGC4494: LX,total (ROSAT) - 3 x 1039 ergs s-1 LX,gas (Chandra) - 4 x 1038 ergs s-1 Cause of LX vs. Lopt Dispersion Environmental? ram pressure stripping: LX ? - cluster environment ICM pressure confinement: LX ? “stifling” Internal? - variation in Type Ia supernovae-driven winds - variation in depth of dark matter gravitational potential Low LX/Lopt in low density environments. High and low LX/Lopt in high density environments. (e.g., Brown Bregman 2000) Are We Studying “Typical” Galaxies? Popular targets such as NGC4472, NGC4636, NGC1399, etc., are attractive because of their high X-ray count rates -- but are they typical of elliptical galaxies in general? Of the 34 galaxies in the Brown Bregman (1998) optically- complete sample of elliptical galaxies, over half have their X-ray emission dominated by X-ray binaries. Smaller (fainter) galaxies that failed to make the Brown Bregman (1998) sample are predominantly gas-poor. Metallicity of the Hot Gas: History Initial studies with ASCA led to the “metallicity problem” (Arimoto et al. 1997) : hot gas: ~20% solar, stars: ? solar - spectral codes (Raymond-Smith vs. MEKAL vs. APEC) - calibration - treatment of LMXB