MgII Absorption Lines in z=2.974 Damped Lyman-alpha System toward Gravitationally Lensed QSO APM 08279+5255: Detection of Small-scale Structure in MgII Absorbing Clouds

摘要: 1.02-1.16 micron spectra (R ~ 7,000) of the gravitationally lensed QSO APM 08279+5255 at z_em=3.911 were obtained during commissioning run IRCS, 1-5 near-infrared camera and spectrograph for Subaru 8.2 m Telescope. Strong MgII doublet 2976,2800 angstrom FeII (2600 angstrom), (2587 angstrom) absorption lines z_abs=2.974 clearly detected in rest-frame UV spectra, confirming presence a damped Lyman-alpha system redshift as suggested by Petitjean et al. Also MgI (2853 line is probably detected. An analysis including velocity decomposition was performed. This first detailed study high (z > 2.5) where shifts into observer's frame. The pair A B with 0.38 arcsec separation resolved some exposure frames under excellent seeing condition. We extracted separately. Although three components (v -28, +5, +45 km/s) are known to exist this (Petitjean al.), v km/s not toward source B, showing that cloud lies only sight A. Our results suggests size absorbing clouds small 200 pc, which corresponds absorber. direct detection small-scale structure high-redshift, estimated sizes from photoionization model Churchill Charlton.