Prospectives of Ground Based Observations

Abstract

The study of FeII emission phenomena in quasars and other extragalactic objects will be revolutionized by the next generation of instruments being planned by ESO. In ten years it will be possible to obtain, for 16-mag objects and in a reasonable observing period, spectra with resolution exceeding λ/Δλ = 5 x 10³ with signal-to-noise ratios better than 30 throughout the optical/near infrared wavelength region. These spectra, when combined with UV spectra obtained with the Hubble Space Telescope (HST) will permit the detailed examination of FeII emission in the rest frame of selected extragalactic objects from below the Lyman limit to wavelengths longer than 1 µ-meter. It will then be possible to extend the techniques pioneered by H. Netzer and B. and D. Wills (Netzer and Wills, 1983; Wills, Netzer and Wills, 1985) to constrain the acceptable models of the F_e ⁺ region in quasars and active galaxies. The next generation spectra will have sufficient signal-to-noise ratios to identify and measure the strength of key multiplets, such as multiplets 191, 188 and 167 (Jordan, 1986; Wampler, 1985). It will be possible to measure the relative strengths of density dependent multiplets, such as the ratio of multiplet 36 to multiplet 42 (Wampler, 1985).