Wavelength (å)
نویسندگان
چکیده
We present near-infrared (observed frame) spectra of the high-redshift quasar S4 0636+68 at z = 3.2 which was previously thought to be one of a group of “strong” Fe II emitters (i.e., F (Fe IIλλ4434–4684)/F (Hβ) > 1). Our K-band spectrum clearly shows emission lines of Hβ and [O III]λλ4959, 5007 as well as optical Fe II emission. Our computed value of F (Fe II λλ4434–4684)/F (Hβ) ≃ 0.8 for S4 0636+68 is less than previously thought, and in fact is comparable to values found for radio-loud, flat-spectrum, low-z quasars. Therefore S4 0636+68 appears not to be a strong optical Fe II emitter. Although more than half (5/8) of the high-z quasars observed to date are still classified as strong optical Fe II emitters, their Fe II/Hβ ratios, for the most part, follow the same trend as that of low-z quasars, i.e., an anticorrelation in EW (Fe II)/EW (Hβ) versus EW ([O III])/EW (Hβ), with radio-loud quasars having a mean value of EW (Fe II)/EW (Hβ) approximately half that of radio-quiet quasars at comparable values of EW ([O III])/EW (Hβ). Visiting Astronomer of the University of Hawaii 2.2 meter telescope.
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