Abstract
We present measurements of ultraviolet Fe II/Mg II emission line ratios
for high redshift quasars (z ⪉ 5) in order to estimate the beginning
of intense star formation in the early universe. A detailed comparison
of these quasars at high redshifts to composite spectra of quasars at
the same luminosity but lower redshifts indicates a lack of evolution in
the Fe II/Mg II ratio and, by inference, the Fe/Mg abundance ratio.
Nucleosynthesis and stellar evolution models predict that
α-elements like Mg are produced by massive stars ending in type II
SNe, while Fe is formed predominantly in SNe of type Ia. Guided by the
resulting iron enrichment delay of ˜ 0.3 - 0.6 Gyr, we tentatively
conclude that major star formation activity in the host galaxies of our
high-z quasars must have started at zf ≃ 6 - 9, when
the age of the universe was ˜ 0.5 Gyr (Ho = 72 km
s-1 Mpc-1, ΩM = 0.3,
ΩΛ = 0.7).
| Originalsprog | Engelsk |
|---|---|
| Tidsskrift | Astronomical Society of the Pacific. Conference Proceedings |
| Vol/bind | 311 |
| Sider (fra-til) | 403 |
| ISSN | 1050-3390 |
| Status | Udgivet - 1 jun. 2004 |
| Udgivet eksternt | Ja |