Quasar Elemental Abundances at High Redshifts

Abstract

We examine rest-frame ultraviolet spectra of 70 high-redshift quasars (z ! 3:5) to study the chemical enrichment history of the gas closely related to the quasars and thereby estimate the epoch of first star formation. The fluxes of several ultraviolet emission lines were investigated within the framework of the most recent photoionization models to estimate the metallicity of the gas associated with the high-redshift quasars. Standard photoionization parameters and the assumption of secondary nitrogen enrichment indicate an average abundance of Z=Z ' 4-5 in the line-emitting gas. Assuming a timescale of evol ' 0:5 0:8 Gyr for the chemical enrichment of the gas, the first major star formation for quasars with z ' 4 should have started at a redshift of z f ' 6 8, corresponding to an age of the universe of several times 10 8 yr (H 0 ¼ 65 km s À1 Mpc À1 , M ¼ 0:3, Ã ¼ 0:7). We note that this also appears to be the era of reionization of the universe. Finally, there is some evidence for a positive luminosity-metallicity relation in this high-redshift quasar sample.

Testing Models of Radio Galaxy Evolution and the Cosmological Impact of FR II Radio Galaxies

“…Similar conclusions were drawn from different lines of argument by Kronberg et al (2001) and Furlanetto & Loeb (2001). These radio sources born during the quasar era could also have contributed toward metal enhancement of their environments (GKW03b; GWB04), since observations (e.g., Dietrich et al 2003;Schaye et al 2003;Aguirre et al 2004;Shapley et al 2004;Pieri et al 2006;Prochaska et al 2006;Tripp et al 2006) require an efficient mechanism for spreading metals widely at early cosmic epochs.…”

Tracing Outflows in High-Redshift Quasars

“…Smaller velocity shifts and broader lines are more likely to be associated directly with the quasar as outflows, but we see no strong trend in metallicity with velocity shift or line width. We find a broad range in AAL metallicity, from only ∼ 0.01 solar up to ∼ 10 times solar, consistent with previous supersolar results ( Nagao et al 2006;Dietrich et al 2003). One z ∼ 3.5 quasar has AALs that are supersolar in seven out of nine systems (see Simon & Hamann 2010).…”

Abundance anomalies in tidal disruption events

“…These are low enough compared to the estimated TDE rate for evolved stars in Kochanek (2015) that there seems no difficulty in creating the nitrogen rich quasars using the very long lived TDE's associated with the larger evolved stars. A more general puzzle about abundances inferred from quasar BLRs is that they appear to require very high metallicities, Z > ∼ 5Z⊙ (e.g., Dietrich et al 2003, Nagao et al 2006. It is somewhat challenging to reach these metallicities with global star formation models (e.g., Hamann & Ferland 1993, Friaca & Terlevich 1998, Romano et al 2002, leading to an alternative picture of star formation associated with the outer, self-gravitating parts of the accretion flow (e.g., Collin & Zahn 1999, Wang et al 2011.…”