High Metal Enrichments in Luminous Quasars

We discuss observations of the broad emission line in luminous intermediate redshift quasars, with emphasis on Q0207 -398. This object has relatively sharp lines, allowing us to deconvolve the profiles into distinct components. In this paper we examine the high ionization region, which we show must be matter-bounded, partially transparent to ionizing radiation. We measure a large N V λ1240/He II λ1640 ratio in Q0207-398, but detailed calculations predict this ratio to be ~1 for standard cloud properties. We show that no choice of incident continuum, ionizing photon flux, density, or even the appeal to nonradiative energy sources, can reproduce the observed N V, C IV, O VI, He II spectrum with solar abundances. The intensity of the N V line is sensitive to the abundance of the gas because the abundance of nitrogen, a secondary element goes up roughly as the square of the metallicity. The lowest metallicity capable of reproducing the N V spectrum in Q0207 - 398 is Z ~ 5 Z☉, consistent with that inferred to exist in the cores of massive galaxies after epochs of rapid star formation. Our final model of the high-ionization emission region is one with many properties similar to those inferred for broad absorption-line QSO absorption-line clouds

The Metallicity of the Redshift 4.16 Quasar BR2248-1242

We estimate the metallicity in the broad emission-line region of the redshift z=4.16 quasar, BR2248-1242, by comparing line ratios involving nitrogen to theoretical predictions. BR2248-1242 has unusually narrow emission lines with large equivalent widths, thus providing a rare opportunity to measure several line-ratio abundance diagnostics. The combined diagnostics indicate a metallicity of ~2 times solar. This result suggests that an episode of vigorous star formation occurred near BR2248-1242 prior to the observed z=4.16 epoch. The time available for this enrichment episode is only ~1.5 Gyr at z=4.16 (for H_{0}=65 km s^-1 Mpc^-1, Omega_{m}=0.3 and Omega_Lambda ~< 1). This evidence for high metallicities and rapid star formation is consistent with the expected early-epoch evolution of dense galactic nuclei.Comment: 8 pages, 3 figures. Prepared in AAStex. Submitted to the Astrophysical Journal Revised version: added 1 referenc

High Metal Enrichments in Luminous Quasars

We discuss observations of the broad emission line in luminous intermediate redshift quasars, with emphasis on Q0207 -398. This object has relatively sharp lines, allowing us to deconvolve the profiles into distinct components. In this paper we examine the high ionization region, which we show must be matter-bounded, partially transparent to ionizing radiation. We measure a large N V λ1240/He II λ1640 ratio in Q0207-398, but detailed calculations predict this ratio to be ~1 for standard cloud properties. We show that no choice of incident continuum, ionizing photon flux, density, or even the appeal to nonradiative energy sources, can reproduce the observed N V, C IV, O VI, He II spectrum with solar abundances. The intensity of the N V line is sensitive to the abundance of the gas because the abundance of nitrogen, a secondary element goes up roughly as the square of the metallicity. The lowest metallicity capable of reproducing the N V spectrum in Q0207 - 398 is Z ~ 5 Z_sun_, consistent with that inferred to exist in the cores of massive galaxies after epochs of rapid star formation. Our final model of the high-ionization emission region is one with many properties similar to those inferred for broad absorption-line QSO absorption-line clouds.Astronom