Elemental Abundances in QSOs: Star Formation and Galactic Nuclear Evolution at High Redshifts

Abstract

Quasar (or QSO) elemental abundances provide unique probes of high-redshift star formation and galaxy evolution. There is growing evidence from both the emission and intrinsic absorption lines that QSO environments have roughly solar or higher metallicities out to redshifts >4. The range is not well known, but solar to a few times solar appears to be typical. There is also evidence for higher metallicities in more luminous objects, and for generally enhanced N/C and Fe/alpha abundances compared to solar ratios. These results identify QSOs with vigorous, high-redshift star formation -- consistent with the early evolution of massive galactic nuclei or dense proto-galactic clumps. However, the QSOs offer new constraints. For example, 1) most of the enrichment and star formation must occur before the QSOs "turn on" or become observable, on time scales of ~<1 Gyr at least at the highest redshifts. 2) The tentative result for enhanced Fe/alpha suggests that the first local star formation began at least ~1 Gyr prior to the QSO epoch. 3) The star formation must ultimately be extensive in order to reach high metallicities, i.e. a substantial fraction of the local gas must be converted into stars and stellar remnants. The exact fraction depends on the shape of the initial mass function (IMF). 4) The highest derived metallicities require IMFs that are weighted slightly more toward massive stars than the in solar neighborhood. 5) High metallicities also require deep gravitational potentials. By analogy with the well-known mass--metallicity relation among low-redshift galaxies, metal-rich QSOs should reside in galaxies (or proto-galaxies) that are minimally as massive (or as tightly bound) as our own Milky Way.

To appear in the 1999 Annual Review of Astronomy and Astrophysics, 47 pages, 13 figures (3-6 and 12 not embedded)

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• X-ray Clusters of Galaxies as Cosmological Tools
• The X-ray absorber of PKS2126-158
• On the scattering enhancement of Nv1240 emission line of quasi-stellar objects
• Nature and Origins of Rich Complexes of C IV Associated Absorption Lines
• Outflowing material in the zem = 4.92 BAL QSO SDSS~J160501.21-011220.0
• An observational link between AGN Eddington ratio and [NII]λ6583/Ha at 0.6<z<1.7
• Determination of astrophysical parameters of quasars within the Gaia mission
• Metal-rich absorbers at high redshifts: abundance patterns
• Near-Infrared Photometry of the High-Redshift Quasar RDJ030117+002025: Evidence for a Massive Starburst at z=5.5
• Unveiling the quasar main sequence: illuminating the complexity of active galactic nuclei and their evolution
• Spatially extended absorption around the z=2.63 radio galaxy MRC 2025-218: outflow or infall?
• XMM-Newton Observation of Fe Kalpha emission from a BAL QSO: Mrk 231
• How Similar are the Properties of Quasars with Nearly Identical Ultraviolet Spectra?
• Starburst-driven superwinds in quasar host galaxies
• Effects of a burst of formation of first-generation stars on the evolution of galaxies
• The broad OVI absorber at z = 3.02 toward CTQ 325
• The unusual UV continuum of quasar Ton 34 and the possibility of crystalline dust absorption
• An Intercomparison Study of Two Proximate Damped Ly$\alpha$ Systems with Residual Flux upon the Ly$\alpha$ Absorption Trough toward Quasars
• Extreme High-velocity Outflows from High-redshift BOSS Quasars
• 3D AMR hydrosimulations of a compact source scenario for the Galactic Centre cloud G2
• Production of 2H, 3He, and 7Li from Interactions Between Jets and Clouds
• Quasar spectral energy distribution in EUV restored from associated absorbers: indications to the HeII opacity of the quasar accretion disk wind
• X-ray selected broad absorption line quasars in SDSS-V: BALs and non-BALs span the same range of X-ray properties
• Rapidly accreting black hole of the Lyα-luminous quasar PSO J006.1240+39.2219
• Ultraviolet Fe II Emission in Fainter Quasars: Luminosity Dependences, and the Influence of Environments
• Active Galaxies in the UV
• Carbon-loud SDSS BOSS QSO2s at z > 2: High density gas or secondary production of Carbon?
• Multiwavelength Monitoring of the Dwarf Seyfert 1 Galaxy NGC 4395. IV. The Variable UV Absorption Lines
• Nucleosynthesis in advective disc and outflow: possible explanation for overabundances in winds from X-ray binaries
• AGN Host Galaxies
• The CaFe Project: Optical FeII and Near-Infrared Ca II triplet emission in active galaxies. II. The driver(s) of the Ca II and Fe II and its potential use as a chemical clock
• Enhanced AGN Activity in Overdense Galactic Environments at $2<z<4$
• Is the energy generation rate of nuclear reactions in hot accretion flows important?
• High-energy Neutrinos from Stellar Explosions in Active Galactic Nuclei Accretion Disks
• A possible feature of thermal matter in relativistic jets of radio-loud quasars
• Top-heavy stellar mass distribution in galactic nuclei inferred from the universally high abundance ratio of [Fe/Mg]
• Effects of an Immortal Stellar Population in AGN Disks