相关论文: Iron and alpha-element Production in the First One…

We present seven new abundance measurements of the elements O, C and Si at z > 4.5, doubling the existing sample of weakly depleted elements in gas-rich galaxies, in order to constrain the first ~1 billion years of cosmic metal evolution.…

Element abundances in high-redshift quasar absorbers offer excellent probes of the chemical enrichment of distant galaxies, and can constrain models for population III and early population II stars. Recent observations indicate that the…

In typical astrophysical environments, the abundance of heavy elements ranges from 0.001 to 2 times the solar concentration. Lower abundances have been seen in select stars in the Milky Way's halo and in two quasar absorption systems at…

Damped Lyman-alpha absorbers (DLAs), seen in absorption against a background quasar, provide the most detailed probes available of element abundances in the Universe over > 90 % of its age. DLAs can be used to observationally measure the…

In this first paper of a series, we report on the use of quasar spectra obtained with the UVES high resolution spectrograph and available through the ESO VLT archive to build the first sample of sub-DLA systems, absorbers with HI column…

We explore the redshift evolution of the metal content of damped Lyman alpha systems (DLAs) with new observations of four absorbers at z < 1.5 . The main conclusion is that the column density--weighted mean metallicity, [<Zn/H>] = -1.03 +/-…

We present results of the analysis of near infrared spectroscopic observations of 6 high-redshift quasars (z > 4), emphasizing the measurement of the ultraviolet FeII/MgII emission line strength in order to estimate the beginning of intense…

We present chemical abundance measurements from high-resolution observations of 5 sub-damped Lyman-alpha absorbers at 1.7 < z < 2.4 observed with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph on the 6.5-m Magellan II Clay…

In order to derive information on the star formation history in the early universe we observed 6 high-redshift (z=3.4) quasars in the near-infrared to measure the relative iron and \mgii emission strengths. A detailed comparison of the…

The iron abundance relative to alpha-elements in the circumnuclear region of quasars is regarded as a clock of the star formation history and, more specifically, of the enrichment by SNIa. We investigate the iron abundance in a sample of 22…

(Abbreviated) From six spectra of high-z QSOs, we select eleven metal-rich, Z>=Z_solar, and optically-thin to the ionizing radiation, N(HI)<10^17 cm^-2, absorption systems ranging between z=1.5 and z=2.9 and revealing lines of different…

We analyze relative abundances and ionization conditions in a strong absorption system at z=6.84, seen in the spectrum of the z=7.54 background quasar ULAS J134208.10+092838.61. Singly ionized C, Si, Fe, Mg, and Al measurements are…

We apply the phenomenological model used to explain the abundances of Fe and r-process elements in very metal-poor stars in the Galaxy to [Fe/H] of damped Ly alpha systems. It is assumed that the first stars formed after the Big Bang were…

We present chemical abundance measurements from medium resolution observations of 8 sub-damped Lyman-alpha absorber and 2 strong Lyman-limit systems at z < 1.5 observed with the MIKE spectrograph on the 6.5m Magellan II Clay telescope.…

A powerful technique to trace the signatures of the first stars is through the metal enrichment in concentrated reservoirs of hydrogen, such as the damped Lyman-alpha absorbers (DLAs) in the early universe. We conducted a survey aimed at…

This study focuses on some of the most metal-poor damped Lyman alpha absorbers known in the spectra of high redshift QSOs, using new and archival observations obtained with UV-sensitive echelle spectrographs on the Keck and VLT telescopes.…

Ratios of different ions of the same element encode ionization information independently from relative abundances in quasar absorption line systems, crucial for understanding the multiphase nature and origin of absorbing gas, particularly…

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…

We have obtained low-resolution near infrared spectra of three QSOs at 5.7 < z < 6.3 using the NICMOS instrument of the Hubble Space Telescope. The spectra cover the rest-frame ultraviolet emission of the objects between lambda_rest ~ 1600A…

We present evidence that clumps of \lya lines are physically associated with about half of the extensive metal-line systems (absorption systems with four or more observed metal-line species) found in this paper, demonstrate that all four…