Chemical Abundance Measurements Research Articles

A new measurement of zinc metallicity in a DLA at z∼3.35

We present chemical abundance measurements in the z abs=3.35045 Damped Lyman- α (DLA) system observed in the UVES spectrum of the BAL quasar BR 1117-1329. We measure a neutral hydrogen column density N(HI)=6.9±1.7×10 20 atoms cm −2 and derive mean abundances relative to solar: [Si/H]=−1.26±0.13, [Fe/H]=−1.51±0.13, [Ni/H]=−1.57±0.13, [Cr/H]=−1.36±0.13, [Zn/H]=−1.18±0.13, [Al/H]>−1.25, [O/H]>−1.25 and [N/H]<−2.24. This is the third measurement of Zn, an element mildly depleted onto dust grain, at z abs>3. The iron to zinc and chromium to zinc ratios, [Fe/Zn]=−0.33±0.05 and [Cr/Zn]=−0.18±0.05 demonstrate that the absorber has a low dust content. The nitrogen ratio [N/Si]<−0.98 suggests that the ‘secondary’ N production process is taking place in this DLA. Finally, this absorber does not seem to present a convincing α-enhancement as shown by the α over Fe-peak element ratios: [Si/Fe]=0.25±0.06, [Si/Cr]=0.10±0.06 and [Si/Zn]=−0.08±0.06.

The UCSD HIRES/Keck I Damped Lyα Abundance Database. I. The Data

We present new chemical abundance measurements of 16 damped Lyα systems at z > 1.5 and update our previous abundance analyses. The entire database presented here was derived from HIRES observations on the Keck I telescope, reduced with the same software package, and analyzed with identical techniques. Altogether, we present a large, homogeneous database of chemical abundance measurements for protogalaxies in the early universe, ideal for studying a number of important aspects of galaxy formation. In addition, we have established an on-line directory for this database and will continuously update the results.

Chemical Abundances in Virgo Spiral Galaxies. II. Effects of Cluster Environment

view Abstract Citations (116) References (72) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Chemical Abundances in Virgo Spiral Galaxies. II. Effects of Cluster Environment Skillman, Evan D. ; Kennicutt, Robert C., Jr. ; Shields, Gregory A. ; Zaritsky, Dennis Abstract We present new measurements of chemical abundances in H II regions in spiral galaxies of the Virgo cluster and a comparison of Virgo galaxies and field spirals. With these new data there now exist nine Virgo spirals with abundance measurements for at least four H II regions. Our sample of Virgo galaxies ranges from H I deficient objects near the core of the cluster to galaxies with normal H I properties, far from the cluster core. We investigate the relationship between H I disk characteristics and chemical abundances to determine whether dynamical processes that remove gas from the disk, such as ram pressure stripping by the intracluster medium, also affect the chemical abundances. We divide the nine Virgo spirals into three groups of three galaxies each: those with strong H I deficiencies, intermediate cases, and those with no H I deficiencies. The three most H I deficient Virgo spirals have larger mean abundances (0.3 to 0.5 dex in O/H than the spirals on the periphery of the cluster. This suggests that dynamical processes associated with the cluster environment are more important than cluster membership in determining the current chemical properties of spiral galaxies. There is also weak evidence of shallower abundance gradients in the H I deficient Virgo spirals. We also compare the abundance properties of our Virgo sample to a large sample of field spirals studied by Zaritsky, Kennicutt, & Huchra (1994). Those authors found that the mean abundance of the disk gas increases with increasing maximum circular velocity, increasing luminosity, and decreasing (earlier) Hubble type (but with a large dispersion in the mean abundances and abundance gradients). The dispersion in the properties of field galaxies and the small size of the Virgo sample make it difficult to draw definitive conclusions about any systematic difference between the field and Virgo spirals. Nevertheless, the H I deficient Virgo galaxies have larger mean abundances than field galaxies of comparable luminosity or Hubble type, while the spirals at the periphery of the cluster are indistinguishable from the field galaxies. Simple, illustrative chemical evolution models with infall of metal- poor gas are constructed and compared to models in which the infall is terminated. The models are constrained by comparison with observed gas mass fractions, current star formation rates, and gas consumption times. The model results indicate that the curtailment of infall of metal-poor gas onto cluster core spirals may explain part of the enhanced abundance. However, additional work is needed, particularly modeling of the effects of truncating the outer gaseous disk within the context of models with radial gas transport. The increased abundances in cluster core late-type spirals, relative to field galaxies, may be important in the interpretation of observations of these galaxies. Specifically, we point to possible effects on the Tully-Fisher and Cepheid variable distance determinations and the interpretation of colors in the Butcher-Oemler effect. Publication: The Astrophysical Journal Pub Date: May 1996 DOI: 10.1086/177138 arXiv: arXiv:astro-ph/9511019 Bibcode: 1996ApJ...462..147S Keywords: GALAXIES: ABUNDANCES; GALAXIES: CLUSTERS: INDIVIDUAL NAME: VIRGO; GALAXIES: EVOLUTION; GALAXIES: SPIRAL; ISM: H II REGIONS; Astrophysics E-Print: 53 pages (gzip'ed and uuencoded postscript) Accepted for publication for the Astrophysical Journal full text sources arXiv | ADS | data products SIMBAD (10) NED (9)

The IUE Survey for Damped Lyman- alpha and Lyman-Limit Absorption Systems: Evolution of the Gaseous Content of the Universe

view Abstract Citations (354) References (46) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The IUE Survey for Damped Lyman- alpha and Lyman-Limit Absorption Systems: Evolution of the Gaseous Content of the Universe Lanzetta, Kenneth M. ; Wolfe, Arthur M. ; Turnshek, David A. Abstract We present a spectroscopic survey for moderate-redshift absorption features from damped Lyα and Lyman- limit absorption systems. The survey is based on a set of optimally extracted and co-added International Ultraviolet Explorer spectra of QSOs, BL Lac objects, and Seyfert galaxies. Results of this survey are combined with those of previous surveys carried out at optical wavelengths in order to examine evolution of the gaseous content of the universe over the redshift interval 0.008 ≲ z ≲ 3.5. The main results of the survey are that (1) the product of the absorption cross section and the comoving spatial number density of damped Lyα absorption systems does not appear to evolve strongly over the redshift interval 0.008 ≲ z ≲ 3.5, (2) the cosmological mass density Ωg(z) of neutral gas associated with damped Lyα absorption systems appears to decrease significantly from z 3.5 to 0.008, and (3) the observed evolution of Ωg(z) results from a steady decrease in the incidence of high column density absorption systems with decreasing redshift. Together these results suggest that the average mass of neutral gas per absorption system decreases with time, which is qualitatively consistent with the hypothesis that the observed evolution of Ωg(z) results from the consumption of gas into stars at z ≲ 3.5. We present additional arguments supporting this hypothesis and assess the implications of the observations of Ωg(z) for scenarios of galaxy formation and evolution. Under a "closed box assumption" we determine a characteristic epoch zs of star formation in galaxies of zs = 2-3 and a characteristic timescale τs of star formation in galaxies of r = 0.5-1.0 × 109 h-1 yr at z ≳ 1.5. Considering recent chemical abundance measurements by Pettini et al. and others we conclude that the cosmic metallicity at z ≍ 2.5 is given by log Z(z ≍ 2.5)/Zsun = -1.0±0.5. Comparing the inferred cosmological mass density of metals in gas and stars at the epoch z with the nominal cosmological mass density of metals in nearby galaxies, we conclude that the characteristic epoch of metal production in galaxies occurred after the characteristic epoch of star formation in galaxies. The implication of this result is that the bulk of stars in nearby galaxies should be metal poor, whereas only a small fraction of the disk stars in the solar neighborhood are actually metal poor. This inconsistency represents a cosmic G-dwarf problem" in that a straightforward interpretation of our observations predicts many more metal-poor stars than are found in the solar neighborhood. We propose that the cosmic G-dwarf problem may be resolved if damped Lyα absorption systems trace not only galactic disk evolution, as suggested previously by Wolfe, but also galactic spheroid evolution. Publication: The Astrophysical Journal Pub Date: February 1995 DOI: 10.1086/175286 Bibcode: 1995ApJ...440..435L Keywords: COSMOLOGY: OBSERVATIONS; GALAXIES: ABUNDANCES; GALAXIES: EVOLUTION; GALAXIES: FORMATION; GALAXIES: QUASARS: ABSORPTION LINES full text sources ADS | data products NED (273) SIMBAD (239) MAST (1) INES (1)

Isotopic and chemical investigations on Angra dos Reis

We report on extensive isotopic studies of Pb, Sr and Xe and on chemical abundance measurements of K, Rb, Sr, Ba, Nd, Sm, U and Th for total meteorite and mineral separates of the Angra dos Reis achondrite. U-Pb, Th-Pb and Pb-Pb ages are concordant at 4.54 AE for the total meteorite and for high-purity whitlockite in Angra dos Reis. This establishes Angra dos Reis as an early planetary differentiate which has not been disturbed for these systems since 4.54 AE ago. Measured 87Sr/ 86Sr in pyroxene and whitlockite for Angra dos Reis (ADOR) are distinctly below BABI by two parts in 10 4 and only one part in 10 4 above the lowest 87Sr/ 86Sr (ALL) measured in an Allende inclusion. The difference in ADOR-ALL corresponds to an interval of condensation in the solar nebula of ∼3 m.y. If 26Al was the heat source for the magmatism on the parent planets of Angra dos Reis and the basaltic achondrites (BABI) then the relatively large difference in 87Sr/ 86Sr, BABI - ALL, must be the result of planetary evolution rather than condensation over ∼10 m.y. Xe isotopic measurements confirm the presence of large amounts of 244Pu-produced fission Xe and show that 244Pu was enriched in the whitlockite relative to the pyroxene by a factor of ∼18. We present chemical element enrichment factors between the whitlockite and the fassaitic pyroxene in Angra dos Reis. The enrichment factors demonstrate close analogy between the rare earth elements and their actinide analogs. The enrichment factor for Pu is intermediate to the enrichment factors of Nd and Sm.