Ionization Properties and Elemental Abundances in Damped Ly alpha Systems

Details Ionization Properties and Elemental Abundances in Damped Ly alpha Systems Ionization Properties and Elemental Abundances in Damped Ly alpha Systems

2001-04-18

arxiv.org/abs/astro-ph/0104298v1

Astronomy and Astrophysics

Astrophysics

20 pages including 16 figures, accepted for publication in the Astrophysical Journal, Vol. 557, No. 1, Aug 10, 2001

Scientific paper

10.1086/321650

We analyze extant data of Al++, Al+ and other low ions with the aim of studying the ionization properties of Damped Ly alpha systems (DLAs) from the analysis of the ratio R(Al++/Al+) = N(Al++)/N(Al+). We find good correlations logN(Al+)-logN(Si+) and logN(Al+)-logN(Fe+) that we use to indirectly estimate N(Al+) from N(Si+) and/or N(Fe+) measurements. In this way we determine the ratio R(Al++/Al+) for a sample of 20 DLAs. Contrary to common belief, the ratio can attain relatively high values (up to 0.6), suggesting that gas of intermediate ionization state plays an important role in DLAs. On the other hand, the lack of any trend between abundance ratios, such as Si/H and Si/Fe, and R(Al++/Al+) indicates that abundances are not severely influenced by ionization effects. We find a logR(Al++/Al+) - logN(H I) anticorrelation that we use, in conjunction with idealized photoionization equilibrium calculations, to constrain the ionization properties and to predict ionization corrections in DLAs. We consider two possible origins for the species of low and intermediate ionization state: (1) neutral regions devoid of Al++ and/or (2) partially ionized, (Al++)-bearing regions. The logR(Al++/Al+) - logN(H I) anticorrelation can be naturally explained in terms of a two-region model with a soft, stellar-type ionizing radiation field. We present abundance ionization corrections for 14 elements of astrophysical interest derived with different types of ionizing spectra. For most of these elements the corrections are generally below measurements errors, contrary to the predictions of recent models presented in the literature. We briefly discuss the potential effects of inaccuracies of the Al recombination rates used in the photoionization calculations.

Affiliated with

Also associated with

No associations

Rating

Ionization Properties and Elemental Abundances in Damped Ly alpha Systems does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Ionization Properties and Elemental Abundances in Damped Ly alpha Systems, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ionization Properties and Elemental Abundances in Damped Ly alpha Systems will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-563771