Galactic Winds and the Photo-chemical Evolution of Elliptical Galaxies: The Classic Model Revisited

We consider the simultaneous chemical, photometric, and gaseous thermal energy evolution of elliptical galaxies. The evolution of chemical abundances in the intracluster medium (ICM) is set by the differing timescales for gas ejection, via supernovae (SNe)-driven winds, from dwarf, normal, and giant ellipticals, and is monitored concurrently. Emphasis is placed upon the influence of, and sensitivity to, the underlying stellar initial mass function (IMF), star formation efficiency, supernovae Type Ia rates, supernovae remnant (SNR) dynamics, and the most recent advances in stellar nucleosynthesis. Unlike many previous studies, we adhere to a wide range of optical (e.g. colour-metallicity-luminosity relationship) and x-ray (e.g. recent ASCA ICM abundance measurements) observational constraints. IMFs biased toward high mass stars, at least during the early phases of star formation, are implicated in order to satisfy all the observational constraints.Comment: 18 pages, LaTeX, also available at http://msowww.anu.edu.au/~gibson/publications.html, MNRAS, in pres

A Comparison of Three Elliptical Galaxy Photo-chemical Evolution Codes

Working within the classic supernovae-driven wind framework for elliptical galaxy evolution, we perform a systematic investigation into the discrepancies between the predictions of three contemporary codes -- Arimoto & Yoshii (1987, A&A, 173, 23), Bressan et al. (1994, ApJS, 94, 63), and Gibson (1996a, MNRAS, 278, 829; 1996b, MNRAS, submitted). By being primarily concerned with reproducing the present-day colour-metallicity-luminosity (CML) relations amongst ellipticals, the approaches taken in the theoretical modelling have managed to obscure many of the hidden differences between the codes. Targeting the timescale for the onset of the initial galactic wind t_GW as a primary ``difference'' indicator, we demonstrate exactly how and why each code is able to claim successful reproduction of the CML relations, despite possessing apparently incompatible input ingredients.Comment: 30 pages, LaTeX, 3 figures available from http://msowww.anu.edu.au/~gibson/publications.html, to be published in Sept 1996 ApJ, Part

Chemical Evolution of the Carina Dwarf Spheroidal

We explore a range of chemical evolution models for the Local Group dwarf spheroidal (dSph) galaxy, Carina. A novel aspect of our work is the removal of the star formation history (SFH) as a `free parameter' in the modeling, making use, instead, of its colour-magnitude diagram (CMD)-constrained SFH. By varying the relative roles of galactic winds, re-accretion, and ram-pressure stripping within the modeling, we converge on a favoured scenario which emphasises the respective roles of winds and re-accretion. While our model is successful in recovering most elemental abundance patterns, comparable success is not found for all the neutron capture elements. Neglecting the effects of stripping results in predicted gas fractions approximately two orders of magnitude too high, relative to that observed.Comment: Accepted for publication in PoS (Proceedings of Science): Nuclei in the Cosmos XII (Cairns, Aug 2012); 6 pages; 4 figure

Soil development and sampling strategies for the returned Martian surface samples

Sampling of the Martian surface materials should be based on the experience gained from the study of soils and rocks collected in cold, dry environments, i.e., dry valleys of Antarctica. Previous studies have suggested that some of our best terrestrial analogs of the Martian soils are represented by those found in the polar deserts of Antarctica. Special sampling considerations must be taken into account when obtaining these samples because they represent at least five distinct types of materials. Weathering of planetary regolith materials occurs from both chemical and physical interactions of the planet's surface materials with the atmosphere and, if present, the hydrosphere and biosphere along with extraplanetary objects which may produce the original surface materials and produce secondary materials that are product of equilibrium between the atmosphere and study weathering processes and regolith development occurring on Martian-like surfaces, simulation studies must be carried out in materials in the field