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Ages and Metallicities of Extragalactic Globular Clusters from Spectral Line Indices: M104
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Chemical evolution of the intra-cluster medium
Full text linkThe high metallicity of the intra–cluster medium (ICM) is
generally interpreted on the basis of the galactic wind scenario for
elliptical galaxies. In this framework, we develop a toy model to follow
the chemical evolution of the ICM, formulated in
analogy to chemical models for individual galaxies.
The model computes the galaxy formation history (GFH)
of cluster galaxies, connecting the final luminosity function (LF)
to the corresponding metal enrichment history of the ICM.
The observed LF can be reproduced with a smooth, Madau–plot like GFH
peaking at ,
plus a “burst” of formation of dwarf galaxies at high redshift.
The model is used to test the response of the predicted
metal content and abundance evolution of the ICM to varying input
galactic models.
The chemical enrichment is
computed from “galactic yields” based on models of elliptical
galaxies with a variable initial mass function (IMF), favouring
the formation of massive stars at high redshift and/or
in more massive galaxies. For a given final galactic luminosity, these model
ellipticals eject into the ICM a larger quantity of gas and of metals
than do standard models based on the Salpeter IMF.
However, a scenario in which the IMF varies with redshift as a consequence
of the
effect of the cosmic background temperature on the Jeans mass scale
appears to be
too mild to account for the observed metal production in clusters.
The high iron–mass–to–luminosity–ratio
of the ICM
can be reproduced only by assuming a more dramatic variation of the typical
stellar mass, in line with other recent findings. The mass
in the wind–ejected gas is predicted to exceed the mass in galaxies by
a factor of 1.5–2 and to constitute roughly half of the intra–cluster gas
The HST/ACS Survey of Galactic Globular Clusters: Variability of the Blue Straggler Stars
No full textCan a "standard" initial mass function explain the metal enrichment in clusters of galaxies ?
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