Thursday, 24 July 2008

From the paper 'Red Nuggets at z ∼ 1.5: Compact passive galaxies and the
formation of the Kormendy Relation' by Damjanov et al (0807.1744) I chose these two plots.

We had discussions before about these tiny galaxies that Mariska and Pieter investigated. These authors do sort of the same job, but at slightly lower redshift (1.5-ish). The left plot shows the effective radius - stellar mass plane, with the dots and contours being local SDSS red galaxies. The bigger points with error bars are their (and some other) red galaxies at higher redshift, which appear to small. I show this plot, because the arrows indicate the approximate track of evolution due to three different processes: dry mergers, pure stellar mass growth without changing size and adiabatic expansion (stellar mass loss makes the systems less bound). All three processes seem incapable of transforming the galaxies towards the low - z counterparts.

The right plot shows the galaxies in the stellar mass density - effective radius plane (Kormendy relation). Here they are all on the same trend, with the high redshift galaxies smaller and denser than their local red SDSS partners. Color coding here is redshift, which appears to hint at some evolution: the higher the redshift of the galaxy, the smaller and denser it is. The main part of the evolution takes place at 1.1 < z < 1.5.

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