Evolution of the fundamental plane of 0.2 < z < 1.2 early-type galaxies in the EGS
Context. The fundamental plane links the structural properties of
early-type galaxies such as its surface brightness and effective radius
with its dynamics. The study of the fundamental plane evolution
therefore has important implications for models of galaxy formation and
evolution. <BR /> Aims: This work aims to identify signs of evolution of
early-type galaxies through the study of parameter correlations such as
the fundamental plane, the Kormendy, and the Faber-Jackson relations,
using a sample of 135 field galaxies extracted from the Extended Groth
Strip in the redshift range 0.2 < z < 1.2. <BR /> Methods: We
calculate the internal velocity dispersions with DEEP2 data by
extracting the stellar kinematics from absorption line spectra, using a
maximum penalized-likelihood approach. Morphology was determined through
visual classification of the V + I images of ACS. The structural
parameters of these galaxies were obtained by fitting de Vaucouleurs
stellar profiles to the ACS I-band images with the GALFIT code. To check
the effect on the fundamental plane of the structural parameters,
Sérsic and bulge-to-disc decomposition models were fitted to our
sample of galaxies. A good agreement was found in the fundamental plane
derived from the three models. <BR /> Results: Assuming that effective
radii and velocity dispersions do not evolve with redshift, we found a
brightening of 0.68 mag in the B-band and 0.52 mag in the g-band at
<z> = 0.7. However, the scatter in the fundamental plane for our
high-redshift sample is reduced by half when we allow the fundamental
plane slope to evolve, suggesting a different evolution of early-type
galaxies according to their intrinsic properties such as total mass,
size, or luminosity. The study of the Kormendy relation shows a
population of very compact (R<SUB>e</SUB> < 2 Kpc) and bright
galaxies (-21.5 > M<SUB>g</SUB> > -22.5), of which there are only
a small fraction (0.4%) at z = 0. Studying the luminosity-size and
stellar mass-size relations, we show that the evolution of these compact
objects is mainly caused by an increase in size that could be explained
by the action of dry minor mergers. We also detect an evolution in the
fundamental plane caused mainly by this population of very compact and
bright galaxies. Unfortunately, we cannot distinguish a change in the
slope from an increase in the scatter of the fundamental plane because
our high-redshift sample is biased to the brightest objects.
Table 1 is only available in electronic form at the CDS via anonymous
ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/526/A72">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/526/A72</A>