Kavli Affiliate: Wendy Freedman
| First 5 Authors: Ilaria Lonoce, Wendy Freedman, Anja Feldmeier-Krause, ,
| Summary:
The Hydra I cluster offers an excellent opportunity to study and compare the
relic old stellar populations in the core of its two brightest galaxies. In
addition, the differing kinematics of the two galaxies allows a test of the
local validity of general scaling relations. In this work we present a direct
comparison employing full spectral fitting of new high-quality long-slit
optical and NIR spectroscopic data. We retrieve age, metallicity and 19
elemental abundances out to about 12 kpc within each galaxy, as well as the IMF
in their central regions. Our results suggest that the inner 5 kpc region of
both galaxies, despite their different masses, formed at the same time and
evolved with a similar star formation time-scale and chemical enrichment,
confirming their early formation in the cluster build up. Only the overall
metallicity and IMF radial profiles show differences connected with their
different velocity dispersion profiles. The radial trend of the IMF positively
correlates with both [Z/H] and velocity dispersion. While the trends of the IMF
with metallicity agree with a global trend for both galaxies, the trends with
the velocity dispersion exhibit differences. The outer regions show signs of
mixed stellar populations with large differences in chemical content compared
to the centers, but with similar old ages.
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