2008 Supplement: Frascati Workshop 2007 / Ota

L_{X}-T Relation and Thermal Evolution of Galaxy Clusters

N. Ota, T. Kitayama, K. Masai, K. Mitsuda


We present an observational approach to constrain the global structure
and evolution of the intracluster medium utilizing the ROSAT and ASCA
distant cluster sample. From statistical analysis of the gas density
profile and the connection to the L_{X}-T relation under the
β-model, the scaled gas profile is found to be nearly universal for
the outer region. On the other hand, a large density scatter exists in
the core region and there is clearly a deviation from the self-similar
scaling for clusters with a small core. The discovery of the existence
of an X-ray fundamental plane in the distant cluster sample suggests
that the cooling time (t_{cool}) is a parameter to control the gas
structure. The appearance of small cores in regular clusters may be
strongly connected with the thermal evolution. We derive the
luminosity-ambient temperature (T') relation, assuming the universal
temperature profile for the clusters with short t_{ cool}, and find
the dispersion around the relation significantly decreases and the slope
becomes marginally less steep. Considering a correlation between
t_{cool} and the X-ray morphology, the observational results lead us to
draw a phenomenological picture: after a cluster collapses and t_{cool}
falls below the age of the universe, the core cools radiatively with
quasi-hydrostatic balancing in the gravitational potential, and the
central density gradually becomes higher to evolve from an
outer-core-dominant cluster, which follows the self-similarity, to
inner-core-dominant cluster.


galaxies: clusters: general X-rays: galaxies: clusters

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