22,827 research outputs found
Why are there strong radio AGNs in the center of "non-cool core" clusters?
Radio AGN feedback in X-ray cool cores has been proposed as a crucial
ingredient in the evolution of baryonic structures. However, it has long been
known that strong radio AGNs also exist in "noncool core" clusters, which
brings up the question whether an X-ray cool core is always required for radio
feedback. We present a systematic analysis of 152 groups and clusters to show
that every BCG with a strong radio AGN has an X-ray cool core. Those strong
radio AGNs in the center of the "noncool core" systems identified before are in
fact associated with small X-ray cool cores with typical radii of < 5 kpc (we
call them coronae). Small coronae are most likely of ISM origin and they carry
enough fuel to power radio AGNs. Our results suggest that the traditional cool
core/noncool core dichotomy is too simple. A better alternative is the cool
core distribution function with the enclosed X-ray luminosity. Other
implications of our results are also discussed, including a warning on the
simple extrapolation of the density profile to derive Bondi accretion rate.Comment: 4 pages, 2 figure, to appear in proceedings of the conference "The
Monster's Fiery Breath: Feedback in Galaxies, Groups, and Clusters", June
2009, Madison, WI, Eds. S. Heinz & E. Wilcot
Probing the topological charge in QCD matter via multiplicity up-down asymmetry
Relativistic heavy ion collisions provide the possibility to study the
topological charge in QCD matter through the event-by-event fluctuating net
axial charge or nonequal numbers of left- and right-handed quarks they generate
in the produced quark-gluon plasma. Based on the chiral kinetic approach for
nearly massless quarks and antiquarks in the strong vorticity field produced
along the normal direction of the reaction plane of non-central heavy ion
collisions, we show that a unique signal for the topological charge in QCD
matter can be identified from the asymmetric distribution of particles with
momenta pointing in the upper and lower hemispheres of the reaction plane as a
result of the fluctuating net axial charge.Comment: 6 pages and 4 figure
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