405 research outputs found
Extended reagions of radio emission not associated with the AGN phenomenon as sources of acceleration of cosmic rays: The case of cD galaxies
Diffuse, non-thermal extended emission not associated with the AGN
phenomenon, found in many clusters of galaxies hosted by an AGN, are related to
the acceleration of cosmic rays. In the current work we present preliminary
evidence of absence of such formations in clusters of galaxies hosted by
optically identified cD galaxies. Our subsample consists of three powerful low
redshift radiogalaxies, centered in poor clusters of galaxies. We have searched
for radio relics and (mini)halos which could be forming as a result of the
confinement of cosmic rays by bubbles creayed by the AGN. We report on the work
in progress.Comment: 4 pages, Conference HEPRO II
HST images and properties of the most distant radio galaxies
We present Hubble Space Telescope images of 11 high redshift radio galaxies
(between and ). The galaxies were observed with the WFPC2 camera
in a broad band filter (F606W or F707W, roughly equivalent to V or R-band), for
2 orbits each. We find that on the scale of the HST observations there is a
wide variety of morphological structures of the hosting galaxies: most objects
have a clumpy, irregular appearance, consisting of a bright nucleus and a
number of smaller components, suggestive of merging systems. Some observed
structures could be due (at least partly) to the presence of dust distributed
through the galaxies. The UV continuum emission is generally elongated and
aligned with the axis of the radio sources, however the characteristics of the
``alignment effect'' differ from case to case, suggesting that the phenomenon
cannot be explained by a single physical mechanism. We compare the properties
of our radio galaxies with those of the
UV dropout galaxies and conclude that (i) the most massive radio galaxies may
well evolve from an aggregate of UV dropout galaxies and (ii) high redshift
radio galaxies probably evolve into present day brightest cluster galaxies.Comment: 22 pages, 30 figures, accepted by A&
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