5 research outputs found
Large-scale magnetized outflows from the Virgo Cluster spiral NGC 4569 : a galactic wind in a ram pressure wind
Using the Effelsberg radio telescope at 4.85 GHz and 8.35 GHz we
discovered large symmetric lobes of polarized radio emission around the
strongly H
Large-scale magnetized outflows from the Virgo Cluster spiral NGC4569
Using the Effelsberg radio telescope at 4.85GHz and 8.35 GHz we discovered
large symmetric lobes of polarized radio emission around the strongly HI
deficient Virgo cluster spiral galaxy NGC4569. These lobes extend up to 24 kpc
from the galactic disk. Our observations were complemented by 1.4 GHz continuum
emission from existing HI observations. This is the first time that such huge
radio continuum lobes are observed in a cluster spiral galaxy. The eastern lobe
seems detached and has a flat spectrum typical for in-situ cosmic ray electron
acceleration. The western lobe is diffuse and possesses vertical magnetic
fields over its whole volume. The lobes are not powered by an AGN, but probably
by a nuclear starburst producing >10^5 supernovae which occurred ~30 Myr ago.
Since the radio lobes are symmetric, they resist ram pressure due to the
galaxy's rapid motion within the intracluster medium.Comment: Accepted for publication in A&A, 8 pages, 6 figure
The magnetic fields of large Virgo Cluster spirals
Because of its proximity the Virgo Cluster is an excellent target for
studying interactions of galaxies with the cluster environment. Both the
high-velocity tidal interactions and effects of ram pressure stripping by the
intracluster gas can be investigated. Optical and/or \ion{H}{i} observations do
not always show effects of weak interactions between galaxies and their
encounters with the cluster medium. For this reason we searched for possible
anomalies in the magnetic field structure in Virgo Cluster spirals which could
be attributed to perturbations in their gas distribution and kinematics. Five
angularly large Virgo Cluster spiral galaxies (NGC 4501, NGC 4438, NGC 4535,
NGC 4548 and NGC 4654) were the targets for a sensitive total power and
polarization study using the 100-m radio telescope in Effelsberg at 4.85 GHz.
For two objects polarization data at higher frequencies have been obtained
allowing Faraday rotation analysis. Distorted magnetic field structures were
identified in all galaxies. Interaction-induced magnetized outflows were found
in NGC 4438 (due to nuclear activity) and NGC 4654 (a combination of tidal
tails and ram pressure effects). Almost all objects (except the anaemic NGC
4548) exhibit distortions in polarized radio continuum attributable to
influence of the ambient gas. For some galaxies they agree with observations of
other species, but sometimes (NGC 4535) the magnetic field is the only tracer
of the interaction with the cluster environment. The cluster environment
clearly affects the evolution of the galaxies due to ram pressure and tidal
effects. Magnetic fields provide a very long-lasting memory of past
interactions. Therefore, they are a good tracer of weak interactions which are
difficult to detect by other observations.Comment: 13 pages, 12 figure