1,363 research outputs found
Stabilization of injection-locked lasers using spatial mode interference
We report the use of spatial-mode-interference, or tilt-locking, for the active stabilization of injection-locking of a Nd:YAG laser. We show that this control scheme is robust and adds negligible frequency noise to the injection-locked laserOttaway, D.J.; Gray, M.B.; Shaddock, D.A.; Hollitt, C.; Veitch, P.J.; Munch, J.; McClelland, David Ernes
Unravelling the origin of large-scale magnetic fields in galaxy clusters and beyond through Faraday Rotation Measures with the SKA
We investigate the possibility for the SKA to detect and study the magnetic
fields in galaxy clusters and in the less dense environments surrounding them
using Faraday Rotation Measures. To this end, we produce 3-dimensional magnetic
field models for galaxy clusters of different masses and in different stages of
their evolution, and derive mock rotation measure observations of background
radiogalaxies. According to our results, already in phase I, we will be able to
infer the magnetic field properties in galaxy clusters as a function of the
cluster mass, down to solar-masses. Moreover, using cosmological
simulations to model the gas density, we have computed the expected rotation
measure through shock-fronts that occur in the intra-cluster medium during
cluster mergers. The enhancement in the rotation measure due to the density
jump will permit to constraint the magnetic field strength and structure after
the shock passage. SKA observations of polarised sources located behind galaxy
clusters will answer several questions about the magnetic field strength and
structure in galaxy clusters, and its evolution with cosmic time.Comment: 9 pages, 4 Figures, to appear as part of 'Cosmic Magnetism' in
Proceedings 'Advancing Astrophysics with the SKA (AASKA14)', PoS(AASKA14
A Taxonomy of Extended Radio Sources in Clusters of Galaxies
At the request of the conference attendees, we have compiled a classification
of extended radio sources in clusters. These range from scales of tens of
parsecs to over a megaparsec in scale, and include both sources associated with
AGN and sources thought to derive from the electron population in the ionized
ICM. We pay special attention to distinguishing between the types of AGN in the
cores of cooling flow clusters and between the multiple classes of objects
referred to over the years as ``radio relics.'' We suggest new names based on
physical arguments for some of these classes of objects where their commonly
used names are inappropriate or confusing.Comment: 5 pages, to appear in "The Riddle of Cooling Flows in Galaxies and
Clusters of Galaxies," held in Charlottesvile, VA, May 31 - June 4, 2003, ed.
T. H. Reiprich, J. C. Kempner, and N. Soker,
http://www.astro.virginia.edu/coolflow
Cluster magnetic fields through the study of polarized radio halos in the SKA era
Galaxy clusters are unique laboratories to investigate turbulent fluid
motions and large scale magnetic fields. Synchrotron radio halos at the center
of merging galaxy clusters provide the most spectacular and direct evidence of
the presence of relativistic particles and magnetic fields associated with the
intracluster medium. The study of polarized emission from radio halos is
extremely important to constrain the properties of intracluster magnetic fields
and the physics of the acceleration and transport of the relativistic
particles. However, detecting this polarized signal is a very hard task with
the current radio facilities.We use cosmological magneto-hydrodynamical
simulations to predict the expected polarized surface brightness of radio halos
at 1.4 GHz. We compare these expectations with the sensitivity and the
resolution reachable with the SKA1. This allows us to evaluate the potential
for studying intracluster magnetic fields in the surveys planned for SKA1.Comment: 11 pages, 4 figures; to appear as part of 'Cosmic Magnetism' in
Proceedings 'Advancing Astrophysics with the SKA (AASKA14)', PoS(AASKA14)10
Redshifts and Velocity Dispersions of Galaxy Clusters in the Horologium-Reticulum Supercluster
We present 118 new optical redshifts for galaxies in 12 clusters in the
Horologium-Reticulum supercluster (HRS) of galaxies. For 76 galaxies, the data
were obtained with the Dual Beam Spectrograph on the 2.3m telescope of the
Australian National University at Siding Spring Observatory. After combining 42
previously unpublished redshifts with our new sample, we determine mean
redshifts and velocity dispersions for 13 clusters, in which previous
observational data were sparse. In six of the 13 clusters, the newly determined
mean redshifts differ by more than 750 km/s from the published values. In the
case of three clusters, A3047, A3109, and A3120, the redshift data indicate the
presence of multiple components along the line of sight. The new cluster
redshifts, when combined with other reliable mean redshifts for clusters in the
HRS, are found to be distinctly bi-modal. Furthermore, the two redshift
components are consistent with the bi-modal redshift distribution found for the
inter-cluster galaxies in the HRS by Fleenor et al. (2005).Comment: 13 pages, 3 figures, Accepted to A
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