The axis of evil - a polarization perspective (2009)
Frommert, Mona, Ensslin, Torsten A.
We search for an unusual alignment of the preferred axes of the quadrupole and octopole, the so-called "axis of evil", in the CMB temperature and polarization data from WMAP. We split the temperature...
Cosmic Cartography of the Large-Scale Structure with Sloan Digital Sky Survey Data Release 6 (2009)
Kitaura, Francisco S., Jasche, Jens, Li, Cheng, Ensslin, Torsten A., Metcalf, R. Benton, Wandelt, Benjamin D., ...
We present the largest Wiener reconstruction of the cosmic density field made to date. The reconstruction is based on the Sloan Digital Sky Survey data release 6 covering the northern Galactic cap....
Jansson, Ronnie, Farrar, Glennys R., Waelkens, Andre H., Ensslin, Torsten A.
We introduce a method to quantify the quality-of-fit between data and observables depending on the large scale Galactic magnetic field. We combine WMAP5 polarized synchrotron data and Rotation...
Frommert, Mona, Ensslin, Torsten A.
Secondary anisotropies of the cosmic microwave background (CMB) can be detected by using the cross-correlation between the large-scale structure (LSS) and the CMB temperature fluctuations. In such...
Optimal ISW detection and joint likelihood for cosmological parameter estimation (2008)
Frommert, Mona, Ensslin, Torsten A., Kitaura, Francisco S.
We analyse the local variance effect in the standard method for detecting the integrated Sachs-Wolfe effect (ISW) via cross-correlating the cosmic microwave background (CMB) with the large-scale...
Ensslin, Torsten A., Frommert, Mona, Kitaura, Francisco S.
We develop information field theory (IFT) as a means of Bayesian, data based inference on spatially distributed signals, the information fields. Starting from general considerations on the nature of...
Simulations of cosmic-ray feedback by active galactic nuclei in galaxy clusters (2008)
Sijacki, Debora, Pfrommer, Christoph, Springel, Volker, Ensslin, Torsten A.
Large scale magnetic field of the Milky Way from WMAP3 data (2007)
Jansson, Ronnie, Farrar, Glennys R., Waelkens, Andre, Ensslin, Torsten A.
We report on initial results from a project to constrain the large-scale and turbulent magnetic fields of the Milky Way galaxy, which eventually will incorporate all of the relevant observational...
Pfrommer, Christoph, Ensslin, Torsten A., Springel, Volker
The thermal plasma of galaxy clusters lost most of its information on how structure formation proceeded as a result of dissipative processes. In contrast, non-equilibrium distributions of cosmic rays...
Cosmic rays and the primordial gas (2007)
Jasche, Jens, Ciardi, Benedetta, Ensslin, Torsten A.
One of the most outstanding problems in the gravitational collapse scenario of early structure formation is the cooling of primordial gas to allow for small mass objects to form. As the neutral...
Cosmic ray feedback in hydrodynamical simulations of galaxy and galaxy cluster formation (2006)
Pfrommer, Christoph, Springel, Volker, Jubelgas, Martin, Ensslin, Torsten A.
It is well known that cosmic rays (CRs) contribute significantly to the pressure of the interstellar medium in our own Galaxy, suggesting that they may play an important role in regulating star...
Cosmological structure formation shocks and cosmic rays in hydrodynamical simulations (2006)
Pfrommer, Christoph, Springel, Volker, Ensslin, Torsten A., Jubelgas, Martin
Cosmological shock waves during structure formation not only play a decisive role for the thermalization of gas in virializing structures but also for the acceleration of relativistic cosmic rays...
Pfrommer, Christoph, Ensslin, Torsten A., Springel, Volker, Jubelgas, Martin, Dolag, Klaus
We performed high-resolution simulations of a sample of 14 galaxy clusters that span a mass range from 5 x 10^13 M_solar/h to 2 x 10^15 M_solar/h to study the effects of cosmic rays (CRs) on thermal...
Detecting shock waves in cosmological smoothed particle hydrodynamics simulations (2006)
Pfrommer, Christoph, Springel, Volker, Ensslin, Torsten A., Jubelgas, Martin
We develop a formalism for the identification and accurate estimation of the strength of structure formation shocks during cosmological smoothed particle hydrodynamics simulations. Shocks not only...
Cosmic ray feedback in hydrodynamical simulations of galaxy formation (2006)
Jubelgas, Martin, Springel, Volker, Ensslin, Torsten A., Pfrommer, Christoph
It is well known that cosmic rays (CRs) contribute significantly to the pressure of the interstellar medium in our own Galaxy, suggesting that they may play an important role in regulating star...
Cosmic ray physics in calculations of cosmological structure formation (2006)
Ensslin, Torsten A., Pfrommer, Christoph, Springel, Volker, Jubelgas, Martin
Cosmic rays (CRs) play a decisive role within our own Galaxy. They provide partial pressure support against gravity, they trace past energetic events such as supernovae, and they reveal the...
Deep 1.4 GHz VLA Observations of the Radio Halo and Relic in Abell 2256 (2006)
Clarke, Tracy E., Ensslin, Torsten A.
We present deep VLA observations of the merging galaxy cluster Abell 2256. This cluster is known to possess diffuse steep spectrum radio relic emission in the peripheral regions. Our new observations...
Future magnetic fields studies using the Planck Surveyor experiment (2005)
Ensslin, Torsten A., Vogt, Corina, Waelkens, Andre, Schekochihin, Alexander A.
The Planck mission will permit measurements of the polarization of the cosmic microwave background and of polarized foregrounds such as our own Galaxy with an unprecedented combination of accuracy...
Magnetic Fields in Clusters of Galaxies (2005)
Ensslin, Torsten A., Vogt, Corina, Pfrommer, Christoph
A brief overview about our knowledge on galaxy cluster magnetic fields is provided. Emphasize is given to the mutual dependence of our knowledge on relativistic particles in galaxy clusters and the...
Vogt, Corina, Ensslin, Torsten A.
We present a Bayesian maximum likelihood analysis of Faraday rotation measure (RM) maps of extended radio sources to determine magnetic field power spectra in clusters of galaxies. Using this...
The quest for cosmic ray protons in galaxy clusters (2004)
Pfrommer, Christoph, Ensslin, Torsten A.
There have been many speculations about the presence of cosmic ray protons (CRps) in galaxy clusters over the past two decades. However, no direct evidence such as the characteristic gamma-ray...
Pfrommer, Christoph, Ensslin, Torsten A., Sarazin, Craig L.
The Chandra X-ray Observatory is finding a large number of cavities in the X-ray emitting intra-cluster medium which often coincide with the lobes of the central radio galaxy. We propose...
Pfrommer, Christoph, Ensslin, Torsten A.
We wish to estimate magnetic field strengths of radio emitting galaxy clusters by minimising the non-thermal energy density contained in cosmic ray electrons (CRe), protons (CRp), and magnetic...
Searching for the relativistic Sunyaev-Zeldovich effect with the PLANCK experiment (2004)
Ensslin, Torsten A., Hansen, Steen H.
Populations of relativistic electrons in clusters of galaxies should imprint a characteristic spectral distortion signature on the Cosmic Microwave Background photons - the relativistic...
A Taxonomy of Extended Radio Sources in Clusters of Galaxies (2003)
Kempner, Joshua C., Blanton, Elizabeth L., Clarke, Tracy E., Ensslin, Torsten A., Johnston-Hollitt, Melanie, Rudnick, Lawrence
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...
Vogt, Corina, Ensslin, Torsten A.
We apply a novel technique of Faraday Rotation measure (RM) map analysis to three galaxy clusters, Abell 400, Abell 2634 and Hydra A, in order to estimate cluster magnetic field strengths, length...
Pfrommer, Christoph, Ensslin, Torsten A.
We wish to constrain the cosmic-ray proton (CRp) population in galaxy clusters. By hadronic interactions with the thermal gas of the intra-cluster medium (ICM), the CRp produce gamma-rays for which...
Pfrommer, Christoph, Ensslin, Torsten A.
We examine the cosmic ray proton (CRp) population within the giant elliptical galaxy M 87 using the TeV gamma-ray detection of the HEGRA collaboration. In our scenario, the gamma-rays are produced by...
Many compact radio sources like quasars, blazars, radio galaxies, and micro-quasars emit circular polarisation (CP) with surprising temporal persistent handedness. We propose that the CP is caused by...
The Magnetic Power Spectrum in Faraday Rotation Screens (2003)
Ensslin, Torsten A., Vogt, Corina
The autocorrelation function and similarly the Fourier-power spectrum of a rotation measure (RM) map of an extended background radio source can be used to measure components of the magnetic...
Does circular polarisation reveal the rotation of quasar engines? (2002)
Many radio sources like quasars, blazars, radio galaxies, and micro-quasars exhibit circular polarisation (CP) with surprising temporal persistent handedness. As a possible explanation we propose...
On the escape of cosmic rays from radio galaxy cocoons (2002)
(Abridged) A model for the escape of CR particles from radio galaxy cocoons is presented here. It is assumed that the radio cocoon is poorly magnetically connected to the environment. An extreme case...
Modification of cluster radio halo appearance by the thermal Sunyaev-Zeldovich effect (2002)
We discuss the consequences of the spectral and morphological modification of galaxy cluster radio halos due to the Sunyaev-Zeldovich (SZ) effect for the interpretation of existing and upcoming high...
The Radio Luminosity Function of Cluster Radio Halos (2002)
Ensslin, Torsten A., Roettgering, Huub
A significant fraction of galaxy clusters exhibits cluster wide radio halos. We give a simple prediction of the local and higher redshift radio halo luminosity function (RHLF) on the basis of (i) an...
The Fate of Intracluster Radio Plasma (2002)
Radio plasma injected by active radio galaxies into clusters of galaxies quickly becomes invisible due to radiative losses of the relativistic electrons. In this talk, the fate of radio plasma and...
Bagchi, Joydeep, Ensslin, Torsten A., Miniati, Francesco, Stalin, C. S., Singh, M., Raychaudhury, Somak, ...
We report the discovery of large-scale diffuse radio emission from what appears to be a large-scale filamentary network of galaxies in the region of cluster ZwCl 2341.1+0000, and stretching over an...
Radio and X-Ray Detectability of Buoyant Radio Plasma Bubbles in Clusters of Galaxies (2002)
Ensslin, Torsten A., Heinz, Sebastian
The Chandra X-ray Observatory is finding a surprisingly large number of cavities in the X-ray emitting intracluster medium, produced by the release of radio plasma from active galactic nuclei. In...
Tracing the Remnants of Powerful Quasars to Probe the IGM (2001)
Ensslin, Torsten A., Sunyaev, Rashid A., Brueggen, Markus
Powerful quasars and radio galaxies are injecting large amounts of energy in the form of radio plasma into the inter-galactic medium (IGM). Once this nonthermal component of the IGM has radiatively...
Ensslin, Torsten A., Sunyaev, Rashid A.
Most of the Universe's populations of low energy cosmic ray electrons in the energy range of 1-100 MeV still manage to elude from detection by our instruments, since their synchrotron emission is at...
On the Formation of Cluster Radio Relics (2001)
Ensslin, Torsten A., Brueggen, Marcus
(abridged) We present detailed 3-dimensional magneto-hydrodynamical simulations of the passage of a radio plasma cocoon filled with turbulent magnetic fields through a shock wave. Taking into account...
Fossil Radio Plasma in Cluster Merger Shock Waves (2001)
Ensslin, Torsten A., Brueggen, Marcus
In several merging clusters of galaxies so-called cluster radio relics have been observed. These are extended radio sources which do not seem to be associated with any radio galaxy. Two competing...
Radio Plasma as a Cosmological Probe (2001)
Plasma containing relativistic particles appears in various forms in the inter galactic medium (IGM): As radio plasma released by active radio galaxies, as fossil radio plasma from former radio...
Ensslin, Torsten A., Simon, Patrick, Biermann, Peter L., Klein, Ulrich, Kohle, Sven, Kronberg, Philipp P., ...
Sensitive images of low-level, Mpc-sized radio cocoons offer new opportunities to probe large scale intergalactic gas flows outside clusters of galaxies. New radio images of high surface brightness...
Isotropization of Ultra-High Energy Cosmic Ray Arrival Directions by Radio Ghosts (2000)
Medina-Tanco, Gustavo, Ensslin, Torsten A.
The isotropy in the ultra high energy cosmic ray (UHECR) flux observed by Yakutsk and AGASA experiments, is a very strong constraint to production and propagation models alike. Most of the scenarios...
We give for a plasma with a history of several expansion and contraction phases an analytical model of the evolution of a contained relativistic electron population under synchrotron, inverse Compton...
Particle Acceleration and Diffusion in Fossil Radio Plasma (2000)
The strong activity of radio galaxies should have led to a nearly ubiquitous presence of fossil radio plasma in the denser regions of the inter-galactic medium as clusters, groups and filaments of...
Are Cluster Radio Relics Revived Fossil Radio Cocoons? (2000)
A new model for the, so called, `cluster radio relics' is presented (Ensslin & Gopal-Krishna 2000). Fossil radio cocoons, resulting from the former activity of radio galaxies, should contain a low...
Dolag, Klaus, Ensslin, Torsten A.
We investigate the possibility that radio halos of clusters of galaxies are caused by synchrotron emission of cosmic ray electrons (CRe), which were produced by cosmic ray protons (CRp) interacting...
Comptonization of the Cosmic Microwave Background by Relativistic Plasma (2000)
Ensslin, Torsten A., Kaiser, Christian R.
(Abridged) We investigate the spectral distortion of the cosmic microwave background (CMB) caused by relativistic plasma. Within the Thomson regime, an exact analytic expression for the photon...
Theoretical Implications of Diffuse Non-Thermal Emission from Clusters of Galaxies (2000)
A short review on theoretical implications of non-thermal emission (radio, extreme ultraviolet, high energy X-ray) from the intra-cluster medium is given. The origin of cluster radio halos and...
We investigate the possibility that patches of old radio plasma (`radio ghosts') of former radio galaxies form a second distinct phase of the inter-galactic medium (IGM), not mixed with the thermal...
Cosmic Rays in the Galactic Center Region (1998)
Rhode, Wolfgang, Ensslin, Torsten A., Biermann, Peter L.
EGRET data on the Gamma ray emission from the inner Galaxy have shown a rather flat spectrum, extending to about 50 GeV. It is usually assumed that these gamma-rays arise from the interactions of...
Ensslin, Torsten A., Lieu, Richard, Biermann, Peter L.
The excess in extreme-ultraviolet (EUV) radiation and high energy X-rays (HEX) of Coma may be modeled by power law spectra. Their origin could be inverse Compton (IC) emission by relativistic...
Shock Waves of the Large-Scale Structure Formation in the Universe (1998)
Ensslin, Torsten A., Biermann, Peter L., Klein, Ulrich, Kohle, Sven
Simulations of structure formation in the Universe predict accretion shock waves at the boundaries of the large-scale structures as sheets, filaments, and clusters of galaxies. If magnetic fields are...
Black hole energy release to the Gaseous Universe (1998)
Ensslin, Torsten A, Nath, Biman B., Biermann, Peter L.
We estimate the energy release of black hole formation to the intra-cluster medium of the Coma cluster and find that this is comparable to the present day energy content. Therefore an energetic and...
Black Hole Energy Release to the Gaseous Universe (1998)
Ensslin, Torsten A., Wang, Yiping, Nath, Biman B., Biermann, Peter L.
We estimate the energy release of black hole formation to the intra-cluster medium of the Coma cluster and find that this is comparable to the present day energy content. Therefore an energetic and...
Cluster Radio Relics as a Tracer of Shock Waves of the Large-Scale Structure Formation (1997)
Ensslin, Torsten A., Biermann, Peter L., Klein, Ulrich, Kohle, Sven
We present evidence for the existence of shock waves caused by the formation of the large-scale structure. In some clusters of galaxies peripherally located sources of extended diffuse radio emission...
Ensslin, Torsten A., Biermann, Peter L.
Relativistic electrons, seen in the large diffuse radio halo of the Coma cluster of galaxies, should scatter background photons to higher energies. We calculate the inverse Compton contributions from...