Synthetic Observations of Simulated AGN Jets: X-ray Cavities

Observations of X-ray cavities formed by powerful jets from AGN in galaxy cluster cores are widely used to estimate the energy output of the AGN. Using methods commonly applied to observations of clusters, we conduct synthetic X-ray observations of 3D MHD simulated jet-ICM interactions to test the reliability of measuring X-ray cavity power. These measurements are derived from empirical estimates of the enthalpy content of the cavities and their implicit ages. We explore how such physical factors as jet intermittency and observational conditions such as orientation of the jets with respect to the line of sight impact the reliability of observational measurements of cavity enthalpy and age. An estimate of the errors in these quantities can be made by directly comparing "observationally" derived values with "actual" values from the simulations. In our tests, cavity enthalpy derived from observations was typically within a factor of two of the simulation values. Cavity age and, therefore, cavity power are sensitive to the accuracy of the estimated inclination angle of the jets. Cavity age and power estimates within a factor of two of the actual values are possible given an accurate inclination angle.Comment: 34 pages, 14 figures, accepted for publication in Ap

Three-Dimensional Simulations of Bi-Directed Magnetohydrodynamic Jets Interacting with Cluster Environments

We report on a series of three-dimensional magnetohydrodynamic simulations of active galactic nucleus (AGN) jet propagation in realistic models of magnetized galaxy clusters. We are primarily interested in the details of energy transfer between jets and the intracluster medium (ICM) to help clarify what role such flows could have in the reheating of cluster cores. Our simulated jets feature a range of intermittency behaviors, including intermittent jets that periodically switch on and off and one model jet that shuts down completely, naturally creating a relic plume. The ICM into which these jets propagate incorporates tangled magnetic field geometries and density substructure designed to mimic some likely features of real galaxy clusters. We find that our jets are characteristically at least 60% efficient at transferring thermal energy to the ICM. Irreversible heat energy is not uniformly distributed, however, instead residing preferentially in regions very near the jet/cocoon boundaries. While intermittency affects the details of how, when, and where this energy is deposited, all of our models generically fail to heat the cluster cores uniformly. Both the detailed density structure and nominally weak magnetic fields in the ICM play interesting roles in perturbing the flows, particularly when the jets are non-steady. Still, this perturbation is never sufficient to isotropize the jet energy deposition, suggesting that some other ingredient is required for AGN jets to successfully reheat cluster cores.Comment: 19 pages, 18 figures, Accepted for publication in the Astrophysical Journa

MHD Simulations of AGN Jets in a Dynamic Galaxy Cluster Medium

We present a pair of 3-d magnetohydrodynamical simulations of intermittent jets from a central active galactic nucleus (AGN) in a galaxy cluster extracted from a high resolution cosmological simulation. The selected cluster was chosen as an apparently relatively relaxed system, not having undergone a major merger in almost 7 Gyr. Despite this characterization and history, the intra-cluster medium (ICM) contains quite active "weather". We explore the effects of this ICM weather on the morphological evolution of the AGN jets and lobes. The orientation of the jets is different in the two simulations so that they probe different aspects of the ICM structure and dynamics. We find that even for this cluster that can be characterized as relaxed by an observational standard, the large-scale, bulk ICM motions can significantly distort the jets and lobes. Synthetic X-ray observations of the simulations show that the jets produce complex cavity systems, while synthetic radio observations reveal bending of the jets and lobes similar to wide-angle tail (WAT) radio sources. The jets are cycled on and off with a 26 Myr period using a 50% duty cycle. This leads to morphological features similar to those in "double-double" radio galaxies. While the jet and ICM magnetic fields are generally too weak in the simulations to play a major role in the dynamics, Maxwell stresses can still become locally significant.Comment: 20 pages, 14 figures, accepted for publication in the Astrophysical Journa

Polymer depletion interaction between two parallel repulsive walls

The depletion interaction between two parallel repulsive walls confining a dilute solution of long and flexible polymer chains is studied by field-theoretic methods. Special attention is paid to self-avoidance between chain monomers relevant for polymers in a good solvent. Our direct approach avoids the mapping of the actual polymer chains on effective hard or soft spheres. We compare our results with recent Monte Carlo simulations [A. Milchev and K. Binder, Eur. Phys. J. B 3, 477 (1998)] and with experimental results for the depletion interaction between a spherical colloidal particle and a planar wall in a dilute solution of nonionic polymers [D. Rudhardt, C. Bechinger, and P. Leiderer, Phys. Rev. Lett. 81, 1330 (1998)].Comment: 17 pages, 3 figures. Final version as publishe

A relationship between AGN jet power and radio power

Using Chandra X-ray and VLA radio data, we investigate the scaling relationship between jet power, P_jet, and synchrotron luminosity, P_rad. We expand the sample presented in Birzan et al. (2008) to lower radio power by incorporating measurements for 21 gEs to determine if the Birzan et al. (2008) P_jet-P_rad scaling relations are continuous in form and scatter from giant elliptical galaxies (gEs) up to brightest cluster galaxies (BCGs). We find a mean scaling relation of P_jet approximately 5.8x10^43 (P_rad/10^40)^(0.70) erg/s which is continuous over ~6-8 decades in P_jet and P_rad with a scatter of approximately 0.7 dex. Our mean scaling relationship is consistent with the model presented in Willott et al. (1999) if the typical fraction of lobe energy in non-radiating particles to that in relativistic electrons is > 100. We identify several gEs whose radio luminosities are unusually large for their jet powers and have radio sources which extend well beyond the densest parts of their X-ray halos. We suggest that these radio sources are unusually luminous because they were unable to entrain appreciable amounts of gas.Comment: Accepted for publication in the Astrophysical Journal; 8 pages, 3 color figures, 1 tabl

Influence of long-range correlated surface and near the surface disorder on the process of adsorption of long-flexible polymer chains

The influence of long-range correlated surface and decaying near surface disorder with quenched defects is studied. We consider a correlation function for the defects of the form $\frac{e^{-z/\xi}}{r^{a}}$, where $a<d-1$ and $z$ being the coordinate in the direction perpendicular to the surface and $r$ denotes the distance parallel to the surface. We investigate the process of adsorption of long-flexible polymer chains with excluded volume interactions on a "marginal" and attractive wall in the framework of renormalization group field theoretical approach up to first order of perturbation theory in a double ($\epsilon$,$\delta$)- expansion ($\epsilon=4-d$, $\delta=3-a$) for the semi-infinite $|\phi|^4$ $O(m,n)$ model with the above mentioned type of surface and near the surface disorder in the limit $m,n\to 0$. In particular we study two limiting cases. First, we investigate the scenario where the chain's extension it much larger then $\xi$. Second, we consider the case where the chain's extension is of the order of $\xi$. For both cases we obtained series for bulk and the whole set of surface critical exponents, characterizing the process of adsorption of long-flexible polymer chains at the surface. The polymer linear dimensions parallel and perpendicular to the surface and the corresponding partition functions as well as the behavior of monomer density profiles and the fraction of adsorbed monomers at the surface and in the volume are studied.Comment: 31 pages, 5 figures, 2 table

Measuring the non-thermal pressure in early type galaxy atmospheres: A comparison of X-ray and optical potential profiles in M87 and NGC1399

We compare the gravitational potential profiles of the elliptical galaxies NGC 4486 (M87) and NGC 1399 (the central galaxy in the Fornax cluster) derived from X-ray and optical data. This comparison suggests that the combined contribution of cosmic rays, magnetic fields and micro-turbulence to the pressure is ~10% of the gas thermal pressure in the cores of NGC 1399 and M87, although the uncertainties in our model assumptions (e.g., spherical symmetry) are sufficiently large that the contribution could be consistent with zero. In the absence of any other form of non-thermal pressure support, these upper bounds translate into upper limits on the magnetic field of ~10-20 muG at a distance of 1'-2' from the centers of NGC1399 and M87. We show that these results are consistent with the current paradigm of cool cluster cores, based on the assumption that AGN activity regulates the thermal state of the gas by injecting energy into the intra-cluster medium. The limit of ~10-20% on the energy density in the form of relativistic protons applies not only to the current state of the gas, but essentially to the entire history of the intra-cluster medium, provided that cosmic ray protons evolve adiabatically and that their spatial diffusion is suppressed.Comment: Accepted for MNRAS. 19 pages; 14 figures; expanded version in response to comments from the refere

αEβ7 Integrin Identifies Subsets of Pro-Inflammatory Colonic CD4+ T Lymphocytes in Ulcerative Colitis.

Background and Aims The αEβ7 integrin is crucial for retention of T lymphocytes at mucosal surfaces through its interaction with E-cadherin. Pathogenic or protective functions of these cells during human intestinal inflammation, such as ulcerative colitis [UC], have not previously been defined, with understanding largely derived from animal model data. Defining this phenotype in human samples is important for understanding UC pathogenesis and is of translational importance for therapeutic targeting of αEβ7-E-cadherin interactions. Methods αEβ7+ and αEβ7- colonic T cell localization, inflammatory cytokine production and expression of regulatory T cell-associated markers were evaluated in cohorts of control subjects and patients with active UC by immunohistochemistry, flow cytometry and real-time PCR of FACS-purified cell populations. Results CD4+αEβ7+ T lymphocytes from both healthy controls and UC patients had lower expression of regulatory T cell-associated genes, including FOXP3, IL-10, CTLA-4 and ICOS in comparison with CD4+αEβ7- T lymphocytes. In UC, CD4+αEβ7+ lymphocytes expressed higher levels of IFNγ and TNFα in comparison with CD4+αEβ7- lymphocytes. Additionally the CD4+αEβ7+ subset was enriched for Th17 cells and the recently described Th17/Th1 subset co-expressing both IL-17A and IFNγ, both of which were found at higher frequencies in UC compared to control. Conclusion αEβ7 integrin expression on human colonic CD4+ T cells was associated with increased production of pro-inflammatory Th1, Th17 and Th17/Th1 cytokines, with reduced expression of regulatory T cell-associated markers. These data suggest colonic CD4+αEβ7+ T cells are pro-inflammatory and may play a role in UC pathobiology

Phylogenetic classification of Cordyceps and the clavicipitaceous fungi

Cordyceps, comprising over 400 species, was historically classified in the Clavicipitaceae, based on cylindrical asci, thickened ascus apices and filiform ascospores, which often disarticulate into part-spores. Cordyceps was characterized by the production of well-developed often stipitate stromata and an ecology as a pathogen of arthropods and Elaphomyces with infrageneric classifications emphasizing arrangement of perithecia, ascospore morphology and host affiliation. To refine the classification of Cordyceps and the Clavicipitaceae, the phylogenetic relationships of 162 taxa were estimated based on analyses consisting of five to seven loci, including the nuclear ribosomal small and large subunits (nrSSU and nrLSU), the elongation factor 1α (tef1), the largest and the second largest subunits of RNA polymerase II (rpb1 and rpb2), β-tubulin (tub), and mitochondrial ATP6 (atp6). Our results strongly support the existence of three clavicipitaceous clades and reject the monophyly of both Cordyceps and Clavicipitaceae. Most diagnostic characters used in current classifications of Cordyceps (e.g., arrangement of perithecia, ascospore fragmentation, etc.) were not supported as being phylogenetically informative; the characters that were most consistent with the phylogeny were texture, pigmentation and morphology of stromata. Therefore, we revise the taxonomy of Cordyceps and the Clavicipitaceae to be consistent with the multi-gene phylogeny. The family Cordycipitaceae is validated based on the type of Cordyceps, C. militaris, and includes most Cordyceps species that possess brightly coloured, fleshy stromata. The new family Ophiocordycipitaceae is proposed based on Ophiocordyceps Petch, which we emend. The majority of species in this family produce darkly pigmented, tough to pliant stromata that often possess aperithecial apices. The new genus Elaphocordyceps is proposed for a subclade of the Ophiocordycipitaceae, which includes all species of Cordyceps that parasitize the fungal genus Elaphomyces and some closely related species that parasitize arthropods. The family Clavicipitaceae s. s. is emended and includes the core clade of grass symbionts (e.g., Balansia, Claviceps, Epichloë, etc.), and the entomopathogenic genus Hypocrella and relatives. In addition, the new genus Metacordyceps is proposed for Cordyceps species that are closely related to the grass symbionts in the Clavicipitaceae s. s. Metacordyceps includes teleomorphs linked to Metarhizium and other closely related anamorphs. Two new species are described, and lists of accepted names for species in Cordyceps, Elaphocordyceps, Metacordyceps and Ophiocordyceps are provided

The Azimuthal Decorrelation of Jets Widely Separated in Rapidity

This study reports the first measurement of the azimuthal decorrelation between jets with pseudorapidity separation up to five units. The data were accumulated using the D{\O}detector during the 1992--1993 collider run of the Fermilab Tevatron at $\sqrt{s}=$ 1.8 TeV. These results are compared to next--to--leading order (NLO) QCD predictions and to two leading--log approximations (LLA) where the leading--log terms are resummed to all orders in $\alpha_{\scriptscriptstyle S}$. The final state jets as predicted by NLO QCD show less azimuthal decorrelation than the data. The parton showering LLA Monte Carlo {\small HERWIG} describes the data well; an analytical LLA prediction based on BFKL resummation shows more decorrelation than the data.Comment: 6 pages with 4 figures, all uuencoded and gzippe