Properties of Intra-group Stars and Galaxies in Galaxy Groups: "Normal" versus "Fossil" Groups

Cosmological LCDM simulations of 12 M_vir~10^14 Msun galaxy groups have been performed, invoking star formation, chemical evolution with non-instantaneous recycling, metallicity dependent radiative cooling, strong star-burst driven galactic super-winds and effects of a meta-galactic UV field. At z=0, intra-group light (IGL) fractions are found to be 12-45%. Low values refer to groups with only a small difference between the R-band magnitudes of the first and second ranked group galaxy, large are typical of "fossil" groups (FGs). The IG stars in the 4 FGs are 0.3-0.5 Gyr older than in the 8 nonFGs. For the IGL, B-R=~1.4, in good agreement with observations. For FGs/nonFGs the iron abundance of the IG stars is slightly sub-solar in the central parts (r~100 kpc) decreasing to about 40% solar at about 0.5 r_vir The IG stars are alpha-element enhanced with [O/Fe] increasing with r, and an overall [O/Fe]~0.45, indicating predominant SNII enrichment. The velocity distributions of the IG stars and group galaxies are, at r>~30 kpc, significantly more radially anisotropic for FGs than for nonFGs. So a characteristic of FG formation, apart from formation time (D'Onghia et al.), may be the "initial" velocity distribution of the group galaxies. For FGs one can dynamically infer the (dark matter dominated) mass distribution of the groups all the way to r_vir, from the kinematics of the IG stars or group galaxies. For the nonFGs this method overestimates the group mass at r>~200 kpc, by up to a factor of two at r_vir. This is interpreted as FGs being, in general, more relaxed than nonFGs. Finally, FGs of the above M_vir should host ~500 planetary nebulae at projected distances between 100 and 1000 kpc from the first ranked galaxy. All results appear consistent with the FG formation scenario of D'Onghia et al.Comment: 12 pages, 15 figures, Accepted for MNRAS, Printing in colour recommende

Recent Results from the SAFIR Project

The "Seyfert and star formation Activity in the Far-Infrared" (SAFIR) project is aimed at studying the physical nature of the nuclear IR emission and star formation properties of a small sample of nearby Seyfert galaxies observed with the PACS and SPIRE instruments on board the Herschel space observatory. In this paper, we review the achieved results, that reveal the importance of the far-IR range to improve the quality and reliability of the estimates of basic AGN torus parameters, and describe some preliminary outcome from the on-going work on the dust properties of resolved AGN host galaxies

Recent Results from the SAFIR Project

The "Seyfert and star formation Activity in the Far-Infrared" (SAFIR) project is aimed at studying the physical nature of the nuclear IR emission and star formation properties of a small sample of nearby Seyfert galaxies observed with the PACS and SPIRE instruments on board the Herschel space observatory. In this paper, we review the achieved results, that reveal the importance of the far-IR range to improve the quality and reliability of the estimates of basic AGN torus parameters, and describe some preliminary outcome from the on-going work on the dust properties of resolved AGN host galaxies

Measurement of dielectron production in central Pb-Pb collisions at sNN =2.76 TeV

The first measurement of dielectron (e(+)e(-)) production in central (0-10\%) Pb-Pb collisions at root S-NN = 2.76 TeV at the LHC is presented. The dielectron invariant-mass spectrum is compared to the expected contributions from hadron decays in the invariant-mass range 0 < m(ee) < 3.5 GeV/c(2). The ratio of data and the cocktail of hadronic contributions without vacuum rho(0) is measured in the invariant-mass range 0.15 < m(ee) < 0.7 GeV/c(2), where an excess of dielectrons is observed in other experiments, and its value is 1.40 +/- 0.28 (stat.) +/- 0.08 (syst.) +/- 0.27 (cocktail). The dielectron spectrum measured in the invariant mass range 0 < m(ee) < 1 GeV/c(2) is consistent with the predictions from two theoretical model calculations that include thermal dielectron production from both partonic and hadronic phases with in-medium broadened rho(0) meson. The fraction of direct virtual photons over inclusive virtual photons is extracted for dielectron pairs with invariant mass 0.1 < m(ee) < 0.3 GeV/c(2) and in the transverse-momentum intervals 1 <( )p(T,ee) < 2 GeV/c and 2 < p(T,ee) < 4 GeV/c. The measured fraction of virtual direct photons is consistent with the measurement of real direct photons by ALICE and with the expectations from previous dielectron measurements at RHIC within the experimental uncertainties

A novel three degrees of freedom partially decoupled robot with linear actuators

In this work, a new translational robot formed with two different parallel manipulators with a common control point is introduced. An asymmetric parallel manipulator provides three translational degrees of freedom to the proposed robot while the orientation of the end-effector platform is kept constant by means of a Delta-like manipulator. An exact solution is easily derived to solve the forward displacement analysis while a semi-closed form solution is available for solving the inverse displacement analysis. The infinitesimal kinematics of the robot is approached by applying the theory of screws. Finally, a numerical example that consists of solving the inverse/forward displacement analysis as well as the forward acceleration analysis of the end-effector platform is presented. The example also includes the computation of the workspace and the direct/inverse singularities of the example