14588387
Galaxy groups in the 2dF Galaxy Redshift Survey: galaxy spectral type segregation in groups
The behaviour of the relative fraction of galaxies with different spectral types in groups is analysed as a function of projected local galaxy density and the group-centric distance. The group sample was taken from the 2dF Group Galaxy Calatogue constructed by Merchan & Zandivarez. Our group sample was constrained to have a homogeneous virial mass distribution with redshift. Galaxies belonging to this group sample were selected in order to minimize possible biases, such as preferential selection of high-luminosity objects. We find a clear distinction between high virial mass groups (MV≳ 1013.5 M⊙) and the less massive ones. While the massive groups show a significant dependence of the relative fraction of low star formation galaxies on local galaxy density and group-centric radius, groups with lower masses show no significant trends. We also cross-correlate our group subsample with the previously identified clusters, finding that this sample shows a very similar behaviour to that observed in the high virial mass group subsample.
118533903
The dynamical state of galaxy groups and their luminosity content
We analyse the dependence of the luminosity function (LF) of galaxies in groups on group dynamical state. We use the Gaussianity of the velocity distribution of galaxy members as a measurement of the dynamical equilibrium of groups identified in the Sloan Digital Sky Survey Data Release 7 by Zandivarez & Martinez. We apply the Anderson–Darling goodness-of-fit test to distinguish between groups according to whether they have Gaussian or non-Gaussian velocity distributions, i.e. whether they are relaxed or not. For these two subsamples, we compute the 0.1r-band LF as a function of group virial mass and group total luminosity. For massive groups, , we find statistically significant differences between the LF of the two subsamples: the LFs of groups that have Gaussian velocity distributions have a brighter characteristic absolute magnitude (∼0.3 mag) and a steeper faint-end slope (∼0.25). We detect a similar effect when comparing the LF of bright [] Gaussian and non-Gaussian groups. Our results indicate that, for massive/luminous groups, the dynamical state of the system is directly related to the luminosity of its galaxy members.
16676496
Clustering and Light Profiles of Galaxies in the Environment of 20 Ultra-Steep-Spectrum Radio Sources
We have analyzed galaxy properties in the neighborhood of 20 ultra–steep-spectrum (USS) radio sources taken from the Westerbork in the Southern Hemisphere (WISH) catalog of De Breuck and coworkers. Galaxies in these USS fields were identified in deep observations that were carried out in the K' band using the OSIRIS imager at the CTIO 4 m telescope. We find a statistically significant signal of clustering around our sample of USS sources. The angular extension of the detected USS source–galaxy clustering is θc ~ 20'', corresponding to a spatial scale of ~120 h-1 kpc, assuming the sources are at z ~ 1 in an Ωm = 0.3, ΩΛ = 0.7 model universe. These results are in agreement with those obtained by Best for radio galaxy–galaxy correlation, and Best and coworkers for radio-loud AGN–galaxy correlation. We have also analyzed the light distribution of the galaxies by fitting Sersic's law profiles. Our results show no significant dependence of the galaxy shape parameters on the projected distance to the USS source.
119301581
Rational approximations in analytic QCD
We consider the 'modified minimal analytic' (mMA) coupling that involves an infrared cut to the standard MA coupling. The mMA coupling is a Stieltjes function and, as a consequence, the paradiagonal Pad? approximants converge to the coupling in the entire Q2-plane except on the timelike semiaxis below the cut. The equivalence between the narrow width approximation of the discontinuity function of the coupling, on the one hand, and this Pad? (rational) approximation of the coupling, on the other hand, is shown. We approximate the analytic analogs of the higher powers of mMA coupling by rational functions in such a way that the singularity region is respected by the approximants. Several comparisons, for real and complex arguments Q2, between the exact and approximate expressions are made and the speed of convergence is discussed. Motivated by the success of these approximants, an improvement of the mMA coupling is suggested and possible uses in the reproduction of experimental data are discussed.
17723357
Galaxy groups in the 2dF Galaxy Redshift Survey: luminosity and mass statistics
Several statistics are applied to groups and galaxies in groups in the Two degree Field Galaxy Redshift Survey. Firstly we estimate the luminosity functions for different subsets of galaxies in groups. The results are well fitted by a Schechter function with parameters M ∗ 5log(h) = 19.90 ± 0.03 and � = 1.13 ± 0.02 for all galaxies in groups, which is quite consistent with the results by Norberg et al. for field galaxies. When considering the four different spectral types defined by Madgwick et al. we find that the characteristic magnitude is typically brighter than in the field. We also observe a steeper value, � = 0.76± 0.03, of the faint end slope for low star-forming galaxies when compared with the corresponding field value. This steepening is more conspicuous, � = 1.10 ± 0.06, for those galaxies in more massive groups (M � 10 14 h −1 M⊙) than the obtained in the lower mass subset, � = 0.71 ± 0.04 (M < 10 14 h −1 M⊙). Secondly, we compute group total luminosities using Moore, Frenk & White prescriptions. We define a flux-limited group sample using a new statistical tool developed by Rauzy. The resulting group sample is used to determine the group luminosity function finding a good agreement with previous determinations and semianalytical models.
118549208
An analytic Pade-motivated QCD coupling
We consider a modification of the Minimal Analytic (MA) coupling of Shirkov and Solovtsov. This modified MA (mMA) coupling reflects the desired analytic properties of the space‐like observables. We show that an approximation by Dirac deltas of its discontinuity function ρ is equivalent to a Pade (rational) approximation of the mMA coupling that keeps its analytic structure. We propose a modification to mMA that, as preliminary results indicate, could be an improvement in the evaluation of low‐energy observables compared with other analytic couplings.
122967003
Augmented reality aiding collimator exchange at the LHC
Novel Augmented Reality techniques have the potential to have a large positive impact on the way remote maintenance operations are carried out in hazardous areas, e.g. areas where radiation doses that imply careful planning and optimization of maintenance operations are present. This paper describes an Augmented Reality strategy, system and implementation for aiding the remote collimator exchange in the LHC, currently the world׳s largest and highest-energy particle accelerator. The proposed system relies on marker detection and multi-modal augmentation in real-time. A database system has been used to ensure flexibility. The system has been tested in a mock-up facility, showing real time performance and great potential for future use in the LHC. The technical-scientific difficulties identified during the development of the system and the proposed solutions described in this paper may help the development of future Augmented Reality systems for remote handling in scientific facilities.
56302496
Design, analysis, and fabrication of the APT cavities
The design for the superconducting cavities of the high-energy accelerator for the Accelerator Production of Tritium (APT) project has been extensively changed in the last two years. The original accelerator design incorporated 0.48 and 0.71 beta cavities with stiffeners, and a stainless-steel helium vessel. Today, the accelerator uses unstiffened 0.64 and 0.82 beta cavities, and a titanium helium vessel. This paper discusses the design process, including the supporting analyses, prototype cavities built, and the decisions made to support the current design. The design of the integrated cavity-helium vessel is presented. Future plans and testing for design validation are also discussed.
122910167
Implications of Yukawa textures in the neutral Higgs decays within the 2HDM–III
We discuss the implications of assuming a four–zero Yukawa ansatz for the neutral Higgs decays, within the context of the general 2–Higgs Doublet Model of type III. We begin by presenting a detailed analysis of the neutral Higgs boson couplings with fermions and gauge bosons and the resulting effects on its decays. In particular, we are interested on the possibility of the neutral Higgs boson production in current colliders.