Rubin-LSST

Abstract:

A measurement of inclusive W and Z production cross sections in pp collisions at √s = 7TeV is presented. The electron and muon decay channels are analyzed in a data sample collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 36 pb-1. The measured inclusive cross sections are σ(pp → WX) × ß(W → lν) = 10.31 × 0.02 (stat.) × 0.09 (syst.) × 0.10 (th.) × 0.41 (lumi.) nb and σ(pp → ZX) x B(Z → l +l- = 0.974 × 0.007 (stat.) × 0.007 (syst.) × 0.018 (th.) × 0.039 (lumi.) nb, limited to the dilepton invariant mass range 60 to 120 GeV. The luminosity-independent cross section ratios are (σ(pp → WX) × B(W → lv))/(σ(pp → ZX) × B(Z → l+l-)) = 10.54 × 0.07 (stat.) × 0.08 (syst.) × 0.16 (th.) and (σ(pp → W+X) × B(W+ → l+ν))/(σ(pp → W-X) × B(W- → l-v̄)) = 1.421×0.006 (stat.) ×0.014 (syst.) ×0.029 (th.). The measured values agree with next-to-next-to-leading order QCD cross section calculations based on recent parton distribution functions. Copyright CERN.

Abstract:

A search for events with jets and missing transverse energy is performed in a data sample of pp collisions collected at √s=7TeV by the CMS experiment at the LHC. The analyzed data sample corresponds to an integrated luminosity of 1.14fb-1. In this search, a kinematic variable αT is used as the main discriminator between events with genuine and misreconstructed missing transverse energy. No excess of events over the standard model expectation is found. Exclusion limits in the parameter space of the constrained minimal supersymmetric extension of the standard model are set. In this model, squark masses below 1.1 TeV are excluded at 95% C.L. Gluino masses below 1.1 TeV are also ruled out at 95% C.L. for values of the universal scalar mass parameter below 500 GeV. © 2011 CERN.

Abstract:

A subset of microquasars exhibits high peculiar velocity with respect to the local standard of rest due to the kicks they receive when being born in supernovae. The interaction between the radio plasma released by microquasar jets from such high-velocity binaries with the interstellar medium must lead to the production of trails and bow shocks similar to what is observed in narrow-angle tailed radio galaxies and pulsar wind nebulae. We present a set of numerical simulations of this interaction that illuminate the long-term dynamical evolution and the observational properties of these microquasar bow-shock nebulae and trails. We find that this interaction always produces a structure that consists of a bow shock, a trailing neck, and an expanding bubble. Using our simulations to model emission, we predict that the shock surrounding the bubble and the neck should be visible in Hα emission, the interior of the bubble should be visible in synchrotron radio emission, and only the bow shock is likely to be detectable in X-ray emission. We construct an analytic model for the evolution of the neck and bubble shape and compare this model with observations of the X-ray binary SAX J1712.6-3739. © 2011. The American Astronomical Society. All rights reserved.

Abstract:

Galaxy merging is a fundamental aspect of the standard hierarchical galaxy formation paradigm. Recently, the Galaxy Zoo project has compiled a large, homogeneous catalogue of 3373 mergers, through direct visual inspection of the entire SDSS spectro- scopic sample. We explore a subset of galaxies from this catalogue that are spheroidal 'post-mergers' (SPMs) - where a single remnant is in the final stages of relaxation after the merger and shows evidence for a dominant bulge, making them plausible progenitors of early-type galaxies. Our results indicate that the SPMs have bluer colours than the general early-type galaxy population possibly due to merger-induced star formation. An analysis using optical emission line ratios indicates that 20 of our SPMs exhibit LINER or Seyfert-like activity (68%), while the remaining 10 galaxies are classified as either star forming (16%) or quiescent (16%). A comparison to the emission line activity in the ongoing mergers from Darg et al. indicates that the AGN fraction rises in the post-mergers, suggesting that the AGN phase probably becomes dominant only in the very final stages of the merger process. The optical colours of the SPMs and the plausible mass ratios for their progenitors indicate that, while a minority are consistent with major mergers between two early-type galaxies, the vast majority are remnants of major mergers where at least one progenitor is a late-type galaxy.