Rubin-LSST

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.

Abstract:

The distribution of dust in the ecliptic plane between 0.96 and 1.04 AU has been inferred from impacts on the two STEREO spacecraft through observation of secondary particle trails and unexpected off-points in the Heliospheric Imager (HI) cameras. This study made use of analysis carried out by members of a distributed web-based project, Solar Stormwatch. A comparison between observations of the brightest particle trails and a survey of fainter trails shows consistent distributions. While there is no obvious correlation between this distribution and the occurrence of individual meteor streams at Earth, there are some broad longitudinal features in these distributions that are also observed in sources of the sporadic meteor population. The asymmetry in the number of trails seen by each spacecraft and the fact that there are many more unexpected off-points in the HI-B than in HI-A, indicates that the majority of impacts are coming from the apex direction. For impacts causing off-points in the HI-B camera these dust particles are estimated to have masses in excess of 10-17 kg with radii exceeding 0.1 {\mu}m. For off-points observed in the HI-A images, which can only have been caused by particles travelling from the anti-apex direction, the distribution is consistent with that of secondary 'storm' trails observed by HI-B, providing evidence that these trails also result from impacts with primary particles from an anti-apex source. It is apparent that the differential mass index of particles from the apex direction is consistently above 2. This indicates that the majority of the mass is within the smaller particles of this population. In contrast, the differential mass index of particles from the anti-apex direction (causing off-points in HI-A) is consistently below 2, indicating that the majority of the mass is to be found in larger particles of this distribution.