Rubin-LSST

Abstract:

A search for narrow resonances with a mass of at least 1 TeV in the dijet mass spectrum is performed using pp collisions at s=7TeV corresponding to an integrated luminosity of 1 fb-1, collected by the CMS experiment at the LHC. No resonances are observed. Upper limits at the 95% confidence level are presented on the product of the resonance cross section, branching fraction into dijets, and acceptance, separately for decays into quark-quark, quark-gluon, and gluon-gluon pairs. The data exclude new particles predicted in the following models at the 95% confidence level: string resonances with mass less than 4.00 TeV, E6 diquarks with mass less than 3.52 TeV, excited quarks with mass less than 2.49 TeV, axigluons and colorons with mass less than 2.47 TeV, and W' bosons with mass less than 1.51 TeV. These results extend previous exclusions from the dijet mass search technique. © 2011 CERN.

Abstract:

A search for squarks and gluinos in final states containing jets, missing transverse momentum and no electrons or muons is presented. The data were recorded by the ATLAS experiment in √s=7 TeV proton-proton collisions at the Large Hadron Collider. No excess above the Standard Model background expectation was observed in 35 pb-1 of analysed data. Gluino masses below 500 GeV are excluded at the 95% confidence level in simplified models containing only squarks of the first two generations, a gluino octet and a massless neutralino. The exclusion increases to 870 GeV for equal mass squarks and gluinos. In MSUGRA/CMSSM models with tanβ=3, A0=0 and μ>0, squarks and gluinos of equal mass are excluded below 775 GeV. These are the most stringent limits to date. © 2011 CERN.

Abstract:

We present a search for galaxies at 7.6 < z < 9.8 using the latest Hubble Space Telescope/Wide Field Camera 3 (WFC3) near-infrared data, based on the Lyman-break technique. We search for galaxies which have large (Y-J) colours (the 'Y-drops') on account of the Lyman α forest absorption, and with (J-H) colours inconsistent with being low-redshift contaminants. We identify 24 candidates at redshift z≈ 8-9 (15 are robust and a further nine more marginal but consistent with being high redshift) over an area of ≈50arcmin2. Previous searches for Y-drops with WFC3 have focused only on the Hubble Ultra Deep Field, and our larger survey (involving two other nearby deep fields and a wider area survey) has trebled the number of robust Y-drop candidates. For the first time, we have sufficient z≈ 8-9 galaxies to fit both φ* and M* of the UV Schechter luminosity function. There is evidence for evolution in this luminosity function from z= 6-7 to z= 8-9, in the sense that there are fewer UV-bright galaxies at z≈ 8-9, consistent with an evolution mainly in M*. The candidate z≈ 8-9 galaxies we detect have insufficient ionizing flux to reionize the Universe, and it is probable that galaxies below our detection limit provide a significant UV contribution. The faint-end slope, α, is not well constrained. However, adopting a similar faint-end slope to that determined at z= 3-6 (α=-1.7) and a Salpeter initial mass function (IMF), then the ionizing photon budget still falls short if fesc < 0.5, even integrating down to MUV=-8. A steeper faint-end slope or a low-metallicity population (or a top-heavy IMF) might still provide sufficient photons for star-forming galaxies to reionize the Universe, but confirmation of this might have to await the James Webb Space Telescope. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.

Abstract:

The ATLAS3D project is a multiwavelength survey combined with a theoretical modelling effort. The observations span from the radio to the millimetre and optical, and provide multicolour imaging, two-dimensional kinematics of the atomic (Hi), molecular (CO) and ionized gas (Hβ, [Oiii] and [Ni]), together with the kinematics and population of the stars (Hβ, Fe5015 and Mg b), for a carefully selected, volume-limited (1.16 × 105Mpc3) sample of 260 early-type (elliptical E and lenticular S0) galaxies (ETGs). The models include semi-analytic, N-body binary mergers and cosmological simulations of galaxy formation. Here we present the science goals for the project and introduce the galaxy sample and the selection criteria. The sample consists of nearby (D < 42Mpc, |δ- 29°| < 35°, |b| > 15°) morphologically selected ETGs extracted from a parent sample of 871 galaxies (8 per cent E, 22 per cent S0 and 70 per cent spirals) brighter than MK < -21.5mag (stellar mass M{black star}≳ 6 ×109M⊙). We analyse possible selection biases and we conclude that the parent sample is essentially complete and statistically representative of the nearby galaxy population. We present the size-luminosity relation for the spirals and ETGs and show that the ETGs in the ATLAS3D sample define a tight red sequence in a colour-magnitude diagram, with few objects in the transition from the blue cloud. We describe the strategy of the SAURON integral field observations and the extraction of the stellar kinematics with the ppxf method. We find typical 1σ errors of ΔV≈ 6kms-1, Δσ≈ 7kms-1, Δh3≈Δh4≈ 0.03 in the mean velocity, the velocity dispersion and Gauss-Hermite (GH) moments for galaxies with effective dispersion σe≳ 120kms-1. For galaxies with lower σe (≈40 per cent of the sample) the GH moments are gradually penalized by ppxf towards zero to suppress the noise produced by the spectral undersampling and only V and σ can be measured. We give an overview of the characteristics of the other main data sets already available for our sample and of the ongoing modelling projects. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.

Abstract:

We use the ATLAS3D sample of 260 early-type galaxies to study the apparent kinematic misalignment angle, Ψ, defined as the angle between the photometric and kinematic major axes. We find that 71 per cent of nearby early-type galaxies are strictly aligned systems (Ψ≤ 5°), an additional 14 per cent have 5° < Ψ≤ 10° and 90 per cent of galaxies have Ψ≤ 15°. Taking into account measurement uncertainties, 90 per cent of galaxies can be considered aligned to better than 5°, suggesting that only a small fraction of early-type galaxies (∼10 per cent) are not consistent with the axisymmetry within the projected half-light radius. We identify morphological features such as bars and rings (30 per cent), dust structures (16 per cent), blue nuclear colours (6 per cent) and evidence of interactions (8 per cent) visible on ATLAS3D galaxies. We use kinemetry to analyse the mean velocity maps and separate galaxies into two broad types of regular and non-regular rotators. We find 82 per cent of regular rotators and 17 per cent of non-regular rotators, with two galaxies that we were not able to classify due to the poor data quality. The non-regular rotators are typically found in dense regions and are massive. We characterize the specific features in the mean velocity and velocity dispersion maps. The majority of galaxies do not have any specific features, but we highlight here the frequency of the kinematically distinct cores (7 per cent of galaxies) and the aligned double peaks in the velocity dispersion maps (4 per cent of galaxies). We separate galaxies into five kinematic groups based on the kinemetric features, which are then used to interpret the (Ψ-ε) diagram. Most of the galaxies that are misaligned have complex kinematics and are non-regular rotators. In addition, some show evidence of the interaction and might not be in equilibrium, while some are barred. While the trends are weak, there is a tendency that large values of Ψ are found in galaxies at intermediate environmental densities and among the most massive galaxies in the sample. Taking into account the kinematic alignment and the kinemetric analysis, the majority of early-type galaxies have velocity maps more similar to that of the spiral discs than to that of the remnants of equal-mass mergers. We suggest that the most common formation mechanism for early-type galaxies preserves the axisymmetry of the disc progenitors and their general kinematic properties. Less commonly, the formation process results in a triaxial galaxy with much lower net angular momentum. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.