Rubin-LSST

Abstract:

21 cm intensity mapping experiments aim to observe the diffuse neutral hydrogen (HI) distribution on large scales which traces the Cosmic structure. The Square Kilometre Array (SKA) will have the capacity to measure the 21 cm signal over a large fraction of the sky. However, the redshifted 21 cm signal in the respective frequencies is faint compared to the Galactic foregrounds produced by synchrotron and free-free electron emission. In this article, we review selected foreground subtraction methods suggested to effectively separate the 21 cm signal from the foregrounds with intensity mapping simulations or data. We simulate an intensity mapping experiment feasible with SKA phase 1 including extragalactic and Galactic foregrounds. We give an example of the residuals of the foreground subtraction with a independent component analysis and show that the angular power spectrum is recovered within the statistical errors on most scales. Additionally, the scale of the Baryon Acoustic Oscillations is shown to be unaffected by foreground subtraction.

Abstract:

This chapter describes the assumed specifications and sensitivities for HI galaxy surveys with SKA1 and SKA2. It addresses the expected galaxy number densities based on available simulations as well as the clustering bias over the underlying dark matter. It is shown that a SKA1 HI galaxy survey should be able to find around 5×106 galaxies over 5,000 deg2 (up to z ∼ 0:8), while SKA2 should find ∼ 109 galaxies over 30,000 deg2 (up to z ∼ 2:5). The numbers presented here have been used throughout the cosmology chapters for forecasting.

Abstract:

Coma is frequently used as the archetype z ∼ 0 galaxy cluster to compare higher redshift work against. It is not clear, however, how representative the Coma cluster is for galaxy clusters of its mass or X-ray luminosity, and significantly, recent works have suggested that the galaxy population of Coma may be in some ways anomalous. In this work, we present a comparison of Coma to an X-ray-selected control sample of clusters. We show that although Coma is typical against the control sample in terms of its internal kinematics (sub-structure and velocity dispersion profile), it has a significantly high (∼3σ) X-ray temperature set against clusters of comparable mass. By de-redshifting our control sample cluster galaxies star formation rates using a fit to the galaxy main-sequence evolution at z < 0.1, we determine that the typical star formation rate of Coma galaxies as a function of mass is higher than for galaxies in our control sample at a confidence level of >99 per cent. One way to alleviate this discrepancy and bring Coma in line with the control sample would be to have the distance to Coma to be slightly lower, perhaps through a non-negligible peculiar velocity with respect to the Hubble expansion, but we do not regard this as likely given precision measurements using a variety of approaches. Therefore, in summary, we urge caution in using Coma as a z ∼ 0 baseline cluster in galaxy evolution studies. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Abstract:

A search for the standard model Higgs boson decaying to a W-boson pair at the LHC is reported. The event sample corresponds to an integrated luminosity of 4.9 fb-1 and 19.4 fb-1 collected with the CMS detector in pp collisions at √ s = 7 and 8 TeV, respectively. The Higgs boson candidates are selected in events with two or three charged leptons. An excess of events above background is observed, consistent with the expectation from the standard model Higgs boson with a mass of around 125 GeV. The probability to observe an excess equal or larger than the one seen, under the background-only hypothesis, corresponds to a significance of 4.3 standard deviations for m H = 125.6 GeV. The observed signal cross section times the branching fraction to WW for m H = 125.6 GeV is 0.72-0.18+0.20 times the standard model expectation. The spin-parity J P = 0+ hypothesis is favored against a narrow resonance with J P = 2+ or J P = 0- that decays to a W-boson pair. This result provides strong evidence for a Higgs-like boson decaying to a W-boson pair. [Figure not available: see fulltext.] © 2014 Cern for the benefit of the CMS collaboration.

Abstract:

Measurements are presented of the associated production of a W boson and a charm-quark jet (W + c) in pp collisions at a center-of-mass energy of 7 TeV. The analysis is conducted with a data sample corresponding to a total integrated luminosity of 5 fb−1, collected by the CMS detector at the LHC. W boson candidates are identified by their decay into a charged lepton (muon or electron) and a neutrino. The W + c measurements are performed for charm-quark jets in the kinematic region p jet T > 25 GeV, |ηjet| < 2.5, for two different thresholds for the transverse momentum of the lepton from the W-boson decay, and in the pseudorapidity range |ηℓ| < 2.1. Hadronic and inclusive semileptonic decays of charm hadrons are used to measure the following total cross sections: σ(pp → W + c + X) × B(W → ℓν) = 107.7 ± 3.3 (stat.) ± 6.9 (syst.) pb (p ℓ T > 25 GeV) and σ(pp → W + c + X)×B(W → ℓν) = 84.1 ± 2.0 (stat.) ± 4.9 (syst.) pb (p ℓ T > 35 GeV), and the cross section ratios σ(pp → W+ + ¯ c + X)/σ(pp → W− + c + X) = 0.954 ± 0.025 (stat.) ± 0.004 (syst.) (p ℓ T > 25 GeV) and σ(pp → W+ + ¯ c + X)/σ(pp → W− + c + X) = 0.938 ± 0.019 (stat.) ± 0.006 (syst.) (p ℓ T > 35 GeV). Cross sections and cross section ratios are also measured differentially with respect to the absolute value of the pseudorapidity of the lepton from the W-boson decay. These are the first measurements from the LHC directly sensitive to the strange quark and antiquark content of the proton. Results are compared with theoretical predictions and are consistent with the predictions based on global fits of parton distribution functions.