Rubin-LSST

Abstract:

We present results from an ongoing investigation using the Kilo Degree Survey (KiDS) on the VLT Survey Telescope (VST) to provide a census of ultra-compact massive galaxies (UCMGs), defined as galaxies with stellar masses M* > 8 × 1010M⊙ and effective radii Re < 1.5 kpc. UCMGs, which are expected to have undergone very few merger events, provide a unique view on the accretion history of the most massive galaxies in the Universe. Over an effective sky area of nearly 330 deg2, we select UCMG candidates from KiDS multicolour images, which provide high quality structural parameters, photometric redshifts, and stellar masses. Our sample of ~1000 photometrically selected UCMGs at z < 0.5 represents the largest sample of UCMG candidates assembled to date over the largest sky area. In this paper, we present the first effort to obtain their redshifts using different facilities, starting with first results for 28 candidates with redshifts z < 0.5, obtained at NTT and TNG telescopes.We confirmed, as bona fide UCMGs, 19 out of the 28 candidates with new redshifts. A further 46 UCMG candidates are confirmed with literature spectroscopic redshifts (35 at z < 0.5), bringing the final cumulative sample of spectroscopically confirmed lower-z UCMGs to 54 galaxies, which is the largest sample at redshifts below 0.5. We use these spectroscopic redshifts to quantify systematic errors in our photometric selection, and use these to correct our UCMG number counts. We finally compare the results to independent data sets and simulations.

Abstract:

A combined measurement of differential and inclusive total cross sections of Higgs boson production is performed using 36.1 fb−1 of 13 TeV proton–proton collision data produced by the LHC and recorded by the ATLAS detector in 2015 and 2016. Cross sections are obtained from measured H→γγ and H→ZZ⁎→4ℓ event yields, which are combined taking into account detector efficiencies, resolution, acceptances and branching fractions. The total Higgs boson production cross section is measured to be 57.0−5.9+6.0 (stat.) −3.3+4.0 (syst.) pb, in agreement with the Standard Model prediction. Differential cross-section measurements are presented for the Higgs boson transverse momentum distribution, Higgs boson rapidity, number of jets produced together with the Higgs boson, and the transverse momentum of the leading jet. The results from the two decay channels are found to be compatible, and their combination agrees with the Standard Model predictions.