The Compact Group of Galaxies HCG 31 is in an early phase of merging

We have obtained high spectral resolution (R = 45900) Fabry-Perot velocity maps of the Hickson Compact Group HCG 31 in order to revisit the important problem of the merger nature of the central object A+C and to derive the internal kinematics of the candidate tidal dwarf galaxies in this group. Our main findings are: (1) double kinematic components are present throughout the main body of A+C, which strongly suggests that this complex is an ongoing merger (2) regions $A2$ and E, to the east and south of complex A+C, present rotation patterns with velocity amplitudes of $\sim 25 km s^{-1}$ and they counterrotate with respect to A+C, (3) region F, which was previously thought to be the best example of a tidal dwarf galaxy in HCG 31, presents no rotation and negligible internal velocity dispersion, as is also the case for region $A1$. HCG 31 presents an undergoing merger in its center (A+C) and it is likely that it has suffered additional perturbations due to interactions with the nearby galaxies B, G and Q.Comment: 5 pages + figures - Accepted to ApJ Lette

A kinematic study of the irregular dwarf galaxy NGC 2366 using HI and Halpha observations

Abridged. Context. The metal content of dwarf galaxies and the metal enrichment of the intergalactic medium both suggest that mass loss from galaxies is a significant factor for the chemical evolution history of galaxies, in particular of dwarf galaxies. However, no clear evidence of a blow-away in local dwarf galaxies has been found so far. Aims. We therefore performed a detailed kinematic analysis of the neutral and ionised gas in the nearby star-forming irregular dwarf galaxy NGC 2366 in order to make predictions about the fate of the gas and to get a more complete picture of this galaxy. Methods. A deep Halpha image and Fabry-Perot interferometric data of NGC 2366 were obtained. They were complemented by HI synthesis data from the THINGS survey. We searched for line-splitting both in Halpha and HI by performing a Gaussian decomposition. To get an idea whether the expansion velocities are high enough for a gas blow-away, we used the pseudo-isothermal halo model, which gives us realistic values for the escape velocities of NGC 2366. The good data quality also allowed us to discuss some peculiarities of the morphology and the dynamics in NGC 2366. Results. A large red-shifted outflow north west of the giant extragalactic HII region with an expansion velocity of up to 50 km/s is found in Halpha, but not in HI. Additionally, a blue-shifted component north of the giant extragalactic HII region was detected both in Halpha and HI with an expansion velocity of up to 30 km/s. A comparison with the escape velocities of NGC 2366 reveals that the gas does not have enough kinetic energy to leave the gravitational potential.Comment: 15 pages, 14 figures, accepted for publication by A&

Longitudinal relationships between caloric expenditure and gray matter in the cardiovascular health study

Background: Physical activity (PA) can be neuroprotective and reduce the risk for Alzheimer’s disease (AD). In assessing physical activity, caloric expenditure is a proxy marker reflecting the sum total of multiple physical activity types conducted by an individual. Objective:To assess caloric expenditure, as a proxy marker of PA, as a predictive measure of gray matter (GM) volumes in the normal and cognitively impaired elderly persons. Methods: All subjects in this study were recruited from the Institutional Review Board approved Cardiovascular Health Study (CHS), a multisite population-based longitudinal study in persons aged 65 and older. We analyzed a sub-sample of CHS participants 876 subjects (mean age 78.3, 57.5% F, 42.5% M) who had i) energy output assessed as kilocalories (kcal) per week using the standardized Minnesota Leisure-Time Activities questionnaire, ii) cognitive assessments for clinical classification of normal cognition, mild cognitive impairment (MCI), and AD, and iii) volumetric MR imaging of the brain. Voxel-based morphometry modeled the relationship between kcal/week and GM volumes while accounting for standard covariates including head size, age, sex, white matter hyperintensity lesions, MCI or AD status, and site. Multiple comparisons were controlled using a False Discovery Rate of 5 percent. Results: Higher energy output, from a variety of physical activity types, was associated with larger GM volumes in frontal, temporal, and parietal lobes, as well as hippocampus, thalamus, and basal ganglia. High levels of caloric expenditure moderated neurodegeneration-associated volume loss in the precuneus, posterior cingulate, and cerebellar vermis. Conclusion:Increasing energy output from a variety of physical activities is related to larger gray matter volumes in the elderly, regardless of cognitive status.Cyrus A. Raji, David A. Merrill, Harris Eyre, Sravya Mallam, Nare Torosyan, Kirk I. Erickson, Oscar L. Lopez , James T. Becker, Owen T. Carmichael, H. Michael Gach, Paul M. Thompson, W.T. Longstreth, Jr. and Lewis H. Kulle

A new measurement of the properties of the rare decay K -> pi+ e+ e-

A large low-background sample of events (10300) has been collected for the rare decay of kaons in flight K+ -> pi+ e+ e- by experiment E865 at the Brookhaven AGS. The decay products were accepted by a broad band high-resolution charged particle spectrometer with particle identification. The branching ratio (2.94 +- 0.05(stat.) +- 0.13(syst.) +- 0.05(model))*10**{-7} was determined normalizing to events from the decay chain K+ -> pi+ pi0; pi0 -> e+ e- gamma. From the analysis of the decay distributions the vector nature of this decay is firmly established now, and limits on scalar and tensor contributions are deduced. From the (e+ e-) invariant mass distribution the decay form factor f(z)=f0(1+ delta*z) (z=M(ee)**2/m(K)**2) is determined with delta=2.14 +- 0.13 +- 0.15. Chiral QCD perturbation theory predictions for the form factor are also tested, and terms beyond leading order O(p**4) are found to be important.Comment: 4 pages, 5 figure

Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

This paper presents measurements of the $W^+ \rightarrow \mu^+\nu$ and $W^- \rightarrow \mu^-\nu$ cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

Combined QCD and electroweak analysis of HERA data

A simultaneous fit of parton distribution functions (PDFs) and electroweak parameters to HERA data on deep inelastic scattering is presented. The input data are the neutral current and charged current inclusive cross sections which were previously used in the QCD analysis leading to the HERAPDF2.0 PDFs. In addition, the polarisation of the electron beam was taken into account for the ZEUS data recorded between 2004 and 2007. Results on the vector and axial-vector couplings of the Z boson to u- and d-type quarks, on the value of the electroweak mixing angle and the mass of the W boson are presented. The values obtained for the electroweak parameters are in agreement with Standard Model predictions.Comment: 32 pages, 10 figures, accepted by Phys. Rev. D. Small corrections from proofing process and small change to Fig. 12 and Table

Improving the Louvain Algorithm for Community Detection with Modularity Maximization

International audienc

Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector

A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13  TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139  fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV