Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

Measurement of event-shape observables in Z→ℓ+ℓ− events in pp collisions at √ s=7 TeV with the ATLAS detector at the LHC

Event-shape observables measured using charged particles in inclusive $Z$-boson events are presented, using the electron and muon decay modes of the $Z$ bosons. The measurements are based on an integrated luminosity of $1.1 {\rm fb}^{-1}$ of proton--proton collisions recorded by the ATLAS detector at the LHC at a centre-of-mass energy $\sqrt{s}=7$ TeV. Charged-particle distributions, excluding the lepton--antilepton pair from the $Z$-boson decay, are measured in different ranges of transverse momentum of the $Z$ boson. Distributions include multiplicity, scalar sum of transverse momenta, beam thrust, transverse thrust, spherocity, and $\mathcal{F}$-parameter, which are in particular sensitive to properties of the underlying event at small values of the $Z$-boson transverse momentum. The Sherpa event generator shows larger deviations from the measured observables than Pythia8 and Herwig7. Typically, all three Monte Carlo generators provide predictions that are in better agreement with the data at high $Z$-boson transverse momenta than at low $Z$-boson transverse momenta and for the observables that are less sensitive to the number of charged particles in the event.Comment: 36 pages plus author list + cover page (54 pages total), 14 figures, 4 tables, submitted to EPJC, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2014-0

Spatial and temporal variation of microstimulation thresholds for inhibiting the tail-flick reflex from the rat's rostral medial medulla

Suppression of the tail-flick reflex by microstimulation of the rostral medial medulla in rats lightly anesthetized with barbiturates was studied with regard to spatial and temporal variations in electrical threshold. Trains of constant-current pulses with linearly descending amplitudes (called ‘ramps’) were passed through the extracellular brain microelectrode during noxious heating of the tail. The pulse amplitude at the time of the reflex, after allowance for conduction and reaction latencies, was taken as the threshold reading. This new method revealed a range of vertical electrode positions corresponding roughly to the nucleus raphe magnus, where the thresholds tended to be lowest (a mean of 4.1 μA for 0.4-ms pulses delivered at 50 Hz). In confirmation of the technique's validity neither the duration of the ramp nor its starting amplitude, within their useful range, significantly affected the measured threshold. Pronounced temporal fluctuation was seen in thresholds measured every 2 min. Spatial variability within the low-threshold region and differences between preparations were statistically much smaller sources of variation. The temporal fluctuation appeared to have a stationary mean for at least 20 min under constant conditions of anesthesia. In some experiments, action potentials from single neurons were recorded through the stimulating electrode, and classified into those inhibited during the tail-flick (off-cells), those excited (on-cells), and those unaffected (neutral cells). The thresholds where off-cells exhibited their maximum action potential were on average significantly lower than corresponding thresholds for on-cells. Short-range (<0.2mm) spatial variations in the threshold appeared however to be uncorrelated with the distance to an individual recorded off-cell or on-cell. The temporal fluctuations are suggested to reflect the profound cyclical changes in firing state of off-cells and on-cells that have been reported previously from barbiturate-anesthetized rats

Molecular Markers of Biomass Burning in Arctic Aerosols

Biomass burning is one of the most important\ud sources of organic matter in the atmosphere as it affects the\ud absorption and scattering of solar radiation, creates cloud\ud condensation nuclei and possibly influences ice and snow\ud albedo. Here we created and validated an analytical method\ud using HPLC/(−)-ESI-MS/MS to determine phenolic compounds\ud (PCLCs): vanillic acid, isovanillic acid, homovanillic\ud acid, syringic acid, syringaldehyde, ferulic acid, p-coumaric acid,\ud and coniferyl aldehyde at trace levels in particulate matter. We\ud analyzed eighteen high-volume air samples from Ny Ålesund\ud (Svalbard) collected during the boreal spring and summer of\ud 2010. Biomass burning molecules including PCLCs (<0.49\ud μm, mean atmospheric concentration 6 pg m−3), levoglucosan\ud (0.004 to 0.682 ng m−3) and acrylamide (32 fg m−3 to 166 fg m−3) were present in the sampled aerosols. Levoglucosan\ud concentrations, an unambiguous cellulose combustion tracer, derived from 2010 Russian fires. PCLCs levels in the Ny Alesund\ud atmosphere in different size fractions reflected both long-range transport linked to biomass burning and a terrigenous local\ud source

Is the L a meson?

The Kππ enhancement at 1780 MeV (the "L meson") is copiously produced in our K+p experiment at 12 GeV/c. We show that this "meson" can be explained as a threshold enhancement in the KN(1420)π system. We see no evidence for this enhancement in channels other than KN(1420)π. © 1969 The American Physical Society.SCOPUS: ar.jinfo:eu-repo/semantics/publishe