arXiv subjects
Publications and source records attributed to M. D'Onofrio.
We present the most recent results on searches for squarks and gluinos in ppbar collisions at sqrt(s)=1.96 TeV, in events with large missing transverse energy, leptons and multiple jets in the final state, based on 1.8 to 2.8 fb-1 of data collected by the CDF Run II detector at the Tevatron. No evidence of new physics is found and exclusion limits in several MSSM scenarios are extracted.
We present preliminary results on a search for squarks and gluinos in proton-antiproton collisions with a center-of-mass energy of 1.96 TeV and based on about 2.0 fb-1 of data collected by the CDF detector in the Tevatron Run II. Events with multiple jets of hadrons and large missing transverse energy in the final state are studied within the framework of minimal supergravity (mSUGRA) and assuming R-parity conservation. The results are compared to Standard Model predictions and limits on gluino and squark masses are extracted. A specific search for the supersymmetric partner of the bottom quark produced from gluino decays is carried out using a sample of events with missing transverse energy and two or more jets, at least one of them b-tagged. Good agreement is found between data and Standard Model predictions, and limits on gluino and sbottom masses are extracted.
Inclusive jet cross sections in Z/γ^* events, with Z/γ^* decaying into an electron-positron pair, are measured as a function of jet transverse momentum and jet multiplicity in ppbar collisions at sqrt{s} = 1.96 TeV with the upgraded Collider Detector at Fermilab in Run II, based on an integrated luminosity of 2.5 fb-1. The measurements cover the rapidity region |yjet | < 2.1 and the transverse momentum range ptjet > 30 GeV/c. Next-to-leading order perturbative QCD predictions are in good agreement with the measured cross sections.
By exploting the data of three large surveys (WINGS, NFPS and SDSS), we present here a comparative analysis of the Fundamental Plane (FP hereafter) of the early-type galaxies (ETGs) belonging to 59 galaxy clusters in the redshift range $0.04<z<0.07$. We show that the variances of the distributions of the FP coefficients derived for the clusters in our sample are not consistent with the hypothesis of universality of the FP relation. By investigating the origin of such remarkable variances we find that, besides a couple of obvious factors, such as the adopted fitting technique and the method used to measure the photometric and kinematic variables, the coefficients of the FP are strongly influenced by a number of things, mainly related to the distribution of photometric/kinematic properties of galaxies in the particular sample under analysis. For instance, the $a$ coefficient derived for the whole sample of ETGs, turns out to decrease when faint galaxies are progressively removed from the sample, suggesting that bright and faint ETGs have systematically different FPs, likely because of different mechanisms of galaxy formation. In general, by comparing mock cluster samples with the real one, we conclude that the observed variances of the FP coefficients cannot be attributed just to statistical uncertainties. We speculate that the FP is actually a bent surface, which is approximated by different planes when different selection criteria, either chosen or induced by observations, are acting to define galaxies samples. We also find ...
[Abridged] The WIde-field Nearby Galaxy-cluster Survey (WINGS) is a project aiming at the study of the galaxy populations in clusters in the local universe (0.04<z<0.07) and the influence of environment on the physical properties of galaxies. This survey provides a high quality set of spectroscopic data for ~6000 galaxies in 48 clusters. A salient feature of this model is the possibility of treating dust extinction as a function of age, allowing younger stars to be more obscured than older ones. Our technique, for the first time, takes into account this feature in a spectral fitting code. A set of template spectra spanning a wide range of star formation histories is built, with features closely resembling those of typical spectra in our sample in terms of spectral resolution, noise and wavelength coverage. Our method of analyzing these spectra allows us to test the reliability and the uncertainties related to each physical parameter we are inferring. The well-known degeneracy problem, i.e. the non-uniqueness of the best fit solution (mass and extinction in different age bins), can be addressed by assigning adequate error bars to the recovered parameters. The values found in this way, together with their error bars, identify the region of parameter space which contains all the possible solutions for a given spectrum. A comparison test was also performed on a WINGS subsample, containing objects in common with the Sloan Digital Sky Survey, yielding excellent agreement. We find that the stellar content as a function of age is reliably recovered in four main age bins and that the uncertainties only mildly depend on the S/N ratio. The metallicity of the dominant stellar population is not always recoverable unambiguosly, depending on the Star Formation History pattern.
We search for and characterize substructures in the projected distribution of galaxies observed in the wide field CCD images of the 77 nearby clusters of the WIde-field Nearby Galaxy-cluster Survey (WINGS). This sample is complete in X-ray flux in the redshift range 0.04<z<0.07. We search for substructures in WINGS clusters with DEDICA, an adaptive-kernel procedure. We test the procedure on Monte-Carlo simulations of the observed frames and determine the reliability for the detected structures. DEDICA identifies at least one reliable structure in the field of 55 clusters. 40 of these clusters have a total of 69 substructures at the same redshift of the cluster (redshift estimates of substructures are from color-magnitude diagrams). The fraction of clusters with subclusters (73%) is higher than in most studies. The presence of subclusters affects the relative luminosities of the brightest cluster galaxies (BCGs). Down to L ~ 10^11.2 L_Sun, our observed differential distribution of subcluster luminosities is consistent with the theoretical prediction of the differential mass function of substructures in cosmological simulations.
A precise determination of the energy scale of jets at the Collider Detector at Fermilab at the Tevatron $p\bar{p}$ collider is described. Jets are used in many analyses to estimate the energies of partons resulting from the underlying physics process. Several correction factors are developed to estimate the original parton energy from the observed jet energy in the calorimeter. The jet energy response is compared between data and Monte Carlo simulation for various physics processes, and systematic uncertainties on the jet energy scale are determined. For jets with transverse momenta above 50 GeV the jet energy scale is determined with a 3% systematic uncertainty.
This is the first paper of a series that will present data and scientific results from the WINGS project, a wide-field, multiwavelength imaging and spectroscopic survey of galaxies in 77 nearby clusters. The sample was extracted from the ROSAT catalogs with constraints on the redshift (0.04 20). The global goal of the WINGS project is the systematic study of the local cosmic variance of the cluster population and of the properties of cluster galaxies as a function of cluster properties and local environment. This data collection will allow to define a local 'Zero-Point' reference against which to gauge the cosmic evolution when compared to more distant clusters. The core of the project consists of wide-field optical imaging of the selected clusters in the B and V bands. We have also completed a multi-fiber, medium resolution spectroscopic survey for 51 of the clusters in the master sample. In addition, a NIR (JK) survey of ~50 clusters and an H_alpha + UV survey of some 10 clusters are presently ongoing, while a very-wide-field optical survey has also been programmed. In this paper we briefly outline the global objectives and the main characteristics of the WINGS project. Moreover, the observing strategy and the data reduction of the optical imaging survey (WINGS-OPT) are presented. We have achieved a photometric accuracy of ~0.025mag, reaching completeness to V~23.5. Field size and resolution (FWHM) span the absolute intervals (1.6-2.7)Mpc and (0.7-1.7)kpc, respectively, depending on the redshift and on the seeing. This allows the planned studies to get a valuable description of the local properties of clusters and galaxies in clusters.
The properties of three-jet events with total transverse energy greater than 320 GeV and individual jet energy greater than 20 GeV have been analyzed and compared to absolute predictions from a next-to-leading order (NLO) perturbative QCD calculation. These data, of integrated luminosity 86 pb^-1, were recorded by the CDF Experiment for proton-antiproton collisions at sqrt{s}=1.8 TeV. This study tests a model of higher order QCD processes that result in gluon emission and can be used to estimate the magnitude of the contribution of processes higher than NLO. The total cross section is measured to be 466 +/- 3(stat.)^{+207}_{-70}(syst.) pb. The differential cross section is furthermore measured for all kinematically accessible regions of the Dalitz plane, including those for which the theoretical prediction is unreliable. While the measured cross section is consistent with the theoretical prediction in magnitude, the two differ somewhat in shape in the Dalitz plane.
We present new imaging and spectroscopic observations of the interacting system Arp 194 (= UGC 06945 = VV 126). The northern component (A194N) is a distorted spiral or ring galaxy likely disrupted by a collision or close encounter with a southern galaxy (A194S). There is evidence that a third galaxy with similar recession velocity is projected on A194N but its role is likely secondary. A194S is connected to A194N by a string of emission knots which motivates our interpretation that the former was the intruder. Three of the knots are easily discernible in B,R, and H-alpha images and are assumed to trace the path of the intruder following the encounter, which we estimate occurred a few 10^8 yr ago. Both A194S and N are experiencing strong bursts of star formation: the H-alpha luminosity indicates a total star formation rate ~ 10 solar masses per year. The lack of detectable J and K emission from the blobs, along with strong H-alpha emission, indicates that an evolved stellar population is not likely to be present. The brightest knot (closest to A194S) shows a star formation rate of ~1.2 solar masses per year which, if sustained over a time ~ 7 10^7 yr, could explain the spectral energy distribution. This suggests that the stripped matter was originally predominantly gaseous. The brightest knot is detected as a FIRST radio source and this is likely the signature of supernova remnants related to enhanced star formation. Motions in the gas between the brightest knot and A194S, traced by an emission line link of increasing radial velocity, suggests infall toward the center of the intruder. Arp 194 is therefore one of the few galaxies where evidence of ``cross-fueling'' is observed [LaTeX removed].
This is the first paper of a series investigating the scaling relations of early-type galaxies in clusters. Here we illustrate the multi-band imagery and the image reduction and calibration procedures relative to the whole sample of 22 clusters at 0.05 < z < 0.25. We also present the detailed surface photometry of 312 early-type galaxies in 7 clusters in the first redshift bin, z~0.025-0.075. We give for each galaxy the complete set of luminosity and geometrical profiles, and and a number of global, photometric and morphological parameters. They have been evaluated taking into account the effects of seeing. Internal consistency checks and comparisons with data in the literature confirm the quality of our analysis. These data, together with the spectroscopic ones presented in the second paper of the series, will provide the local calibration of the scaling relations.
We outline the results of a two-dimensional (2D) fit of the light distribution of early-type galaxies belonging to a complete volume-limited sample, and briefly discuss the significant correlations among the structural parameters. In particular we reconfirm that the lack of structural homology is likely a characteristic of hot stellar systems.
UGC 3995 is a close pair of spiral galaxies whose eastern component hosts a Seyfert 2 nucleus. We present a detailed analysis of this system using long slit spectroscopy and narrow (\ha + \nii) as well as broad band (B, R) imaging and an archive WFPC2 image. The component galaxies reveal surprisingly small signs of interaction considering their spatial proximity and almost identical recession velocities, as the bright filament is probably an optical illusion due to the superposition of the bar of the Seyfert galaxy and of the spiral arms of the companion. The broad band morphology, a B--R color map, and a continuum-subtracted \ha + \nii image demonstrate that the western component UGC 3995B is in front of the Seyfert-hosting component UGC 3995A, partly obscuring its western side. The small radial velocity difference leaves the relative motion of the two galaxies largely unconstrained. The observed lack of major tidal deformations, along with some morphological peculiarities, suggests that the galaxies are proximate in space but may have recently approached each other on the plane of the sky. The geometry of the system and the radial velocity curve at P. A. = 106 suggest that the encounter may be retrograde or, alternatively, prograde before perigalacticon. The partial overlap of the two galaxies allows us to estimate the optical thickness of the disk of component B. We derive an extinction = 0.18 visual magnitudes in the infra-arms parts of the foreground galaxy disk, and >= 1-1.5 visual magnitudes in correspondence of the spiral arms.
This is a multiband photometric and spectroscopic study of the peculiar S0 galaxy NGC128. We present results from broad (B and R) and narrow band optical CCD photometry, near (NIR) and far (FIR) infrared observations, long slit spectroscopy, and Fabry-Perot interferometry (CIGALE). The peculiar peanut shape morphology of the galaxy is observed both at optical and near-infrared wavelengths. The stellar disk is thick and distorted (arc-bended), with a color asymmetry along the major axis due to the presence of a large amount of dust, estimated through NIR and FIR data of ~6x10^6 M_sun, in the region of interaction with the companion galaxy NGC127. The color maps are nearly uniform over the whole galaxy, but for the major axis asymmetry, and a small gradient toward the center indicating the presence of a redder disk-like component. The H_alpha image indeed reveals the existence of a tilted gaseous ``disk'' around the center, oriented with the major axis toward the companion galaxy NGC127. Long slit and CIGALE data confirm the presence of gas in a disk-like component counter-rotating and inclined approximately of 50 deg. to the line of sight. The mass of the gas disk in the inner region is ~2.7x10^4 M_sun. The stellar velocity field is cylindrical up to the last measured points of the derived rotation curves, while the velocity dispersion profiles are typical for an S0 galaxy, but for an extended constant behaviour along the minor axis.
We derive the relative distances to the Virgo, Fornax, and Coma clusters of galaxies by applying the Dn-sigma and the Fundamental Plane (FP) relations to the data of the homogeneous samples of early--type galaxies studied by Caon etal, Lucey etal, and Jorgensen etal. The two distance indicators give consistent results, the relative distance moduli to Fornax and Coma with respect to Virgo being Dmu(FV)=0.45+-0.15 and Dmu(CV)=3.55+-0.15) respectively. The formal error on D(m-M) may be as small as 0.07 mag (~3% in distance), provided that all the sources of bias are taken into account and a correct statistical approach is used. Much of the actual uncertainty in the relative distance of the clusters (12-15%), is due to the existence of systematic departures in the measurements of the velocity dispersions among the various datasets, and to the corrections for aperture effects. The above result for the Fornax cluster is supported by the L-sigma-mu relation and, with lesser accuracy, by the log(m)-log(re) relations. Our value of Dmu(FV) is in fair agreement with the one derived using planetary nebulae and SNe-Ia, while is in open contrast with that coming from surface brightness fluctuations, globular clusters luminosity function, and infrared Tully-Fisher relation. In our data Coma appears slightly nearer than indicated by the other distance indicators, but now a better agreement with the Tully-Fisher relation seems to exist. Finally we found that there aren't correlations of the residuals of the Dn-sigma with the effective surface brightness, the total luminosity of the galaxies, with the ellipticity and the shape parameter a4. Instead a correlation seems to exists with maximum Vrot, with (V/sigma) and with the exponent m of the r^1/m fit to major axis light of galaxies.
Major axis rotation curves and velocity dispersions profiles, extending out to about one effective radius, are presented for 15 ellipticals and S0's out of the photometric sample of Fornax cluster galaxies studied by Caon \etal\ (1994). A brief description of the spectroscopic and photometric characteristics of each galaxy is provided, together with a comparison with previous studies. Six of the nine E's are possibly misclassified S0's or ellipticals harboring a disk-like component. Two galaxies (NGC~1399 and 1404) show a hint of counter-rotation. Evidence is given that the \bright\ and the \ordinary\ families of early-type galaxies, first introduced by Capaccioli \etal\ (1992), look distinct also in term of the anisotropy parameter $(\Vm/σ)^*$.
We have obtained the best fit to the light profiles of a luminosity limited sample of elliptical and S0 galaxies with a power law \rn, letting the exponent remain free rather than keeping it fixed at $1/n=1/4$ as in the well known \GV formula. The introduction of a free parameter in the fitting formula (ranging from $n=0.5$ for $<\re>=0.3$ kpc to $n=16$ for $<\re>=25$ kpc) is justified by the existence of a good correlation between $n$ and the global galaxian parameters, such as total luminosity and scale-radius. This result seems to be in line with the segregation of properties between the `ordinary' and `bright' families of early-type galaxies, and has consequence for the claimed independence of the shape of galaxy profiles with respect to the Fundamental Plane parameters.