The XMM-Newton serendipitous survey - II. First results from the AXIS high galactic latitude medium sensitivity survey

We present the first results on the identifications of a medium sensitivity survey (X-ray flux limit 2 x 10(-14) erg cm(-2) s(-1) in the 0.5-4.5 keV band) at high galactic latitude (\b\ > 20degrees) carried out with the XMM-Newton X-ray observatory within the AXIS observing programme. This study is being conducted as part of the XMM-Newton Survey Science Centre activities towards the identification of the sources in the X-ray serendipitous sky survey. The sample contains 29 X-ray sources in a solid angle of 0.26 deg(2) (source density 113 +/- 21 sources deg(-2)), out of which 27 (93%) have been identified. The majority of the sources are broad-line AGN (19), followed by narrow emission line X-ray emitting galaxies (6, all of which turn out to be AGN), 1 nearby non-emission line galaxy (NGC 4291) and 1 active coronal star. Among the identified sources we find 2 broad-absorption line QSOs (z similar to 1.8 and z similar to 1.9), which constitute similar to10% of the AGN population at this flux level, similar to optically selected samples. Identifications of a further 10 X-ray sources fainter than our survey limit are also presented

Measurement of b hadron lifetimes in exclusive decays containing a J/psi in p-pbar collisions at sqrt(s)=1.96TeV

We report on a measurement of $b$-hadron lifetimes in the fully reconstructed decay modes B^+ -->J/Psi K+, B^0 --> J/Psi K*, B^0 --> J/Psi Ks, and Lambda_b --> J/Psi Lambda using data corresponding to an integrated luminosity of 4.3 ${\rm fb}^{-1}$, collected by the CDF II detector at the Fermilab Tevatron. The measured lifetimes are $\tau$B^+ = $1.639 \pm 0.009 ({\rm stat}) \pm 0.009 {\rm (syst) ~ ps}$, $\tau$B^0 = $1.507 \pm 0.010 ({\rm stat}) \pm 0.008 {\rm (syst) ~ ps}$ and $\tau$Lambda_b = $1.537 \pm 0.045 ({\rm stat}) \pm 0.014 {\rm (syst) ~ ps}$. The lifetime ratios are $\tau$B^+/$\tau$B^0 = $1.088 \pm 0.009 ({\rm stat})\pm 0.004 ({\rm syst})$ and $\tau$Lambda_b/$\tau$B^0 = $1.020 \pm 0.030 ({\rm stat})\pm 0.008 ({\rm syst})$. These are the most precise determinations of these quantities from a single experiment.Comment: revised version. accepted for PRL publicatio

Measurement of ZZ production in leptonic final states at {\surd}s of 1.96 TeV at CDF

In this paper we present a precise measurement of the total ZZ production cross section in pp collisions at {\surd}s= 1.96 TeV, using data collected with the CDF II detector corresponding to an integrated luminosity of approximately 6 fb-1. The result is obtained by combining separate measurements in the four-charged (lll'l'), and two-charged-lepton and two-neutral-lepton (llvv) decay modes of the Z. The combined measured cross section for pp {\to} ZZ is 1.64^(+0.44)_(-0.38) pb. This is the most precise measurement of the ZZ production cross section in 1.96 TeV pp collisions to date.Comment: submitted to Phys. Rev. Let

Measurement of b Hadron Lifetimes in Exclusive Decays Containing a J/Psi in p(p)over-bar Collisions at root s=1.96 TeV

We report on a measurement of b-hadron lifetimes in the fully reconstructed decay modes B+-> J/psi K+, B-0 -> J/psi K*(892)(0), B-0 -> J/psi K-s(0), and Lambda(0)(b)-> J/psi Lambda(0) using data corresponding to an integrated luminosity of 4.3 fb(-1), collected by the CDF II detector at the Fermilab Tevatron. The measured lifetimes are tau(B+)=[1.639 +/- 0.009(stat)+/- 0.009(syst)]ps, tau(B-0)=[1.507 +/- 0.010(stat)+/- 0.008(syst)]ps, and tau(Lambda(0)(b))=[1.537 +/- 0.045(stat)+/- 0.014(syst)]ps. The lifetime ratios are tau(B+)/tau(B-0)=[1.088 +/- 0.009(stat)+/- 0.004(syst)] and tau(Lambda(0)(b))/tau(B-0)=[1.020 +/- 0.030(stat)+/- 0.008(syst)]. These are the most precise determinations of these quantities from a single experiment

Search for High Mass Resonances Decaying to Muon Pairs in root s=1.96 TeV p(p)over-bar Collisions

We present a search for a new narrow, spin-1, high mass resonance decaying to mu(+)mu(-) + X, using a matrix-element-based likelihood and a simultaneous measurement of the resonance mass and production rate. In data with 4.6 fb(-1) of integrated luminosity collected by the CDF detector in p (p) over bar collisions at root s = 1960 GeV, the most likely signal cross section is consistent with zero at 16% confidence level. We therefore do not observe evidence for a high mass resonance and place limits on models predicting spin-1 resonances, including M > 1071 GeV/c(2) at 95% confidence level for a Z' boson with the same couplings to fermions as the Z boson

Insights into the High-energy γ-ray Emission of Markarian 501 from Extensive Multifrequency Observations in the Fermi Era

We report on the γ-ray activity of the blazar Mrk501 during the first 480 days of Fermi operation. We find that the average Large Area Telescope (LAT) -ray spectrum of Mrk501 can be well described by a single power-law function with a photon index of 1.78 0.03. While we observe relatively mild flux variations with the Fermi-LAT (within less than a factor of two), we detect remarkable spectral variability where the hardest observed spectral index within the LAT energy range is 1.52 0.14, and the softest one is 2.51 0.20. These unexpected spectral changes do not correlate with the measured flux variations above 0.3GeV. In this paper, we also present the first results from the 4.5 month long multifrequency campaign (2009 March 15August 1) on Mrk501, which included the Very Long Baseline Array (VLBA), Swift, RXTE, MAGIC, and VERITAS, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign. The extensive radio to TeV data set from this campaign provides us with the most detailed spectral energy distribution yet collected for this source during its relatively low activity. The average spectral energy distribution of Mrk501 is well described by the standard one-zone synchrotron self-Compton (SSC) model. In the framework of this model, we find that the dominant emission region is characterized by a size r0.1pc (comparable within a factor of few to the size of the partially resolved VLBA core at 15-43 GHz), and that the total jet power (C1044ergs1) constitutes only a small fraction (<103) of the Eddington luminosity. The energy distribution of the freshly accelerated radiating electrons required to fit the time-averaged data has a broken power-law form in the energy range 0.3 GeV-10 TeV, with spectral indices 2.2 and 2.7 below and above the break energy of 20GeV. We argue that such a form is consistent with a scenario in which the bulk of the energy dissipation within the dominant emission zone of Mrk501 is due to relativistic, proton-mediated shocks. We find that the ultrarelativistic electrons and mildly relativistic protons within the blazar zone, if comparable in number, are in approximate energy equipartition, with their energy dominating the jet magnetic field energy by about two orders of magnitude

Photometric redshifts from reconstructed quasar templates

From Sloan Digital Sky Survey (SDSS) commissioning photometric and spectroscopic data, we investigate the utility of photometric redshift techniques in the task of estimating QSO redshifts. We consider empirical methods (e.g., nearest neighbor searches and polynomial fitting), standard spectral template fitting, and hybrid approaches (i.e., training spectral templates from spectroscopic and photometric observations of QSOs). We find that in all cases, because of the presence of strong emission lines within the QSO spectra, the nearest neighbor and template-fitting methods are superior to the polynomial-fitting approach. Applying a novel reconstruction technique, we can, from the SDSS multicolor photometry, reconstruct a statistical representation of the underlying SEDs of the SDSS QSOs. Although the reconstructed templates are based on only broadband photometry, the common emission lines present within the QSO spectra can be recovered in the resulting spectral energy distributions. The technique should be useful in searching for spectral differences among QSOs at a given redshift, in searching for spectral evolution of QSOs, in comparing photometric redshifts for objects beyond the SDSS spectroscopic sample with those in the well-calibrated photometric redshifts for objects brighter than 20th magnitude, and in searching for systematic and time-variable effects in the SDSS broadband photometric and spectral photometric calibrations

The extended Chandra Deep Field-South survey: Chandra point-source catalogs

We present Chandra point-source catalogs for the Extended Chandra Deep Field - South (E-CDF-S) survey. The E-CDF-S consists of four contiguous 250 ks Chandra observations covering an approximately square region of total solid angle approximate to 0.3 deg(2), which flank the existing approximate to 1 Ms Chandra Deep Field - South (CDF-S). The survey reaches sensitivity limits of approximate to 1.1 x 10(-16) and approximate to 6.7 x 10(-16) ergs cm(-2) s(-1) for the 0.5 - 2.0 and 2 - 8 keV bands, respectively. We detect 762 distinct X-ray point sources within the E-CDF-S exposure; 589 of these sources are new (i.e., not previously detected in the approximate to 1 Ms CDF-S). This brings the total number of X-ray point sources detected in the E-CDF-S region to 915 ( via the E-CDF-S and approximate to 1 Ms CDF-S observations). Source positions are determined using matched-filter and centroiding techniques; the median positional uncertainty is approximate to 0.'' 35. The basic X-ray and optical properties of these sources indicate a variety of source types, although absorbed active galactic nuclei (AGNs) seem to dominate. In addition to our main Chandra catalog, we constructed a supplementary source catalog containing 33 lower significance X-ray point sources that have bright optical counterparts ( R < 23). These sources generally have X-ray - to - optical flux ratios expected for normal and starburst galaxies, which lack a strong AGN component. We present basic number-count results for our main Chandra catalog and find good agreement with the approximate to 1 Ms CDF-S for sources with 0.5 - 2.0 and 2 - 8 keV fluxes greater than 3 x 10(-16) and 1 x 10(-15) ergs cm(-2) s(-1), respectively. Furthermore, three extended sources are detected in the 0.5 - 2.0 keV band, which are found to be likely associated with galaxy groups or poor clusters at z approximate to 0.1-0.7; these have typical rest-frame 0.5 - 2.0 keV luminosities of (1-5) x 10(42) ergs s(-1)

A survey of z > 5.7 quasars in the sloan digital sky survey. III. Discovery of five additional quasars

We present the discovery of five new quasars at z > 5.7, selected from the multicolor imaging data of the Sloan Digital Sky Survey (SDSS). Three of them, at redshifts 5.93, 6.07, and 6.22, were selected from similar to1700 deg(2) of new SDSS Main Survey imaging in the northern Galactic cap. An additional quasar, at redshift 5.85, was discovered by co-adding the data obtained in the Fall Equatorial Stripe in the SDSS Southern Survey Region. The fifth object, at redshift 5.80, is selected from a nonstandard SDSS scan in the southern Galactic cap outside the Main Survey area. The spectrum of SDSS J162331.81+ 311200.5 ( z = 6.22) shows a complete Gunn-Peterson trough at z(abs) > 5.95, similar to the troughs detected in the other three z greater than or similar to 6.2 quasars known. We present a composite spectrum of the z > 5.7 quasars discovered in the SDSS to date. The average emission-line and continuum properties of z similar to 6 quasars exhibit no significant evolution compared with those at low redshift. Using a complete sample of nine z > 5.7 quasars, we find that the density of quasars with M-1450 < -26.7 at z similar to 6 is (6 +/- 2) x 10(-10) Mpc(-3) (H-0 = 65 km s(-1) Mpc(-1), Omega = 0.35, and Lambda = 0.65), consistent with our previous estimates. The luminosity distribution of the sample is fitted with a power-law luminosity function Psi( L) proportional to L-3.2 +/- 0.7, somewhat steeper than but consistent with our previous estimates

Broad absorption line quasars in the Sloan Digital Sky Survey with VLA first radio detections

We present 13 broad absorption line (BAL) quasars, including 12 new objects, identified in the Sloan Digital Sky Survey (SDSS) and matched within 2 " to sources in the FIRST radio survey catalog. The surface density of this sample of radio-detected BAL quasars is 4.5 +/- 1.2 per 100 deg(2), i.e., approximately 4 times as high as previously found by the shallower FIRST Bright Quasar Survey (FBQS). A majority of these radio-detected BAL quasars are moderately radio-loud objects. The fraction of BAL quasars in the entire radio quasar sample, 4.8% +/- 1.3%, is comparable to the fraction of BAL quasars among the SDSS optical quasar sample (ignoring selection effects). We estimate that the true fraction of BAL quasars (mostly "HiBALs") in the radio sample is 9.2% +/- 2.6%, once selection effects are accounted for. We caution that the absorption troughs of four of the 13 radio-detected quasars considered do not strictly satisfy the standard BALnicity criteria. One or possibly two of the new radio-detected BAL quasars are of the rare "FeLoBAL" type. BAL quasars are generally redder than the median SDSS quasar at the same redshift