A new sample of X-ray selected narrow emission-line galaxies. I. The nature of optically elusive AGN

Using the 3XMM catalogue of serendipitous X-ray sources, and the SDSS-DR9 spectroscopic catalogue, we have obtained a new sample of X-ray selected narrow emission line galaxies. The standard optical diagnostic diagram and selection by hard X-ray luminosity expose a mismatch between the optically-based and X-ray-based classifications. The nature of these misclassified elusive AGN can be understood in terms of their broader X-ray and optical properties and leads to a division of this sub-sample into two groups. A little more than half are likely to be narrow-line Seyfert 1s (NLS1s), so misclassified because of the contribution of the Broad Line Region (BLR) to their optical spectra. The remainder have some of the properties of Seyfert 2 (Sy2) AGN; their optical elusiveness can be explained by optical dilution from the host galaxy plus a star-formation contribution and by their underluminous optical emission due to low accretion rates. Because some of the Sy2 sources have very low accretion rates, are unabsorbed, plus the fact that they lack broad optical emission lines, they are good candidates to be True Sy2 AGN.Comment: 13 pages, 13 figues, accepted for publication in A&

Evidence for a large fraction of Compton-thick quasars at high redshift

Using mid-infrared and radio selection criteria, we pre-select a sample of candidate high-redshift type-2 quasars in the Subaru XMM-Newton Deep Field (SXDF). To filter out starburst contaminants, we use a bayesian method to fit the spectral energy distributions (SEDs) between 24-microns and B-band, obtain photometric redshifts, and identify the best candidates for high-z type-2 quasars. This leaves us with 12 z_phot >= 1.7 type-2 quasar candidates in an area ~0.8 deg^2, of which only two have secure X-ray detections. The two detected sources have estimated column densities N_H~2 & 3x10^27 m^-2, i.e. heavily obscured but Compton-thin quasars. Given the large bolometric luminosities and redshifts of the undetected objects, the lack of X-ray detections suggests extreme absorbing columns N_H >= 10^28 m^-2 are typical. We have found evidence for a population of ``Compton-thick'' high-redshift type-2 quasars, at least comparable to, and probably larger than the type-1 quasar population, although spectroscopic confirmation of their AGN nature is important.Comment: 6 pages, 2 colour figures. Accepted by MNRAS. Full resolution version and supplementary figures can be found at: http://www.mpia.de/homes/martinez/publications.htm

Comoving Space Density and Obscured Fraction of High-Redshift Active Galactic Nuclei in the Subaru/{\it XMM-Newton} Deep Survey

We study the comoving space density of X-ray-selected luminous active galactic nuclei (AGNs) and the obscured AGN fraction at high redshifts ($3 < z < 5$) in the Subaru/{\it XMM-Newton} Deep Survey (SXDS) field. From an X-ray source catalog with high completeness of optical identification thanks to deep optical images, we select a sample of 30 AGNs at $z > 3$ with intrinsic (de-absorbed and rest-frame 2--10 keV) luminosities of $L_{\rm X} = 10^{44-45}$ erg s$^{-1}$ detected in the 0.5--2 keV band, consisting of 20 and 10 objects with spectroscopic and photometric redshifts, respectively. Utilizing the $1/V_{\rm max}$ method, we confirm that the comoving space density of luminous AGNs decreases with redshift above $z > 3$. When combined with the {\it Chandra}-COSMOS result of Civano et al.\ (2011), the density decline of AGNs with $L_{\rm X} = 10^{44-45}$ erg s$^{-1}$ is well represented by a power law of $(1 + z)^{-6.2 \pm 0.9}$. We also determine the fraction of X-ray obscured AGNs with $N_{\rm H} > 10^{22}$ cm$^{-2}$ in the Compton-thin population to be 0.54$^{+0.17}_{-0.19}$, by carefully taking into account observational biases including the effects of photon statistics for each source. This result is consistent with an independent determination of the type-2 AGN fraction based on optical properties, for which the fraction is found to be 0.59$\pm$0.09. Comparing our result with that obtained in the local Universe, we conclude that the obscured fraction of luminous AGNs increases significantly from $z=0$ to $z>3$ by a factor of 2.5$\pm$1.1.Comment: 12 pages, 12 figures, 1 table. Accepted for publication in Ap

First Light from the Far-Infrared Spectroscopy of the Troposphere (FIRST) Instrument

We present first light spectra from the new Far-Infrared Spectroscopy of the Troposphere (FIRST) instrument. FIRST is a Fourier Transform Spectrometer developed to measure accurately the far-infrared (15 to 100 micrometers; 650 to 100 wavenumbers) emission spectrum of the Earth and its atmosphere. The observations presented here were obtained during a high altitude balloon flight from Ft. Sumner, New Mexico on 7 June 2005. The flight data demonstrate the instrument's ability to observe the entire energetically significant infrared emission spectrum (50 to 2000 wavenumbers) at high spectral and spatial resolution on a single focal plane in an instrument with one broad spectral bandpass beamsplitter. Comparisons with radiative transfer calculations demonstrate that FIRST accurately observes the very fine spectral structure in the far-infrared. Comparisons of the atmospheric window radiances measured by FIRST and by instruments on the NASA Aqua satellite that overflew FIRST are in excellent agreement. FIRST opens a new window on the spectrum that can be used for studying atmospheric radiation and climate, cirrus clouds, and water vapor in the upper troposphere

G313.3+00.3: A New Planetary Nebula discovered by the Australia Telescope Compact Array and the Spitzer Space Telescope

We present a new planetary nebula, first identified in images from the Australia Telescope Compact Array, although not recognized at that time. Recent observations with the Spitzer Space Telescope during the GLIMPSE Legacy program have rediscovered the object. The high-resolution radio and infrared images enable the identification of the central star or its wind, the recognition of the radio emission as thermal, and the probable presence of polycylic aromatic hydrocarbons in and around the source. These lead to the conclusion that G313.3+00.3 is a planetary nebula. This object is of particular interest because it was discovered solely through radio and mid-infrared imaging, without any optical (or near-infrared) confirmation, and acts as a proof of concept for the discovery of many more highly extinguished planetary nebulae. G313.3+00.3 is well-resolved by both the instruments with which it was identified, and suffers extreme reddening due to its location in the Scutum-Crux spiral arm.Comment: 18 pages, LaTeX (aastex), incl. 8 PostScript (eps) figures and 1 table. Accepted by ApJ (Part 1

The Subaru-XMM-Newton Deep Survey (SXDS) VIII.: Multi-wavelength Identification, Optical/NIR Spectroscopic Properties, and Photometric Redshifts of X-ray Sources

We report the multi-wavelength identification of the X-ray sources found in the Subaru-XMM-Newton Deep Survey (SXDS) using deep imaging data covering the wavelength range between the far-UV to the mid-IR. We select a primary counterpart of each X-ray source by applying the likelihood ratio method to R-band, 3.6micron, near-UV, and 24micron source catalogs as well as matching catalogs of AGN candidates selected in 1.4GHz radio and i'-band variability surveys. Once candidates of Galactic stars, ultra-luminous X-ray sources in a nearby galaxy, and clusters of galaxies are removed there are 896 AGN candidates in the sample. We conduct spectroscopic observations of the primary counterparts with multi-object spectrographs in the optical and NIR; 65\% of the X-ray AGN candidates are spectroscopically-identified. For the remaining X-ray AGN candidates, we evaluate their photometric redshift with photometric data in 15 bands. Utilising the multi-wavelength photometric data of the large sample of X-ray selected AGNs, we evaluate the stellar masses, M*, of the host galaxies of the narrow-line AGNs. The distribution of the stellar mass is remarkably constant from z=0.1 to 4.0. The relation between M* and 2--10 keV luminosity can be explained with strong cosmological evolution of the relationship between the black hole mass and M*. We also evaluate the scatter of the UV-MIR spectral energy distribution (SED) of the X-ray AGNs as a function of X-ray luminosity and absorption to the nucleus. The scatter is compared with galaxies which have redshift and stellar mass distribution matched with the X-ray AGN. The UV-NIR SEDs of obscured X-ray AGNs are similar to those of the galaxies in the matched sample. In the NIR-MIR range, the median SEDs of X-ray AGNs are redder, but the scatter of the SEDs of the X-ray AGN broadly overlaps that of the galaxies in the matched sample.Comment: Accepted for publication in PASJ Subaru special issue. 42 pages, 22 figures. Entire contents of Tables 3, 8, 9, 10, and 11, and ASCII format tables are available from http://www.astr.tohoku.ac.jp/~akiyama/SXDS/index.htm

The XMM-Newton wide angle survey (XWAS): the X-ray spectrum of type-1 AGN

Aims. We discuss the broad band X-ray properties of one of the largest samples of X-ray selected type-1 AGN to date (487 objects in total), drawn from the XMM-Newton Wide Angle Survey (XWAS). The objects presented in this work cover 2−10 keV (rest-frame) luminosities from ∼1042−1045 erg s−1 and are detected up to redshift ∼4. We constrain the overall properties of the broad band continuum, soft excess and X-ray absorption, along with their dependence on the X-ray luminosity and redshift.We discuss the implications for models of AGN emission. Methods. We fitted the observed 0.2−12 keV broad band spectra with various models to search for X-ray absorption and soft excess. The F-test was used with a significance threshold of 99% to statistically accept the detection of additional spectral components. Results. We constrained the mean spectral index of the broad band X-ray continuum to (Γ) = 1.96 ± 0.02 with intrinsic dispersion σ(Γ) = 0.27+0.01 −0.02. The continuum becomes harder at faint fluxes and at higher redshifts and hard (2−10 keV) luminosities. The dependence of Γ with flux is likely due to undetected absorption rather than to spectral variation. We found a strong dependence of the detection efficiency of objects on the spectral shape. We expect this effect to have an impact on the measured mean continuum shapes of sources at different redshifts and luminosities. We detected excess absorption in >∼3% of our objects, with rest-frame column densities ∼a few ×1022 cm−2. The apparent mismatch between the optical classification and X-ray properties of these objects is a challenge for the standard orientation-based AGN unification model. We found that the fraction of objects with detected soft excess is ∼36%. Using a thermal model, we constrained the soft excess mean rest-frame temperature and intrinsic dispersion to kT ∼ 100 eV and σkT ∼ 34 eV. The origin of the soft excess as thermal emission from the accretion disk or Compton scattered disk emission is ruled out on the basis of the temperatures detected and the lack of correlation of the soft excess temperature with the hard X-ray luminosity over more than 2 orders of magnitude in luminosity. Furthermore, the high luminosities of the soft excess rule out an origin in the host galaxy.We acknowledge Chris Done, Bozena Czerny, Gordon Stewart, Pilar Esquej and Ken Pounds for useful comments. We acknowledge the anonymous referee for a careful reading of the manuscript and for comments that improved the paper. S.M., M.W. and J.A.T. acknowledge support from the UK STFC research council. F.J.C. acknowledges financial support for this work from the Spanish Ministerio de Educación y Ciencia under project ESP2006-13608-C02-01. A.C. acknowledges financial support from the Spanish Ministerio de Educación y Ciencia fellowship and also from the MIUR and The Italian Space Agency (ASI) grants PRIN-MUR 2006-02-5203 and No. I/088/06/0. M.K. acknowledges support from the NASA grant NNX08AX50G and NNX07AG02G

Hybrid managers, career narratives and identity work: a contextual analysis of UK healthcare organizations

While hybrid managers are increasingly important in contemporary organizations (especially in the public sector), we know little about why or how they become hybrid managers, or how this is shaped by the interplay of professional experience and organizational circumstances. In pursuit of a more variegated, contextualised and dynamic understanding of hybrid management, this paper focuses on how individuals transition into managerial hybrids, emphasizing the dynamic and emergent nature of hybrid management identity. Studying managers in English healthcare, we employ the concept of identity work as expressed through career narratives to examine the influence of career trajectories and organizational experiences on emerging hybrid manager identity. The study identifies three broad managerial career narratives – aspirational, ambivalent and agnostic – and relates them to experiences of doctor and nurse hybrid managers in three healthcare settings. An interpretive analysis of these narratives reveals a more variegated, situated and dynamic interpretation of hybrid managerial identities than previously considered and underscores the importance of personal and organizational experiences in shaping emergent hybrid professional/managerial identity

Platelet actin nodules are podosome-like structures dependent on Wiskott-Aldrich syndrome protein and ARP2/3 complex

The actin nodule is a novel F-actin structure present in platelets during early spreading. However, only limited detail is known regarding nodule organization and function. Here we use electron microscopy, SIM and dSTORM super-resolution, and live-cell TIRF microscopy to characterize the structural organization and signalling pathways associated with nodule formation. Nodules are composed of up to four actin-rich structures linked together by actin bundles. They are enriched in the adhesion-related proteins talin and vinculin, have a central core of tyrosine phosphorylated proteins and are depleted of integrins at the plasma membrane. Nodule formation is dependent on Wiskott-Aldrich syndrome protein (WASp) and the ARP2/3 complex. WASp(-/-) mouse blood displays impaired platelet aggregate formation at arteriolar shear rates. We propose actin nodules are platelet podosome-related structures required for platelet-platelet interaction and their absence contributes to the bleeding diathesis of Wiskott-Aldrich syndrome

The X-ray source content of the XMM-Newton Galactic plane survey

We report the results of an optical campaign carried out by the XMM-Newton Survey Science Centre with the specific goal of identifying the brightest X-ray sources in the XMM-Newton Galactic plane survey. In addition to photometric and spectroscopic observations obtained at the ESO-VLT and ESO-3.6 m, we used cross-correlations with the 2XMMi, USNO-B1.0, MASS, and GLIMPSE catalogues to advance the identification process. Active coronae account for 16 of the 30 positively or tentatively identified X-ray sources and exhibit the softest X-ray spectra. Many of the identified hard X-ray sources are associated with massive stars, possible members of binary systems and emitting at intermediate X-ray luminosities of 1032−34 erg s−1. Among these are (i) a very absorbed, likely hyper-luminous star with X-ray/optical spectra and luminosities comparable to those of η Carina; (ii) a new X-rayselected WN8 Wolf-Rayet star in which most of the X-ray emission probably arises from wind collision in a binary; (iii) a new Be/X-ray star belonging to the growing class of γ-Cas analogues; and (iv) a possible supergiant X-ray binary of the kind discovered recently by INTEGRAL. One of the sources, XGPS-25, has a counterpart of moderate optical luminosity that exhibits HeII λ4686 and Bowen CIII-NIII emission lines, suggesting that this may be a quiescent or X-ray shielded low mass X-ray binary, although its X-ray properties might also be consistent with a rare kind of cataclysmic variable (CV). We also report the discovery of three new CVs, one of which is a likely magnetic system displaying strong X-ray variability. The soft (0.4–2.0 keV) band log N(>S )−log S curve is completely dominated by active stars in the flux range of 1 × 10−13 to 1 × 10−14 erg cm−2 s−1. Several active coronae are also detected above 2 keV suggesting that the population of RS CVn binaries contributes significantly to the hard X-ray source population. In total, we are able to identify a large fraction of the hard (2–10 keV) X-ray sources in the flux range of 1 × 10−12 to 1 × 10−13 erg cm−2 s−1 with Galactic objects at a rate consistent with what is expected for the Galactic contribution alone.We thank an anonymous referee for useful comments which helped to improve the quality of this paper. We are grateful to O. Herent for carrying out some of the observations presented in this work. This work has been supported in part by the DLR (Deutsches Zentrum für Luftund Raumfahrt) under grants 50 OX 0201 and 50 OX 0801. I.N. is supported by the Spanish Ministerio de Ciencia e Innovación under grants AYA2008-06166-C03-03 and CSD2006-70. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. The DENIS project has been partly funded by the SCIENCE and the HCM plans of the European Commission under grants CT920791 and CT940627. It is supported by INSU, MEN and CNRS in France, by the State of Baden-Württemberg in Germany, by DGICYT in Spain, by CNR in Italy, by FFwFBWF in Austria, by FAPESP in Brazil, by OTKA grants F-4239 and F-013990 in Hungary, and by the ESO C&EE grant A-04-046. Jean Claude Renault from IAP was the Project manager. Observations were carried out thanks to the contribution of numerous students and young scientists from all involved institutes, under the supervision of P. Fouqué, survey astronomer resident in Chile. The WHT is operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. The observation presented here was taken as part of the ING service programme (proposal SW2005A06). This research has made use of Aladin, of the VizieR catalogue access tool and of Simbad at CDS, Strasbourg, France