320 research outputs found
Scrutinising evidence for the triggering of Active Galactic Nuclei in the outskirts of massive galaxy clusters at z≈1
No full textEnvironmental effects are believed to play an important yet poorly understood role in triggering accretion events onto the supermassive black holes (SMBHs) of galaxies (Active Galactic Nuclei; AGN). Massive clusters, which represent the densest structures in the Universe, provide an excellent laboratory to isolate environmental effects and study their impact on black hole growth. In this work, we critically review observational evidence for the preferential activation of SMBHs in the outskirts of galaxy clusters. We develop a semi-empirical model under the assumption that the incidence of AGN in galaxies is independent of environment. We demonstrate that the model is broadly consistent with recent observations on the AGN halo occupation at z=0.2, although it may overpredict satellite AGN in massive halos at that low redshift. We then use this model to interpret the projected radial distribution of X-ray sources around high redshift (z≈1) massive (>5×1014M⊙) clusters, which show excess counts outside their virial radius. Such an excess naturally arises in our model as a result of sample variance. Up to 20% of the simulated projected radial distributions show excess counts similar to the observations, which are however, because of background/foreground AGN and hence, not physically associated with the cluster. Our analysis emphasises the importance of projection effects and shows that current observations of z≈1 clusters remain inconclusive on the activation of SMBHs during infall
The Human Resources Strategic Management
No full textThe most of the specialists value the role of the strategies and the tactics in modern societies development, including in the economic field, especially in increasing the companies effectiveness, but also for mezo, macro and worldwide economic levels. As response to some strong requirements, the strategies are used not only in economic field, but also in other ones: political, military, social, educational etc. In Romania, for each field of activity and each organization is necessary to ground, to elaborate, to adopt and to operate realistic scientific strategies; to accelerate this action in human resources field, the most important organizational resources, perhaps this is the most necessary issue. This article targets the following: I. to provide a short description of the strategic management and the strategy’s concepts; II. to emphasize/to highlight the foreign and Romanian specialists points of view out of strategic human resources management; III.to present author`s own considerations about strategic human resources management.human resources; strategic management; strategy; human resources management.
Stellar population properties for 2 million galaxies from SDSS DR14 and DEEP2 DR4 from full spectral fitting
No full textThe elusive hot phase of the CGM and its interplay with the AGN feedback (review with an X-ray eROSITA focus)
No full textThe elusive hot phase of the CGM and its interplay with the AGN feedback (review with an X-ray eROSITA focus
Observation des oscillations baryoniques primordiales des galaxies à raie d’émission à décalage vers le rouge modéré : la structure aux grandes échelles dans l’univers.
No full textJ'ai démontrer la faisabilité de la sélection de la cible pour les galaxies en ligne des émissions lumineuses. Je comprends maintenant les principaux mécanismes physiques de conduite de l'efficacité d'une sélection, en particulier le rapport à la photométrie de parent. Une question reste perplexe, je ne pouvais pas encore estimer quantitativement l'impact de la poussière sur l'efficacité de la sélection. J'espère que d'aborder cette question avec l'ensemble des données décrites dans le chapitre 4.En dehors de la ligne de sélection de la cible de la galaxie d'émission, j'ai étudié, au premier ordre, les deux principales erreurs systématiques sur la détermination de l'échelle BAO nous attendent en raison de l'utilisation galaxies en ligne des émissions comme traceurs de la question. J'ai d'abord montré le caractère incomplet de la distribution redshift, en raison de la mesure du décalage spectral avec [Oii], est lié à la résolution instrumentale. Je trouve qu'il ya deux régimes intéressants. Pour une observation des plus brillants [OII] émetteurs, une résolution modérée est suffisante, alors que pour une enquête plus faible, la plus haute de la résolution le meilleur. Deuxièmement, j'ai estimé le biais de la galaxie linéaire des sélections discuté avant et je trouve qu'ils sont très biaisés. D'une part, ce sont d'excellentes nouvelles pour les observateurs, comme le temps nécessaire pour observer à un signal donné au bruit dans le spectre de puissance diminue avec le carré de la partialité. D'autre part, elle constitue un nouveau défi pour les algorithmes de reconstruction et la fabrication de catalogues simulacres.In this PhD, I demonstrate the feasibility of the target selection for bright emission line galaxies. Also I now understand the main physical mechanisms driving the efficiency of a selection, in particular the relation to the parent photometry. A puzzling issue remains, I could not yet estimate quantitatively the impact of the dust on the selection efficiency. I hope to address this question with the data set described in chapter 4.Apart from the emission line galaxy target selection, I investigated, at first order, the two main systematic errors on the determination of the BAO scale we expect due to using emission line galaxies as tracers of the matter. First I showed the incompleteness in the redshift distribution, due to the measurement of the redshift with [Oii], is related to the instrumental resolution. I find there are two interesting regimes. For an observation of the brightest [Oii]emitters, a moderate resolution is sufficient, whereas for a fainter survey, the highest the resolution the best. Secondly, I estimated the linear galaxy bias of the selections discussed before and I find they are highly biased. On one hand, this is great news for the observers, as the time required to observed at a given signal to noise in the power spectrum decreases with the square of the bias. On the other hand, it constitutes a new challenge for reconstruction algorithms and the making of mock catalogs. The work in progress described in the last chapter shows I am starting to try and handle these questions in a robust manner
Probing AGN inner structure with X-ray obscured type 1 AGN
No full textUsing the X-ray-selected active galactic nuclei (AGN) from the XMM-XXL
north survey and the Sloan Digital Sky Survey-Baryon Oscillation
Spectroscopic Survey spectroscopic follow-up of them, we compare the
properties of X-ray unobscured and obscured broad-line AGN (BLAGN1 and
BLAGN2; N-H below and above 10(21.5) cm(-2)), including their X-ray
luminosity L-X, black hole mass, Eddington ratio lambda(Edd), optical
continuum, and line features. We find that BLAGN2 have systematically
larger broad line widths and hence apparently higher (lower) M-BH
(lambda(Edd)) than BLAGN1. We also find that the X-ray obscuration in
BLAGN tends to coincide with optical dust extinction, which is optically
thinner than that in narrow-line AGN (NLAGN) and likely partial covering
to the broad-line region. All the results can be explained in the
framework of a multicomponent, clumpy torus model by interpreting BLAGN2
as an intermediate type between BLAGN1 and NLAGN in terms of an
intermediate inclination angle
The SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Final emission line galaxy target selection
No full textRaichoor, Anand et al.-- Full list of authors: Raichoor, A.; Comparat, J.; Delubac, T.; Kneib, J. -P.; Yèche, Ch; Dawson, K. S.; Percival, W. J.; Dey, A.; Lang, D.; Schlegel, D. J.; Gorgoni, C.; Bautista, J.; Brownstein, J. R.; Mariappan, V.; Seo, H. -J.; Tinker, J. L.; Ross, A. J.; Wang, Y.; Zhao, G. -B.; Moustakas, J.; Palanque-Delabrouille, N.; Jullo, E.; Newmann, J. A.; Prada, F.; Zhu, G. B.We describe the algorithm used to select the emission line galaxy (ELG) sample at z ~ 0.85 for the extended Baryon Oscillation Spectroscopic Survey of the Sloan Digital Sky Survey IV, using photometric data from the DECam Legacy Survey. Our selection is based on a selection box in the g - r versus r - z colour-colour space and a cut on the g-band magnitude, to favour galaxies in the desired redshift range with strong [O II] emission. It provides a target density of 200 deg on the North Galactic Cap and of 240 deg on the South Galactic Cap (SGC), where we use a larger selection box because of deeper imaging. We demonstrate that this selection passes the extended Baryon Oscillation Spectroscopic Survey requirements in terms of homogeneity. About 50 000 ELGs have been observed since the observations have started in 2016, September. These roughly match the expected redshift distribution, though the measured efficiency is slightly lower than expected. The efficiency can be increased by enlarging the redshift range and with incoming pipeline improvement. The cosmological forecast based on these first data predict σ/D = 0.023, in agreement with previous forecasts. Lastly, we present the stellar population properties of the ELG SGC sample. Once observations are completed, this sample will be suited to provide a cosmological analysis at z ~ 0.85, and will pave the way for the next decade of massive spectroscopic cosmological surveys, which heavily rely on ELGs. The target catalogue over the SGC will be released along with DR14. © 2017 The AuthorsAuthor contributions: AR, TD and JPK acknowledge support from
the ERC advanced grant LIDA.WJP acknowledges support from the
European Research Council through the Darksurvey grant 614030,
and from the UK Science and Technology Facilities Council grant
ST/N000668/1 and UK Space Agency grant ST/N00180X/1. EJ
acknowledges support from the OCEVU Labex (ANR-11-LABX0060).
This paper represents an effort by both the SDSS-IV collaborations. Funding for SDSS-III was provided by the Alfred P.
Sloan Foundation, the Participating Institutions, the National Science Foundation and the U.S. Department of Energy Office of
Science. Funding for the Sloan Digital Sky Survey IV has been
provided by the Alfred P. Sloan Foundation, the U.S. Department
of Energy Office of Science and the Participating Institutions.
SDSS-IV acknowledges support and resources from the Center
for High-Performance Computing at the University of Utah. The
SDSS web site is www.sdss.org. SDSS-IV is managed by the Astrophysical Research Consortium for the Participating Institutions
of the SDSS Collaboration including the Brazilian Participation
Group, the Carnegie Institution for Science, Carnegie Mellon University, the Chilean Participation Group, the French Participation
Group, Harvard-Smithsonian Center for Astrophysics, Instituto de
Astrof´ısica de Canarias, the Johns Hopkins University, Kavli
Institute for the Physics and Mathematics of the Universe
(IPMU)/University of Tokyo, Lawrence Berkeley National Laboratory, Leibniz Institut fur Astrophysik Potsdam (AIP), Max- ¨
Planck-Institut fur Astronomie (MPIA Heidelberg), Max-Planck- ¨
Institut fur Astrophysik (MPA Garching), Max-Planck-Institut ¨
fur Extraterrestrische Physik (MPE), National Astronomical ¨
Observatory of China, New Mexico State University, New
York University, University of Notre Dame, Observatario Na- ´
cional/MCTI, The Ohio State University, Pennsylvania State
University, Shanghai Astronomical Observatory, United Kingdom Participation Group, Universidad Nacional Autonoma de ´
Mexico, University of Arizona, University of Colorado Boul- ´
der, University of Portsmouth, University of Utah, University of
Virginia, University of Washington, University of Wisconsin, Vanderbilt University and Yale University.
This paper presents observations obtained at Cerro Tololo InterAmerican Observatory, National Optical Astronomy Observatory
(NOAO Prop. ID: 2014B-0404; co-PIs: D. J. Schlegel and A. Dey),
which is operated by the Association of Universities for Research
in Astronomy (AURA) under a cooperative agreement with the
National Science Foundation. This paper also includes DECam
observations obtained as part of other projects, namely the Dark
Energy Survey (DES, NOAO Prop. ID: 2012B-0001).
DECaLS used data obtained with the Dark Energy Camera
(DECam), which was constructed by the Dark Energy Survey
(DES) collaboration. Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science
Foundation, the Ministry of Science and Education of Spain, the
Science and Technology Facilities Council of the United Kingdom,
the Higher Education Funding Council for England, the National
Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological
Physics at the University of Chicago, Center for Cosmology and
Astro-Particle Physics at the Ohio State University, the Mitchell
Institute for Fundamental Physics and Astronomy at Texas A&M
University, Financiadora de Estudos e Projetos, Fundac¸ao Carlos ˜
Chagas Filho de Amparo, Financiadora de Estudos e Projetos,
Fundac¸ao Carlos Chagas Filho de Amparo ˜ a Pesquisa do Estado do `
Rio de Janeiro, Conselho Nacional de Desenvolvimento Cient´ıfico
e Tecnologico and the Minist ´ erio da Ci ´ encia, Tecnologia e Ino- ˆ
vacao, the Deutsche Forschungsgemeinschaft and the Collaborating ˜
Institutions in the Dark Energy Survey. The Collaborating Institutions are Argonne National Laboratory, the University of California
at Santa Cruz, the University of Cambridge, Centro de Investigaciones Energeticas, Medioambientales y Tecnol ´ ogicas-Madrid, the ´
University of Chicago, University College London, the DES-Brazil
Consortium, the University of Edinburgh, the Eidgenossische Tech- ¨
nische Hochschule (ETH) Zurich, Fermi National Accelerator Lab- ¨
oratory, the University of Illinois at Urbana-Champaign, the Institut
de Ciencies de l’Espai (IEEC/CSIC), the Institut de F ` ´ısica d’Altes
Energies, Lawrence Berkeley National Laboratory, the LudwigMaximilians Universitat M ¨ unchen and the associated Excellence ¨
Cluster Universe, the University of Michigan, the National Optical
Astronomy Observatory, the University of Nottingham, the Ohio
State University, the University of Pennsylvania, the University of
Portsmouth, SLAC National Accelerator Laboratory, Stanford University, the University of Sussex and Texas A&M University.
This publication uses data products from the Wide-field Infrared
Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California
Institute of Technology, and NEOWISE, which is a project of the
Jet Propulsion Laboratory/California Institute of Technology. WISE
and NEOWISE are funded by the National Aeronautics and Space
Administration.
Author contributions AR led this paper, designed the target selection, analysed the ELG plates and estimated the structural properties
and stellar masses. JC led the zspec measurement, developed the zspec
confidence flag, the spectra stacking procedure, and installed and
ran the DECaLS pipeline on the Utah machines (with JRB). TD led
the systematics analysis. JPK, ChY, KSD and WJP supervised the
ELG programme. JC, TD, KSD and CG did the visual inspection.
AJR, YW and GBZ did the cosmological forecast. HJS and JLT
led the tiling, VM led the spectroscopic observations, JB and JRB
led the spectroscopic pipeline reduction. AD, DL and DJS led the
DECaLS imaging observation and pipeline development. JM and
NPD reviewed the ELG programme and participated in the ELG
programme development. EJ, JAN, FP and GBZ also participated
in the ELG programme development
Scrutinizing evidence for the triggering of active galactic nuclei in the outskirts of massive galaxy clusters at <i>z</i> ≈ 1
No full textEnvironmental effects are believed to play an important yet poorly understood role in triggering accretion events onto the supermassive black holes (SMBHs) of galaxies (active galactic nuclei; AGNs). Massive clusters, which represent the densest structures in the Universe, provide an excellent laboratory to isolate environmental effects and study their impact on black hole growth. In this work, we critically review observational evidence for the preferential activation of SMBHs in the outskirts of galaxy clusters. We develop a semi-empirical model under the assumption that the incidence of AGN in galaxies is independent of environment. We demonstrate that the model is broadly consistent with recent observations on the AGN halo occupation at z = 0.2, although it may overpredict satellite AGN in massive haloes at that low redshift. We then use this model to interpret the projected radial distribution of X-ray sources around high redshift (z approximate to 1) massive (>5 x 10(14) M-circle dot) clusters, which show excess counts outside their virial radius. Such an excess naturally arises in our model as a result of sample variance. Up to 20 per cent of the simulated projected radial distributions show excess counts similar to the observations, which are however, because of background/foreground AGN and hence, not physically associated with the cluster. Our analysis emphasizes the importance of projection effects and shows that current observations of z approximate to 1 clusters remain inconclusive on the activation of SMBHs during infall
Cosmological implications of baryon acoustic oscillation measurements
No full textAubourg, Éric et al--Full list of authors: Aubourg, Éric; Bailey, Stephen; Bautista, Julian E.; Beutler, Florian; Bhardwaj, Vaishali; Bizyaev, Dmitry; Blanton, Michael; Blomqvist, Michael; Bolton, Adam S.; Bovy, Jo; Brewington, Howard; Brinkmann, J.; Brownstein, Joel R.; Burden, Angela; Busca, Nicolás G.; Carithers, William; Chuang, Chia-Hsun; Comparat, Johan; Croft, Rupert A. C.; Cuesta, Antonio J.; Dawson, Kyle S.; Delubac, Timothée; Eisenstein, Daniel J.; Font-Ribera, Andreu; Ge, Jian; Le Goff, J. -M.; Gontcho, Satya Gontcho A.; Gott, J. Richard; Gunn, James E.; Guo, Hong; Guy, Julien; Hamilton, Jean-Christophe; Ho, Shirley; Honscheid, Klaus; Howlett, Cullan; Kirkby, David; Kitaura, Francisco S.; Kneib, Jean-Paul; Lee, Khee-Gan; Long, Dan; Lupton, Robert H.; Magaña, Mariana Vargas; Malanushenko, Viktor; Malanushenko, Elena; Manera, Marc; Maraston, Claudia; Margala, Daniel; McBride, Cameron K.; Miralda-Escudé, Jordi; Myers, Adam D.; Nichol, Robert C.; Noterdaeme, Pasquier; Nuza, Sebastián E.; Olmstead, Matthew D.; Oravetz, Daniel; Pâris, Isabelle; Padmanabhan, Nikhil; Palanque-Delabrouille, Nathalie; Pan, Kaike; Pellejero-Ibanez, Marcos; Percival, Will J.; Petitjean, Patrick; Pieri, Matthew M.; Prada, Francisco; Reid, Beth; Rich, James; Roe, Natalie A.; Ross, Ashley J.; Ross, Nicholas P.; Rossi, Graziano; Rubiño-Martín, Jose Alberto; Sánchez, Ariel G.; Samushia, Lado; Génova-Santos, Ricardo Tanausú; Scóccola, Claudia G.; Schlegel, David J.; Schneider, Donald P.; Seo, Hee-Jong; Sheldon, Erin; Simmons, Audrey; Skibba, Ramin A.; Slosar, Anže; Strauss, Michael A.; Thomas, Daniel; Tinker, Jeremy L.; Tojeiro, Rita; Vazquez, Jose Alberto; Viel, Matteo; Wake, David A.; Weaver, Benjamin A.; Weinberg, David H.; Wood-Vasey, W. M.; Yèche, Christophe; Zehavi, Idit; Zhao, Gong-Bo; BOSS CollaborationWe derive constraints on cosmological parameters and tests of dark energy models from the combination of baryon acoustic oscillation (BAO) measurements with cosmic microwave background (CMB) data and a recent reanalysis of Type Ia supernova (SN) data. In particular, we take advantage of high-precision BAO measurements from galaxy clustering and the Lyman-α forest (LyaF) in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). Treating the BAO scale as an uncalibrated standard ruler, BAO data alone yield a high confidence detection of dark energy; in combination with the CMB angular acoustic scale they further imply a nearly flat universe. Adding the CMB-calibrated physical scale of the sound horizon, the combination of BAO and SN data into an "inverse distance ladder" yields a measurement of H0=67.3±1.1 km s-1 Mpc-1, with 1.7% precision. This measurement assumes standard prerecombination physics but is insensitive to assumptions about dark energy or space curvature, so agreement with CMB-based estimates that assume a flat ΛCDM cosmology is an important corroboration of this minimal cosmological model. For constant dark energy (Λ), our BAO+SN+CMB combination yields matter density Ωm=0.301±0.008 and curvature Ωk=-0.003±0.003. When we allow more general forms of evolving dark energy, the BAO+SN+CMB parameter constraints are always consistent with flat ΛCDM values at ≈1σ. While the overall χ2 of model fits is satisfactory, the LyaF BAO measurements are in moderate (2-2.5σ) tension with model predictions. Models with early dark energy that tracks the dominant energy component at high redshift remain consistent with our expansion history constraints, and they yield a higher H0 and lower matter clustering amplitude, improving agreement with some low redshift observations. Expansion history alone yields an upper limit on the summed mass of neutrino species, mν<0.56 eV (95% confidence), improving to mν<0.25 eV if we include the lensing signal in the Planck CMB power spectrum. In a flat ΛCDM model that allows extra relativistic species, our data combination yields Neff=3.43±0.26; while the LyaF BAO data prefer higher Neff when excluding galaxy BAO, the galaxy BAO alone favor Neff≈3. When structure growth is extrapolated forward from the CMB to low redshift, standard dark energy models constrained by our data predict a level of matter clustering that is high compared to most, but not all, observational estimates. © 2015 American Physical Society.We thank Eric Linder for useful discussions of early dark energy and structure growth. We also thank Savvas Koushiappas and Gordon Blackadder for alerting us to an error in the decaying dark matter section of the preprint version of this paper and answering our questions as we corrected it. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III web site is http://www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University.Peer reviewe
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