WorldWideScience

Sample records for agn reactor series

  1. Time Series Analysis of the UV Flickering in AGN

    Science.gov (United States)

    Robinson, Edward L.

    2003-01-01

    Goals of the Research: Many active galactic nuclei (AGN) exhibit large-amplitude luminosity fluctuations on short timescales. The fluctuations lead to a profound conclusion: The size of the emitting region is remarkably small. This observational fact is one of the pillars supporting the AGN paradigm: Prodigious amounts of gravitational potential energy are liberated in an accretion disk around a supermassive black hole. The goals of the research were to extract from the IUE Archive the very best observational characterizations of AGN flickering, and to use these to test and develop models for AGN variability.

  2. 76 FR 11291 - University of New Mexico AGN-201M Reactor Notice of Issuance of Renewed Facility Operating...

    Science.gov (United States)

    2011-03-01

    ... COMMISSION University of New Mexico AGN-201M Reactor Notice of Issuance of Renewed Facility Operating License... No. R-102, held by the University of New Mexico (the licensee), which authorizes continued operation of the University of New Mexico AGN-201M Reactor (UNMR), located in Albuquerque, Bernalillo...

  3. The First Reactor, Understanding the Atom Series.

    Science.gov (United States)

    Allardice, Corbin; And Others

    This booklet is one of the "Understanding the Atom" Series. Consisting of three sections, it is an account of the development of the first nuclear reactor by a team of scientists led by Enrico Farmi. The first section briefly reviews the early work on nuclear fission and neutron emission, the impact of Einstein's letter to President Roosevelt, the…

  4. Breeder Reactors, Understanding the Atom Series.

    Science.gov (United States)

    Mitchell, Walter, III; Turner, Stanley E.

    The theory of breeder reactors in relationship to a discussion of fission is presented. Different kinds of reactors are characterized by the cooling fluids used, such as liquid metal, gas, and molten salt. The historical development of breeder reactors over the past twenty-five years includes specific examples of reactors. The location and a brief…

  5. Nonlinear analysis and prediction of time series in multiphase reactors

    CERN Document Server

    Liu, Mingyan

    2014-01-01

    This book reports on important nonlinear aspects or deterministic chaos issues in the systems of multi-phase reactors. The reactors treated in the book include gas-liquid bubble columns, gas-liquid-solid fluidized beds and gas-liquid-solid magnetized fluidized beds. The authors take pressure fluctuations in the bubble columns  as time series for nonlinear analysis, modeling and forecasting. They present qualitative and quantitative non-linear analysis tools which include attractor phase plane plot, correlation dimension, Kolmogorov entropy and largest Lyapunov exponent calculations and local non-linear short-term prediction.

  6. Ongoing Development of a Series Bosch Reactor System

    Science.gov (United States)

    Abney, Morgan B; Mansell, J. Matthew; Stanley, Christine; Edmunson, Jennifer; DuMez, Samuel J.; Chen, Kevin

    2013-01-01

    Future manned missions to deep space or planetary surfaces will undoubtedly incorporate highly robust, efficient, and regenerable life support systems that require minimal consumables. To meet this requirement, NASA continues to explore a Bosch-based carbon dioxide reduction system to recover oxygen from CO2. In order to improve the equivalent system mass of Bosch systems, we seek to design and test a "Series Bosch" system in which two reactors in series are optimized for the two steps of the reaction, as well as to explore the use of in situ materials as carbon deposition catalysts. Here we report recent developments in this effort including assembly and initial testing of a Reverse Water-Gas Shift reactor (RWGSr) and initial testing of two gas separation membranes. The RWGSr was sized to reduce CO2 produced by a crew of four to carbon monoxide as the first stage in a Series Bosch system. The gas separation membranes, necessary to recycle unreacted hydrogen and CO2, were similarly sized. Additionally, we report results of preliminary experiments designed to determine the catalytic properties of Martian regolith simulant for the carbon formation step.

  7. Reduction of Microbial Population in Cheese Whey by UV in a Single and Series Conventional Reactors

    Directory of Open Access Journals (Sweden)

    Abdel E. Ghaly

    2006-01-01

    Full Text Available In this study, the effectiveness of two conventional UV reactors in series for the online sterilization of cheese whey was compared to that of a single conventional reactor. The single reactor and the two reactor series were tested at eleven flow rates (5, 10, 15, 20, 25, 30, 35, 40, 50, 60 and 70 mL min-1 and five flow rates, (35, 40, 50, 60, 70 mL min-1, respectively. 100% destruction efficiency could not be achieved in the single reactor. When two reactors were connected in series, the destruction efficiency reached 100% at the flow rate of 35 mL min-1 and lasted for 25 min. The temperature of the effluent decreased with the increase in flow rate in both systems. The rate of microbial destruction in the single reactor and the two reactor series was described by an exponential equation. The maximum effluent temperatures in the single reactor and the two reactor series were 45.8 and 36.0°C, respectively. The flow in both reactors was laminar (Re=1.39 at 5mL min-1 and Re= 20.10 at 70 mL min-1. Visual observation revealed less fouling on the UV lamps of two reactor series than the single reactor. A different design in which there is no contact between the liquid and the UV lamp should be investigated. The quartz sleeve could also be replaced with fluropolymer coiled tube around the UV lamp. The smooth surface of the fluropolymer would reduce scaling and extend the effective operating time.

  8. Obscured AGN

    Science.gov (United States)

    Ptak, Andrew

    2011-01-01

    Many obscured AGN show evidence of significant starburst emission dominating below 2 keV. Therefore wide-field X-ray surveys sensitive enough to luminosities below approximately 10^42 ergs per second will result in detections of galaxies with contributions of both obscured AGN and starburst emission. We will discuss Bayesian approaches to assessing the relative contribution of each component, minimizing survey biases and using the resultant posterior probabilities for the AGN and starburst components to determine their evolution.

  9. Possible pressurized thermal shock events during large primary to secondary leakage. The Hungarian AGNES project and PRISE accident scenarios in VVER-440/V213 type reactor

    Energy Technology Data Exchange (ETDEWEB)

    Perneczky, L. [KFKI Atomic Energy Research Inst., Budabest (Hungary)

    1997-12-31

    Nuclear power plants of WWER-440/213-type have several special features. Consequently, the transient behaviour of such a reactor system should be different from the behaviour of the PWRs of western design. The opening of the steam generator (SG) collector cover, as a specific primary to secondary circuit leakage (PRISE) occurring in WWER-type reactors happened first time in Rovno NPP Unit I on January 22, 1982. Similar accident was studied in the framework of IAEA project RER/9/004 in 1987-88 using the RELAP4/mod6 code. The Hungarian AGNES (Advanced General and New Evaluation of Safety) project was performed in the period 1991-94 with the aim to reassess the safety of the Paks NPP using state-of-the-art techniques. The project comprised three type of analyses for the primary to secondary circuit leakages: Design Basis Accident (DBA) analyses, Pressurized Thermal Shock (PTS) study and deterministic analyses for Probabilistic Safety Analysis (PSA). Major part of the thermohydraulic analyses has been performed by the RELAP5/mod2.5/V251 code version with two input models. 32 refs.

  10. 75 FR 27372 - University of New Mexico; University of New Mexico AGN-201M Reactor; Environmental Assessment and...

    Science.gov (United States)

    2010-05-14

    ... of New Mexico Radiation Safety. Finally, there is a 60 cm concrete block shield on the front of the reactor tank and 40 cm concrete block shields on the sides and back. There is no shielding on the top of... one-story concrete structure with six feet of earth between one foot thick concrete walls on the...

  11. Reactors

    CERN Document Server

    International Electrotechnical Commission. Geneva

    1988-01-01

    This standard applies to the following types of reactors: shunt reactors, current-limiting reactors including neutral-earthing reactors, damping reactors, tuning (filter) reactors, earthing transformers (neutral couplers), arc-suppression reactors, smoothing reactors, with the exception of the following reactors: small reactors with a rating generally less than 2 kvar single-phase and 10 kvar three-phase, reactors for special purposes such as high-frequency line traps or reactors mounted on rolling stock.

  12. EXPERIMENTAL STUDY OF THYRISTOR CONTROLLED REACTOR (TCR AND GTO CONTROLLED SERIES CAPACITOR (GCSC

    Directory of Open Access Journals (Sweden)

    JYOTI AGRAWAL,

    2011-06-01

    Full Text Available This paper deals with the simulation of Thyristor controlled reactor (TCR and GTO Controlled Series Capacitor (GCSC, equipment for controlled series compensation of transmission systems. The paper alsopresents experimental results of a TCR and GCSC connected to a single-phase system. The experiments are carried out in the FACTS lab of electrical engineering department. The TCR system is simulated using MATLAB and the simulation results are presented. The power and control circuits are simulated. The current drawn by the TCR varies with the variation in the firing angle. Stepped variation of current can be obtained using thyristor switched reactor. The simulation results are compared with the theoretical and practical results.Harmonics and its impact on the system are presented. This paper also presents the GCSC, its main components, principal of operation, typical waveforms and main applications. Duality of the GCSC with the well known thyristor controlled reactor is also discussed in this paper.

  13. State Observer Design for Monitoring the Degree of Polymerization in a Series of Melt Polycondensation Reactors

    Directory of Open Access Journals (Sweden)

    Chen Ling

    2016-01-01

    Full Text Available A nonlinear reduced-order state observer is applied to estimate the degree of polymerization in a series of polycondensation reactors. The finishing stage of polyethylene terephthalate synthesis is considered in this work. This process has a special structure of lower block triangular form, which is properly utilized to facilitate the calculation of the state-dependent gain in the observer design. There are two possible on-line measurements in each reactor. One is continuous, and the other is slow-sampled with dead time. For the slow-sampled titration measurement, inter-sample behavior is estimated from an inter-sample output predictor, which is essential in providing continuous corrections on the observer. Dead time compensation is carried out in the same spirit as the Smith predictor to reduce the effect of delay in the measurement outputs. By integrating the continuous-time reduced-order observer, the inter-sample predictor and the dead time compensator together, the degree of polymerization is accurately estimated in all reactors. The observer performance is demonstrated by numerical simulations. In addition, a pre-filtering technique is used in the presence of sensor noise.

  14. Multi-faceted AGN

    Science.gov (United States)

    Farrar, Glennys R.; Chen, Yanping; Dai, Yuxiao; Zaw, Ingyin

    2016-08-01

    An interesting question is how frequently an object is an AGN by multiple different criteria — e.g., is simultaneously a narrow-line optical AGN and an X-ray or radio AGN, possibly as a function of luminosities in the various wavebands and perhaps host galaxy type. Answering such questions quantitatively has been difficult up to now because of the lack of a complete, uniformly selected optical AGN catalog. Here we report first results of such an analysis, using the new, all-sky catalog of uniformly selected optical AGNs from Zaw, Chen and Farrar (2016), the Swift-BAT 70-month catalog of X-ray AGN (Baumgartner et al., 2013), and the van Velzen et al. (2012) catalog of radio AGN.

  15. Development of toroid-type HTS DC reactor series for HVDC system

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kwangmin, E-mail: kwangmin81@gmail.com [Changwon National University, 55306 Sarim-dong, Changwon 641-773 (Korea, Republic of); Go, Byeong-Soo; Park, Hea-chul; Kim, Sung-kyu; Kim, Seokho [Changwon National University, 55306 Sarim-dong, Changwon 641-773 (Korea, Republic of); Lee, Sangjin [Uiduk University, Gyeongju 780-713 (Korea, Republic of); Oh, Yunsang [Vector Fields Korea Inc., Pohang 790-834 (Korea, Republic of); Park, Minwon; Yu, In-Keun [Changwon National University, 55306 Sarim-dong, Changwon 641-773 (Korea, Republic of)

    2015-11-15

    Highlights: • The authors developed the 400 mH, 400 A class toroid-type HTS DC reactor system. • The target temperature, inductance and operating current are under 20 K at magnet, 400 mH and 400 A, respectively. All target performances of the HTS DC reactor were achieved. • The HTS DC reactor was conducted through the interconnection operation with a LCC type HVDC system. • Now, the authors are studying the 400 mH, 1500 A class toroid-type HTS DC reactor for the next phase HTS DC reactor. - Abstract: This paper describes design specifications and performance of a toroid-type high-temperature superconducting (HTS) DC reactor. The first phase operation targets of the HTS DC reactor were 400 mH and 400 A. The authors have developed a real HTS DC reactor system during the last three years. The HTS DC reactor was designed using 2G GdBCO HTS wires. The HTS coils of the toroid-type DC reactor magnet were made in the form of a D-shape. The electromagnetic performance of the toroid-type HTS DC reactor magnet was analyzed using the finite element method program. A conduction cooling method was adopted for reactor magnet cooling. The total system has been successfully developed and tested in connection with LCC type HVDC system. Now, the authors are studying a 400 mH, kA class toroid-type HTS DC reactor for the next phase research. The 1500 A class DC reactor system was designed using layered 13 mm GdBCO 2G HTS wire. The expected operating temperature is under 30 K. These fundamental data obtained through both works will usefully be applied to design a real toroid-type HTS DC reactor for grid application.

  16. Monitoring anaerobic sequential batch reactors via fractal analysis of pH time series.

    Science.gov (United States)

    Méndez-Acosta, H O; Hernandez-Martinez, E; Jáuregui-Jáuregui, J A; Alvarez-Ramirez, J; Puebla, H

    2013-08-01

    Efficient monitoring and control schemes are mandatory in the current operation of biological wastewater treatment plants because they must accomplish more demanding environmental policies. This fact is of particular interest in anaerobic digestion processes where the availability of accurate, inexpensive, and suitable sensors for the on-line monitoring of key process variables remains an open problem nowadays. In particular, this problem is more challenging when dealing with batch processes where the monitoring strategy has to be performed in finite time, which limits the application of current advanced monitoring schemes as those based in the proposal of nonlinear observers (i.e., software sensors). In this article, a fractal time series analysis of pH fluctuations in an anaerobic sequential batch reactor (AnSBR) used for the treatment of tequila vinasses is presented. Results indicated that conventional on-line pH measurements can be correlated with off-line determined key process variables, such as COD, VFA and biogas production via some fractality indexes.

  17. Reactor models for a series of continuous stirred tank reactors with a gas-liquid-solid leaching system: Part II. Gas-transfer control

    Science.gov (United States)

    Papangelakis, V. G.; Demopoulos, G. P.

    1992-12-01

    This article is the second in a three-article series devoted to the development of comprehensive three-phase steady-state reactor models. In this article in particular, model equations are developed for the case of a leaching reactor operating under pure gas-transfer control. That is, the transfer of a gaseous reactant at the g-1 interface is considered to be the controlling step of the process rather than the particle dissolution reaction itself. For the derivation of the appropriate model equations, the gas-transfer capacity of the reactor is coupled with the particle dissolution kinetics. Two model versions are developed. In model version 1, the dissolved gas is assumed to be distributed equally among all particles. On the basis of this assumption, a gastransfer control-shrinking core model (GTC-SCM) equation is formulated which, along with the segregated flow model, helps to calculate the conversion of the solid phase. The size distribution of the particles at the exit of the reactor is computed via a mass-particle size density (PSD) function derived with the use of the population balance model (PBM). In model version 2, the dissolved gas is assumed to be distributed among particles in proportion to their surface area. Using the PBM, equations are developed suitable for the calculation of the total specific surface area of the reacting solids and their conversion. Single as well as multiple parallel leaching reactions are considered in developing the two model versions.

  18. Development of toroid-type HTS DC reactor series for HVDC system

    Science.gov (United States)

    Kim, Kwangmin; Go, Byeong-Soo; Park, Hea-chul; Kim, Sung-kyu; Kim, Seokho; Lee, Sangjin; Oh, Yunsang; Park, Minwon; Yu, In-Keun

    2015-11-01

    This paper describes design specifications and performance of a toroid-type high-temperature superconducting (HTS) DC reactor. The first phase operation targets of the HTS DC reactor were 400 mH and 400 A. The authors have developed a real HTS DC reactor system during the last three years. The HTS DC reactor was designed using 2G GdBCO HTS wires. The HTS coils of the toroid-type DC reactor magnet were made in the form of a D-shape. The electromagnetic performance of the toroid-type HTS DC reactor magnet was analyzed using the finite element method program. A conduction cooling method was adopted for reactor magnet cooling. The total system has been successfully developed and tested in connection with LCC type HVDC system. Now, the authors are studying a 400 mH, kA class toroid-type HTS DC reactor for the next phase research. The 1500 A class DC reactor system was designed using layered 13 mm GdBCO 2G HTS wire. The expected operating temperature is under 30 K. These fundamental data obtained through both works will usefully be applied to design a real toroid-type HTS DC reactor for grid application.

  19. Reactor models for a series of continuous stirred tank reactors with a gas-liquid-solid leaching system: Part I. Surface reaction control

    Science.gov (United States)

    Papangelakis, V. G.; Demopoulos, G. P.

    1992-12-01

    In this three-part series of articles, comprehensive three-phase steady-state hydrometallurgical reactor models of the continuous stirred tank reactor (CSTR) type are developed and applied to a commercial (pressure oxidation) process. The key features of the developed models are the coupling of both mass and heat balance equations, the description of the nonisothermal performance (autothermal) of a multistage continuous reactor, and the treatment of multimineral feed materials. The model considers only the oxidation reactions, because they mainly affect the thermal balance of the reactor. The stoichiometries and intrinsic kinetics of the heterogeneous leaching reactions, which are established via independent experiments, are the foundation of the developed model. A three-phase (g-l-s) reaction process might be controlled by either surface reaction control, i.e., the rate(s) of the heterogeneous leaching reaction(s), or by gas transfer control, i.e., the rate of transfer of the gaseous reactant into the liquid phase. In the present article (Part I), the case of surface reaction control is treated. The article addresses, in particular, the following topics: (1) it outlines the basic mass and heat balance equations which describe the performance of a multistage leaching reactor; (2) it presents a continuous function to describe the particle size distribution of the feed; and (3) it develops, on the basis of probability theory, number- and mass-particle size density functions which give the size distribution of particle populations reacting according to the surface reaction control-shrinking core model.

  20. Signatures of AGN feedback

    Science.gov (United States)

    Wylezalek, Dominika; Zakamska, Nadia L.; MaNGA-GMOS Team

    2017-01-01

    Feedback from actively accreting SMBHs (Active Galactic Nuclei, AGN) is now widely considered to be the main driver in regulating the growth of massive galaxies. Observational proof for this scenario has, however, been hard to come by. Many attempts at finding a conclusive observational proof that AGN may be able to quench star formation and regulate the host galaxies' growth have shown that this problem is highly complex.I will present results from several projects that focus on understanding the power, reach and impact of feedback processes exerted by AGN. I will describe recent efforts in our group of relating feedback signatures to the specific star formation rate in their host galaxies, where our results are consistent with the AGN having a `negative' impact through feedback on the galaxies' star formation history (Wylezalek+2016a,b). Furthermore, I will show that powerful AGN-driven winds can be easily hidden and not be apparent in the integrated spectrum of the galaxy. This implies that large IFU surveys, such as the SDSS-IV MaNGA survey, might uncover many previously unknown AGN and outflows that are potentially very relevant for understanding the role of AGN in galaxy evolution (Wylezalek+2016c)!

  1. Neutrinos from AGN

    Science.gov (United States)

    Kazanas, Demosthenes; White, Nicholas E. (Technical Monitor)

    2000-01-01

    The great penetrating power of neutrinos makes them ideal probe of astrophysical sites and conditions inaccessible to other forms of radiation. These are the centers of stars (collapsing or not) and the centers of Active Galactic Nuclei (AGN). It has been suggested that AGN presented a very promising source of high energy neutrinos, possibly detectable by underwater neutrino detectors. This paper reviews the evolution of ideas concerning the emission of neutrinos from AGN in view of the more recent developments in gamma-ray astronomy and their implications for the neutrino emission from these class of objects.

  2. Reactor

    Science.gov (United States)

    Evans, Robert M.

    1976-10-05

    1. A neutronic reactor having a moderator, coolant tubes traversing the moderator from an inlet end to an outlet end, bodies of material fissionable by neutrons of thermal energy disposed within the coolant tubes, and means for circulating water through said coolant tubes characterized by the improved construction wherein the coolant tubes are constructed of aluminum having an outer diameter of 1.729 inches and a wall thickness of 0.059 inch, and the means for circulating a liquid coolant through the tubes includes a source of water at a pressure of approximately 350 pounds per square inch connected to the inlet end of the tubes, and said construction including a pressure reducing orifice disposed at the inlet ends of the tubes reducing the pressure of the water by approximately 150 pounds per square inch.

  3. Using Flow Electrodes in Multiple Reactors in Series for Continuous Energy Generation from Capacitive Mixing

    KAUST Repository

    Hatzell, Marta C.

    2014-12-09

    Efficient conversion of “mixing energy” to electricity through capacitive mixing (CapMix) has been limited by low energy recoveries, low power densities, and noncontinuous energy production resulting from intermittent charging and discharging cycles. We show here that a CapMix system based on a four-reactor process with flow electrodes can generate constant and continuous energy, providing a more flexible platform for harvesting mixing energy. The power densities were dependent on the flow-electrode carbon loading, with 5.8 ± 0.2 mW m–2 continuously produced in the charging reactor and 3.3 ± 0.4 mW m–2 produced in the discharging reactor (9.2 ± 0.6 mW m–2 for the whole system) when the flow-electrode carbon loading was 15%. Additionally, when the flow-electrode electrolyte ion concentration increased from 10 to 20 g L–1, the total power density of the whole system (charging and discharging) increased to 50.9 ± 2.5 mW m–2.

  4. Trigonometric Fourier-series solutions of the point reactor kinetics equations

    Energy Technology Data Exchange (ETDEWEB)

    Hamada, Yasser Mohamed, E-mail: yaser_abdelsatar@ci.suez.edu.eg

    2015-01-15

    Highlights: • A new method based on Fourier series expansion is introduced. • The method provides accurate approximations to the point kinetics equations. • Vandermonde matrix is used to determine the coefficients of the Fourier series. • A new formula is introduced to determine the inverse of the Vandermonde matrix. • The obtained results agree well with those obtained with other conventional codes. - Abstract: In this paper, a new method based on the Fourier series is introduced to obtain approximate solutions to the systems of the point kinetics equations. These systems are stiff involving equations with slowly and rapidly varying components. They are solved numerically using Fourier series expansion over a partition of the total time interval. Approximate solution requires determining the series coefficients over each time step in that partition. These coefficients are determined using the high order derivatives of the dependent variables at the beginning of the time step introducing a system of linear algebraic equations to be solved at each step. The obtained algebraic system is similar to the Vandermonde system. Evaluation of the inverse of the Vandermonde matrix is required to determine the coefficients of the Fourier series. Because the obtained Vandermonde matrix has a special structure, due to the properties of the sine and cosine functions, a new formula is introduced to determine its inverse using standard computations. The new method solves the general linear and non-linear kinetics problems with six groups of delayed neutrons. The validity of the algorithm is tested with five different types of reactivities including step reactivity insertion, ramp input, oscillatory reactivity changes, a reactivity as a function of the neutron density and finally temperature feedback reactivity. Comparisons are made with analytical and conventional numerical methods used to solve the point kinetics equations. The results confirm the theoretical analysis

  5. CERN Library | Agnes Chavez @ CERN | 3 May

    CERN Multimedia

    CERN Library

    2016-01-01

    Agnes Chavez is an artist and educator participating in a two-week research stay through the ATLAS Experiment at CERN.   Tuesday 3 May at 4 p.m. CERN Library (52 1-052) Artist/educator, Agnes Chavez will share video outcomes from Projecting Particles, an Art + Science + Education collaboration with ATLAS. The Sci-Art project combines the International Masterclass with Projection Art in a series of teen-led youth workshops and projection events. In this presentation Chavez will share her vision and describe the research and development behind the project, now in its third year.  For the Projecting pARTicles series of art installations she has formed an interdisciplinary team of programmers, artists, scientists and educators to investigate how we can create art and education interventions inspired by emerging particle physics theories. Chavez’s art experiments with data visualization, sound and projections to create participatory environments. She collaborates with programmers t...

  6. Unobscured Type 2 AGNs

    CERN Document Server

    Shi, Yong; Smith, Paul; Rigby, Jane; Hines, Dean; Donley, Jennifer; Schmidt, Gary; Diamond-Stanic, Aleksandar M; 10.1088/0004-637X/714/1/115

    2010-01-01

    Type 2 AGNs with intrinsically weak broad emission lines (BELs) would be exceptions to the unified model. After examining a number of proposed candidates critically, we find that the sample is contaminated significantly by objects with BELs of strengths indicating that they actually contain intermediate-type AGNs, plus a few Compton-thick sources as revealed by extremely low ratios of X-ray to nuclear IR luminosities. We develop quantitative metrics that show two (NGC 3147 and NGC 4594) of the remaining candidates to have BELs 2-3 orders of magnitude weaker than those of typical type-1 AGNs. Several more galaxies remain as candidates to have anomalously weak BELs, but this status cannot be confirmed with the existing information. Although the parent sample is poorly defined, the two confirmed objects are well under 1% of its total number of members, showing that the absence of a BEL is possible, but very uncommon in AGN. We evaluate these two objects in detail using multi-wavelength measurements. They have li...

  7. Circular polarisation in AGN

    NARCIS (Netherlands)

    Macquart, JP

    2002-01-01

    We discuss the constraints that recent observations place on circular polarisation in AGN. In many sources the circular polarisation is variable on short timescales, indicating that it originates in compact regions of the sources. The best prospects for gleaning further information about circular po

  8. SWIFT Observations AGN

    Science.gov (United States)

    Mushotzky, Richard

    2008-01-01

    I will present results from the x-ray and optical follow-up observations of the Swift Burst Alert Telescope (BAT) Active Galactic Nuclei (AGN) survey. I will discuss the nature of obscuration in these objects, the relationship to optical properties and the change of properties with luminosity and galaxy type.

  9. The evolution of obscured AGN

    Science.gov (United States)

    Brightman, Murray

    2012-09-01

    We present results on the evolution of Compton thick AGN with redshift, and the nature of this obscuration, important for understanding the accretion history of the universe and for AGN unification schemes. We use lessons learned from spectral complexity of local AGN (Brightman & Nandra 2012) and up to date spectral models of heavily absorbed AGN, which take into account Compton scattering, self consistent Fe Ka modeling and the geometry of the circumnuclear material (Brightman & Nandra 2011), to optimise our identification of Compton thick AGN and understanding of the obscuring material. Results from the Chandra Deep Field South are presented (Brightman & Ueda, 2012), which show an increasing fraction of CTAGN with redshift and that most heavily obscured AGN are geometrically deeply buried in material, as well as new results from and extension of this study to AEGIS-XD and Chandra-COSMOS survey, which aim to fully characterise the dependence of heavy AGN obscuration on redshift and luminosity.

  10. New models of radical polymerization with branching and scission predicting molecular weight distribution in tubular and series of continuous stirred tank reactors allowing for multiradicals and gelation

    NARCIS (Netherlands)

    Yaghini, N.; Iedema, P.D.

    2015-01-01

    Modeling of the mol. wt. distribution (MWD) of low-​d. Polyethylene (ldPE) has been carried out for a tubular reactor under realistic non-​isothermal conditions and for a series of CSTR's. The model allows for the existence of multiradicals and the occurrence of gelation. The deterministic model is

  11. How are AGN Found?

    CERN Document Server

    Mushotzky, R

    2004-01-01

    We discuss the very different methods in each wavelength band for selecting and finding Active Galactic Nuclei (AGN). We briefly review the history of the different techniques for finding AGN and compare and contrast the advantages and difficulties of selection in different wavelength bands. We stress the strong selection effects in each wavelength band and the difficulty of defining complete samples. Of all the techniques presently used, we conclude that selection in the hard X-ray band via imaging and spectroscopy is the most complete and allows the best estimate of the number and evolution of active galaxies. However, all of the techniques have difficulties at low luminosities where emission due to stellar processes can have similar sizes and luminosities.

  12. Absorbing Outflows in AGN

    Science.gov (United States)

    Mathur, Smita

    2002-01-01

    The goal of this program was a comprehensive multiwavelength study of absorption phenomena in active galactic nuclei (AGN). These include a variety of associated absorption systems: X-ray warm absorbers, X-ray cold absorbers. UV absorbers with high ionization lines, MgII absorbers, red quasars and BALQSOs. The aim is to determine the physical conditions in the absorbing outflows, study their inter-relations and their role in AGN. We designed several observing programs to achieve this goal: X-ray spectroscopy, UV spectroscopy, FLAY spectroscopy and X-ray imaging. We were very successful towards achieving the goal over the five year period as shown through following observing programs and papers. Copies of a few papers are attached with this report.

  13. Ionized Absorbers in AGN

    Science.gov (United States)

    Mathur, S.

    1999-01-01

    As a part of this program, we observed three AGN:PKS2251 + 113, PG0043 = 039 and PLH909. Two objects show signatures of absorbtion in their UV spectra. Based on our earlier modeling of X-ray warm absorbents, we expected to observe X-ray observation in these objects. The third, PLH909, is known to have soft excess in EINSTEIN data. Attachment: "Exploratory ASCA observation of broad absorption line quasi-stellar objects".

  14. A Method of Identifying AGNs Based on Emission-Line Excess and the Nature of Low-Luminosity AGNs in the Sloan Digital Sky Survey. II. The Nature of Low-Luminosity AGNs

    Science.gov (United States)

    Tanaka, Masayuki

    2012-04-01

    We have developed a new method of identifying active galactic nuclei (AGNs) and studied the nature of low-luminosity AGNs in the Sloan Digital Sky Survey. This is the latter part of a series of papers in which we consider correlations between the AGN activities and the host-galaxy properties. Based on a sample of AGNs identified by a new method developed in the former part (2012, PASJ, 64, 36), we found that AGNs typically show extinction of τV = 1.2, and exhibit a wide range of ionization levels. The finding of ionization levels motivated us to use [O II] + [O III] as an indicator of AGN power. We found that AGNs are preferentially located in massive, red, early-type galaxies. Taking into account a selection bias of the Oxygen-excess method, we showed that strong AGNs are located in active star-forming galaxies, and that rapidly growing super-massive black holes are located in rapidly growing galaxies, which clearly shows the coevolution of super-massive black holes and their host galaxies. This is a surprising phenomenon, given that the growths of black holes and host galaxies occur on their respective physical scales which are very different. Interestingly, the AGN power does not strongly correlate with the host-galaxy mass. It seems that the mass works as a ``switch'' for activating AGNs. The absence of AGNs in low-mass galaxies might be due to the absence of super-massive black holes there, but a dedicated observation of the nuclear region of nearby low-mass galaxies would be necessary to obtain a deeper insight into it.

  15. Obscured AGN at High Redshift

    Science.gov (United States)

    Stern, Daniel

    2008-01-01

    This viewgraph presentation reviews the obscured sources of Active Galactic Nuclei (AGN) in the universe at high redshift. The cosmic X-ray background, unified models of AGN and clues to galaxy formation/evolution is the motivation for this study.

  16. A Novel Method to Identify AGNs Based on Emission Line Excess and the Nature of Low-luminosity AGNs in the Sloan Digital Sky Survey: II - Nature of Low-luminosity AGNs

    CERN Document Server

    Tanaka, Masayuki

    2011-01-01

    We develop a novel method to identify active galactic nuclei (AGNs) and study the nature of low-luminosity AGNs in the Sloan Digital Sky Survey. This is the second part of a series of papers and we study the correlations between the AGN activities and host galaxy properties. Based on a sample of AGNs identified with the new method developed in Paper-I, we find that AGNs typically show extinction of tau_V=1.2 and they exhibit a wide range of ionization levels. The latter finding motivates us to use [OII]+[OIII] luminosity as an indicator of AGN power. We find that AGNs are preferentially located in massive, red, early-type galaxies. By carefully taking into account a selection bias of the Oxygen-excess method, we show that strong AGNs are located in actively star forming galaxies and rapidly growing super-massive black holes are located in rapidly growing galaxies, which clearly shows the co-evolution of super-massive black holes and the host galaxies. This is a surprising phenomenon given that the growths of ...

  17. Models of AGN feedback

    CERN Document Server

    Combes, F

    2014-01-01

    The physical processes responsible of sweeping up the surrounding gas in the host galaxy of an AGN, and able in some circumstances to expel it from the galaxy, are not yet well known. The various mechanisms are briefly reviewed: quasar or radio modes, either momentum-conserving outflows, energy-conserving outflows, or intermediate. They are confronted to observations, to know whether they can explain the M-sigma relation, quench the star formation or whether they can also provide some positive feedback and how the black hole accretion history is related to that of star formation.

  18. Reactor models for a series of continuous stirred tank reactors with a gas-liquid-solid leaching system: Part III. Model application

    Science.gov (United States)

    Papangelakis, V. G.; Demopoulos, G. P.

    1992-12-01

    A mathematical model developed to describe the steady-state performance of a three-phase leaching reactor is applied to the analysis and simulation of an industrial process: the high-temperature (180 °C to 200 °C) aqueous pressure oxidation (O2-H2SO4) of refractory pyrite-arsenopyrite (FeS2-FeAsS) gold concentrates. The simulation work reported here centers on the analysis of the autothermal operation of a continuous multistage horizontal autoclave. The focus is on the performance of the first autoclave compartment, since its autothermal “initialization” determines the rate of the whole process. The analysis of the whole autoclave is subsequently done on a stage-by-stage basis. The model considers both possible reaction control regimes, that is, reactor operation limited by the rate of the particle dissolution reaction (surface reaction control) or limited by the rate of O2 transfer at the g-1 interface (gas-transfer control). The decision whether the reactor operates under surface reaction control or gas transfer control is based on whether the gas-transfer capacity of the reactor can or cannot satisfy the oxygen demands of the leaching reactions. With the aid of the model, the effects of feed rate, feed preheating, cooling with water injection, slurry recycling, and autoclave configuration are critically evaluated from the standpoint of optimum autoclave performance.

  19. High affinity retinoic acid receptor antagonists: analogs of AGN 193109.

    Science.gov (United States)

    Johnson, A T; Wang, L; Gillett, S J; Chandraratna, R A

    1999-02-22

    A series of high affinity retinoic acid receptor (RAR) antagonists were prepared based upon the known antagonist AGN 193109 (2). Introduction of various phenyl groups revealed a preference for substitution at the para-position relative to the meta-site. Antagonists with the highest affinities for the RARs possessed hydrophobic groups, however, the presence of polar functionality was also well tolerated.

  20. AGN feedback in galaxy formation

    CERN Document Server

    Antonuccio-Delogu, Vincenzo

    2010-01-01

    During the past decade, convincing evidence has been accumulated concerning the effect of active galactic nuclei (AGN) activity on the internal and external environment of their host galaxies. Featuring contributions from well-respected researchers in the field, and bringing together work by specialists in both galaxy formation and AGN, this volume addresses a number of key questions about AGN feedback in the context of galaxy formation. The topics covered include downsizing and star-formation time scales in massive elliptical galaxies, the connection between the epochs of supermassive black h

  1. Self-Regulation of AGN in Galaxy Clusters

    CERN Document Server

    Brüggen, M

    2009-01-01

    Cool cores of galaxy clusters are thought to be heated by low-power active galactic nuclei (AGN), whose accretion is regulated by feedback. However, the interaction between the hot gas ejected by the AGN and the ambient intracluster medium is extremely difficult to simulate as it involves a wide range of spatial scales and gas that is Rayleigh-Taylor (RT) unstable. Here we present a series of three-dimensional hydrodynamical simulations of a self-regulating AGN in a galaxy cluster. Our adaptive-mesh simulations include prescriptions for radiative cooling, AGN heating and a subgrid model for RT-driven turbulence, which is crucial to simulate this evolution. AGN heating is taken to be proportional to the rest-mass energy that is accreted onto the central region of the cluster. For a wide range of feedback efficiencies, the cluster regulates itself for at least several $10^9$ years. Heating balances cooling through a string of outbursts with typical recurrence times of around 80 Myrs, a timescale that depends on...

  2. Neutrino propagation in AGN environment

    CERN Document Server

    Sahu, S; Sahu, Sarira; Bannur, Vishnu M.

    2000-01-01

    Assuming the violation of equivalence principle (VEP) by ultra high energy AGN neutrinos we study the effect of random magnetic field fluctuation on conversion of electron neutrinos to tau anti-neutrinos.

  3. Neutrino Propagation in AGN Environment

    Science.gov (United States)

    Sahu, Sarira; Bannur, Vishnu M.

    Assuming the violation of equivalence principle (VEP) by ultra high energy AGN neutrinos we study the effect of random magnetic field fluctuation on conversion of electron neutrinos to tau anti-neutrinos.

  4. The First INTEGRAL AGN Catalog

    CERN Document Server

    Beckmann, V; Shrader, C R; Soldi, S

    2006-01-01

    We present the first INTEGRAL AGN catalog, based on observations performed from launch of the mission in October 2002 until January 2004. The catalog includes 42 AGN, of which 10 are Seyfert 1, 17 are Seyfert 2, and 9 are intermediate Seyfert 1.5. The fraction of blazars is rather small with 5 detected objects, and only one galaxy cluster and no star-burst galaxies have been detected so far. A complete subset consists of 32 AGN with a significance limit of 7 sigma in the INTEGRAL/ISGRI 20-40 keV data. Although the sample is not flux limited, the distribution of sources shows a ratio of obscured to unobscured AGN of 1.5 - 2.0, consistent with luminosity dependent unified models for AGN. Only four Compton-thick AGN are found in the sample. Based on the INTEGRAL data presented here, the Seyfert 2 spectra are slightly harder (Gamma = 1.95 +- 0.01) than Seyfert 1.5 (Gamma = 2.10 +- 0.02) and Seyfert 1 (Gamma = 2.11 +- 0.05).

  5. Student Collaboration in a Series of Integrated Experiments to Study Enzyme Reactor Modeling with Immobilized Cell-Based Invertase

    Science.gov (United States)

    Taipa, M. A^ngela; Azevedo, Ana M.; Grilo, Anto´nio L.; Couto, Pedro T.; Ferreira, Filipe A. G.; Fortuna, Ana R. M.; Pinto, Ine^s F.; Santos, Rafael M.; Santos, Susana B.

    2015-01-01

    An integrative laboratory study addressing fundamentals of enzyme catalysis and their application to reactors operation and modeling is presented. Invertase, a ß-fructofuranosidase that catalyses the hydrolysis of sucrose, is used as the model enzyme at optimal conditions (pH 4.5 and 45 °C). The experimental work involves 3 h of laboratory time…

  6. The Second INTEGRAL AGN Catalogue

    CERN Document Server

    Beckmann, V; Ricci, C; Alfonso-Garzón, J; Courvoisier, T J -L; Domingo, A; Gehrels, N; Lubinski, P; Mas-Hesse, J M; Zdziarski, A A

    2009-01-01

    The INTEGRAL mission provides a large data set for studying the hard X-ray properties of AGN and allows to test the unified scheme for AGN. We present analysis of INTEGRAL IBIS/ISGRI, JEM-X, and OMC data for 199 AGN that have been reported to be detected by INTEGRAL above 20 keV. The data analysed here allow a significant spectral extraction on 148 objects and optical variability study of 57 AGN. The slopes of the hard X-ray spectra of Seyfert 1 and Seyfert 2 galaxies are found to be consistent within the uncertainties, whereas lower luminosities are measured for the more absorbed / type 2 AGN. The intermediate Seyfert 1.5 objects exhibit hard X-ray spectra consistent with those of Seyfert 1. When applying a Compton reflection model, the underlying continua appear still the same in Seyfert 1 and 2 with photon index 2, and the reflection strength is about R = 1, when assuming different inclination angles. A significant correlation is found between the hard X-ray and optical luminosity and the mass of the centr...

  7. Lessons learnt from INTEGRAL AGN

    CERN Document Server

    Beckmann, V; Soldi, S; Alfonso-Garzon, J; Courvoisier, T J -L; Domingo, A; Gehrels, N; Lubinski, P; Mas-Hesse, J M; Zdziarski, A A

    2010-01-01

    The INTEGRAL mission provides a large data set for studying the hard X-ray properties of AGN and allows to test the unified scheme for AGN. We present results based on the analysis of 199 AGN. A difference between the Seyfert types is detected in slightly flatter spectra with higher cut-off energies and lower luminosities for the more absorbed/type 2 AGN. When applying a Compton reflection model, the underlying continua (photon index 1.95) appear the same in Seyfert 1 and 2, and the reflection strength is R=1 in both cases, with differences in the inclination angle only. A difference is seen in the sense that Seyfert 1 are on average twice as luminous in hard X-rays than the Seyfert 2 galaxies. The unified model for Seyfert galaxies seems to hold, showing in hard X-rays that the central engine is the same in Seyfert 1 and 2 galaxies, seen under different inclination angle and absorption. Based on our knowledge of AGN from INTEGRAL data, we briefly outline open questions and investigations to answer them. In t...

  8. IR properties of AGN and SB

    Science.gov (United States)

    Talezade Lari, M. H.; Davoudifar, P.; Mickaelian, A. M.

    2016-09-01

    Through multi-wavelength flux ratios it is possible to detect AGN and Star-burst Galaxies. Techniques of detecting extragalactic objects as well as AGN are studied in different wavelengths (X-Ray, Radio and IR). Specification of AGN as IR and radio sources is discussed. IR catalogues of 2MASS and WISE were used to study the interrelationship between interactions/merging, starburst and AGN phenomena.

  9. CERN Library | Agnes Chavez @ CERN | 17 March

    CERN Multimedia

    2015-01-01

    Agnes Chavez will present her work on Tuesday, 17 March 2015 at 4 p.m. in the Library (Builidng. 52-1-052) Coffee will be served from 3.30 p.m.   Agnes Chavez is an artist and educator participating in a two-week research stay organised by the ATLAS Experiment at CERN. Chavez is using the stay to develop her art and education project, Projecting pARTicles, which will be exploring particle physics through projection art. Chavez experiments with data visualization, sound and projection art to create participatory environments. She collaborates with programmers to create algorithmic drawings projected on to buildings, walls and spaces. This work explores our relationship with nature and technology, and how these and other sensory experiences determine how we perceive and interpret the world around us. For the Projecting pARTicles series she has formed an interdisciplinary team of programmers, artists, scientists and educators to investigate how we can create art and education interventions inspire...

  10. AGN identification: what lies ahead

    Science.gov (United States)

    Fotopoulou, Sotiria

    2016-08-01

    Classification has been one the first concerns of modern astronomy, starting from stars sorted in the famous Harvard classification system and promptly followed by the morphological classification of galaxies by none other than Edwin Hubble himself (Hubble 1926). Both classification schema are essentially connected to the physics of the objects reflecting the temperature for stars and e.g. the age of the star population for galaxies. Systematic observations of galaxies have revealed the intriguing class of Active Galactic Nuclei (AGN), objects of tremendous radiation that do not share the same properties of what we now call normal galaxies. Observations have led to the definition of distinct and somewhat arbitrary categories (Seyfert galaxies, quasars, QSO, radio AGN, etc), essentially rediscovering the many faces of the same phenomenon, up until the unification of AGN (Antonucci 1993, Urry and Padovani 1995). Even after the realization that all AGN have the same engine powering their amazing radiation, astronomers are still using and refining the selection criteria within their favorite electromagnetic range in the hope to better understand the impact of the AGN phenomenon in the greater context of galaxy evolution. In the dawn of Big Data astronomy we find ourselves equipped with new tools. I will present the prospects of machine learning methods in better understanding the AGN population. Namely, I will show results from supervised learning algorithms whereby a labeled training set is used to amalgamate decision tree(s) (Fotopoulou et al., 2016) or neural network(s), and unsupervised learning where the algorithm performs clustering analysis of the full dataset in a multidimensional space identifying clusters of objects sharing potentially the same physical properties (Fotopoulou in prep.).

  11. SOLUCIÓN ANALÍTICA PARA OBTENER EL VOLUMEN ÓPTIMO DE UNA SERIE DE REACTORES DE AGITACIÓN CONTINUA DONDE SE EFECTÚA UNA REACCIÓN DE PRIMER ORDEN

    Directory of Open Access Journals (Sweden)

    Ignacio Elizalde

    2013-01-01

    Full Text Available An analytical procedure for determining the optimum size of CSTR in series operating under isothermal and isobaric conditions sustaining first order reaction at constant density has been developed. The procedure requires the concentration of reactant at the entrance of the first reactor and at the outlet of the last reactor; it is also required the continuity of reaction rate as function of conversion, due to the later changes from one reactor to another. The optimization method involves the calculation of intermediate concentrations instead of their estimation, as it is done by graphical solution reported previously. Also, the procedure reported in this contribution is valid for any reactor number. Under these circumstances the method predicts that all reactors must have the same size in order to minimize the total volume of the system.

  12. The AGN phenomenon: open issues

    CERN Document Server

    Beckmann, Volker

    2013-01-01

    The aim of this short paper is to motivate and encourage research in the field of Active Galactic Nuclei (AGN). Here we summarize the main open questions concerning the central engine. Is the central black hole rapidly spinning and can we prove this? What is the dominant accretion mechanism in AGN? Why do some AGN form jets while others don't and how do the jets originate? What keeps jets collimated out to distances of 100 kpc? Is the emission of blazars dominated rather by synchrotron self-Compton or by external Compton processes? Which parameters are important in the unified model? We outline the status of related research, formulate the questions and try to hint at research projects able to tackle these fundamental topics. Deep surveys, polarization measurements, improved models, faster and more accurate simulations as well as bridging the gap in the MeV range can be part of the tools to bring us closer to an understanding of AGN.

  13. Radio properties of local AGN

    NARCIS (Netherlands)

    Nagar, NM; Falcke, H; Wilson, AS; Mujica, R; Maiolino, R

    2004-01-01

    This article focuses on the radio properties of the similar to 470 nearby bright (northern) galaxies of the Palomar spectroscopic sample. Almost half the sample's galaxies have nuclei with emission-lines characteristic of AGN but with L-H alpha = 50% of all LLAGNs; there is no evidence against all L

  14. Results from the First INTEGRAL AGN Catalogue

    CERN Document Server

    Beckmann, V; Shrader, C R; Gehrels, N

    2005-01-01

    We present results based on the first INTEGRAL AGN catalogue. The catalogue includes 42 AGN, of which 10 are Seyfert 1, 17 are Seyfert 2, and 9 are intermediate Seyfert 1.5. The fraction of blazars is rather small with 5 detected objects, and only one galaxy cluster and no star-burst galaxies have been detected so far. The sample consists of bright (fx > 5e-12 erg/cm**2/s), low luminosity (L = 2e43 erg/s), local (z = 0.020) AGN. Although the sample is not flux limited, we find a ratio of obscured to unobscured AGN of 1.5 - 2.0, consistent with luminosity dependent unified models for AGN. Only four Compton-thick AGN are found in the sample. This implies that the missing Compton-thick AGN needed to explain the cosmic hard X-ray background would have to have lower fluxes than discovered by INTEGRAL so far.

  15. Fading AGN Candidates: AGN Histories and Outflow Signatures

    Science.gov (United States)

    Keel, William C.; Lintott, Chris J.; Maksym, W. Peter; Bennert, Vardha N.; Chojnowski, S. Drew; Moiseev, Alexei; Smirnova, Aleksandrina; Schawinski, Kevin; Sartori, Lia F.; Urry, C. Megan; Pancoast, Anna; Schirmer, Mischa; Scott, Bryan; Showley, Charles; Flatland, Kelsi

    2017-02-01

    We consider the energy budgets and radiative history of eight fading active galactic nuclei (AGNs), identified from an energy shortfall between the requirements to ionize very extended (radius > 10 kpc) ionized clouds and the luminosity of the nucleus as we view it directly. All show evidence of significant fading on timescales of ≈50,000 yr. We explore the use of minimum ionizing luminosity Qion derived from photoionization balance in the brightest pixels in Hα at each projected radius. Tests using presumably constant Palomar–Green QSOs, and one of our targets with detailed photoionization modeling, suggest that we can derive useful histories of individual AGNs, with the caveat that the minimum ionizing luminosity is always an underestimate and subject to uncertainties about fine structure in the ionized material. These consistency tests suggest that the degree of underestimation from the upper envelope of reconstructed Qion values is roughly constant for a given object and therefore does not prevent such derivation. The AGNs in our sample show a range of behaviors, with rapid drops and standstills; the common feature is a rapid drop in the last ≈2 × 104 yr before the direct view of the nucleus. The e-folding timescales for ionizing luminosity are mostly in the thousands of years, with a few episodes as short as 400 yr. In the limit of largely obscured AGNs, we find additional evidence for fading from the shortfall between even the lower limits from recombination balance and the maximum luminosities derived from far-infrared fluxes. We compare these long-term light curves, and the occurrence of these fading objects among all optically identified AGNs, to simulations of AGN accretion; the strongest variations over these timespans are seen in models with strong and local (parsec-scale) feedback. We present Gemini integral-field optical spectroscopy, which shows a very limited role for outflows in these ionized structures. While rings and loops of emission

  16. Pharmacokinetics of a novel retinoid AGN 190168 and its metabolite AGN 190299 after intravenous administration of AGN 190168 to rats.

    Science.gov (United States)

    Hsyu, P H; Bowen, B; Tang-Liu, D

    1994-07-01

    The pharmacokinetics of AGN 190168, a novel synthetic retinoid, and its major metabolite, AGN 190299, in rat blood after intravenous administration was investigated. Approximately 4.4 mg kg-1 (high dose) or 0.49 mg kg-1 (low dose) of AGN 190168 was administered to rats via the femoral vein. Blood was collected from the femoral artery at various time points during an 8 h period. Blood concentrations of AGN 190168 and AGN 190299 were determined by a specific and sensitive high-pressure liquid chromatographic (HPLC) method. AGN 190168 was rapidly metabolized in rats. The only detectable drug-related species in the blood was AGN 190299. Therefore, only pharmacokinetics of AGN 190299 were calculated. Elimination of AGN 190299 appeared to be non-linear after administration of the high dose, and linear after administration of the low dose. The maximum elimination rate (Vmax) and the concentration at half of the Vmax (km), as estimated by a Michaelis-Menten one-compartment model, were 7.58 +/- 2.42 micrograms min-1 (mean +/- SD) and 6.10 +/- 1.58 micrograms mL-1, respectively. The value of the area under the blood concentration time curve (AUC) was 9.54 +/- 1.68 micrograms h mL-1 after administration of the high dose and 0.594 +/- 0.095 micrograms h mL-1 after administration of the low dose. The clearance value was 7.79 +/- 1.20 mL min-1 kg-1 after the high dose, statistically significantly different from that after the low dose (p AGN 190168 to AGN 190299, non-linear pharmacokinetics of AGN 190299 after the 4.4 mg kg-1 dose, and the lack of difference in disposition profiles between sexes after intravenous administration of AGN 190168 to rats.

  17. ROSA-III base test series for a large break loss-of-coolant accident in a boiling water reactor

    Energy Technology Data Exchange (ETDEWEB)

    Tasaka, K.; Abe, N.; Anoda, Y.; Koizumi, Y.; Shiba, M.

    1982-05-01

    The rig of safety assessment (ROSA)-III facility is a volumetrically scaled (1/424) boiling water reactor (BWR) system with an electrically heated core designed for integral loss-of-coolant accident (LOCA) and emergency core cooling system (ECCS) tests. It is confirmed from the experimental results obtained so far that the ROSA-III test facility can simulate major aspects of a BWR LOCA, such as boiling transition by lowering of the mixture level in the core, rewetting by the lower plenum flashing, and final quenching by the ECCS. The overall agreement between the calculated results by the RELAP5/ MOD0 code and the experimental results is good; however, the calculated lower plenum flashing rewetted the whole core and the calculated cladding temperature considerably underpredicts the measured value at the upper part of the core.

  18. Modeling optical and UV polarization of AGNs III. From uniform-density to clumpy regions

    CERN Document Server

    Marin, F; Gaskell, C M

    2015-01-01

    A growing body of evidence suggests that part of, if not all, scattering regions of active galactic nuclei (AGNs) are clumpy. Hence. in this paper, we run radiative transfer models in the optical/UV for a variety of AGN reprocessing regions with different distributions of clumpy scattering media. We use the latest version of the Monte Carlo code STOKES presented in the first two papers of this series to model AGN reprocessing regions of increasing morphological complexity. We replace previously uniform-density media with up to thousands of constant-density clumps. We couple a continuum source to fragmented equatorial scattering regions, polar outflows, and toroidal, obscuring dust regions and investigate a wide range of geometries. We also consider different levels of fragmentation in each scattering region to evaluate importance of fragmentation for the net polarization of the AGN. We find that, in comparison with uniform-density models, equatorial distributions of gas and dust clouds result in grayer spectr...

  19. Understanding Active Galactic Nuclei using near-infrared high angular resolution polarimetry I : MontAGN - STOKES comparison

    Science.gov (United States)

    Grosset, L.; Marin, F.; Gratadour, D.; Goosmann, R.; Rouan, D.; Clénet, Y.; Pelat, D.; Rojas Lobos, P. A.

    2016-12-01

    In this first research note of a series of two, we present a comparison between two Monte Carlo radiative transfer codes: MontAGN and STOKES. Both were developed in order to better understand the observed polarisation of Active Galactic Nuclei (AGN). Our final aim is to use these radiative transfer codes to simulate the polarisation maps of a prototypical type-2 radio-quiet AGN on a wide range of wavelengths, from the infrared band with MontAGN to the X-ray energies with STOKES. Doing so, we aim to analyse in depth the recent SPHERE/IRDIS polarimetric observations conducted on NGC 1068. In order to validate the codes and obtain preliminary results, we set for both codes a common and simple AGN model, and compared their polaro-imaging results.

  20. Understanding active galactic nuclei using near-infrared high angular resolution polarimetry I : MontAGN - stokes comparison

    CERN Document Server

    Grosset, Lucas; Gratadour, Damien; Goosmann, René; Rouan, Daniel; Clénet, Yann; Pelat, Didier; Lobos, Patricia Andrea Rojas

    2016-01-01

    In this first research note of a series of two, we present a comparison between two Monte Carlo radiative transfer codes: MontAGN and STOKES. Both were developed in order to better understand the observed polarisation of Active Galactic Nuclei (AGN). Our final aim is to use these radiative transfer codes to simulate the polarisation maps of a prototypical type-2 radio-quiet AGN on a wide range of wavelengths, from the infrared band with MontAGN to the X-ray energies with STOKES. Doing so, we aim to analyse in depth the recent SPHERE/IRDIS polarimetric observations conducted on NGC 1068. In order to validate the codes and obtain preliminary results, we set for both codes a common and simple AGN model, and compared their polaro-imaging results.

  1. Gamma-ray-selected AGN

    Science.gov (United States)

    Giommi, Paolo

    2016-08-01

    The gamma-ray band is the most energetic part of the electromagnetic spectrum. As such it is also where selection effects are most severe, as it can only be reached by the most extreme non-thermal AGN. Blazars, with their emission dominated by non-thermal blue-shifted radiation arising in a relativistic jet pointed in the direction of the observer, naturally satisfy this though requirement. For this reason, albeit these sources are intrisically very rare (orders of magnitude less abundant than radio quiet AGN of the same optical magnitude) they almost completely dominate the extragalactic gamma-ray and very high energy sky. I will discuss the emission of different types of blazars and the selection effects that are at play in the gamma-ray band based on recent results from the current generation of gamma-ray astronomy satellites, ground-based Cherenkov telescopes, and Monte Carlo simulations.

  2. Highlights from the VERITAS AGN Observation Program

    CERN Document Server

    Benbow, Wystan

    2015-01-01

    The VERITAS array of four 12-m imaging atmospheric-Cherenkov telescopes began full-scale operations in 2007, and is one of the world's most sensitive detectors of astrophysical VHE (E>100 GeV) $\\gamma$-rays. Observations of active galactic nuclei (AGN) are a major focus of the VERITAS Collaboration, and more than 60 AGN, primarily blazars, are known to emit VHE photons. Approximately 3400 hours have been devoted to the VERITAS AGN observation program and roughly 160 AGN are already observed with the array, in most cases with the deepest VHE exposure to date. These observations have resulted in 34 detections, most of which are accompanied by contemporaneous, multi-wavelength observations, enabling a more detailed study of the underlying jet-powered processes. Recent highlights of the VERITAS AGN observation program, and the collaboration's long-term AGN observation strategy, are presented.

  3. Comparing Simulations of AGN Feedback

    Science.gov (United States)

    Richardson, Mark L. A.; Scannapieco, Evan; Devriendt, Julien; Slyz, Adrianne; Thacker, Robert J.; Dubois, Yohan; Wurster, James; Silk, Joseph

    2016-07-01

    We perform adaptive mesh refinement (AMR) and smoothed particle hydrodynamics (SPH) cosmological zoom simulations of a region around a forming galaxy cluster, comparing the ability of the methods to handle successively more complex baryonic physics. In the simplest, non-radiative case, the two methods are in good agreement with each other, but the SPH simulations generate central cores with slightly lower entropies and virial shocks at slightly larger radii, consistent with what has been seen in previous studies. The inclusion of radiative cooling, star formation, and stellar feedback leads to much larger differences between the two methods. Most dramatically, at z=5, rapid cooling in the AMR case moves the accretion shock to well within the virial radius, while this shock remains near the virial radius in the SPH case, due to excess heating, coupled with poorer capturing of the shock width. On the other hand, the addition of feedback from active galactic nuclei (AGNs) to the simulations results in much better agreement between the methods. For our AGN model, both simulations display halo gas entropies of 100 keV cm2, similar decrements in the star formation rate, and a drop in the halo baryon content of roughly 30%. This is consistent with the AGN growth being self-regulated, regardless of the numerical method. However, the simulations with AGN feedback continue to differ in aspects that are not self-regulated, such that in SPH a larger volume of gas is impacted by feedback, and the cluster still has a lower entropy central core.

  4. AGN Physics from QSO Clustering

    CERN Document Server

    Croom, S; Shanks, T; Outram, P J; Smith, R; Miller, L; Loaring, N; Kenyon, S; Couch, W; Croom, Scott; Boyle, Brian; Shanks, Tom; Outram, Phil; Smith, Robert; Miller, Lance; Loaring, Nicola; Kenyon, Suzanne; Couch, Warrick

    2003-01-01

    We review the current status of QSO clustering measurements, particular with respect to their relevance in understanding AGN physics. Measurements based on the 2dF QSO Redshift Survey (2QZ) find a scale length for QSO clustering of s_0=5.76(+0.17-0.27) h-1 Mpc at a redshift ~1.5, very similar to low redshift galaxies. There is no evidence of evolution in the clustering of QSOs from z~0.5 to z~2.2. This lack of evolution and low clustering amplitude suggests a short life time for AGN activity of the order ~10^6-10^7 years. Large surveys such at the 2QZ and SDSS also allow the the study of QSO environments in 3D for the first time (at least at low redshift), early results from this work seem to show no difference between the environments of QSOs and normal galaxies. Future studies e.g. measuring clustering as a function of black hole mass, and deep QSO surveys should provide further insight into the formation and evolution of AGN.

  5. Extracting Information from AGN Variability

    CERN Document Server

    Kasliwal, Vishal P; Richards, Gordon T

    2016-01-01

    AGN exhibit rapid, high amplitude stochastic flux variability across the entire electromagnetic spectrum on timescales ranging from hours to years. The cause of this variability is poorly understood. We present a new method for using variability to (1) measure the time-scales on which flux perturbations evolve and (2) characterize the driving flux perturbations. We model the observed light curve of an AGN as a linear differential equation driven by stochastic impulses. Physically, the impulses could be local `hot-spots' in the accretion disk---the linear differential equation then governs how the hot spots evolve and dissipate. The impulse-response function of the accretion disk material is given by the Green's function of the linear differential equation. The timescales on which the hot-spots radiate energy is characterized by the powerspectrum of the driving stochastic impulses. We analyze the light curve of the \\Kepler AGN Zw 229-15 and find that the observed variability behavior can be modeled as a damped...

  6. Detecting Dual AGN at High Redshift

    Science.gov (United States)

    Barrows, Robert S.

    2012-01-01

    The existence of supermassive black holes (SMBHs) in most, if not all, galaxies, along with observations of galaxy mergers, suggests that pairs of SMBHs should exist for some time in the merger remnant. Observational evidence for these systems at kpc-scale separations (i.e. dual AGN) has dramatically increased recently through a combination of spectral and morphological selections. I discuss observations of CXOXBJ142607.6+353351 (CXOJ1426+35), a candidate dual AGN at z=1.175, and put its properties, including significant obscuration, within the context of other candidate/confirmed dual AGN at lower redshifts. Though dual AGN are expected to be more common at higher redshifts, they are more difficult to detect. Furthermore, adding to the difficulties of detection are a number of other physical mechanisms which can mimic the spectroscopic signature of two Type 2 AGN. In particular, I will discuss the possibility of strong outflows from an AGN. These outflow phenomena can be an important feedback mechanism in galaxies and are apparently common in AGN, making them a viable alternative to the dual AGN scenario. Based on our candidate's luminosity and emission line intensities, we find that an outflow is a possibility. If this is the case, such an outflow would be especially strong and has implications for AGN feedback in galaxies. However, the dual AGN scenario cannot be ruled out, and at z=1.175, the two putative AGN could potentially be resolved with Chandra. Other candidate dual AGN at similar redshifts and with significant obscuration could also be confirmed this way. This research was sponsored by the Strategic University Research Partnership Program, the National Aeronautics and Space Administration and the Arkansas NASA EPSCoR program.

  7. Host Galaxy Morphology and the AGN Unified Model

    CERN Document Server

    Trump, Jonathan R

    2011-01-01

    We use a sample of active galaxies from the Cosmic Evolution Survey to show that host galaxy morphology is tied to the accretion rate and X-ray obscuration of its active galactic nucleus (AGN). Unobscured and rapidly accreting broad-line AGNs are more likely to be in spheroid-dominated hosts than weak or obscured AGNs, and obscured AGNs are more likely to have disturbed host galaxies. Much of the disagreement in previous work on the AGN-merger connection is likely due to each study probing AGNs with different obscuration and accretion properties. Only obscured AGNs seem to merger-driven, while weak AGNs are fed by stochastic processes in disks, and rapidly-accreting broad-line AGNs require massive bulges. Our observed "unified model" for AGN hosts fits with theoretical models for merger-driven AGN evolution, but is also consistent with steady-state AGN activity.

  8. The Study of Relativistic AGN Jets and Experimental Survey of AGN Properties

    Science.gov (United States)

    Sabzali, V.; Davoudifar, P.; Mickaelian, A. M.

    2016-09-01

    AGN, their evolution and their relativistic jets were studied on the basis of data from multi-wavelength surveys. NRAO VLA Sky Survey (NVSS) and VLBI were used to study radio jets and radio continuum emission of AGN. A population of AGN will be selected and used in a future optical survey for their jets.

  9. The OPTX Project V: Identifying Distant AGNs

    CERN Document Server

    Trouille, L; Tremonti, C

    2011-01-01

    The Baldwin, Phillips, and Terlevich emission-line ratio diagnostic ([OIII]/H{\\beta} versus [NII]/H{\\alpha}, hereafter BPT diagram) efficiently separates galaxies whose signal is dominated by star formation from those dominated by AGN activity (BPT-AGN). Yet this BPT diagram is limited to z = 1.0 +/-0.4) and has a high X-ray luminosity to total infrared luminosity ratio. This suggests that, on average, the X-ray signal in BPT-comp is dominated by obscured or low accretion rate AGN activity rather than by star formation, supporting their inclusion in the TBT-AGN regime.

  10. Nuclear Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Hogerton, John

    1964-01-01

    This pamphlet describes how reactors work; discusses reactor design; describes research, teaching, and materials testing reactors; production reactors; reactors for electric power generation; reactors for supply heat; reactors for propulsion; reactors for space; reactor safety; and reactors of tomorrow. The appendix discusses characteristics of U.S. civilian power reactor concepts and lists some of the U.S. reactor power projects, with location, type, capacity, owner, and startup date.

  11. Unravelling the complex structure of AGN-driven outflows: II. Photoionization and energetics

    CERN Document Server

    Karouzos, Marios; Bae, Hyun-Jin

    2016-01-01

    Outflows have been shown to be prevalent in galaxies hosting luminous active galactic nuclei (AGNs) and present a physically plausible way to couple the AGN energy output with the interstellar medium of their hosts. Despite their prevalence, accurate characterization of these outflows has been challenging. In the second of a series of papers, we use Gemini Multi-Object Spectrograph IFU data of 6 local (z<0.1) and moderate-luminosity Type 2 AGNs to study the ionization properties and energetics of AGN-driven outflows. We find strong evidence that connect the extreme kinematics of the ionized gas with the AGN photoionization. The kinematic component related to the AGN-driven outflow is clearly separated from other kinematic components, such as virial motions or rotation, on the velocity and velocity dispersion diagram. Our spatially resolved kinematic analysis reveals that from 30% up to 90% of the total mass and kinetic energy of the outflow is contained within the central kpc of the galaxy. The spatially i...

  12. AGN Unification at z ~ 1: u - R Colors and Gradients in X-ray AGN Hosts

    CERN Document Server

    Ammons, S Mark; Koo, David C; Dutton, Aaron A; Melbourne, Jason; Max, Claire E; Mozena, Mark; Kocevski, Dale D; McGrath, Elizabeth J; Bouwens, Rychard J; Magee, Daniel K

    2011-01-01

    We present uncontaminated rest-frame u - R colors of 78 X-ray-selected AGN hosts at 0.5 1.1 kpc. These three observations imply that AGN obscuration is uncorrelated with the star formation rate beyond ~1 kpc. These observations favor a unification scenario for intermediate-luminosity AGNs in which obscuration is determined geometrically. Scenarios in which the majority of intermediate-luminosity AGN at z ~ 1 are undergoing rapid, galaxy-wide quenching due to AGN-driven feedback processes are disfavored.

  13. SWIFT BAT Survey of AGN

    Science.gov (United States)

    Tueller, J.; Mushotzky, R. F.; Barthelmy, S.; Cannizzo, J. K.; Gehrels, N.; Markwardt, C. B.; Skinner, G. K.; Winter, L. M.

    2008-01-01

    We present the results1 of the analysis of the first 9 months of data of the Swift BAT survey of AGN in the 14-195 keV band. Using archival X-ray data or follow-up Swift XRT observations, we have identified 129 (103 AGN) of 130 objects detected at [b] > 15deg and with significance > 4.8-delta. One source remains unidentified. These same X-ray data have allowed measurement of the X-ray properties of the objects. We fit a power law to the logN - log S distribution, and find the slope to be 1.42+/-0.14. Characterizing the differential luminosity function data as a broken power law, we find a break luminosity logL*(ergs/s)= 43.85+/-0.26. We obtain a mean photon index 1.98 in the 14-195 keV band, with an rms spread of 0.27. Integration of our luminosity function gives a local volume density of AGN above 10(exp 41) erg/s of 2.4x10(exp -3) Mpc(sup -3), which is about 10% of the total luminous local galaxy density above M* = -19.75. We have obtained X-ray spectra from the literature and from Swift XRT follow-up observations. These show that the distribution of log nH is essentially flat from nH = 10(exp 20)/sq cm to 10(exp 24)/sq cm, with 50% of the objects having column densities of less than 10(exp 22)/sq cm. BAT Seyfert galaxies have a median redshift of 0.03, a maximum log luminosity of 45.1, and approximately half have log nH > 22.

  14. AGN Winds and Blazar Phenomenology

    Science.gov (United States)

    Kazanas, Demos

    2012-01-01

    The launch of {\\em Fermi} produced a significant number of AGN detections to allow statistical treatment of their properties. One of the first such systematics was the "Blazar Divide" in FSRQs and BL Lacs according to their gamma-ray spectral index and luminosity. Further data accumulation indicated this separation to be less clear than thought before. An MHD wind model which can model successfully the Seyfert X-ray absorber properties provides the vestiges of an account of the observed blazar classification. We propose to employ this model to model in detail the broad band blazar spectra and their statistical properties in terms of the physical parameters of these MHD winds.

  15. AGN Zoo and Classifications of Active Galaxies

    Science.gov (United States)

    Mickaelian, Areg M.

    2015-07-01

    We review the variety of Active Galactic Nuclei (AGN) classes (so-called "AGN zoo") and classification schemes of galaxies by activity types based on their optical emission-line spectrum, as well as other parameters and other than optical wavelength ranges. A historical overview of discoveries of various types of active galaxies is given, including Seyfert galaxies, radio galaxies, QSOs, BL Lacertae objects, Starbursts, LINERs, etc. Various kinds of AGN diagnostics are discussed. All known AGN types and subtypes are presented and described to have a homogeneous classification scheme based on the optical emission-line spectra and in many cases, also other parameters. Problems connected with accurate classifications and open questions related to AGN and their classes are discussed and summarized.

  16. Spectral Energy Distributions of Quasars and AGN

    Science.gov (United States)

    Wilkes, B.

    2004-06-01

    Active Galactic Nuclei (AGN) are multiwavelength emitters. To have any hope of understanding them, or even to determine their energy output, we must observe them in multiple wavebands using many telescopes. I will review what we have learned from broad-band observations of relatively bright, low-redshift AGN over the past ˜ 15 years. AGN can be found at all wavelengths but each provides a different view of the intrinsic population, often with little overlap between samples selected in different wavebands. I look forward to the full view of the intrinsic population which we will obtain over the next few years with surveys using today's new, sensitive observatories. These surveys are already finding enough new and different AGN candidates to pose the question ``What IS an AGN?".

  17. Radio Loud AGNs are Mergers

    CERN Document Server

    Chiaberge, Marco; Lotz, Jennifer; Norman, Colin

    2015-01-01

    We measure the merger fraction of Type 2 radio-loud and radio-quiet active galactic nuclei at z>1 using new samples. The objects have HST images taken with WFC3 in the IR channel. These samples are compared to the 3CR sample of radio galaxies at z>1 and to a sample of non-active galaxies. We also consider lower redshift radio galaxies with HST observations and previous generation instruments (NICMOS and WFPC2). The full sample spans an unprecedented range in both redshift and AGN luminosity. We perform statistical tests to determine whether the different samples are differently associated with mergers. We find that all (92%) radio-loud galaxies at z>1 are associated with recent or ongoing merger events. Among the radio-loud population there is no evidence for any dependence of the merger fraction on either redshift or AGN power. For the matched radio-quiet samples, only 38% are merging systems. The merger fraction for the sample of non-active galaxies at z>1 is indistinguishable from radio-quiet objects. This...

  18. A Brief History of AGN

    CERN Document Server

    Shields, G A

    1999-01-01

    Astronomers knew early in the twentieth century that some galaxies have emission-line nuclei. However, even the systematic study by Seyfert (1943) was not enough to launch active galactic nuclei (AGN) as a major topic of astronomy. The advances in radio astronomy in the 1950s revealed a new universe of energetic phenomena, and inevitably led to the discovery of quasars. These discoveries demanded the attention of observers and theorists, and AGN have been a subject of intense effort ever since. Only a year after the recognition of the redshifts of 3C 273 and 3C 48 in 1963, the idea of energy production by accretion onto a black hole was advanced. However, acceptance of this idea came slowly, encouraged by the discovery of black hole X-ray sources in our Galaxy and, more recently, supermassive black holes in the center of the Milky Way and other galaxies. Many questions remain as to the formation and fueling of the hole, the geometry of the central regions, the detailed emission mechanisms, the production of j...

  19. A New Catalogue of Type 1 AGN and its Implication on the AGN Unified Model

    CERN Document Server

    Oh, Kyuseok; Schawinski, Kevin; Koss, Michael; Trakhtenbrot, Benny

    2015-01-01

    We have newly identified a substantial number of type 1 active galactic nuclei (AGN) featuring weak broad-line regions (BLRs) at z < 0.2 from detailed analysis of galaxy spectra in the Sloan Digital Sky Survey Data Release 7. These objects predominantly show a stellar continuum but also a broad H-alpha emission line, indicating the presence of a low-luminosity AGN oriented so that we are viewing the central engine directly without significant obscuration. These accreting black holes have previously eluded detection due to their weak nature. The new BLR AGNs we found increased the number of known type 1 AGNs by 49%. Some of these new BLR AGNs were detected at the Chandra X-ray Observatory, and their X-ray properties confirm that they are indeed type 1 AGN. Based on our new and more complete catalogue of type 1 AGNs, we derived the type 1 fraction of AGNs as a function of [OIII] 5007 emission luminosity and explored the possible dilution effect on the obscured AGN due to star-formation. The new type 1 AGN fr...

  20. The 60-month all-sky BAT Survey of AGN and the Anisotropy of Nearby AGN

    Energy Technology Data Exchange (ETDEWEB)

    Ajello, M.; /KIPAC, Menlo Park; Alexander, D.M.; /Durham U.; Greiner, J.; /Garching, Max Planck Inst., MPE; Madejski, G.M.; /KIPAC, Menlo Park; Gehrels, N.; /NASA, Goddard; Burlon, D.; /Garching, Max Planck Inst., MPE

    2012-04-02

    Surveys above 10 keV represent one of the the best resources to provide an unbiased census of the population of Active Galactic Nuclei (AGN). We present the results of 60 months of observation of the hard X-ray sky with Swift/BAT. In this timeframe, BAT detected (in the 15-55 keV band) 720 sources in an all-sky survey of which 428 are associated with AGN, most of which are nearby. Our sample has negligible incompleteness and statistics a factor of {approx}2 larger over similarly complete sets of AGN. Our sample contains (at least) 15 bona-fide Compton-thick AGN and 3 likely candidates. Compton-thick AGN represent a {approx}5% of AGN samples detected above 15 keV. We use the BAT dataset to refine the determination of the LogN-LogS of AGN which is extremely important, now that NuSTAR prepares for launch, towards assessing the AGN contribution to the cosmic X-ray background. We show that the LogN-LogS of AGN selected above 10 keV is now established to a {approx}10% precision. We derive the luminosity function of Compton-thick AGN and measure a space density of 7.9{sub -2.9}{sup +4.1} x 10{sup -5} Mpc{sup -3} for objects with a de-absorbed luminosity larger than 2 x 10{sup 42} erg s{sup -1}. As the BAT AGN are all mostly local, they allow us to investigate the spatial distribution of AGN in the nearby Universe regardless of absorption. We find concentrations of AGN that coincide spatially with the largest congregations of matter in the local ({le} 85 Mpc) Universe. There is some evidence that the fraction of Seyfert 2 objects is larger than average in the direction of these dense regions.

  1. AGN polarization modeling with STOKES

    CERN Document Server

    Goosmann, R W; Shoji, M; Goosmann, Rene W.

    2007-01-01

    We introduce a new, publicly available Monte Carlo radiative transfer code, STOKES, which has been developed to model polarization induced by scattering off free electrons and dust grains. It can be used in a wide range of astrophysical applications. Here, we apply it to model the polarization produced by the equatorial obscuring and scattering tori assumed to exist in active galactic nuclei (AGNs). We present optical/UV modeling of dusty tori with a curved inner shape and for two different dust types: one composition reproduces extinction properties of our Galaxy, and the other is derived from composite quasar spectra. The polarization spectra enable us to clearly distinguish between the two dust compositions. The STOKES code and its documentation can be freely downloaded from http://www.stokes-program.info/.

  2. Comparing Simulations of AGN Feedback

    CERN Document Server

    Richardson, Mark L A; Devriendt, Julien; Slyz, Adrianne; Thacker, Robert J; Dubois, Yohan; Wurster, James; Silk, Joseph

    2016-01-01

    We perform adaptive mesh refinement (AMR) and smoothed particle hydrodynamics (SPH) cosmological zoom simulations of a region around a forming galaxy cluster, comparing the ability of the methods to handle successively more complex baryonic physics. In the simplest, non-radiative case, the two methods are in good agreement with each other, but the SPH simulations generate central cores with slightly lower entropies and virial shocks at slightly larger radii, consistent with what has been seen in previous studies. The inclusion of radiative cooling, star formation, and stellar feedback leads to much larger differences between the two methods. Most dramatically, at z=5, rapid cooling in the AMR case moves the accretion shock well within the virial radius, while this shock remains near the virial radius in the SPH case, due to excess heating, coupled with poorer capturing of the shock width. On the other hand, the addition of feedback from active galactic nuclei (AGN) to the simulations results in much better ag...

  3. Toward a Unified AGN Structure

    Science.gov (United States)

    Kazanas, Demosthenes; Fukumura, Keigo; Shrader, Chris; Behar, Ehud; Contopoulosa, Ioannis

    2012-01-01

    We present a unified model for the structure and appearance of accretion powered sources across their entire luminosity range from galactic X-ray binaries (XRB) to luminous quasars, with emphasis on AG N and their phenomenology. Central to this model is the notion of MHD winds launched by the accretion disks that power these objects. These winds provide the matter that manifests as blueshifted absorption features in the UV and X-ray spectra of a large fraction of these sources; furthermore, their density distribution in the poloidal plane determines their "appearance" (i.e. the column and velocity structure of these absorption features and the obscuration of the continuum source) as a function of the observer inclination angle (a feature to which INTEGRAL has made significant contributions). This work focuses on just the broadest characteristics of these objects; nonetheless, it provides scaling laws that allow one to reproduce within this model the properties of objects extending in luminosity from luminous quasars to XRBs. Our general conclusion is that the AGN phenomenology can be accounted for in terms of three parameters: The wind maSS flux in units of the Eddington value, m(dot), the observers' inclination angle Theta and the logarithmic slope between the 0/UV and X-ray fluxes alpha(sub ox); however because of a correlation between alpha(sub ox) and UV luminosity the number of significant parameters is two. The AGN correlations implied by this model appear to extend to and consistent with the XRB phenomenology, suggesting the presence of a truly unified underlying structure for accretion powered sources.

  4. KAIT Fermi AGN Light-Curve Reservoir

    Data.gov (United States)

    National Aeronautics and Space Administration — This web page shows the light curves of a total of 163 AGNs that are monitored by KAIT with average cadence of 3 days. These are unfiltered observations; in...

  5. Highlights from the VERITAS AGN Observation Program

    CERN Document Server

    Benbow, Wystan

    2016-01-01

    The VERITAS array of four 12-m imaging atmospheric-Cherenkov telescopes began full-scale operations in 2007, and is one of the world's most sensitive detectors of astrophysical very high energy (VHE; E>100 GeV) gamma rays. Observations of active galactic nuclei (AGN) are a major focus of the VERITAS Collaboration, and more than 60 AGN, primarily blazars, are known to emit VHE photons. Approximately 4000 hours have been devoted to the VERITAS AGN observation program, resulting in 34 detections. Most of these detections are accompanied by contemporaneous, broadband observations, enabling a more detailed study of the underlying jet-powered processes. Recent highlights of the VERITAS AGN observation program are presented.

  6. AGN Absorption Linked to Host Galaxies

    CERN Document Server

    Juneau, Stéphanie

    2013-01-01

    Multiwavelength identification of AGN is crucial not only to obtain a more complete census, but also to learn about the physical state of the nuclear activity (obscuration, efficiency, etc.). A panchromatic strategy plays an especially important role when the host galaxies are star-forming. Selecting far-Infrared galaxies at 0.3AGN tracers in the X-ray, optical spectra, mid-infrared, and radio regimes, we found a twice higher AGN fraction than previous studies, thanks to the combined AGN identification methods and in particular the recent Mass-Excitation (MEx) diagnostic diagram. We furthermore find an intriguing relation between AGN X-ray absorption and the specific star formation rate (sSFR) of the host galaxies, indicating a physical link between X-ray absorption and either the gas fraction or the gas geometry in the hosts. These findings have implications for our current understanding of both the AGN unification model and the nature of the black hole-galaxy connection. These proceedi...

  7. A method for determining AGN accretion phase in field galaxies

    Science.gov (United States)

    Micic, Miroslav; Martinović, Nemanja; Sinha, Manodeep

    2016-09-01

    Recent observations of active galactic nucleus (AGN) activity in massive galaxies (log M*/ M⊙ > 10.4) show the following: (1) at z AGN-hosting galaxies do not show enhanced merger signatures compared with normal galaxies, (2) also at z AGNs are hosted by quiescent galaxies and (3) at z > 1, the percentage of AGNs in star-forming galaxies increases and becomes comparable to the AGN percentage in quiescent galaxies at z ˜ 2. How can major mergers explain AGN activity in massive quiescent galaxies that have no merger features and no star formation to indicate a recent galaxy merger? By matching merger events in a cosmological N-body simulation to the observed AGN incidence probability in the COSMOS survey, we show that major merger-triggered AGN activity is consistent with the observations. By distinguishing between `peak' AGNs (recently merger-triggered and hosted by star-forming galaxies) and `faded' AGNs (merger-triggered a long time ago and now residing in quiescent galaxies), we show that the AGN occupation fraction in star-forming and quiescent galaxies simply follows the evolution of the galaxy merger rate. Since the galaxy merger rate drops dramatically at z AGNs left to be observed are the ones triggered by old mergers that are now in the declining phase of their nuclear activity, hosted by quiescent galaxies. As we go towards higher redshifts, the galaxy merger rate increases and the percentages of `peak' AGNs and `faded' AGNs become comparable.

  8. Modeling optical and UV polarization of AGNs. III. From uniform-density to clumpy regions

    Science.gov (United States)

    Marin, F.; Goosmann, R. W.; Gaskell, C. M.

    2015-05-01

    Context. A growing body of evidence suggests that some, if not all, scattering regions of active galactic nuclei (AGNs) are clumpy. The inner AGN components cannot be spatially resolved with current instruments and must be studied by numerical simulations of observed spectroscopy and polarization data. Aims: We run radiative transfer models in the optical/UV for a variety of AGN reprocessing regions with different distributions of clumpy scattering media. We obtain geometry-sensitive polarization spectra and images to improve our previous AGN models and their comparison with the observations. Methods: We use the latest public version 1.2 of the Monte Carlo code stokes presented in the first two papers of this series to model AGN reprocessing regions of increasing morphological complexity. We replace previously uniform-density media with up to thousands of constant-density clumps. We couple a continuum source to fragmented equatorial scattering regions, polar outflows, and toroidal obscuring dust regions and investigate a wide range of geometries. We also consider different levels of fragmentation in each scattering region to evaluate the importance of fragmentation for the net polarization of the AGN. Results: In comparison with uniform-density models, equatorial distributions of gas and dust clouds result in grayer spectra and show a decrease in the net polarization percentage at all lines of sight. The resulting polarization position angle depends on the morphology of the clumpy structure, with extended tori favoring parallel polarization while compact tori produce orthogonal polarization position angles. In the case of polar scattering regions, fragmentation increases the net polarization unless the cloud filling factor is small. A complete AGN model constructed from the individual, fragmented regions can produce low polarization percentages (<2%), with a parallel polarization angle for observer inclinations up to 70° for a torus half opening angle of 60°. For

  9. Panel A1 : AGN SEDs and AGN vs. star-formation

    NARCIS (Netherlands)

    Barthel, PD; Lutz, D; Pilbratt, GL; Cernicharo, J; Heras, AM; Prusti, T; Harris, RA

    2001-01-01

    Photometry and spectroscopy with FIRST will provide unique opportunities to study the spectral energy distributions of AGN and the relation of AGN and starburst galaxies. This is true both for in-depth characterization of nearby sources and for interpretation of high redshift objects detected by FIR

  10. Early evolution stage of AGN

    Science.gov (United States)

    Kunert-Bajraszewska, M.; Labiano, A.; Siemiginowska, A.; Guainazzi, M.; Gawroński, M.

    2015-03-01

    Radio sources are divided into two distinct morphological groups of objects: Fanaroff-Riley type I and type II sources. There is a relatively sharp luminosity boundary between these at low frequency. The nature of the FR division is still an open issue, as are the details of the evolutionary process in which younger and smaller GHz-peaked spectrum (GPS) and compact steep spectrum (CSS) sources become large-scale radio structures. It is still unclear whether FRII objects evolve to become FRIs, or whether a division has already occurred amongst CSS sources and some of these then become FRIs and some FRIIs. We explored evolution scenarios of AGNs using new radio, optical and X-ray data of unstudied so far Low Luminosity Compact (LLC) sources. We suggest that the determining factors of the further evolution of compact radio objects could occur at subgalactic (or even nuclear) scales, or they could be related to the radio jet - interstellar medium (ISM) interactions and evolution. Our studies show that the evolutionary track could be related to the interaction, strength of the radio source and excitation levels of the ionized gas instead of the radio morphology of the young radio source.

  11. The Spatial Clustering of ROSAT All-Sky Survey AGNs II. Halo Occupation Distribution Modeling of the Cross Correlation Function

    CERN Document Server

    Miyaji, Takamitsu; Coil, Alison L; Aceves, Hector

    2010-01-01

    This is the second paper of a series that reports on our investigation of the clustering properties of AGNs in the ROSAT All-Sky Survey (RASS) through cross-correlation functions (CCFs) with Sloan Digital Sky Survey (SDSS) galaxies. In this paper, we apply the Halo Occupation Distribution (HOD) model to the CCFs between the RASS Broad-line AGNs with SDSS Luminous Red Galaxies (LRGs) in the redshift range 0.16AGNs by a model fit to the CCF. For the first time, we are able to go beyond quoting merely a `typical' AGN host halo mass, M_h, and model the full distribution function of AGN host dark matter halos. In addition, we are able to determine the large-scale bias and the mean M_h more accurately. We explore the behavior of three simple HOD models. Our first model (Model A) is a truncated power-law HOD model in which all AGNs are satellites. With this model, we find an upper lim...

  12. AGN evolution from a galaxy evolution viewpoint

    CERN Document Server

    Caplar, Neven; Trakhtenbrot, Benny

    2014-01-01

    We explore the connections between the evolving galaxy and AGN populations. We present a simple phenomenological model that links the evolving galaxy mass function and the evolving quasar luminosity function, motivated by similarities between the two, which makes specific and testable predictions for the distribution of host galaxy masses for AGN of different luminosities. We show that the phi$^{*}$ normalisations of the galaxy mass function and the AGN luminosity function closely track each other over a wide range of redshifts, implying a constant "duty cycle" of AGN activity. The strong redshift evolution in the AGN break luminosity $L^*$ is produced by either an evolution in the distribution of Eddington rations, or in the $m_{bh}/m_{*}$ mass ratio, or both. An evolving $m_{bh}/m_{*}$ ratio, such that it is ten times higher at $z \\sim 2$ (i.e. roughly following $(1+z)^{2}$), reproduces the observed distribution of SDSS quasars in the ($m_{bh},L$) plane and accounts for the apparent "sub-Eddington boundary"...

  13. Environmental effects on galaxies and AGN

    CERN Document Server

    Padilla, Nelson; Gonzalez, Roberto

    2009-01-01

    We study the properties of SDSS galaxies with and without AGN detection as a function of the local and global environment. For the full SDSS sample, we find indications that the local galaxy density is the most efficient parameter to separate galaxy populations, but we also find that galaxies at fixed local density show some remaining variation of their properties as a function of the distance to the nearest cluster of galaxies (in a range of 0 to 10 cluster virial radii). These differences seem to become less significant if the galaxy samples are additionally constrained to be hosted by groups of similar total luminosity. In AGN host galaxies, the morphology-density relation is much less noticeable when compared to the behaviour of the full SDSS sample, indicating a lack of sensitivity to the host group mass during the AGN phase probably due to the higher typical luminosities of the AGN hosts. In order to interpret this result we analyse control AGN samples with matching distributions of redshifts, r-band lu...

  14. ASTRO-H White Paper - AGN Reflection

    CERN Document Server

    Reynolds, C; Awaki, H; Gallo, L; Gandhi, P; Haba, Y; Kawamuro, T; LaMassa, S; Lohfink, A; Ricci, C; Tazaki, F; Zoghbi, A

    2014-01-01

    X-ray observations provide a powerful tool to probe the central engines of active galactic nuclei (AGN). A hard X-ray continuum is produced from deep within the accretion flow onto the supermassive black hole, and all optically thick structures in the AGN (the dusty torus of AGN unification schemes, broad emission line clouds, and the black hole accretion disk) "light up" in response to irradiation by this continuum. This White Paper describes the prospects for probing AGN physics using observations of these X-ray reflection signatures. High-resolution SXS spectroscopy of the resulting fluorescent iron line in type-2 AGN will give us an unprecedented view of the obscuring torus, allowing us to assess its dynamics (through line broadening) and geometry (through the line profile as well as observations of the "Compton shoulder"). The broad-band view obtained by combining all of the ASTRO-H instruments will fully characterize the shape of the underlying continuum (which may be heavily absorbed) and reflection/sc...

  15. Dust Emission by AGN and Starbursts

    CERN Document Server

    Siebenmorgen, R

    2005-01-01

    Present AGN and starburst models aiming to account for the observed infrared SEDs consider a physical description of the dust and a solution of the radiative transfer problem. MIR spectra obtained at different spatial scales (SST-IRS, ISO and TIMMI2) are presented. They show that PAH bands are detected in starburst regions but significantly reduced near the centre of AGN. This is explained by examining the heating mechanism of PAHs after hard (FUV, X-ray) photon interactions. Economic radiative transfer models of starbursts and AGN are made available. The successful application of the starburst model is demonstrated by fitting broad band data and detailed Spitzer spectra of NGC7714. The AGN model is applied to ISO data of a sample of 68 radio galaxies and quasars of the 3CR catalogue. Radiative transfer models of galaxies with Hidden Broad Line Regions are shown. Their SED enable us to separate the contributions from the dusty disc of the AGN and the starbursts. The composite model is consistent with the unif...

  16. A Powerful AGN Outburst in RBS 797

    CERN Document Server

    Cavagnolo, K W; Wise, M W; Nulsen, P E J; Brüggen, M; Gitti, M; Rafferty, D A

    2011-01-01

    Utilizing $\\sim 50$ ks of Chandra X-ray Observatory imaging, we present an analysis of the intracluster medium (ICM) and cavity system in the galaxy cluster RBS 797. In addition to the two previously known cavities in the cluster core, the new and deeper X-ray image has revealed additional structure associated with the active galactic nucleus (AGN). The surface brightness decrements of the two cavities are unusually large, and are consistent with elongated cavities lying close to our line-of-sight. We estimate a total AGN outburst energy and mean jet power of $\\approx 3 - 6 \\times 10^{60}$ erg and $\\approx 3 - 6 \\times 10^{45}$ erg s$^{-1}$, respectively, depending on the assumed geometrical configuration of the cavities. Thus, RBS 797 is apparently among the the most powerful AGN outbursts known in a cluster. The average mass accretion rate needed to power the AGN by accretion alone is $\\sim 1 M_{\\odot}$ yr$^{-1}$. We show that accretion of cold gas onto the AGN at this level is plausible, but that Bondi acc...

  17. The Horizon-AGN Simulation: Morphological Diversity of Galaxies Promoted by AGN feedback

    CERN Document Server

    Dubois, Yohan; Pichon, Christophe; Devriendt, Julien; Gavazzi, Raphael; Welker, Charlotte; Volonteri, Marta

    2016-01-01

    The interplay between cosmic gas accretion onto galaxies and galaxy mergers drives the observed morphological diversity of galaxies. By comparing the state-of-the-art hydrodynamical cosmological simulations Horizon-AGN and Horizon-noAGN, we unambiguously identify the critical role of Active Galactic Nuclei (AGN) in setting up the correct galaxy morphology for the massive end of the population. With AGN feedback, typical kinematic and morpho-metric properties of galaxy populations as well as the galaxy-halo mass relation are in much better agreement with observations. Only AGN feedback allows massive galaxies at the center of groups and clusters to become ellipticals, while without AGN feedback those galaxies reform discs. It is the merger-enhanced AGN activity that is able to freeze the morphological type of the post-merger remnant by durably quenching its quiescent star formation. Hence morphology is shown not to be purely driven by mass but also by the nature of cosmic accretion: at constant galaxy mass, el...

  18. The Horizon-AGN simulation: morphological diversity of galaxies promoted by AGN feedback

    Science.gov (United States)

    Dubois, Yohan; Peirani, Sébastien; Pichon, Christophe; Devriendt, Julien; Gavazzi, Raphaël; Welker, Charlotte; Volonteri, Marta

    2016-09-01

    The interplay between cosmic gas accretion onto galaxies and galaxy mergers drives the observed morphological diversity of galaxies. By comparing the state-of-the-art hydrodynamical cosmological simulations Horizon-AGN and Horizon-noAGN, we unambiguously identify the critical role of Active Galactic Nuclei (AGN) in setting up the correct galaxy morphology for the massive end of the population. With AGN feedback, typical kinematic and morpho-metric properties of galaxy populations as well as the galaxy-halo mass relation are in much better agreement with observations. Only AGN feedback allows massive galaxies at the center of groups and clusters to become ellipticals, while without AGN feedback those galaxies reform discs. It is the merger-enhanced AGN activity that is able to freeze the morphological type of the post-merger remnant by durably quenching its quiescent star formation. Hence morphology is shown not to be purely driven by mass but also by the nature of cosmic accretion: at constant galaxy mass, ellipticals are galaxies that are mainly assembled through mergers, while discs are preferentially built from the in situ star formation fed by smooth cosmic gas infall.

  19. The radio AGN population dichotomy: Green valley Seyferts versus red sequence low-excitation AGN

    CERN Document Server

    Smolcic, V

    2009-01-01

    Radio outflows of active galactic nuclei (AGN) are invoked in cosmological models as a key feedback mechanism in the latest phases of massive galaxy formation. Recently it has been suggested that the two major radio AGN populations -- the powerful high-excitation, and the weak low-excitation radio AGN (HERAGN and LERAGN, resp.) -- represent two earlier and later stages of massive galaxy build-up. To test this, here we make use of a local (0.04AGN with available optical spectroscopy, drawn from the FIRST, NVSS, SDSS, and 3CRR surveys. A clear dichotomy is found between the properties of low-excitation (absorption line AGN, and LINERs) and high-excitation (Seyferts) radio AGN. The hosts of the first have the highest stellar masses, reddest optical colors, and highest mass black holes but accrete inefficiently (at low rates). On the other hand, the high-excitation radio AGN have lower stellar masses, bluer optical colors (consistent with the `green valley'), and lower mass blac...

  20. The Activity of the Neighbours of AGN and Starburst Galaxies

    CERN Document Server

    Koulouridis, E; Chavushyan, V; Dultzin, D; Krongold, Y; Georgantopoulos, I; Leon-Tavares, J

    2011-01-01

    We present a follow-up study on a series of papers concerning the role of close interactions as a possible triggering mechanism of the activity of AGN and starburst galaxies. We have already studied the close (< 100 kpc/h) and the large scale (< 1 Mpc/h) environment of Sy1, Sy2 and Bright IRAS galaxies (BIRG) and their respective control samples. The results led us to the conclusion that a close encounter appears capable of activating a sequence where a normal galaxy becomes first a starburst, then a Sy2 and finally a Sy1. However since both galaxies of an interacting pair should be affected, we present here optical spectroscopy and X-ray imaging of the neighbouring galaxies around our original Seyfert and BIRG galaxy samples. Based on optical spectroscopy we find that more than 70% of all neighbouring galaxies exhibit thermal or/and nuclear activity (namely enhanced star formation, starbursting and/or AGN), while an additional X-ray analysis showed that this percentage can reach up to 100%. Furthermore...

  1. Unveiling multiple AGN activity in galaxy mergers

    CERN Document Server

    De Rosa, A; Bogdanovic, T; Decarli, R; Heidt, J; Herrero-Illana, R; Husemann, B; Komossa, S; Kun, E; Loiseau, N; Guainazzi, M; Paragi, Z; Perez-Torres, M; Piconcelli, E; Schawinski, K; Vignali, C

    2016-01-01

    In this paper we present an overview of the MAGNA (Multiple AGN Activity) project aiming at a comprehensive study of multiple supemassive black hole systems. With the main goal to characterize the sources in merging systems at different stages of evolution, we selected a sample of objects optically classified as multiple systems on the basis of emission line diagnostics and started a massive multiband observational campaign. Here we report on the discovery of the exceptionally high AGN density compact group SDSS~J0959+1259. A multiband study suggests that strong interactions are taking place among its galaxies through tidal forces, therefore this system represents a case study for physical mechanisms that trigger nuclear activity and star formation. We also present a preliminary analysis of the multiple AGN system SDSS~J1038+3921.}

  2. Reverberation Mapping of AGN Accretion Disks

    Science.gov (United States)

    Fausnaugh, Michael; AGN STORM Collaboration

    2017-01-01

    I will discuss new reverberation mapping results that allow us to investigate the temperature structure of AGN accretion disks. By measuring time-delays between broad-band continuum light curves, we can determine the size of the disk as a function of wavelength. I will discuss the detection of continuum lags in NGC 5548 reported by the AGN STORM project and implications for the accretion disk. I will also present evidence for continuum lags in two other AGN for which we recently measured black hole masses from continuum-Hbeta reverberations. The mass measurements allow us to compare the continuum lags to predictions from standard thin disk theory, and our results indicate that the accretion disks are larger than the simplest expectations.

  3. MEASURING SUPERMASSIVE BLACK HOLE SPINS IN AGN

    Directory of Open Access Journals (Sweden)

    Laura Brenneman

    2013-12-01

    Full Text Available Measuring the spins of supermassive black holes (SMBHs in active galactic nuclei (AGN can inform us about the relative role of gas accretion vs. mergers in recent epochs of the life of the host galaxy and its AGN. Recent theoretical and observation advances have enabled spin measurements for ten SMBHs thus far, but this science is still very much in its infancy. Herein, I discuss how we measure black hole spin in AGN, using recent results from a long Suzaku campaign on NGC 3783 to illustrate this process and its caveats. I then present our current knowledge of the distribution of SMBH spins in the local universe. I also address prospects for improving the accuracy, precision and quantity of these spin constraints in the next decade and beyond with instruments such as NuSTAR, Astro-H and future large-area X-ray telescopes.

  4. AGN jet physics and apparent opening angles

    CERN Document Server

    Clausen-Brown, Eric; Pushkarev, Alexander B; Kovalev, Yuri Y; Lister, Matthew L

    2013-01-01

    We present a new method to measure Gamma*theta_j in flux-limited samples of active galactic nuclei (AGN) jets, where Gamma is the bulk Lorentz factor and theta_j is the jet's half-opening angle. The Gamma*theta_j parameter is physically important for models of jet launching, and also determines the effectiveness of jet instabilities and magnetic reconnection. We measure Gamma*theta_j by analyzing the observed distribution of apparent opening angles in very long baseline interferometry (VLBI) flux-limited samples of jets, given some prior knowledge of the active galactic nuclei (AGN) radio luminosity function. We then apply this method to the MOJAVE flux-limited sample of radio loud objects and find Gamma*theta_j = 0.1 +- 0.03, which implies that AGN jets are subject to a variety of physical processes that require causal connection.

  5. Bolometric Luminosity Correction of H2O Maser AGNs

    Indian Academy of Sciences (India)

    Q. Guo; J. S. Zhang; J. Wang

    2014-09-01

    For the H2O maser host AGN sample, we derived their bolometric luminosity corrections, based on their X-ray data and [O III] emission line luminosities. Our results for maser AGNs is comparable to that of non-maser AGNs.

  6. AGN Host Galaxy Properties and Mass Function

    OpenAIRE

    Bongiorno, Angela

    2016-01-01

    Supermassive black hole growth, nuclear activity, and galaxy evolution have been found to be closely related. In the context of AGN-galaxy coevolution, I will discuss about the relation found between the host galaxy properties and the central BH and I will present the latest determination of the host galaxy stellar mass function (HGMF), and the specific accretion rate distribution function (SARDF), derived from the XMM-COSMOS sample up to z∼2.5, with particular focus on AGN feedback as possib...

  7. AGN Host Galaxy Properties And Mass Function

    Science.gov (United States)

    Bongiorno, Angela

    2016-10-01

    Supermassive black hole growth, nuclear activity, and galaxy evolution have been found to be closely related. In the context of AGN-galaxy coevolution, I will discuss about the relation found between the host galaxy properties and the central BH and I will present the latest determination of the host galaxy stellar mass function (HGMF), and the specific accretion rate distribution function (SARDF), derived from the XMM-COSMOS sample up to z˜2.5, with particular focus on AGN feedback as possible responsible mechanism for galaxy quenching.

  8. The Activity of the Neighbours of AGN and Starburst Galaxies: Towards an evolutionary sequence of AGN activity

    CERN Document Server

    Koulouridis, E; Chavushyan, V; Dultzin, D; Krongold, Y; Georgantopoulos, I; Goudis, C

    2009-01-01

    We present a follow-up study of a series of papers concerning the role of close interactions as a possible triggering mechanism of the activity of AGN and starburst (SB) galaxies. We have already studied the close (<100 kpc) and the large scale (<1 Mpc) environment of Sy1, Sy2 and Bright IRAS galaxies and their respective control samples (Koulouridis et al.). The results led us to the conclusion that a close encounter appears capable of activating a sequence where a normal galaxy becomes first a starburst, then a Sy2 and finally a Sy1 galaxy. However since both galaxies of an interacting pair should be affected, we present here optical spectroscopy and X-ray imaging of the neighbouring galaxies around our Seyfert and BIRG galaxy samples. We find that more than 70% of all neighbouring galaxies exhibit thermal or/and nuclear activity (namely enhanced star formation, starbursting and/or AGN) and furthermore we discovered various trends regarding the type and strength of the neighbour's activity with respec...

  9. Morphologies of z~0.7 AGN Host Galaxies in CANDELS: No trend of merger incidence with AGN luminosity

    CERN Document Server

    Villforth, C; Rosario, D J; Santini, P; McGrath, E J; van der Wel, A; Chang, Y -Y; Guo, Yicheng; Dahlen, T; Bell, E F; Conselice, C J; Croton, D; Dekel, A; Faber, S M; Grogin, N; Hamilton, T; Hopkins, P F; Juneau, S; Kartaltepe, J; Kocevski, D; Koekemoer, A; Koo, D C; Lotz, J; McIntosh, D; Mozena, M; Somerville, R; Wild, V

    2014-01-01

    The processes that trigger Active Galactic Nuclei (AGN) remain poorly understood. While lower luminosity AGN may be triggered by minor disturbances to the host galaxy, stronger disturbances are likely required to trigger luminous AGN. Major wet mergers of galaxies are ideal environments for AGN triggering since they provide large gas supplies and galaxy scale torques. There is however little observational evidence for a strong connection between AGN and major mergers. We analyse the morphological properties of AGN host galaxies as a function of AGN and host galaxy luminosity and compare them to a carefully matched sample of control galaxies. AGN are X-ray selected in the redshift range 0.5 < z < 0.8 and have luminosities 41 < log(L_X [erg/s]) < 44.5. 'Fake AGN' are simulated in the control galaxies by adding point sources with the magnitude of the matched AGN. We find that AGN host and control galaxies have comparable assymetries, Sersic indices and ellipticities at restframe ~950nm. AGN host gala...

  10. Testing AGN feedback models in galaxy evolution

    Science.gov (United States)

    Shin, Min-Su

    Galaxy formation and evolution have been one of the most challenging problems in astrophysics. A single galaxy has various components (stars, atomic and molecular gas, a supermassive black hole, and dark matter) and has interacted with its cosmic environment throughout its history. A key issue in understanding galaxy evolution is to find the dominant physical processes in the interactions between the components of a galaxy and between a galaxy and its environment. AGN feedback has been proposed as a key process to suppress late star formation in massive elliptical galaxies and as a general consequence of galaxy mergers and interactions. In this thesis, I investigate feedback effects from active galactic nuclei (AGN) using a new simulation code and data from the Sloan Digital Sky Survey. In the first chapter, I test purely mechanical AGN feedback models via a nuclear wind around the central SMBH in elliptical galaxies by comparing simulation results to four well-defined observational constraints: the mass ratio between the SMBH and its host galaxy, the lifetime of the quasar phase, the X-ray luminosity from the hot interstellar medium, and the mass fraction of young stars. Even though purely mechanical AGN feedback is commonly assumed in cosmological simulations, I find that it is inadequate, and cannot reproduce all four observational constraints simultaneously. This result suggests that both mechanical and radiative feedback modes are important physical processes. In the second chapter, I simulate the coevolution of the SMBH and its host galaxy under different environments, represented by different amounts of gas stripping. Though the connection between environment and galaxy evolution has been well-studied, environmental effects on the growth of the SMBH have not been answered yet. I find that strong gas stripping, which satellite galaxies might experience, highly suppresses SMBH mass accretion and AGN activity. Moreover, the suppression of the SMBH growth is

  11. Parameter matching of series reactor in reactive compensation capacitor bank%无功补偿电容器组串联电抗器的参数匹配

    Institute of Scientific and Technical Information of China (English)

    刘书铭; 李琼林; 杜习周; 余晓鹏; 张晓东

    2012-01-01

    Series reactor is the important part of the reactive power compensation capacitor,the series reactance rate improperly selected may cause the resonance between the capacitor and the system, affecting the safety of equipment and the system stability. The power capacitor switching operation and field test in a substation indicate the mismatching of reactor parameters leads directly to the capacitor fuse explosion. If the current limiting reactor is equipped,not only the appropriate series reactance rate should be selected, but also the equivalent series reactance rate of capacitor bank considered. The corresponding solutions are given according to site situations and the harmonics of shunt compensating branch are analyzed for different series reactance rates of capacitor bank.%串联电抗器是无功补偿电容器中重要的组成部分,串抗率选择不当,可能会使电容器组与系统发生谐振,影响设备的安全和系统的稳定.通过对某一变电站进行电力电容器投切试验和现场测试,得出无功补偿电容器组串联电抗器的参数不匹配是引起该案例中电容器熔丝群爆的直接原因.提出在有限流电抗器的情况下,电容器的设计除了选择合适的串抗率外,还应考虑电容器组等效串抗率,并结合现场实际情况,给出了相应的解决措施.同时分析了电容器组在不同串抗率的情况下,并联补偿支路各次谐波的情况.

  12. H Reactor

    Data.gov (United States)

    Federal Laboratory Consortium — The H Reactor was the first reactor to be built at Hanford after World War II.It became operational in October of 1949, and represented the fourth nuclear reactor on...

  13. The HORIZON-AGN simulation: morphological diversity of galaxies promoted by AGN feedback

    Science.gov (United States)

    Dubois, Yohan; Peirani, Sébastien; Pichon, Christophe; Devriendt, Julien; Gavazzi, Raphaël; Welker, Charlotte; Volonteri, Marta

    2016-12-01

    The interplay between cosmic gas accretion on to galaxies and galaxy mergers drives the observed morphological diversity of galaxies. By comparing the state-of-the-art hydrodynamical cosmological simulations HORIZON-AGN and HORIZON-NOAGN, we unambiguously identify the critical role of active galactic nuclei (AGN) in setting up the correct galaxy morphology for the massive end of the population. With AGN feedback, typical kinematic and morpho-metric properties of galaxy populations as well as the galaxy-halo mass relation are in much better agreement with observations. Only AGN feedback allows massive galaxies at the centre of groups and clusters to become ellipticals, while without AGN feedback those galaxies reform discs. It is the merger-enhanced AGN activity that is able to freeze the morphological type of the post-merger remnant by durably quenching its quiescent star formation. Hence morphology is shown to be driven not only by mass but also by the nature of cosmic accretion: at constant galaxy mass, ellipticals are galaxies that are mainly assembled through mergers, while discs are preferentially built from the in situ star formation fed by smooth cosmic gas infall.

  14. Helical Magnetic Fields in AGN Jets

    Indian Academy of Sciences (India)

    Y. J. Chen; G.-Y. Zhao; Z.-Q. Shen

    2014-09-01

    We establish a simple model to describe the helical magnetic fields in AGN jets projected on the sky plane and the line-of-sight. This kind of profile has been detected in the polarimetric VLBI observation of many blazar objects, suggesting the existence of helical magnetic fields in these sources.

  15. AGN variability at hard X-rays

    CERN Document Server

    Soldi, S; Beckmann, V; Lubinski, P

    2010-01-01

    We present preliminary results on the variability properties of AGN above 20 keV in order to show the potential of the INTEGRAL IBIS/ISGRI and Swift/BAT instruments for hard X-ray timing analysis of AGN. The 15-50 keV light curves of 36 AGN observed by BAT during 5 years show significantly larger variations when the blazar population is considered (average normalized excess variance = 0.25) with respect to the Seyfert one (average normalized excess variance = 0.09). The hard X-ray luminosity is found to be anti-correlated to the variability amplitude in Seyfert galaxies and correlated to the black hole mass, confirming previous findings obtained with different AGN hard X-ray samples. We also present results on the Seyfert 1 galaxy IC 4329A, as an example of spectral variability study with INTEGRAL/ISGRI data. The position of the high-energy cut-off of this source is found to have varied during the INTEGRAL observations, pointing to a change of temperature of the Comptonising medium. For several bright Seyfert...

  16. Hard X-ray Variability of AGN

    CERN Document Server

    Beckmann, V; Courvoisier, T J -L; Gehrels, N; Soldi, S; Tüller, J; Wendt, G

    2007-01-01

    Aims: Active Galactic Nuclei are known to be variable throughout the electromagnetic spectrum. An energy domain poorly studied in this respect is the hard X-ray range above 20 keV. Methods: The first 9 months of the Swift/BAT all-sky survey are used to study the 14 - 195 keV variability of the 44 brightest AGN. The sources have been selected due to their detection significance of >10 sigma. We tested the variability using a maximum likelihood estimator and by analysing the structure function. Results: Probing different time scales, it appears that the absorbed AGN are more variable than the unabsorbed ones. The same applies for the comparison of Seyfert 2 and Seyfert 1 objects. As expected the blazars show stronger variability. 15% of the non-blazar AGN show variability of >20% compared to the average flux on time scales of 20 days, and 30% show at least 10% flux variation. All the non-blazar AGN which show strong variability are low-luminosity objects with L(14-195 keV) < 1E44 erg/sec. Conclusions: Concer...

  17. AGN Heating Through Cavities and Shocks

    NARCIS (Netherlands)

    P.E.J. Nulsen; C. Jones; W.R. Forman; L.P. David; B.R. McNamara; D.A. Rafferty; L. Bîrzan; M. Wise

    2007-01-01

    Three comments are made on AGN heating of cooling flows. A simple physical argument is used to show that the enthalpy of a buoyant radio lobe is converted to heat in its wake. Thus, a significant part of ``cavity'' enthalpy is likely to end up as heat. Second, the properties of the repeated weak sho

  18. A Global Picture of AGN Winds

    Science.gov (United States)

    Kazanas, D.; Fukumura, K.

    2011-01-01

    We present a unified structure for accretion powered sources across their entire luminosity range from accreting galactic black holes to the most luminous quasars, with emphasis on AGN and their phenomenology. Central to this end is the notion of MHD winds launched from the accretion disks that power these objects. This work similar in spirit to that of Elvis of more that a decade ago, provides, on one hand, only the broadest characteristics of these objects, but on the other, also scaling laws that allow one to make contact with objects of different luminosity. The conclusion of this work is that AGN phenomenology can be accounted for in terms of dot(m), the wind mass flux in units of the Eddington value, the observer's inclination angle theta and alpha_OX the logarithmic slope between UV and X-ray flares. However given the well known correlation between alpha(sub ox) and UV Luminosity, we conclude that the AGN structure depends on only two parameters. The small number of model parameters hence suggests that an understanding of the global AGN properties maybe within reach.

  19. What are the galaxies that host MIR-selected AGN?

    Science.gov (United States)

    Rosario, David

    2016-08-01

    Infra-red selection techniques, sensitive to dust strongly heated by an AGN, offer a way to identify some of the most obscured accretion events in the Universe. I will describe the results of a comprehensive multi-wavelength study of AGN to z>2 selected using Spitzer/IRAC based methods in the COSMOS field. Armed with AGN-optimised redshifts and stellar masses, we explore the dust emission from the active nucleus and the host galaxy. We demonstrate that IR-selected AGN tend to be found in low mass host galaxies, when compared to other AGN identification methods. The star-formation rates of obscured and unobscured IR-selected AGN are very similar, implying that large-scale obscuration with co-eval star-bursts are not found in a major proportion of heavily obscured AGN.

  20. Decreased specific star formation rates in AGN host galaxies

    Science.gov (United States)

    Shimizu, T. Taro; Mushotzky, Richard F.; Meléndez, Marcio; Koss, Michael; Rosario, David J.

    2015-09-01

    We investigate the location of an ultra-hard X-ray selected sample of active galactic nuclei (AGN) from the Swift Burst Alert Telescope (BAT) catalogue with respect to the main sequence (MS) of star-forming galaxies using Herschel-based measurements of the star formation rate (SFR) and M*'s from Sloan Digital Sky Survey photometry where the AGN contribution has been carefully removed. We construct the MS with galaxies from the Herschel Reference Survey and Herschel Stripe 82 Survey using the exact same methods to measure the SFR and M* as the Swift/BAT AGN. We find that a large fraction of the Swift/BAT AGN lie below the MS indicating decreased specific SFR (sSFR) compared to non-AGN galaxies. The Swift/BAT AGN are then compared to a high-mass galaxy sample (CO Legacy Database for GALEX Arecibo SDSS Survey, COLD GASS), where we find a similarity between the AGN in COLD GASS and the Swift/BAT AGN. Both samples of AGN lie firmly between star-forming galaxies on the MS and quiescent galaxies far below the MS. However, we find no relationship between the X-ray luminosity and distance from the MS. While the morphological distribution of the BAT AGN is more similar to star-forming galaxies, the sSFR of each morphology is more similar to the COLD GASS AGN. The merger fraction in the BAT AGN is much higher than the COLD GASS AGN and star-forming galaxies and is related to distance from the MS. These results support a model in which bright AGN tend to be in high-mass star-forming galaxies in the process of quenching which eventually starves the supermassive black hole itself.

  1. AGN Variability: Probing Black Hole Accretion

    Science.gov (United States)

    Moreno, Jackeline; O'Brien, Jack; Vogeley, Michael S.; Richards, Gordon T.; Kasliwal, Vishal P.

    2017-01-01

    We combine the long temporal baseline of Sloan Digital Sky Survey (SDSS) for quasars in Stripe 82 with the high precision photometry of the Kepler/K2 Satellite to study the physics of optical variability in the accretion disk and supermassive black hole engine. We model the lightcurves directly as Continuous-time Auto Regressive Moving Average processes (C-ARMA) with the Kali analysis package (Kasliwal et al. 2016). These models are extremely robust to irregular sampling and can capture aperiodic variability structure on various timescales. We also estimate the power spectral density and structure function of both the model family and the data. A Green's function kernel may also be estimated for the resulting C-ARMA parameter fit, which may be interpreted as the response to driving impulses such as hotspots in the accretion disk. We also examine available spectra for our AGN sample to relate observed and modelled behavior to spectral properties. The objective of this work is twofold: to explore the proper physical interpretation of different families of C-ARMA models applied to AGN optical flux variability and to relate empirical characteristic timescales of our AGN sample to physical theory or to properties estimated from spectra or simulations like the disk viscosity and temperature. We find that AGN with strong variability features on timescales resolved by K2 are well modelled by a low order C-ARMA family while K2 lightcurves with weak amplitude variability are dominated by outliers and measurement errors which force higher order model fits. This work explores a novel approach to combining SDSS and K2 data sets and presents recovered characteristic timescales of AGN variability.

  2. Density profile of dark matter haloes and galaxies in the Horizon-AGN simulation: the impact of AGN feedback

    CERN Document Server

    Peirani, S; Volonteri, M; Devriendt, J; Bundy, K; Silk, J; Pichon, C; Kaviraj, S; Gavazzi, R; Habouzit, M

    2016-01-01

    Using a suite of three large cosmological hydrodynamical simulations, Horizon-AGN, Horizon-noAGN (no AGN feedback) and Horizon-DM (no baryons), we investigate how a typical sub-grid model for AGN feedback affects the evolution of the inner density profiles of massive dark matter haloes and galaxies. Based on direct object-to-object comparisons, we find that the integrated inner mass and density slope differences between objects formed in these three simulations (hereafter, H_AGN, H_noAGN and H_DM) significantly evolve with time. More specifically, at high redshift (z~5), the mean central density profiles of H_AGN and H_noAGN dark matter haloes tend to be much steeper than their H_DM counterparts owing to the rapidly growing baryonic component and ensuing adiabatic contraction. By z~1.5, these mean halo density profiles in H_AGN have flattened, pummelled by powerful AGN activity ("quasar mode"): the integrated inner mass difference gaps with H_noAGN haloes have widened, and those with H_DM haloes have narrowed...

  3. Equivalence of conversion rate of the plug flow reactor and the multiple mixed flow feactors in series for the second-order irreversible reaction%多级串联等体积全混流反应器与平推流反应器的等效性研究——以二级不可逆反应为例

    Institute of Scientific and Technical Information of China (English)

    练以诚; 赵葛新; 秦玉建; 杨索和; 罗国华; 靳海坡

    2011-01-01

    在多级串联全混流反应器中针对二级不可逆反应,推导出第N级串级反应器的出口浓度表达式.为与平推流反应器进行比较,引人反应器的相对效率,在平推流反应器中一定的转化率条件下,考察反应速率常数和反应物初始摩尔比大于1的情况下对串联级数的影响.通过实例计算,得出随着相对效率的增大,串联反应器级数随之增大.而当串联级数达到5时,相对效率达到94%以上.此外,随着反应速率常数和反应物初始浓度比的增大,串联全混流反应器级数在相对效率固定的情况下都会达到有限的级数,即在5个串级以内就可以达到较高的相对效率.%The formula of output concentration of reactant of the N-th reactor is made of N nesting squarts.Approximate expression has been presented on research in replace of the plug flow reactor by the multiple mixed flow reactors in series. The relative sufficiency is introduced to study the relationship between plug flow reactor and the multiple mixed flow reactors in series. The effect of the reaction rate constant and the reactants initial concentration ratio on the series were number discussed by compared with the plug flow reactor and the multiple mixed flow reactors in series. The results show that the series numbers increased with the increase of relative efficiencyt.When the series is 5, the relative efficiency is over 94%. Besides, as the reaction rate constant and the ratio of initial concentration of reactants improved, the series of multiple mixed flow reactors will be a constant. Generally ,the relative efficiency is high when the series within 5 reactors.

  4. Compact radio cores in radio-quiet AGNs

    CERN Document Server

    Maini, Alessandro; Norris, Ray P; Giovannini, Gabriele; Spitler, Lee R

    2016-01-01

    The mechanism of radio emission in radio-quiet (RQ) active galactic nuclei (AGN) is still debated and might arise from the central AGN, from star formation activity in the host, or from either of these sources. A direct detection of compact and bright radio cores embedded in sources that are classified as RQ can unambiguously determine whether a central AGN significantly contributes to the radio emission. We search for compact, high-surface-brightness radio cores in RQ AGNs that are caused unambiguously by AGN activity. We used the Australian Long Baseline Array to search for compact radio cores in four RQ AGNs located in the Extended Chandra Deep Field South (ECDFS). We also targeted four radio-loud (RL) AGNs as a control sample. We detected compact and bright radio cores in two AGNs that are classified as RQ and in one that is classified as RL. Two RL AGNs were not imaged because the quality of the observations was too poor. We report on a first direct evidence of radio cores in RQ AGNs at cosmological reds...

  5. Method for Determining AGN Accretion Phase in Field Galaxies

    CERN Document Server

    Micic, Miroslav; Sinha, Manodeep

    2016-01-01

    Recent observations of AGN activity in massive galaxies (log Mstar / Msun > 10.4) show that: 1) at z 1, percentage of AGNs in star forming galaxies increases and becomes comparable to AGN percentage in quiescent galaxies at z ~ 2. How can major mergers explain AGN activity in massive quiescent galaxies which have no merger features and no star formation to indicate recent galaxy merger? By matching merger events in a cosmological N-body simulation to the observed AGN incidence probability in the COSMOS survey, we show that major merger triggered AGN activity is consistent with the observations. By distinguishing between "peak" AGNs (recently merger triggered and hosted by star forming galaxies) and "faded" AGNs (merger triggered a long time ago and now residing in quiescent galaxies), we show that the AGN occupation fraction in star forming and quiescent galaxies simply follows the evolution of the galaxy merger rate. Since the galaxy merger rate drops dramatically at z < 1, the only AGNs left to be obser...

  6. Host galaxies of double-peaked [OIII] emitting AGN: binary AGN or mergers?

    CERN Document Server

    Villforth, Carolin

    2013-01-01

    Mergers are suspected to be reliable triggers of both starformation and AGN activity. However, the exact timing of this process remains poorly understood. Here, we present deep imaging and long slit spectroscopy data of a sample of four double-peaked [OIII] emitting AGN. These sources are often believed to host binary AGN, or at least be currently undergoing major mergers. The sample presented here either have previous IFU and high resolution imaging data that show double-nuclei in the IR as well as kinematicly and spatially distinct line emitting regions. Two sources have detections of double point sources in either the X-ray or radio. The sources studied are therefore likely binary AGN. The AGN in this sample are luminous, radio-quiet and at low redshift. The $u/r/z$ imaging data show host galaxies in a wide range of merger stages, with the majority (3/4) showing tidal tails or complex kinematics and morphologies clearly indicating a recent merger. One source however -hosting a double X-ray source- shows qu...

  7. The SWIFT AGN and Cluster Survey I: Number Counts of AGN and Galaxy Clusters

    CERN Document Server

    Dai, Xinyu; Kochanek, Christopher S; Nugent, Jenna M; Bregman, Joel N

    2015-01-01

    The Swift AGN and Cluster Survey (SACS) uses 125 deg^2 of Swift XRT serendipitous fields with variable depths surrounding gamma-ray bursts to provide a medium depth (4e-15 erg/s/cm^2) and area survey filling the gap between deep, narrow Chandra/XMM-Newton surveys and wide, shallow ROSAT surveys. Here we present a catalog of 22,563 point sources and 442 extended sources and examine the number counts of the AGN and galaxy cluster populations. SACS provides excellent constraints on the AGN number counts at the bright end with negligible uncertainties due to cosmic variance, and these constraints are consistent with previous measurements. We use Wise mid-infrared (MIR) colors to classify the sources. For AGN we can roughly separate the point sources into MIR-red and MIR-blue AGN, finding roughly equal numbers of each type in the soft X-ray band (0.5-2 keV), but fewer MIR-blue sources in the hard X-ray band (2-8 keV). The cluster number counts, with 5% uncertainties from cosmic variance, are also consistent with p...

  8. Extremely efficient Zevatron in rotating AGN magnetospheres

    CERN Document Server

    Osmanov, Zaza; Machabeli, George; Chkheidze, Nino

    2014-01-01

    A novel model of particle acceleration in the magnetospheres of rotating Active Galactic Nuclei (AGN) is constructed.The particle energies may be boosted up to 10^{21}eV in a two step mechanism: In the first stage, the Langmuir waves are centrifugally excited and amplified by means of a parametric process that efficiently pumps rotational energy to excite electrostatic fields. In the second stage, the electrostatic energy is transferred to particle kinetic energy via Landau damping made possible by rapid "Langmuir collapse". The time scale for parametric pumping of Langmuir waves turns out to be small compared to the kinematic timescale, indicating high efficiency of the first process. The second process of "Langmuir collapse" - the creation of caverns or low density regions - also happens rapidly for the characteristic parameters of the AGN magnetosphere. The Langmuir collapse creates appropriate conditions for transferring electric energy to boost up already high particle energies to much higher values. It ...

  9. On the warm absorber in AGN outflow

    CERN Document Server

    Adhikari, T P; Sobolewska, M; Czerny, B

    2016-01-01

    Warm absorber (WA) is an ionised gas present in the line of sight to the AGN central engine. The effect of the absorber is imprinted in the absorption lines observed in X-ray spectra of AGN. In this work, we model the WA in Seyfert 1 galaxy Mrk 509 using its recently published shape of broad band spectral energy distribution (SED) as a continuum illuminating the absorber. Using the photoionization code {\\sc Titan}, recently we have shown that the absorption measure distribution (AMD) found for this object can be successfully modelled as a single slab of gas in total pressure (radiation+gas) equilibrium, contrary to the usual models of constant density multiple slabs. We discuss the transmitted spectrum that would be recorded by an observer after the radiation from the nucleus passes through the WA.

  10. AGN Population in Compact Groups Galaxies

    Directory of Open Access Journals (Sweden)

    M. A. Martínez

    2008-01-01

    Full Text Available El propósito de este trabajo es establecer la frecuencia de actividad nuclear (ya sea por formación estelar ó por actividad tipo AGN en las galaxias pertenecientes a los Grupos Compactos de Hickson (CGs, y caracterizar el tipo de actividad como función de las propiedades de la galaxia huésped y del grupo que las contiene. Con este propósito, hemos seleccionado una muestra estadísticamente significativa de 65 grupos compactos del catálogo de Hickson y obtenido espectroscopía de resolución intermedia para 200 galaxias de la muestra, y tenemos datos completamente reducidos y analizados de 167 galaxias. Añadiendo a la muestra 71 galaxias observadas por Coziol et al. (1998, 2000, 2004 obtenemos una muestra de 238 galaxias. De éstas, 153 (64% muestran emisiones y 76% posiblemente albergan un AGN.

  11. Reactor Physics

    Energy Technology Data Exchange (ETDEWEB)

    Ait Abderrahim, A

    2001-04-01

    The Reactor Physics and MYRRHA Department of SCK-CEN offers expertise in various areas of reactor physics, in particular in neutronics calculations, reactor dosimetry, reactor operation, reactor safety and control and non-destructive analysis of reactor fuel. This expertise is applied in the Department's own research projects in the VENUS critical facility, in the BR1 reactor and in the MYRRHA project (this project aims at designing a prototype Accelerator Driven System). Available expertise is also used in programmes external to the Department such as the reactor pressure steel vessel programme, the BR2 reactor dosimetry, and the preparation and interpretation of irradiation experiments by means of neutron and gamma calculations. The activities of the Fuzzy Logic and Intelligent Technologies in Nuclear Science programme cover several domains outside the department. Progress and achievements in these topical areas in 2000 are summarised.

  12. X-Rays and Infrared Selected AGN

    Science.gov (United States)

    Kirhakos, S. D.; Steiner, J. E.

    1990-11-01

    RESUMEN. En la busqueda de nucleos activos galacticos (NAG) oscurecidos, seleccionamos una tnuestra de galaxias ernisoras de rayos S infrarrojos, Ia mayoria de las cuales son vistas de perf ii. La 6ptica de la regi6n nuclear de las galaxias seleccionadas revelan que el 76% de ellas muestran lineas de emisi5n La clasificaci6n de los es- pectros de acuerdo a los anchos y a la intensidad de cocientes de lineas muestran que existen 34 NAG, 34 objetos de tipo de transici6n y 34 galaxias de la regi6n con nucleos de tipo regi6n H II. Entre los NAG, 3 son del tipo Seyfert I y las otras son del tipo 2. Sugerimos que los objetos identificados como NAG de llneas angostas son objetos tipo Seyfert I oscurecidos ABSTRACT. Looking for obscured active galactic nuclei (AGN), we selected a sample of infrarediX-rays emitting galaxies, mos"t of which are seen as edge-on. Optical spectroscopy of the nuclear region of the selected galaxies revealed that 76 % of them show emission l 'nes. Classification of the spectra according to the widths and line intensity ratios shows that there are 34 AGN, 34 transition type objects and 43 nuclear HIl-like region galaxies. Among the AGN, three are Seyfert type 1 and the others are type 2 objects. We suggest that the objects identified as narrow line AGN are obscured Seyfert 1. o'L : GALAXIES-ACTIVE - X-RAY S-GENERAL

  13. Fast cold gas in hot AGN outflows

    CERN Document Server

    Costa, Tiago; Haehnelt, Martin

    2014-01-01

    Observations of the emission from spatially extended cold gas around bright high-redshift QSOs reveal surprisingly large velocity widths exceeding 2000 km s^(-1), out to projected distances as large as 30 kpc. The high velocity widths have been interpreted as the signature of powerful AGN-driven outflows. Naively, these findings appear in tension with hydrodynamic models in which AGN-driven outflows are energy-driven and thus very hot with typical temperatures T = 10^6-7 K. Using the moving-mesh code Arepo, we perform 'zoom-in' cosmological simulations of a z = 6 QSO and its environment, following black hole growth and feedback via energy-driven outflows. In the simulations, the QSO host galaxy is surrounded by a clumpy circum-galactic medium pre-enriched with metals due to supernovae-driven galactic outflows. As a result, part of the AGN-driven hot outflowing gas can cool radiatively, leading to large amounts (> 10^9 M_sun) of cold gas comoving with the hot bipolar outflow. This results in velocity widths of...

  14. Eigenvector 1: Towards AGN Spectroscopic Unification

    Directory of Open Access Journals (Sweden)

    Jack W. Sulentic

    2007-01-01

    Full Text Available Presentamos una introducción al espacio de parámetros conocido como \\Eigenvector 1", en el que se busca encontrar una unificación, a partir de propiedades espectrales, de los diversos tipos de AGN con líneas anchas de emisión. Este es un parámetro 4D que utiliza mediciones en el óptico, UV y rayos{X para distinguir entre diferentes clases de AGN. Las diferencias en la ocupación del espacio de parámetros sugieren que las fuentes de radio{fuertes son fundamentalmente diferentes a la mayoría de las fuentes radio{calladas. Esto se deriva de nuestra sugerencia de que pueden existir dos poblaciones distintas de AGN con líneas anchas de emisión. Sugerimos que la exploración del espacio de parámetros \\Eigenvector 1" a altos corrimientos al rojo y fuentes luminosas podría ser un programa valioso para los nuevos telescopios propuestos en San Pedro Mártir

  15. LOW LUMINOSITY AGN CANDIDATES IN SDSS

    Directory of Open Access Journals (Sweden)

    J. P. Torres-Papaqui

    2011-01-01

    Full Text Available En una muestra de 476931 galaxias con l neas de emisi n agostas del Sloan Digital Sky Survey Data Release 5, identificamos y estudiamos galaxias de las cuales algunas importantes l neas de emisi n usadas para determinar la naturaleza de su actividad ([OIII]h5007 A, H , o ambas no est an presentes. Este fen meno afecta al 22% de las galaxias con l neas de emisi n y no esta relacionado con una baja raz n de se al a ruido. En el diagrama comparando el ancho equivalente EW([NII]h6584 con la raz n de l nea [NII]h6584/H , la mayor a de estas galaxias se clasifica como AGN. El FWHM de la l nea H es del orden de 400 km s-1 y la luminosidad mediana es 5.6 1039 erg s-1, lo cual justifica la clasificaci n de estas galaxias como AGN de baja luminosidad. Un estudio en sus historias de formaci n estelar usando starlight revela que no existe formaci n estelar en el ltimo Giga a o. Las galaxias anfitrionas de las LLAGNs son de tipo morfol gico temprano con bulbos m s masivos que los de AGN luminosas.

  16. Effects of AGN feedback on LCDM galaxies

    CERN Document Server

    Lagos, Claudia del P; Padilla, Nelson D

    2008-01-01

    We study the effects of Active Galactic Nuclei (AGN) feedback on the formation and evolution of galaxies in a semi-analytic model of galaxy formation. This model is an improved version of the one described by Cora (2006), which now considers the growth of black holes (BHs) as driven by (i) gas accretion during merger-driven starbursts and mergers with other BHs, (ii) accretion during starbursts triggered by disc instabilities, and (iii) accretion of gas cooled from quasi-hydrostatic hot gas haloes. It is assumed that feedback from AGN operates in the later case. The model has been calibrated in order to reproduce observational correlations between BH mass and mass, velocity dispersion, and absolute magnitudes of the galaxy bulge. AGN feedback has a strong impact on reducing or even suppressing gas cooling, an effect that becomes important at lower redshifts. This phenomenon helps to reproduce the observed galaxy luminosity function (LF) in the optical and near IR bands at z=0, and the cosmic star formation ra...

  17. AGN Black Hole Masses from Reverberation Mapping

    Science.gov (United States)

    Peterson, B. M.

    2004-01-01

    Emission-line variability data on bright AGNs indicates that the central objects in these sources have masses in the million to few-hundred million solar mass range. The time-delayed response of the emission lines to continuum variations can be used to infer the size of the line-emitting region via light travel-time arguments. By combining these sizes with the Doppler widths of the variable part of the emission lines, a virial mass estimate can be obtained. For three especially well-studied sources, NGC 5548, NGC 7469, and 3C 390.3, data on multiple emission lines can be used to test the virial hypothesis. In each of these cases, the response time of the various emission lines is anticorrelated with the line width, with the dependence as expected for gravitationally bound motion of the line-emitting clouds, i.e., that the square of the Doppler line width is inversely proportional to the emission-line time delay. Virial masses based on the Balmer lines have now been measured for about three dozen AGNs. Systematic effects currently limit the accuracy of these masses to a factor of several, but characteristics of the radius-luminosity and mass-luminosity relationships for AGNs are beginning to emerge.

  18. Reactor safeguards

    CERN Document Server

    Russell, Charles R

    1962-01-01

    Reactor Safeguards provides information for all who are interested in the subject of reactor safeguards. Much of the material is descriptive although some sections are written for the engineer or physicist directly concerned with hazards analysis or site selection problems. The book opens with an introductory chapter on radiation hazards, the construction of nuclear reactors, safety issues, and the operation of nuclear reactors. This is followed by separate chapters that discuss radioactive materials, reactor kinetics, control and safety systems, containment, safety features for water reactor

  19. Reactor operation

    CERN Document Server

    Shaw, J

    2013-01-01

    Reactor Operation covers the theoretical aspects and design information of nuclear reactors. This book is composed of nine chapters that also consider their control, calibration, and experimentation.The opening chapters present the general problems of reactor operation and the principles of reactor control and operation. The succeeding chapters deal with the instrumentation, start-up, pre-commissioning, and physical experiments of nuclear reactors. The remaining chapters are devoted to the control rod calibrations and temperature coefficient measurements in the reactor. These chapters also exp

  20. Ultra-fast outflows (aka UFOs) from AGNs and QSOs

    Science.gov (United States)

    Cappi, M.; Tombesi, F.; Giustini, M.

    During the last decade, strong observational evidence has been accumulated for the existence of massive, high velocity winds/outflows (aka Ultra Fast Outflows, UFOs) in nearby AGNs and in more distant quasars. Here we briefly review some of the most recent developments in this field and discuss the relevance of UFOs for both understanding the physics of accretion disk winds in AGNs, and for quantifying the global amount of AGN feedback on the surrounding medium.

  1. Ultra-fast outflows (aka UFOs) from AGNs and QSOs

    CERN Document Server

    Cappi, M; Giustini, M

    2013-01-01

    During the last decade, strong observational evidence has been accumulated for the existence of massive, high velocity winds/outflows (aka Ultra Fast Outflows, UFOs) in nearby AGNs and in more distant quasars. Here we briefly review some of the most recent developments in this field and discuss the relevance of UFOs for both understanding the physics of accretion disk winds in AGNs, and for quantifying the global amount of AGN feedback on the surrounding medium.

  2. Hot Dust Obscured Galaxies with Excess Blue Light: Dual AGN or Single AGN Under Extreme Conditions?

    Science.gov (United States)

    Assef, R. J.; Walton, D. J.; Brightman, M.; Stern, D.; Alexander, D.; Bauer, F.; Blain, A. W.; Diaz-Santos, T.; Eisenhardt, P. R. M.; Finkelstein, S. L.; Hickox, R. C.; Tsai, C.-W.; Wu, J. W.

    2016-03-01

    Hot dust-obscured galaxies (Hot DOGs) are a population of hyper-luminous infrared galaxies identified by the Wide-field Infrared Survey Explorer (WISE) mission from their very red mid-IR colors, and characterized by hot dust temperatures (T > 60 K). Several studies have shown clear evidence that the IR emission in these objects is powered by a highly dust-obscured active galactic nucleus (AGN) that shows close to Compton-thick absorption at X-ray wavelengths. Thanks to the high AGN obscuration, the host galaxy is easily observable, and has UV/optical colors usually consistent with those of a normal galaxy. Here we discuss a sub-population of eight Hot DOGs that show enhanced rest-frame UV/optical emission. We discuss three scenarios that might explain the excess UV emission: (i) unobscured light leaked from the AGN by reflection over the dust or by partial coverage of the accretion disk; (ii) a second unobscured AGN in the system; or (iii) a luminous young starburst. X-ray observations can help discriminate between these scenarios. We study in detail the blue excess Hot DOG WISE J020446.13-050640.8, which was serendipitously observed by Chandra/ACIS-I for 174.5 ks. The X-ray spectrum is consistent with a single, hyper-luminous, highly absorbed AGN, and is strongly inconsistent with the presence of a secondary unobscured AGN. Based on this, we argue that the excess blue emission in this object is most likely either due to reflection or a co-eval starburst. We favor the reflection scenario as the unobscured star formation rate needed to power the UV/optical emission would be ≳1000 M⊙ yr-1. Deep polarimetry observations could confirm the reflection hypothesis.

  3. HOT DUST OBSCURED GALAXIES WITH EXCESS BLUE LIGHT: DUAL AGN OR SINGLE AGN UNDER EXTREME CONDITIONS?

    Energy Technology Data Exchange (ETDEWEB)

    Assef, R. J.; Diaz-Santos, T. [Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago (Chile); Walton, D. J.; Brightman, M. [Space Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125 (United States); Stern, D.; Eisenhardt, P. R. M.; Tsai, C.-W. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Mail Stop 169-236, Pasadena, CA 91109 (United States); Alexander, D. [Department of Physics, Durham University, Durham DH1 3LE (United Kingdom); Bauer, F. [Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22 (Chile); Blain, A. W. [Physics and Astronomy, University of Leicester, 1 University Road, Leicester LE1 7RH (United Kingdom); Finkelstein, S. L. [The University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712 (United States); Hickox, R. C. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States); Wu, J. W., E-mail: roberto.assef@mail.udp.cl [UCLA Astronomy, P.O. Box 951547, Los Angeles, CA 90095-1547 (United States)

    2016-03-10

    Hot dust-obscured galaxies (Hot DOGs) are a population of hyper-luminous infrared galaxies identified by the Wide-field Infrared Survey Explorer (WISE) mission from their very red mid-IR colors, and characterized by hot dust temperatures (T > 60 K). Several studies have shown clear evidence that the IR emission in these objects is powered by a highly dust-obscured active galactic nucleus (AGN) that shows close to Compton-thick absorption at X-ray wavelengths. Thanks to the high AGN obscuration, the host galaxy is easily observable, and has UV/optical colors usually consistent with those of a normal galaxy. Here we discuss a sub-population of eight Hot DOGs that show enhanced rest-frame UV/optical emission. We discuss three scenarios that might explain the excess UV emission: (i) unobscured light leaked from the AGN by reflection over the dust or by partial coverage of the accretion disk; (ii) a second unobscured AGN in the system; or (iii) a luminous young starburst. X-ray observations can help discriminate between these scenarios. We study in detail the blue excess Hot DOG WISE J020446.13–050640.8, which was serendipitously observed by Chandra/ACIS-I for 174.5 ks. The X-ray spectrum is consistent with a single, hyper-luminous, highly absorbed AGN, and is strongly inconsistent with the presence of a secondary unobscured AGN. Based on this, we argue that the excess blue emission in this object is most likely either due to reflection or a co-eval starburst. We favor the reflection scenario as the unobscured star formation rate needed to power the UV/optical emission would be ≳1000 M{sub ⊙} yr{sup −1}. Deep polarimetry observations could confirm the reflection hypothesis.

  4. Radio AGN in the local universe: unification, triggering and evolution

    CERN Document Server

    Tadhunter, Clive

    2016-01-01

    Associated with one of the most important forms of active galactic nucleus (AGN) feedback, and showing a strong preference for giant elliptical host galaxies, radio AGN (L_1.4GHz > 10^24 W Hz^-1) are a key sub-class of the overall AGN population. Here I review our current state of understanding of the population of radio AGN at low and intermediate redshifts (z < 0.7), concentrating on their AGN and host galaxy properties, and covering three interlocking themes: the classification of radio AGN and its interpretation; the triggering and fuelling of the jet and AGN activity; and the evolution of the host galaxies. I show that much of the observed diversity in the AGN properties of radio AGN can be explained in terms of a combination of orientation/anisotropy, mass accretion rate, and variability effects. The detailed morphologies of the host galaxies are consistent with the triggering of strong-line radio galaxies (SLRG) in galaxy mergers. However, the star formation properties and cool ISM contents suggest ...

  5. Decreased Specific Star Formation Rates in AGN Host Galaxies

    CERN Document Server

    Shimizu, T Taro; Melendez, Marcio; Koss, Michael; Rosario, David

    2015-01-01

    We investigate the location of an ultra-hard X-ray selected sample of AGN from the Swift Burst Alert Telescope (BAT) catalog with respect to the main sequence (MS) of star-forming galaxies using Herschel-based measurements of the star formation rate (SFR) and stellar mass (\\mstar) from Sloan Digital Sky Survey (SDSS) photometry where the AGN contribution has been carefully removed. We construct the MS with galaxies from the Herschel Reference Survey and Herschel Stripe 82 Survey using the exact same methods to measure the SFR and \\mstar{} as the Swift/BAT AGN. We find a large fraction of the Swift/BAT AGN lie below the MS indicating decreased specific SFR (sSFR) compared to non-AGN galaxies. The Swift/BAT AGN are then compared to a high-mass galaxy sample (COLD GASS), where we find a similarity between the AGN in COLD GASS and the Swift/BAT AGN. Both samples of AGN lie firmly between star-forming galaxies on the MS and quiescent galaxies far below the MS. However, we find no relationship between the X-ray lum...

  6. Observations of AGN with large telescopes

    Directory of Open Access Journals (Sweden)

    Meg Urry

    2007-01-01

    Full Text Available Aquí describo cuatro cuestiones científicas apremiantes en lo referente a AGN que pueden ser abordadas empleando el telescopio de 10-m como el GTC. (1 La demografía de agujeros negros puede ser determinada mediante exploraciones profundas de longitudes de ondas múltiples (incluyendo rayos X seguidas por espectroscopia del óptico e infrarrojo con un telescopio de la clase de 10-m. En la época de la actividad pico de AGN, alrededor de z 2, la mayoría de los AGN será clasificada erróneamente por las exploraciones ópticas, ya que los más fuertemente oscurecidos solamente cuentan con emisión de la galaxia anfitriona en el óptico; si la galaxia es muy roja, la espectroscopia infrarroja resulta esencial. (2 Masas precisas de agujeros negros pueden ser determinadas utilizando la relación MBH-. Esta puede revelar las tendencias en luminosidad con masa de agujero negro que hasta ahora no resultan aparentes. La evolución de la relación MBH- con el corrimiento al rojo potencialmente constriñe modelos de formación de galaxias y de retroalimentación. La medición de requiere un telescopio de la clase de 10-m para todos los AGN excepto los más cercanos. (3 Imaginería óptica profunda de alta resolución puede revelar directamente las propiedades de la galaxia anfitriona de AGN, incluyendo los episodios de formación estelar. Con imaginería muy profunda, el GTC podrá de esta manera indagar las escalas de tiempo relativas de la actividad de formación estelar a escala galáctica y de la acreción nuclear de agujeros negros, revelando así la conexión entre agujeros negros y galaxias. (4 Finalmente, imaginería profunda con alta resolución espacial, en un amplio rango de longitudes de ondas desde el infrarrojo al óptico, promete esclarecer las condiciones físicas en jets relativistas y ofrecer importante información para llegar a entender sus procesos de emisión, su fuerza cinética y el contenido de materia.

  7. Reactor Neutrinos

    OpenAIRE

    Soo-Bong Kim; Thierry Lasserre; Yifang Wang

    2013-01-01

    We review the status and the results of reactor neutrino experiments. Short-baseline experiments have provided the measurement of the reactor neutrino spectrum, and their interest has been recently revived by the discovery of the reactor antineutrino anomaly, a discrepancy between the reactor neutrino flux state of the art prediction and the measurements at baselines shorter than one kilometer. Middle and long-baseline oscillation experiments at Daya Bay, Double Chooz, and RENO provided very ...

  8. ROSA-III double-ended break test series for a loss-of-coolant accident in a boiling water reactor

    Energy Technology Data Exchange (ETDEWEB)

    Tasaka, K.; Anoda, Y.; Koizumi, Y.; Kumamaru, H.; Nakamura, H.; Shiba, M.; Suzuki, M.; Yonomoto, T.

    1985-01-01

    The Rig of Safety Assessment (ROSA) III facility is a volumetrically scaled (1/424) boiling water reactor (BWR) system with an electrically heated core designed for integral loss-of-coolant accident (LOCA) and emergency-core-cooling-system (ECCS) tests. Experimental results obtained so far confirm that the severest single failure assumption in ECCS is the high-pressure core spray system failure even in a large-break LOCA in a BWR. The measured peak cladding temperature was well below the present safety criterion of 1473 K, even with the single failure assumption in ECCS, and the effectiveness of ECCS for core cooling during a double-ended-break LOCA has been confirmed. The overall agreement between the results calculated by the RELAP4/MOD6/U4/J3 computer code and the experimental results is good. The similarity between the ROSA-III test and a BWR LOCA has been confirmed through the comparison of calculated results for the ROSA-III facility and a BWR system.

  9. Establishing the mid-infrared selection of AGN

    Science.gov (United States)

    Haas, Martin; Chini, Rolf; Huchra, John P.; Leipski, Christian; Mueller, Sven A. H.; Ott, Stephan; Schartel, Norbert; Siebenmorgen, Ralf; Wilkes, Belinda

    2004-09-01

    Since a large fraction of AGN is missed in common UV-excess surveys, and even in radio, near-IR and X-ray surveys, we have searched for AGN via mid-IR emission from their nuclear dust at T>300 K. This is a new AGN selection technique, and one not affected by extinction. Among 3000 high galactic latitude sources randomly detected by ISO at 6.7 microns we have discovered a population of extremly infra-red, mostly unknown objects. This population is not detected on IRAS-ADDSCANs and very few of these sources show up in the NVSS and FIRST radio surveys. Various colour criteria from 2MASS and optical wavebands and the comparison with known object types show that the sources have a higher MIR excess than those seen in the ELAIS survey. Our analysis suggests that we have, in fact, found AGN with a pronounced MIR emission. We estimate that, if this is true, the number counts of AGN will have to be revised dramatically upwards. In order to verify our hypothesis on the AGN nature of the sources, we have selected MIR-excess AGN candidates with unknown classification from our ISO survey. First results from optical spectrocopy show some to be AGN, but also that many of the sources are extremely reddened. Therefore, we here apply for 5-40 micron IRS spectroscopy of 30 of the remaining unidentified sources to establish their nature as AGN, to determine the fraction of type 1 and 2 AGN among this MIR selected sample, and to constrain their additional starburst contribution. While new IR surveys from Spitzer are expected to find more such interesting objects, we have already identified a promising sample. The requested observations will make a significant contribution to the debate on the entire AGN population.

  10. Hot Dust Obscured Galaxies with Excess Blue Light: Dual AGN or Single AGN Under Extreme Conditions?

    CERN Document Server

    Assef, R J; Brightman, M; Stern, D; Alexander, D; Bauer, F; Blain, A W; Diaz-Santos, T; Eisenhardt, P R M; Finkelstein, S L; Hickox, R C; Tsai, C -W; Wu, J W

    2015-01-01

    Hot Dust-Obscured Galaxies (Hot DOGs) are a population of hyper-luminous infrared galaxies identified by the WISE mission from their very red mid-IR colors, and characterized by hot dust temperatures ($T>60~\\rm K$). Several studies have shown clear evidence that the IR emission in these objects is powered by a highly dust-obscured AGN that shows close to Compton-thick absorption at X-ray wavelengths. Thanks to the high AGN obscuration, the host galaxy is easily observable, and has UV/optical colors usually consistent with those of a normal galaxy. Here we discuss a sub-population of 8 Hot DOGs that show enhanced rest-frame UV/optical emission. We discuss three scenarios that might explain the excess UV emission: (i) unobscured light leaked from the AGN by reflection over the dust or by partial coverage of the accretion disk; (ii) a second unobscured AGN in the system; or (iii) a luminous young starburst. X-ray observations can help discriminate between these scenarios. We study in detail the blue excess Hot D...

  11. X-ray AGN in the XMM-LSS galaxy clusters: no evidence for AGN suppression

    CERN Document Server

    Koulouridis, E; Melnyk, O; Elyiv, A; Georgantopoulos, I; Clerc, N; Surdej, J; Chiappetti, L; Pierre, M

    2014-01-01

    We present a study of the overdensity of X-ray selected AGN in 33 galaxy clusters in the XMM-LSS field, up to redhift z=1.05. Previous studies have shown that the presence of X-ray selected AGN in rich galaxy clusters is suppressed. In the current study we investigate the occurrence of X-ray selected AGN in low and moderate X-ray luminosity galaxy clusters. Due to the wide contiguous XMM-LSS survey area we are able to extend the study to the cluster outskirts. We therefore determine the projected overdensity of X-ray point-like sources out to 6r_{500} radius. To provide robust statistical results we also use a stacking analysis of the cluster projected overdensities. We investigate whether the observed X-ray overdensities are to be expected by estimating also the corresponding optical galaxy overdensities. We find a positive X-ray projected overdensity at the first radial bin, which is however of the same amplitude as that of optical galaxies. Therefore, no suppression of X-ray AGN activity with respect to th...

  12. AGN content of X-ray, IR and radio sources

    Science.gov (United States)

    Mickaelian, A. M.; Paronyan, G. M.; Abrahamyan, H. V.; Gyulzadyan, M. V.; Mikayelyan, G. A.

    2016-09-01

    We have carried out a number of surveys and identification works related to X-ray, IR and radio sources and searched for extragalactic ones. Among them, most interesting are Active Galactic Nuclei (AGN) and Starburst (SB) Galaxies. Some 4500 AGN have been revealed from ROSAT BSC and FSC sources, and many more are hidden ones; those showing evidence of activity but with no emission lines in optical wavelengths. We estimated AGN content of X-ray sources as 52.9%. IR sources contain thousands of SBs, and most important are those having signs of interaction and/or merging. We have carried out optical identifications of IRAS point sources, and 1278 IR galaxies have been revealed, including LIRGs and ULIRGs. We have also combined IRAS PSC and FSC catalogs and compiled its extragalactic sample, which allowed to estimate AGN content among IR sources as 23.7%. Extragalactic radio sources contain bright galaxies, AGN and SBs. We have studied the border between AGN and normal galaxies by radio/optical flux ratios to establish which objects may be attributed to AGN based on radio properties. Interestingly, absolute majority of objects associated with both X-ray and radio sources are AGN.

  13. CAIXA. II. AGNs from excess variance analysis (Ponti+, 2012) [Dataset

    NARCIS (Netherlands)

    Ponti, G.; Papadakis, I.E.; Bianchi, S.; Guainazzi, M.; Matt, G.; Uttley, P.; Bonilla, N.F.

    2012-01-01

    We report on the results of the first XMM-Newton systematic "excess variance" study of all the radio quiet, X-ray unobscured AGN. The entire sample consist of 161 sources observed by XMM-Newton for more than 10ks in pointed observations, which is the largest sample used so far to study AGN X-ray var

  14. Do AGN suppress star formation in early-type galaxies?

    OpenAIRE

    Schawinski, Kevin

    2010-01-01

    The observation that AGN host galaxies preferentially inhabit the "green valley" between the blue cloud and the red sequence has significant consequences for our understanding of the co-evolution of galaxies and black holes via accretion events. I discuss the interpretation of green valley AGN host galaxy colours with particular focus on early-type galaxies.

  15. The Environment of AGNs in the Sloan Digital Sky Survey

    CERN Document Server

    Miller, C J; Gómez, P; Hopkins, A; Bernardi, M; Miller, Christopher J.; Nichol, Robert C.; Gomez, Percy; Hopkins, Andrew; Bernardi, Mariangela

    2003-01-01

    We present the observed fraction of galaxies with an Active Galactic Nucleus (AGN) as a function of environment in the Early Data Release of the Sloan Digital Sky Survey (SDSS). Using 4921 galaxies between 0.05 10^8 years), or that the AGN burst more often than expected; ~40 times over the redshift range of our sample.

  16. Are Radio AGN Powered by Accretion or Black Hole Spin?

    CERN Document Server

    McNamara, B R; Nulsen, P E J

    2010-01-01

    We compare accretion and black hole spin as potential energy sources for outbursts from AGN in brightest cluster galaxies (BCGs). We find that the distribution of AGN power estimated from X-ray cavities is consistent with a broad range of both spin parameter and accretion rate. Sufficient quantities of molecular gas are available in most BCGs to power their AGN by accretion alone. However, we find no correlation between AGN power and molecular gas mass. For a given AGN power, the BCG's gas mass and accretion efficiency vary by more than two orders of magnitude. Most of the molecular gas in BCGs is apparently consumed by star formation or is driven out of the nucleus by the AGN before it reaches the nuclear black hole. Bondi accretion from hot atmospheres is generally unable to fuel powerful AGN, unless their black holes are more massive than their bulge luminosities imply. We identify several powerful AGN that reside in relatively gas-poor galaxies, indicating an unusually efficient mode of accretion, or that...

  17. New insights on the Starburst-AGN connection

    Directory of Open Access Journals (Sweden)

    Roberto Cid Fernandes

    2001-01-01

    Full Text Available We review recent evidence for a connection between star-formation and nuclea r activity in Seyfert galaxies. We speculate that AGN activity and star-formation occur on "cycles" of ~ 108 yr, and that there may be an evolutionary link between the AGN properties and the age of the nuclear stellar population.

  18. Warm Absorber Diagnostics of AGN Dynamics

    Science.gov (United States)

    Kallman, Timothy

    Warm absorbers and related phenomena are observable manifestations of outflows or winds from active galactic nuclei (AGN) that have great potential value. Understanding AGN outflows is important for explaining the mass budgets of the central accreting black hole, and also for understanding feedback and the apparent co-evolution of black holes and their host galaxies. In the X-ray band warm absorbers are observed as photoelectric absorption and resonance line scattering features in the 0.5-10 keV energy band; the UV band also shows resonance line absorption. Warm absorbers are common in low luminosity AGN and they have been extensively studied observationally. They may play an important role in AGN feedback, regulating the net accretion onto the black hole and providing mechanical energy to the surroundings. However, fundamental properties of the warm absorbers are not known: What is the mechanism which drives the outflow?; what is the gas density in the flow and the geometrical distribution of the outflow?; what is the explanation for the apparent relation between warm absorbers and the surprising quasi-relativistic 'ultrafast outflows' (UFOs)? We propose a focused set of model calculations that are aimed at synthesizing observable properties of warm absorber flows and associated quantities. These will be used to explore various scenarios for warm absorber dynamics in order to answer the questions in the previous paragraph. The guiding principle will be to examine as wide a range as possible of warm absorber driving mechanisms, geometry and other properties, but with as careful consideration as possible to physical consistency. We will build on our previous work, which was a systematic campaign for testing important class of scenarios for driving the outflows. We have developed a set of tools that are unique and well suited for dynamical calculations including radiation in this context. We also have state-of-the-art tools for generating synthetic spectra, which are

  19. Transrelativistic pair plasmas in AGN jets

    DEFF Research Database (Denmark)

    Bottcher, M.; Pohl, M.; Schlickeiser, R.

    1999-01-01

    Models of relativistic jets filled with ultrarelativistic pair plasma are very successful in explaining the broadband radiation of gamma-ray blazars. Assuming that the initial injection and cooling of ultrarelativistic pair plasma in an AGN jet has occurred, producing the observed high-energy gamma......-ray radiation, we investigate the further evolution of the pair plasma as it continues to move out from the central engine. The effects of thermalization and reacceleration, the emission of pair bremsstrahlung and annihilation radiation and the bulk Compton process, and the possible application to MeV blazars...

  20. Role of Reconnection in AGN Jets

    CERN Document Server

    Lyutikov, M

    2003-01-01

    We discuss the possible role of reconnection in electro-magnetically dominated cores of relativistic AGN jets. We suggest that reconnection may proceed in a two-fold fashion: initial explosive collapse on the Alfven time-scale of a current-carrying jet (which is of the order of the light crossing time) and subsequent slow quasi-steady reconnection. Sites of explosive collapse are associated with bright knots, while steady-state reconnection re-energizes particles in the ``bridges'' between the knots. Ohmic dissipation in reconnection layers leads to particle acceleration either by inductive electric fields or by stochastic particle acceleration in the ensuing electro-magnetic turbulence.

  1. Clues to the Structure of AGN Through Massive Variability Surveys

    Science.gov (United States)

    Lawrence, A.

    2016-06-01

    Variability studies hold information on otherwise unresolvable regions in Active Galactic Nuclei (AGN). Population studies of large samples likewise have been very productive for our understanding of AGN. These two themes are coming together in the idea of systematic variability studies of large samples - with SDSS, PanSTARRS, and soon, LSST. I summarise what we have learned about the optical and UV variability of AGN, and what it tells us about accretion discs and the BLR. The most exciting recent results have focused on rare large-scale outbursts and collapses - Tidal Disruption Events, changing-look AGN, and large amplitude microlensing. All of these promise to give us new insight into AGN physics.

  2. Clues to the Structure of AGN through massive variability surveys

    CERN Document Server

    Lawrence, Andy

    2016-01-01

    Variability studies hold information on otherwise unresolvable regions in Active Galactic Nuclei (AGN). Population studies of large samples likewise have been very productive for our understanding of AGN. These two themes are coming together in the idea of systematic variability studies of large samples - with SDSS, PanSTARRS, and soon, LSST. I summarise what we have learned about the optical and UV variability of AGN, and what it tells us about accretion discs and the BLR. The most exciting recent results have focused on rare large-scale outbursts and collapses - Tidal Disruption Events, changing-look AGN, and large amplitude microlensing. All of these promise to give us new insight into AGN physics.

  3. Challenges in Finding AGNs in the Low Luminosity Regime

    Science.gov (United States)

    Satyapal, Shobita; Abel, Nick; Secrest, Nathan; Singh, Amrit; Ellison, Sara

    2016-08-01

    Low luminosity AGNs are an important component of the AGN population. They are often found in the lowest mass galaxies or galaxies that lack classical bulges, a demographic that places important constraints to models of supermassive black hole seed formation and merger-free models of AGN fueling. The detection of AGNs in this low luminosity regime is challenging both because star formation in the host galaxy can dominate the optical spectrum and gas and dust can obscure the central engine at both optical and X-ray wavelengths. Thus while mid-infrared color selection and X-ray observations at energies review the effectiveness of uncovering AGNs in the low luminosity regime using multiwavength investigations, with a focus on infrared spectroscopic signatures.

  4. The Spectral Energy Distributions of Quasars and AGN

    CERN Document Server

    Wilkes, B J

    2003-01-01

    Active Galactic Nuclei (AGN) are multiwavelength emitters. To have any hope of understanding them, or even to determine their energy output, we must observe them with many telescopes. I will review what we have learned from broad-band observations of relatively bright, low-redshift AGN over the past 15 years. AGN can be found at all wavelengths but each provides a different view of the intrinsic population, often with little overlap between samples selected in different wavebands. I look forward to the full view of the intrinsic population which we will obtain over the next few years with surveys using today's new, sensitive observatories. These surveys are already finding enough new and different AGN candidates to pose the question "What IS an AGN?".

  5. A UV to mid-IR study of AGN selection

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Sun Mi; Kochanek, Christopher S. [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Assef, Roberto [Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago (Chile); Brown, Michael J. I. [School of Physics, Monash University, Clayton, Vic 3800 (Australia); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Mail Stop 169-221, Pasadena, CA 91109 (United States); Jannuzi, Buell T. [Department of Astronomy and Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Gonzalez, Anthony H. [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Hickox, Ryan C. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States); Moustakas, John [Department of Physics and Astronomy, Siena College, 515 Loudon Road, Loudonville, NY 12211 (United States)

    2014-07-20

    We classify the spectral energy distributions (SEDs) of 431,038 sources in the 9 deg{sup 2} Boötes field of the NOAO Deep Wide-Field Survey (NDWFS). There are up to 17 bands of data available per source, including ultraviolet (GALEX), optical (NDWFS), near-IR (NEWFIRM), and mid-infrared (IRAC and MIPS) data, as well as spectroscopic redshifts for ∼20,000 objects, primarily from the AGN and Galaxy Evolution Survey. We fit galaxy, active galactic nucleus (AGN), stellar, and brown dwarf templates to the observed SEDs, which yield spectral classes for the Galactic sources and photometric redshifts and galaxy/AGN luminosities for the extragalactic sources. The photometric redshift precision of the galaxy and AGN samples are σ/(1 + z) = 0.040 and σ/(1 + z) = 0.169, respectively, with the worst 5% outliers excluded. On the basis of the χ{sub ν}{sup 2} of the SED fit for each SED model, we are able to distinguish between Galactic and extragalactic sources for sources brighter than I = 23.5 mag. We compare the SED fits for a galaxy-only model and a galaxy-AGN model. Using known X-ray and spectroscopic AGN samples, we confirm that SED fitting can be successfully used as a method to identify large populations of AGNs, including spatially resolved AGNs with significant contributions from the host galaxy and objects with the emission line ratios of 'composite' spectra. We also use our results to compare with the X-ray, mid-IR, optical color, and emission line ratio selection techniques. For an F-ratio threshold of F > 10, we find 16,266 AGN candidates brighter than I = 23.5 mag and a surface density of ∼1900 AGN deg{sup –2}.

  6. Hidden AGNs in Early-Type Galaxies

    CERN Document Server

    Paggi, A; Civano, F; Pellegrini, S; Elvis, M; Kim, D -W

    2015-01-01

    We present a stacking analysis of the complete sample of Early Type Galaxies (ETGs) in the \\textit{Chandra} COSMOS (C-COSMOS) survey, to explore the nature of the X-ray luminosityin the redshift and stellar luminosity ranges \\(0AGN. To discriminate between the relative importance of these two components, we (1) compare our results with the relation observed in the local universe \\(L_{X,gas}\\propto L_K^{4.5}\\) for hot gaseous halos emission in ETGs, and (2) evaluate the spectral signature of each stacked bin. We find two regimes where the non-stellar X-ray emission is hard, consistent with AGN emission. First, there is evidence of hard, absorbed X-ray emission in stacked bins including relatively high z (\\(\\sim 1.2\\)) ETGs with average high X-ray luminosity (\\(L_{X-LMXB}\\gtrsim 6\\times{10}^{42}\\mbox{ er...

  7. Interactions, star formation and AGN activity

    CERN Document Server

    Li, Cheng; Heckman, Timothy M; White, Simon D M; Jing, Y P

    2007-01-01

    It has long been known that galaxy interactions are associated with enhanced star formation. In a companion paper, we explored this connection by applying a variety of statistics to SDSS data. In particular, we showed that specific star formation rates of galaxies are higher if they have close neighbours. Here we apply exactly the same techniques to AGN in the survey, showing that close neighbours are not associated with any similar enhancement of nuclear activity. Star formation is enhanced in AGN with close neighbours in exactly the same way as in inactive galaxies, but the accretion rate onto the black hole, as estimated from the extinction-corrected [O III] luminosity, is not influenced by the presence or absence of companions. Previous work has shown that galaxies with more strongly accreting black holes contain more young stars in their inner regions. This leads us to conclude that star formation induced by a close companion and star formation associated with black hole accretion are distinct events. Th...

  8. The link between broad emission line fluctuations and non-thermal emission from the inner AGN jet

    CERN Document Server

    León-Tavares, J; Lobanov, A; Valtaoja, E; Arshakian, T G

    2014-01-01

    AGN reverberate when the broad emission lines respond to changes of the ionizing thermal continuum emission. Reverberation measurements have been commonly used to estimate the size of the broad-line region (BLR) and the mass of the central black hole. However, reverberation mapping studies have been mostly performed on radio-quiet sources where the contribution of the jet can be neglected. In radio-loud AGN, jets and outflows may affect substantially the relation observed between the ionizing continuum and the line emission. To investigate this relation, we have conducted a series of multiwavelength studies of radio-loud AGN, combining optical spectral line monitoring with regular VLBI observations. Our results suggest that at least a fraction of the broad-line emitting material can be located in a sub-relativistic outflow ionized by non-thermal continuum emission generated in the jet at large distances (> 1pc) from the central engine of AGN. This finding may have a strong impact on black hole mass estimates ...

  9. Starburst-AGN mixing: II. Optically-selected active galaxies

    CERN Document Server

    Davies, Rebecca L; Ho, I-Ting; Dopita, Michael A

    2014-01-01

    We use 4 galaxies from the Calar Alto Legacy Integral Field Area (CALIFA) survey with clear signs of accretion onto supermassive black holes to investigate the relative contribution of star-formation and active galactic nucleus (AGN) activity to the line-emission of each galaxy as a function of radius. The combination of star-formation and AGN activity produces curved "mixing sequences" on standard optical diagnostic diagrams, and the fraction of emission due to AGN activity decreases smoothly with distance from the centre of the galaxy. We use the AGN activity profiles to calculate the size of the AGN narrow line regions, which have radii of ~ 6.3 kpc. We calculate the fractional contribution of the star-formation and the AGN activity to the global Halpha, [O II] $\\lambda \\lambda$ 3727,3729 and [O III] $\\lambda$ 5007 luminosities of each galaxy, and show that both ionization sources contribute significantly to the emission in all three lines. We use weighted combinations of stellar and AGN photoionization mo...

  10. Misclassified type 1 AGNs in the local universe

    CERN Document Server

    Woo, Jong-Hak; Park, Daeseong; Bae, Hyun-Jin; Kim, Jae-Hyuk; Lee, Seung-Eun; Kim, Sang Chul; Kwon, Hong-Jin

    2014-01-01

    We search for misclassified type 1 AGNs among type 2 AGNs identified with emission line flux ratios, and investigate the properties of the sample. Using 4\\,113 local type 2 AGNs at $0.02AGNs among type 2 AGN sample is $\\sim$3.5%, implying that a large number of missing type 1 AGN population may exist. The misclassified type 1 AGNs have relatively low luminosity with a mean broad \\Ha\\ luminosity, log L$_{H\\alpha} = 40.50\\pm0.35$ \\ergs, while black hole mass of the sample is comparable to that of the local black hole population, with a mean black hole mass, log M$_{\\rm BH} = 6.94\\pm0.51$ M$_{\\odot}$. The mean Eddington ratio of the sample is log L$_{\\rm bol}$/L$_{\\rm Edd}$ = $-2.00\\pm0.40$, indicating tha...

  11. Intermediate Inclinations of Type 2 Coronal-Line Forest AGN

    CERN Document Server

    Rose, Marvin; Crenshaw, Michael; Glidden, Ana

    2015-01-01

    Coronal-Line Forest Active Galactic Nuclei (CLiF AGN) are remarkable in the sense that they have a rich spectrum of dozens of coronal emission lines (e.g. [FeVII], [FeX] and [NeV]) in their spectra. Rose, Elvis & Tadhunter (2015) suggest that the inner obscuring torus wall is the most likely location of the coronal line region in CLiF AGN, and the unusual strength of the forbidden high ionization lines is due to a specific AGN-torus inclination angle. Here we test this suggestion using mid-IR colours (4.6$\\mu$m-22$\\mu$m) from the Wide-Field Infrared Survey Explorer (WISE) for the CLiF AGN. We use the Fischer et al. (2014) result that showed that as the AGN-torus inclination becomes more face on, the Spitzer 5.5$\\mu$m to 30$\\mu$m colours become bluer. We show that the [W2-W4] colours for the CLiF AGN ($\\langle$[W2-W4]$\\rangle$ = 5.92$\\pm$0.12) are intermediate between SDSS type 1 ($\\langle$[W2-W4]$\\rangle$ = 5.22$\\pm$0.01) and type 2 AGN ($\\langle$[W2-W4]$\\rangle$ = 6.35$\\pm$0.03). This implies that the AG...

  12. Identifying Luminous AGN in Deep Surveys: Revised IRAC Selection Criteria

    CERN Document Server

    Donley, J L; Brusa, M; Capak, P; Cardamone, C N; Civano, F; Ilbert, O; Impey, C D; Kartaltepe, J S; Miyaji, T; Salvato, M; Sanders, D B; Trump, J R; Zamorani, G

    2012-01-01

    Spitzer IRAC selection is a powerful tool for identifying luminous AGN. For deep IRAC data, however, the AGN selection wedges currently in use are heavily contaminated by star-forming galaxies, especially at high redshift. Using the large samples of luminous AGN and high-redshift star-forming galaxies in COSMOS, we redefine the AGN selection criteria for use in deep IRAC surveys. The new IRAC criteria are designed to be both highly complete and reliable, and incorporate the best aspects of the current AGN selection wedges and of infrared power-law selection while excluding high redshift star-forming galaxies selected via the BzK, DRG, LBG, and SMG criteria. At QSO-luminosities of log L(2-10 keV) (ergs/s) > 44, the new IRAC criteria recover 75% of the hard X-ray and IRAC-detected XMM-COSMOS sample, yet only 38% of the IRAC AGN candidates have X-ray counterparts, a fraction that rises to 52% in regions with Chandra exposures of 50-160 ks. X-ray stacking of the individually X-ray non-detected AGN candidates lead...

  13. Mini-Survey on SDSS OIII AGN with Swift

    Science.gov (United States)

    Angelini, Lorella

    2008-01-01

    The number of AGN and their luminosity distribution are crucial parameters for our understanding of the AGN phenomenon. There is a common wisdom that every massive galaxy has a massive black hole. However, most of these objects either are not radiating or until recently have been very difficult to detect. The Sloan Digital Sky Survey (SDSS) data, based on the [OIII] line indicate that perhaps up to 20% of all galaxies may be classified as AGN a surprising result that must be checked with independent data. X-ray surveys have revealed that hard X-ray selected AGN show a strong luminosity dependent evolution and their luminosity function (LF) shows a dramatic break towards low $L_X$ (at all $z$). This is seen for all types of AGN, but is stronger for the broad-line objects. In sharp contrast, the local LF of {it optically-selected samples} shows no such break and no differences between narrow and broad-line objects. Assuming both hard X-ray and [O{\\sc iii}] emission are fair indicators of AGN activity, it is important to understand this discrepancy. We present here the results of a min-survey done with Swift on a selected sample of SDSS selected AGN. The objects have been sampled at different L([O{\\sc iii}]) to check the relation with the $L_X$ observed with Swift.

  14. Radio faint AGN: a tale of two populations

    CERN Document Server

    Padovani, P; Kellermann, K I; Miller, N; Mainieri, V; Tozzi, P

    2015-01-01

    We study the Extended Chandra Deep Field South (E-CDFS) Very Large Array sample, which reaches a flux density limit at 1.4 GHz of 32.5 microJy at the field centre and redshift ~ 4, and covers ~ 0.3 deg^2. Number counts are presented for the whole sample while the evolutionary properties and luminosity functions are derived for active galactic nuclei (AGN). The faint radio sky contains two totally distinct AGN populations, characterised by very different evolutions, luminosity functions, and Eddington ratios: radio-quiet (RQ)/radiative-mode, and radio-loud/jet-mode AGN. The radio power of RQ AGN evolves ~ (1+z)^2.5, similarly to star-forming galaxies, while the number density of radio-loud ones has a peak at ~ 0.5 and then declines at higher redshifts. The number density of radio-selected RQ AGN is consistent with that of X-ray selected AGN, which shows that we are sampling the same population. The unbiased fraction of radiative-mode RL AGN, derived from our own and previously published data, is a strong funct...

  15. Radio AGN in the local universe: unification, triggering and evolution

    Science.gov (United States)

    Tadhunter, Clive

    2016-06-01

    Associated with one of the most important forms of active galactic nucleus (AGN) feedback, and showing a strong preference for giant elliptical host galaxies, radio AGN (L_{1.4 GHz} > 10^{24} W Hz^{-1}) are a key sub-class of the overall AGN population. Recently their study has benefitted dramatically from the availability of high-quality data covering the X-ray to far-IR wavelength range obtained with the current generation of ground- and space-based telescope facilities. Reflecting this progress, here I review our current state of understanding of the population of radio AGN at low and intermediate redshifts (z < 0.7), concentrating on their nuclear AGN and host galaxy properties, and covering three interlocking themes: the classification of radio AGN and its interpretation; the triggering and fuelling of the jet and AGN activity; and the evolution of the host galaxies. I show that much of the observed diversity in the AGN properties of radio AGN can be explained in terms of a combination of orientation/anisotropy, mass accretion rate, and variability effects. The detailed morphologies of the host galaxies are consistent with the triggering of strong-line radio galaxies (SLRG) in galaxy mergers. However, the star formation properties and cool ISM contents suggest that the triggering mergers are relatively minor in terms of their gas masses in most cases, and would not lead to major growth of the supermassive black holes and stellar bulges; therefore, apart from a minority (<20 %) that show evidence for higher star formation rates and more massive cool ISM reservoirs, the SLRG represent late-time re-triggering of activity in mature giant elliptical galaxies. In contrast, the host and environmental properties of weak-line radio galaxies (WLRG) with Fanaroff-Riley class I radio morphologies are consistent with more gradual fuelling of the activity via gas accretion at low rates onto the supermassive black holes.

  16. Disentangling AGN and Star Formation in Soft X-Rays

    Science.gov (United States)

    LaMassa, Stephanie M.; Heckman, T. M.; Ptak, A.

    2012-01-01

    We have explored the interplay of star formation and active galactic nucleus (AGN) activity in soft X-rays (0.5-2 keV) in two samples of Seyfert 2 galaxies (Sy2s). Using a combination of low-resolution CCD spectra from Chandra and XMM-Newton, we modeled the soft emission of 34 Sy2s using power-law and thermal models. For the 11 sources with high signal-to-noise Chandra imaging of the diffuse host galaxy emission, we estimate the luminosity due to star formation by removing the AGN, fitting the residual emission. The AGN and star formation contributions to the soft X-ray luminosity (i.e., L(sub x,AGN) and L(sub x,SF)) for the remaining 24 Sy2s were estimated from the power-law and thermal luminosities derived from spectral fitting. These luminosities were scaled based on a template derived from XSINGS analysis of normal star-forming galaxies. To account for errors in the luminosities derived from spectral fitting and the spread in the scaling factor, we estimated L(sub x,AGN) and L(sub x,SF))from Monte Carlo simulations. These simulated luminosities agree with L(sub x,AGN) and L(sub x,SF) derived from Chandra imaging analysis within a 3sigma confidence level. Using the infrared [Ne ii]12.8 micron and [O iv]26 micron lines as a proxy of star formation and AGN activity, respectively, we independently disentangle the contributions of these two processes to the total soft X-ray emission. This decomposition generally agrees with L(sub x,SF) and L(sub x,AGN) at the 3 sigma level. In the absence of resolvable nuclear emission, our decomposition method provides a reasonable estimate of emission due to star formation in galaxies hosting type 2 AGNs.

  17. Multiwavelength Studies of X-ray Selected AGN

    Science.gov (United States)

    Paronyan, G. M.; Mickaelian, A. M.; Abrahamyan, H. V.

    2016-06-01

    We present multiwavelength studies of the AGN and galaxy samples of the HRC/BHRC Joint Catalogue, optical identifications of ROSAT BSC and FSC sources. The extragalactic sample contains 4253 candidate AGN and 492 galaxies without a sign of activity. Multiwavelength data were retrieved from γ-ray to radio providing 62 photometric points in the range 100 GeV - 151 MHz. Color-color diagrams were built to investigate the nature of these objects. Activity types were taken from the SDSS DR12 spectroscopic database, as well as NED and HyperLEDA. So far, 451 objects remain as AGN candidates to be confirmed by spectroscopic observations.

  18. The Starburst Model for AGN Past, Present & Future

    CERN Document Server

    Fernandes, R C

    1996-01-01

    It is now eleven years since Terlevich \\& Melnick first proposed an `AGN without black-holes' model, an idea which since then evolved into what is now called the starburst model for AGN. This model has been the subject of much debate in the last decade, with observational evidence both for and against it further fuelling the controversy. Can we after all these years reach a veredictum on whether starbursts can power AGN? This contribution tries to answer this question reviewing the main achievements of the starburst model, its current status and future prospects.

  19. Multifunctional reactors

    NARCIS (Netherlands)

    Westerterp, K.R.

    1992-01-01

    Multifunctional reactors are single pieces of equipment in which, besides the reaction, other functions are carried out simultaneously. The other functions can be a heat, mass or momentum transfer operation and even another reaction. Multifunctional reactors are not new, but they have received much

  20. AGN environments: is the viewing angle sufficient to explain the difference between broad-line and narrow-line AGN? -- A low-redshift study of close AGN neighbours. Paper I

    CERN Document Server

    Villarroel, Beatriz; Matsuoka, Yoshiki

    2012-01-01

    The unification of active galactic nuclei (AGN) is a model that has been difficult to test due to the lack of knowledge on the intrinsic luminosities of the objects. We present a test were we probe the model by statistical investigation of the neighbours to AGN at redshifts 0.03 < z < 0.2 within a projected distance of 350 kpc and |\\Delta z|<0.001, 0.006, 0.012 and 0.03 between AGN and neighbour. 1658 Type-1 (broad-line) AGN-galaxy pairs and 5698 Type-2 AGN-galaxy pairs with spectroscopic redshifts from the Data Release 7 of Sloan Digital Sky Survey were used together with a complementary set of pairs with photometric redshifts on the neighbour galaxies (13519 Type-1 AGN-galaxy and 58743 Type-2 AGN-galaxy pairs). Morphologies for the AGN host galaxies were derived from the Galaxy Zoo project. Our results suggest that broad-line AGN and narrow-line AGN reside in widely different environments where the neighbours to Type-2 AGN are more star-forming and bluer than those of Type-1 AGN. There is a colour-...

  1. The MOSDEF Survey: AGN Multi-wavelength Identification, Selection Biases, and Host Galaxy Properties

    Science.gov (United States)

    Azadi, Mojegan; Coil, Alison L.; Aird, James; Reddy, Naveen; Shapley, Alice; Freeman, William R.; Kriek, Mariska; Leung, Gene C. K.; Mobasher, Bahram; Price, Sedona H.; Sanders, Ryan L.; Shivaei, Irene; Siana, Brian

    2017-01-01

    We present results from the MOSFIRE Deep Evolution Field (MOSDEF) survey on the identification, selection biases, and host galaxy properties of 55 X-ray, IR, and optically selected active galactic nuclei (AGNs) at 1.4optical spectra of galaxies and AGNs and use the BPT diagram to identify optical AGNs. We examine the uniqueness and overlap of the AGNs identified at different wavelengths. There is a strong bias against identifying AGNs at any wavelength in low-mass galaxies, and an additional bias against identifying IR AGNs in the most massive galaxies. AGN hosts span a wide range of star formation rates (SFRs), similar to inactive galaxies once stellar mass selection effects are accounted for. However, we find (at ∼2–3σ significance) that IR AGNs are in less dusty galaxies with relatively higher SFR and optical AGNs in dusty galaxies with relatively lower SFR. X-ray AGN selection does not display a bias with host galaxy SFR. These results are consistent with those from larger studies at lower redshifts. Within star-forming galaxies, once selection biases are accounted for, we find AGNs in galaxies with similar physical properties as inactive galaxies, with no evidence for AGN activity in particular types of galaxies. This is consistent with AGNs being fueled stochastically in any star-forming host galaxy. We do not detect a significant correlation between SFR and AGN luminosity for individual AGN hosts, which may indicate the timescale difference between the growth of galaxies and their supermassive black holes.

  2. Metals and dust in high redshift AGNs

    CERN Document Server

    Maiolino, R; Marconi, A; Schneider, R; Bianchi, S; Pedani, M; Pipino, A; Matteucci, F; Cox, P; Caselli, P

    2006-01-01

    We summarize some recent results on the metallicity and dust properties of Active Galactic Nuclei (AGN) at high redshift (110). The properties of dust in high-z QSOs are discussed within the context of the dust production mechanisms in the early universe. The dust extinction curve is observed to evolve beyond z>4, and by z~6 it is well described by the properties expected for dust produced by SNe, suggesting that the latter is the main mechanism of dust production in the early universe. We also show that the huge dust masses observed in distant QSOs can be accounted for by SN dust within the observational constraints currently available. Finally, we show that QSO winds, which have been proposed as an alternative mechanism of dust production, may also contribute significantly to the total dust budget at high redshift.

  3. Starbursts and AGN Fueling through Secular Evolution

    CERN Document Server

    Combes, F

    2006-01-01

    Except in the most extreme cases of nuclear activity, either starbursts or AGN, it is difficult to find observationnally a close link between the dynamics and the activity. Theoretically however, the necessary step to fuel the gas to the center, is that gravity torques are created through a non-axisymmetric pattern, either bar and/or spiral, triggered or not by a tidal interaction. We describe the sequence of processes for a typical evolution cycle for a spiral galaxy, and the possible efficient feedback mechanisms. The various morphologies and dynamical states of spiral galaxies are interpreted in terms of a sequence of evolutionary phases, and the corresponding time-scales can be estimated from observations. In this scenario, activity in galaxies is related to the appearance of bar instability, although they might not be synchronised in phase. The role of external gas accretion in the secular evolution is discussed.

  4. Demography of High-Redshift AGN

    Directory of Open Access Journals (Sweden)

    Fabrizio Fiore

    2012-01-01

    Universe during its infancy. We review the latest searches for high-z AGN in the deepest X-ray field so far, the Chandra Deep Field South (CDFS 4 Msecond exposure. We do not confirm the positive detection of a signal in the stacked Chandra images at the position of z~6 galaxies recently reported by Treister and collaborators (2011. We present z>3 X-ray sources number counts in the 0.5–2 keV band, obtained joining CDFS faint detections (see Fiore et al. (2011, with Chandra-COSMOS and XMM-COSMOS detections. We use these number counts to make predictions for surveys with three mission concepts: Athena, WFXT, and a Super-Chandra.

  5. AGN feedback in elliptical galaxies: numerical simulations

    CERN Document Server

    Ciotti, L

    2011-01-01

    The importance of feedback (radiative and mechanical) from massive black holes at the centers of elliptical galaxies is not in doubt, given the well established relation among black hole mass and galaxy optical luminosity. Here, with the aid of high-resolution hydrodynamical simulations, we discuss how this feedback affects the hot ISM of isolated elliptical galaxies of different mass. The cooling and heating functions include photoionization plus Compton heating, the radiative transport equations are solved, and the mechanical feedback due to the nuclear wind is also described on a physical basis; star formation is considered. In the medium-high mass galaxies the resulting evolution is highly unsteady. At early times major accretion episodes caused by cooling flows in the recycled gas produced by stellar evolution trigger AGN flaring: relaxation instabilities occur so that duty cycles are small enough to account for the very small fraction of massive ellipticals observed to be in the QSO-phase, when the accr...

  6. Infrared Constraints on AGN Tori Models

    CERN Document Server

    Hatziminaoglou, E; Pérez-Fournon, I; Franceschini, A; Hernan-Caballero, A; Afonso-Luis, A; Lonsdale, C; Fang, F; Oliver, S; Rowan-Robinson, M; Shupe, D; Smith, H; Surace, J; Gonzales-Solares, E

    2006-01-01

    This work focuses on the properties of dusty tori in active galactic nuclei (AGN) derived from the comparison of SDSS type 1 quasars with mid-Infrared (MIR) counterparts and a new, detailed torus model. The infrared data were taken by the Spitzer Wide-area InfraRed Extragalactic (SWIRE) Survey. Basic model parameters are constraint, such as the density law of the graphite and silicate grains, the torus size and its opening angle. A whole variety of optical depths is supported. The favoured models are those with decreasing density with distance from the centre, while there is no clear tendency as to the covering factor, ie small, medium and large covering factors are almost equally distributed. Based on the models that better describe the observed SEDs, properties such as the accretion luminosity, the mass of dust, the inner to outer radius ratio and the hydrogen column density are computed.

  7. 电晕线串并联的脉冲电晕放电特性%Pulse Corona Discharge Characteristics of the Line-to-plate Reactor with Series and Parallel Corona Wire

    Institute of Scientific and Technical Information of China (English)

    何正浩; 李劲

    2001-01-01

    The V-A characteristics of nanosecond pulse corona discharge with different corona wire length in series and parallel in the line-to-plate pulse corona discharge reactor is measured.It investigates the different features of the pulse corona discharge while the corona wires are connected in series and parallel. It is known from the study that the V-A characteristics of nanosecond pulse corona discharge trends to rise as exponential function. The corona currents with the wire in series increase as logarithmic function with the increase of the corona wire. But the corona currents with the wire in parallel increase as linear function with the increase of the corona wire. The results suggest that the corona wires is better to be connected in parallel in practical design for getting high corona discharge efficiency and the corona wire shouldn’t be long.%在线板结构脉冲电晕放电试验模型上,测试了不同长度电晕线串并联时的ns脉冲电晕放电伏安特性,研究了电晕线串并联时脉冲电晕放电的不同特点。研究表明ns脉冲电晕放电伏安特性呈指数函数上升趋势,串联电晕线的电晕电流随其长度的增长为自然对数函数上升趋势,并联电晕线的电晕 电流随其长度的增长为线形函数上升趋势。根据研究,实际设计脉冲电晕放电反应器时,为提高反应器效率,多根电晕线应并联而不宜串联,且电晕线不宜过长。

  8. Full-Scale Continuous Mini-Reactor Setup for Heterogeneous Grignard Alkylation of a Pharmaceutical Intermediate

    DEFF Research Database (Denmark)

    Pedersen, Michael Jønch; Holm, Thomas; Rahbek, Jesper P.

    2013-01-01

    A reactor setup consisting of two reactors in series has been implemented for a full-scale, heterogeneous Grignard alkylation. Solutions pass from a small filter reactor into a static mixer reactor with multiple side entries, thus combining continuous stirred tank reactor (CSTR) and plug flow rea...

  9. Mechanical AGN Feedback: Controlling the Thermodynamical Evolution of Elliptical Galaxies

    CERN Document Server

    Gaspari, M; Temi, P

    2012-01-01

    A fundamental gap in the current understanding of galaxies concerns the thermodynamical evolution of the ordinary, baryonic matter. On one side, radiative emission drastically decreases the thermal energy content of the interstellar plasma (ISM), inducing a slow cooling flow toward the centre. On the other side, the active galactic nucleus (AGN) struggles to prevent the runaway cooling catastrophe, injecting huge amount of energy in the ISM. The present study intends to deeply investigate the role of mechanical AGN feedback in (isolated or massive) elliptical galaxies, extending and completing the mass range of tested cosmic environments. Our previously successful feedback models, in galaxy clusters and groups, demonstrated that AGN outflows, self-regulated by cold gas accretion, are able to properly quench the cooling flow, without destroying the cool core. Via 3D hydrodynamic simulations (FLASH 3.3), including also stellar evolution, we show that massive mechanical AGN outflows can indeed solve the cooling ...

  10. AGN Broad Line Regions Scale with Bolometric Luminosity

    CERN Document Server

    Trippe, Sascha

    2015-01-01

    The masses of supermassive black holes in active galactic nuclei (AGN) can be derived spectroscopically via virial mass estimators based on selected broad optical/ultraviolet emission lines. These estimates commonly use the line width as a proxy for the gas speed and the monochromatic continuum luminosity as a proxy for the radius of the broad line region. However, if the size of the broad line region scales with bolometric rather than monochromatic AGN luminosity, mass estimates based on different emission lines will show a systematic discrepancy which is a function of the color of the AGN continuum. This has actually been observed in mass estimates based on H-alpha / H-beta and C IV lines, indicating that AGN broad line regions indeed scale with bolometric luminosity. Given that this effect seems to have been overlooked as yet, currently used single-epoch mass estimates are likely to be biased.

  11. New mechanism of radiation polarization in Seyfert-1 AGNs

    CERN Document Server

    Silant'ev, N A; Piotrovich, M Yu; Natsvlishvili, T M; Buliga, S D

    2016-01-01

    In most of Seyfert-1 active galactic nucei (AGN) the optical linear continuum polarization degree is usually small (less than 1%) and the polarization position angle is nearly parallel to the AGN radio-axis. However, there are many types-1 AGNs with unexplained intermediate values for both positional angles and polarization degrees. Our explanation of polarization degree and positional angle of Seyfert-1 AGNs focuses on the reflection of non-polarized radiation from sub-parsec jets in optically thick accretion discs. The presence of a magnetic field surrounding the scattering media will induce Faraday rotation of the polarization plane that may explain the intermediate values of positional angles if there is a magnetic field component normal to the accretion disc. The Faraday rotation depolarization effect in disc diminishes the competition between polarization of the reflected radiation with the parallel component of polarization and the perpendicular polarization from internal radiation of disc (the Milne p...

  12. AGN Feedback Driven Molecular Outflow in NGC 1266

    CERN Document Server

    Alatalo, K; Graves, G; Deustua, S; Wrobel, J; Young, L M; Davis, T A; Bureau, M; Bayet, E; Blitz, L; Bois, M; Bournaud, F; Cappellari, M; Davies, R L; de Zeeuw, P T; Emsellem, E; Khochfar, S; Krajnovic, D; Kuntschner, H; Martin, S; McDermid, R M; Morganti, R; Naab, T; Oosterloo, T; Sarzi, M; Scott, N; Serra, P; Weijmans, A

    2012-01-01

    NGC 1266 is a nearby field galaxy observed as part of the ATLAS3D survey (Cappellari et al. 2011). NGC 1266 has been shown to host a compact (< 200 pc) molecular disk and a mass-loaded molecular outflow driven by the AGN (Alatalo et al. 2011). Very Long Basline Array (VLBA) observations at 1.65 GHz revealed a compact (diameter < 1.2 pc), high bright- ness temperature continuum source most consistent with a low-level AGN origin. The VLBA continuum source is positioned at the center of the molecular disk and may be responsible for the expulsion of molecular gas in NGC 1266. Thus, the candidate AGN-driven molecular outflow in NGC 1266 supports the picture in which AGNs do play a significant role in the quenching of star formation and ultimately the evolution of the red sequence of galaxies.

  13. AGN-selected clusters as revealed by weak lensing

    Science.gov (United States)

    Wold, M.; Lacy, M.; Dahle, H.; Lilje, P. B.; Ridgway, S. E.

    2002-01-01

    We discuss the results in light of the cooling flow and the merger/interaction scenarios for triggering and fuelling AGN in clusters, but find that the data do not point unambiguously to neither of the two.

  14. Simulations of Metal Enrichment in Galaxy Clusters by AGN Outflows

    CERN Document Server

    Moll, R; Domainko, W; Kapferer, W; Mair, M; Van Kampen, E; Kronberger, T; Kimeswenger, S; Ruffert, M

    2006-01-01

    We assess the importance of AGN outflows with respect to the metal enrichment of the intracluster medium (ICM) in galaxy clusters. We use combined N-body and hydrodynamic simulations, along with a semi-numerical galaxy formation and evolution model. Using assumptions based on observations, we attribute outflows of metal-rich gas initiated by AGN activity to a certain fraction of our model galaxies. The gas is added to the model ICM, where the evolution of the metallicity distribution is calculated by the hydrodynamic simulations. For the parameters describing the AGN content of clusters and their outflow properties, we use the observationally most favorable values. We find that AGNs have the potential to contribute significantly to the metal content of the ICM or even explain the complete abundance, which is typically ~0.5 Z_sun in core regions. Furthermore, the metals end up being inhomogeneously distributed, in accordance with observations.

  15. AGN feedback in clusters: shock and sound heating

    CERN Document Server

    Nulsen, P E J

    2013-01-01

    Observations support the view that feedback, in the form of radio outbursts from active nuclei in central galaxies, prevents catastrophic cooling of gas and rapid star formation in many groups and clusters of galaxies. Variations in jet power drive a succession of weak shocks that can heat regions close to the active galactic nuclei (AGN). On larger scales, shocks fade into sound waves. The Braginskii viscosity determines a well-defined sound damping rate in the weakly magnetized intracluster medium (ICM) that can provide sufficient heating on larger scales. It is argued that weak shocks and sound dissipation are the main means by which radio AGN heat the ICM, in which case, the power spectrum of AGN outbursts plays a central role in AGN feedback.

  16. A Degeneracy in DRW Modelling of AGN Light Curves

    CERN Document Server

    Kozlowski, Szymon

    2016-01-01

    Individual light curves of active galactic nuclei (AGNs) are nowadays successfully modelled with the damped random walk (DRW) stochastic process, characterized by the power exponential covariance matrix of the signal, with the power $\\beta=1$. By Monte Carlo simulation means, we generate mock AGN light curves described by non-DRW stochastic processes ($0.5\\leq\\beta\\leq 1.5$ and $\\beta\

  17. Multiwavelength Number Counts of AGN in the GOODS Fields

    Science.gov (United States)

    Urry, C. M.; Treister, E.; Chatzichristou, E. T.; Van Duyne, J.; Bauer, F. E.; Alexander, D. M.; Koekemoer, A. M.; Moustakas, L. A.; Brandt, W. N.; Grogin, N. A.; Bergeron, J.; Stern, D.; Chary, R.-R.; Conselice, C. J.; Cristiani, S.

    2004-05-01

    We model the X-ray, optical, and far-infrared flux distributions of AGN in the GOODS fields, starting from hard X-ray luminosity functions and spectral energy distributions appropriate to the unified scheme for AGN. The deep optical counts measured from HST ACS images can be well explained by a unified scheme that postulates roughly 3 times as many obscured as unobscured AGN. This scenario is consistent with the observed spectroscopic and photometric redshift distributions of the GOODS AGN once selection effects are considered. The previously reported discrepancy between observed spectroscopic redshift distributions and the predictions of population synthesis models for the X-ray background (which include a similarly large number of obscured AGN) is explained by bias against the most heavily obscured AGN in both X-ray surveys and optical spectroscopic samples. We present the model predictions for the number counts of AGN in the Spitzer MIPS 24 micron and IRAC 3.6-8 micron bands. The GOODS Spitzer observations will verify whether large numbers of obscured AGN are indeed present in the early Universe; these will be very bright far-infrared sources, including some, missed by X-ray observations, that look like ultraluminous infrared galaxies. Based on observations obtained with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc, under NASA contract NAS5-26555. This work was supported by NASA grants HST-GO-09425(.01-A,.13-A,.26-A); NSF CAREER award AST 99-83783; NASA contract number 1224666 issued by JPL/Caltech under NASA contract 1407; ASI grant I/R/088/02; and a Royal Society University Research Fellowship.

  18. Fossil AGN jets as ultra high energy particle accelerators

    OpenAIRE

    2007-01-01

    Remnants of AGN jets and their surrounding cocoons leave colossal magnetohydrodynamic (MHD) fossil structures storing total energies ~10^{60} erg. The original active galacic nucleus (AGN) may be dead but the fossil will retain its stable configuration resembling the reversed-field pinch (RFP) encountered in laboratory MHD experiments. In an RFP the longitudinal magnetic field changes direction at a critical distance from the axis, leading to magnetic re-connection there, and to slow decay of...

  19. The global properties of all variety of AGN

    CERN Document Server

    Marcha, M J M

    2004-01-01

    Active Galactic Nuclei (AGN) have been a challenging field of research for the past six decades. Nevertheless, many questions still remain unanswered today, regardless of the tremendous theoretical and technological advances. In this brief review I propose to take a step back from the usual discussion of AGN properties and draw attention to some topics that I believe are important to keep in mind as we strive forward in our pursuit of knowledge about these sources.

  20. Optical Identifications of X-ray Selected AGNs

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    For investigating the statistical properties of X-ray selected Active Galactic Nuclei (AGNs), we have carried out a program of optical identification of a selection of X-ray sources from ROSAT All Sky Survey Bright Source Catalogue (RASS-BSC) using the 2.16 m telescope of Beijing Astronomical Observatory (BAO). In the preliminary observations, 23 new AGNs were discovered, of which 9 are quasars, and 14 are Seyfert galaxies.

  1. Reactor vessel

    OpenAIRE

    Makkee, M.; Kapteijn, F.; Moulijn, J.A

    1999-01-01

    A reactor vessel (1) comprises a reactor body (2) through which channels (3) are provided whose surface comprises longitudinal inwardly directed parts (4) and is provided with a catalyst (6), as well as buffer bodies (8, 12) connected to the channels (3) on both sides of the reactor body (2) and comprising connections for supplying (9, 10, 11) and discharging (13, 14, 15) via the channels (3) gases and/or liquids entering into a reaction with each other and substances formed upon this reactio...

  2. Lyman continuum leaking AGN in the SSA22 field

    Science.gov (United States)

    Micheva, Genoveva; Iwata, Ikuru; Inoue, Akio K.

    2017-02-01

    Subaru/SuprimeCam narrowband photometry of the SSA22 field reveals the presence of four Lyman continuum (LyC) candidates among a sample of 14 AGN. Two show offsets and likely have stellar LyC in nature or are foreground contaminants. The remaining two LyC candidates are Type I AGN. We argue that the average LyC escape fraction of high redshift low luminosity AGN is not likely to be unity, as often assumed in the literature. From direct measurement we obtain the average LyC-to-UV flux density ratio and ionizing emissivity for a number of AGN classes and find it at least a factor of two lower than values obtained assuming f_esc = 1. Comparing to recent Ly{\\alpha} forest measurements, AGNs at redshift z~3 make up at most ~12% and as little as ~5% of the total ionizing budget. Our results suggest that AGNs are unlikely to dominate the ionization budget of the Universe at high redshifts.

  3. Clustering Measurements of broad-line AGNs: Review and Future

    CERN Document Server

    Krumpe, Mirko; Coil, Alison L

    2013-01-01

    Despite substantial effort, the precise physical processes that lead to the growth of super-massive black holes in the centers of galaxies are still not well understood. These phases of black hole growth are thought to be of key importance in understanding galaxy evolution. Forthcoming missions such as eROSITA, HETDEX, eBOSS, BigBOSS, LSST, and Pan-STARRS will compile by far the largest ever Active Galactic Nuclei (AGNs) catalogs which will allow us to measure the spatial distribution of AGNs in the universe with unprecedented accuracy. For the first time, AGN clustering measurements will reach a level of precision that will not only allow for an alternative approach to answering open questions in AGN/galaxy co-evolution but will open a new frontier, allowing us to precisely determine cosmological parameters. This paper reviews the large-scale clustering measurements of broad line AGNs. We summarize how clustering is measured and which constraints can be derived from AGN clustering measurements, we discuss re...

  4. A new technique to efficiently select Compton-thick AGN

    CERN Document Server

    Severgnini, P; Della Ceca, R

    2012-01-01

    We present a new efficient diagnostic method, based on mid-infrared and X-ray data, to select local (z-0.2. We build up a sample of 43 CT AGN candidates using data from IRAS-PSC and 2XMM catalogue. In order to test the efficiency of the proposed method in selecting CT AGN we use the results of the X-ray spectral analysis performed on all the sources of our sample. After taking into account the different selection effects, we have estimated the number of CT in the local Universe and their density down to the IRAS flux limit of F25=0.5Jy. We find that the diagnostic plot proposed here is an efficient method to select Compton-thick AGN in the nearby Universe since ~84% of the sources populating the proposed CT region are actually CT AGN. Twenty percent are newly-discovered CT AGN. We then estimate the surface density of CT AGN down to the IRAS PSC catalogue flux limit (F25=0.5Jy) that turns out to be ~3e-3 src deg-2. After estimating an equivalent IR-hard X-ray limiting flux, we compare our result with those fou...

  5. Mini-Survey Of SDSS of [OIII] AGN With Swift

    Science.gov (United States)

    Angelini, L.; George, I. M.; Hill, J.; Padgett, C. A.; Mushotzky, R. F.

    2008-01-01

    The number of AGN and their luminosity distribution are crucial parameters for our understanding of the AGN phenomenon. Recent work (e.g. Ferrarese and Merritt 2000) strongly suggests every massive galaxy has a central black hole. However, most of these objects either are not radiating or have been very difficult to detect. We are now in the era of large surveys, and the luminosity function (LF) of AGN has been estimated in various ways. In the X-ray band, Chandra and XMM surveys (e.g., Barger et al. 2005; Hasinger, et al. 2005) have revealed that the LF of Hard X-ray selected AGN shows a strong luminosity-dependent evolution with a dramatic break towards low L(x) (at al z). This is seen for all types of AGN, but is stronger for the broad-line objects (e.g., Steffen et al. 2004). In sharp contrast, the local LF of optically-selected samples shows no such break and no differences between narrow and broad-line objects (Hao et al. 2005). If, as been suggested, hard X-ray and optical emission line can both be fair indicators of AGN activity, it is important to first understand how reliable these characteristics are if we hope to understand the apparent discrepancy in the LFs.

  6. The INTEGRAL/IBIS AGN catalogue: an update

    CERN Document Server

    Malizia, A; Molina, M; Bassani, L; Bazzano, A; Bird, A J; Ubertini, P

    2016-01-01

    In the most recent IBIS survey based on observations performed during the first 1000 orbits of INTEGRAL, are listed 363 high energy emitters firmly associated with AGN, 107 of which are reported here for the first time. We have used X-ray data to image the IBIS 90\\% error circle of all the AGN in the sample of 107, in order to obtain the correct X-ray counterparts, locate them with arcsec accuracy and therefore pinpoint the correct optical counterparts. This procedure has led to the optical and spectral characterization of the entire sample. This new set consists of 34 broad line or type 1 AGN, 47 narrow line or type 2 AGN, 18 Blazars and 8 sources of unknown class. These 8 sources have been associated with AGN from their positional coincidence with 2MASX/Radio/X-ray sources. Seven high energy emitters have been included since they are considered to be good AGN candidates. Spectral analysis has been already performed on 55 objects and the results from the most recent and/or best statistical measurements have ...

  7. The Star Formation and AGN luminosity relation: Predictions from a semi-analytical model

    CERN Document Server

    Gutcke, Thales A; Maccio`, Andrea V; Lacey, Cedric

    2015-01-01

    In a Universe where AGN feedback regulates star formation in massive galaxies, a strong correlation between these two quantities is expected. If the gas causing star formation is also responsible for feeding the central black hole, then a positive correlation is expected. If powerful AGNs are responsible for the star formation quenching, then a negative correlation is expected. Observations so far have mainly found a mild correlation or no correlation at all (i.e. a flat relation between star formation rate (SFR) and AGN luminosity), raising questions about the whole paradigm of "AGN feedback". In this paper, we report the predictions of the GALFORM semi-analytical model, which has a very strong coupling between AGN activity and quenching of star formation. The predicted SFR-AGN luminosity correlation appears negative in the low AGN luminosity regime, where AGN feedback acts, but becomes strongly positive in the regime of the brightest AGN. Our predictions reproduce reasonably well recent observations by Rosa...

  8. NUCLEAR REACTOR

    Science.gov (United States)

    Miller, H.I.; Smith, R.C.

    1958-01-21

    This patent relates to nuclear reactors of the type which use a liquid fuel, such as a solution of uranyl sulfate in ordinary water which acts as the moderator. The reactor is comprised of a spherical vessel having a diameter of about 12 inches substantially surrounded by a reflector of beryllium oxide. Conventionnl control rods and safety rods are operated in slots in the reflector outside the vessel to control the operation of the reactor. An additional means for increasing the safety factor of the reactor by raising the ratio of delayed neutrons to prompt neutrons, is provided and consists of a soluble sulfate salt of beryllium dissolved in the liquid fuel in the proper proportion to obtain the result desired.

  9. Reactor Neutrinos

    Directory of Open Access Journals (Sweden)

    Soo-Bong Kim

    2013-01-01

    Full Text Available We review the status and the results of reactor neutrino experiments. Short-baseline experiments have provided the measurement of the reactor neutrino spectrum, and their interest has been recently revived by the discovery of the reactor antineutrino anomaly, a discrepancy between the reactor neutrino flux state of the art prediction and the measurements at baselines shorter than one kilometer. Middle and long-baseline oscillation experiments at Daya Bay, Double Chooz, and RENO provided very recently the most precise determination of the neutrino mixing angle θ13. This paper provides an overview of the upcoming experiments and of the projects under development, including the determination of the neutrino mass hierarchy and the possible use of neutrinos for society, for nonproliferation of nuclear materials, and geophysics.

  10. Chemical Reactors.

    Science.gov (United States)

    Kenney, C. N.

    1980-01-01

    Describes a course, including content, reading list, and presentation on chemical reactors at Cambridge University, England. A brief comparison of chemical engineering education between the United States and England is also given. (JN)

  11. The XXL Survey. XII. Optical spectroscopy of X-ray-selected clusters and the frequency of AGN in superclusters

    Science.gov (United States)

    Koulouridis, E.; Poggianti, B.; Altieri, B.; Valtchanov, I.; Jaffé, Y.; Adami, C.; Elyiv, A.; Melnyk, O.; Fotopoulou, S.; Gastaldello, F.; Horellou, C.; Pierre, M.; Pacaud, F.; Plionis, M.; Sadibekova, T.; Surdej, J.

    2016-06-01

    Context. This article belongs to the first series of XXL publications. It presents multifibre spectroscopic observations of three 0.55 deg2 fields in the XXL Survey, which were selected on the basis of their high density of X-ray-detected clusters. The observations were obtained with the AutoFib2+WYFFOS (AF2) wide-field fibre spectrograph mounted on the 4.2 m William Herschel Telescope. Aims: The paper first describes the scientific rationale, the preparation, the data reduction, and the results of the observations, and then presents a study of active galactic nuclei (AGN) within three superclusters. Methods: To determine the redshift of galaxy clusters and AGN, we assign high priority to a) the brightest cluster galaxies (BCGs), b) the most probable cluster galaxy candidates, and c) the optical counterparts of X-ray point-like sources. We use the outcome of the observations to study the projected (2D) and the spatial (3D) overdensity of AGN in three superclusters. Results: We obtained redshifts for 455 galaxies in total, 56 of which are counterparts of X-ray point-like sources. We were able to determine the redshift of the merging supercluster XLSSC-e, which consists of six individual clusters at z ~ 0.43, and we confirmed the redshift of supercluster XLSSC-d at z ~ 0.3. More importantly, we discovered a new supercluster, XLSSC-f, that comprises three galaxy clusters also at z ~ 0.3. We find a significant 2D overdensity of X-ray point-like sources only around the supercluster XLSSC-f. This result is also supported by the spatial (3D) analysis of XLSSC-f, where we find four AGN with compatible spectroscopic redshifts and possibly one more with compatible photometric redshift. In addition, we find two AGN (3D analysis) at the redshift of XLSSC-e, but no AGN in XLSSC-d. Comparing these findings with the optical galaxy overdensity we conclude that the total number of AGN in the area of the three superclusters significantly exceeds the field expectations. All of the

  12. Reactor Neutrinos

    OpenAIRE

    Lasserre, T.; Sobel, H.W.

    2005-01-01

    We review the status and the results of reactor neutrino experiments, that toe the cutting edge of neutrino research. Short baseline experiments have provided the measurement of the reactor neutrino spectrum, and are still searching for important phenomena such as the neutrino magnetic moment. They could open the door to the measurement of coherent neutrino scattering in a near future. Middle and long baseline oscillation experiments at Chooz and KamLAND have played a relevant role in neutrin...

  13. Nuclear Technology Series. Course 8: Reactor Safety.

    Science.gov (United States)

    Center for Occupational Research and Development, Inc., Waco, TX.

    This technical specialty course is one of thirty-five courses designed for use by two-year postsecondary institutians in five nuclear technician curriculum areas: (1) radiation protection technician, (2) nuclear instrumentation and control technician, (3) nuclear materials processing technician, (4) nuclear quality-assurance/quality-control…

  14. Mini Survey of SDSS [OIII] AGN with Swift: Testing the Hypothesis that L(sub [OIII]) Traces AGN Luminosity

    Science.gov (United States)

    2007-01-01

    The number of AGN and their luminosity distribution are crucial parameters for our understanding of the AGN phenomenon. Recent work strongly suggests every massive galaxy has a central black hole. However most of these objects either are not radiating or have been very difficult to detect We are now in the era of large surveys, and the luminosity function (LF] of AGN has been estimated in various ways. In the X-ray band. Chandra and XMM surveys have revealed that the LF of hard X-ray selected AGN shows a strong luminosity-dependent evolution with a dramatic break towards low L(sub x) (at all z). This is seen for all types of AGN, but is stronger for the broad-line objects. In sharp contrast, the local LF of optically-selected samples shows no such break and no differences between narrow and broad-line objects. If as been suggested, hard X ray and optical emission line can both can be fair indicators of AGN activity, it is important to first understand how reliable these characteristics are if we hope to understand the apparent discrepancy in the LFs.

  15. The Role of Star-Formation and AGN in Dust Heating of z=0.3-2.8 Galaxies - II. Informing IR AGN fraction estimates through simulations

    CERN Document Server

    Roebuck, Eric; Hayward, Christopher C; Pope, Alexandra; Kirkpatrick, Allison; Hernquist, Lars; Yan, Lin

    2016-01-01

    A key question in extragalactic studies is the determination of the relative roles of stars and AGN in powering dusty galaxies at $z\\sim$1-3 where the bulk of star-formation and AGN activity took place. In Paper I, we present a sample of $336$ 24$\\mu$m-selected (Ultra)Luminous Infrared Galaxies, (U)LIRGs, at $z \\sim 0.3$-$2.8$, where we focus on determining the AGN contribution to the IR luminosity. Here, we use hydrodynamic simulations with dust radiative transfer of isolated and merging galaxies, to investigate how well the simulations reproduce our empirical IR AGN fraction estimates and determine how IR AGN fractions relate to the UV-mm AGN fraction. We find that: 1) IR AGN fraction estimates based on simulations are in qualitative agreement with the empirical values when host reprocessing of the AGN light is considered; 2) for star-forming galaxy-AGN composites our empirical methods may be underestimating the role of AGN, as our simulations imply $>$50% AGN fractions, $\\sim$3$\\times$ higher than previous...

  16. Infrared Constrains on AGN Tori Models

    CERN Document Server

    Hatziminaoglou, E

    2006-01-01

    This work focuses on the properties of dusty tori in active galactic nuclei (AGN) derived from the comparison of SDSS type 1 quasars with mid-Infrared (MIR) counterparts and a new, detailed torus model. The infrared data were taken by the Spitzer Wide-area InfraRed Extragalactic (SWIRE) Survey. Basic model parameters are constraint, such as the density law of the graphite and silicate grains, the torus size and its opening angle. A whole variety of optical depths is supported. The favoured models are those with decreasing density with distance from the centre, while there is no clear tendency as to the covering factor, i.e. small, medium and large covering factors are almost equally distributed. Based on the models that better describe the observed SEDs, properties such as the accretion luminosity, the mass of dust, the inner to outer radius ratio and the hydrogen column density are computed. The properties of the tori, as derived fitting the observed SEDs, are independent of the redshift, once observational ...

  17. Gravitational microlensing of AGN dusty tori

    CERN Document Server

    Stalevski, Marko; Popovic, Luka C; Baes, Maarten

    2012-01-01

    We investigated gravitational microlensing of AGN dusty tori in the case of lensed quasars in the infrared domain. The dusty torus is modeled as a clumpy two-phase medium. To obtain spectral energy distributions and images of tori at different wavelengths, we used the 3D Monte Carlo radiative transfer code SKIRT. A ray-shooting technique has been used to calculate microlensing magnification maps. We simulated microlensing by the stars in the lens galaxy for different configurations of the lensed system and different values of the torus parameters, in order to estimate (a) amplitudes and timescales of high magnification events, and (b) the influence of geometrical and physical properties of dusty tori on light curves in the infrared domain. We found that, despite their large size, dusty tori could be significantly affected by microlensing in some cases, especially in the near-infrared domain (rest-frame). The very long timescales of such events, in the range from several decades to hundreds of years, are limit...

  18. Starbursts and agn fueling through secular evolution

    Directory of Open Access Journals (Sweden)

    F. Combes

    2006-01-01

    Full Text Available Excepto en los casos m as extremos de actividad nuclear, ya sea explosi on de formaci on estelar o AGN, es dif cil encontrar de manera observacional una estrecha relaci on entre la din amica y la actividad. De manera te orica, sin embargo, el paso necesario para aprovisionar de gas al centro es que las torcas de gravedad se creen mediante un patr on no axisim etrico, ya sea de barra y/o espiral, provocado o no por una interacci on de marea. Describimos la secuencia de los procesos de un ciclo t pico de evoluci on para una galaxia espiral, y los posibles mecanismos e cientes de retroalimentaci on. Las diversas morfolog as y estados din amicos de galaxias espirales son interpretados en t erminos de una secuencia de fases evolutivas, y las escalas temporales correspondientes se pueden estimar de observaciones. En este escenario, la actividad en las galaxias est a relacionada con la apariencia de la inestabilidad de la barra, aunque sus fases no est en sincronizadas. Se discute el papel de la acreci on externa de gas en la evoluci on secular.

  19. Radio-Loud AGN: The Suzaku View

    Science.gov (United States)

    Sambruna, Rita

    2009-01-01

    We review our Suzaku observations of Broad-Line Radio Galaxies (BLRGs). The continuum above 2 approx.keV in BLRGs is dominated by emission from an accretion flow, with little or no trace of a jet, which is instead expected to emerge at GeV energies and be detected by Fermi. Concerning the physical conditions of the accretion disk, BLRGs are a mixed bag. In some sources the data suggest relatively high disk ionization, in others obscuration of the innermost regions, perhaps by the jet base. While at hard X-rays the distinction between BLRGs and Seyferts appears blurry, one of the cleanest observational differences between the two classes is at soft X-rays, where Seyferts exhibit warm absorbers related to disk winds while BLRGs do not. We discuss the possibility that jet formation inhibits disk winds, and thus is related to the remarkable dearth of absorption features at soft X-rays in BLRGs and other radio-loud AGN.

  20. Coronal-Line Forest AGN: the best view of the inner edge of the AGN torus?

    CERN Document Server

    Rose, Marvin; Tadhunter, Clive

    2015-01-01

    We introduce Coronal-Line Forest Active Galactic Nuclei (CLiF AGN), AGN which have a rich spectrum of forbidden high-ionization lines (FHILs, e.g. [FeVII], [FeX] and [NeV]), as well as relatively strong narrow ($\\sim$300 km s$^{-1}$) H$\\alpha$ emission when compared to the other Balmer transition lines. We find that the kinematics of the CLiF emitting region are similar to those of the forbidden low-ionization emission-line (FLIL) region. We compare emission line strengths of both FHILs and FLILs to CLOUDY photoionization results and find that the CLiF emitting region has higher densities (10$^{4.5}$ $<$ n$_H$ $<$ 10$^{7.5}$ cm$^{-3}$) when compared to the FLIL emitting region (10$^{3.0}$ $<$ n$_H$ $<$ 10$^{4.5}$ cm$^{-3}$). We use the photoionization results to calculate the CLiF regions radial distances (0.04 $<$ R$_{CLiF}$ $<$ 32.5 pc) and find that they are comparable to the dust grain sublimation distances (0.10 $<$ R$_{SUB}$ $<$ 4.3 pc). As a result we suggest that the inner toru...

  1. Utilization of AGN-201K for Education and Research in Korea

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Myung-Hyun [Department of Nuclear Engineering, Kyung Hee University, KHU Reactor Research and Education Center, Kiheung, Yongin, Gyeonggi-do, 446-701 (Korea, Republic of)

    2011-07-01

    A zero power reactor, AGN-201K has been operated in Kyung Hee University since 1982 and it was refurbished extensively three years ago. In 2008, Reactor Research and Education Center (RREC) was established for student training and research. The primary mission of RREC is an educational service for nuclear engineering students. Since January 2009, short courses were provided 15 times to 160 students from 7 universities. This course has been an one-week dormitory housing program in the name of Reactor Experiment and was designed as an advanced course customized to undergraduate senior-level. It has introductory session, safety guide session, concluding presentation session with six experiment sessions; reactor operation and control, measurement of period for reactivity, criticality approach, rod worth measurement, measurement of temperature feedback coefficient and thermal flux measurement with neutron activation analysis (NAA). As a R and D effort for future experimental courses, RREC is now seeking for the possibility of reactor utilization for prompt gamma activation analysis, NAA for material mass spectroscopy, and neutron radiography (NR). A feasibility study on NR was done with MCNP simulation on collimator design and showed that calculated thermal flux level was high enough at the object position even though image size is very small, less than 4 cm diameter. Research activity has been done for sub-criticality measurement with modified neutron source multiplication method (MNSM). For sub-criticality evaluation with this method, three kinds of the neutron flux distributions such as forward, adjoint, fixed source neutron fluxes, which are solution in both eigenvalue and fixed source problems are needed. These flux distributions were calculated by using PARTISN code systems. Physics conditions are highly dependent on the source locations and rod positions as well as detector positions. Recent results showed that this method improved accuracy in rod worth

  2. CHARACTERIZATION OF A SAMPLE OF INTERMEDIATE-TYPE AGNs. I. SPECTROSCOPIC PROPERTIES AND SERENDIPITOUS DISCOVERY OF NEW DUAL AGNs

    Energy Technology Data Exchange (ETDEWEB)

    Benitez, Erika; Cruz-Gonzalez, Irene; Martinez, Benoni; Jimenez-Bailon, Elena [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Apdo. Postal 70-264, Mexico D.F. 04510 (Mexico); Mendez-Abreu, Jairo; Lopez-Martin, Luis [Instituto de Astrofisica de Canarias, E-38200 La Laguna, Tenerife (Spain); Fuentes-Carrera, Isaura [Escuela Superior de Fisica y Matematicas, Instituto Politecnico Nacional (ESFM-IPN), U.P. Adolfo Lopez Mateos, Mexico D.F. 07730 (Mexico); Leon-Tavares, Jonathan [Aalto University Metsaehovi Radio Observatory, Metsaehovintie 114, FI-02540, Kylmaelae (Finland); Chavushyan, Vahram H., E-mail: erika@astro.unam.mx [Instituto Nacional de Astrofisica, Optica y Electronica, Apdo. Postal 51-216, 72000 Puebla (Mexico)

    2013-01-20

    A sample of 10 nearby intermediate-type active galactic nuclei (AGNs) drawn from the Sloan Digital Sky Survey is presented. The aim of this work is to provide estimations of the black hole (BH) mass for the sample galaxies from the dynamics of the broad-line region. For this purpose, a detailed spectroscopic analysis of the objects was done. Using Baldwin-Phillips-Terlevich diagnostic diagrams, we have carefully classified the objects as true intermediate-type AGNs and found that 80%{sup +7.2%} {sub -17.3%} are composite AGNs. The BH mass estimated for the sample is within 6.54 {+-} 0.16 < log M {sub BH} < 7.81 {+-} 0.14. Profile analysis shows that five objects (J120655.63+501737.1, J121607.08+504930.0, J141238.14+391836.5, J143031.18+524225.8, and J162952.88+242638.3) have narrow double-peaked emission lines in both the red (H{alpha}, [N II] {lambda}{lambda}6548,6583 and [S II] {lambda}{lambda}6716, 6731) and the blue (H{beta} and [O III] {lambda}{lambda}4959, 5007) regions of the spectra, with velocity differences ({Delta}V) between the double peaks within 114 km s{sup -1} < {Delta}V < 256 km s{sup -1}. Two of them, J121607.08+504930.0 and J141238.14+391836.5, are candidates for dual AGNs since their double-peaked emission lines are dominated by AGN activity. In searches of dual AGNs, type 1, type II, and intermediate-type AGNs should be carefully separated, due to the high serendipitous number of narrow double-peaked sources (50% {+-} 14.4%) found in our sample.

  3. AGN host galaxy mass function in COSMOS. Is AGN feedback responsible for the mass-quenching of galaxies?

    Science.gov (United States)

    Bongiorno, A.; Schulze, A.; Merloni, A.; Zamorani, G.; Ilbert, O.; La Franca, F.; Peng, Y.; Piconcelli, E.; Mainieri, V.; Silverman, J. D.; Brusa, M.; Fiore, F.; Salvato, M.; Scoville, N.

    2016-04-01

    We investigate the role of supermassive black holes in the global context of galaxy evolution by measuring the host galaxy stellar mass function (HGMF) and the specific accretion rate, that is, λSAR, the distribution function (SARDF), up to z ~ 2.5 with ~1000 X-ray selected AGN from XMM-COSMOS. Using a maximum likelihood approach, we jointly fit the stellar mass function and specific accretion rate distribution function, with the X-ray luminosity function as an additional constraint. Our best-fit model characterizes the SARDF as a double power-law with mass-dependent but redshift-independent break, whose low λSAR slope flattens with increasing redshift while the normalization increases. This implies that for a given stellar mass, higher λSAR objects have a peak in their space density at earlier epoch than the lower λSAR objects, following and mimicking the well-known AGN cosmic downsizing as observed in the AGN luminosity function. The mass function of active galaxies is described by a Schechter function with an almost constant M∗⋆ and a low-mass slope α that flattens with redshift. Compared to the stellar mass function, we find that the HGMF has a similar shape and that up to log (M⋆/M⊙) ~ 11.5, the ratio of AGN host galaxies to star-forming galaxies is basically constant (~10%). Finally, the comparison of the AGN HGMF for different luminosity and specific accretion rate subclasses with a previously published phenomenological model prediction for the "transient" population, which are galaxies in the process of being mass-quenched, reveals that low-luminosity AGN do not appear to be able to contribute significantly to the quenching and that at least at high masses, that is, M⋆ > 1010.7 M⊙, feedback from luminous AGN (log Lbol ≳ 46 [erg/s]) may be responsible for the quenching of star formation in the host galaxy.

  4. Average Heating Rate of Hot Atmospheres in Distant Galaxy Clusters by Radio AGN: Evidence for Continuous AGN Heating

    Science.gov (United States)

    Ma, Cheng-Jiun; McNamara, B.; Nulsen, P.; Schaffer, R.

    2011-09-01

    X-ray observations of nearby clusters and galaxies have shown that energetic feedback from AGN is heating hot atmospheres and is probably the principal agent that is offsetting cooling flows. Here we examine AGN heating in distant X-ray clusters by cross correlating clusters selected from the 400 Square Degree X-ray Cluster survey with radio sources in the NRAO VLA Sky Survey. The jet power for each radio source was determined using scaling relations between radio power and cavity power determined for nearby clusters, groups, and galaxies with atmospheres containing X-ray cavities. Roughly 30% of the clusters show radio emission above a flux threshold of 3 mJy within the central 250 kpc that is presumably associated with the brightest cluster galaxy. We find no significant correlation between radio power, hence jet power, and the X-ray luminosities of clusters in redshift range 0.1 -- 0.6. The detection frequency of radio AGN is inconsistent with the presence of strong cooling flows in 400SD, but cannot rule out the presence of weak cooling flows. The average jet power of central radio AGN is approximately 2 10^{44} erg/s. The jet power corresponds to an average heating of approximately 0.2 keV/particle for gas within R_500. Assuming the current AGN heating rate remained constant out to redshifts of about 2, these figures would rise by a factor of two. Our results show that the integrated energy injected from radio AGN outbursts in clusters is statistically significant compared to the excess entropy in hot atmospheres that is required for the breaking of self-similarity in cluster scaling relations. It is not clear that central AGN in 400SD clusters are maintained by a self-regulated feedback loop at the base of a cooling flow. However, they may play a significant role in preventing the development of strong cooling flows at early epochs.

  5. Inverse Compton X-ray signature of AGN feedback

    Science.gov (United States)

    Bourne, Martin A.; Nayakshin, Sergei

    2013-12-01

    Bright AGN frequently show ultrafast outflows (UFOs) with outflow velocities vout ˜ 0.1c. These outflows may be the source of AGN feedback on their host galaxies sought by galaxy formation modellers. The exact effect of the outflows on the ambient galaxy gas strongly depends on whether the shocked UFOs cool rapidly or not. This in turn depends on whether the shocked electrons share the same temperature as ions (one-temperature regime, 1T) or decouple (2T), as has been recently suggested. Here we calculate the inverse Compton spectrum emitted by such shocks, finding a broad feature potentially detectable either in mid-to-high energy X-rays (1T case) or only in the soft X-rays (2T). We argue that current observations of AGN do not seem to show evidence for the 1T component. The limits on the 2T emission are far weaker, and in fact it is possible that the observed soft X-ray excess of AGN is partially or fully due to the 2T shock emission. This suggests that UFOs are in the energy-driven regime outside the central few pc, and must pump considerable amounts of not only momentum but also energy into the ambient gas. We encourage X-ray observers to look for the inverse Compton components calculated here in order to constrain AGN feedback models further.

  6. Disentangling AGN and Star Formation in Soft X-rays

    CERN Document Server

    LaMassa, Stephanie M; Ptak, A

    2012-01-01

    We have explored the interplay of star formation and AGN activity in soft X-rays (0.5-2 keV) in two samples of Seyfert 2 galaxies (Sy2s). Using a combination of low resolution CCD spectra from Chandra and XMM-Newton, we modeled the soft emission of 34 Sy2s using power law and thermal models. For the 11 sources with high signal-to-noise Chandra imaging of the diffuse host galaxy emission, we estimate the luminosity due to star formation by removing the AGN, fitting the residual emission. The AGN and star formation contributions to the soft X-ray luminosity (i.e. L$_{x,AGN}$ and L$_{x,SF}$) for the remaining 24 Sy2s were estimated from the power law and thermal luminosities derived from spectral fitting. These luminosities were scaled based on a template derived from XSINGS analysis of normal star forming galaxies. To account for errors in the luminosities derived from spectral fitting and the spread in the scaling factor, we estimated L$_{x,AGN}$ and L$_{x,SF}$ from Monte Carlo simulations. These simulated lum...

  7. Lyman continuum leaking AGN in the SSA22 field

    CERN Document Server

    Micheva, Genoveva; Inoue, Akio K

    2016-01-01

    Subaru/SuprimeCam narrowband photometry of the SSA22 field reveals the presence of four Lyman continuum (LyC) candidates among a sample of 14 AGN. Two show offsets and likely have stellar LyC in nature or are foreground contaminants. The remaining two LyC candidates are Type I AGN. We argue that the average LyC escape fraction of high redshift quasars is not likely to be unity, as often assumed in the literature. From direct measurement we obtain the average LyC-to-UV flux density ratio and ionizing emissivity for a number of AGN classes and find it at least a factor of two lower than values obtained assuming f_esc = 1. Comparing to recent Ly{\\alpha} forest measurements, AGNs at redshift z\\sim3 make up at most \\sim20% and as little as 3% of the total ionizing budget. Our results suggest that AGNs are unlikely to dominate the ionization budget of the Universe at high redshifts.

  8. Interpreting the Ionization Sequence in AGN Emission-Line Spectra

    CERN Document Server

    Richardson, Chris T; Baldwin, Jack A; Hewett, Paul C; Ferland, Gary J

    2013-01-01

    We investigate the physical cause of the great range in the ionization level seen in the spectra of narrow lined active galactic nuclei (AGN). Mean field independent component analysis identifies examples of individual SDSS galaxies whose spectra are not dominated by emission due to star formation (SF), which we designate as AGN. We assembled high S/N ratio composite spectra of a sequence of these AGN defined by the ionization level of their narrow-line regions (NLR), extending down to very low-ionization cases. We used a local optimally emitting cloud (LOC) model to fit emission-line ratios in this AGN sequence. These included the weak lines that can be measured only in the co-added spectra, providing consistency checks on strong line diagnostics. After integrating over a wide range of radii and densities our models indicate that the radial extent of the NLR is the major parameter in determining the position of high to moderate ionization AGN along our sequence, providing a physical interpretation for their ...

  9. Mini-Survey of SDSS OIII AGN with Swift

    Science.gov (United States)

    Angelina, Lorella; George, Ian

    2007-01-01

    There is a common wisdom that every massive galaxy has a massive block hole. However, most of these objects either are not radiating or until recently have been very difficult to detect. The Sloan Digital Sky Survey (SDSS) data, based on the [OIII] line indicate that perhaps up to 20% of all galaxies may be classified as AGN a surprising result that must be checked with independent data. X-ray surveys have revealed that hard X-ray selected AGN show a strong luminosity dependent evolution and their luminosity function (LF) shows a dramatic break towards low Lx (at all z). This is seen for all types of AGN, but is stronger for the broad-line objects. In sharp contrast, the local LF of (optically-selected samples) shows no such break and no differences between narrow and broad-line objects. Assuming both hard X-ray and [OIII] emission are fair indicators of AGN activity, it is important to understand this discrepancy. We present here the results of a mini-survey done with Swift on a selected sample of SDSS selected AGN. The objects have been sampled at different L([OIII]) to check the relation with the Lx observed with Swift.

  10. Application of The Real_time Swiss Permanent GPS Network 'agnes'

    Science.gov (United States)

    Brockmann, E.; Grünig, S.; Hug, R.; Schneider, D.; Wiget, A.; Wild, U.

    The Swiss Federal Office of Topography (S+T) has been building up and operating an automated GPS network for Switzer-land (AGNES) since 1998. The final ex- pansion of 29 permanently operating GPS tracking stations was reached at the end of 2001. AGNES is a multipurpose network serving scien-tific applications (geody- namics and atmospheric research) as well as surveying applications (ref-erence frame maintenance, densification of the reference frame). In addition, a positioning service is offered on a commercial basis under the pro-duct name swipos-GIS/GEO (Swiss Positioning Service for GIS and Geodetic Applications). The paper focuses on the different applications and the results achieved so far. In the field of geody- namics, results of a kinematic model of the tectonic movements in the Swiss Alps derived from GPS time series will be shown. Since end of 2001 the S+T contributes hourly zenith path delay estimates with a time delay of 1:15 hours to the European COST-716 project and to MeteoSwiss as additional information for numerical weather prediction. Furthermore results of the high-precision real-time positioning service swipos-GIS/GEO (accuracy 0.01-0.1m) using the GSM technique for broadcasting differ-ential corrections are presented with the focus on improving the performance (ambiguity initialization, coordinate repeatability) by using the virtual reference sta- tion concept.

  11. On the Importance of Very-light Internally-subsonic AGN Jets in Radio-mode AGN Feedback

    CERN Document Server

    Guo, Fulai

    2016-01-01

    Radio-mode active galactic nucleus (AGN) feedback plays a key role in the evolution of galaxy groups and clusters. Its physical origin lies in the kpc-scale interaction of AGN jets with the hot halo gas, where jet properties may play an important role. Large-scale jet simulations often initiate light internally-supersonic jets with density contrast $0.01<\\eta<1$. Here we argue for the importance of very-light ($\\eta<0.01$) internally-subsonic jets in AGN feedback. We investigated the shapes of young X-ray cavities produced by AGN jets in a suite of hydrodynamic simulations, and found that bottom-wide cavities are always produced by internally-subsonic jets, while internally-supersonic jets produce cylindrical, center-wide, or top-wide cavities. We found examples of real cavities inflated by internally-subsonic and internally-supersonic jets, suggesting a dichotomy of AGN jets according to their internal Mach numbers. We further studied the long-term cavity evolution, and found that old cavities resul...

  12. BAT AGN Spectroscopic Survey - III. An observed link between AGN Eddington ratio and narrow-emission-line ratios

    Science.gov (United States)

    Oh, Kyuseok; Schawinski, Kevin; Koss, Michael; Trakhtenbrot, Benny; Lamperti, Isabella; Ricci, Claudio; Mushotzky, Richard; Veilleux, Sylvain; Berney, Simon; Crenshaw, D. Michael; Gehrels, Neil; Harrison, Fiona; Masetti, Nicola; Soto, Kurt T.; Stern, Daniel; Treister, Ezequiel; Ueda, Yoshihiro

    2017-01-01

    We investigate the observed relationship between black hole mass (MBH), bolometric luminosity (Lbol) and Eddington ratio (λEdd) with optical emission-line ratios ([N II] λ6583/Hα, [S II] λλ6716, 6731/Hα, [O I] λ6300/Hα, [O III] λ5007/Hβ, [Ne III] λ3869/Hβ and He II λ4686/Hβ) of hard X-ray-selected active galactic nuclei (AGN) from the BAT AGN Spectroscopic Survey. We show that the [N II] λ6583/Hα ratio exhibits a significant correlation with λEdd (RPear = -0.44, p-value = 3 × 10-13, σ = 0.28 dex), and the correlation is not solely driven by MBH or Lbol. The observed correlation between [N II] λ6583/Hα ratio and MBH is stronger than the correlation with Lbol, but both are weaker than the λEdd correlation. This implies that the large-scale narrow lines of AGN host galaxies carry information about the accretion state of the AGN central engine. We propose that [N II] λ6583/Hα is a useful indicator of Eddington ratio with 0.6 dex of rms scatter, and that it can be used to measure λEdd and thus MBH from the measured Lbol, even for high-redshift obscured AGN. We briefly discuss possible physical mechanisms behind this correlation, such as the mass-metallicity relation, X-ray heating, and radiatively driven outflows.

  13. Simulations of cosmic ray feedback by AGN in galaxy clusters

    CERN Document Server

    Sijacki, D; Springel, V; Ensslin, T A

    2008-01-01

    We investigate a numerical model for AGN feedback where for the first time a relativistic particle population in AGN-inflated bubbles is followed within a full cosmological context. In our high-resolution simulations of galaxy cluster formation, we assume that BH accretion is accompanied by energy feedback that occurs in two different modes, depending on the accretion rate itself. Unlike in previous work, we inject a non-thermal particle population of relativistic protons into the AGN bubbles, instead of adopting a purely thermal heating. We then follow the subsequent evolution of the cosmic ray (CR) plasma inside the bubbles, considering both its hydrodynamical interactions and dissipation processes relevant for the CR population. Due to the different buoyancy of relativistic plasma and the comparatively long CR dissipation timescale we find substantial changes in the evolution of clusters as a result of CR feedback. In particular, the non-thermal population can provide significant pressure support in centra...

  14. Do Some AGN Lack X-ray Emission?

    CERN Document Server

    Simmonds, Charlotte; Thuan, Trinh X; Izotov, Yuri I; Stern, Daniel; Harrison, Fiona A

    2016-01-01

    $Context:$ Intermediate-Mass Black Holes (IMBHs) are thought to be the seeds of early Supermassive Black Holes (SMBHs). While $\\gtrsim$100 IMBH and small SMBH candidates have been identified in recent years, few have been robustly confirmed to date, leaving their number density in considerable doubt. Placing firmer constraints both on the methods used to identify and confirm IMBHs/SMBHs, as well as characterizing the range of host environments that IMBHs/SMBHs likely inhabit is therefore of considerable interest and importance. Additionally, finding significant numbers of IMBHs in metal-poor systems would be particularly intriguing, since such systems may represent local analogs of primordial galaxies, and therefore could provide clues of early accretion processes. $Aims:$ Here we study in detail several candidate Active Galactic Nuclei (AGN) found in metal-poor hosts. $Methods:$ We utilize new X-ray and optical observations to characterize these metal-poor AGN candidates and compare them against known AGN lu...

  15. The central parsecs of AGN across the electromagnetic spectrum

    Science.gov (United States)

    Prieto, Almudena

    2016-08-01

    High angular resolution observations across the electromagnetic spectrum of the nearest AGN are providing a view of the nuclear region rather different from- and somewhat simpler than-the one envisaged by the canonical AGN Unification Schemes. I will review the challenges that parsec-scale observations in the IR when combined with comparable physical scales in radio, millimetre, optical, UV and X-ray of some of the nearest AGN are revealing about the nature of the nuclear emission, the transition from the most luminous to the feeble ones, and their accretion power. I will discuss how these observations challenge the requirement of a torus and question one of its fundamental attributes which is the collimation of the nuclear radiation.

  16. Exploring AGN Activity over Cosmic Time with the SKA

    CERN Document Server

    Smolcic, Vernesa; Delhaize, Jacinta; Prandoni, Isabella; Seymour, Nicholas; Jarvis, Matt; Afonso, Jose; Magliocchetti, Manuela; Huynh, Minh; Vaccari, Mattia; Karim, Alexander

    2015-01-01

    In this Chapter we present the motivation for undertaking both a wide and deep survey with the SKA in the context of studying AGN activity across cosmic time. With an rms down to 1 $\\mu$Jy/beam at 1 GHz over 1,000 - 5,000 deg$^2$ in 1 year (wide tier band 1/2) and an rms down to 200 nJy/beam over 10 - 30 deg$^2$ in 2000 hours (deep tier band 1/2), these surveys will directly detect faint radio-loud and radio-quiet AGN (down to a 1 GHz radio luminosity of about $2\\times10^{23}$ W/Hz at $z=6$). For the first time, this will enable us to conduct detailed studies of the cosmic evolution of radio AGN activity to the cosmic dawn ($z\\gtrsim6$), covering all environmental densities.

  17. Merging and Clustering of the Swift BAT AGN Sample

    CERN Document Server

    Koss, Michael; Veilleux, Sylvain; Winter, Lisa; 10.1088/2041-8205/716/2/L125

    2010-01-01

    We discuss the merger rate, close galaxy environment, and clustering on scales up to a Mpc of the SWIFT BAT hard X-ray sample of nearby (z<0.05), moderate-luminosity active galactic nuclei (AGN). We find a higher incidence of galaxies with signs of disruption compared to a matched control sample (18% versus 1%) and of close pairs within 30 kpc (24% versus 1%). We also find a larger fraction with companions compared to normal galaxies and optical emission line selected AGN at scales up to 250 kpc. We hypothesize that these merging AGN may not be identified using optical emission line diagnostics because of optical extinction and dilution by star formation. In support of this hypothesis, in merging systems we find a higher hard X-ray to [OIII] flux ratio, as well as emission line diagnostics characteristic of composite or star-forming galaxies, and a larger IRAS 60 um to stellar mass ratio.

  18. Sonochemical Reactors.

    Science.gov (United States)

    Gogate, Parag R; Patil, Pankaj N

    2016-10-01

    Sonochemical reactors are based on the generation of cavitational events using ultrasound and offer immense potential for the intensification of physical and chemical processing applications. The present work presents a critical analysis of the underlying mechanisms for intensification, available reactor configurations and overview of the different applications exploited successfully, though mostly at laboratory scales. Guidelines have also been presented for optimum selection of the important operating parameters (frequency and intensity of irradiation, temperature and liquid physicochemical properties) as well as the geometric parameters (type of reactor configuration and the number/position of the transducers) so as to maximize the process intensification benefits. The key areas for future work so as to transform the successful technique at laboratory/pilot scale into commercial technology have also been discussed. Overall, it has been established that there is immense potential for sonochemical reactors for process intensification leading to greener processing and economic benefits. Combined efforts from a wide range of disciplines such as material science, physics, chemistry and chemical engineers are required to harness the benefits at commercial scale operation.

  19. The INTEGRAL/IBIS AGN catalogue: an update

    Science.gov (United States)

    Malizia, A.; Landi, R.; Molina, M.; Bassani, L.; Bazzano, A.; Bird, A. J.; Ubertini, P.

    2016-07-01

    In the most recent IBIS survey based on observations performed during the first 1000 orbits of INTEGRAL, are listed 363 high-energy emitters firmly associated with AGN, 107 of which are reported here for the first time. We have used X-ray data to image the IBIS 90 per cent error circle of all the AGN in the sample of 107, in order to obtain the correct X-ray counterparts, locate them with arcsec accuracy and therefore pinpoint the correct optical counterparts. This procedure has led to the optical and spectral characterization of the entire sample. This new set consists of 34 broad line or type 1 AGN, 47 narrow line or type 2 AGN, 18 blazars and 8 sources of unknown class. These eight sources have been associated with AGN from their positional coincidence with 2MASX/Radio/X-ray sources. Seven high-energy emitters have been included since they are considered to be good AGN candidates. Spectral analysis has been already performed on 55 objects and the results from the most recent and/or best statistical measurements have been collected. For the remaining 52 sources, we report the spectral analysis for the first time in this work. We have been able to obtain the full X-ray coverage of the sample making use of data from Swift/XRT, XMM-Newton and NuSTAR. In addition to the spectral characterization of the entire sample, this analysis has enabled us to identify peculiar sources and by comparing different data sets, highlight flux variability in the 2-10 keV and 20-40 keV bands.

  20. The Future of X-ray Reverberation from AGN

    CERN Document Server

    Fabian, A C; Cackett, E M; Kara, E; Uttley, P; Wilkins, D R

    2016-01-01

    XMM-Newton is capable of making a transformational advance in our understanding of how luminous accreting black holes work, by dedicating about 10 per cent of future observing time to long observations, of order Megaseconds, to X-ray variable Active Galactic Nuclei (AGN) research. This would enable reverberation studies, already a commonplace feature of AGN, to proceed to the next level and follow the behaviour of the powerful dynamic corona. Such a dedicated legacy programme can only be carried out with XMM-Newton.

  1. Viscous time lags between starburst and AGN activity

    Science.gov (United States)

    Blank, Marvin; Duschl, Wolfgang J.

    2016-10-01

    There is strong observational evidence indicating a time lag of order of some 100 Myr between the onset of starburst and AGN activity in galaxies. Dynamical time lags have been invoked to explain this. We extend this approach by introducing a viscous time lag the gas additionally needs to flow through the AGN's accretion disc before it reaches the central black hole. Our calculations reproduce the observed time lags and are in accordance with the observed correlation between black hole mass and stellar velocity dispersion.

  2. PAHS AS TRACERS OF LOCAL AGN-STARBURST CONNECTION

    Directory of Open Access Journals (Sweden)

    Mario-A. Higuera-G.

    2013-01-01

    Full Text Available The main purpose of this research was to investigate how energetic processes associated with active galactic nuclei (AGN are related to those due to nuclear or circumnuclear star formation activity. Photometric and spectroscopic data were used to discriminate between these processes in a sample of starburst, infrared galaxies and AGNs. Here, we propose new diagnostic diagrams based on the 7.7 μm polycyclic aromatic hydrocarbon emission band, the L(MIR,FIR infrared ratio and the q parameter. The diagnostic diagrams allow us to discriminate the behavior of quasars and Seyfert 1-Seyfert 2 galaxies from starbursts and LIRGs-ULIRGs objects.

  3. Fourier series

    CERN Document Server

    Tolstov, Georgi P

    1962-01-01

    Richard A. Silverman's series of translations of outstanding Russian textbooks and monographs is well-known to people in the fields of mathematics, physics, and engineering. The present book is another excellent text from this series, a valuable addition to the English-language literature on Fourier series.This edition is organized into nine well-defined chapters: Trigonometric Fourier Series, Orthogonal Systems, Convergence of Trigonometric Fourier Series, Trigonometric Series with Decreasing Coefficients, Operations on Fourier Series, Summation of Trigonometric Fourier Series, Double Fourie

  4. HST-COS OBSERVATIONS OF AGNs. III. SPECTRAL CONSTRAINTS IN THE LYMAN CONTINUUM FROM COMPOSITE COS/G140L DATA

    Energy Technology Data Exchange (ETDEWEB)

    Tilton, Evan M.; Shull, J. Michael; Danforth, Charles W. [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, 389-UCB, Boulder, CO 80309 (United States); Stevans, Matthew L., E-mail: evan.tilton@colorado.edu, E-mail: michael.shull@colorado.edu, E-mail: charles.danforth@colorado.edu, E-mail: stevans@astro.as.utexas.edu [Department of Astronomy, The University of Texas at Austin, Austin, TX 78712 (United States)

    2016-01-20

    The rest-frame ultraviolet (UV) spectra of active galactic nuclei (AGNs) are important diagnostics of both accretion disk physics and their contribution to the metagalactic ionizing UV background. Though the mean AGN spectrum is well characterized with composite spectra at wavelengths greater than 912 Å, the shorter-wavelength extreme-UV (EUV) remains poorly studied. In this third paper in a series on the spectra of AGNs, we combine 11 new spectra taken with the Cosmic Origins Spectrograph on the Hubble Space Telescope with archival spectra to characterize the typical EUV spectral slope of AGNs from λ{sub rest} ∼ 850 Å down to λ{sub rest} ∼ 425 Å. Parameterizing this slope as a power law, we obtain F{sub ν} ∝ ν{sup −0.72±0.26}, but we also discuss the limitations and systematic uncertainties of this model. We identify broad emission features in this spectral region, including emission due to ions of O, Ne, Mg, and other species, and we limit the intrinsic He i 504 Å photoelectric absorption edge opacity to τ{sub He} {sub i} < 0.047.

  5. HST-COS Observations of AGNs. III. Spectral Constraints in the Lyman Continuum from Composite COS/G140L Data

    Science.gov (United States)

    Tilton, Evan M.; Stevans, Matthew L.; Shull, J. Michael; Danforth, Charles W.

    2016-01-01

    The rest-frame ultraviolet (UV) spectra of active galactic nuclei (AGNs) are important diagnostics of both accretion disk physics and their contribution to the metagalactic ionizing UV background. Though the mean AGN spectrum is well characterized with composite spectra at wavelengths greater than 912 Å, the shorter-wavelength extreme-UV (EUV) remains poorly studied. In this third paper in a series on the spectra of AGNs, we combine 11 new spectra taken with the Cosmic Origins Spectrograph on the Hubble Space Telescope with archival spectra to characterize the typical EUV spectral slope of AGNs from λrest ˜ 850 Å down to λrest ˜ 425 Å. Parameterizing this slope as a power law, we obtain Fν ∝ ν-0.72±0.26, but we also discuss the limitations and systematic uncertainties of this model. We identify broad emission features in this spectral region, including emission due to ions of O, Ne, Mg, and other species, and we limit the intrinsic He i 504 Å photoelectric absorption edge opacity to τHe i contract NAS5-26555.

  6. Kiloparsec-scale Spatial Offsets in Double-peaked Narrow-line AGNs. I. Markers for Selection of Compelling Dual AGN Candidates

    CERN Document Server

    Comerford, Julia M; Stern, Daniel; Cooper, Michael C; Weiner, Benjamin J; Newman, Jeffrey A; Harrison, Fiona; Madsen, Kristin; Barrows, R Scott

    2011-01-01

    Merger-remnant galaxies with kpc-scale separation dual active galactic nuclei (AGNs) should be widespread as a consequence of galaxy mergers and triggered gas accretion onto supermassive black holes, yet very few dual AGNs have been observed. Galaxies with double-peaked narrow AGN emission lines in the Sloan Digital Sky Survey are plausible dual AGN candidates, but their double-peaked profiles could also be the result of gas kinematics or AGN-driven outflows and jets on small or large scales. To help distinguish between these scenarios, we have obtained spatial profiles of the AGN emission via follow-up longslit spectroscopy of 81 double-peaked narrow-line AGNs in SDSS at 0.03 < z < 0.36 using Lick, Palomar, and MMT Observatories. We find that all 81 systems exhibit double AGN emission components with ~kpc projected spatial separations on the sky, which suggests that they are produced by kpc-scale dual AGNs or kpc-scale outflows, jets, or rotating gaseous disks. In addition, we find that the subsample (...

  7. Role of cluster size and substrate in the gas phase CC bond coupling reactions of allyl halides mediated by Agn+ and Agn-1H+ cluster cations

    Science.gov (United States)

    Wang, Farrah Qiuyun; Khairallah, George N.; O'Hair, Richard A. J.

    2009-06-01

    Previous studies have demonstrated that the silver hydride cluster cation Ag4H+ promotes CC bond coupling of allylbromide [G.N. Khairallah, R.A.J. O'Hair, Angewandte Chemie International Edition 44 (2005) 728]. Here the influence of both the nature and the size of the silver cluster cation and the substrate on CC bond coupling are examined. Thus each of the cations Ag2H+, Ag4H+, Ag3+, and Ag5+ were allowed to react with three different halides: allyl chloride, allyl bromide and allyl iodide. No CC bond coupling is observed in the reactions of the cluster cations with allyl chloride. There are four main reaction sequences that result in CC bond coupling for allyl bromide and allyl iodide mediated by Agn+ and Agn-1H+ clusters: (i) A sequence involving the reactions of silver cluster cations with two molecules of C3H5X: Agn+ --> Agn(C3H5X)+ --> AgnX2+. This only occurs in the cases of: n = 3 and X = I; n = 5 and X = Br. (ii) A sequence involving the reactions of silver cluster cations with two molecules of C3H5X via an organometallic intermediate: Agn+ --> Agn-1(C3H5)+ --> Agn-1X+. This only occurs in the cases of: n = 5 and X = Br and I. (iii) A sequence involving the reactions of silver hydride cluster cations with three molecules of C3H5X: Agn-1H+ --> Agn-1X+ --> Agn-1X(C3H5X)+ --> Ag(C3H5)2+ and Agn-1X3+. This only occurs in the cases of: n = 5 and X = Br and I. (iv) A sequence involving the reactions of silver hydride cluster cations with three molecules of C3H5X via an organometallic intermediate: Agn-1H+ --> Agn-1X+ --> Agn-3(C3H5)+ --> Ag(C3H5)2+ and Agn-3X+. This only occurs in the cases of: n = 5 and X = I.

  8. Fast ionized X-ray absorbers in AGNs

    Science.gov (United States)

    Fukumura, K.; Tombesi, F.; Kazanas, D.; Shrader, C.; Behar, E.; Contopoulos, I.

    2016-05-01

    We investigate the physics of the X-ray ionized absorbers often identified as warm absorbers (WAs) and ultra-fast outflows (UFOs) in Seyfert AGNs from spectroscopic studies in the context of magnetically-driven accretion-disk wind scenario. Launched and accelerated by the action of a global magnetic field anchored to an underlying accretion disk around a black hole, outflowing plasma is irradiated and ionized by an AGN radiation field characterized by its spectral energy density (SED). By numerically solving the Grad-Shafranov equation in the magnetohydrodynamic (MHD) framework, the physical property of the magnetized disk-wind is determined by a wind parameter set, which is then incorporated into radiative transfer calculations with xstar photoionization code under heating-cooling equilibrium state to compute the absorber's properties such as column density N_H, line-of-sight (LoS) velocity v, ionization parameter ξ, among others. Assuming that the wind density scales as n ∝ r-1, we calculate theoretical absorption measure distribution (AMD) for various ions seen in AGNs as well as line spectra especially for the Fe Kα absorption feature by focusing on a bright quasar PG 1211+143 as a case study and show the model's plausibility. In this note we demonstrate that the proposed MHD-driven disk-wind scenario is not only consistent with the observed X-ray data, but also help better constrain the underlying nature of the AGN environment in a close proximity to a central engine.

  9. The impact of AGN on their host galaxies

    CERN Document Server

    Harrison, C M

    2013-01-01

    In these proceedings I briefly: (1) review the impact (or "feedback") that active galactic nuclei (AGN) are predicted to have on their host galaxies and larger scale environment, (2) review the observational evidence for or against these predictions and (3) present new results on ionised outflows in AGN. The observational support for the "maintenance mode" of feedback is strong (caveat the details); AGN at the centre of massive halos appear to be regulating the cooling of hot gas, which could in turn control the levels of future star formation (SF) and black hole growth. In contrast, direct observational support for more rapid forms of feedback, which dramatically impact on SF (i.e., the "quasar mode"), remains elusive. From a systematic study of the spectra of approx. 24000 z10^23 W/Hz). Follow-up IFU observations have shown that these extreme gas kinematics are extended over kilo-parsec scales. However, the co-existence of high-levels of SF, luminous AGN activity and radio jets raises interesting questions ...

  10. Unveiling the physics of AGN through X-ray variability

    Science.gov (United States)

    Hernández-García, L.; González-Martín, O.; Masegosa, J.; Márquez, I.

    2017-03-01

    Although variability is a general property characterizing active galactic nuclei (AGN), it is not well established whether the changes occur in the same way in every nuclei. The main purpose of this work is to study the X-ray variability pattern(s) in AGN selected at optical wavelengths in a large sample, including low ionization nuclear emission line regions (LINERs) and type 1.8, 1.9, and 2 Seyferts, using the public archives in Chandra and/or XMM–Newton. Spectra of the same source gathered at different epochs were simultaneously fitted to study long term variations; the variability patterns were studied allowing different parameters to vary during the spectral fit. Whenever possible, short term variations from the analysis of the light curves and long term UV flux variability were studied. Variations at X-rays in timescales of months/years are very common in all AGN families but short term variations are only found in type 1.8 and 1.9 Seyferts. The main driver of the long term X-ray variations seems to be related to changes in the nuclear power. Other variability patterns cannot be discarded in a few cases. We discuss the geometry and physics of AGN through the X-ray variability analysis.

  11. The Evolution of the AGN population in the MORGANA model

    Science.gov (United States)

    Fontanot, F.; Monaco, P.; Cristiani, S.; Tozzi, P.

    2008-10-01

    We present the results of the MOdel for the Rise of Galaxies aNd Agns (MORGANA), that includes in a self-consistent way the accretion of matter onto Super-Massive Black Holes. We compare MORGANA predictions to the observed evolution of the AGN space density (inferred from optical and X-ray surveys) and we find that that it is possible to reproduce the apparent downsizing of the AGN population in the framework of concordance cosmology. We will show that this result is likely due to the improved treatment of gas cooling and feedback in MORGANA, and in particular to the modeling of the stellar kinetic feedback, arising in star-forming bulges as a consequence of the level of turbolence. On the other hand, the predicted low-mass end of BH-bulge relation is steeper than observed: we discuss this disagreement on the light of the predicted excess of small bulges, which is common to several models of galaxy formation and evolution. Finally we will show that a stronger constrain on the relative importance of the physical processes involved in the build up of the AGN population move from the observed redshift evolution of the BH-Bulge relation.

  12. Compton Thick AGN in the XMM-COSMOS survey

    CERN Document Server

    Lanzuisi, G; Georgantopoulos, I; Georgakakis, A; Delvecchio, I; Akylas, T; Berta, S; Bongiorno, A; Brusa, M; Cappelluti, N; Civano, F; Comastri, A; Gilli, R; Gruppioni, C; Hasinger, G; Iwasawa, K; Koekemoer, A; Lusso, E; Marchesi, S; Mainieri, V; Merloni, A; Mignoli, M; Piconcelli, E; Pozzi, F; Rosario, D J; Salvato, M; Silverman, J; Trakhtenbrot, B; Vignali, C; Zamorani, G

    2014-01-01

    Heavily obscured, Compton Thick (CT, NH>10^24 cm-2) AGN may represent an important phase in AGN/galaxy co-evolution and are expected to provide a significant contribution to the cosmic X-ray background (CXB) at its peak. Through direct X-ray spectra analysis, we selected 39 heavily obscured AGN (NH>3x10^23 cm-2) in the 2 deg^2 XMM-COSMOS survey. Thanks to deeper Chandra data available in the field, we can define 10 of these sources as bona-fide CT, spanning a large range of redshift and luminosity, and estimate the efficiency of our selection to be of the order of 80%. We collected the multi-wavelength information available for these sources, to study the distribution of BH mass (MBH), Eddington ratio (lambda_Edd), stellar mass (M*), specific star formation rate (sSFR) in comparison with a sample of unobscured AGN. We find that highly obscured sources tend to have significantly smaller MBH and higher lambda_Edd with respect to unobscured sources. The sSFR of highly obscured sources is consistent with the one ...

  13. The Prevalence of Gas Outflows in Type 2 AGNs

    CERN Document Server

    Woo, Jong-Hak; Son, Donghoon; Karouzos, Marios

    2015-01-01

    To constrain the nature and fraction of the ionized gas outflows in AGNs, we perform a detailed analysis on gas kinematics as manifested by the velocity dispersion and shift of the OIII {\\lambda}5007 emission line, using a large sample of ~39,000 type 2 AGNs at z<0.3. First, we confirm a broad correlation between OIII and stellar velocity dispersions, indicating that the bulge gravitational potential plays a main role in determining the OIII kinematics. However, OIII velocity dispersion is on average larger than stellar velocity dispersion by a factor of 1.3-1.4, suggesting that the non-gravitational component, i.e., outflows, is almost comparable to the gravitational component. Second, the increase of the OIII velocity dispersion (after normalized by stellar velocity dispersion) with both AGN luminosity and Eddington ratio suggests that non-gravitational kinematics are clearly linked to AGN accretion. The distribution in the OIII velocity - velocity dispersion diagram dramatically expands toward large val...

  14. FLOYDS Classification of Gaia16ann as an AGN

    Science.gov (United States)

    Hosseinzadeh, G.; Arcavi, I.; Howell, D. A.; McCully, C.; Valenti, S.

    2016-07-01

    We obtained a spectrum of Gaia16ann on 2016 July 7.5 UT with the robotic FLOYDS instrument mounted on the LCOGT 2-meter telescope on Haleakala, Hawai'i. Using SNID (Blondin & Tonry 2007, ApJ, 666, 1024), we find a good fit to an AGN at redshift z=0.196.

  15. Progress of research on AGNs at the Urumqi Observatory

    Institute of Scientific and Technical Information of China (English)

    T.P.KRICHBAUM; L.FUHRMANN; N.MARCHILI

    2010-01-01

    We report the progress on Very Long Baseline Interferometry(VLBI) observations of Gigahertz Peaked Spectrum(GPS) radio sources,and single-dish observations of active galactic nuclei(AGNs).The GPS sources are a kind of young AGNs observable in radio.From our VLBI observations at 1.6 and 5 GHz with the European VLBI Network(EVN) including the Urumqi and Shanghai stations,most GPS sources show compact doubles with sizes less than 1 kiloparsec.We have classified the sources into double-lobes,core-jets,and complex structures according to the spectral indices as well as images.We also estimated the values of the jet viewing angle for the symmetric objects.In addition,we are monitoring a few samples of AGNs with the Urumqi 25-meter radio telescope,in order to find flux variability.We detected rapid flux variability in quasar 1156+295,and relatively slow variability in a few of the others.The origin of the rapid variability is discussed.Moreover,we launched a radio-optical monitoring program called Fermi-AGN in 2009.

  16. NIR Flare of the AGN Candidate PMNJ0107+0333

    Science.gov (United States)

    Carrasco, L.; Miramon, J.; Recillas, E.; Porras, A.; Chavushyan, V.; Mayya, D. Y.

    2016-12-01

    We report on the new NIR flare of the AGN candidate PMNJ0107+0333, cross identified with the X-ray source 1RXS J010729.5+033341. On November 13th,2016 (MJD 2457705.699), we found the source with the following flux in the NIR band: H = 14.657 +/- 0.05.

  17. Converting the Audience: A Conversation with Agnes Wilcox

    Science.gov (United States)

    Becker, Becky

    2006-01-01

    This article presents a conversation with Agnes Wilcox, Executive Director of Prison Performing Arts in St. Louis, Missouri, about Prison Performing Arts. Although the average person might balk at the notion of interacting with prison inmates, finding it intimidating, worrisome, or self-sacrificial, for Wilcox, Prison Performing Arts is a…

  18. Similarities between circular polarization in Galactic jet sources and AGN

    NARCIS (Netherlands)

    Macquart, JP; Wu, K; Hannikainen, DC; Sault, RJ; Jauncey, DL

    2003-01-01

    We compare the observational properties of the circular polarization in Galactic jet sources with that observed in AGN, and outline the constraints they place on the mechanism responsible for the circular polarization. We also discuss the implications of the time scale of polarization variations on

  19. Modeling the reverberation of optical polarization in AGN

    CERN Document Server

    Lobos, P Andrea Rojas; Marin, Frederic

    2016-01-01

    According to the standard paradigm, the strong and compact luminosity of active galactic nuclei (AGN) is due to multi-temperature black body emission originating from an accretion disk formed around a supermassive black hole. This central engine is thought to be surrounded by a dusty region along the equatorial plane and by ionized winds along the poles. The innermost regions cannot yet be resolved neither in the optical nor in the infrared and it is fair to say that we still lack a satisfactory understanding of the physical processes, geometry and composition of the central (sub-parsec) components of AGN. Like spectral or polarimetric observations, the reverberation data needs to be modeled in order to infer constraints on the AGN geometry (such as the inner radius or the half-opening angle of the dusty torus). In this research note, we present preliminary modeling results using a time-dependent Monte Carlo method to solve the radiative transfer in a simplified AGN set up. We investigate different model conf...

  20. The Eddington Ratio of H2O Maser Host AGN

    Indian Academy of Sciences (India)

    Q. Guo; J. S. Zhang; J. Wang

    2011-03-01

    The Eddington ratio was derived for the entire maser host AGN sample, based on the intrinsic X-ray luminosity, the X-ray bolometric correction X and the mass of central black hole. Further the [O III] bolometric correction [O III] was estimated for our sample. Possible relations were also investigated between the maser luminosity and the bolometric luminosity – the Eddington ratio.

  1. On the Superluminal Motion of Radio-Loud AGNs

    Indian Academy of Sciences (India)

    Zhi-Bin Zhang; Yi-Zhen Zhang

    2011-03-01

    Apparent superluminal motion of different radio-loud AGNs are similarly related with beaming effect. The cosmological expanding effect would play no part in the superluminal motion of radio galaxies, BL Lacertae objects as well as quasars.Meanwhile, we confirm that estimates for apparent velocity app and Doppler boosting factor based on multi-wavelength combination and variability are comparable.

  2. Highly variable AGN from the XMM-Newton Slew Survey

    CERN Document Server

    Strotjohann, N L; Starling, R L C; Esquej, P; Read, A M; Evans, P A; Miniutti, G

    2016-01-01

    We investigate the properties of a variability-selected complete sample of AGN in order to identify the mechanisms which cause large amplitude X-ray variability on time scales of years. A complete sample of 24 sources was constructed, from AGN which changed their soft X-ray luminosity by more than one order of magnitude over 5--20 years between ROSAT observations and the XMM Slew Survey. Follow-up observations were obtained with the Swift satellite. After removal of two probable spurious sources, we find that the sample has global properties which differ little from a non-varying control sample drawn from the wider XMM-Slew/ROSAT/Veron sample of all secure AGN detections. A wide range of AGN types are represented in the varying sample. The black hole mass distributions for the varying and non-varying sample are not significantly different. This suggests that long timescale variability is not strongly affected by black hole mass. There is marginal evidence that the variable sources have a lower redshift (2$\\si...

  3. Density functional study of Agn-1Y (n =2-10) clusters

    Institute of Scientific and Technical Information of China (English)

    Liu Xiao-Yong; Zhu Zheng-He; Sheng Yong

    2011-01-01

    properties of Agn-1Y (n =2-10) clusters in this paper.The structural optimization and the frequency analysis are performed at the B3LYP/LANL2DZ level.Meanwhile,the differences in geometry,stability and electronic properties between Agn and Agn-1Y (n =2-10) clusters are also studied.The results show that for the doping of the yttrium atoms,the structures and the average binding lengths of the Agn clusters are greatly changed. In addition,the thermodynamic stabilities of the Agn clusters are enhanced generally with the doping of the Y atoms.In addition,the chemical stabilities of the Agn- 1 Y clusters are still improved compared with that of the three-dimensional Agn clusters.

  4. A radio view of high-energy emitting AGNs

    Science.gov (United States)

    Schulz, Robert Frank

    2016-07-01

    Active galactic nuclei (AGNs) are among the most energetic objects in the Universe. These galaxies that are dominated in part or even throughout the electromagnetic spectrum by emission from their central, compact region. AGNs are extensively studied by multi-wavelength observations. In the standard picture, the main driver of an AGN is a supermassive black hole (SMBH) in its centre that is surrounded by an accretion disk. Perpendicular to the disk, in the vicinity of highly magnetized SMBH relativistic outflows of plasma, so-called jets, can form on either side that can reach far beyond the host galaxy. Only about 10% of all AGNs are dominated by emission from these jets due to relativistic beaming effects and these so-called blazars dominate the extragalactic gamma-ray sky. It is commonly accepted that the low-energy emission (radio to UV/X-ray) is due to synchrotron emission from the jet. The high-energy emission is considered to stem from inverse-Compton scattering of photons on the jet particles, but different sources for these photons are discussed (internal or external to the AGN) and other models for the high-energy emission have also been proposed. The nature of the high-energy emission is strongly linked to the location of the emission region in the jet which requires a detailed understanding of the formation and evolution of jets. Radio observations especially using very long baseline interferometry (VLBI) provide the best way to gain direct information on the intrinsic properties of jets down to sub-pc scales, close to their formation region. In this thesis, I focus on the properties of three different AGNs, IC 310, PKS2004-447, and 3C 111 that belong to the small non-blazar population of gamma-ray-loud AGNs. I study them in detail with a variety of radio astronomical instruments with respect to their high-energy emission and in the context of the large monitoring programmes MOJAVE (Monitoring Of Jets in Active galactic nuclei with VLBA Experiments) and

  5. Host Galaxy Properties of the Swift BAT Ultra Hard X-Ray Selected AGN

    Science.gov (United States)

    Koss, Michael; Mushotzky, Richard; Veilleux, Sylvain; Winter, Lisa M.; Baumgartner, Wayne; Tueller, Jack; Gehrels, Neil; Valencic, Lynne

    2011-01-01

    We have assembled the largest sample of ultra hard X-ray selected (14-195 keV) AGN with host galaxy optical data to date, with 185 nearby (zAGN from the Swift Burst Alert Telescope (BAT) sample. The BAT AGN host galaxies have intermediate optical colors (u -- r and g -- r) that are bluer than a comparison sample of inactive galaxies and optically selected AGN from the Sloan Digital Sky Survey (SDSS) which are chosen to have the same stellar mass. Based on morphological classifications from the RC3 and the Galaxy Zoo, the bluer colors of BAT AGN are mainly due to a higher fraction of mergers and massive spirals than in the comparison samples. BAT AGN in massive galaxies (log Stellar Mass >10.5) have a 5 to 10 times higher rate of spiral morphologies than in SDSS AGN or inactive galaxies. We also see enhanced far-IR emission in BAT AGN suggestive of higher levels of star formation compared to the comparison samples. BAT AGN are preferentially found in the most massive host galaxies with high concentration indexes indicative of large bulge-to-disk ratios and large supermassive black holes. The narrow-line (NL) BAT AGN have similar intrinsic luminosities as the SDSS NL Seyferts based on measurements of [O III] Lambda 5007. There is also a correlation between the stellar mass and X-ray emission. The BAT AGN in mergers have bluer colors and greater ultra hard X-ray emission compared to the BAT sample as whole. In agreement with the Unified Model of AGN, and the relatively unbiased nature of the BAT sources, the host galaxy colors and morphologies are independent of measures of obscuration such as X-ray column density or Seyfert type. The high fraction of massive spiral galaxies and galaxy mergers in BAT AGN suggest that host galaxy morphology is related to the activation and fueling of local AGN.

  6. Modeling the reverberation of optical polarization in AGN

    Science.gov (United States)

    Rojas Lobos, P. A.; Goosmann, R.; Marin, F.

    2016-12-01

    According to the standard paradigm, the strong and compact luminosity of active galactic nuclei (AGN) is due to multi-temperature black body emission originating from an accretion disk formed around a supermassive black hole. This central engine is thought to be surrounded by a dusty region along the equatorial plane and by ionized winds along the poles. The innermost regions cannot yet be resolved neither in the optical nor in the infrared and it is fair to say that we still lack a satisfactory understanding of the physical processes, geometry and composition of the central (sub-parsec) components of AGN. Like spectral or polarimetric observations, the reverberation data needs to be modeled in order to infer constraints on the AGN geometry (such as the inner radius or the half-opening angle of the dusty torus). In this research note, we present preliminary modeling results using a time-dependent Monte Carlo method to solve the radiative transfer in a simplified AGN set up. We investigate different model configurations using both polarization and time lags and find a high dependency on the geometry to the time-lag response. For all models there is a clear distinction between edge-on or face-on viewing angles for fluxes and time lags, the later showing a higher wavelength-dependence than the former. Time lags, polarization and fluxes point toward a clear dichotomy between the different inclinations of AGN, a method that could help us to determine the true orientation of the nucleus in Seyfert galaxies.

  7. Kiloparsec-scale outflows are prevalent among luminous AGN: outflows and feedback in the context of the overall AGN population

    CERN Document Server

    Harrison, C M; Mullaney, J R; Swinbank, A M

    2014-01-01

    We present integral field unit (IFU) observations covering the [O III]4959,5007 and H-Beta emission lines of sixteen z~(6-16) kpc in all targets and observe signatures of spherical outflows and bi-polar superbubbles. We show that our targets are representative of z 5x10^41 erg/s) type 2 AGN and that ionised outflows are not only common but also in >=70% (3 sigma confidence) of cases, they are extended over kiloparsec scales. Our study demonstrates that galaxy-wide energetic outflows are not confined to the most extreme star-forming galaxies or radio-luminous AGN; however, there may be a higher incidence of the most extreme outflow velocities in quasars hosted in ultra-luminous infrared galaxies. Both star formation and AGN activity appear to be energetically viable to drive the outflows and we find no definitive evidence that favours one process over the other. Although highly uncertain, we derive mass outflow rates (typically ~10x the SFRs), kinetic energies (~0.5-10% of L[AGN]) and momentum rates (typically...

  8. AGN-Host Galaxy Connection: Morphology and Colours of X-ray Selected AGN at z < 2

    CERN Document Server

    Pović, M; García, A M Pérez; Bongiovanni, A; Cepa, J; Huertas-Company, M; Lara-López, M A; Lorenzo, M Fernández; Ederoclite, A; Alfaro, E; Castañeda, H; Gallego, J; González-Serrano, J I; González, J J

    2012-01-01

    The connection between AGN and their host galaxies has been widely studied over recent years, showing it to be of great importance for providing answers to some fundamental questions related with AGN fueling mechanisms, their formation and evolution. Using X-ray and one of the deepest broad-band optical data sets, we studied morphology and colours in relationship with X-ray properties for sources at redshifts z < 2.0, using a sample of 262 AGN in the Subaru/XMM-Newton Deep Survey (SXDS). Morphological classification was obtained using the galSVM code, one of the new methods useful especially when dealing with high-redshift sources and low-resolution data. Colour-magnitude diagrams were studied in relationship with redshift, morphology, X-ray obscuration, and X-ray-to-optical flux ratio. Finally, the significance of different regions was analysed on colour-magnitude diagrams, relating the observed properties of AGN populations with some models of their formation and evolution.

  9. The MOSDEF survey: AGN multi-wavelength identification, selection biases and host galaxy properties

    CERN Document Server

    Azadi, Mojegan; Aird, James; Reddy, Naveen; Shapley, Alice; Freeman, William R; Kriek, Mariska; Leung, Gene C K; Mobasher, Bahram; Price, Sedona H; Sanders, Ryan L; Shivaei, Irene; Siana, Brian

    2016-01-01

    We present results from the MOSFIRE Deep Evolution Field (MOSDEF) survey on the identification, selection biases and host galaxy properties of 55 X-ray, IR and optically-selected active galactic nuclei (AGN) at $1.4 < z < 3.8$. We obtain rest-frame optical spectra of galaxies and AGN and use the BPT diagram to identify optical AGN. We examine the uniqueness and overlap of the AGN identified at different wavelengths. There is a strong bias against identifying AGN at any wavelength in low mass galaxies, and an additional bias against identifying IR AGN in the most massive galaxies. AGN host galaxies span a wide range of star formation rate (SFR), similar to inactive galaxies once stellar mass selection effects are accounted for. However, we generally identify IR AGN in less dusty galaxies with relatively higher SFR and optical AGN in dusty galaxies with relatively lower SFR. X-ray AGN selection does not display a bias with host galaxy SFR. These results are consistent with those from larger studies at low...

  10. X-ray absorption, nuclear infrared emission and dust covering factors of AGN: testing Unification Schemes

    CERN Document Server

    Mateos, S; Alonso-Herrero, A; Hernán-Caballero, A; Barcons, X; Ramos, A Asensio; Watson, M G; Blain, A; Caccianiga, A; Ballo, L; Braito, V; Almeida, C Ramos

    2016-01-01

    We present the distributions of geometrical covering factors of active galactic nuclei (AGNs) dusty tori (f2) using an X-ray selected complete sample of 227 AGN drawn from the Bright Ultra-hard XMM-Newton Survey. The AGN have z from 0.05 to 1.7, 2-10 keV luminosities between 10^42 and 10^46 erg/s and Compton-thin X-ray absorption. Employing data from UKIDSS, 2MASS and the Wide-field Infrared Survey Explorer in a previous work we determined the rest-frame 1-20 microns continuum emission from the torus which we model here with the clumpy torus models of Nenkova et al. Optically classified type 1 and type 2 AGN are intrinsically different, with type 2 AGN having on average tori with higher f2 than type 1 AGN. Nevertheless, ~20 per cent of type 1 AGN have tori with large covering factors while ~23-28 per cent of type 2 AGN have tori with small covering factors. Low f2 are preferred at high AGN luminosities, as postulated by simple receding torus models, although for type 2 AGN the effect is certainly small. f2 in...

  11. Constraining the properties of AGN host galaxies with Spectral Energy Distribution modeling

    CERN Document Server

    Ciesla, L; Georgakakis, A; Bernhard, E; Mitchell, P D; Buat, V; Elbaz, D; Floc'h, E Le; Lacey, C G; Magdis, G E; Xilouris, M

    2015-01-01

    [abridged] We use the latest release of CIGALE, a galaxy SED fitting model relying on energy balance, to study the influence of an AGN in estimating both the SFR and stellar mass in galaxies, as well as the contribution of the AGN to the power output of the host. Using the galaxy formation SAM GALFORM, we create mock galaxy SEDs using realistic star formation histories (SFH) and add an AGN of Type 1, Type 2, or intermediate type whose contribution to the bolometric luminosity can be variable. We perform an SED fitting of these catalogues with CIGALE assuming three different SFHs: a single- and double-exponentially-decreasing, and a delayed SFH. Constraining thecontribution of an AGN to the LIR (fracAGN) is very challenging for fracAGN<20%, with uncertainties of ~5-30% for higher fractions depending on the AGN type, while FIR and sub-mm are essential. The AGN power has an impact on the estimation of $M_*$ in Type 1 and intermediate type AGNs but has no effect for galaxies hosting Type 2 AGNs. We find that i...

  12. Investigating the host galaxies of luminous AGN in the local universe with integral field spectroscopy

    Science.gov (United States)

    McElroy, Rebecca; Croom, Scott; Husemann, Bernd; Close AGN Reference Survey; SAMI Galaxy Survey

    2017-01-01

    This thesis investigates how galaxies and their super massive black holes coevolve. We use integral field spectroscopy to search for evidence of AGN feedback and triggering. We demonstrate that outflows are ubiquitous among luminous local type 2 AGN using observations from the AAT's SPIRAL instrument. Using multiple component Gaussian emission line decomposition we are able to disentangle the kinematic and ionisation properties of these winds. This allows us to argue that the outflows from these AGN are directly impacting the surrounding ISM within the galaxies. We search for evidence of AGN triggering using data from The Close AGN Reference Survey (CARS). CARS aims to provide a detailed multi-wavelength view of 40 nearby (0.01 type not once, but twice. So called ‘changing look’ AGN are an uncommon phenomenon, but twice changed AGN are much rarer. This AGN first transitioned from a narrow line AGN (type 2) to a broad line AGN (type 1) in the 1980s. It was recently observed as part of CARS. Examination of the MUSE data for this particular source showed that it no longer had the spectral features typical of a type 1 AGN. The continuum emission from the accretion disk was no longer visible and the broad lines were dramatically diminished. In this talk we describe the possible reasons for this change, supported by analysis of multi-epoch optical photometry and spectroscopy, alongside data obtained through director’s discretionary time from Chandra, HST, and the VLA. We then conclude by discussing the implications of this discovery on our understanding of AGN timescales and the physics behind AGN spectral types.

  13. Hybrid adsorptive membrane reactor

    Science.gov (United States)

    Tsotsis, Theodore T. (Inventor); Sahimi, Muhammad (Inventor); Fayyaz-Najafi, Babak (Inventor); Harale, Aadesh (Inventor); Park, Byoung-Gi (Inventor); Liu, Paul K. T. (Inventor)

    2011-01-01

    A hybrid adsorbent-membrane reactor in which the chemical reaction, membrane separation, and product adsorption are coupled. Also disclosed are a dual-reactor apparatus and a process using the reactor or the apparatus.

  14. D and DR Reactors

    Data.gov (United States)

    Federal Laboratory Consortium — The world's second full-scale nuclear reactor was the D Reactor at Hanford which was built in the early 1940's and went operational in December of 1944.D Reactor ran...

  15. Hybrid adsorptive membrane reactor

    Science.gov (United States)

    Tsotsis, Theodore T.; Sahimi, Muhammad; Fayyaz-Najafi, Babak; Harale, Aadesh; Park, Byoung-Gi; Liu, Paul K. T.

    2011-03-01

    A hybrid adsorbent-membrane reactor in which the chemical reaction, membrane separation, and product adsorption are coupled. Also disclosed are a dual-reactor apparatus and a process using the reactor or the apparatus.

  16. The Spitzer mid-infrared AGN survey. I - optical and near-infrared spectroscopy of candidate obscured and normal AGN selected in the mid-infrared

    CERN Document Server

    Lacy, M; Gates, E L; Nielsen, D M; Petric, A O; Sajina, A; Urrutia, T; Drews, S Cox; Harrison, C; Seymour, N; Storrie-Lombardi, L J

    2013-01-01

    We present the results of a program of optical and near-infrared spectroscopic follow-up of candidate Active Galactic Nuclei (AGN) selected in the mid-infrared. This survey selects both normal and obscured AGN closely matched in luminosity across a wide range, from Seyfert galaxies with bolometric luminosities L_bol~10^10L_sun, to highly luminous quasars (L_bol~10^14L_sun), and with redshifts from 0-4.3. Samples of candidate AGN were selected through mid-infrared color cuts at several different 24 micron flux density limits to ensure a range of luminosities at a given redshift. The survey consists of 786 candidate AGN and quasars, of which 672 have spectroscopic redshifts and classifications. Of these, 137 (20%) are type-1 AGN with blue continua, 294 (44%) are type-2 objects with extinctions A_V>~5 towards their AGN, 96 (14%) are AGN with lower extinctions (A_V~1) and 145 (22%) have redshifts, but no clear signs of AGN activity in their spectra. 50% of the survey objects have L_bol >10^12L_sun, in the quasar ...

  17. Cold Dust Emission from X-ray AGN in the SCUBA-2 Cosmology Legacy Survey: Dependence on Luminosity, Obscuration & AGN Activity

    CERN Document Server

    Banerji, Manda; Willott, C J; Geach, J E; Harrison, C M; Alaghband-Zadeh, S; Alexander, D M; Bourne, N; Coppin, K E K; Dunlop, J S; Farrah, D; Jarvis, M; Michalowski, M J; Page, M; Smith, D J B; Swinbank, A M; Symeonidis, M; Van der Werf, P P

    2015-01-01

    We study the 850um emission in X-ray selected AGN in the 2 sq-deg COSMOS field using new data from the SCUBA-2 Cosmology Legacy Survey. We find 19 850um bright X-ray AGN in a high-sensitivity region covering 0.89 sq-deg with flux densities of S850=4-10 mJy. The 19 AGN span the full range in redshift and hard X-ray luminosity covered by the sample - 0.71 X-ray AGN - S850=0.71+/-0.08mJy. We explore trends in the stacked 850um flux densities with redshift, finding no evolution in the average cold dust emission over the redshift range probed. For Type 1 AGN, there is no significant correlation between the stacked 850um flux and hard X-ray luminosity. However, in Type 2 AGN the stacked submm flux is a factor of 2 higher at high luminosities. When averaging over all X-ray luminosities, no significant differences are found in the stacked submm fluxes of Type 1 and Type 2 AGN as well as AGN separated on the basis of X-ray hardness ratios and optical-to-infrared colours. However, at log10(LX) >44.4, dependences in ave...

  18. AGN feedback in the nucleus of M 51

    Science.gov (United States)

    Querejeta, M.; Schinnerer, E.; García-Burillo, S.; Bigiel, F.; Blanc, G. A.; Colombo, D.; Hughes, A.; Kreckel, K.; Leroy, A. K.; Meidt, S. E.; Meier, D. S.; Pety, J.; Sliwa, K.

    2016-10-01

    AGN feedback is invoked as one of the most relevant mechanisms that shape the evolution of galaxies. Our goal is to understand the interplay between AGN feedback and the interstellar medium in M 51, a nearby spiral galaxy with a modest AGN and a kpc-scale radio jet expanding through the disc of the galaxy. For this purpose, we combine molecular gas observations in the CO(1-0) and HCN(1-0) lines from the Plateau de Bure interferometer with archival radio, X-ray, and optical data. We show that there is a significant scarcity of CO emission in the ionisation cone, while molecular gas emission tends to accumulate towards the edges of the cone. The distribution and kinematics of CO and HCN line emission reveal AGN feedback effects out to r ~ 500 pc, covering the whole extent of the radio jet, with complex kinematics in the molecular gas which displays strong local variations. We propose that this is the result of the almost coplanar jet pushing on molecular gas in different directions as it expands; the effects are more pronounced in HCN than in CO emission, probably as the result of radiative shocks. Following previous interpretation of the redshifted molecular line in the central 5'' as caused by a molecular outflow, we estimate the outflow rates to be ṀH2 ~ 0.9 M⊙/ yr and Ṁdense ~ 0.6 M⊙/ yr, which are comparable to the molecular inflow rates (~1 M⊙/ yr); gas inflow and AGN feedback could be mutually regulated processes. The agreement with findings in other nearby radio galaxies suggests that this is not an isolated case, and is probably the paradigm of AGN feedback through radio jets, at least for galaxies hosting low-luminosity active nuclei. The reduced HCN(1-0) datacube is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/593/A118

  19. Radio Loud AGN Unification: Connecting Jets and Accretion

    Directory of Open Access Journals (Sweden)

    Meyer Eileen T.

    2013-12-01

    Full Text Available While only a fraction of Active Galactic Nuclei are observed to host a powerful relativistic jet, a cohesive picture is emerging that radio-loud AGN may represent an important phase in the evolution of galaxies and the growth of the central super-massive black hole. I will review my own recent observational work in radio-loud AGN unification in the context of understanding how and why jets form and their the connection to different kinds of accretion and growing the black hole, along with a brief discussion of possible connections to recent modeling work in jet formation. Starting from the significant observational advances in our understanding of jetted AGN as a population over the last decade thanks to new, more sensitive instruments such as Fermi and Swift as well as all-sky surveys at all frequencies, I will lay out the case for a dichotomy in the jetted AGN population connected to accretion mode onto the black hole. In recent work, we have identified two sub-populations of radio-loud AGN which appear to be distinguished by jet structure, where low-efficiency accreting systems produce ‘weak’ jets which decelerate more rapidly than the ’strong’ jets of black holes accreting near the Eddington limit. The two classes are comprised of: (1The weak jet sources, corresponding to the less collimated, edge-darkened FR Is, with a decelerating or spine-sheath jet with velocity gradients, and (2 The strong jet sources, having fast, collimated jets, and typically displaying strong emission lines. The dichotomy in the vp-Lp plane can be understood as a "broken power sequence" in which jets exist on one branch or the other based on the particular accretion mode (Georganopolous 2011.We suggest that the intrinsic kinetic power (as measured by low-frequency, isotropic radio emission, the orientation, and the accretion rate of the SMBH system are the the fundamental axes needed for unification of radio-loud AGN by studying a well-characterized sample

  20. Optimizing Reactors Selection and Sequencing:Minimum Cost versus Minimum Volume

    Institute of Scientific and Technical Information of China (English)

    Rachid Chebbi

    2014-01-01

    The present investigation targets minimum cost of reactors in series for the case of one single chemical reaction, considering plug flow and stirred tank reactor(s) in the sequence of flow reactors. Using Guthrie’s cost correlations three typical cases were considered based on the profile of the reaction rate reciprocal versus conversion. Significant differences were found compared to the classical approach targeting minimum total reactor volume.

  1. THE ORIGIN OF DOUBLE-PEAKED NARROW LINES IN ACTIVE GALACTIC NUCLEI. I. VERY LARGE ARRAY DETECTIONS OF DUAL AGNs AND AGN OUTFLOWS

    Energy Technology Data Exchange (ETDEWEB)

    Müller-Sánchez, F.; Comerford, J. M.; Nevin, R.; Barrows, R. S. [Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309 (United States); Cooper, M. C. [Center for Cosmology, Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Greene, J. E. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

    2015-11-10

    We have examined a subset of 18 active galactic nuclei (AGNs) drawn from a sample of 81 galaxies that possess double-peaked narrow optical emission line spectra in the Sloan Digital Sky Survey, have 2 optical AGN emission components separated by >0.″2, and are detected in the Faint Images of the Radio Sky at Twenty-centimeters survey. Without follow-up observations, the sources of the double-peaked narrow emission lines are uncertain, and may be produced by kiloparsec-scale separation dual active supermassive black holes, AGN outflows, or disk rotation. In this work, we propose a new methodology to characterize double-peaked narrow emission line galaxies based on optical long-slit spectroscopy and high-resolution multi-band Very Large Array observations. The nature of the radio emission in the sample galaxies is varied. Of the 18 galaxies, we detect 2 compact flat-spectrum radio cores with projected spatial separations on the sky between 0.6 and 1.6 kpc in 3 galaxies: J1023+3243, J1158+3231, and J1623+0808. The two radio sources are spatially coincident with the two optical components of ionized gas with AGN-like line ratios, which confirms the presence of dual AGNs in these three galaxies. Dual AGNs account for only ∼15% (3/18) of the double-peaked AGNs in our sample. Gas kinematics produce ∼75% (13/18) of the double-peaked narrow emission lines, distributed in the following way: seven AGN wind-driven outflows, five radio-jet driven outflows, and one rotating narrow-line region. The remaining 10% (2/18) are ambiguous cases. Our method demonstrates the power of spatially resolved spectroscopy and high-resolution radio observations for the identification of AGN outflows and AGN pairs with angular separations as small as 0.″18.

  2. Key Science Observations of AGNs with KaVA Array

    CERN Document Server

    Kino, Motoki; Zhao, Guang-Yao; Sohn, Bong Won

    2015-01-01

    KaVA (KVN and VERA Array) is a new combined VLBI array with KVN (Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry). First, we briefly review the imaging capabilities of KaVA array which actually achieves more than three times better dynamic range than that achieved by VERA alone. The KaVA images clearly show detailed structures of extended radio jets in AGNs. Next, we represent the key science program to be led by KaVA AGN sub working group. We will conduct the monitoring observations of Sgr A* and M87 because of the largeness of their central super-massive black hole angular sizes. The main science goals of the program are (i) testing magnetically-driven-jet paradigm by mapping velocity fields of the M87 jet, and (ii) obtaining tight constraints on physical properties of radio emitting region in Sgr A*.

  3. THE DETECTION OF EXTREME LOW-LUMINOSITY AGNS

    Directory of Open Access Journals (Sweden)

    D. M. Neri-Larios

    2011-01-01

    Full Text Available Exploramos el diagrama de diagn stico que utiliza la raz n de l neas de emisi n ([NII]h6584 A/H frente al ancho equivalente de [NII]h6584 A, propuesto por Coziol et al. (1998 a una muestra obtenida del SDSS DR5 para separar las galaxias dominadas por formaci n estelar y galaxias con n cleo activo (AGNs de baja luminosidad. Este diagrama de diagn stico no necesita las l neas clasicas de emisi n como [OIII]h5007 A, o H para clasificar el tipo de actividad. Se demuestra emp ricamente que esta combinaci n de l neas de emisi n se puede utilizar para buscar en los llamados AGN de baja luminosidad.

  4. Red AGN in XMM-Newton/SDSS fields

    CERN Document Server

    Georgakakis, A; Akylas, A

    2006-01-01

    In this paper we combine archival and proprietary XMM-Newton observations (about 5deg^2) that overlap with the Sloan Digital Sky Survey to explore the nature of the moderate-z X-ray population. We focus on X-ray sources with optically red colours (g-r>0.4), which we argue are important for understanding the origin of the X-ray background. Firstly, these systems constitute a significant fraction, about 2/3, of the z1e22 cm^{-2}) and unobscured (N_H2mag) AGNs identified in the Two Micron All Sky Survey (2MASS). The median N_H of the red X-ray sources studied here is ~1e21cm^{-2}, lower than that found for the 2MASS AGNs, suggesting different populations.

  5. Exploring Multiwavelength AGN Variability with Swift Archival Data

    CERN Document Server

    Gelbord, Jonathan; Grupe, Dirk; Berk, Dan Vanden; Wu, Jian

    2015-01-01

    We are conducting an archival Swift program to measure multiwavelength variability in active galactic nuclei (AGN). This variability information will provide constraints on the geometry, physical conditions and processes of the structures around the central black holes that emit and reprocess the observed flux. Among our goals are: (1) to produce a catalog of type 1 AGN with time-resolved multi-wavelength data; (2) to characterize variability in the optical, UV and X-ay bands as well as changes in spectral slope; (3) to quantify the impact of variability on multi-wavelength properties; and (4) to measure correlated variability between bands. Our initial efforts have revealed a UVOT calibration issue that can cause a few percent of measured UV fluxes to be anomalously low, by up to 30%.

  6. Subgrid Modeling of AGN-Driven Turbulence in Galaxy Clusters

    CERN Document Server

    Scannapieco, Evan

    2008-01-01

    Hot, underdense bubbles powered by active galactic nuclei (AGN) are likely to play a key role in halting catastrophic cooling in the centers of cool-core galaxy clusters. We present three-dimensional simulations that capture the evolution of such bubbles, using an adaptive-mesh hydrodynamic code, FLASH3, to which we have added a subgrid model of turbulence and mixing. While pure-hydro simulations indicate that AGN bubbles are disrupted into resolution-dependent pockets of underdense gas, proper modeling of subgrid turbulence indicates that this a poor approximation to a turbulent cascade that continues far beyond the resolution limit. Instead, Rayleigh-Taylor instabilities act to effectively mix the heated region with its surroundings, while at the same time preserving it as a coherent structure, consistent with observations. Thus bubbles are transformed into hot clouds of mixed material as they move outwards in the hydrostatic intracluster medium (ICM), much as large airbursts lead to a distinctive ``mushroo...

  7. Solving the Cooling Flow Problem through Mechanical AGN Feedback

    CERN Document Server

    Gaspari, M; Ruszkowski, M

    2012-01-01

    Unopposed radiative cooling of plasma would lead to the cooling catastrophe, a massive inflow of condensing gas, manifest in the core of galaxies, groups and clusters. The last generation X-ray telescopes, Chandra and XMM, have radically changed our view on baryons, indicating AGN heating as the balancing counterpart of cooling. This work reviews our extensive investigation on self-regulated heating. We argue that the mechanical feedback, based on massive subrelativistic outflows, is the key to solving the cooling flow problem, i.e. dramatically quenching the cooling rates for several Gyr without destroying the cool-core structure. Using a modified version of the 3D hydrocode FLASH, we show that bipolar AGN outflows can further reproduce fundamental observed features, such as buoyant bubbles, weak shocks, metals dredge- up, and turbulence. The latter is an essential ingredient to drive nonlinear thermal instabilities, which cause the formation of extended cold gas, a residual of the quenched cooling flow and,...

  8. Parsec-Scale Jet-Environment Interactions in AGN

    CERN Document Server

    Lister, Matthew L

    2007-01-01

    Observations made with the VLBA have led to fundamental advances in our understanding of how radio jets in AGN evolve from parsec-scales out to distances exceeding several hundred kiloparsecs. In this review I discuss current models of young radio source evolution, as well as the observational evidence for a rapid change in jet properties on scales of ~1 kpc. A central topic of current debate is the relative importance of intermittent jet fueling versus jet-environment interactions in causing a drop-off in powerful radio sources at this critical evolutionary stage. Recent 3-D hydrodynamical jet simulations suggest that dense environments and cloud collisions can temporarily stifle, but not completely halt powerful relativistic jets. Several VLBA studies of jet-ISM interactions in both blazars and weak Seyfert jets have indicated that collimated outflows are indeed possible in dense environments. At present, the bulk of the evidence favors intermittent AGN accretion as the dominant factor in determining the ev...

  9. Pyrometric fuel particle measurements in pressurised reactors

    Energy Technology Data Exchange (ETDEWEB)

    Hernberg, R.; Joutsenoja, T. [Tampere Univ. of Technology (Finland)

    1996-12-01

    A fiberoptic two-colour pyrometric technique for fuel particle temperature and size measurement is modified and applied to three pressurized reactors of different type in Finland, Germany and France. A modification of the pyrometric method for simultaneous in situ measurement of the temperature and size of individual pulverized coal particles at the pressurized entrained flow reactor in Jyvaeskylae was developed and several series of measurements were made. In Orleans a fiberoptic pyrometric device was installed to a pressurised thermogravimetric reactor and the two-colour temperatures of fuel samples were measured. Some results of these measurements are presented. The project belongs to EU`s Joule 2 extension research programme. (author)

  10. Dissecting Galaxies: Spatial and Spectral Separation of Emission Excited by Star Formation and AGN Activity

    CERN Document Server

    Davies, Rebecca L; Kewley, Lisa J; Dopita, Michael A; Hampton, Elise J; Shastri, Prajval; Scharwachter, Julia; Sutherland, Ralph; Kharb, Preeti; Bhatt, Harish; Jin, Chichuan; Banfield, Julie; Zaw, Ingyin; James, Bethan; Juneau, Stephanie; Srivastava, Shweta

    2016-01-01

    The optical spectra of Seyfert galaxies are often dominated by emission lines excited by both star formation and AGN activity. Standard calibrations (such as for the star formation rate) are not applicable to such composite (mixed) spectra. In this paper, we describe how integral field data can be used to spectrally and spatially separate emission associated with star formation from emission associated with accretion onto an active galactic nucleus (AGN). We demonstrate our method using integral field data for two AGN host galaxies (NGC 5728 and NGC 7679) from the Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7). The spectra of NGC 5728 and NGC 7679 form clear sequences of AGN fraction on standard emission line ratio diagnostic diagrams. We show that the emission line luminosities of the majority (> 85 per cent) of spectra along each AGN fraction sequence can be reproduced by linear superpositions of the emission line luminosities of one AGN dominated spectrum and one star formation dominated...

  11. Variability-based AGN selection using image subtraction in the SDSS and LSST era

    CERN Document Server

    Choi, Yumi; Becker, Andrew C; Ivezić, \\vZeljko; Connolly, Andrew J; MacLeod, Chelsea L; Ruan, John J; Anderson, Scott F

    2013-01-01

    With upcoming all sky surveys such as LSST poised to generate a deep digital movie of the optical sky, variability-based AGN selection will enable the construction of highly-complete catalogs with minimum contamination. In this study, we generate $g$-band difference images and construct light curves for QSO/AGN candidates listed in SDSS Stripe 82 public catalogs compiled from different methods, including spectroscopy, optical colors, variability, and X-ray detection. Image differencing excels at identifying variable sources embedded in complex or blended emission regions such as Type II AGNs and other low-luminosity AGNs that may be omitted from traditional photometric or spectroscopic catalogs. To separate QSOs/AGNs from other sources using our difference image light curves, we explore several light curve statistics and parameterize optical variability by the characteristic damping timescale ($\\tau$) and variability amplitude. By virtue of distinguishable variability parameters of AGNs, we are able to select...

  12. Observational constraints on viscosity in AGN accretion discs

    Energy Technology Data Exchange (ETDEWEB)

    Siemiginowska, A.; Czerny, B. (N. Copernicus Astronomical Centre, Warsaw (Poland))

    1989-07-15

    The optical/UV/soft X-ray big bump can be modelled as thermal emission from an accretion disc. The observed UV variability in AGN spectra may be caused by accretion-disc instabilities, and can be used to constrain the viscosity. The comparison of thermal time-scales with the observed time-scales of variability in 10 Seyfert galaxies and 16 QSOs indicates values for the parameter {alpha} of the order of 0.01 for most cases. (author).

  13. AGN Jet Kinematics on Parsec-Scales: The MOJAVE Program

    Directory of Open Access Journals (Sweden)

    Matthew Lister

    2016-09-01

    Full Text Available Very long baseline interferometry offers the best means of investigating the complex dynamics of relativistic jets powered by active galactic nuclei, via multi-epoch, sub-milliarcsecond, full-polarization imaging at radio wavelengths. Although targeted studies have yielded important information on the structures of individual AGN jets, the strong selection effects associated with relativistically beaming imply that general aspects of the flows can only be determined via large statistical studies. In this review I discuss major results from the Monitoring of Jets in Active Galactic Nuclei With VLBA Experiments (MOJAVE program, which has gathered multi-epoch Very Long Baseline Array (VLBA data at 15 GHz on over 400 AGN jets over the course of two decades. The sample is large enough to encompass a range of AGN optical class, radio luminosity and synchrotron peak frequency, and has been used to show that within a particular jet, individual bright features have a spread of apparent speed and velocity vector position angle about a characteristic value. We have found that in some cases there is a secular evolution of launch angle direction over time, indicative of evolving narrow energized channels within a wider outflow. The majority of the jet features are superluminal and accelerating, with changes in speed more common than changes in direction. Within approximately 100 pc of the AGN, the flows are generally accelerating, while beyond this distance the flows begin to decelerate or remain nearly constant in speed. We also find evidence for a maximum bulk flow Lorentz factor of 50 in the pc-scale radio regime, and a trend of higher jet speeds in lower-synchrotron peaked and gamma-ray-loud blazars.

  14. Reactor and method of operation

    Science.gov (United States)

    Wheeler, John A.

    1976-08-10

    A nuclear reactor having a flattened reactor activity curve across the reactor includes fuel extending over a lesser portion of the fuel channels in the central portion of the reactor than in the remainder of the reactor.

  15. Probing the central parsecs of AGN using Faraday Rotation

    Science.gov (United States)

    Zavala, R. T.; Taylor, G. B.

    2002-05-01

    A broad frequency range and low instrumental polarization makes the Very Long Baseline Array (VLBA) an ideal instrument for studying polarimetry at sub-milliarcsecond resolution. To take advantage of these unique capabilities we have conducted a multi-frequency polarization survey of 40 radio-loud AGN (Quasars, BL Lacs, and radio galaxies). Our aim is to use Faraday Rotation Measures (RMs) as a probe of the central 1-50 parsecs of these objects. The RM is produced by the line of sight magnetic field weighted by the electron density. Using the electron density established through spectral line diagnostics a magnetic field strength and topology can be estimated within a few parsecs of the central engines of these AGN. The observations for the survey are complete, and we present the first results for 8 quasars, 5 BL Lacs, and 4 radio galaxies. The magnitudes for the RMs range from several thousand rad m-2 in the quasars and radio galaxies to a few hundred rad m-2 in the BL Lac objects. These values are in agreement with the basic ideas of the unified model for AGN. We also observe variations in the RM on small spatial (time scales ( ~ 6 months) in the quasars 3C 273 and 3C 279. R.T.Z. gratefully acknowledges support from a pre-doctoral research appointment at NRAO and from the New Mexico Alliance for Graduate Education and the Professiorate through NSF grant HRD-0086701.

  16. Evidence that most type 1 AGN are reddened by dust

    CERN Document Server

    Baron, Dalya; Poznanski, Dovi; Netzer, Hagai

    2016-01-01

    The typical optical-UV continuum slopes observed in many type 1 active galactic nuclei (AGN) are redder than expected from thin accretion disk models. A possible resolution to this conundrum is that many AGN are reddened by dust along the line of sight. To explore this possibility, we stack 5000 SDSS AGN with luminosity L ~ 10^45 erg/s and redshift z ~ 0.4 in bins of optical continuum slope alpha_opt and width of the broad Hbeta emission line. We measure the equivalent width (EW) of the NaID absorption feature in each stacked spectrum. We find a linear relation between alpha_opt and EW(NaID), such that EW(NaID) increases as alpha_opt becomes redder. In the bin with the smallest Hbeta width, objects with the bluest slopes that are similar to accretion disk predictions are found to have EW(NaID) = 0, supporting the line-of-sight dust hypothesis. This conclusion is also supported by the dependence of the Halpha/Hbeta line ratio on alpha_opt. The implied relationship between continuum slope and dust reddening is ...

  17. The Baldwin effect in the narrow emission lines of AGNs

    CERN Document Server

    Zhang, Kai; Gaskell, C Martin; Dong, Xiao-Bo

    2012-01-01

    The anti-correlations between the equivalent widths of emission lines and the continuum luminosity in AGNs, known as the Baldwin effect are well established for broad lines, but are less well studied for narrow lines. In this paper we explore the Baldwin effect of narrow emission lines over a wide range of ionization levels and critical densities using a large sample of broad-line, radio-quiet AGNs taken from Sloan Digital Sky Survey (SDSS) Data Release 4. These type1 AGNs span three orders of magnitude in continuum luminosity. We show that most narrow lines show a similar Baldwin effect slope of about -0.2 while the significant deviations of the slopes for [NII] 6583, [OII] 3727, [NeV] 3425, and the narrow component of Ha can be explained by the influence of metallicity, star-formation contamination and possibly by difference in the shape of the UV-optical continuum. The slopes do not show any correlation with either the ionization potential or the critical density. We show that a combination of 50% variatio...

  18. Disk Outflows and High-Luminosity True Type 2 AGN

    CERN Document Server

    Elitzur, Moshe

    2016-01-01

    The absence of intrinsic broad line emission has been reported in a number of active galactic nuclei (AGN), including some with high Eddington ratios. Such "true type 2 AGN" are inherent to the disk-wind scenario for the broad line region: Broad line emission requires a minimal column density, implying a minimal outflow rate and thus a minimal accretion rate. Here we perform a detailed analysis of the consequences of mass conservation in the process of accretion through a central disk. The resulting constraints on luminosity are consistent with all the cases where claimed detections of true type 2 AGN pass stringent criteria, and predict that intrinsic broad line emission can disappear at luminosities as high as about 4x$10^{46}$ erg s$^{-1}$ and any Eddington ratio, though more detections can be expected at Eddington ratios below about 1%. Our results are applicable to every disk outflow model, whatever its details and whether clumpy or smooth, irrespective of the wind structure and its underlying dynamics. ...

  19. A Search for AGN Intra-day Variability with KVN

    CERN Document Server

    Lee, Taeseok; Oh, Junghwan; Byun, Do-Young; Sohn, Bong-Won; Lee, Sang-Sung

    2015-01-01

    Active galactic nuclei (AGN) are known for irregular variability on all time scales, down to intra-day variability with relative variations of a few percent within minutes to hours. On such short timescales, unexplored territory, such as the possible existence of a shortest characteristic time scale of activity and the shape of the high frequency end of AGN power spectra, still exists. We present the results of AGN single-dish fast photometry performed with the Korean VLBI Network (KVN). Observations were done in a "anti-correlated" mode using two antennas, with always at least one antenna pointing at the target. This results in an effective time resolution of less than three minutes. We used all four KVN frequencies, 22, 43, 86, and 129 GHz, in order to trace spectral variability, if any. We were able to derive high-quality light curves for 3C 111, 3C 454.3, and BL Lacertae at 22 and 43 GHz, and for 3C 279 at 86 GHz, between May 2012 and April 2013. We performed a detailed statistical analysis in order to as...

  20. Gamma-Rays from Non-Blazar AGN

    CERN Document Server

    Rieger, Frank M

    2016-01-01

    Non-blazar Active Galactic Nuclei (AGN) have emerged as a new gamma-ray emitting source class on the extragalactic sky and started to deepen our understanding of the physical processes and the nature of AGN in general. The detection of Narrow Line Seyfert 1 galaxies in the Fermi-LAT energy regime, for example, offers important information for our understanding of jet formation and radio-loudness. Radio galaxies, on the other hand, have become particularly interesting at high (HE) and very high (VHE) gamma-ray energies. With their jets not directly pointing towards us (i.e. misaligned), they offer a unique tool to probe into the nature of the fundamental (and often hidden) physical processes in AGN. This review highlights and discusses some of the observational and theoretical progress achieved in the gamma-ray regime during recent years, including the evidence for unexpected spectral hardening in Centaurus A and extreme short-term variability as seen in IC 310 and M87.

  1. AGN-stimulated Cooling of Hot Gas in Elliptical Galaxies

    CERN Document Server

    Valentini, Milena

    2015-01-01

    We study the impact of relatively weak AGN feedback on the interstellar medium of intermediate and massive elliptical galaxies. We find that the AGN activity, while globally heating the ISM, naturally stimulates some degree of hot gas cooling on scales of several kpc. This process generates the persistent presence of a cold ISM phase, with mass ranging between 10$^4$ and $\\gtrsim$ 5 $\\times$ 10$^7$ M$_\\odot$, where the latter value is appropriate for group centered, massive galaxies. Widespread cooling occurs where the ratio of cooling to free-fall time before the activation of the AGN feedback satisfies $t_{cool}/t_{ff} \\lesssim 70$, that is we find a less restrictive threshold than commonly quoted in the literature. This process helps explaining the body of observations of cold gas (both ionized and neutral/molecular) in Ellipticals and, perhaps, the residual star formation detected in many early-type galaxies. The amount and distribution of the off-center cold gas vary irregularly with time. The cold ISM v...

  2. AGN Outflow Shocks on Bonnor-Ebert Spheres

    CERN Document Server

    Dugan, Zachary; Bieri, Rebekka; Silk, Joseph; Rahman, Mubdi

    2016-01-01

    Feedback from Active Galactic Nuclei (AGN) and subsequent jet cocoons and outflow bubbles can have a significant impact on star formation in the host galaxy. To investigate feedback physics on small scales, we perform hydrodynamic simulations of realistically fast AGN winds striking Bonnor-Ebert (BE) spheres and examine gravitational collapse and ablation. We test AGN wind velocities ranging from 300--3,000 km s$^{-1}$ and wind densities ranging from 0.5--10 $m_\\mathrm{p}\\,\\mathrm{cm}^{-3}$. We include heating and cooling of low- and high-temperature gas, self-gravity, and spatially correlated perturbations in the shock, with a maximum resolution of 0.01 pc. We find that the ram pressure is the most important factor that determines the fate of the cloud. High ram pressure winds increase fragmentation and decrease the star formation rate, but also cause star formation to occur on a much shorter time scale and with increased velocities of the newly formed stars. We find a threshold ram pressure of $\\sim 2\\times...

  3. AGN feedback drives the colour evolution of local galaxies

    CERN Document Server

    Shabala, Stanislav S; Silk, Joseph

    2011-01-01

    We investigate the effects of AGN feedback on the colour evolution of galaxies found in local (z<0.2) groups and clusters. Galaxies located within the lobes of powerful Fanaroff-Riley type II (edge-brightened) sources show much redder colours than neighbouring galaxies that are not spatially coincident with the radio source. By contrast, no similar effect is seen near Fanaroff-Riley type I (core-dominated) radio sources. We show that these colours are consistent with FR-IIs truncating star formation as the expanding bow shock overruns a galaxy. We examine a sample of clusters with no detectable radio emission and show that galaxy colours in these clusters carry an imprint of past AGN feedback. AGN activity in the low-redshift Universe is predominantly driven by low-luminosity radio sources with short duty cycles. Our results show that, despite their rarity, feedback from powerful radio sources is an important driver of galaxy evolution even in the local volume.

  4. A Compton thick AGN in the barred spiral NGC 4785

    CERN Document Server

    Gandhi, P; Ricci, C; Asmus, D; Mushotzky, R F; Ueda, Y; Terashima, Y; La Parola, V

    2014-01-01

    We present X-ray observations of the active galactic nucleus (AGN) in NGC 4785. The source is a local Seyfert 2 which has not been studied so far in much detail. It was recently detected with high significance in the 15-60 keV band in the 66 month Swift/BAT all sky survey, but there have been no prior pointed X-ray observations of this object. With Suzaku, we clearly detect the source below 10 keV, and find it to have a flat continuum and prominent neutral iron fluorescence line with equivalent width >~1 keV. Fitting the broadband spectra with physical reflection models shows the source to be a bona fide Compton thick AGN with Nh of at least 2x10^{24} cm^{-2} and absorption-corrected 2-10 keV X-ray power L(2-10) ~ few times 10^{42} erg s^{-1}. Realistic uncertainties on L(2-10) computed from the joint confidence interval on the intrinsic power law continuum photon index and normalization are at least a factor of 10. The local bona fide Compton thick AGN population is highly heterogeneous in terms of WISE mid-...

  5. Astrometric Evidence for a Population of Dislodged AGNs

    Science.gov (United States)

    Makarov, Valeri V.; Frouard, Julien; Berghea, Ciprian T.; Rest, Armin; Chambers, Kenneth C.; Kaiser, Nicholas; Kudritzki, Rolf-Peter; Magnier, Eugene A.

    2017-02-01

    We investigate a sample of 2293 ICRF2 extragalactic radio-loud sources with accurate positions determined by VLBI, mostly active galactic nuclei (AGNs) and quasars, which are cross-matched with optical sources in the first Gaia release (Gaia DR1). The distribution of offsets between the VLBI sources and their optical counterparts is strongly non-Gaussian, with powerful wings extending beyond 1 arcsec. Limiting our analysis to only high-confidence difference detections, we find (and publish) a list of 188 objects with normalized variances above 12 and offsets below 1 arcsec. Pan-STARRS stacked and monochromatic images resolve some of these sources, indicating the presence of double sources, confusion sources, or pronounced extended structures. Some 89 high-quality objects, however, do not show any perturbations and appear to be star-like single sources, yet they are displaced by multiples of the expected error from the radio-loud AGN. We conclude that a fraction of luminous AGNs (more than 4%) can be physically dislodged from the optical centers of their parent galaxies.

  6. Is AGN feedback necessary to form red elliptical galaxies?

    CERN Document Server

    Khalatyan, A; Schramm, M; Gottlöber, S; Steinmetz, M; Wisotzki, L

    2007-01-01

    We have used GADGET2 to simulate the formation of an elliptical galaxy in a cosmological dark matter halo with mass 3x10^12M_Sun/h. Using a stellar population synthesis model has allowed us to compute magnitudes, colours and surface brightness profiles. We have included a model to follow the growth of a central black hole and we have compared the results of simulations with and without feedback from AGNs. We have studied the interplay between cold gas accretion and merging in the development of galactic morphologies, the link between colour and morphology evolution, the effect of AGN feedback on the photometry of early type galaxies, the redshift evolution in the properties of quasar hosts, and the impact of AGN winds on the chemical enrichment of the intergalactic medium (IGM). We have found that the early phases of galaxy formation are driven by the accretion of cold filamentary flows, which form a disc at the centre of the dark matter halo. When the dark matter halo is sufficiently massive to support the p...

  7. Modeling AGN outbursts from supermassive black hole binaries

    Directory of Open Access Journals (Sweden)

    Tanaka T.

    2012-12-01

    Full Text Available When galaxies merge to assemble more massive galaxies, their nuclear supermassive black holes (SMBHs should form bound binaries. As these interact with their stellar and gaseous environments, they will become increasingly compact, culminating in inspiral and coalescence through the emission of gravitational radiation. Because galaxy mergers and interactions are also thought to fuel star formation and nuclear black hole activity, it is plausible that such binaries would lie in gas-rich environments and power active galactic nuclei (AGN. The primary difference is that these binaries have gravitational potentials that vary – through their orbital motion as well as their orbital evolution – on humanly tractable timescales, and are thus excellent candidates to give rise to coherent AGN variability in the form of outbursts and recurrent transients. Although such electromagnetic signatures would be ideally observed concomitantly with the binary’s gravitational-wave signatures, they are also likely to be discovered serendipitously in wide-field, high-cadence surveys; some may even be confused for stellar tidal disruption events. I discuss several types of possible “smoking gun” AGN signatures caused by the peculiar geometry predicted for accretion disks around SMBH binaries.

  8. A Candidate Dual AGN at z=1.175

    CERN Document Server

    Barrows, R Scott; Madsen, Kristin; Harrison, Fiona; Assef, Roberto J; Comerford, Julia M; Cushing, Michael C; Fassnacht, Christopher D; Gonzalez, Anthony; Griffith, Roger; Hickox, Ryan; Kirkpatrick, J Davy; Lagattuta, David J

    2011-01-01

    The X-ray source CXOXBJ142607.6+353351 (CXOJ1426+35), which was identified in a 172 ks Chandra image in the Bootes field, shows double-peaked rest-frame optical/UV emission lines, separated by 0.69" (5.5 kpc) in the spatial dimension and by 690 km s^-1 in the velocity dimension. The high excitation lines and emission line ratios indicate both systems are ionized by an AGN continuum, and the double-peaked profile resembles that of candidate dual AGN. At a redshift of z=1.175, this source is the highest redshift candidate dual AGN yet identified. However, many sources have similar emission line profiles for which other interpretations are favored. We have analyzed the substantial archival data available in this field, as well as acquired near-infrared (NIR) adaptive optics (AO) imaging and NIR slit spectroscopy. The X-ray spectrum is hard, implying a column density of several 10^23 cm^-2. Though heavily obscured, the source is also one of the brightest in the field, with an absorption-corrected 2-10 keV luminos...

  9. The Radiative Efficiency of Accretion Flows in Individual AGN

    CERN Document Server

    Davis, Shane W

    2010-01-01

    The radiative efficiency of AGN is commonly estimated based on the total mass accreted and the total AGN light emitted per unit volume in the universe integrated over time (the Soltan argument). In individual AGN, thin accretion disk model spectral fits can be used to deduce the absolute accretion rate Mdot, if the black hole mass M is known. The radiative efficiency {\\eta} is then set by the ratio of the bolometric luminosity L_bol to Mdot c^2. We apply this method to determine {\\eta} in a sample of 80 PG quasars with well determined L_bol, where Mdot is set by thin accretion disk model fits to the optical luminosity density, and the M determination based on the bulge stellar velocity dispersion (13 objects) or the broad line region (BLR). For the BLR-based masses, we derive a mean log {\\eta} = -1.05 +/- 0.52 consistent with the Soltan argument based estimates. We find a strong correlation of {\\eta} with M, rising from {\\eta} ~ 0.03 at M = 10^7 M{\\odot} and L/L_Edd ~ 1 to {\\eta} ~ 0.4 at M = 10^9 M{\\odot} an...

  10. AGN Heating in Simulated Cool-Core Clusters

    CERN Document Server

    Li, Yuan; Bryan, Greg L

    2016-01-01

    We analyze heating and cooling processes in an idealized simulation of a cool-core cluster, where momentum-driven AGN feedback balances radiative cooling in a time-averaged sense. We find that, on average, energy dissipation via shock waves is almost an order of magnitude higher than via turbulence. Most of the shock waves in the simulation are very weak shocks with Mach numbers smaller than 1.5, but the stronger shocks, although rare, dissipate energy more effectively. We find that shock dissipation is a steep function of radius, with most of the energy dissipated within 30 kpc, while radiative cooling loses area less concentrated. However, adiabatic processes and mixing (of post-shock materials and the surrounding gas) are able to redistribute the heat throughout the core. A considerable fraction of the AGN energy also escapes the core region. The cluster goes through cycles of AGN outbursts accompanied by periods of enhanced precipitation and star formation, over Gyr timescales. The cluster core is under-h...

  11. Observational evidence for AGN feedback in early-type galaxies

    CERN Document Server

    Schawinski, Kevin; Sarzi, Marc; Maraston, Claudia; Kaviraj, Sugata; Joo, Seok-Joo; Yi, Sukyoung K; Silk, Joseph

    2007-01-01

    A major amendment in recent models of hierarchical galaxy formation is the inclusion of so-called AGN feedback. The energy input from an active central massive black hole is invoked to suppress star formation in early-type galaxies at later epochs. A major problem is that this process is poorly understood, and compelling observational evidence for its mere existence is still missing. In search for signatures of AGN feedback, we have compiled a sample of 16,000 early-type galaxies in the redshift range 0.05AGN are located considerably closer to and almost on the red sequence. S...

  12. Inverse Compton X-ray signature of AGN feedback

    CERN Document Server

    Bourne, Martin A

    2013-01-01

    Bright AGN frequently show ultra-fast outflows (UFOs) with outflow velocities vout ! 0.1c. These outflows may be the source of AGN feedback on their host galaxies sought by galaxy formation modellers. The exact effect of the outflows on the ambient galaxy gas strongly depends on whether the shocked UFOs cool rapidly or not. This in turn depends on whether the shocked electrons share the same temperature as ions (one temperature regime; 1T) or decouple (2T), as has been recently suggested. Here we calculate the Inverse Compton spectrum emitted by such shocks, finding a broad feature potentially detectable either in mid-to-high energy X-rays (1T case) or only in the soft X-rays (2T). We argue that current observations of AGN do not seem to show evidence for the 1T component, while the limits on the 2T emission are far weaker. This suggests that UFOs are in the energy-driven regime outside the central few pc, and must pump considerable amounts of not only momentum but also energy into the ambient gas. We encoura...

  13. The Detectability of AGN Cavities in Cooling-Flow Clusters

    CERN Document Server

    Birzan, L; McNamara, B R; Nulsen, P E J; Wise, M W

    2009-01-01

    Chandra X-ray Observatory has revealed X-ray cavities in many nearby cooling flow clusters. The cavities trace feedback from the central active galactic nulceus (AGN) on the intracluster medium (ICM), an important ingredient in stabilizing cooling flows and in the process of galaxy formation and evolution. But, the prevalence and duty cycle of such AGN outbursts is not well understood. To this end, we study how the cooling is balanced by the cavity heating for a complete sample of clusters (the Brightest 55 clusters of galaxies, hereafter B55). In the B55, we found 33 cooling flow clusters, 20 of which have detected X-ray bubbles in their ICM. Among the remaining 13, all except Ophiuchus could have significant cavity power yet remain undetected in existing images. This implies that the duty cycle of AGN outbursts with significant heating potential in cooling flow clusters is at least 60 % and could approach 100 %, but deeper data is required to constrain this further.

  14. Revisiting Stochastic Variability of AGNs with Structure Functions

    CERN Document Server

    Kozłowski, Szymon

    2016-01-01

    Discrepancies between reported structure function (SF) slopes and their overall flatness as compared to expectations from the damped random walk (DRW) model, generally well-describing the variability of active galactic nuclei (AGN), has triggered us to study this problem in detail. We review common AGN variability observables and identify their most common problems. Equipped with this knowledge, we study ~9000 r-band AGN light curves from Stripe 82 of the Sloan Digital Sky Survey, using SFs described by stochastic processes with the power exponential covariance matrix of the signal. We model the "sub-ensemble" SFs in the redshift-absolute magnitude bins with the full SF equation (including the turnover and the noise part) and a single power-law (SPL; in the "red noise regime" after subtracting the noise term). The distribution of full-equation SF (SPL) slopes peaks at gamma=0.55+/-0.08 (0.52+/-0.06) and is consistent with DRW. There is a hint of a weak correlation of gamma with the luminosity and a lack of co...

  15. EVN observations of low-luminosity flat-spectrum AGNs

    CERN Document Server

    Caccianiga, A; Thean, A; Dennett-Thorpe, J

    2001-01-01

    We present and discuss the results of VLBI (EVN) observations of three low-luminosity (P(5 GHz)<10^25 W/Hz) Broad Emission Line AGNs carefully selected from a sample of flat spectrum radio sources (CLASS). Based on the total and the extended radio power at 5 GHz and at 1.4 GHz respectively, these objects should be technically classified as radio-quiet AGN and thus the origin of their radio emission is not clearly understood. The VLBI observations presented in this paper have revealed compact radio cores which imply a lower limit on the brightness temperature of about 3X10^8 K. This result rules out a thermal origin for the radio emission and strongly suggests an emission mechanism similar to that observed in more powerful radio-loud AGNs. Since, by definition, the three objects show a flat (or inverted) radio spectrum between 1.4 GHz and 8.4 GHz, the observed radio emission could be relativistically beamed. Multi-epoch VLBI observations can confirm this possibility in two years time.

  16. Compton reflection in AGN with Simbol-X

    CERN Document Server

    Beckmann, V; Gehrels, N; Lubinski, P; Malzac, J; Petrucci, P O; Shrader, C R; Soldi, S

    2009-01-01

    AGN exhibit complex hard X-ray spectra. Our current understanding is that the emission is dominated by inverse Compton processes which take place in the corona above the accretion disk, and that absorption and reflection in a distant absorber play a major role. These processes can be directly observed through the shape of the continuum, the Compton reflection hump around 30 keV, and the iron fluorescence line at 6.4 keV. We demonstrate the capabilities of Simbol-X to constrain complex models for cases like MCG-05-23-016, NGC 4151, NGC 2110, and NGC 4051 in short (10 ksec) observations. We compare the simulations with recent observations on these sources by INTEGRAL, Swift and Suzaku. Constraining reflection models for AGN with Simbol-X will help us to get a clear view of the processes and geometry near to the central engine in AGN, and will give insight to which sources are responsible for the Cosmic X-ray background at energies above 20 keV.

  17. agnes b.曾经的诗意

    Institute of Scientific and Technical Information of China (English)

    于晓丹

    2013-01-01

    从前的agnes b.常常在我无以言辞时替我表达,像诗一样。秋天总有忧伤的日子,不过女人们在忧伤时穿得常常更为诗意。比如那天,我要去见一位十几年不见的男性朋友,穿上本白色薄丝衬衫、套上驼色羊毛衫后,从衣橱里拣出了那件在深处挂了十年的agnes b锈红色齐踝厚呢大衣。出门的一瞬,感觉天空的蓝凛冽而透彻,云像奔腾的马,快速地往北飘移而去。作为女人,我一直相信服装的款式、手感和色彩能够诉说情感,启发对生活的想象力。从前的agnes b常常在我无以言辞时替我表达,像诗一样。

  18. How AGN feedback and metal cooling shape cluster entropy profiles

    CERN Document Server

    Dubois, Yohan; Teyssier, Romain; Slyz, Adrianne

    2011-01-01

    Observed clusters of galaxies essentially come in two flavors: non cool core clusters characterized by an isothermal temperature profile and a central entropy floor, and cool-core clusters where temperature and entropy in the central region are increasing with radius. Using cosmological resimulations of a galaxy cluster, we study the evolution of its intracluster medium (ICM) gas properties, and through them we assess the effect of different (sub-grid) modelling of the physical processes at play, namely gas cooling, star formation, feedback from supernovae and active galactic nuclei (AGN). More specifically we show that AGN feedback plays a major role in the pre-heating of the proto-cluster as it prevents a high concentration of mass from collecting in the center of the future galaxy cluster at early times. However, AGN activity during the cluster's later evolution is also required to regulate the mass flow into its core and prevent runaway star formation in the central galaxy. Whereas the energy deposited by...

  19. Bar effects on central star formation and AGN activity

    CERN Document Server

    Oh, Seulhee; Yi, Sukyoung K

    2011-01-01

    Galactic bars are often suspected to be a channel of gas inflow to the galactic center and trigger central star formation and active galactic nuclei (AGN) activity. However, the current status on this issue based on empirical studies is unsettling, especially on AGN. We investigate this question based on the Sloan Digital Sky Survey (SDSS) Data Release 7. From the nearby (0.01 < z < 0.05) bright (Mr < -19) database, we have constructed a sample of 6,658 relatively face-on late-type galaxies through visual inspection. We found 36% of them to have a bar. Bars are found to be more common in galaxies with earlier morphology. This makes sample selection critical. Parameter-based selections would miss a large fraction of barred galaxies of early morphology. Bar effects on star formation or AGN are difficult to understand properly because multiple factors (bar frequency, stellar mass, black-hole mass, gas contents, etc.) seem to contribute to them in intricate manners. In the hope of breaking these degenera...

  20. Evidence for AGN Feedback in Galaxy Clusters and Groups

    Directory of Open Access Journals (Sweden)

    Myriam Gitti

    2012-01-01

    Full Text Available The current generation of flagship X-ray missions, Chandra and XMM-Newton, has changed our understanding of the so-called “cool-core” galaxy clusters and groups. Instead of the initial idea that the thermal gas is cooling and flowing toward the center, the new picture envisages a complex dynamical evolution of the intracluster medium (ICM regulated by the radiative cooling and the nongravitational heating from the active galactic nucleus (AGN. Understanding the physics of the hot gas and its interplay with the relativistic plasma ejected by the AGN is key for understanding the growth and evolution of galaxies and their central black holes, the history of star formation, and the formation of large-scale structures. It has thus become clear that the feedback from the central black hole must be taken into account in any model of galaxy evolution. In this paper, we draw a qualitative picture of the current knowledge of the effects of the AGN feedback on the ICM by summarizing the recent results in this field.

  1. Sweeping Away the Mysteries of Dusty Continuous Winds in AGN

    CERN Document Server

    Keating, S K; Gallagher, S C; Deo, R P

    2012-01-01

    An integral part of the Unified Model for Active Galactic Nuclei (AGNs) is an axisymmetric obscuring medium, which is commonly depicted as a torus of gas and dust surrounding the central engine. However, a robust, dynamical model of the torus is required in order to understand the fundamental physics of AGNs and interpret their observational signatures. Here we explore self-similar, dusty disk-winds, driven by both magnetocentrifugal forces and radiation pressure, as an explanation for the torus. Using these models, we make predictions of AGN infrared (IR) spectral energy distributions (SEDs) from 2-100 microns by varying parameters such as: the viewing angle; the base column density of the wind; the Eddington ratio; the black hole mass; and the amount of power in the input spectrum emitted in the X-ray relative to that emitted in the UV/optical. We find that models with N_H,0 = 10^25 cm^-2, L/L_Edd = 0.1, and M_BH >= 10^8 Msun are able to adequately approximate the general shape and amount of power expected ...

  2. Evidence for AGN Feedback in Galaxy Clusters and Groups

    CERN Document Server

    Gitti, Myriam; McNamara, Brian R

    2011-01-01

    The current generation of flagship X-ray missions, Chandra and XMM-Newton, has changed our understanding of the so-called "cool core" galaxy clusters and groups. Instead of the initial idea that the thermal gas is cooling and flowing toward the center, the new picture envisages a complex dynamical evolution of the intra-cluster medium (ICM) regulated by the radiative cooling and the nongravitational heating from the active galactic nucleus (AGN). Understanding the physics of the hot gas and its interplay with the relativistic plasma ejected by the AGN is key for understanding the growth and evolution of galaxies and their central black holes, the history of star formation, and the formation of large-scale structures. It has thus become clear that the feedback from the central black hole must be taken into account in any model of galaxy evolution. In this paper, we draw a qualitative picture of the current knowledge of the effects of the AGN feedback on the ICM by summarizing the recent results in this field.

  3. Triggering star formation by both radiative and mechanical AGN feedback

    Institute of Scientific and Technical Information of China (English)

    Chao Liu; Zhao-Ming Gan; Fu-Guo Xie

    2013-01-01

    We perform two dimensional hydrodynamic numerical simulations to study the positive active galactic nucleus (AGN) feedback which triggers,rather than suppresses,star formation.Recently,it was shown by Nayakshin et al.and Ishibashi et al.that star formation occurs when the cold interstellar medium (ISM) is squeezed by the impact of mass outflow or radiation pressure,respectively.Mass outflow is ubiquitous in this astrophysical context,and radiation pressure is also important if the AGN is luminous.For the first time in this subject,we incorporate both mass outflow feedback and radiative feedback into our model.Consequently,the ISM is shocked into shells by the AGN feedback,and these shells soon fragment into clumps and filaments because of Rayleigh-Taylor and thermal instabilities.We have two major findings:(1)the star formation rate can indeed be very large in the clumps and filaments.However,the resultant star formation rate density is too large compared with previous works,which is mainly because we ignore the fact that most of the stars that are formed would be disrupted when they move away from the galactic center.(2) Although radiation pressure feedback has a limited effect,when mass outflow feedback is also included,they reinforce each other.Specifically,in the gas-poor case,mass outflow is always the dominant contributor to feedback.

  4. Time Series

    OpenAIRE

    Gil-Alana, L.A.; Moreno, A; Pérez-de-Gracia, F. (Fernando)

    2011-01-01

    The last 20 years have witnessed a considerable increase in the use of time series techniques in econometrics. The articles in this important set have been chosen to illustrate the main themes in time series work as it relates to econometrics. The editor has written a new concise introduction to accompany the articles. Sections covered include: Ad Hoc Forecasting Procedures, ARIMA Modelling, Structural Time Series Models, Unit Roots, Detrending and Non-stationarity, Seasonality, Seasonal Adju...

  5. Three years of Swift/BAT Survey of AGN: Reconciling Theory and Observations?

    Energy Technology Data Exchange (ETDEWEB)

    Burlon, D.; /Garching, Max Planck Inst., MPE; Ajello, M.; /SLAC /KIPAC, Menlo Park; Greiner, J.; /Garching, Max Planck Inst., MPE; Comastri, A.; /Muenchen, Tech. U. Universe; Merloni, A.; /Garching, Max Planck Inst., MPE /Muenchen, Tech. U. Universe; Gehrels, N.; /NASA, Goddard

    2011-02-07

    It is well accepted that unabsorbed as well as absorbed AGN are needed to explain the nature and the shape of the Cosmic X-ray background, even if the fraction of highly absorbed objects (dubbed Compton-thick sources) substantially still escapes detection. We derive and analyze the absorption distribution using a complete sample of AGN detected by Swift-BAT in the first three years of the survey. The fraction of Compton-thick AGN represents only 4.6% of the total AGN population detected by Swift-BAT. However, we show that once corrected for the bias against the detection of very absorbed sources the real intrinsic fraction of Compton-thick AGN is 20{sub -6}{sup +9}%. We proved for the first time (also in the BAT band) that the anti-correlation of the fraction of absorbed AGN and luminosity it tightly connected to the different behavior of the luminosity functions (XLFs) of absorbed and unabsorbed AGN. This points towards a difference between the two subsamples of objects with absorbed AGN being, on average, intrinsically less luminous than unobscured ones. Moreover the XLFs show that the fraction of obscured AGN might also decrease at very low luminosity. This can be successfully interpreted in the framework of a disk cloud outflow scenario as the disappearance of the obscuring region below a critical luminosity. Our results are discussed in the framework of population synthesis models and the origin of the Cosmic X-ray Background.

  6. Possible evidence of destroying small PAH particles by radiation from AGNs

    Science.gov (United States)

    Feng, Qi-Chen; Wang, Jing; Wei, Jian-Yan

    2015-02-01

    The issue of destroying small polycyclic aromatic hydrocarbon (PAH) particles by radiation from AGNs is examined through optical narrow-emission line ratios of a sample of type II AGNs. We find that narrow-line ratios [OI]λ6300/Hα and [SII]λ6716, λ6731/Hα have prominent correlations with the PAH 11.3/7.7 ratio in our selected sample of AGNs. Because of the marginal (and in some cases no) dependence of the PAH ratio on the gas metallicity, a possible explanation for the correlations is the destruction of small PAH particles by the hard ionizing field associated with the AGNs.

  7. Hiding in Plain Sight - Recovering Clusters of Galaxies with the Strongest AGN in Their Cores

    CERN Document Server

    Green, T S; Ebeling, H; Burgett, W S; Draper, P W; Kaiser, N; Kudritzki, R -P; Magnier, E A; Metcalfe, N; Wainscoat, R J; Waters, C

    2016-01-01

    A key challenge in understanding the feedback mechanism of AGN in Brightest Cluster Galaxies (BCGs) is the inherent rarity of catching an AGN during its strong outburst phase. This is exacerbated by the ambiguity of differentiating between AGN and clusters in X-ray observations. If there is evidence for an AGN then the X-ray emission is commonly assumed to be dominated by the AGN emission, introducing a selection effect against the detection of AGN in BCGs. In order to recover these 'missing' clusters, we systematically investigate the colour-magnitude relation around some ~3500 ROSAT All Sky Survey selected AGN, looking for signs of a cluster red sequence. Amongst our 22 candidate systems, we independently rediscover several confirmed systems, where a strong AGN resides in a central galaxy. We compare the X-ray luminosity to red sequence richness distribution of our AGN candidate systems with that of a similarly selected comparison sample of ~1000 confirmed clusters and identify seven 'best' candidates (all ...

  8. AGN Feedback in Overdense Environments at z=2.23

    Science.gov (United States)

    Lucy, Adrian B.; Lehmer, B.; Alexander, D. M.; Best, P.; Geach, J.; Harrison, C. M.; Hornschemeier, A. E.; Matsuda, Y.; Mullaney, J.; Smail, I.; Sobral, D.

    2013-01-01

    We present results from a ≈100 ks Chandra observation of the 2QZ Cluster 1004+00 galaxy overdensity at z=2.23. This 2QZ Clus structure was first identified as an overdensity of four optically-selected quasars; that sample was subsequently found to overlap with an overdensity of 22 Hα-emitting galaxies (HAEs) identified through narrow and broad band near-infrared imaging by Matsuda et al. (2011). In addition to the preselected quasars in 2QZ Clus, our Chandra observation reveals that a further three HAEs are X-ray sources, all characterized by X-ray luminosities and spectral slopes consistent with unobscured active galactic nuclei (AGN). In total, we find that ≈30% of HAEs in our observed region of 2QZ Clus are AGN. This AGN fraction is high compared to AGN fractions among HAEs in the Chandra-COSMOS field (C-COSMOS), and if this enhancement is purely a result of the quasar selection bias of our sample, we estimate that such activity is rare at this redshift. Hα is a tracer of star formation, so 2QZ Clus is well suited to the investigation of the coeval growth of supermassive black holes and their host galaxies in the precursors to rich local clusters. Moreover, we have an ideal control sample in C-COSMOS; this survey contains a large sample of HAEs classified identically using infrared imaging, but without any selection of quasars. We calculate AGN fraction as a function of galaxy overdensity in C-COSMOS, and perform stacking analyses of Chandra and 250μ Herschel SPIRE data to obtain mean black hole accretion rates dMBH/dt and star formation rates SFR. Preliminary results indicate that dMBH/dt and its ratio to SFR are significantly elevated in 2QZ Clus compared to similarly overdense regions of C-COSMOS. We discuss these relations in the context of theoretical models describing the emergence of the MBH/Mgal relation of the local Universe.

  9. Series Bosch System Development

    Science.gov (United States)

    Abney, Morgan B.; Evans, Christopher; Mansell, Matt; Swickrath, Michael

    2012-01-01

    State-of-the-art (SOA) carbon dioxide (CO2) reduction technology for the International Space Station produces methane as a byproduct. This methane is subsequently vented overboard. The associated loss of hydrogen ultimately reduces the mass of oxygen that can be recovered from CO2 in a closed-loop life support system. As an alternative to SOA CO2 reduction technology, NASA is exploring a Series-Bosch system capable of reducing CO2 with hydrogen to form water and solid carbon. This results in 100% theoretical recovery of oxygen from metabolic CO2. In the past, Bosch-based technology did not trade favorably against SOA technology due to a high power demand, low reaction efficiencies, concerns with carbon containment, and large resupply requirements necessary to replace expended catalyst cartridges. An alternative approach to Bosch technology, labeled "Series-Bosch," employs a new system design with optimized multi-stage reactors and a membrane-based separation and recycle capability. Multi-physics modeling of the first stage reactor, along with chemical process modeling of the integrated system, has resulted in a design with potential to trade significantly better than previous Bosch technology. The modeling process and resulting system architecture selection are discussed.

  10. BAT AGN Spectroscopic Survey-III. An observed link between AGN Eddington ratio and narrow emission line ratios

    CERN Document Server

    Oh, Kyuseok; Koss, Michael; Trakhtenbrot, Benny; Lamperti, Isabella; Ricci, Claudio; Mushotzky, Richard; Veilleux, Sylvain; Berney, Simon; Crenshaw, D Michael; Gehrels, Neil; Harrison, Fiona; Masetti, Nicola; Soto, Kurt T; Stern, Daniel; Treister, Ezequiel; Ueda, Yoshihiro

    2016-01-01

    We investigate the observed relationship between black hole mass ($M_{\\rm BH}$), bolometric luminosity ($L_{\\rm bol}$), and Eddington ratio (${\\lambda}_{\\rm Edd}$) with optical emission line ratios ([NII] {\\lambda}6583/H{\\alpha}, [SII] {\\lambda}{\\lambda}6716,6731/H{\\alpha}, [OI] {\\lambda}6300/H{\\alpha}, [OIII] {\\lambda}5007/H{\\beta}, [NeIII] {\\lambda}3869/H{\\beta}, and HeII {\\lambda}4686/H{\\beta}) of hard X-ray-selected AGN from the BAT AGN Spectroscopic Survey (BASS). We show that the [NII] {\\lambda}6583/H{\\alpha} ratio exhibits a significant correlation with ${\\lambda}_{\\rm Edd}$ ($R_{\\rm Pear}$ = -0.44, $p$-value=$3\\times10^{-13}$, {\\sigma} = 0.28 dex), and the correlation is not solely driven by $M_{\\rm BH}$ or $L_{\\rm bol}$. The observed correlation between [NII] {\\lambda}6583/H{\\alpha} ratio and $M_{\\rm BH}$ is stronger than the correlation with $L_{\\rm bol}$, but both are weaker than the ${\\lambda}_{\\rm Edd}$ correlation. This implies that the large-scale narrow lines of AGN host galaxies carry informa...

  11. AGN host galaxy mass function in COSMOS: is AGN feedback responsible for the mass-quenching of galaxies?

    CERN Document Server

    Bongiorno, A; Merloni, A; Zamorani, G; Ilbert, O; La Franca, F; Peng, Y; Piconcelli, E; Mainieri, V; Silverman, J D; Brusa, M; Fiore, F; Salvato, M; Scoville, N

    2016-01-01

    We investigate the role of supermassive black holes in the global context of galaxy evolution by measuring the host galaxy stellar mass function (HGMF) and the specific accretion rate i.e., lambda_SAR, distribution function (SARDF) up to z~2.5 with ~1000 X-ray selected AGN from XMM-COSMOS. Using a maximum likelihood approach, we jointly fit the stellar mass function and specific accretion rate distribution function, with the X-ray luminosity function as an additional constraint. Our best fit model characterizes the SARDF as a double power-law with mass dependent but redshift independent break whose low lambda_SAR slope flattens with increasing redshift while the normalization increases. This implies that, for a given stellar mass, higher lambda_SAR objects have a peak in their space density at earlier epoch compared to the lower lambda_SAR ones, following and mimicking the well known AGN cosmic downsizing as observed in the AGN luminosity function. The mass function of active galaxies is described by a Schech...

  12. Average Heating Rate of Hot Atmospheres in Distant Clusters by Radio AGN: Evidence for Continuous AGN Heating

    CERN Document Server

    Ma, C -J; Nulsen, P E J; Schaffer, R; Vikhlinin, A

    2011-01-01

    X-ray observations of nearby clusters and galaxies have shown that energetic feedback from active galactic nuclei (AGN) is heating hot atmospheres and is probably the principal agent that is offsetting cooling flows. Here we examine AGN heating in distant X-ray clusters by cross correlating clusters selected from the 400 Square Degree X-ray Cluster survey with radio sources in the NRAO VLA Sky Survey. The jet power for each radio source was determined using scaling relations between radio power and cavity power determined for nearby clusters, groups, and galaxies with atmospheres containing X-ray cavities. Roughly 30% of the clusters show radio emission above a flux threshold of 3 mJy within the central 250 kpc that is presumably associated with the brightest cluster galaxy. We find no significant correlation between radio power, hence jet power, and the X-ray luminosities of clusters in redshift range 0.1 - 0.6. The detection frequency of radio AGN is inconsistent with the presence of strong cooling flows in...

  13. The KMOS AGN Survey at High redshift (KASHz): the prevalence and drivers of ionised outflows in the host galaxies of X-ray AGN

    CERN Document Server

    Harrison, C M; Mullaney, J R; Stott, J P; Swinbank, A M; Arumugam, V; Bauer, F E; Bower, R G; Bunker, A J; Sharples, R M

    2015-01-01

    We present the first results from the KMOS AGN Survey at High redshift (KASHz), a VLT/KMOS integral-field spectroscopic survey of z>0.6 AGN. We present galaxy-integrated spectra of 89 X-ray AGN (Lx=10^42-10^45 erg/s), for which we observed [O III] (z=1.1-1.7) or Halpha emission (z=0.6-1.1). The targets have X-ray luminosities representative of the parent AGN population and we explore the emission-line luminosities as a function of X-ray luminosity. For the [O III] targets, ~50 per cent have ionised gas velocities indicative of gas that is dominated by outflows and/or highly turbulent material (i.e., overall line-widths >~600 km/s). The most luminous half (i.e., Lx>6x10^43 erg/s) have a >~2 times higher incidence of such velocities. On the basis of our results, we find no evidence that X-ray obscured AGN are more likely to host extreme kinematics than unobscured AGN. Our KASHz sample has a distribution of gas velocities that is consistent with a luminosity-matched sample of z<0.4 AGN. This implies little ev...

  14. Clustering, Cosmology and a New Era of Black Hole Demographics: The Conditional Luminosity Function of AGNs

    Science.gov (United States)

    Ballantyne, David R.

    2017-01-01

    Deep X-ray surveys have provided a comprehensive and largely unbiased view of active galactic nuclei (AGN) evolution stretching back to z~5. However, it has been challenging to use the survey results to connect this evolution to the cosmological environment that AGNs inhabit. Exploring this connection will be crucial to understanding the triggering mechanisms of AGNs and how these processes manifest in observations at all wavelengths. In anticipation of upcoming wide-field X-ray surveys that will allow quantitative analysis of AGN environments, we present a method to observationally constrain the Conditional Luminosity Function (CLF) of AGNs at a specific z. Once measured, the CLF allows the calculation of the AGN bias, mean dark matter halo mass, AGN lifetime, halo occupation number, and AGN correlation function -- all as a function of luminosity. The CLF can be constrained using a measurement of the X-ray luminosity function and the correlation length at different luminosities. The method is illustrated at z≈0 and 0.9 using the limited data that is currently available, and a clear luminosity dependence in the AGN bias and mean halo mass is predicted at both, supporting the idea that there are at least two different modes of AGN triggering. In addition, the CLF predicts that z≈0.9 quasars may be commonly hosted by haloes with Mh ~ 1014 M⊙. These `young cluster' environments may provide the necessary interactions between gas-rich galaxies to fuel luminous accretion. The results derived from this method will be useful to populate AGNs of different luminosities in cosmological simulations.

  15. Incidence of WISE -selected obscured AGNs in major mergers and interactions from the SDSS

    Science.gov (United States)

    Weston, Madalyn E.; McIntosh, Daniel H.; Brodwin, Mark; Mann, Justin; Cooper, Andrew; McConnell, Adam; Nielsen, Jennifer L.

    2017-02-01

    We use the Wide-field Infrared Survey Explorer (WISE) and the Sloan Digital Sky Survey (SDSS) to confirm a connection between dust-obscured active galactic nuclei (AGNs) and galaxy merging. Using a new, volume-limited (z ≤ 0.08) catalogue of visually selected major mergers and galaxy-galaxy interactions from the SDSS, with stellar masses above 2 × 1010 M⊙, we find that major mergers (interactions) are 5-17 (3-5) times more likely to have red [3.4] - [4.6] colours associated with dust-obscured or `dusty' AGNs, compared to non-merging galaxies with similar masses. Using published fibre spectral diagnostics, we map the [3.4] - [4.6] versus [4.6] - [12] colours of different emission-line galaxies and find that one-quarter of Seyferts have colours indicative of a dusty AGN. We find that AGNs are five times more likely to be obscured when hosted by a merging galaxy, half of AGNs hosted by a merger are dusty, and we find no enhanced frequency of optical AGNs in merging over non-merging galaxies. We conclude that undetected AGNs missed at shorter wavelengths are at the heart of the ongoing AGN-merger connection debate. The vast majority of mergers hosting dusty AGNs are star forming and located at the centres of Mhalo < 1013 M⊙ groups. Assuming plausibly short-duration dusty-AGN phases, we speculate that a large fraction of gas-rich mergers experience a brief obscured AGN phase, in agreement with the strong connection between central star formation and black hole growth seen in merger simulations.

  16. A Fixed Bed Barrier Reactor with Separate Feed of Reactants

    NARCIS (Netherlands)

    Neomagus, H.W.J.P.; Saracco, G.; Versteeg, G.F.

    2001-01-01

    A new type of gas-solid reactor was developed and characterised in the series of reactor configurations with separate feed of reactants studied by our group. The novelty in the proposed design lies in the use of a fixed bed of small catalytic particles instead of a porous catalytic membrane. The maj

  17. Chart Series

    Data.gov (United States)

    U.S. Department of Health & Human Services — The Centers for Medicare and Medicaid Services (CMS) offers several different Chart Series with data on beneficiary health status, spending, operations, and quality...

  18. ¿Teología para agnósticos?

    Directory of Open Access Journals (Sweden)

    Sotelo Martínez, Igancio

    2002-04-01

    Full Text Available Not available

    Pretendo exponer de la manera más breve unas pocas razones que muestren que la teología concierne también al agnóstico. Por teología entiendo la reflexión sistemática en torno a la fe cristiana y por agnóstico, también en sentido muy amplio, aquel que no participa de esta fe. La tesis que defiendo es que no es necesaria la fe para interesarse por la teología; tiene sentido ocuparse de Dios sin creer en su existencia.
    ¿Por qué el agnóstico habría de ocuparse de la teología cuando el creyente parece que no la necesita? Cree antes de examinar reflexivamente su fe, que no depende de argumentos ni de demostraciones. Lo cierto es que la teología no conduce a la fe y hasta puede dudarse de si la fortalece. Conozco personas profundamente creyentes que huyen de las disquisiciones teológicas como de la peste. Viven la fe en una experiencia de amor al prójimoque no precisa de argumentos. Les basta acompañarse con las Sagradas Escrituras y de algunos libros piadosos o de espiritualidad. Cabría ampliar el horizonte de este artículo y preguntarse por el alcance y sentido que tenga la «reflexión sistemática» sobre Dios para aquellos que creen.
    En todo caso, no deja de ser paradójico intentar una defensa de la teología, cuando parece que les sobra, tanto a agnósticos como a creyentes; incluso la Iglesia ha encerrado a los teólogos en un gueto en el que, si bien gozan de mucha mayor libertad que en el pasado, la disfrutan en buena parte porque se han quedado sin audiencia. Escriben exclusivamente para los colegas que son los únicos que los leen. Claro que, dada la fragmentación actual de los saberes, lo mismo les ocurre a los demás especialistas.
    Si una buena parte de los creyentes se desentienden de la teología, ¿por qué habría de ocupar al agnóstico? Barrunto que una vindicación de la teología valga tanto para los unos como para los otros, pero en esta ocasión considero tan sólo las

  19. Radio-loud AGN-jet morphology and polarization: the role of ultra-high resolution radio surveys

    CERN Document Server

    Agudo, Ivan

    2016-01-01

    A review of the current challenges for the understanding of the physics of extragalactic radio jets from supermassive black holes is presented. Also, a prospect is given about how both very long baseline interferometry (VLBI) and polarimetric observations help us to understand their physics and the ones of their magnetic fields. This paper focuses on the impact that previous ultra-high resolution polarimetric surveys have had on our current knowledge on radio loud AGN. It first concentrates on the expectations about the improvement that the Square Kilometer Array, used as a super-sensitive VLBI station on existing and future very long baseline interferometric arrays, will provide in terms of access to new source classes, and in terms of a deeper portion of the Universe than currently accessible. A series of key new radio loud AGN science fields, to be opened by the Square Kilometer Array, are outlined together with a collection of preliminary ideas about possible programs of interest to deep in such fields. T...

  20. Anti-hierarchical evolution of the AGN space density in a hierarchical universe

    CERN Document Server

    Enoki, Motohiro; Kobayashi, Masakazu A R; Nagashima, Masahiro

    2014-01-01

    Recent observations show that the space density of luminous active galactic nuclei (AGN) peaks at higher redshifts than that of faint AGN. This downsizing trend in the AGN evolution seems to be contradictory to the hierarchical structure formation scenario. In this study, we present the AGN space density evolution predicted by a semi-analytic model of galaxy and AGN formation based on the hierarchical structure formation scenario. We demonstrate that our model can reproduce the downsizing trend of the AGN space density evolution. The reason for the downsizing trend in our model is a combination of the cold gas depletion as a consequence of star formation, the gas cooling suppression in massive halos and the AGN life time scaling with the dynamical time scale. We assume that a major merger of galaxies causes a starburst, spheroid formation, and cold gas accretion onto a supermassive black hole (SMBH). We also assume that this cold gas accretion triggers AGN activity. Since the cold gas is mainly depleted by st...

  1. AEGIS: The Clustering of X-ray AGN Relative to Galaxies at z~1

    CERN Document Server

    Coil, Alison L; Newman, Jeffrey A; Cooper, Michael C; Croton, Darren; Davis, Marc; Koo, David C; Laird, E S; Nandra, K; Weiner, Benjamin J; Willmer, Christopher N A; Yan, Renbin

    2009-01-01

    We measure the clustering of non-quasar X-ray AGN at z=0.7-1.4 in the AEGIS field. Using the cross-correlation of 113 Chandra-selected AGN, with a median log L_X=42.8 erg s^-1, with ~5,000 DEEP2 galaxies, we find that the X-ray AGN are fit by a power law with a clustering scale length of r_0=5.95 +/-0.90 h^-1 Mpc and slope gamma=1.66 +/-0.22. X-ray AGN have a similar clustering amplitude as red, quiescent and `green' transition galaxies at z~1 and are significantly more clustered than blue, star-forming galaxies. The X-ray AGN clustering strength is primarily determined by the host galaxy color; AGN in red host galaxies are significantly more clustered than AGN in blue host galaxies, with a relative bias that is similar to that of red to blue DEEP2 galaxies. We detect no dependence of clustering on optical brightness, X-ray luminosity, or hardness ratio within the ranges probed here. We find evidence for galaxies hosting X-ray AGN to be more clustered than a sample of galaxies with matching joint optical colo...

  2. Are Compton-Thick AGN the Missing Link Between Mergers and Black Hole Growth?

    CERN Document Server

    Kocevski, Dale D; Nandra, Kirpal; Koekemoer, Anton M; Salvato, Mara; Aird, James; Bell, Eric F; Hsu, Li-Ting; Kartaltepe, Jeyhan S; Koo, David C; Lotz, Jennifer M; McIntosh, Daniel H; Mozena, Mark; Rosario, David; Trump, Jonathan R

    2015-01-01

    We examine the host morphologies of heavily obscured active galactic nuclei (AGN) at $z\\sim1$ to test whether obscured supermassive black hole growth at this epoch is preferentially linked to galaxy mergers. Our sample consists of 154 obscured AGN with $N_{\\rm H}>10^{23.5}$ cm$^{-2}$ and $z<1.5$. Using visual classifications, we compare the morphologies of these AGN to control samples of moderately obscured ($10^{22}$ cm$^{-2}$ $AGN. These control AGN are matched in redshift and intrinsic X-ray luminosity to our heavily obscured AGN. We find that heavily obscured AGN at z~1 are twice as likely to be hosted by late-type galaxies relative to unobscured AGN ($65.3^{+4.1}_{-4.6}\\%$ vs $34.5^{+2.9}_{-2.7}\\%$) and three times as likely to exhibit merger or interaction signatures ($21.5^{+4.2}_{-3.3}\\%$ vs $7.8^{+1.9}_{-1.3}\\%$). The increased merger fraction is significant at the 3.8$\\sigma$ level. We also find that the inc...

  3. Obscuration in AGNs: near-infrared luminosity relations and dust colors

    CERN Document Server

    Burtscher, L; Davies, R I; Janssen, A; Lutz, D; Rosario, D; Contursi, A; Genzel, R; Gracia-Carpio, J; Lin, M -Y; Schnorr-Mueller, A; Sternberg, A; Sturm, E; Tacconi, L

    2015-01-01

    We combine two approaches to isolate the AGN luminosity at near-infrared wavelengths and relate the near-IR pure AGN luminosity to other tracers of the AGN. Using integral-field spectroscopic data of an archival sample of 51 local AGNs, we estimate the fraction of non-stellar light by comparing the nuclear equivalent width of the stellar 2.3 micron CO absorption feature with the intrinsic value for each galaxy. We compare this fraction to that derived from a spectral decomposition of the integrated light in the central arc second and find them to be consistent with each other. Using our estimates of the near-IR AGN light, we find a strong correlation with presumably isotropic AGN tracers. We show that a significant offset exists between type 1 and type 2 sources in the sense that type 1 sources are 7 (10) times brighter in the near-IR at log L_MIR = 42.5 (log L_X = 42.5). These offsets only becomes clear when treating infrared type 1 sources as type 1 AGNs. All AGNs have very red near-to-mid-IR dust colors. T...

  4. Using HI Absorption to Trace Outflows from Galaxies and Feeding of AGN

    NARCIS (Netherlands)

    Morganti, Raffaella; Barbosa, Domingos; Anton, Sonia; Gurvits, Leonid; Maia, Dalmiro

    2012-01-01

    Understanding the role of cold gas in the triggering and evolution of active galactic nuclei (AGN) is one of the goals of future cm and mm facilities. HI 21cm in absorption is one powerful diagnostic that can be used to explore these topics and probe the central regions of AGN. This contribution wil

  5. Hard X-ray Spectroscopy of Obscured AGN with NuSTAR

    Science.gov (United States)

    Balokovic, Mislav; Harrison, Fiona; NuSTAR Extragalactic Surveys Team

    2017-01-01

    The Nuclear Spectroscopic Telescope Array (NuSTAR) has enabled studies of the local active galactic nuclei (AGN) to extend into the hard X-ray band, up to 79 keV, with unprecedented spatial resolution and sensitivity. As a part of its extragalactic program, NuSTAR is surveying the nearby population of AGN detected at hard X-ray energies by the Swift Burst Alert Telescope (Swift/BAT), selecting even the most obscured local AGN. I will highlight some of the results based on broadband X-ray spectroscopy of individual targets and present my work on the large representative sample of more than a hundred nearby obscured AGN, which constitutes the largest available atlas of hard X-ray spectra of obscured AGN to date. The high quality of the data allows us to probe the details of AGN structures such as the X-ray-emitting corona and the toroidal obscurer in the under-explored spectral window above 10 keV. I will present both phenomenological results important for synthesis models of the cosmic X-ray background, and a novel approach for constraining the geometry of the gas surrounding the supermassive black hole (including the accretion disk, the broad-line region, and the torus) from the hard X-ray band. Finally, I will discuss how what we learned from this survey of local AGN relates to deeper high-redshift X-ray surveys and AGN structure probes at other wavelengths.

  6. A Comparison of X-ray and Mid-Infrared Selection of Obscured AGN

    CERN Document Server

    Eckart, Megan E; Stern, Daniel; Harrison, Fiona A; Helfand, David J

    2009-01-01

    We compare the relative merits of AGN selection at X-ray and mid-infrared wavelengths using data from moderately deep fields observed by both Chandra and Spitzer. The X-ray-selected AGN sample and associated optical follow-up are drawn from the SEXSI program. Mid-infrared data in these fields are derived from Spitzer imaging, and mid-infrared AGN selection is accomplished primarily through application of the IRAC color-color AGN `wedge' selection technique. Nearly all X-ray sources in these fields which exhibit clear spectroscopic signatures of AGN activity have mid-infrared colors consistent with IRAC AGN selection. These are predominantly the most luminous X-ray sources. X-ray sources that lack high-ionization and/or broad lines in their optical spectra are far less likely to be selected as AGN by mid-infrared color selection techniques. The fraction of X-ray sources identified as AGN in the mid-infrared increases monotonically as the X-ray luminosity increases. Conversely, only 22% of mid-infrared-selected...

  7. A Search for AGN Intra-Day Variability with KVN

    Science.gov (United States)

    Lee, Taeseok; Trippe, Sascha; Oh, Junghwan; Byun, Do-Young; Sohn, Bong-Won; Lee, Sang-Sung

    2015-10-01

    Active galactic nuclei (AGN) are known for irregular variability on all time scales, down to intra-day variability with relative variations of a few percent within minutes to hours. On such short timescales, unexplored territory, such as the possible existence of a shortest characteristic time scale of activity and the shape of the high frequency end of AGN power spectra, still exists. We present the results of AGN single-dish fast photometry performed with the Korean VLBI Network (KVN). Observations were done in a "anti-correlated" mode using two antennas, with always at least one antenna pointing at the target. This results in an effective time resolution of less than three minutes. We used all four KVN frequencies, 22, 43, 86, and 129 GHz, in order to trace spectral variability, if any. We were able to derive high-quality light curves for 3C 111, 3C 454.3, and BL Lacertae at 22 and 43 GHz, and for 3C 279 at 86 GHz, between May 2012 and April 2013. We performed a detailed statistical analysis in order to assess the levels of variability and the corresponding upper limits. We found upper limits on flux variability ranging from ∼1.6% to ∼7.6%. The upper limits on the derived brightness temperatures exceed the inverse Compton limit by three to six orders of magnitude. From our results, plus comparison with data obtained by the University of Michigan Radio Astronomy Observatory, we conclude that we have not detected source-intrinsic variability which would have to occur at sub-per cent levels.

  8. Relativistic HD and MHD modelling for AGN jets

    Science.gov (United States)

    Keppens, R.; Porth, O.; Monceau-Baroux, R.; Walg, S.

    2013-12-01

    Relativistic hydro and magnetohydrodynamics (MHD) provide a continuum fluid description for plasma dynamics characterized by shock-dominated flows approaching the speed of light. Significant progress in its numerical modelling emerged in the last two decades; we highlight selected examples of modern grid-adaptive, massively parallel simulations realized by our open-source software MPI-AMRVAC (Keppens et al 2012 J. Comput. Phys. 231 718). Hydrodynamical models quantify how energy transfer from active galactic nuclei (AGN) jets to their surrounding interstellar/intergalactic medium (ISM/IGM) gets mediated through shocks and various fluid instability mechanisms (Monceau-Baroux et al 2012 Astron. Astrophys. 545 A62). With jet parameters representative for Fanaroff-Riley type-II jets with finite opening angles, we can quantify the ISM volumes affected by jet injection and distinguish the roles of mixing versus shock-heating in cocoon regions. This provides insight in energy feedback by AGN jets, usually incorporated parametrically in cosmological evolution scenarios. We discuss recent axisymmetric studies up to full 3D simulations for precessing relativistic jets, where synthetic radio maps can confront observations. While relativistic hydrodynamic models allow one to better constrain dynamical parameters like the Lorentz factor and density contrast between jets and their surroundings, the role of magnetic fields in AGN jet dynamics and propagation characteristics needs full relativistic MHD treatments. Then, we can demonstrate the collimating properties of an overal helical magnetic field backbone and study differences between poloidal versus toroidal field dominated scenarios (Keppens et al 2008 Astron. Astrophys. 486 663). Full 3D simulations allow one to consider the fate of non-axisymmetric perturbations on relativistic jet propagation from rotating magnetospheres (Porth 2013 Mon. Not. R. Astron. Soc. 429 2482). Self-stabilization mechanisms related to the detailed

  9. Revisiting Stochastic Variability of AGNs with Structure Functions

    Science.gov (United States)

    Kozłowski, Szymon

    2016-08-01

    Discrepancies between reported structure function (SF) slopes and their overall flatness as compared to the expectations from the damped random walk (DRW) model, which generally well describes the variability of active galactic nuclei (AGNs), have triggered us to study this problem in detail. We review common AGN variability observables and identify their most common problems. Equipped with this knowledge, we study ˜9000 r-band AGN light curves from Stripe 82 of the Sloan Digital Sky Survey, using SFs described by stochastic processes with the power exponential covariance matrix of the signal. We model the “subensemble” SFs in the redshift-absolute magnitude bins with the full SF equation (including the turnover and the noise part) and a single power law (SPL; in the “red noise regime” after subtracting the noise term). The distribution of full-equation SF (SPL) slopes peaks at γ =0.55+/- 0.08 (0.52 ± 0.06) and is consistent with the DRW model. There is a hint of a weak correlation of γ with the luminosity and a lack of correlation with the black hole mass. The typical decorrelation timescale in the optical is τ =0.97+/- 0.46 year. The SF amplitude at one year obtained from the SPL fitting is {{SF}}0=0.22+/- 0.06 mag and is overestimated because the SF is already at the turnover part, so the true value is {{SF}}0=0.20+/- 0.06 mag. The asymptotic variability is {{SF}}∞ =0.25+/- 0.06 mag. It is strongly anticorrelated with both the luminosity and the Eddington ratio and is correlated with the black hole mass. The reliability of these results is fortified with Monte Carlo simulations.

  10. Accretion Disk Line Emission in AGN a Devil's Advocacy

    CERN Document Server

    Sulentic, J W; Dultzin-Hacyan, D

    1998-01-01

    We review the evidence for AGN optical and X-ray broad line emission from an accretion disk. We argue that there is little, if any, statistical evidence to support this assertion. The inconsistency is strongest for the rare class of Balmer profiles that show double peaks. The line profiles predicted by a simple illuminated disk model are often incompatible with the observations. We suggest that the Fe Kalpha line in Seyfert 1 galaxies, where a broad line is most often and most strongly detected, is actually a composite of two lines both with Gaussian profiles; one narrow/unshifted and the other broad/redshifted.

  11. The AGN Jet Model of the Fermi Bubbles

    CERN Document Server

    Guo, Fulai

    2016-01-01

    The nature and origin of the Fermi bubbles detected in the inner Galaxy remain elusive. In this paper, we briefly discuss some recent theoretical and observational developments, with a focus on the AGN jet model. Analogous to radio lobes observed in massive galaxies, the Fermi bubbles could be naturally produced by a pair of opposing jets emanating nearly along the Galaxy's rotation axis from the Galactic center. Our two-fluid hydrodynamic simulations reproduce quite well the bubble location and shape, and interface instabilities at the bubble surface could be effectively suppressed by shear viscosity. We briefly comment on some potential issues related to our model, which may lead to future progress.

  12. The jet of the Low Luminosity AGN of M81

    Directory of Open Access Journals (Sweden)

    Alberdi A.

    2013-12-01

    Full Text Available In this contribution, we summarize our main results of a big campaign of global VLBI observations of the AGN in M81 (M81* phase-referenced to the radio supernova SN 1993J. Thanks to the precise multi-epoch and multi-frequency astrometry, we have determined the normalized core-shift of the relativistic jet of M81* and estimated both the magnetic field and the particle density at the jet base. We have also found evidence of jet precession in M81* coming from the systematic time evolution of the jet orientation correlated with changes in the overall flux density.

  13. The PAH contribution to AGN near-infrared emission

    Science.gov (United States)

    Marco, O.; Brooks, K.

    In the course of building ``unified models'' of Active Galactic Nuclei, the near infrared emission in the central kilo-parsec nuclear region is a key parameter: this wavelength range corresponds to the hot to warm dust emission, which originates in the torus and the Narrow Line Region (from a few parsecs to hundreds of parsecs). The measured flux is interpreted in terms of thermal emission and, via a dust modelisation, torus models are built. Using ISAAC at VLT, we observed a sample of AGNs in order to estimate the relative contribution between the thermal continuum emission from silicate & graphite dust grains and PAH molecules.

  14. Radio continuum surveys and galaxy evolution: The AGN view

    CERN Document Server

    Smolcic, Vernesa

    2016-01-01

    Understanding how galaxies form in the early universe and their subsequent evolution through cosmic time is a major goal of modern astrophysics. Panchromatic look-back sky surveys significantly advanced the field in the past decades, and we are now entering an even more fruitful period - a 'golden age' of radio astronomy - with upgraded, and new facilities delivering an order of magnitude increase in sensitivity. An overview of recent developments in radio continuum sky surveys, focusing on the physical properties and cosmic evolution of radio AGN since z~5 is presented here.

  15. The cluster environments of radio-loud AGN

    CERN Document Server

    Ineson, Judith; Hardcastle, Martin; Kraft, Ralph; Evans, Daniel; Jarvis, Matt

    2014-01-01

    Radio-loud AGN play an important r\\^ole in galaxy evolution. We need to understand their properties, and the processes that affect their behaviour in order to model galaxy formation and development. We here present preliminary results of an investigation into the cluster environments of radio galaxies. We have found evidence of a strong correlation between radio luminosity and environment richness for low excitation radio galaxies, and no evidence of evolution of the environment with redshift. Conversely, for high excitation radio galaxies, we found no correlation with environment richness, and tentative evidence of evolution of the cluster environment.

  16. Broad emission lines variability: a window into the heart of AGN

    Science.gov (United States)

    Ilic, Dragana; Popovic, Luka C.; Shapovalova, Alla I.; Afanasiev, V. L.; Chavushyan, V. H.; Burenkov, A.; Kollatschny, W.; Kovacevic, A.

    2016-08-01

    The broad emission lines of active galactic nuclei (AGN) are known to vary both in flux and shape, and are often showing very complex line profiles. They can give us invaluable information about the kinematics and geometry of the broad line region (BLR) where these lines are originating from. The BLR is close to the supermassive black hole in AGN and may hold basic information about the formation and fueling of AGN.Here we summarize the results of the line and continuum variability of a sample of broad line AGN, obtained with the long-term optical monitoring campaign performed with telescopes of SAO (Russia), OAGH and OAN-SPM (Mexico), and Calar Alto (Spain). We monitored different type of broad line AGN (double-peaked, radio loud and radio quiet, NLSy1 and a supermassive binary black hole candidate) which show different variability characteristics that can be explained by different physical properties in BLR.

  17. The Abundance of Distant and Extremely Red Galaxies: The Role of AGN Feedback in Hierarchical Models

    CERN Document Server

    Menci, N; Giallongo, E; Grazian, A; Salimbeni, S

    2006-01-01

    We investigate the effect of AGN feedback associated to the bright QSO phase onto the color distribution of galaxies from z=0 up to z=4. To this aim, we insert a blast-wave model of AGN feedback in our semi-analytic model of galaxy formation, which includes the growth of supermassive black holes and the AGN activity triggered by interactions of the host galaxies. The AGN feedback is directly related to the impulsive, luminous quasar phase. We test our model by checking the consistency of its results against i) the QSO luminosity functions from z=0 to z=4; ii) the observed local relation between the black hole mass m_{BH} and the mass of the host galaxy. At low redshift the inclusion of AGN feedback enhances the number of red bright galaxies, so that the color distribution of M_r1.5) galaxies; at 0.52.5.

  18. COPROX fixed bed reactor - temperature control schemes

    Energy Technology Data Exchange (ETDEWEB)

    Giunta, P.; Moreno, M.; Marino, F.; Amadeo, N.; Lobarde, M. [Laboratorio de Procesos Cataliticos, Facultad de Ingenieria, Universidad de Buenos Aires, Buenos Aires (Argentina)

    2012-06-15

    Different temperature control schemes for the COPROX stage of a 5-kW fuel cell system were analyzed. It was found that, among the schemes proposed, i.e., co- and countercurrent heat exchange, single adiabatic reactor and series of adiabatic reactors with interstage heat exchange, the best choice for temperature control was the series of adiabatic reactors with interstage heat exchange. This scheme represented the best way to keep the average temperature around 443 K, which was found to be the most suitable temperature for selectivity towards CO oxidation. If hydrogen is produced from ethanol steam reforming, the heat withdrawal can be carried out by the water/ethanol reformer feed mixture, thus contributing to the energy integration of the overall system. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Reactor Physics Programme

    Energy Technology Data Exchange (ETDEWEB)

    De Raedt, C

    2000-07-01

    The Reactor Physics and Department of SCK-CEN offers expertise in various areas of reactor physics, in particular in neutronics calculations, reactor dosimetry, reactor operation, reactor safety and control and non-destructive analysis on reactor fuel. This expertise is applied within the Reactor Physics and MYRRHA Research Department's own research projects in the VENUS critical facility, in the BR1 reactor and in the MYRRHA project (this project aims at designing a prototype Accelerator Driven System). Available expertise is also used in programmes external to the Department such as the reactor pressure steel vessel programme, the BR2 reactor dosimetry, and the preparation and interpretation of irradiation experiments. Progress and achievements in 1999 in the following areas are reported on: (1) investigations on the use of military plutonium in commercial power reactors; (2) neutron and gamma calculations performed for BR-2 and for other reactors; (3) the updating of neutron and gamma cross-section libraries; (4) the implementation of reactor codes; (6) the management of the UNIX workstations; and (6) fuel cycle studies.

  20. Using gravitational lensed images to investigate the intrinsic AGN variability

    CERN Document Server

    Marti-Vidal, I

    2016-01-01

    We discuss about how the relative flux densities among the images of gravitationally-lensed active galactic nuclei, AGN, can be used to study the intrinsic AGN variability with high accuracy. Multi-frequency monitoring observations of resolved gravitational lenses can allow us to detect signals of very weak variability and also provide information about the jet opacity and structure. As an example, we investigate the variability of the flux-density ratio between the two lensed images of the blazar B0218+357, using dual-frequency cm-wave observations. Similar to our previously reported submm-wave observations of the lensed blazar PKS1830-211, we observe a clear chromatic variability, starting short before an increase in the flux-density of the blazar. The evolution of the flux-density ratios between the blazar images shows a more clear and rich structure than that of the mere lightcurves of each individual image. The accuracy in the ratio measurements is allowing us to see variability episodes in the blazar th...

  1. Black hole mass, jet power and accretion in AGN

    CERN Document Server

    Chen, Yong-Yun; Xiong, Dingrong; Yu, Xiaoling

    2015-01-01

    We study the relation between accretion, black hole mass and jet power in AGN, by using a large group of blazars detected by the Fermi Large Area Telescope and radio galaxies. Our main results are as follows. (i) The jet power of FSRQs and FRII-HEG depends on the black hole mass, which suggests that the FSRQs and FRII-HEG are in Radiation-Pressure Dominated regime. The jet power of BL Lacs and FRI-LEG depends on the accretion, which suggests that the BL Lacs and FRI-LEG are in the Gas-Pressure Dominated regime. (ii) We find that most of FSRQs and BL Lacs have $\\rm{P_{jet}>L_{BZ}^{max}}$, which suggests that the Blandford-Znajek mechanism is insufficient to explain the jet power of these objects. (iii) The FSRQs are roughly separated from BL Lacs by the Ledlow-Owen's dividing line in the $\\rm{\\log P_{jet}-\\log M}$ plane, which supports the unified scheme of AGN. (iv) The FSRQs and BL Lacs have a clear division at $\\rm{L_{bol}/L_{Edd}\\sim0.01}$, and the distribution of Eddington ratios of BL Lacs and FSRQs exhi...

  2. Compton reflection and iron fluorescence in AGN and GBHCs

    CERN Document Server

    Reynolds, C S

    1998-01-01

    Any cold, optically-thick matter in the vicinity of an accreting black hole, such as the accretion disk, can intercept and reprocess some fraction of the hard X-ray continuum emission, thereby imprinting atomic features into the observed spectrum. This process of `X-ray reflection' primarily gives rise to a broad reflection `hump' peaking at 30keV and an iron emission line at 6.4keV. In this review, I briefly describe the physics of this process before reviewing the observations of these features in active galactic nuclei (AGN) and Galactic black hole candidates (GBHCs). In some AGN, Seyfert galaxies in particular, the iron line is found to be very broad and asymmetric. It is believed that such lines arise from the innermost regions of the accretion disk, with mildly-relativistic Doppler shifts and gravitational redshifts combining to produce the line profile. Hence, such lines give us a direct observational probe of the region within several gravitational radii of the black hole. The complications that plagu...

  3. AGN-Induced Cavities in NGC 1399 And NGC 4649

    Energy Technology Data Exchange (ETDEWEB)

    Shurkin, K.; /New Mexico U.; Dunn, R.J.H.; /Southampton U.; Gentile, G.; Taylor, G.B.; /New Mexico U.; Allen, S.W.; /KIPAC, Menlo Park

    2007-11-14

    We present an analysis of archival Chandra and VLA observations of the E0 galaxy NGC1399 and the E2 galaxy NGC4649 in which we investigate cavities in the surrounding X-ray emitting medium caused by the central AGN. We calculate the jet power required for the AGN to evacuate these cavities and find values of {approx} 8x10{sup 41} erg s-1 and {approx} 14x10{sup 41} erg s{sup -1} for the lobes of NGC1399 and {approx} 7x10{sup 41} erg s{sup -1} and {approx} 6x1041 erg s{sup -1} for those of NGC4649. We also calculate the k/f values for each cavity, where k is the ratio of the total particle energy to that of electrons radiating in the range of 10 MHz to 10 GHz, and f is the volume filling factor of the plasma in the cavity. We find that the values of k/f for the lobes of NGC1399 are {approx} 93 and {approx} 190, and those of the lobes of NGC4649 are {approx} 15000 and {approx} 12000. We conclude that the assumed spectrum describes the electron distribution in the lobes of NGC1399 reasonably well, and that there are few entrained particles. For NGC4649, either there are many entrained particles or the model spectrum does not accurately describe the population of electrons.

  4. Type 1 low z AGN. I. Emission properties

    CERN Document Server

    Stern, Jonathan

    2012-01-01

    We analyze the emission properties of a new sample of 3,579 type 1 AGN, selected from the SDSS DR7 based on the detection of broad H-alpha emission. The sample extends over a broad H-alpha luminosity L_bHa of 10^40 - 10^44 erg s^-1 and a broad H-alpha FWHM of 1,000 - 25,000 km s^-1, which covers the range of black hole mass 10^6AGN, regardless of the host luminosity. 4. The hosts of lower lumin...

  5. Discovery of Four kpc-Scale Binary AGNs

    CERN Document Server

    Liu, Xin; Shen, Yue; Strauss, Michael A

    2010-01-01

    We report the discovery of four kpc-scale binary AGNs. These objects were originally selected from the Sloan Digital Sky Survey based on double-peaked [O III] 4959,5007 emission lines in their fiber spectra. The double peaks could result from pairing active supermassive black holes (SMBHs) in a galaxy merger, or could be due to bulk motions of narrow-line region gas around a single SMBH. Deep near-infrared (NIR) images and optical slit spectra obtained from the Magellan 6.5 m and the APO 3.5 m telescopes strongly support the binary SMBH scenario for the four objects. In each system, the NIR images reveal tidal features and double stellar bulges with a projected separation of several kpc, while optical slit spectra show two Seyfert 2 nuclei spatially coincident with the stellar bulges, with line-of-sight velocity offsets of a few hundred km/s. These objects were drawn from a sample of only 43 objects, demonstrating the efficiency of this technique to find kpc-scale binary AGNs.

  6. Eclipsing the innermost X-ray emitting regions in AGN

    CERN Document Server

    Sanfrutos, Mario; Dovčiak, Michal; Agís-González, Beatriz

    2015-01-01

    Variable X-ray absorption has been observed in active galactic nuclei (AGN) on several time scales. Observations allow us to identify the absorber with clouds associated either with the clumpy torus (parsec scales, long timescales) or with the broad line region (BLR) (short timescales). In the latter, the cloud size has been estimated to be of the order of few gravitational radii from the observed absorption variability. Such small cloud sizes are comparable to the X-ray emitting regions so that a detailed modeling of occultation events in AGN has the potential of enabling us to infer accurately the geometry of the system. We have developed a relativistic X-ray spectral model for occultation events and we present here theoretical predictions on the different observables that can be inferred by studying X-ray eclipses in simulated XMM-Newton data. These include the size of the X-ray emitting regions as well as more fundamental parameters such as the black hole spin and the system inclination. We find that abso...

  7. Radio transient following FRB 150418: afterglow or coincident AGN flare?

    CERN Document Server

    Li, Ye

    2016-01-01

    Recently, Keane et al. reported the discovery of a fading radio transient following FRB 150418, and interpreted it as the afterglow of the FRB. Williams \\& Berger, on the other hand, suggested that the radio transient is analogous to a group of variable radio sources, so that it could be a coincident AGN flare in the observational beam of the FRB. A new observation with VLA showed a re-brightening, which is consistent with the AGN picture. Here, using the radio survey data of Ofek et al., we statistically examine the chance coincidence probability to produce an event like the FRB 150418 transient. We find that the probabilities to produce a variable radio transient with at least the same variability amplitude and signal-to-noise ratio as the FRB 150415 transient, without and with the VLA point, are $P_1 \\sim 6 \\times 10^{-4}$ and $P_1 \\sim 2 \\times 10^{-3}$, respectively. In addition, the chance probability to have a fading transient detected following a random time (FRB time) is less than $P_2 \\sim 10^{-...

  8. Dynamical Delays Between Starburst and AGN Activity in Galaxy Nuclei

    CERN Document Server

    Hopkins, Philip F

    2011-01-01

    Observations of AGN have suggested a possible delay between the peak of star formation (on some scale) and AGN activity. Feedback from fast stellar winds has been invoked to explain this, but this is not likely to be viable in bright systems accreting primarily cold dense gas. We show that such a delay can arise even in bright quasars for purely dynamical reasons. If some large-scale process produces rapid inflow, smaller scales will quickly become gas-dominated. As the gas density peaks, so does the SFR. However, gravitational torques which govern further inflow are relatively inefficient in gas-dominated systems; as more gas is turned into stars, the stars provide an efficient angular momentum sink allowing more rapid inflow. Moreover, the gas provided to the central regions in mergers or strong disk instabilities will typically be ~100 times larger than that needed to fuel the BH; the system is effectively in the 'infinite gas supply' limit. BH growth can therefore continue for some time while the gas supp...

  9. Detecting Neutrinos from AGN New Fluxes and Cross Sections

    CERN Document Server

    Hill, G C

    1996-01-01

    New information on the structure of the nucleon from the HERA ep collider leads to higher neutrino cross sections for the processes nu_mu + N --> mu + X needed to calculate the expected rates of astrophysical neutrino induced muons in large detectors either under construction, or in the design stage. These higher cross sections lead to higher muon rates for arrival angles where neutrino attenuation in the earth is less important. On the other hand, new estimates of AGN neutrino fluxes suggest that the expected muon rates in these detectors may be much lower than previously calculated. I use the new cross sections to calculate the expected muon rates and angular distributions in large detectors for a variety of AGN models and compare these rates with the atmospheric neutrino backrounds (from both conventional decay channels and the "prompt" charmed meson decay channels). If the lowest flux estimates are correct, there may be diffculties in determining the origin of a small excess of muons, due to the large unc...

  10. Simulations of the OzDES AGN Reverberation Mapping Project

    CERN Document Server

    King, Anthea L; Davis, Tamara M; Denney, K D; Kochanek, C S; Peterson, Bradley M; Skielboe, Andreas; Vestergaard, Marianne; Huff, Eric; Watson, Darach; Banerji, Manda; McMahon, Richard; Sharp, Rob; Lidman, C

    2015-01-01

    As part of the OzDES spectroscopic survey we are carrying out a large scale reverberation mapping study of $\\sim$500 quasars over five years in the 30 deg$^2$ area of the Dark Energy Survey (DES) supernova fields. These quasars have redshifts ranging up to 4 and have apparent AB magnitudes between $16.8AGN and constrain the radius-luminosity ($R-L$) relationship. Here we investigate the expected efficiency of the OzDES reverberation mapping campaign and its possible extensions. We expect to recover lags for $\\sim$35-45\\% of the quasars. AGN with shorter lags and greater variability are more likely to yield a lag, and objects with lags $\\lesssim$6 month or $\\sim$1 year are expected be recovered the most accurately. The baseline OzDES reverberation mapping campaign is predicted to produce an ...

  11. XMM-Newton, powerful AGN winds and galaxy feedback

    Science.gov (United States)

    Pounds, K.; King, A.

    2016-06-01

    The discovery that ultra-fast ionized winds - sufficiently powerful to disrupt growth of the host galaxy - are a common feature of luminous AGN is major scientific breakthrough led by XMM-Newton. An extended observation in 2014 of the prototype UFO, PG1211+143, has revealed an unusually complex outflow, with distinct and persisting velocities detected in both hard and soft X-ray spectra. While the general properties of UFOs are consistent with being launched - at the local escape velocity - from the inner disc where the accretion rate is modestly super-Eddington (King and Pounds, Ann Rev Astron Astro- phys 2015), these more complex flows have raised questions about the outflow geometry and the importance of shocks and enhanced cooling. XMM-Newton seems likely to remain the best Observatory to study UFOs prior to Athena, and further extended observations, of PG1211+143 and other bright AGN, have the exciting potential to establish the typical wind dynamics, while providing new insights on the accretion geometry and continuum source structure. An emphasis on such large, coordinated observing programmes with XMM-Newton over the next decade will continue the successful philosophy pioneered by EXOSAT, while helping to inform the optimum planning for Athena

  12. Fueling AGN II: Spatially Resolved Molecular Inflows and Outflows

    CERN Document Server

    Davies, R I; Hicks, E K S; Emsellem, E; Erwin, P; Burtscher, L; Dumas, G; Lin, M; Malkan, M A; Mueller-Sanchez, F; de Xivry, G Orban; Rosario, D J; Schnorr-Mueller, A; Tran, A

    2014-01-01

    We analyse the 2-dimensional distribution and kinematics of the stars as well as molecular and ionised gas in the central few hundred parsecs of 5 active and 5 matched inactive galaxies. The equivalent widths of the Br-gamma line indicate there is no on-going star formation in their nuclei, although recent (terminated) starbursts are possible in the active galaxies. The stellar velocity fields show no signs of non-circular motions, while the 1-0S(1) H_2 kinematics exhibit significant deviations from simple circular rotation. In the active galaxies the H_2 kinematics reveal inflow and outflow superimposed on disk rotation. Steady-state circumnuclear inflow is seen in three AGN, and hydrodynamical models indicate it can be driven by a large scale bar. In three of the five AGN, molecular outflows are spatially resolved. The outflows are oriented such that they intersect, or have an edge close to, the disk - which may be the source of molecular gas in the outflow. The relatively low speeds imply the gas will fall...

  13. AGN jets driven stochastic cold accretion in cluster cores

    CERN Document Server

    Prasad, Deovrat; Babul, Arif

    2016-01-01

    Several arguments suggest that stochastic condensation of cold gas and its accretion onto the central supermassive black hole (SMBH) is essential for active galactic nuclei (AGN) feedback to work in the most massive galaxies that lie at the centers of galaxy clusters. Our 3-D AGN jet-ICM (intracluster medium) simulations show that the angular momentum of the cold gas crossing $\\lesssim 1$ kpc is essentially isotropic. With almost equal mass in clockwise and counter-clockwise orientations, we expect a cancellation of angular momentum on roughly the dynamical time. This means that a compact accretion flow with a short viscous time ought to form, through which enough accretion power can be channeled into jet mechanical energy sufficiently quickly to prevent a cooling flow. The inherent stochasticity, expected in feedback cycles driven by cold gas condensation, gives rise to a large variation in the cold gas mass at the centers of galaxy clusters, for similar cluster and SMBH masses, in agreement with the observa...

  14. An AGN Identification for 3EG J2006-2321

    Science.gov (United States)

    Wallace, P. M.; Halpern, J. P.; Magalhaes, A. M.; Thompson, D. J.; White, Nicholas E. (Technical Monitor)

    2001-01-01

    We present a multiwavelength analysis of the high-energy gamma-ray source 3EG J2006-2321 (l = 18 deg.82, b = -26 deg.26). The flux of this source above 100 MeV is shown to be variable on time scales of days and months. Optical observations and careful examination of archived radio data indicate that its most probable identification is with PMN J2005-2310, a flat-spectrum radio quasar with a 5GHz flux density of 260 mJy. Study of the V = 19.3 optical counterpart indicates a redshift of 0.833 and variable linear polarization. No X-ray source has been detected near the position of PMN J2005-2310, but an X-ray upper limit is derived from ROSAT data. This upper limit provides for a spectral energy distribution with global characteristics similar to those of known gamma-ray blazars. Taken together, these data indicate that 3EG J2006-2321, listed as unidentified in the 3rd EGRET Catalog, is a member of the blazar class of AGN. The 5-GHz radio flux density of this blazar is the lowest of the 68 EGRET-detected AGN. The fact that EGRET has detected such a source has implications for unidentified EGRET sources, particularly those at high latitudes (absolute value of b greater than 30 deg), many of which may be blazars.

  15. The cluster-scale AGN outburst in Hydra A

    CERN Document Server

    Nulsen, P E J; Wise, M W; David, L P

    2004-01-01

    Deep Chandra observations of the Hydra A Cluster reveal a feature in the X-ray surface brightness that surrounds the 330 MHz radio lobes of the AGN at the cluster center. Surface brightness profiles of this feature and its close association with the radio lobes argue strongly that it is a shock front driven by the expanding radio lobes. The Chandra image also reveals other new structure on smaller scales that is associated with the radio source, including a large cavity and filament. The shock front extends 200 - 300 kpc from the AGN at the cluster center and its strength varies along the front, with Mach numbers in the range ~ 1.2 - 1.4. It is stronger where it is more distant from the cluster center, as expected for a shock driven by expanding radio lobes. Simple modeling gives an age for the shock front ~ 1.4\\times10^8 y and a total energy driving it of ~ 10^{61} erg. The mean mechanical power driving the shock is comparable to quasar luminosities, well in excess of that needed to regulate the cooling core...

  16. HIGH-Z X-RAY AGN CLUSTERING & COSMOLOGICAL INFERENCE

    Directory of Open Access Journals (Sweden)

    M. Plionis

    2009-01-01

    Full Text Available We study the angular clustering of X-ray selected active galactic nuclei (AGN in di erent ux-limited sub- samples of the Chandra Deep Field North (CDF-N and South (CDF-S surveys. We nd a strong dependence of the clustering strength on the sub-sample ux-limit, a fact which explains most of the disparate clustering results of di erent XMM and Chandra surveys. At high ux-limits the clustering length increases considerably; for example, at fx;limit 1015 erg s-1 cm-2, we obtain r0 ' 17 5 and 18 3 h-1 Mpc, for the CDF-N and CDF-S, respectively. The ux-limit dependence translates into a luminosity dependent X-ray AGN clustering. Applying the standard formalism relating the theoretical CDM model clustering to the data in a at cosmology (for w =-1 and h = 0:72, we nd: m ' 0:28 0:03 and 8 ' 0:75 0:03; while utilizing also the SN Ia Hubble relation (for 8 = 0:75 and h = 0:72, we nd: m ' 0:26 0:04 and w = 0:9 0:1

  17. Dust in high-z radio-loud AGN

    CERN Document Server

    Cimatti, A; Röttgering, H J A; Ivison, R J; Mazzei, P; Cimatti, Andrea; Freudling, Wolfram; Roettgering, Huub; Ivison, Rob; Mazzei, Paola

    1997-01-01

    We present continuum observations of a small sample of high-redshift, radio-loud AGN (radio galaxies and quasars) aimed at the detection of thermal emission from dust. Seven AGN were observed with IRAM and SEST at 1.25mm; two of them, the radio galaxies 1243+036 ($z \\sim 3.6$) and MG1019+0535 ($z \\sim 2.8$) were also observed at 0.8mm with the JCMT submillimetre telescope. Additional VLA observations were obtained in order to derive the spectral shape of the synchrotron radiation of MG1019+0535 at high radio frequencies. MG1019+0535 and TX0211$-$122 were expected to contain a large amount of dust based on their depleted Ly$\\alpha$ emission. The observations suggest a clear 1.25-mm flux density excess over the synchrotron radiation spectrum of MG1019+0535, suggesting the presence of thermal emission from dust in this radio galaxy, whereas the observations of TX0211$-$122 were not sensitive enough to meaningfully constrain its dust content. On the other hand, our observations of 1243+036 provide a stringent upp...

  18. Variability and Multiwavelength Detected AGN in the GOODS Fields

    CERN Document Server

    Sarajedini, Vicki L; Klesman, Alison J; Laird, Elise S; Gonzalez, Pablo G Perez; Mozena, Mark

    2011-01-01

    We identify 85 variable galaxies in the GOODS North and South fields using 5 epochs of HST ACS V-band (F606W) images spanning 6 months. The variables are identified through significant flux changes in the galaxy's nucleus and represent ~2% of the survey galaxies. With the aim of studying the active galaxy population in the GOODS fields, we compare the variability-selected sample with X-ray and mid-IR AGN candidates. Forty-nine percent of the variables are associated with X-ray sources identified in the 2Ms Chandra surveys. Twenty-four percent of X-ray sources likely to be AGN are optical variables and this percentage increases with decreasing hardness ratio of the X-ray emission. Stacking of the non-X-ray detected variables reveals marginally significant soft X-ray emission. Forty-eight percent of mid-IR power-law sources are optical variables, all but one of which are also X-ray detected. Thus, about half of the optical variables are associated with either X-ray or mid-IR power-law emission. The slope of the...

  19. LMFBR type reactor

    Energy Technology Data Exchange (ETDEWEB)

    Kawakami, Hiroto

    1995-02-07

    A reactor container of the present invention has a structure that the reactor container is entirely at the same temperature as that at the inlet of the reactor and, a hot pool is incorporated therein, and the reactor container has is entirely at the same temperature and has substantially uniform temperature follow-up property transiently. Namely, if the temperature at the inlet of the reactor core changes, the temperature of the entire reactor container changes following this change, but no great temperature gradient is caused in the axial direction and no great heat stresses due to axial temperature distribution is caused. Occurrence of thermal stresses caused by the axial temperature distribution can be suppressed to improve the reliability of the reactor container. In addition, since the laying of the reactor inlet pipelines over the inside of the reactor is eliminated, the reactor container is made compact and the heat shielding structures above the reactor and a protection structure of container walls are simplified. Further, secondary coolants are filled to the outside of the reactor container to simplify the shieldings. The combined effects described above can improve economical property and reliability. (N.H.).

  20. Nuclear reactors and fuel cycle

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2014-07-01

    fulfill its mission that is to contribute in improving the quality of life of the Brazilian people. The nuclear fuel cycle is a series of steps involved in the production and use of fuel for nuclear reactors. The Laboratories of Chemistry and Environmental Diagnosis Center, CQMA, support the demand of Nuclear Fuel Cycle Program providing chemical characterization of uranium compounds and other related materials. In this period the Research Reactor Center (CRPq) concentrated efforts on improving equipment and systems to enable the IEA-R1 research reactor to operate at higher power, increasing the capacity of radioisotopes production, samples irradiation, tests and experiments. (author)

  1. Optical variability of AGN in the PTF/iPTF survey

    CERN Document Server

    Caplar, Neven; Trakhtenbrot, Benny

    2016-01-01

    We characterize the optical variability of quasars in the intermediate Palomar Transient Factory (iPTF) and Palomar Transient Factory (PTF) surveys. We re-calibrate the $r$-band light curves for $\\sim$28,000 luminous, broad-line AGNs from the SDSS, producing a total of $\\sim$2.4 million photometric data points. We utilize both the structure function (SF) and power spectrum density (PSD) formalisms to search for links between the optical variability and the physical parameters of the accreting supermassive black holes that power the quasars. The excess variance (SF$^{2}$) of the quasar sample tends to zero at very short time separations, validating our re-calibration of the time-series data. We find that the the amplitude of variability at a given time-interval, or equivalently the time-scale of variability to reach a certain amplitude, is most strongly correlated with luminosity with weak or no dependence on black hole mass and redshift. For a variability level of SF($\\tau$)=0.07 mag, the time-scale has a dep...

  2. Dielectronic Recombination Of Iron M-shell Ions Motivated By Absorption Features In AGN Spectra

    Science.gov (United States)

    Lukic, Dragan; Schnell, M.; Savin, D. W.; Brandau, C.; Schmidt, E. W.; Yu, D.; Bernhardt, D.; Schippers, S.; Müller, A.; Lestinsky, M.; Orlov, D.; Sprenger, F.; Grieser, M.; Repnow, R.; Hoffmann, J.; Wolf, A.

    2006-09-01

    XMM-Newton and Chandra observations of active galactic nuclei (AGN) show spectra rich with X-ray absorption features. These observations have detected a broad unresolved transition array (UTA) between 15-17 Å. This is attributed to inner-shell photoexcitation of M-shell iron ions. Modeling these UTA features is currently limited by uncertainties in the low-temperature dielectronic recombination (DR) data for M-shell iron. In order to resolve this issue, and to provide reliable iron M-shell DR data for plasma modeling, we are carrying out a series of laboratory measurements using the heavy-ion Test Storage Ring (TSR) at the Max-Plank-Institute for Nuclear Physics in Heidelberg, Germany. We use the DR data obtained at TSR, to calculate rate coefficients for plasma modeling. We are also providing our data to atomic theorist to benchmark their DR calculations. Here we report our recent experimental results for DR for several iron M-shell ions and plans for future work. This work has been supported in part by NASA, the German Federal Ministry for Education and Research, and the German Research Council

  3. Photometric AGN reverberation mapping - an efficient tool for BLR sizes, black hole masses and host-subtracted AGN luminosities

    CERN Document Server

    Haas, M; Ramolla, M; Nunez, F Pozo; Westhues, C; Watermann, R; Hoffmeister, V; Murphy, M

    2011-01-01

    Photometric reverberation mapping employs a wide bandpass to measure the AGN continuum variations and a suitable band, usually a narrow band (NB), to trace the echo of an emission line in the broad line region (BLR). The narrow band catches both the emission line and the underlying continuum, and one needs to extract the pure emission line light curve. We performed a test on two local AGNs, PG0003+199 (=Mrk335) and Ark120, observing well-sampled broad- (B, V) and narrow-band light curves with the robotic 15cm telescope VYSOS-6 on Cerro Armazones, Chile. In PG0003+199, H_alpha dominates the flux in the NB by 85%, allowing us to measure the time lag of H_alpha against B without the need to correct for the continuum contribution. In Ark120, H_beta contributes only 50% to the flux in the NB. The cross correlation of the B and NB light curves shows two distinct peaks of similar strength, one at lag zero from the autocorrelated continuum and one from the emission line at tau_cent = 47.5 +/- 3.4 days. We constructed...

  4. Type 1 AGN at low z. III. The optical narrow line ratios

    CERN Document Server

    Stern, Jonathan

    2012-01-01

    We present the optical narrow line ratios in an SDSS based sample of 3,175 broad Ha selected type 1 AGN, and explore their positions in the BPT diagrams as a function of the AGN and the host properties. We find the following: 1. The luminosities of all measured narrow lines (Ha, Hb, [OIII], [NII], [SII], [OI]) show a Baldwin relation relative to the broad Ha luminosity L_bHa, with slopes in the range of 0.53-0.72. 2. About 20% of the type 1 AGN reside within the `Composite' and `SF' regions of the BPT diagrams. These objects also show excess narrow Ha and UV luminosities, for their L_bHa, consistent with contribution from star formation which dominates the narrow lines emission, as expected from their positions in the BPT diagrams. 3. The type 1 which reside within the AGN region in the BPT diagrams, are offset to lower [SII]/Ha and [NII]/Ha luminosity ratios, compared to type 2 AGN. This offset is a selection effect, related to the lower AGN/host luminosity selection of the type 2 AGN selected from the SDSS ...

  5. Soft X-ray and Ultraviolet Emission Relations in Optically Selected AGN Samples

    CERN Document Server

    Strateva, I; Schneider, D; Vanden Berk, Daniel E; Vignali, C; Strateva, Iskra; Brandt, Niel; Schneider, Donald; Berk, Daniel Vanden; Vignali, Cristian

    2005-01-01

    Using a sample of 228 optically selected Active Galactic Nuclei (AGNs) in the 0.01-6.3 redshift range with a high fraction of X-ray detections (81-86%), we study the relation between rest-frame UV and soft X-ray emission and its evolution with cosmic time. The majority of the AGNs in our sample (155 objects) have been selected from the Sloan Digital Sky Survey (SDSS) in an unbiased way, rendering the sample results representative of all SDSS AGNs in particular, and highly complete optically selected AGN samples in general. The addition of two heterogeneous samples of 36 high-redshift and 37 low-redshift AGNs further supports and extends our conclusions. We confirm that the X-ray emission from AGNs is correlated with their UV emission, and that the ratio of the monochromatic luminosity emitted at 2keV compared to 2500A decreases with increasing luminosity (alpha_ox = -0.136l_uv+2.616, where l_uv is in log units), but does not change with cosmic time. These results apply to intrinsic AGN emission, as we correct...

  6. Disentangling star formation and AGN activity in powerful infrared luminous radio galaxies at 1 < z < 4

    Science.gov (United States)

    Drouart, G.; Rocca-Volmerange, B.; De Breuck, C.; Fioc, M.; Lehnert, M.; Seymour, N.; Stern, D.; Vernet, J.

    2016-09-01

    High-redshift radio galaxies present signs of both star formation and AGN activity, making them ideal candidates to investigate the connection and coevolution of AGN and star formation in the progenitors of present-day massive galaxies. We make use of a sample of 11 powerful radio galaxies spanning 1 relative contribution of the AGN and star formation by combining the galaxy evolution code PÉGASE.3 with an AGN torus model. We find that three components are necessary to reproduce the observed SEDs: an evolved and massive stellar component, a submm bright young starburst, and an AGN torus. We find that powerful radio galaxies form at very high-redshift, but experience episodic and important growth at 1 mass of the associated starburst varies from 5 to 50% of the total mass of the system. The properties of star formation differ from source to source, indicating no general trend of the star formation properties in the most infrared luminous high-redshift radio galaxies and no correlation with the AGN bolometric luminosity. Moreover, we find that AGN scattered light have a very limited impact on broad-band SED fitting on our sample. Finally, our analysis also suggests a wide range in origins for the observed star formation,which we partially constrain for some sources.

  7. Can we reproduce the X-ray background spectral shape using local AGN?

    CERN Document Server

    Vasudevan, Ranjan V; Gandhi, Poshak

    2013-01-01

    The X-ray background (XRB) is due to the aggregate of active galactic nuclei (AGN), which peak in activity at z~1 and is often modeled as the sum of different proportions of unabsorbed, moderately- and heavily-absorbed AGN. We present the summed spectrum of a complete sample of local AGN (the Northern Galactic Cap of the 58-month Swift/BAT catalog, z<0.2) using 0.4-200keV data and directly determine the different proportions of unabsorbed, moderately and heavily-absorbed AGN that make up the summed spectrum. This stacked low redshift AGN spectrum is remarkably similar in shape to the XRB spectrum (when shifted to z~1), but the observed proportions of different absorption populations differ from most XRB synthesis models. AGN with Compton-thick absorption account for only ~12% of the sample, but produce a significant contribution to the overall spectrum. We confirm that Compton reflection is more prominent in moderately-absorbed AGN and that the photon index differs intrinsically between unabsorbed and abso...

  8. AGN are cooler than you think: the intrinsic far-IR emission from QSOs

    CERN Document Server

    Symeonidis, M; Page, M J; Pearson, C; Bendo, G; Seymour, N; Oliver, S J

    2016-01-01

    We present an intrinsic AGN SED extending from the optical to the submm, derived with a sample of unobscured, optically luminous (vLv(5100)>10^43.5 erg/s) QSOs at z 10^43.5 erg/s). We note that for our sample of luminous QSOs, the average AGN emission is at least as high as, and mostly higher than, the total stellar powered emission at all wavelengths from the optical to the submm. This implies that in many galaxies hosting powerful AGN, there is no `safe' broadband photometric observation (at lambda<1000um) which can be used in calculating star-formation rates without subtracting the AGN contribution. Roughly, the AGN contribution may be ignored only if the intrinsic AGN luminosity at 5100 Ang is at least a factor of 4 smaller than the total infrared luminosity (L_IR; 8-1000um) of the galaxy. Finally, we examine the implication of our work in statistical studies of star-formation in AGN host galaxies.

  9. Morphologies of Radio, X-Ray, and Mid-Infrared Selected AGN

    CERN Document Server

    Griffith, Roger L

    2010-01-01

    We investigate the optical morphologies of candidate active galaxies identified at radio, X-ray, and mid-infrared wavelengths. We use the Advanced Camera for Surveys General Catalog (ACS-GC) to identify 372, 1360, and 1238 AGN host galaxies from the VLA, XMM-Newton and Spitzer Space Telescope observations of the COSMOS field, respectively. We investigate both quantitative (GALFIT) and qualitative (visual) morphologies of these AGN host galaxies, split by brightness in their selection band. We find that the radio-selected AGN are most distinct, with a very low incidence of having unresolved optical morphologies and a high incidence of being hosted by early-type galaxies. In comparison to X-ray selected AGN, mid-IR selected AGN have a slightly higher incidence of being hosted by disk galaxies. These morphological results conform with the results of Hickox et al. 2009 who studied the colors and large-scale clustering of AGN, and found a general association of radio-selected AGN with ``red sequence'' galaxies, mi...

  10. Binary Black Holes, Accretion Disks and Relativistic Jets: Photocenters of Nearby AGN and Quasars

    Science.gov (United States)

    Wehrle, Ann E.; Jones, Dayton L.; Meier, David L.; Piner, B. Glenn; Unwin, Stephen C.

    2004-01-01

    One of the most challenging questions in astronomy today is to understand the origin, structure, and evolution of the central engines in the nuclei of quasars and active galaxies (AGNs). The favoured theory involves the activation of relativistic jets from the fueling of a supermassive black hole through an accretion disk. In some AGN an outer optically thick, dusty torus is seen orbiting the black hole system. This torus is probably related to an inner accretion disk - black hole system that forms the actual powerhouse of the AGN. In radio-loud AGN two oppositely-directed radio jets are ejected perpendicular to the torus/disk system. Although there is a wealth of observational data on AGN, some very basic questions have not been definitively answered. The Space Interferometry Mission (SIM) will address the following three key questions about AGN. 1) Does the most compact optical emission from an AGN come from an accretion disk or from a relativistic jet? 2) Does the separation of the radio core and optical photocenter of the quasars used for the reference frame tie, change on the timescales of their photometric variability, or is the separation stable at the level of a few microarcseconds? 3) Do the cores of galaxies harbor binary supermassive black holes remaining from galaxy mergers? It is not known whether such mergers are common, and whether binaries would persist for a significant time.

  11. Incidence of WISE-Selected Obscured AGNs in Major Mergers and Interactions from the SDSS

    CERN Document Server

    Weston, Madalyn E; Brodwin, Mark; Mann, Justin; Cooper, Andrew; McConnell, Adam; Nielsen, Jennifer L

    2016-01-01

    We use the Wide-field Infrared Survey Explorer (WISE) and the Sloan Digital Sky Survey (SDSS) to confirm a connection between dust-obscured active galactic nuclei (AGNs) and galaxy merging. Using a new, volume-limited (z <= 0.08) catalog of visually-selected major mergers and galaxy-galaxy interactions from the SDSS, with stellar masses above 2x10^10 Msun, we find that major mergers (interactions) are 5-17 (3-5) times more likely to have red [3.4]-[4.6] colors associated with dust-obscured or `dusty' AGNs, compared to non-merging galaxies with similar masses. Using published fiber spectral diagnostics, we map the [3.4]-[4.6] versus [4.6]-[12] colors of different emission-line galaxies and find one-quarter of Seyferts have colors indicative of a dusty AGN. We find that AGNs are five times more likely to be obscured when hosted by a merging galaxy, half of AGNs hosted by a merger are dusty, and we find no enhanced frequency of optical AGNs in merging over non-merging galaxies. We conclude that undetected AGN...

  12. Cooling, AGN Feedback and Star Formation in Simulated Cool-Core Galaxy Clusters

    CERN Document Server

    Li, Yuan; Ruszkowski, Mateusz; Voit, G Mark; O'Shea, Brian W; Donahue, Megan

    2015-01-01

    Numerical simulations of active galactic nuclei (AGN) feedback in cool-core galaxy clusters have successfully avoided classical cooling flows, but often produce too much cold gas. We perform adaptive mesh simulations that include momentum-driven AGN feedback, self-gravity, star formation and stellar feedback, focusing on the interplay between cooling, AGN heating and star formation in an isolated cool-core cluster. Cold clumps triggered by AGN jets and turbulence form filamentary structures tens of kpc long. This cold gas feeds both star formation and the supermassive black hole (SMBH), triggering an AGN outburst that increases the entropy of the ICM and reduces its cooling rate. Within 1-2 Gyr, star formation completely consumes the cold gas, leading to a brief shutoff of the AGN. The ICM quickly cools and redevelops multiphase gas, followed by another cycle of star formation/AGN outburst. Within 6.5 Gyr, we observe three such cycles. There is good agreement between our simulated cluster and the observations...

  13. Light water reactor safety

    CERN Document Server

    Pershagen, B

    2013-01-01

    This book describes the principles and practices of reactor safety as applied to the design, regulation and operation of light water reactors, combining a historical approach with an up-to-date account of the safety, technology and operating experience of both pressurized water reactors and boiling water reactors. The introductory chapters set out the basic facts upon which the safety of light water reactors depend. The central section is devoted to the methods and results of safety analysis. The accidents at Three Mile Island and Chernobyl are reviewed and their implications for light wate

  14. Nuclear reactor physics

    CERN Document Server

    Stacey, Weston M

    2010-01-01

    Nuclear reactor physics is the core discipline of nuclear engineering. Nuclear reactors now account for a significant portion of the electrical power generated worldwide, and new power reactors with improved fuel cycles are being developed. At the same time, the past few decades have seen an ever-increasing number of industrial, medical, military, and research applications for nuclear reactors. The second edition of this successful comprehensive textbook and reference on basic and advanced nuclear reactor physics has been completely updated, revised and enlarged to include the latest developme

  15. Dissecting galaxies: spatial and spectral separation of emission excited by star formation and AGN activity

    Science.gov (United States)

    Davies, Rebecca L.; Groves, Brent; Kewley, Lisa J.; Dopita, Michael A.; Hampton, Elise J.; Shastri, Prajval; Scharwächter, Julia; Sutherland, Ralph; Kharb, Preeti; Bhatt, Harish; Jin, Chichuan; Banfield, Julie; Zaw, Ingyin; James, Bethan; Juneau, Stéphanie; Srivastava, Shweta

    2016-10-01

    The optical spectra of Seyfert galaxies are often dominated by emission lines excited by both star formation and active galactic nucleus (AGN) activity. Standard calibrations (such as for the star formation rate) are not applicable to such composite (mixed) spectra. In this paper, we describe how integral field data can be used to spectrally and spatially separate emission associated with star formation from emission associated with accretion on to an AGN. We demonstrate our method using integral field data for two AGN host galaxies (NGC 5728 and NGC 7679) from the Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7). The spectra of NGC 5728 and NGC 7679 form clear sequences of AGN fraction on standard emission line ratio diagnostic diagrams. We show that the emission line luminosities of the majority (>85 per cent) of spectra along each AGN fraction sequence can be reproduced by linear superpositions of the emission line luminosities of one AGN dominated spectrum and one star formation dominated spectrum. We separate the Hα, Hβ, [N II]λ6583, [S II]λλ6716, 6731, [O III]λ5007 and [O II]λλ3726, 3729 luminosities of every spaxel into contributions from star formation and AGN activity. The decomposed emission line images are used to derive the star formation rates and AGN bolometric luminosities for NGC 5728 and NGC 7679. Our calculated values are mostly consistent with independent estimates from data at other wavelengths. The recovered star-forming and AGN components also have distinct spatial distributions which trace structures seen in high-resolution imaging of the galaxies, providing independent confirmation that our decomposition has been successful.

  16. The radio luminosity function and redshift evolution of radio-mode and quasar-mode AGN

    Science.gov (United States)

    Pracy, Mike

    2016-08-01

    The properties of the AGN population indicate that there are two fundamentally different accretion modes operating. In the quasar-mode, material is accreted onto the supermassive black hole via a small, thin, optically luminous accretion disc. Accretion in this mode is recognisable by emission lines in the optical spectrum. However, there is a population of AGN observable only by their radio emission and without optical emission lines. These radio-mode AGN are likely powered by radiatively inefficient accretion from a hot gas halo. I will describe the cosmic evolution of these two populations via radio luminosity functions. The radio luminosity functions are constructed from a new survey of over 4000 radio galaxies out to z=1, all with confirmed redshifts and their accretion mode classified from their optical spectra. This is 20 times larger than the only other survey used to make such a measurement. The radio-mode AGN population displays no statistically significant evolution in space density out to redshift z=1. In contrast the quasar mode AGN exhibits rapid evolution in space density, increasing by a factor of 8 over the same redshift range. The characteristic break in the radio luminosity function occurs at a significantly higher power for the quasar-mode AGN in comparison to the radio-mode AGN and we demonstrate this is consistent with the two populations representing fundamentally different accretion modes. The radio luminosity function is used to estimate the total amount of mechanical energy available for radio mode feedback as a function of redshift, and is found to be in good agreement with cosmological models and previous measurements. Again, by separating by accretion mode, the previously estimated increase in available mechanical energy per unit volume out to z=1 (approximately a factor of 2) can be attributed to the rapid evolution of the quasar-mode AGN, while for the classical radio-mode AGN the total mechanical energy output remains roughly

  17. Unravelling ICM Physics and AGN Feedback with Deep Chandra Observations of NGC 5813

    Science.gov (United States)

    Randall, Scott; Nulsen, Paul; Jones, Christine; Forman, William; Clarke, Tracy

    2015-09-01

    We present results based on very deep (650 ks) Chandra observations of the galaxy group NGC 5813. This system shows three pairs of collinear cavities, with each pair associated with an elliptical AGN outburstshock. Due to the relatively regular morphology of this system, and the unique unambiguous detection of three distinct AGN outburstshocks, it is particularly well-suited for the study of AGN feedbackand the AGN outburst history. The implied mean kinetic power is roughly the same for each outburst, demonstrating that the average AGN kinetic luminosity can remain stable over long timescales (roughly 50Myr). The two older outbursts have larger, roughly equal total energies as compared with the youngest outburst, implying that the youngest outburst is ongoing. We find that the radiative cooling rate and the mean shock heating rate of the gas are well balanced at each shock front, suggesting that AGN outburst shock heating alone is sufficient to offset cooling and establish AGN/ICM feedback within at least the central 30 kpc. This heating takes place roughly isotropically and most strongly at small radii, as is required for feedback to operate. We suggest that shock heating may play a significant role in AGN feedback at smaller radii in other systems, where weak shocks are more difficult to detect. We find non-zero shockfront widths that are too large to be explained by particle diffusion. Instead, all measured widths are consistent with shock broadening due to propagation through a turbulent ICM with a mean turbulent speed of roughly 70 km/s. Significant contributions to our understanding of AGN feedback and ICM physics, partially via studies similar to the one described here, will be one of the major achievements of the Athena mission.

  18. Spinning fluids reactor

    Science.gov (United States)

    Miller, Jan D; Hupka, Jan; Aranowski, Robert

    2012-11-20

    A spinning fluids reactor, includes a reactor body (24) having a circular cross-section and a fluid contactor screen (26) within the reactor body (24). The fluid contactor screen (26) having a plurality of apertures and a circular cross-section concentric with the reactor body (24) for a length thus forming an inner volume (28) bound by the fluid contactor screen (26) and an outer volume (30) bound by the reactor body (24) and the fluid contactor screen (26). A primary inlet (20) can be operatively connected to the reactor body (24) and can be configured to produce flow-through first spinning flow of a first fluid within the inner volume (28). A secondary inlet (22) can similarly be operatively connected to the reactor body (24) and can be configured to produce a second flow of a second fluid within the outer volume (30) which is optionally spinning.

  19. Progress report within the series of GRS-F progress reports on reactor safety, sponsored by the Federal Ministry of Economics and Labour. Period: 1 July - 31 December 2003; Berichte ueber vom Bundesministerium fuer Wirtschaft und Arbeit gefoerderte Forschungsvorhaben auf dem Gebiet der Reaktorsicherheit. Berichtszeitraum: 01. Juli - 31. Dezember 2003

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2004-07-01

    The Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, by order of the BMWi, continuously issues information on the status of the investigations into the safety of nuclear power plants by publishing semi-annual and annual progress reports within the series of GRS-F-Fortschrittsberichte (GRS-F-Progress Reports). Each progress report represents a compilation of individual reports about the objectives, work performed, results achieved, next steps of the work etc. The individual reports are prepared in a standard form by the research organisations themselves as documentation of their progress in work and are published by the Research Management Division of GRS within the framework of general information on the progress in reactor safety research. The compilation of the reports is classified according to general topics related to reactor safety research. Further, use is made of the classification system ''Joint Safety Research Index'' of the CEC (commission of the european communities). The reports are arranged in sequence of their project numbers. (orig.) [German] Die Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH informiert im Auftrag des BMWi halbjaehrlich und jaehrlich ueber den Stand der Untersuchungen zur Sicherheit von Kernreaktoren in den Fortschrittsberichten der GRS-F-Berichtsreihe. Jeder Fortschrittsbericht stellt eine Sammlung von Einzelberichten ueber Zielsetzung, durchgefuehrte Arbeiten, erzielte Ergebnisse, geplante Weiterarbeit etc. dar, die von den Forschungsstellen selbst als Dokumentation ihres Arbeitsfortschritts in einheitlicher Form erstellt und von der Forschungsbetreuung (FB) in der GRS im Rahmen der allgemeinen Information ueber die Fortschritte von Untersuchungen zur Reaktorsicherheit herausgegeben werden. Die inhaltliche Gliederung der Berichtssammlung erfolgt durch sachliche Zuordnung der Vorhaben zu uebergeordneten Themenbereichen der Reaktorsicherheitsforschung, ferner nach dem Klassifikationsschema

  20. VizieR Online Data Catalog: RM AGNs accretion rates and BH masses (Du+, 2016)

    Science.gov (United States)

    Du, P.; Wang, J.-M.; Hu, C.; Ho, L. C.; Li, Y.-R.; Bai, J.-M.

    2016-05-01

    We select all AGNs with reverberation mapping (RM) data (here only broad Hβ line), which yield robust BH mass estimates needed for our analysis. All RM AGNs before 2013 are summarized by Bentz et al. (2013ApJ...767..149B). Our project to search for super-Eddington accreting massive black holes (SEAMBHs) has monitored about 25 candidates and successfully measured Hβ lags ({tau}Hβ) in 14 AGNs to date (Du et al. 2015, J/ApJ/806/22) and other five objects monitored between 2014 and 2015 (to be submitted). See section 2 for further explanations. (2 data files).

  1. The host galaxies and narrow-line regions of four double-peaked [OIII] AGNs

    Energy Technology Data Exchange (ETDEWEB)

    Villforth, Carolin; Hamann, Fred [Department of Astronomy, University of Florida, 32611 Gainesville, FL (United States)

    2015-03-01

    Major gas-rich mergers of galaxies are expected to play an important role in triggering and fueling luminous active galactic nuclei (AGNs). The mechanism of AGN fueling during mergers, however, remains poorly understood. We present deep multi-band (u/r/z) imaging and long-slit spectroscopy of four double-peaked [OIII] emitting AGNs. This class of object is likely associated with either kiloparsec-separated binary AGNs or final stage major mergers, although AGNs with complex narrow-line regions (NLRs) are known contaminants. Such objects are of interest since they represent the onset of AGN activity during the merger process. Three of the four double-peaked [OIII] emitters studied have been confirmed as major mergers using near-infrared imaging and one is a confirmed X-ray binary AGN. All AGNs are luminous, radio-quiet to radio-intermediate, and have redshifts of 0.1AGN suggests that the merger of a binary black hole can take longer than 1 Gyr. All AGNs hosted by merging galaxies have companions at distances ⩽150 kpc. The NLRs have large sizes (10 kpc < r < 100 kpc) and consist of compact clumps with considerable relative velocities between components (∼200–650 km s{sup −1}). We detect broad, predominantly blue, wings with velocities up to ∼1500 km s{sup −1} in [OIII], indicative of powerful outflows. The outflows are compact (<5 kpc) and co-spatial with nuclear regions showing considerable reddening, consistent with enhanced star formation. One source shows an offset between gas and stellar kinematics, consistent with either a bipolar flow or a counter-rotating gas disk. In all other sources, the ionized gas

  2. FERO (Finding Extreme Relativistic Objects: statistics of relativistic broad Fe K lines in AGN

    Directory of Open Access Journals (Sweden)

    A. L. Longinotti

    2008-01-01

    Full Text Available Las propiedades de las líneas de emisión Fe Kα ensanchadas relativísticamente en núcleos activos de galaxias (AGN son aún materia de debate en la comunidad. Los trabajos recientes parecen excluir que la línea ancha de Fe es un rasgo común en los AGN. Se presenta el análisis de una gran muestra de 157 observaciones de archivo del XMM-Newton de AGN radio callados. Este trabajo en curso es lo desarrollado desde lo reportado en Guainazzi et al. (2006.

  3. Fitting Spectral Energy Distributions of AGN - A Markov Chain Monte Carlo Approach

    CERN Document Server

    Rivera, Gabriela Calistro; Hennawi, Joseph F; Hogg, David W

    2014-01-01

    We present AGNfitter: a Markov Chain Monte Carlo algorithm developed to fit the spectral energy distributions (SEDs) of active galactic nuclei (AGN) with different physical models of AGN components. This code is well suited to determine in a robust way multiple parameters and their uncertainties, which quantify the physical processes responsible for the panchromatic nature of active galaxies and quasars. We describe the technicalities of the code and test its capabilities in the context of X-ray selected obscured AGN using multiwavelength data from the XMM-COSMOS survey.

  4. Exposures series

    OpenAIRE

    Stimson, Blake

    2011-01-01

    Reaktion Books’ Exposures series, edited by Peter Hamilton and Mark Haworth-Booth, is comprised of 13 volumes and counting, each less than 200 pages with 80 high-quality illustrations in color and black and white. Currently available titles include Photography and Australia, Photography and Spirit, Photography and Cinema, Photography and Literature, Photography and Flight, Photography and Egypt, Photography and Science, Photography and Africa, Photography and Italy, Photography and the USA, P...

  5. Supply of enriched uranium for research reactors

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, H. [NUKEM GmbH, Alzenau (Germany)

    1997-08-01

    Since the RERTR-meeting In Newport/USA in 1990 the author delivered a series of papers in connection with the fuel cycle for research reactors dealing with its front-end. In these papers the author underlined the need for unified specifications for enriched uranium metal suitable for the production of fuel elements and made proposals with regard to the re-use of in Europe reprocessed highly enriched uranium. With regard to the fuel cycle of research reactors the research reactor community was since 1989 more concentrating on the problems of its back-end since the USA stopped the acceptance of spent research reactor fuel on December 31, 1988. Now, since it is apparent that these back-end problem have been solved by AEA`s ability to reprocess and the preparedness of the USA to again accept physically spent research reactor fuel the author is focusing with this paper again on the front-end of the fuel cycle on the question whether there is at all a safe supply of low and high enriched uranium for research reactors in the future.

  6. Reactor Vessel Surveillance Program for Advanced Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Kyeong-Hoon; Kim, Tae-Wan; Lee, Gyu-Mahn; Kim, Jong-Wook; Park, Keun-Bae; Kim, Keung-Koo

    2008-10-15

    This report provides the design requirements of an integral type reactor vessel surveillance program for an integral type reactor in accordance with the requirements of Korean MEST (Ministry of Education, Science and Technology Development) Notice 2008-18. This report covers the requirements for the design of surveillance capsule assemblies including their test specimens, test block materials, handling tools, and monitors of the surveillance capsule neutron fluence and temperature. In addition, this report provides design requirements for the program for irradiation surveillance of reactor vessel materials, a layout of specimens and monitors in the surveillance capsule, procedures of installation and retrieval of the surveillance capsule assemblies, and the layout of the surveillance capsule assemblies in the reactor.

  7. Gravitational Redshift of Emission Lines in the AGN Spectra

    CERN Document Server

    Bon, Nataša; Marziani, Paola; Jovanović, Predrag

    2016-01-01

    The detection of gravitationally redshifted optical emission lines has been reported just for a few active galaxies. In this paper we give a short overview of studies that analyzed or exploited the detection of the gravitational redshift in optical AGN spectra. In addition, we tested the consistency of gravitational redshift as the physical origin of the redward shifts observed in their spectra using a sample of $\\approx$ 50 Hamburg-ESO intermediate to high redshift quasars that are among the most luminous quasars known ($10^{47} \\lesssim L \\lesssim 10^{48}$ erg/s), and are expected to host very massive black holes. To this aim we modeled the line profile with accretion disk models around a black hole.

  8. Fossil shell emission in dying radio loud AGNs

    CERN Document Server

    Kino, M; Kawakatu, N; Orienti, M; Nagai, H; Wajima, K; Itoh, R

    2015-01-01

    We investigate shell emission associated with dying radio loud AGNs. First, based on our recent work by Ito et al. (2015), we describe the dynamical and spectral evolutions of shells after stopping the jet energy injection. We find that the shell emission overwhelms that of the radio lobes soon after stopping the jet energy injection because fresh electrons are continuously supplied into the shell via the forward shock while the radio lobes rapidly fade out without jet energy injection. We find that such fossil shells can be a new class of target sources for SKA telescope. Next, we apply the model to the nearby radio source 3C84. Then, we find that the fossil shell emission in 3C84 is less luminous in radio band while it is bright in TeV gamma-ray band and it can be detectable by CTA.

  9. Broad Iron Lines in AGN and X-ray Binaries

    CERN Document Server

    Fabian, A C

    2004-01-01

    Several AGN and black hole X-ray binaries show a clear very broad iron line which is strong evidence that the black holes are rapidly spinning. Detailed analysis of these objects shows that the emission line is not significantly affected by absorption and that the source variability is principally due to variation in amplitude of a power-law. Underlying this is a much less variable, relativistically-smeared, reflection-dominated, component which carries the imprint of strong gravity at a few gravitational radii. The strong gravitational light bending in these regions then explains the power-law variability as due to changes in height of the primary X-ray source above the disc. The reflection component, in particular its variability and the profile of the iron line, enables us to study the innermost regions around an accreting, spinning, black hole.

  10. X-ray variability with WFXT: AGNs, transients and more

    CERN Document Server

    Paolillo, Maurizio; Allevato, Viola; de Martino, Domitilla; della Valle, Massimo; Papadakis, Iossif; Gilli, Roberto; Tozzi, Paolo

    2010-01-01

    The Wide Field X-ray Telescope (WFXT) is a proposed mission with a high survey speed, due to the combination of large field of view (FOV) and effective area, i.e. grasp, and sharp PSF across the whole FOV. These characteristics make it suitable to detect a large number of variable and transient X-ray sources during its operating lifetime. Here we present estimates of the WFXT capabilities in the time domain, allowing to study the variability of thousand of AGNs with significant detail, as well as to constrain the rates and properties of hundreds of distant, faint and/or rare objects such as X-ray Flashes/faint GRBs, Tidal Disruption Events, ULXs, Type-I bursts etc. The planned WFXT extragalactic surveys will thus allow to trace variable and transient X-ray populations over large cosmological volumes.

  11. Optical Spectroscopic ATLAS of the MOJAVE/2cm AGN Sample

    CERN Document Server

    Torrealba, Janet; Cruz-González, Irene; Arshakian, Tigran G; Bertone, Emanuele; Rosa-González, Daniel

    2011-01-01

    We present an optical spectroscopic atlas at intermediate resolution (8 -15 A) for 124 core-dominated radio-loud active galactic nuclei with relativistic jets, drawn from the MOJAVE/2cm sample at 15GHz. It is the first time that spectroscopic and photometric parameters for a large sample of such type of AGN are presented. The atlas includes spectral parameters for the emission lines Hbeta, [O III] 5007, Mg II 2798 and/or C IV 1549 and corresponding data for the continuum, as well as the luminosities and equivalent widths of the Fe II UV/optical. It also contains the homogeneous photometric information in the B-band for 242 sources of the sample, with a distribution peak at BJ=18.0 and a magnitude interval of 11.1< BJ <23.7.

  12. Relativistic Effects on Reflection X-ray Spectra of AGN

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Khee-Gan; /University Coll. London; Fuerst, Steven V.; /KIPAC, Menlo Park; Brandwardi-Raymond, Graziella; Wu, Kinwah; Crowley, Oliver; /University Coll. London

    2007-01-05

    We have calculated the reflection component of the X-ray spectra of active galactic nuclei (AGN) and shown that they can be significantly modified by the relativistic motion of the accretion flow and various gravitational effects of the central black hole. The absorption edges in the reflection spectra suffer severe energy shifts and smearing. The degree of distortion depends on the system parameters, and the dependence is stronger for some parameters such as the inner radius of the accretion disk and the disk viewing inclination angles. The relativistic effects are significant and are observable. Improper treatment of the reflection component of the X-ray continuum in spectral fittings will give rise to spurious line-like features, which will mimic the fluorescent emission lines and mask the relativistic signatures of the lines.

  13. High-Velocity Bipolar Molecular Emission from an AGN Torus

    CERN Document Server

    Gallimore, Jack F; Maiolino, Roberto; Marconi, Alessandro; O'Dea, Christopher P; Lutz, Dieter; Baum, Stefi A; Nikutta, Robert; Impellizzeri, C M V; Davies, Richard; Kimball, Amy E; Sani, Eleonora

    2016-01-01

    We have detected in ALMA observations CO J = 6 - 5 emission from the nucleus of the Seyfert galaxy NGC 1068. The low-velocity (up to +/- 70 km/s relative to systemic) CO emission resolves into a 12x7 pc structure, roughly aligned with the nuclear radio source. Higher-velocity emission (up to +/- 400 km/s) is consistent with a bipolar outflow in a direction nearly perpendicular (roughly 80 degrees) to the nuclear disk. The position-velocity diagram shows that in addition to the outflow, the velocity field may also contain rotation about the disk axis. These observations provide compelling evidence in support of the disk-wind scenario for the AGN obscuring torus.

  14. The Galactic Center - an AGN on a starvation diet

    CERN Document Server

    Biermann, P L; Biermann, Heino Falcke & Peter L.

    1993-01-01

    The Galactic Center shows evidence for the presence of three important AGN ingredients: a Black Hole ($M_\\bullet\\sim10^6M_\\odot$), an accretion disk ($10^{-8.5} - 10^{-7} M_\\odot/{\\rm yr}$) and a powerful jet (jet power $\\ge$ 10\\% disk luminosity). However, the degree of activity is very low and can barely account for the energetics of the whole central region. Neverthelss, in the very inner arsecond the central engine becomes dominant and provides an interesting laboratory for the physics of central engines (Black Holes) in galactic nuclei. We therefore give an overall picture of the central arcsecond where we link the radio emission and the heating of the ambient medium to a weakly accreting disk surrounding a massive Black Hole.

  15. AGN Spectral Energy Distributions of GLAST Telescope Network Program Objects

    Science.gov (United States)

    Adkins, Jeff; Lacy, Mark; Daou, Doris; Rapp, Steve; Stefaniak, Linda

    2005-03-01

    The Gamma-Ray Large Area Space Telescope (GLAST) has a proposed observing list that includes AGNs and Polars bright enough to be observed optically by amateurs and students. This observing list is maintained by the "GLAST Telescope Network" (GTN) and includes a number of objects that have yet to be observed by the Spitzer Space Telescope. Our project will observe one of these objects with the Spitzer MIPS and the IRAC instruments to determine their Spectral Energy Distribution (SED), which will be compared to a computer model of disk emission in order to determine what component of the SED is due to the disk and what component is due to synchrotron radiation induced by the jets. In addition we will observe our program objects prior to, simultaneously with, and after Spitzer observes them. This gives a direct connection from Spitzer research to student activities in the classroom.

  16. Preselecting AGN candidates from multi-wavelength data by ADTree

    Science.gov (United States)

    Zhang, Yanxia; Zheng, Hongwen; Zhao, Yongheng

    2005-03-01

    With the information era in astronomy coming, this "data avalanche" may provide many answers to important problems in contemporary astrophysics. The most important problem is sifting through massive amounts of data to mine knowledge. In this paper, we positionally cross-identify multi-wavelength data from optical, near-infrared, and x-ray bands, and then employ alternating decision trees (adtree) to quickly and robustly separate AGN candidates to a high degree of accuracy. We emphasise the application of the method due to the development of large survey projects and the establishment of the virtual observatory, and conclude that the application of data mining algorithms in astronomy is of great importance to discover new knowledge impossible to obtain before, and promote the development of astronomy.

  17. A mixture evolution scenario of AGN radio luminosity function

    CERN Document Server

    Yuan, Zunli; Zhou, Ming; Mao, Jirong

    2016-01-01

    We propose a mixture evolution scenario to model the evolution of the steep spectrum AGN (active galactic nuclear) radio luminosity function (RLF) based on a Bayesian method. In this scenario, the shape of RLF is determined together by the density and luminosity evolution. Our models indicate that the density evolution is positive until a redshift of $\\thicksim 0.9$ and then turns to be negative, while the luminosity evolution is positive to a higher redshift ($z \\thicksim 5$ for model B and $z \\thicksim 3.5$ for model C) and then turns to be negative. Our mixture evolution model works well, and the modeled RLFs are in good agreement with previous determinations. The mixture evolution scenario can naturally explain the luminosity dependent evolution of the RLFs.

  18. The COSMOS AGN Spectroscopic Survey I: XMM Counterparts

    CERN Document Server

    Trump, Jonathan R; Elvis, Martin; McCarthy, Patrick J; Huchra, John P; Brusa, Marcella; Salvato, Mara; Capak, Peter; Cappelluti, Nico; Civano, Francesca; Comastri, Andrea; Gabor, Jared; Hao, Heng; Hasinger, Gunther; Jahnke, Knud; Kelly, Brandon C; Lilly, Simon J; Schinnerer, Eva; Scoville, Nick Z; Smolcic, Vernesa

    2008-01-01

    We present optical spectroscopy for an X-ray and optical flux-limited sample of 677 XMM-Newton selected targets covering the 2 deg^2 COSMOS field, with a yield of 485 high-confidence redshifts. The majority of the spectra were obtained over three seasons (2005-2007) with the IMACS instrument on the Magellan (Baade) telescope. We also include in the sample previously published Sloan Digital Sky Survey spectra and supplemental observations with MMT/Hectospec. We detail the observations and classification analyses. The survey is 90% complete to flux limits of f_{0.5-10 keV}>8 x 10^-16 erg cm^-2 s^-1 and i_AB+3 x 10^42 erg s^-1) to z<1, of both optically obscured and unobscured types. We find statistically significant evidence that the obscured to unobscured AGN ratio at z<1 increases with redshift and decreases with luminosity.

  19. AGNs as main contributors to the UV ionizing emissivity at high redshifts: predictions from a Lambda-CDM model with linked AGN/galaxy evolution

    CERN Document Server

    Giallongo, E; Fiore, F; Castellano, M; Fontana, A; Grazian, A; Pentericci, L

    2012-01-01

    We have evaluated the contribution of the AGN population to the ionization history of the Universe based on a semi-analytic model of galaxy formation and evolution in the CDM cosmological scenario. The model connects the growth of black holes and of the ensuing AGN activity to galaxy interactions. In the model we have included a self consistent physical description of the escape of ionizing UV photons; this is based on the blast-wave model for the AGN feedback we developed in a previous paper to explain the distribution of hydrogen column densities in AGNs of various redshifts and luminosities, due to absorption by the host galaxy gas. The model predicts UV luminosity functions for AGNs which are in good agreement with those derived from the observations especially at low and intermediate redshifts (z=3). At higher redshifts (z>5) the model tends to overestimate the data at faint luminosities. Critical biases both in the data and in the model are discussed to explain such apparent discrepancies. The predicted...

  20. Estimates of AGN Black Hole Mass and Minimum Variability Timescale

    Institute of Scientific and Technical Information of China (English)

    Guang-Zhong Xie; Luo-En Chen; Huai-Zhen Li; Li-Sheng Mao; Hong Dai; Zhao-Hua Xie; Li Ma; Shu-Bai Zhou

    2005-01-01

    Black hole mass is one of the fundamental physical parameters of active galactic nuclei (AGNs), for which many methods of estimation have been proposed.One set of methods assumes that the broad-line region (BLR) is gravitationally bound by the central black hole potential, so the black hole mass can be estimated from the orbital radius and the Doppler velocity. Another set of methods assumes the observed variability timescale is determined by the orbital timescale near the innermost stable orbit around the Schwarzschild black hole or the Kerr black hole,or by the characteristic timescale of the accretion disk. We collect a sample of 21AGNs, for which the minimum variability timescales have been obtained and their black hole masses (Mσ) have been well estimated from the stellar velocity dispersion or the BLR size-luminosity relation. Using the minimum variability timescales we estimated the black hole masses for 21 objects by the three different methods,the results are denoted by Ms, Mk and Md, respectively. We compared each of them with Mσ individually and found that: (1) using the minimum variability timescale with the Kerr black hole theory leads to small differences between Mσand Mk, none exceeding one order of magnitude, and the mean difference between them is about 0.53 dex; (2) using the minimum variability timescale with the Schwarzschild black hole theory leads to somewhat larger difference between Mσ and Ms: larger than one order of magnitude for 6 of the 21 sources, and the mean difference is 0.74 dex; (3) using the minimum variability timescale with the accretion disk theory leads to much larger differences between Mσ and Md, for 13of the 21 sources the differences are larger than two orders of magnitude; and the mean difference is as high as about 2.01 dex.

  1. X-ray variability in AGN: LINER vs. Seyfert 2

    Science.gov (United States)

    Hernandez-Garcia, Lorena; Masegosa, Josefa; Gonzalez-Martin, Omaira; Marquez, Isabel

    2015-09-01

    Although variability is a general property characterizing active galactic nuclei (AGN), it is not well stablished if the changes occur in the same way in every nuclei . The main purpose of this work is to study the X-ray variability pattern(s) in low luminosity AGN in a large sample, including 18 low ionization nuclear emission line regions (LINERs) and 26 type 2 Seyferts (Sy2), using the public archives in Chandra and/or XMM-Newton. Spectra of the same source gathered at different epochs were simultaneously fitted to study long term variations, whereas the variability patterns were studied allowing different parameters to vary during the spectral fit. Whenever possible, short term variations from the analysis of the light curves and long term UV flux variability were studied. Short term variations are not found at X-rays, but variations in timescales of months/years is very common in both families. The main driver of the long term X-ray variations seems to be related to changes in the nuclear power in both LINERs and Sy2, but other variability patterns cannot be discarded in a few cases, because changes of the column density or at soft energies are also found. The X-ray variations occur in the same way in LINERs and type 2 Seyferts, i.e., related to the nuclear continuum, but they might have different accretion mechanisms. As absorption variations and changing-look sources are not observed in LINERs, but UV nuclear variations are common, we speculate that the BLR and the torus might disappear in these sources.

  2. The AGN Content of the Micron all Sky Survey

    Science.gov (United States)

    Cutri, R. M.

    2000-01-01

    The Two Micron All Sky Survey (2MASS) began routine operations from its northern facility on Mt. Hopkins, AZ in June of 1997, and from its southern facility on Cerro Tololo, Chile in March of 1998. At each site, highly automated 1.3 m telescopes equipped with identical 3-channel cameras, are systematically imaging the sky in three near infrared wavelength bands, J (1.25 um), H (1.65 um) and K-s (2.17 um). The Survey will ultimately produce an Image Atlas containing nearly two million 512 x 1024 pixel images (1 arcsec/pix) in the three colors, a highly complete and reliable catalog containing approx. 300 million point sources having SNR greater than 10 photometry at J less or = 15.8, H less or = 15.1 and K-s less or = 14.3 mag. and an astrometric accuracy greater than 0.511 RMS, and a catalog of 1-2 million resolved sources, primarily galaxies, having SNR greater than 10 photometric accuracy at J less than or = 15.5, H less than or = 14.8 and K-s less than or = 13.5 mag. The 2MASS Sampler, an introductory set of data, was released to the community in December of 1998 (see http://www.ipac.caltech.edu/2mass/). We review the near IR and optical/IR properties of "conventional" QSOs from UV and optical samples, and estimate the number that will be detected by 2MASS. We also discuss 2MASS's ability to test for for new populations of extremely red AGN that have been missed by UV and Visual surveys, as suggested by from IRAS and radio studies. Results of spectroscopic follow-up of 2MASS-selected new AGN candidates will also be presented.

  3. Searching for Short Term Variable Active Galactic Nuclei: A Vital Step Towards Using AGN as Standard Candles

    Science.gov (United States)

    Kilts, Kelly; Gorjian, Varoujan; Rutherford, Thomas; Kohrs, Russell; Urbanowski, Vincent; Bellusci, Nina; Horton, Savannah; Jones, Dana; Jones, Kaytlyn; Pawelski, Peter; Tranum, Haley; Zhang, Emily

    2017-01-01

    Current models for accretion disk sizes of active galactic nuclei (AGN) do not match the limited observational data available, so there is an active need from the modeling community for many more accretion disk/dusty torus reverberation mapping campaigns with which to better calibrate models. Since short term variable AGN can be more easily monitored for reverberation mapping than long term variable AGN, they can begin to provide data more quickly. This project looked for short term variable AGN in the Young Stellar Object Variability (YSOVAR) survey conducted using the Spitzer Space Telescope. The YSOVAR survey targeted 12 nearby star forming regions for repeated observations. Potential AGN from the YSOVAR data were first selected by color ([3.6] - [4.5] > 0.4) and then by magnitude (m < 14) based on previous Spitzer surveys of known AGN. Since AGN share some similar color characteristics with young stars, images of each YSOVAR region were viewed to remove potential objects near concentrations of known young stellar objects since these were likely also YSOs. The spectral energy distribution (SED) for each remaining potential AGN was then examined for AGN like characteristics. Several potential short term variable AGN were found.

  4. The 60 Month All-Sky Burst Alert Telescope Survey of Active Galactic Nucleus and the Anisotropy of Nearby AGNs

    Science.gov (United States)

    Ajello, M.; Alexander, D. M.; Greiner, J.; Madejeski, G. M.; Gehrels, N.; Burlon, D.

    2014-01-01

    Surveys above 10 keV represent one of the best resources to provide an unbiased census of the population of active galactic nuclei (AGNs). We present the results of 60 months of observation of the hard X-ray sky with Swift/Burst Alert Telescope (BAT). In this time frame, BAT-detected (in the 15-55 keV band) 720 sources in an all-sky survey of which 428 are associated with AGNs, most of which are nearby. Our sample has negligible incompleteness and statistics a factor of approx. 2 larger over similarly complete sets of AGNs. Our sample contains (at least) 15 bona fide Compton-thick AGNs and 3 likely candidates. Compton-thick AGNs represent approx. 5% of AGN samples detected above 15 keV. We use the BAT data set to refine the determination of the log N-log S of AGNs which is extremely important, now that NuSTAR prepares for launch, toward assessing the AGN contribution to the cosmic X-ray background. We show that the log N-log S of AGNs selected above 10 keV is now established to approx. 10% precision. We derive the luminosity function of Compton-thick AGNs and measure a space density of 7.9(+4.1/-2.9)× 10(exp -5)/cubic Mpc for objects with a de-absorbed luminosity larger than 2 × 10(exp 42) erg / s. As the BAT AGNs are all mostly local, they allow us to investigate the spatial distribution of AGNs in the nearby universe regardless of absorption. We find concentrations of AGNs that coincide spatially with the largest congregations of matter in the local (much < 85 Mpc) universe. There is some evidence that the fraction of Seyfert 2 objects is larger than average in the direction of these dense regions..

  5. AGN-starburst evolutionary connection : a physical interpretation based on radiative feedback

    CERN Document Server

    Ishibashi, W

    2016-01-01

    Observations point towards a close connection between nuclear starbursts, active galactic nuclei (AGN), and outflow phenomena. An evolutionary sequence, starting from a dust-obscured ultra-luminous infrared galaxy and eventually leading to an unobscured optical quasar, has been proposed and discussed in the literature. AGN feedback is usually invoked to expel the obscuring gas and dust in a blow-out event, but the underlying physical mechanism remains unclear. We consider AGN feedback driven by radiation pressure on dust, which directly acts on the obscuring dusty gas. We obtain that radiative feedback can potentially disrupt dense gas in the infrared-optically thick regime, and that an increase in the dust-to-gas fraction leads to an increase in the effective Eddington ratio. Thus the more dusty gas is preferentially expelled by radiative feedback, and the central AGN is prone to efficiently remove its own obscuring dust cocoon. Large amounts of dust imply heavy obscuration but also powerful feedback, sugges...

  6. Fossil Galaxy Groups -- Ideal Laboratories for Studying the Effects of AGN Heating

    CERN Document Server

    Jetha, Nazirah N; Raychaudhury, Somak; Sengupta, Chandreyee; Hardcastle, Martin

    2009-01-01

    We present the first of a sample of fossil galaxy groups with pre-existing Chandra and/or XMM-Newton X-ray observations and new or forthcoming low frequency GMRT data -- RXJ1416.4+2315 (z=0.137). Fossil galaxy groups are ideal laboratories for studying feedback mechanisms and how energy injection affects the IGM, since due to the lack of recent merging activity, we expect the IGM to be relatively pristine and affected only by any AGN activity that has occurred in the group. Our Chandra X-ray observations reveal features resembling AGN-inflated bubbles, whilst our GMRT radio data show evidence of extended emission from the central AGN that may be filling the bubble. This has enabled us to estimate the work done by the central AGN, place limits on the rates of energy injection and discuss the nature of the plasma filling the bubble.

  7. Prospects for AGN Science using the ART-XC on the SRG Mission

    Science.gov (United States)

    Swartz, Douglas A.; Elsner, Ronald F.; Gubarev, Mikhail V.; O'Dell, Stephen L.; Ramsey, Brian D.; Bonamente, Massimiliano

    2012-01-01

    The enhanced hard X-ray sensitivity provided by the Astronomical Roentgen Telescope to the Spectrum Roentgen Gamma mission facilitates the detection of heavily obscured and other hard-spectrum cosmic X-ray sources. The SRG all-sky survey will obtain large, statistically-well-defined samples of active galactic nuclei (AGN) including a significant population of local heavily-obscured AGN. In anticipation of the SRG all-sky survey, we investigate the prospects for refining the bright end of the AGN luminosity function and determination of the local black hole mass function and comparing the spatial distribution of AGN with large-scale structure defined by galaxy clusters and groups. Particular emphasis is placed on studies of the deep survey Ecliptic Pole regions.

  8. The effect of AGN feedback on the X-ray morphologies of clusters -- simulations vs. observations

    CERN Document Server

    Chon, Gayoung; Boehringer, Hans

    2016-01-01

    We study the effect of Active Nuclei Galaxy (AGN) feedback as one of the major mechanisms modifying the cluster morphology influencing scaling relations, which are the most uncertain factor in constraining cosmology with clusters of galaxies. Using cosmological hydrodynamical simulations we investigate how the AGN feedback changes the X-ray morphology of the simulated systems, and compare to the observed REXCESS (Representative XMM-Newton Cluster Structure Survey) clusters. We apply centre shifts and power ratios to characterise the cluster morphology, and find that our simulated clusters are more substructured than the observed ones. We show that the degree of this discrepancy is affected by the inclusion of AGN feedback. While the clusters simulated with the AGN feedback are in much better agreement with the REXCESS L_X-T relation, they are also more substructured, which increases the tension with observations. This suggests that not only global cluster properties such as L_X and T and radial profiles shoul...

  9. Makrohindamine Hollandis. Esimesed kümme aastat : 1991-2001 / Agnes E. M. Jonker

    Index Scriptorium Estoniae

    Jonker, Agnes E. M.

    2003-01-01

    Hollandi Arhiivikooli dotsent Agnes E. M. Jonker makrohindamise meetodist arhiivinduses e. projektist PIVOT (Projekt uue üleandmisperioodi kehtestamiseks), mis on üle maailma üks tuntumaid funktsionaalse hindamise põhimõtte rakendusnäiteid

  10. AGN Obscuration Through Dusty Infrared Dominated Flows. 1; Radiation-Hydrodynamics Solution for the Wind

    Science.gov (United States)

    Dorodnitsyn, A.; Bisnovatyi-Kogan. G. S.; Kallman, T.

    2011-01-01

    We construct a radiation-hydrodynamics model for the obscuring toroidal structure in active galactic nuclei. In this model the obscuration is produced at parsec scale by a dense, dusty wind which is supported by infrared radiation pressure on dust grains. To find the distribution of radiation pressure, we numerically solve the 2D radiation transfer problem in a flux limited diffusion approximation. We iteratively couple the solution with calculations of stationary 1D models for the wind, and obtain the z-component of the velocity. Our results demonstrate that for AGN luminosities greater than 0.1 L(sub edd) external illumination can support a geometrically thick obscuration via outflows driven by infrared radiation pressure. The terminal velocity of marginally Compton-thin models (0.2 AGN torus problem and AGN unification models. Such winds can also provide an important channel for AGN feedback.

  11. AGN 190383, a novel phospholipase inhibitor with topical anti-inflammatory activity.

    Science.gov (United States)

    De Vries, G W; Lee, G; Amdahl, L; Wenzel, M; Garst, M; Wheeler, L A

    1991-09-01

    AGN 190383 is a 5-hydroxy-2(5H)-furanone ring analog of the marine natural product manoalide. When applied topically, AGN 190383 inhibits phorbol ester induced mouse ear edema. It is a potent inhibitor of bee venom phospholipase A2 and blocks the release of arachidonic acid from calcium ionophore A23187 stimulated human neutrophils. AGN 190383 also inhibits both hormone-operated and depolarization-dependent calcium mobilization in GH3 cells, as well as fMLP stimulated increases in free cytosolic calcium in human PMNs. Furthermore, it is also able to block the release of the neutral protease elastase from stimulated neutrophils. The effects of AGN 190383 on arachidonic acid metabolism and leukocyte function may account, in part, for its anti-inflammatory activity in vivo.

  12. A Hubble Space Telescope Survey of Intrinsic Absorption in Nearby AGN

    Science.gov (United States)

    Dashtamirova, Dzhuliya; Dunn, Jay P.; Crenshaw, D. Michael

    2017-01-01

    We present a survey of the intrinsic UV absorption lines in active galactic nuclei (AGN). We limit our study to the ultraviolet spectra of type 1 AGN with a redshift of z COS) observations. We download and co-add all of the COS spectra. We find that about 80 of these are type 1 AGN. We normalize the COS spectra and identify all of the intrinsic Lyman-alpha, N V, Si IV, and C IV intrinsic absorption features. From these data, we determine the fraction of type 1 AGN with intrinsic absorption in this redshift range and find the global covering factors of the absorbers. We also identify low ionization species as well as excited state lines. A number of objects have multiple epoch COS and/or Space Telescope Imaging Spectrograph (STIS) observations, which we use to investigate the absorption variability.

  13. SNTP program reactor design

    Science.gov (United States)

    Walton, Lewis A.; Sapyta, Joseph J.

    1993-06-01

    The Space Nuclear Thermal Propulsion (SNTP) program is evaluating the feasibility of a particle bed reactor for a high-performance nuclear thermal rocket engine. Reactors operating between 500 MW and 2,000 MW will produce engine thrusts ranging from 20,000 pounds to 80,000 pounds. The optimum reactor arrangement depends on the power level desired and the intended application. The key components of the reactor have been developed and are being tested. Flow-to-power matching considerations dominate the thermal-hydraulic design of the reactor. Optimal propellant management during decay heat cooling requires a three-pronged approach. Adequate computational methods exist to perform the neutronics analysis of the reactor core. These methods have been benchmarked to critical experiment data.

  14. Fast Spectrum Reactors

    CERN Document Server

    Todd, Donald; Tsvetkov, Pavel

    2012-01-01

    Fast Spectrum Reactors presents a detailed overview of world-wide technology contributing to the development of fast spectrum reactors. With a unique focus on the capabilities of fast spectrum reactors to address nuclear waste transmutation issues, in addition to the well-known capabilities of breeding new fuel, this volume describes how fast spectrum reactors contribute to the wide application of nuclear power systems to serve the global nuclear renaissance while minimizing nuclear proliferation concerns. Readers will find an introduction to the sustainable development of nuclear energy and the role of fast reactors, in addition to an economic analysis of nuclear reactors. A section devoted to neutronics offers the current trends in nuclear design, such as performance parameters and the optimization of advanced power systems. The latest findings on fuel management, partitioning and transmutation include the physics, efficiency and strategies of transmutation, homogeneous and heterogeneous recycling, in addit...

  15. Hybrid reactors. [Fuel cycle

    Energy Technology Data Exchange (ETDEWEB)

    Moir, R.W.

    1980-09-09

    The rationale for hybrid fusion-fission reactors is the production of fissile fuel for fission reactors. A new class of reactor, the fission-suppressed hybrid promises unusually good safety features as well as the ability to support 25 light-water reactors of the same nuclear power rating, or even more high-conversion-ratio reactors such as the heavy-water type. One 4000-MW nuclear hybrid can produce 7200 kg of /sup 233/U per year. To obtain good economics, injector efficiency times plasma gain (eta/sub i/Q) should be greater than 2, the wall load should be greater than 1 MW.m/sup -2/, and the hybrid should cost less than 6 times the cost of a light-water reactor. Introduction rates for the fission-suppressed hybrid are usually rapid.

  16. Ultra-fast outflows (aka UFOs) in AGNs and their relevance for feedback

    Science.gov (United States)

    Cappi, Massimo; Tombesi, F.; Giustini, M.; Dadina, M.; Braito, V.; Kaastra, J.; Reeves, J.; Chartas, G.; Gaspari, M.; Vignali, C.; Gofford, J.; Lanzuisi, G.

    2012-09-01

    During the last decade, several observational evidences have been accumulated for the existence of massive, high velocity winds/outflows (aka UFOs) in nearby AGNs and, possibly, distant quasars. I will review here such evidences, present some of the latest results in this field, and discuss the relevance of UFOs for both understanding the physics of accretion/ejection flows on supermassive black holes, and for quantifying the amount of AGN feedback.

  17. AGNfitter: A Bayesian MCMC Approach to Fitting Spectral Energy Distributions of AGNs

    Science.gov (United States)

    Calistro Rivera, Gabriela; Lusso, Elisabeta; Hennawi, Joseph F.; Hogg, David W.

    2016-12-01

    We present AGNfitter, a publicly available open-source algorithm implementing a fully Bayesian Markov Chain Monte Carlo method to fit the spectral energy distributions (SEDs) of active galactic nuclei (AGNs) from the sub-millimeter to the UV, allowing one to robustly disentangle the physical processes responsible for their emission. AGNfitter makes use of a large library of theoretical, empirical, and semi-empirical models to characterize both the nuclear and host galaxy emission simultaneously. The model consists of four physical emission components: an accretion disk, a torus of AGN heated dust, stellar populations, and cold dust in star-forming regions. AGNfitter determines the posterior distributions of numerous parameters that govern the physics of AGNs with a fully Bayesian treatment of errors and parameter degeneracies, allowing one to infer integrated luminosities, dust attenuation parameters, stellar masses, and star-formation rates. We tested AGNfitter’s performance on real data by fitting the SEDs of a sample of 714 X-ray selected AGNs from the XMM-COSMOS survey, spectroscopically classified as Type1 (unobscured) and Type2 (obscured) AGNs by their optical-UV emission lines. We find that two independent model parameters, namely the reddening of the accretion disk and the column density of the dusty torus, are good proxies for AGN obscuration, allowing us to develop a strategy for classifying AGNs as Type1 or Type2, based solely on an SED-fitting analysis. Our classification scheme is in excellent agreement with the spectroscopic classification, giving a completeness fraction of ˜ 86 % and ˜ 70 % , and an efficiency of ˜ 80 % and ˜ 77 % , for Type1 and Type2 AGNs, respectively.

  18. The Search for Molecular Outflows in Local Volume AGNs with Herschel-PACS

    Science.gov (United States)

    Stone, M.; Veilleux, S.; Meléndez, M.; Sturm, E.; Graciá-Carpio, J.; González-Alfonso, E.

    2016-08-01

    We present the results from a systematic search for galactic-scale, molecular (OH 119 μm) outflows in a sample of 52 Local Volume (d\\lt 50 Mpc) Burst Alert Telescope detected active galactic nuclei (BAT AGNs) with Herschel-PACS. We combine the results from our analysis of the BAT AGNs with the published Herschel/PACS data of 43 nearby (z\\lt 0.3) galaxy mergers, mostly ultra-luminous infrared galaxies (ULIRGs) and QSOs. The objects in our sample of BAT AGNs have, on average, ˜ 10{--}100 times lower AGN luminosities, star formation rates, and stellar masses than those of the ULIRG and QSO samples. OH 119 μm is detected in 42 of our BAT AGN targets. Evidence for molecular outflows (i.e., OH absorption profiles with median velocities more blueshifted than -50 km s-1 and/or blueshifted wings with 84% velocities less than -300 km s-1) is seen in only four BAT AGNs (NGC 7479 is the most convincing case). Evidence for molecular inflows (i.e., OH absorption profiles with median velocities more redshifted than 50 km s-1) is seen in seven objects, although an inverted P-Cygni profile is detected unambiguously in only one object (Circinus). Our data show that both the starburst and AGN contribute to driving OH outflows, but the fastest OH winds require AGNs with quasar-like luminosities. We also confirm that the total absorption strength of OH 119 μm is a good proxy for dust optical depth as it correlates strongly with the 9.7 μm silicate absorption feature, a measure of obscuration originating in both the nuclear torus and host galaxy disk. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  19. From Nearby Low Luminosity AGN to High Redshift Radio Galaxies: Science Interests with SKA

    CERN Document Server

    Kharb, P; Singh, V; Bagchi, J; Chandra, C H Ishwara; Hota, A; Konar, C; Wadadekar, Y; Shastri, P; Das, M; Baliyan, K; Nath, B B; Pandey-Pommier, M

    2016-01-01

    We present detailed science cases that a large fraction of the Indian AGN community is interested in pursuing with the upcoming Square Kilometre Array (SKA). These interests range from understanding low luminosity active galactic nuclei in the nearby Universe to powerful radio galaxies at high redshifts. Important unresolved science questions in AGN physics are discussed. Ongoing low-frequency surveys with the SKA pathfinder telescope GMRT, are highlighted.

  20. An enhanced fraction of starbursting galaxies among high Eddington ratio AGNs

    Science.gov (United States)

    Bernhard, E.; Mullaney, J. R.; Daddi, E.; Ciesla, L.; Schreiber, C.

    2016-07-01

    We investigate the star-forming properties of 1620 X-ray selected active galactic nuclei (AGN) host galaxies as a function of their specific X-ray luminosity (i.e. X-ray luminosity per unit host stellar mass) - a proxy of the Eddington ratio. Our motivation is to determine whether there is any evidence of a suppression of star formation at high Eddington ratios, which may hint towards `AGN feedback' effects. Star formation rates (SFRs) are derived from fits to Herschel-measured far-infrared spectral energy distributions, taking into account any contamination from the AGN. Herschel-undetected AGNs are included via stacking analyses to provide average SFRs in bins of redshift and specific X-ray luminosity (spanning 0.01 lesssim L_X/M_{ast } lesssim 100 L_{{⊙}} M_{{⊙}}^{-1}). After normalizing for the effects of mass and redshift arising from the evolving galaxy main sequence, we find that the SFRs of high specific luminosity AGNs are slightly enhanced compared to their lower specific luminosity counterparts. This suggests that the SFR distribution of AGN hosts changes with specific X-ray luminosity, a result reinforced by our finding of a significantly higher fraction of starbursting hosts among high specific luminosity AGNs compared to that of the general star-forming galaxy population (i.e. 8-10 per cent versus 3 per cent). Contrary to our original motivation, our findings suggest that high specific luminosity AGNs are more likely to reside in galaxies with enhanced levels of star formation.

  1. From Nearby Low Luminosity AGN to High Redshift Radio Galaxies: Science Interests with Square Kilometre Array

    Indian Academy of Sciences (India)

    P. Kharb; D. V. Lal; V. Singh; J. Bagchi; C. H. Ishwara Chandra; A. Hota; C. Konar; Y. Wadadekar; P. Shastri; M. Das; K. Baliyan; B. B. Nath; M. Pandey-Pommier

    2016-12-01

    We present detailed science cases that a large fraction of the Indian AGN community is interested in pursuing with the upcoming Square Kilometre Array (SKA). These interests range from understanding low luminosity active galactic nuclei in the nearby Universe to powerful radio galaxies at high redshifts. Important unresolved science questions in AGN physics are discussed. Ongoing low-frequency surveys with the SKA pathfinder telescope GMRT, are highlighted.

  2. Low Resolution Spectral Templates For AGNs and Galaxies From 0.03 -- 30 microns

    CERN Document Server

    Assef, R J; Brodwin, M; Cool, R; Forman, W; González, A H; Hickox, R C; Jones, C; Le Floc'h, E; Moustakas, J; Murray, S S; Stern, D

    2009-01-01

    We present a set of low resolution empirical SED templates for AGNs and galaxies in the wavelength range from 0.03 to 30 microns based on the multi-wavelength photometric observations of the NOAO Deep-Wide Field Survey Bootes field and the spectroscopic observations of the AGN and Galaxy Evolution Survey. Our training sample is comprised of 14448 galaxies in the redshift range 0~ 3.4.

  3. Multi purpose research reactor

    Energy Technology Data Exchange (ETDEWEB)

    Raina, V.K. [Research Reactor Design and Projects Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)]. E-mail: vkrain@magnum.barc.ernet.in; Sasidharan, K. [Research Reactor Design and Projects Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Sengupta, Samiran [Research Reactor Design and Projects Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Singh, Tej [Research Reactor Services Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2006-04-15

    At present Dhruva and Cirus reactors provide the majority of research reactor based facilities to cater to the various needs of a vast pool of researchers in the field of material sciences, physics, chemistry, bio sciences, research and development work for nuclear power plants and production of radio isotopes. With a view to further consolidate and expand the scope of research and development in nuclear and allied sciences, a new 20 MWt multi purpose research reactor is being designed. This paper describes some of the design features and safety aspects of this reactor.

  4. INVAP's Research Reactor Designs

    Directory of Open Access Journals (Sweden)

    Eduardo Villarino

    2011-01-01

    Full Text Available INVAP, an Argentine company founded more than three decades ago, is today recognized as one of the leaders within the research reactor industry. INVAP has participated in several projects covering a wide range of facilities, designed in accordance with the requirements of our different clients. For complying with these requirements, INVAP developed special skills and capabilities to deal with different fuel assemblies, different core cooling systems, and different reactor layouts. This paper summarizes the general features and utilization of several INVAP research reactor designs, from subcritical and critical assemblies to high-power reactors.

  5. LMFBR type reactor

    Energy Technology Data Exchange (ETDEWEB)

    Kanbe, Mitsuru

    1997-04-04

    An LMFBR type reactor comprises a plurality of reactor cores in a reactor container. Namely, a plurality of pot containing vessels are disposed in the reactor vessel and a plurality of reactor cores are formed in a state where an integrated-type fuel assembly is each inserted to a pot, and a coolant pipeline is connected to each of the pot containing-vessel to cool the reactor core respectively. When fuels are exchanged, the integrated-type fuel assembly is taken out together with the pot from the reactor vessel in a state where the integrated-type fuel assembly is immersed in the coolants in the pot as it is. Accordingly, coolants are supplied to each of the pot containing-vessel connected with the coolant pipeline and circulate while cooling the integrated-type fuel assembly for every pot. Then, when the fuels are exchanged, the integrated type fuel assembly is taken out to the outside of the reactor together with the pot by taking up the pot from the pot-containing vessel. Then, neutron economy is improved to thereby improve reactor power and the breeding ratio. (N.H.)

  6. Gaseous fuel reactor systems for aerospace applications

    Science.gov (United States)

    Thom, K.; Schwenk, F. C.

    1977-01-01

    Research on the gaseous fuel nuclear rocket concept continues under the programs of the U.S. National Aeronautics and Space Administration (NASA) Office for Aeronautics and Space Technology and now includes work related to power applications in space and on earth. In a cavity reactor test series, initial experiments confirmed the low critical mass determined from reactor physics calculations. Recent work with flowing UF6 fuel indicates stable operation at increased power levels. Preliminary design and experimental verification of test hardware for high-temperature experiments have been accomplished. Research on energy extraction from fissioning gases has resulted in lasers energized by fission fragments. Combined experimental results and studies indicate that gaseous-fuel reactor systems have significant potential for providing nuclear fission power in space and on earth.

  7. AEGIS: The color-magnitude relation for X-ray selected AGN

    CERN Document Server

    Nandra, K; Willmer, C N A; Cooper, M C; Croton, D J; Davis, M; Faber, S M; Koo, D C; Laird, E S; Newman, J A

    2006-01-01

    We discuss the relationship between rest-frame color and optical luminosity for X-ray sources in the range 0.6AGN). While there are a few luminous QSOs, most are relatively weak or obscured AGN whose optical colors should be dominated by host galaxy light. The vast majority of AGN hosts at z~1 are luminous and red, with very few objects fainter than M_{B}=-20.5 or bluer than U-B=0.6. This places the AGN in a distinct region of color-magnitude space, on the ``red sequence'' or at the top of the ``blue cloud'', with many in between these two modes in galaxy color. A key stage in the evolution of massive galaxies is when star formation is quenched, resulting in a migration from the blue cloud to the red sequence. Our results are consistent with scenarios in which AGN either cause or maintain this quenching. The large numbers of red sequence AGN imply that strong, ongoing s...

  8. Evidence for Widespread AGN Activity among Massive Quiescent Galaxies at z ~ 2

    CERN Document Server

    Olsen, Karen Pardos; Toft, Sune; Zirm, Andrew W

    2012-01-01

    We quantify the presence of Active Galactic nuclei (AGN) in a mass-complete (M_* >5e10 M_sun) sample of 123 star-forming and quiescent galaxies at 1.5 3e42 ergs/s). The latter fraction is similar for star-forming and quiescent galaxies, and does not depend on galaxy stellar mass, suggesting that perhaps luminous AGN are triggered by external effects such as mergers. We detect significant mean X-ray signals in stacked images for both the individually non-detected star-forming and quiescent galaxies, with spectra consistent with star formation only and/or a low luminosity AGN in both cases. Comparing star formation rates inferred from the 2-10 keV luminosities to those from rest-frame IR+UV emission, we find evidence for an X-ray excess indicative of low-luminosity AGN. Among the quiescent galaxies, the excess suggests that as many as 70-100% of these contain low- or high-luminosity AGN, while the corresponding fraction is lower among star-forming galaxies (43-65%). The ubiquitous presence of AGN in massive, q...

  9. Differences in Halo-Scale Environments between Type 1 and Type 2 AGNs at Low Redshift

    CERN Document Server

    Jiang, Ning; Mo, Houjun; Dong, Xiaobo; Wang, Tinggui; Zhou, Hongyan

    2016-01-01

    Using samples of AGNs, normal galaxies and groups of galaxies selected from the Sloan Digital Sky Survey (SDSS), we study the environments of type 1 and type 2 AGNs both on small and large scales. Comparisons are made for samples matched in redshift, r-band luminosity, and [OIII] luminosity, and separately for central and satellite galaxies. We find that type 2 AGNs and normal galaxies reside in similar environments. Type 1 and type 2 AGNs have similar clustering properties on large scales, but at scales smaller than 100 kpc, type 2s have 3 times more neighbors than type 1s. These results suggest that type 1 and type 2 AGNs are hosted by halos of similar masses, as is also seen directly from the mass distributions of their host groups. Type 2s have significantly more satellites around them, and the distribution of their satellites is also more centrally concentrated. The host galaxies of both types of AGNs have similar optical properties, but their infrared colors are significantly different. Our results sugg...

  10. A Model for Type 2 Coronal Line Forest (CLiF) AGN

    CERN Document Server

    Glidden, Ana; Elvis, Martin; McDowell, Jonathan

    2016-01-01

    We present a model for the classification of Coronal-Line Forest Active Galactic Nuclei (CLiF AGN). CLiF AGN are of special interest due to their remarkably large number of emission lines, especially forbidden high ionization lines (FHILs). Rose et al. (2015a) suggest that their emission is dominated by reflection from the inner wall of the obscuring region rather than direct emission from the accretion disk. This makes CLiF AGN laboratories to test AGN-torus models. Modeling AGN as an accreting supermassive black hole, surrounded by a cylinder of dust and gas, we show a relationship between viewing angle and the revealed area of the inner wall. From the revealed area, we can determine the amount of FHIL emission at various angles. We calculate the strength of [FeVII]{\\lambda}6087 emission for a number of intermediate angles (30{\\deg}, 40{\\deg}, and 50{\\deg}) and compare the results with the luminosity of the observed emission line from six known CLiF AGN. We find that there is good agreement between our mode...

  11. A Statistical Study of H I Gas in Nearby Narrow-Line AGN-Hosting Galaxies

    CERN Document Server

    Zhu, Yi-Nan

    2015-01-01

    As a quenching mechanism, AGN feedback could suppress on-going star formation in their host galaxies. On the basis of a sample of galaxies selected from ALFALFA HI survey, the dependence of their HI mass M[HI], stellar mass M[*] & HI-to-stellar mass ratio M[HI]/M[*] on various tracers of AGN activity are presented and analyzed in this paper. Almost all the AGN-hostings in this sample are gas-rich galaxies, and there is no any evidence to be shown to indicate that the AGN activity could increase/decrease either M[HI] or M[HI]/M[*]. The cold neutral gas can not be fixed positions accurately just based on available HI data due to the large beam size of ALFALFA survey. In addition, even though AGN-hostings are more easily detected by HI survey compared with absorption line galaxies, these two types of galaxies show similar star formation history. If an AGN-hosting would ultimately evolve into an old red galaxy with few cold gas, then when and how the gas has been exhausted have to be solved by future hypothes...

  12. A statistical study of H i gas in nearby narrow-line AGN-hosting galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Yi-Nan; Wu, Hong, E-mail: zyn@bao.ac.cn, E-mail: hwu@bao.ac.cn [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

    2015-01-01

    As a quenching mechanism, active galactic nucleus (AGN) feedback could suppress on going star formation in host galaxies. On the basis of a sample of galaxies selected from the Arecibo Legacy Fast ALFA (ALFALFA) H i survey, the dependence of the H i mass (M{sub H} {sub i}), stellar mass (M{sub *}), and H i-to-stellar mass ratio (M{sub H} {sub i}/M{sub *}) on various tracers of AGN activity are presented and analyzed in this paper. Almost all the AGN hostings in this sample are gas-rich galaxies, and there is not any evidence to indicate that the AGN activity could increase or decrease either M{sub H} {sub i} or M{sub H} {sub i}/M{sub *}. The position of the cold neutral gas cannot be fixed accurately based only on available H i data, due to the large beam size of ALFALFA survey. In addition, even though AGN hostings are more easily detected by an H i survey compared with absorption line galaxies, these two types of galaxies show similar star formation history. If an AGN hosting would ultimately evolve into an old red galaxy with low cold gas, then when and how the gas has been exhausted must be solved by future hypotheses and observations.

  13. Luminosity and Redshift Dependence of the Covering Factor of AGNs viewed with WISE and SDSS

    CERN Document Server

    Toba, Yoshiki; Matsuhara, Hideo; Malkan, Matthew A; Gandhi, Poshak; Nakagawa, Takao; Isobe, Naoki; Shirahata, Mai; Oi, Nagisa; Ohyama, Youichi; Takita, Satoshi; Yamauchi, Chisato; Yano, Kenichi

    2014-01-01

    In this work, we investigate the dependence of the covering factor (CF) of active galactic nuclei (AGNs) (i) on the mid-infrared (MIR) luminosity and (ii) on the redshift. We constructed 12- and 22-micron luminosity functions (LFs) at 0.006 < z < 0.3 using the Wide-field Infrared Survey Explorer} (WISE) data. Combining the WISE catalog with the Sloan Digital Sky Survey (SDSS) spectroscopic data, we selected 223,982 galaxies at 12 micron and 25,721 galaxies at 22 micron for spectroscopic classification. We then identified 16,355 AGNs at 12 micron and 4,683 AGNs at 22 micron by their optical emission lines and cataloged classifications in the SDSS. Following that, we estimated the CF as the fraction of type 2 AGN in all AGNs whose MIR emissions are dominated by the active nucleus (not their host galaxies) based on their MIR colors. We found that (i) the CF decreased with increasing MIR luminosity, regardless of the choice of type 2 AGN classification criteria, and (ii) the CF did not change significantly ...

  14. The INTEGRAL/IBIS AGN catalogue I: X-ray absorption properties versus optical classification

    CERN Document Server

    Malizia, A; Bazzano, A; Bird, A J; Masetti, N; Panessa, F; Stephen, J B; Ubertini, P

    2012-01-01

    In this work we present the most comprehensive INTEGRAL AGN sample which lists 272 objects. Here we mainly use this sample to study the absorption properties of active galaxies, to probe new AGN classes and to test the AGN unification scheme. We find that half (48%) of the sample is absorbed while the fraction of Compton thick AGN is small (~7%). In line with our previous analysis, we have however shown that when the bias towards heavily absorbed objects which are lost if weak and at large distance is removed, as it is possible in the local Universe, the above fractions increase to become 80% and 17%. We also find that absorption is a function of source luminosity, which implies some evolution in the obscuration properties of AGN. Few peculiar classes, so far poorly studied in the hard X-ray band, have been detected and studied for the first time such as 5 XBONG, 5 type 2 QSOs and 11 LINERs. In terms of optical classification, our sample contains 57% of type 1 and 43% of type 2 AGN; this subdivision is simila...

  15. Obscured flat spectrum radio AGN as sources of high-energy neutrinos

    CERN Document Server

    Maggi, G; Correa, P; de Vries, K D; Gentile, G; Tavares, J Leon; Scholten, O; van Eijndhoven, N; Vereecken, M; Winchen, T

    2016-01-01

    Active Galactic Nuclei (AGN) are believed to be one of the main source candidates for the high-energy (TeV-PeV) cosmic neutrino flux recently discovered by the IceCube neutrino observatory. Nevertheless, several correlation studies between AGN and the cosmic neutrinos detected by IceCube show no significance. Therefore, in this article we consider a specific sub-class of AGN for which an increased neutrino production is expected. This sub-class contains AGN for which their high-energy jet is pointing toward Earth. Furthermore, we impose the condition that the jet is obscured by gas or dust surrounding the AGN. A method is presented to determine the total column density of the obscuring medium, which is probed by determining the relative X-ray attenuation with respect to the radio flux as obtained from the AGN spectrum. The total column density allows us to probe the interaction of the jet with the surrounding matter which leads to additional neutrino production. Finally, starting from two different source cat...

  16. On the Anomalous Silicate Emission Features of AGNs: A Possible Interpretation Based on Porous Dust

    CERN Document Server

    Li, M P; Li, Aigen

    2008-01-01

    The recent Spitzer detections of the 9.7 micron Si--O silicate emission in type 1 AGNs provide support for the AGN unification scheme. The properties of the silicate dust are of key importance to understanding the physical, chemical and evolutionary properties of the obscuring dusty torus around AGNs. Compared to that of the Galactic interstellar medium (ISM), the 10 micron silicate emission profile of type 1 AGNs is broadened and has a clear shift of peak position to longer wavelengths. In literature this is generally interpreted as an indication of the deviations of the silicate composition, size, and degree of crystallization of AGNs from that of the Galactic ISM. In this Letter we show that the observed peak shift and profile broadening of the 9.7 micron silicate emission feature can be explained in terms of porous composite dust consisting of ordinary interstellar amorphous silicate, amorphous carbon and vacuum. Porous dust is naturally expected in the dense circumnuclear region around AGNs, as a consequ...

  17. Observational constraints on the physics behind the evolution of AGN since z ~ 1

    CERN Document Server

    Georgakakis, A; Willmer, C N A; Nandra, K; Kocevski, D D; Cooper, M C; Rosario, D J; Koo, D C; Trump, J R; Juneau, S

    2011-01-01

    We explore the evolution with redshift of the rest-frame colours and space densities of AGN hosts (relative to normal galaxies) to shed light on the dominant mechanism that triggers accretion onto supermassive black holes as a function of cosmic time. Data from serendipitous wide-area XMM surveys of the SDSS footprint (XMM/SDSS, Needles in the Haystack survey) are combined with Chandra deep observations in the AEGIS, GOODS-North and GOODS-South to compile uniformly selected samples of moderate luminosity X-ray AGN [L_X(2-10keV) = 1e41-1e44erg/s] at redshifts 0.1, 0.3 and 0.8. It is found that the fraction of AGN hosted by red versus blue galaxies does not change with redshift. Also, the X-ray luminosity density associated with either red or blue AGN hosts remains nearly constant since z=0.8. X-ray AGN represent a roughly fixed fraction of the space density of galaxies of given optical luminosity at all redshifts probed by our samples. In contrast the fraction of X-ray AGN among galaxies of a given stellar mas...

  18. Multi-wavelength properties and SMBH's masses of the isolated AGNs in the Local Universe

    Science.gov (United States)

    Vavilova, I. B.; Vasylenko, A. A.; Babyk, Iu. V.; Pulatova, N. G.

    2016-08-01

    The sample of 36 nearest isolated AGNs was cross-matched by 2MIG and Veron-Cetty catalogues and limited to Ks ≤ 12.0m and Vr databases obtained with ground-based and space observatories (from radio to X-ray ranges). It is allowed us to separate the internal evolution mechanisms from the environment influence and consider them as two separate processes related to fueling nuclear activity and accretion on the SMBHs outside of the environment. In this report we present briefly main results, which were already published (Pulatova N., Vavilova I., Sawangwit U. et al. The 2MIG isolated AGNs - I. General and multiwavelength properties of AGNs and host galaxies in the northern sky, MNRAS, 447, Issue 3, p. 2209-2223 (2015)). We accentuate that for the first time we revealed that the host isolated galaxies with AGNs of Sy1 type (without faint companions) appear to possess the bar morphological features (e.g., the interaction with neighboring galaxies is not necessary condition for broad-line region formation). We give also current results as concerns with more detail X-ray analysis, emission features and spectral models for several AGNs for which a cumulative soft and hard energy spectrum was reconstructed. The estimates of SMBH masses show that are systematically lower than the SMBH masses of AGNs located in a dense environment.

  19. Higher prevalence of X-ray selected AGN in intermediate age galaxies up to z~1

    CERN Document Server

    Hernán-Caballero, Antonio; Pérez-González, Pablo G; Barro, Guillermo; Aird, James; Ferreras, Ignacio; Cava, Antonio; Cardiel, Nicolás; Esquej, Pilar; Gallego, Jesús; Nandra, Kirpal; Rodríguez-Zaurín, Javier

    2014-01-01

    We analyse the stellar populations in the host galaxies of 53 X-ray selected optically dull active galactic nuclei (AGN) at 0.3410^10.5 M_sun) and that the observed fraction of galaxies hosting an AGN increases with the stellar mass. A careful selection of random control samples of inactive galaxies allows us to remove the stellar mass and redshift dependencies of the AGN fraction to explore trends with several stellar age indicators. We find no significant differences in the distribution of the rest-frame U-V colour for AGN hosts and inactive galaxies, in agreement with previous results. However, we find significantly shallower 4000 AA breaks in AGN hosts, indicative of younger stellar populations. With the help of a model-independent determination of the extinction, we obtain extinction-corrected U-V colours and light-weighted average stellar ages. We find that AGN hosts have younger stellar populations and higher extinction compared to inactive galaxies with the same stellar mass and at the same redshift. ...

  20. The Detection of Fermi AGN above 100 GeV using Clustering Analysis

    CERN Document Server

    Armstrong, Thomas; Chadwick, Paula M; Nolan, S J

    2015-01-01

    The density-based clustering algorithm DBSCAN has been applied to the Fermi Large Area Telescope (LAT) dataset of $ E_{\\gamma} \\geqslant 100$~GeV events with $\\lvert b\\rvert>10^{\\circ}$, in order to search for new very high energy (VHE) $\\gamma$-ray sources. The clustering analysis returned 49 clusters, of which 21 correspond to already known VHE-emitting active galactic nuclei (AGN) within the TeVCat catalogue and a further 11 were found to be significant in a full Fermi analysis. Of these, 2 are previously detected Fermi VHE AGN, and 9 represent new VHE sources consisting of 6 BL Lac objects, one blazar of unknown type and 2 unassociated sources. Comparing these, along with the VHE AGN RBS 0679 and RBS 0970 previously detected with Fermi-LAT, to the current populations of AGN detected with ground-based instruments and Fermi suggests that the VHE-emitting AGN discovered in this study are very similar to the TeVCat AGN and therefore further observations with ground-based imaging atmospheric Cherenkov telescop...

  1. AGN host galaxies at redshift z~0.7: peculiar or not?

    CERN Document Server

    Boehm, Asmus; Bell, Eric F; Jahnke, Knud; Wolf, Christian; Bacon, David; Barden, Marco; Gray, Meghan E; Hoeppe, Goetz; Jogee, Sharda; McIntosh, Dan H; Peng, Chien Y; Robaina, Adai R; Balogh, Michael; Barazza, Fabio D; Caldwell, John A R; Heymans, Catherine; Haeussler, Boris; van Kampen, Eelco; Lane, Kyle; Meisenheimer, Klaus; Sanchez, Sebastian F; Taylor, Andy N; Zheng, Xianzhong

    2012-01-01

    We perform a quantitative morphological comparison between the hosts of Active Galactic Nuclei (AGN) and quiescent galaxies at intermediate redshifts (z~0.7). The imaging data are taken from the large HST/ACS mosaics of the GEMS and STAGES surveys. Our main aim is to test whether nuclear activity at this cosmic epoch is triggered by major mergers. Using images of quiescent galaxies and stars, we create synthetic AGN images to investigate the impact of an optical nucleus on the morphological analysis of AGN hosts. Galaxy morphologies are parameterized using the asymmetry index A, concentration index C, Gini coefficient G and M20 index. A sample of ~200 synthetic AGN is matched to 21 real AGN in terms of redshift, host brightness and host-to-nucleus ratio to ensure a reliable comparison between active and quiescent galaxies. The optical nuclei strongly affect the morphological parameters of the underlying host galaxy. Taking these effects into account, we find that the morphologies of the AGN hosts are clearly ...

  2. Star formation in AGNs at the hundred parsec scale using MIR high-resolution images

    Science.gov (United States)

    Ruschel-Dutra, Daniel; Rodríguez Espinosa, José Miguel; González Martín, Omaira; Pastoriza, Miriani; Riffel, Rogério

    2017-04-01

    It has been well established in the past decades that the central black hole masses of galaxies correlate with dynamical properties of their harbouring bulges. This notion begs the question of whether there are causal connections between the active galactic nucleus (AGN) and its immediate vicinity in the host galaxy. In this paper, we analyse the presence of circumnuclear star formation in a sample of 15 AGN using mid-infrared observations. The data consist of a set of 11.3 μm polycyclic aromatic hydrocarbon emission and reference continuum images, taken with ground-based telescopes, with sub-arcsecond resolution. By comparing our star formation estimates with AGN accretion rates, derived from X-ray luminosities, we investigate the validity of theoretical predictions for the AGN-starburst connection. Our main results are: (i) circumnuclear star formation is found, at distances as low as tens of parsecs from the nucleus, in nearly half of our sample (7/15); (ii) star formation luminosities are correlated with the bolometric luminosity of the AGN (LAGN) only for objects with LAGN ≥ 1042 erg s-1; (iii) low-luminosity AGNs (LAGN < 1042 erg s-1) seem to have starburst luminosities far greater than their bolometric luminosities.

  3. Search for Molecular Outflows in Local Volume AGN with Herschel-PACS

    CERN Document Server

    Stone, M; Melendez, M; Sturm, E; Gracia-Carpio, J; Gonzalez-Alfonso, E

    2016-01-01

    We present the results from a systematic search for galactic-scale, molecular (OH 119 $\\mu$m) outflows in a sample of 52 Local Volume ($d < 50$ Mpc) Burst Alert Telescope detected active galactic nuclei (BAT AGN) with \\emph{Herschel}-PACS. We combine the results from our analysis of the BAT AGN with the published \\emph{Herschel}/PACS data of 43 nearby ($z<0.3$) galaxy mergers, mostly ultraluminous infrared galaxies (ULIRGs) and QSOs. The objects in our sample of BAT AGN have, on average, $\\sim 10-100$ times lower AGN luminosities, star formation rates (SFRs), and stellar masses than those of the ULIRG and QSO sample. OH 119 $\\mu$m is detected in 42 of our BAT AGN targets. Evidence for molecular outflows (i.e. OH absorption profiles with median velocities more blueshifted than $-$50 km s$^{-1}$ and/or blueshifted wings with 84-percentile velocities less than $-$300 km s$^{-1}$) is seen in only four BAT AGN (NGC~7479 is the most convincing case). Evidence for molecular inflows (i.e. OH absorption profiles...

  4. Searching for highly obscured AGN in the XMM-Newton serendipitous source catalog

    CERN Document Server

    Corral, A; Watson, M G; Rosen, S R; Koulouridis, E; Page, K L; Ranalli, P; Lanzuisi, G; Mountrichas, G; Akylas, A; Stewart, G C; Pye, J P

    2014-01-01

    The majority of active galactic nuclei (AGN) are obscured by large amounts of absorbing material that makes them invisible at many wavelengths. X-rays, given their penetrating power, provide the most secure way for finding these AGN. The XMM-Newton serendipitous source catalog is the largest catalog of X-ray sources ever produced; it contains about half a million detections. These sources are mostly AGN. We have derived X-ray spectral fits for very many 3XMM-DR4 sources ($\\gtrsim$ 114 000 observations, corresponding to $\\sim$ 77 000 unique sources), which contain more than 50 source photons per detector. Here, we use a subsample of $\\simeq$ 1000 AGN in the footprint of the SDSS area (covering 120 deg$^2$) with available spectroscopic redshifts. We searched for highly obscured AGN by applying an automated selection technique based on X-ray spectral analysis that is capable of efficiently selecting AGN. The selection is based on the presence of either a) flat rest-frame spectra; b) flat observed spectra; c) an ...

  5. The physical properties of AGN host galaxies as a probe of SMBH feeding mechanisms

    CERN Document Server

    Gatti, M; Menci, N; Bongiorno, A; Fiore, F

    2014-01-01

    Using a state-of-the-art semi analytic model (SAM) for galaxy formation, we have investigated the statistical effects of assuming two different mechanisms for triggering AGN activity on the properties of AGN host galaxies. We have considered a first accretion mode where AGN activity is triggered by disk instabilities (DI) in isolated galaxies, and a second feeding mode where such an activity is triggered by galaxy mergers and fly-by events (interactions, IT). We obtained the following results:i) for hosts with $M_* \\lesssim 10^{11} M_{\\bigodot}$, both DI and IT modes are able to account for the observed AGN hosts stellar mass function; for more massive hosts, the DI scenario predicts a lower space density than the IT model, lying below the observational estimates for z>0.8.ii) The analysis of the color-magnitude diagram (CMD) of AGN hosts for redshift z < 1.5 can provide a good observational test to effectively discriminate between the DI and IT mode, since DIs are expected to yield AGN host galaxy colors ...

  6. On the selection of AGN neutrino source candidates for a source stacking analysis with neutrino telescopes

    CERN Document Server

    Achterberg, A; Adams, J; Ahrens, J; Atlee, D W; Bahcall, J N; Bai, X; Baret, B; Bartelt, M; Barwick, S W; Bay, R; Beattie, K; Becka, T; Becker, J K; Becker, K H; Berghaus, P; Berley, D; Bernardini, E; Bertrand, D; Besson, D Z; Blaufuss, E; Boersma, D J; Bohm, C; Boser, S; Botner, O; Bouchta, A; Braun, J; Burgess, C; Burgess, T; Castermans, T; Chirkin, D; Clem, J; Collin, B; Conrad, J; Cooley, J; Cowen, D F; D'Agostino, M V; Davour, A; Day, C T; De Clercq, C; Desiati, P; De Young, T; Dreyer, J; Duvoort, M R; Edwards, W R; Ehrlich, R; Ellsworth, R W; Evenson, P A; Fazely, A R; Feser, T; Filimonov, K; Gaisser, T K; Gallagher, J; Ganugapati, R; Geenen, H; Gerhardt, L; Goldschmidt, A; Goodman, J A; Greene, M G; Grullon, S; Gross, A; Gunasingha, R M; Hallgren, A; Halzen, F; Han, K; Hanson, K; Hardtke, D; Hardtke, R; Harenberg, T; Hart, J E; Hauschildt, T; Hays, D; Heise, J; Helbing, K; Hellwig, M; Herquet, P; Hill, G C; Hodges, J; Hoffman, K D; Hoshina, K; Hubert, D; Hughey, B; Hulth, P O; Hultqvist, K; Hundertmark, S; Ishihara, A; Jacobsen, J; Japaridze, G S; Jones, A; Joseph, J M; Kampert, K H; Karle, A; Kawai, H; Kelley, J L; Kestel, M; Kitamura, N; Klein, S R; Klepser, S; Kohnen, G; Kolanoski, H; Köpke, L; Krasberg, M; Kühn, K; Landsman, H; Lang, R; Leich, H; Leuthold, M; Liubarsky, I; Lundberg, J; Madsen, J; Mase, K; Matis, H S; McCauley, T; McParland, C P; Meli, A; Messarius, T; Mészáros, P; Minor, R H; Miocinovic, P; Miyamoto, H; Mokhtarani, A; Montaruli, T; Morey, A; Morse, R; Movit, S M; Munich, K; Nahnhauer, R; Nam, J W; Niessen, P; Nygren, D R; Ogelman, H; Olbrechts, P; Olivas, A; Patton, S; Peña-Garay, C; Pérez de los Heros, C; Pieloth, D; Pohl, A C; Porrata, R; Pretz, J; Price, P B; Przybylski, G T; Rawlins, K; Razzaque, S; Reinghaus, F; Resconi, E; Rhode, W; Ribordy, M; Richter, S; Rizzo, A; Robbins, S; Rott, C; Rutledge, D; Sander, H G; Schlenstedt, S; Schneider, D; Seckel, D; Seo, S H; Seunarine, S; Silvestri, A; Smith, A J; Solarz, M; Song, C; Sopher, J E; Spiczak, G M; Spiering, C; Stamatikos, M; Stanev, T; Steffen, P; Steele, D; Stezelberger, T; Stokstad, R G; Stoufer, M C; Stoyanov, S; Sulanke, K H; Sullivan, G W; Sumner, T J; Taboada, I; Tarasova, O; Tepe, A; Thollander, L; Tilav, S; Toale, P A; Turcan, D; van Eijndhoven, N; Vandenbroucke, J; Voigt, B; Wagner, W; Walck, C; Waldmann, H; Walter, M; Wang, Y R; Wendt, C; Wiebusch, C; Wikström, G; Williams, D R; Wischnewski, R; Wissing, H; Woschnagg, K; Xu, X W; Yodh, G; Yoshida, S; De Dios-Zornoza-Gomez, Juan; Biermann, P L

    2006-01-01

    The sensitivity of a search for sources of TeV neutrinos can be improved by grouping potential sources together into generic classes in a procedure that is known as source stacking. In this paper, we define catalogs of Active Galactic Nuclei (AGN) and use them to perform a source stacking analysis. The grouping of AGN into classes is done in two steps: first, AGN classes are defined, then, sources to be stacked are selected assuming that a potential neutrino flux is linearly correlated with the photon luminosity in a certain energy band (radio, IR, optical, keV, GeV, TeV). Lacking any secure detailed knowledge on neutrino production in AGN, this correlation is motivated by hadronic AGN models, as briefly reviewed in this paper. The source stacking search for neutrinos from generic AGN classes is illustrated using the data collected by the AMANDA-II high energy neutrino detector during the year 2000. No significant excess for any of the suggested groups was found.

  7. Constraining the UV emissivity of AGN throughout cosmic time via X-ray surveys

    Science.gov (United States)

    Ricci, Federica; Marchesi, Stefano; Shankar, Francesco; La Franca, Fabio; Civano, Francesca

    2017-02-01

    The cosmological process of hydrogen (H I) reionization in the intergalactic medium is thought to be driven by UV photons emitted by star-forming galaxies and ionizing active galactic nuclei (AGN). The contribution of quasars (QSOs) to H I reionization at z > 4 has been traditionally believed to be quite modest. However, this view has been recently challenged by new estimates of a higher faint-end UV luminosity function (LF). To set firmer constraints on the emissivity of AGN at z < 6, we here make use of complete X-ray-selected samples including deep Chandra and new Cosmic Evolution Survey data, capable to efficiently measure the 1 Ryd comoving AGN emissivity up to z ˜ 5-6 and down to 5 mag fainter than probed by current optical surveys, without any luminosity extrapolation. We find good agreement between the logNH ≲ 21-22 cm-2 X-ray LF and the optically selected QSO LF at all redshifts for M1450 ≤ -23. The full range of the logNH ≲ 21-22 cm-2 LF (M1450 ≤ -17) was then used to quantify the contribution of AGN to the critical value of photon budget needed to keep the Universe ionized. We find that the contribution of ionizing AGN at z = 6 is as small as 1-7 per cent, and very unlikely to be greater than 30 per cent, thus excluding an AGN-dominated reionization scenario.

  8. The ensemble optical variability of type-1 AGN in the Sloan Digital Sky Survey Data Release 7

    CERN Document Server

    Gallastegui-Aizpun, Unai

    2014-01-01

    We use a sample of over 5000 active galactic nuclei (AGN) with extended morphologies at z<0.8 from the Sloan Digital Sky Survey (SDSS) to study the ensemble optical variability as a function of rest-frame time lag and AGN luminosity with the aim of investigating these parameter relationships at lower luminosities than previously studied. We compare photometry from imaging data with spectrophotometry obtained weeks to years later in the Sloan g, r, and i bands. We employ quasar and galaxy eigenspectra fitting to separate the AGN and host galaxy components. A strong correlation between the variability amplitude and rest-frame time lag is observed, in agreement with quasar structure functions but extending to AGN several magnitudes fainter than previously studied. The structure function slopes for our fainter AGN sample are slightly shallower than those found in quasars studies. An anticorrelation with luminosity is clearly detected, with lower luminosity AGN displaying greater variability amplitudes. We demo...

  9. Where the active galaxies live: a panchromatic view of radio-AGN in the AKARI-NEP field

    CERN Document Server

    Karouzos, Marios; Trichas, Markos

    2013-01-01

    We study the host galaxy properties of radio sources in the AKARI-North Ecliptic Pole (NEP) field, using an ensemble of multi-wavelength datasets. We identify both radio-loud and radio-quiet AGN and study their host galaxy properties by means of SED fitting. We investigate the relative importance of nuclear and star-formation activity in radio-AGN and assess the role of radio-AGN as efficient quenchers of star-formation in their host galaxies.

  10. EDDINGTON RATIO DISTRIBUTION OF X-RAY-SELECTED BROAD-LINE AGNs AT 1.0 < z < 2.2

    Energy Technology Data Exchange (ETDEWEB)

    Suh, Hyewon; Hasinger, Günther [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Steinhardt, Charles [California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Silverman, John D.; Schramm, Malte [Kavli Institute for the Physics and Mathematics of the Universe, Todai Institutes for Advanced Study, the University of Tokyo, Kashiwa, 277-8583 (Kavli IPMU, WPI) (Japan)

    2015-12-20

    We investigate the Eddington ratio distribution of X-ray-selected broad-line active galactic nuclei (AGNs) in the redshift range 1.0 < z < 2.2, where the number density of AGNs peaks. Combining the optical and Subaru/Fiber Multi Object Spectrograph near-infrared spectroscopy, we estimate black hole masses for broad-line AGNs in the Chandra Deep Field South (CDF-S), Extended Chandra Deep Field South (E-CDF-S), and the XMM-Newton Lockman Hole (XMM-LH) surveys. AGNs with similar black hole masses show a broad range of AGN bolometric luminosities, which are calculated from X-ray luminosities, indicating that the accretion rate of black holes is widely distributed. We find a substantial fraction of massive black holes accreting significantly below the Eddington limit at z ≲ 2, in contrast to what is generally found for luminous AGNs at high redshift. Our analysis of observational selection biases indicates that the “AGN cosmic downsizing” phenomenon can be simply explained by the strong evolution of the comoving number density at the bright end of the AGN luminosity function, together with the corresponding selection effects. However, one might need to consider a correlation between the AGN luminosity and the accretion rate of black holes, in which luminous AGNs have higher Eddington ratios than low-luminosity AGNs, in order to understand the relatively small fraction of low-luminosity AGNs with high accretion rates in this epoch. Therefore, the observed downsizing trend could be interpreted as massive black holes with low accretion rates, which are relatively fainter than less-massive black holes with efficient accretion.

  11. Optical Variability Properties of High Luminosity AGN Classes

    Indian Academy of Sciences (India)

    C. S. Stalin; Gopal-Krishna; Ram Sagar; Paul J. Wiita

    2004-03-01

    We present the results of a comparative study of the intra-night optical variability (INOV) characteristics of radio-loud and radio-quiet quasars, which involves a systematic intra-night optical monitoring of seven sets of high luminosity AGNs covering the redshift range ≃ 0.2 to ≃ 2.2. The sample, matched in the optical luminosity – redshift (-) plane, consists of seven radio-quiet quasars (RQQs), eight radio lobe-dominated quasars (LDQs), five radio core-dominated quasars (CDQs) and six BL Lac objects (BLs). Systematic CCD observations, aided by a careful data analysis procedure, have allowed us to detect INOV with amplitudes as low as about 1%. Present observations cover a total of 113 nights (720 hours) with only a single qusar monitored as continuously as possible on a given night. Considering the cases of only unambiguous detections of INOV we have estimated duty cycles (DCs) of 17%, 12%, 20% and 61% for RQQs, LDQs, CDQs, and BLs, respectively. The much lower amplitude and DC of INOV shown by RQQs compared to BLs may be understood in terms of their having optical synchrotron jets which are modestly misdirected from us. From our fairly extensive dataset, no general trend of a correlation between the INOVamplitude and the apparent optical brightness of the quasar is noticed. This suggests that the physical mechanisms of INOV and long term optical variability (LTOV) do not have a one-to-one relationship and different factors are involved. Also, the absence of a clear negative correlation between the INOV and LTOV characteristics of blazars of our sample points toward an inconspicuous contribution of accretion disk fluctuations to the observed INOV. The INOV duty cycle of the AGNs observed in this program suggests that INOV is associated predominantly with the highly polarized optical emission components. We also report new VLA imaging of two RQQs (1029 + 329 & 1252 + 020) in our sample which has yielded a 5 GHz detection in one of them (1252 + 020; 5GHz

  12. Investigating AGN Variability Using Combined Multi-Quarter Kepler Data

    Science.gov (United States)

    Revalski, Mitchell; Nowak, D.; Wiita, P. J.; Wehrle, A. E.; Unwin, S. C.

    2014-01-01

    The study of long and short term variability in active galactic nuclei (AGN) yields deeper insight into the physical nature of their emissions from the accretion disk around, and relativistic jets powered by, a galaxy’s central super-massive black hole. We have now obtained a total of eleven quarters of Kepler data on four radio-loud AGN. Our prior work involved calculating power spectral densities (PSDs) on these data both with and without corrections for various instrumental artifacts. We now focus on combining these data sets into one continuous set for each object which spans approximately 2.5 years at a 30 minute sampling rate with >98% duty cycle. The process of stringing together these data is complicated by the quarterly rolls the Kepler space satellite telescope conducts, which causes each target to fall on a different CCD four times per year. We attempt to overcome this problem with a scaling procedure that maintains the original percentage of variations and scales all eleven quarters to the overall average. We calculate PSDs on these stitched light curves both with and without various end-matching techniques applied to increase the accuracy of the PSDs. The PSDs computed for the stitched light curves allow us to probe a full decade lower in frequency than our previous work and show comparable slopes to the PSDs calculated for individual quarters, suggesting we are linking the quarters appropriately. Our average PSD slopes are consistent with ground based observations of other quasars, falling approximately between -1.6 and -1.9. In addition, we have used original codes to bin and average individual PSDs to reduce the bias introduced on the slope fitting process induced by the uneven population of points in the PSDs. This allows for a more accurate power law fitting and tends to steepen the overall slope by approximately 0.1 in the majority of cases. We note increased flaring in one of our objects on the order of 15%, with our remaining three objects

  13. Light water reactor program

    Energy Technology Data Exchange (ETDEWEB)

    Franks, S.M.

    1994-12-31

    The US Department of Energy`s Light Water Reactor Program is outlined. The scope of the program consists of: design certification of evolutionary plants; design, development, and design certification of simplified passive plants; first-of-a-kind engineering to achieve commercial standardization; plant lifetime improvement; and advanced reactor severe accident program. These program activities of the Office of Nuclear Energy are discussed.

  14. Space Nuclear Reactor Engineering

    Energy Technology Data Exchange (ETDEWEB)

    Poston, David Irvin [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-03-06

    We needed to find a space reactor concept that could be attractive to NASA for flight and proven with a rapid turnaround, low-cost nuclear test. Heat-pipe-cooled reactors coupled to Stirling engines long identified as the easiest path to near-term, low-cost concept.

  15. Reactor Materials Research

    Energy Technology Data Exchange (ETDEWEB)

    Van Walle, E

    2001-04-01

    The activities of the Reactor Materials Research Department of the Belgian Nuclear Research Centre SCK-CEN in 2000 are summarised. The programmes within the department are focussed on studies concerning (1) fusion, in particular mechanical testing; (2) Irradiation Assisted Stress Corrosion Cracking (IASCC); (3) nuclear fuel; and (4) Reactor Pressure Vessel Steel (RPVS)

  16. Nuclear reactor design

    CERN Document Server

    2014-01-01

    This book focuses on core design and methods for design and analysis. It is based on advances made in nuclear power utilization and computational methods over the past 40 years, covering core design of boiling water reactors and pressurized water reactors, as well as fast reactors and high-temperature gas-cooled reactors. The objectives of this book are to help graduate and advanced undergraduate students to understand core design and analysis, and to serve as a background reference for engineers actively working in light water reactors. Methodologies for core design and analysis, together with physical descriptions, are emphasized. The book also covers coupled thermal hydraulic core calculations, plant dynamics, and safety analysis, allowing readers to understand core design in relation to plant control and safety.

  17. Status of French reactors

    Energy Technology Data Exchange (ETDEWEB)

    Ballagny, A. [Commissariat a l`Energie Atomique, Saclay (France)

    1997-08-01

    The status of French reactors is reviewed. The ORPHEE and RHF reactors can not be operated with a LEU fuel which would be limited to 4.8 g U/cm{sup 3}. The OSIRIS reactor has already been converted to LEU. It will use U{sub 3}Si{sub 2} as soon as its present stock of UO{sub 2} fuel is used up, at the end of 1994. The decision to close down the SILOE reactor in the near future is not propitious for the start of a conversion process. The REX 2000 reactor, which is expected to be commissioned in 2005, will use LEU (except if the fast neutrons core option is selected). Concerning the end of the HEU fuel cycle, the best option is reprocessing followed by conversion of the reprocessed uranium to LEU.

  18. 活动星系核VLBI观测的新进展%Progress in the VLBI observation of AGNs

    Institute of Scientific and Technical Information of China (English)

    蒋栋荣

    2003-01-01

    This paper reports some recent progresses in the VLBI observation of the AGNs,specially those in the investigations about the central structure of the AGNs and the low luminosity AGNs.The main goal is to show the importance of the VLBI observations in this field.%介绍了活动星系核(AGN)的VLBI观测的新近展,特别关注其中心结构和低光度的活动星系核.主要目的是强调VLBI观测在该领域的重要性.

  19. DCP Series

    Directory of Open Access Journals (Sweden)

    Philip Stearns

    2011-06-01

    Full Text Available Photo essay. A collection of Images produced by intentionally corrupting the circuitry of a Kodak DC280 2 MP digitalcamera. By rewiring the electronics of a digital camera, glitched images are produced in a manner that parallels chemically processing unexposed film or photographic paper to produce photographic images without exposure to light. The DCP Series of Digital Images are direct visualizations of data generated by a digital camera as it takes a picture. Electronic processes associated with the normal operations of the camera, which are usually taken for granted, are revealed through an act of intervention. The camera is turned inside­out through complexes of short­circuits, selected by the artist, transforming the camera from a picture taking device to a data capturing device that renders raw data (electronic signals as images. In essence, these images are snap­shots of electronic signals dancing through the camera's circuits, manually rerouted, written directly to the on­board memory device. Rather than seeing images of the world through a lens, we catch a glimpse of what the camera sees when it is forced to peer inside its own mind.

  20. Study and Analysis on Naphtha Catalytic Reforming Reactor Simulation

    Institute of Scientific and Technical Information of China (English)

    Liang Ke min; Song Yongji; Pan Shiwei

    2004-01-01

    A naphtha catalytic reforming unit with four reactors connected in series is analyzed. A physical model is proposed to describe the catalytic reforming radial flow reactor. Kinetics and thermodynamics equations are selected to describe the naphtha catalytic reforming reaction characteristics based on idealizing the complex naphtha mixture to represent the paraffin, naphthene, and aromatic groups with individual compounds. The simulation results based on above models agree very well with actual operating data of process unit.

  1. A study on naphtha catalytic reforming reactor simulation and analysis

    Institute of Scientific and Technical Information of China (English)

    LIANG Ke-min; GUO Hai-yan; PAN Shi-wei

    2005-01-01

    A naphtha catalytic reforming unit with four reactors in series is analyzed. A physical model is proposed to describe the catalytic reforming radial flow reactor. Kinetics and thermodynamics equations are selected to describe the naphtha catalytic reforming reactions characteristics based on idealizing the complex naphtha mixture by representing the paraffin, naphthene, and aromatic groups by single compounds. The simulation results based above models agree very well with actual operation unit data.

  2. THE SWIFT AGN AND CLUSTER SURVEY. II. CLUSTER CONFIRMATION WITH SDSS DATA

    Energy Technology Data Exchange (ETDEWEB)

    Griffin, Rhiannon D.; Dai, Xinyu [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019 (United States); Kochanek, Christopher S. [Department of Astronomy, Ohio State University, Columbus, OH 43210 (United States); Bregman, Joel N., E-mail: Rhiannon.D.Griffin-1@ou.edu, E-mail: xdai@ou.edu, E-mail: ckochanek@astronomy.ohio-state.edu, E-mail: jbregman@umich.edu [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States)

    2016-01-15

    We study 203 (of 442) Swift AGN and Cluster Survey extended X-ray sources located in the SDSS DR8 footprint to search for galaxy over-densities in three-dimensional space using SDSS galaxy photometric redshifts and positions near the Swift cluster candidates. We find 104 Swift clusters with a >3σ galaxy over-density. The remaining targets are potentially located at higher redshifts and require deeper optical follow-up observations for confirmation as galaxy clusters. We present a series of cluster properties including the redshift, brightest cluster galaxy (BCG) magnitude, BCG-to-X-ray center offset, optical richness, and X-ray luminosity. We also detect red sequences in ∼85% of the 104 confirmed clusters. The X-ray luminosity and optical richness for the SDSS confirmed Swift clusters are correlated and follow previously established relations. The distribution of the separations between the X-ray centroids and the most likely BCG is also consistent with expectation. We compare the observed redshift distribution of the sample with a theoretical model, and find that our sample is complete for z ≲ 0.3 and is still 80% complete up to z ≃ 0.4, consistent with the SDSS survey depth. These analysis results suggest that our Swift cluster selection algorithm has yielded a statistically well-defined cluster sample for further study of cluster evolution and cosmology. We also match our SDSS confirmed Swift clusters to existing cluster catalogs, and find 42, 23, and 1 matches in optical, X-ray, and Sunyaev–Zel’dovich catalogs, respectively, and so the majority of these clusters are new detections.

  3. The AGN content of deep radio surveys and radio emission in radio-quiet AGN. Why every astronomer should care about deep radio fields

    CERN Document Server

    Padovani, P; Miller, N; Kellermann, K I; Mainieri, V; Rosati, P; Tozzi, P; Vattakunnel, S

    2014-01-01

    We present our very recent results on the sub-mJy radio source populations at 1.4 GHz based on the Extended Chandra Deep Field South VLA survey, which reaches ~ 30 {\\mu}Jy, with details on their number counts, evolution, and luminosity functions. The sub-mJy radio sky turns out to be a complex mix of star-forming galaxies and radio-quiet AGN evolving at a similar, strong rate and declining radio-loud AGN. While the well-known flattening of the radio number counts below 1 mJy is mostly due to star-forming galaxies, these sources and AGN make up an approximately equal fraction of the sub-mJy sky. Our results shed also light on a fifty-year-old issue, namely radio emission from radio-quiet AGN, and suggest that it is closely related to star formation, at least at z ~ 1.5 - 2. The implications of our findings for future, deeper radio surveys, including those with the Square Kilometre Array, are also discussed. One of the main messages, especially to non-radio astronomers, is that radio surveys are reaching such f...

  4. AGNES at vibrated gold microwire electrode for the direct quantification of free copper concentrations

    Energy Technology Data Exchange (ETDEWEB)

    Domingos, Rute F., E-mail: rdomingos@ipgp.fr [Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Torre Sul Lab 11-6.3, Av. Rovisco Pais #1, 1049-001 Lisbon (Portugal); Carreira, Sara [Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Torre Sul Lab 11-6.3, Av. Rovisco Pais #1, 1049-001 Lisbon (Portugal); Galceran, Josep [Department of Chemistry, University of Lleida and Agrotecnio, Rovira Roure 191, 25198 Lleida (Spain); Salaün, Pascal [School of Environmental Sciences, University of Liverpool, 4 Brownlow Street, Liverpool L693 GP (United Kingdom); Pinheiro, José P. [LIEC/ENSG, UMR 7360 CNRS – Université de Lorraine, 15 Avenue du Charmois, 54500 Vandoeuvre-les-Nancy (France)

    2016-05-12

    The free metal ion concentration and the dynamic features of the metal species are recognized as key to predict metal bioavailability and toxicity to aquatic organisms. Quantification of the former is, however, still challenging. In this paper, it is shown for the first time that the concentration of free copper (Cu{sup 2+}) can be quantified by applying AGNES (Absence of Gradients and Nernstian equilibrium stripping) at a solid gold electrode. It was found that: i) the amount of deposited Cu follows a Nernstian relationship with the applied deposition potential, and ii) the stripping signal is linearly related with the free metal ion concentration. The performance of AGNES at the vibrating gold microwire electrode (VGME) was assessed for two labile systems: Cu-malonic acid and Cu-iminodiacetic acid at ionic strength 0.01 M and a range of pH values from 4.0 to 6.0. The free Cu concentrations and conditional stability constants obtained by AGNES were in good agreement with stripping scanned voltammetry and thermodynamic theoretical predictions obtained by Visual MinteQ. This work highlights the suitability of gold electrodes for the quantification of free metal ion concentrations by AGNES. It also strongly suggests that other solid electrodes may be well appropriate for such task. This new application of AGNES is a first step towards a range of applications for a number of metals in speciation, toxicological and environmental studies for the direct determination of the key parameter that is the free metal ion concentration. - Highlights: • AGNES principles are valid at the vibrating gold microwire electrode (VGME). • VGME was successfully employed to quantify free Cu concentrations by using AGNES. • Stability constants of labile systems were in good agreement with predictions.

  5. The Relation between Luminous AGNs and Star Formation in Their Host Galaxies

    Science.gov (United States)

    Xu, Lei; Rieke, G. H.; Egami, E.; Haines, C. P.; Pereira, M. J.; Smith, G. P.

    2015-08-01

    We study the relation of active galactic nuclei (AGNs) to star formation in their host galaxies. Our sample includes 205 Type-1 and 85 Type-2 AGNs, 162 detected with Herschel, from fields surrounding 30 galaxy clusters in the Local Cluster Substructure Survey. The sample is identified by optical line widths and ratios after selection to be brighter than 1 mJy at 24 μm. We show that Type-2 AGN [O iii]λ5007 line fluxes at high z can be contaminated by their host galaxies with typical spectrograph entrance apertures (but our sample is not compromised in this way). We use spectral energy distribution (SED) templates to decompose the galaxy SEDs and estimate star formation rates (SFRs), AGN luminosities, and host galaxy stellar masses (described in an accompanying paper). The AGNs arise from massive black holes (˜ 3× {10}8{M}⊙ ) accreting at ˜10% of the Eddington rate and residing in galaxies with stellar mass \\gt 3× {10}10{M}⊙ ; those detected with Herschel have IR luminosity from star formation in the range of {L}{SF,{IR}}˜ {10}10-{10}12{L}⊙ . We find that (1) the specific SFRs in the host galaxies are generally consistent with those of normal star-forming (main sequence) galaxies; (2) there is a strong correlation between the luminosities from star formation and the AGN; and (3) the correlation may not result from a causal connection, but could arise because the black hole mass (and hence AGN Eddington luminosity) and star formation are both correlated with the galaxy mass.

  6. Estimating Black Hole Masses of AGNs using Ultraviolet Emission Line Properties

    Institute of Scientific and Technical Information of China (English)

    Min-Zhi Kong; Xue-Bing Wu; Ran Wang; Jin-Lin Han

    2006-01-01

    Based on measured broad line region sizes in the reverberation-mapping AGN sample, two new empirical relations are introduced to estimate the central black hole masses of radio-loud high-redshift (z > 0.5) AGNs. First, using the archival IUE/HST spectroscopy data at UV band for the reverberation-mapping objects, we obtained two new empirical relations between the BLR size and Mg Ⅱ/C Ⅳ emission line luminosity. Secondly, using the newly determined black hole masses of the reverberation-mapping sample as calibration, we found two new relationships for determining the black hole mass with the full width at half maximum and the luminosity of Mg Ⅱ/C Ⅳ line. We then apply the relations to estimate the black hole masses of the AGNs in the Large Bright Quasar Survey and a sample of radio-loud quasars. For the objects with small radio-loudness, the black hole mass estimated using the RBLR-LMg Ⅱ/C Ⅳ relation is consistent with that from the RBLR-L3000(A)/1350(A) relation. For radio-loud AGNs, however, the mass estimated from the RBLR-LMg Ⅱ/C Ⅳ relation is systematically lower than that from the continuum luminosity L3000 (A)/1350 (A).Because jets could have significant contributions to the UV/optical continuum luminosity of radio-loud AGNs,we emphasize once again that for radio-loud AGNs, the emission line luminosity may be a better tracer of the ionizing luminosity than the continuum luminosity, so that the relations between the BLR size and UV emission line luminosities should be used to estimate the black hole masses of high redshift radio-loud AGNs.

  7. Exploring the nature of Mid-IR selected buried AGN candidates

    Science.gov (United States)

    Haas, Martin; Chini, Rolf; Huchra, John P.; Leipski, Christian; Mueller, Sven A. H.; Ott, Stephan; Siebenmorgen, Ralf; Wilkes, Belinda

    2005-06-01

    Among 3000 sources detected by the ISOCAM Parallel Survey at 6.7 micron in an area of 8 square degrees at high galactic latitude we have discovered a population of extremely infrared unknown objects. With a typical 6.7 micron flux between 4 and 0.7 mJy they have red 2MASS and optical counterparts. The analysis of the ISO and 2MASS colours suggests that we have found AGN with a pronounced near- and mid-IR emission from nuclear dust. We performed optical spectroscopy for 55 of the 80 AGN candidates selected by their red near-mid-IR colors. We find 27% type 1 AGN (redshift range z=0.1-1), 13% type 2 AGN (z=0.1-0.5), and 60% extremely reddened emission line galaxies (ELGs) with LINER and HII type spectra (z=0.07-0.3). Our multi-wavelength examination of the ELGs indicates that they resemble a population different from known IR luminous starburst galaxies. The high MIR/NIR flux ratio and the rather low FIR upper flux limits on IRAS-ADDSCANs argue against a pure starburst nature, suggesting that the red ELGs contain a buried AGN. While new IR surveys from Spitzer will certainly detect new interesting objects of that type, we have already identified a promising IR sample which has been further focussed by optical spectroscopy. Therefore, we apply for 19-38 micron IRS low resolution spectroscopy of 10 red ELGs carefully selected from our sample (6.7 micron flux > 1 mJy). By focussing on really buried AGN candidates and the [Ne V]24.3um and [O IV]25.9um lines, this proposal substantially goes beyond our shallower cycle-1 IRS 5-40 micron observations of MIR selected (mainly type 1 and type 2) AGN.

  8. Modeling The Molecular Composition in an AGN Disk

    CERN Document Server

    Harada, Nanase; Herbst, Eric

    2013-01-01

    We use a high-temperature chemical network to derive the molecular abundances in axisymmetric accretion disk models around active galactic nuclei (AGNs) within 100 pc using simple radial and vertical density and temperature distributions motivated by more detailed physical models. We explore the effects of X-ray irradiation and cosmic ray ionization on the spatial distribution of the molecular abundances of CO, CN, CS, HCN, HCO+, HC3N, C2H, and c-C3H2 using a variety of plausible disk structures. These simple models have molecular regions with a layer of X-ray dominated regions, a midplane without the strong influence of X-rays, and a high-temperature region in the inner portion with moderate X-ray flux where families of polyynes (C$_{\\rm n}$H$_{2}$) and cyanopolyynes can be enhanced. For the high midplane density disks we explore, we find that cosmic rays produced by supernovae do not significantly affect the regions unless the star formation efficiency significantly exceeds that of the Milky Way. We highlig...

  9. Modeling production of e+/--pair plasma in AGNs

    Science.gov (United States)

    Ford, Alex; Medvedev, Mikhail V.

    2016-10-01

    Processes around spinning supermassive black holes in active galactic nuclei (AGN) are believed to determine how relativistic jets are launched and how the black hole energy is extracted. The key question in these processes is the origin of plasma in black hole magnetospheres. The only reasonable mechanism is believed to be the electron-position cascade - the multistage process involving seed photons from an accretion disk, which are Compton up-scattered by charges accelerated in a gap region of a force-free magnetosphere with subsequent photon-photon pair production. In order to explore the process of the e+/- plasma production, we developed a numerical code which models the dynamics of the cascade along magnetic field lines. We demonstrate that plasma production is sensitive to the spectrum of the ambient photon and magnetic fields, the black hole mass and spin, and other parameters. We discuss the results and observational predictions. Supported by KU CLAS and DOE Grant ID0000225143 (07/01/16).

  10. Spectral Properties of AGN with Very Weak [O III] Lines

    Directory of Open Access Journals (Sweden)

    Kovacevic, J.

    2011-06-01

    Full Text Available The spectral properties of a sample of 58 Active GalacticNuclei (AGN spectra, in which emission [O~III] $lambdalambda$4959, 5007 AA lines are weak or totally absent, are analyzed. In order to investigate thephysical reason for the [O~III] emission suppression, the spectral propertiesof the weak [O~III] spectra sample are compared with the same properties of asample of 269 spectra with the strong [O~III] lines. The spectra are obtainedfrom Sloan Digital Sky Survey (SDSS Database. It is found that the objectswith the weak or absent [O~III] $lambdalambda$4959, 5007 AA linesgenerally have the high continuum luminosities (log($lambda$L$_{5100}$ $>$45, that they are very rare at smaller redshifts ($z <$ 0.3 and that theyusually have strong starburst influence. From the sample with weak or absent[O~III] lines, two boundary subgroups may be distinguished: the subgroup witha strong H$beta$ narrow component and subgroup with a very weak or negligibleH$beta$ narrow component. The physical causes for the [O~III] linessuppressing are probably different in these two subgroups: the [O~III] linesare absent in objects with strong narrow H$beta$ probably because of strongstarburst (SB activity, which produces high density of the gas, while in theobjects with the negligible narrow H$beta$, the reason for [O~III] and narrowH$beta$ suppression may be a low covering factor.

  11. AGN and Starburst Radio Emission from Optically Selected QSOs

    CERN Document Server

    Condon, J J; Kimball, Amy E; Ivezic, Zeljko; Perley, R A

    2013-01-01

    We used the 1.4 GHz NVSS to study radio sources in two color-selected QSO samples: a volume-limited sample of 1313 QSOs defined by M_i < -23 in the redshift range 0.2 < z < 0.45 and a magnitude-limited sample of 2471 QSOs with m_r < 18.5 and 1.8 < z < 2.5. About 10% were detected above the 2.4 mJy NVSS catalog limit and are powered primarily by AGNs. The space density of the low-redshift QSOs evolves as rho proportional to (1+z)^6. In both redshift ranges the flux-density distributions and luminosity functions of QSOs stronger than 2.4 mJy are power laws, with no features to suggest more than one kind of radio source. Extrapolating the power laws to lower luminosities predicts the remaining QSOs should be extremely radio quiet, but they are not. Most were detected statistically on the NVSS images with median peak flux densities S_p(mJy/beam) ~ 0.3 and 0.05 in the low- and high-redshift samples, corresponding to 1.4 GHz spectral luminosities log[L(W/Hz)] ~ 22.7$ and 24.1, respectively. We sug...

  12. Is there really a dichotomy in AGN jet power?

    CERN Document Server

    Broderick, J W

    2011-01-01

    To gain new insights into the radio-loud/radio-quiet dichotomy reported for active galactic nuclei, we examine radio loudness as a function of Eddington ratio for a previously published sample of 199 AGN from five different populations. After initially considering radio loudnesses derived using total radio luminosities, we repeat the investigation using core radio luminosities only, applying a previously established mass correction for these core luminosities. In both cases, for Eddington ratios < 1 per cent, Fanaroff-Riley type I and broad-line radio galaxies are on average more radio-loud than Seyfert and low-ionization nuclear emission-line region galaxies. However, the distribution of radio loudnesses for the mass-corrected, core-only sample is much narrower than that of the clearly bimodal total radio loudness distribution. The advantages and disadvantages of using core- or lobe-dominated radio luminosity as a measure of instantaneous jet power are discussed. We furthermore compare the core and total ...

  13. Do the Kepler AGN Light Curves Need Re-processing?

    CERN Document Server

    Kasliwal, Vishal P; Richards, Gordon T; Williams, Joshua; Carini, Michael T

    2015-01-01

    We gauge the impact of spacecraft-induced effects on the inferred variability properties of the light curve of the Seyfert 1 AGN Zw 229-15 observed by \\Kepler. We compare the light curve of Zw 229-15 obtained from the Kepler MAST database with a re-processed light curve constructed from raw pixel data (Williams & Carini, 2015). We use the first-order structure function, $SF(\\delta t)$, to fit both light curves to the damped power-law PSD of Kasliwal, Vogeley & Richards, 2015. On short timescales, we find a steeper log-PSD slope ($\\gamma = 2.90$ to within $10$ percent) for the re-processed light curve as compared to the light curve found on MAST ($\\gamma = 2.65$ to within $10$ percent)---both inconsistent with a damped random walk which requires $\\gamma = 2$. The log-PSD slope inferred for the re-processed light curve is consistent with previous results (Carini & Ryle, 2012, Williams & Carini, 2015) that study the same re-processed light curve. The turnover timescale is almost identical for bot...

  14. Momentum Driving: which physical processes dominate AGN feedback?

    CERN Document Server

    Ostriker, Jeremiah P; Ciotti, Luca; Novak, Gregory S; Proga, Daniel

    2010-01-01

    The deposition of mechanical feedback from a supermassive black hole (SMBH) in an active galactic nucleus (AGN) into the surrounding galaxy occurs via broad-line winds which must carry mass and radial momentum as well as energy. The effect can be summarized by the dimensionless parameter $\\eta=dot{M_outflow}/dot{M_accretion}= (2 \\epsilon_w c^2)/v_w^2$ where ($\\epslion_w \\equiv dot{E}_w/(dot{M_accretion} c^2)$) is the efficiency by which accreted matter is turned into wind energy in the disc surrounding the central SMBH. The outflowing mass and omentum are proportional to $\\eta$, and many prior treatments have essentially assumed that $\\eta=0$. We perform one- and two-dimensional simulations and find that the growth of the central SMBH is very sensitive to the inclusion of the mass and momentum driving but is insensitive to the assumed mechanical efficiency. For example in representative calculations, the omission of momentum and mass feedback leads to an hundred fold increase in the mass of the SMBH to over $...

  15. The QUEST-La Silla AGN Variability Survey

    CERN Document Server

    Cartier, Régis; Coppi, Paolo; Sánchez, Paula; Arévalo, Patricia; Bauer, Franz E; Rabinowitz, David; Zinn, Robert; Muñoz, Ricardo R; Meza, Nicolás

    2015-01-01

    We present the characterization and initial results from the QUEST-La Silla AGN variability survey. This is an effort to obtain well sampled optical light curves in extragalactic fields with unique multi-wavelength observations. We present photometry obtained from 2010 to 2012 in the XMM-COSMOS field, which was observed over 150 nights using the QUEST camera on the ESO-Schmidt telescope. The survey uses a broadband filter, the $Q$-band, similar to the union of the $g$ and the $r$ filters, achieving an intrinsic photometric dispersion of $0.05$ mag, and a systematic error of $0.05$ mag in the zero-point. Since some detectors of the camera show significant non-linearity, we use a linear correlation to fit the zero-points as a function of the instrumental magnitudes, thus obtaining a good correction to the non-linear behavior of these detectors. We obtain good photometry to an equivalent limiting magnitude of $r\\sim 20.5$. Studying the optical variability of X-ray detected sources in the XMM-COSMOS field, we fin...

  16. MULTI-WAVELENGTHS OBSERVATIONS OF AGN: FIFTEEN YEARS ALONG

    Institute of Scientific and Technical Information of China (English)

    Willem Wamsteker

    2001-01-01

    We discuss the results of the extensive efforts done over the past decade on the near environment of the central engines in Active Galactic Nuclei. The observational material is mainly based on the observations from Ground based observatories in the optical, infrared and radio bands, and of space missions like GINGA, IUE, HST, CGRO, ISO, BeppoSAX and RXTE. The availability of this instrumentation with sufficient sensitivity for the study of these objects in the γ-rays, X-rays, EUV, UV as well as Optical, IR and radio domain has opened a complete new insight. Although the results have not yet lead to a complete and full understanding, they have demonstrated with a high degree of probability that the central engines of these objects are associated with massive blackholes. A strong effort will be required from the theoretical side to make certain that we can actually use the results to distinguish between the different model parameters and place the AGN's in their proper place, not only as individual objects of interest,but also to clarify their place in the general scheme of the evolution in the Universe.The results obtained so far have not solved all the early questions, but with the promise of the new instruments a very exciting outlook exists for the future of the study of the physics of accretion in massive Black Holes.

  17. Intermediate mass black holes in AGN disks: I. Production & Growth

    CERN Document Server

    McKernan, B; Lyra, W; Perets, H B

    2012-01-01

    Here we propose a mechanism for efficiently growing intermediate mass black holes (IMBH) in disks around supermassive black holes. Stellar mass objects can efficiently agglomerate when facilitated by the gas disk. Stars, compact objects and binaries can migrate, accrete and merge within disks around supermassive black holes. While dynamical heating by cusp stars excites the velocity dispersion of nuclear cluster objects (NCOs) in the disk, gas in the disk damps NCO orbits. If gas damping dominates, NCOs remain in the disk with circularized orbits and large collision cross-sections. IMBH seeds can grow extremely rapidly by collisions with disk NCOs at low relative velocities, allowing for super-Eddington growth rates. Once an IMBH seed has cleared out its feeding zone of disk NCOs, growth of IMBH seeds can become dominated by gas accretion from the AGN disk. However, the IMBH can migrate in the disk and expand its feeding zone, permitting a super-Eddington accretion rate to continue. Growth of IMBH seeds via N...

  18. MAPCAT: Monitoring AGN with Polarimetry at the Calar Alto Telescopes

    CERN Document Server

    Agudo, Ivan; Gomez, Jose L; Marscher, Alan P; Jorstad, Svetlana G; Heidt, Jochen

    2011-01-01

    We introduce MAPCAT, a long-term observing program for "Monitoring of AGN with Polarimetry at the Calar Alto Telescopes". Multi-spectral-range studies are critical to understand some of the most relevant current problems of high energy astrophysics of blazars such as their high energy emission mechanisms and the location of their gamma-ray emission region through event associations across the spectrum. Adding multi-spectral-range polarimetry allows for even more reliable identification of polarized flares across the spectrum in these kind of objects, as well as for more accurate modeling of their magnetic field. As part of a major international effort to study the long term multi-spectral range polarimetric behavior of blazars, MAPCAT uses -since mid 2007- CAFOS on the 2.2m Telescope at the Calar Alto Observatory (Almeria, Spain) to obtain monthly optical (R-band) photo-polarimetric measurements of a sample of 34 of the brightest gamma-ray, optical, and radio-millimeter blazars accessible from the northern he...

  19. Energy- and momentum-conserving AGN feedback outflows

    CERN Document Server

    Zubovas, Kastytis

    2014-01-01

    It is usually assumed that outflows from luminous AGN are either in the energy-conserving (non-radiative) or in the momentum-conserving (radiative) regime. We show that in a non-spherical geometry the effects of both regimes may manifest at the same time, and that it is the momentum of the outflow that sets the $M_{\\rm BH}-\\sigma$ relation. Considering an initially elliptical distribution of gas in the host galaxy, we show that a non-radiative outflow opens up a wide ``escape route'' over the paths of least resistance. Most of the outflow energy escapes in that direction. At the same time, in the directions of higher resistance, the ambient gas is affected mainly by the incident momentum from the outflow. Quenching SMBH growth requires quenching gas delivery along the paths of highest resistance, and therefore, it is the momentum of the outflow that limits the black hole growth. We present an analytical argument showing that such energy-conserving feedback bubbles driving leaky ambient shells will terminate S...

  20. High School Observations of AGN Using the GTN

    Science.gov (United States)

    McLin, Kevin M.; Jordan, R.; Perkins, A.; Adkins, J.; Cominsky, L.

    2008-03-01

    Students at Deer Valley High School in Antioch, California have undertaken an AGN monitoring program using telescopes of the Global Telescope Network (GTN) and SkyNet. The GTN is a network of small telescopes funded by GLAST to support the science of high energy astrophysics missions, specifically GLAST, Swift and XMM-Newton. It is managed by the NASA E/PO Group at Sonoma State University. SkyNet is a network of small telescopes managed from the University of North Carolina to catch gamma ray burst afterglows. A primary motivator behind both networks is education. In the program outlined here, high school students will schedule, reduce and analyze observations of active galaxies in order to determine if any microflaring activity has occurred. Students will compare their results with previous studies reported in the literature and then report their own results at the Contra Costa County Science and Engineering Fair. This work will give the students direct experience with several aspects of scientific research, including literature searches, data acquisition and analysis, and reporting of results.