Hypercat - Hypercube of AGN tori

NASA Astrophysics Data System (ADS)

Nikutta, Robert; Lopez-Rodriguez, Enrique; Ichikawa, Kohei; Levenson, Nancy A.; Packham, Christopher C.

2018-06-01

AGN unification and observations hold that a dusty torus obscures the central accretion engine along some lines of sight. SEDs of dust tori have been modeled for a long time, but resolved emission morphologies have not been studied in much detail, because resolved observations are only possible recently (VLTI,ALMA) and in the near future (TMT,ELT,GMT). Some observations challenge a simple torus model, because in several objects most of MIR emission appears to emanate from polar regions high above the equatorial plane, i.e. not where the dust supposedly resides.We introduce our software framework and hypercube of AGN tori (Hypercat) made with CLUMPY (www.clumpy.org), a large set of images (6 model parameters + wavelength) to facilitate studies of emission and dust morphologies. We make use of Hypercat to study the morphological properties of the emission and dust distributions as function of model parameters. We find that a simple clumpy torus can indeed produce 10-micron emission patterns extended in polar directions, with extension ratios compatible with those found in observations. We are able to constrain the range of parameters that produce such morphologies.

AGN Obscuration Through Dusty Infrared Dominated Flows. 1; Radiation-Hydrodynamics Solution for the Wind

NASA Technical Reports Server (NTRS)

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 < tau(sub T) < 0.6), is comparable to or greater than the escape velocity. In Compton thick models the maximum value of the vertical component of the velocity is lower than the escape velocity, suggesting that a significant part of our torus is in the form of failed wind. The results demonstrate that obscuration via normal or failed infrared-driven winds is a viable option for the AGN torus problem and AGN unification models. Such winds can also provide an important channel for AGN feedback.

Hypercat - Hypercube of Clumpy AGN Tori

NASA Astrophysics Data System (ADS)

Nikutta, Robert; Lopez-Rodriguez, Enrique; Ichikawa, Kohei; Levenson, Nancy; Packham, Christopher C.

2017-06-01

Dusty tori surrounding the central engines of Active Galactic Nuclei (AGN) are required by the Unification Paradigm, and are supported by many observations, e.g. variable nuclear absorber (sometimes Compton-thick) in X-rays, reverberation mapping in optical/UV, hot dust emission and SED shapes in NIR/MIR, molecular and cool-dust tori observed with ALMA in sub-mm.While models of AGN torus SEDs have been developed and utilized for a long time, the study of the resolved emission morphology (brightness maps) has so far been under-appreciated, presumably because resolved observations of the central parsec in AGN are only possible very recently. Currently, only NIR+MIR interferometry is capable of resolving the nuclear dust emission (but not of producing images, until MATISSE comes online). Furthermore, MIR interferometry has delivered also puzzling results, e.g. that in some resolved sources the light emanates preferentially from polar directions above the "torus" system, and not from the equatorial plane, where most of the dust is located.We are preparing the release of a panchromatic, fully interpolable hypercube of brightness maps and projected dust images for a large number of CLUMPY torus models (Nenkova+2008), that will help facilitate studies of resolved AGN emission and dust morphologies. Together with the cube we will release a comprehensive set of open-source tools (Python) that will enable researches to work efficiently with this large hypercube:* easy sub-cube selection + memory-mapping (mitigating the too-big-for-RAM problem)* multi-dim image interpolation (get an image at any wavelength & model parameter combination)* simulation of observations with telescopes (compute/provide + apply a PSF) and interferometers (get visibilities)* analyze images with respect to the power contained at all scales and orientations (via 2D steerable wavelets), addressing the seemingly puzzling results mentioned aboveA series of papers is in preparation, aiming at solving the

Are Compton-thick AGNs the Missing Link between Mergers and Black Hole Growth?

NASA Astrophysics Data System (ADS)

Kocevski, Dale D.; Brightman, Murray; 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.

2015-12-01

We examine the host morphologies of heavily obscured active galactic nuclei (AGNs) at z∼ 1 to test whether obscured super-massive black hole growth at this epoch is preferentially linked to galaxy mergers. Our sample consists of 154 obscured AGNs with {N}{{H}}\\gt {10}23.5 {{cm}}-2 and z\\lt 1.5. Using visual classifications, we compare the morphologies of these AGNs to control samples of moderately obscured (1022 cm{}-2\\lt {N}{{H}}\\lt {10}23.5 {{cm}}-2) and unobscured ({N}{{H}}\\lt {10}22 {{cm}}-2) AGN. These control AGNs have similar redshifts and intrinsic X-ray luminosities to our heavily obscured AGN. We find that heavily obscured AGNs are twice as likely to be hosted by late-type galaxies relative to unobscured AGNs ({65.3}-4.6+4.1% versus {34.5}-2.7+2.9%) and three times as likely to exhibit merger or interaction signatures ({21.5}-3.3+4.2% versus {7.8}-1.3+1.9%). The increased merger fraction is significant at the 3.8σ level. If we exclude all point sources and consider only extended hosts, we find that the correlation between the merger fraction and obscuration is still evident, although at a reduced statistical significance (2.5σ ). The fact that we observe a different disk/spheroid fraction versus obscuration indicates that the viewing angle cannot be the only thing differentiating our three AGN samples, as a simple unification model would suggest. The increased fraction of disturbed morphologies with obscuration supports an evolutionary scenario, in which Compton-thick AGNs are a distinct phase of obscured super-massive black hole (SMBH) growth following a merger/interaction event. Our findings also suggest that some of the merger-triggered SMBH growth predicted by recent AGN fueling models may be hidden among the heavily obscured, Compton-thick population.

Tori, Discs, and Winds: The First Ten Years of AGN Interferometry

NASA Astrophysics Data System (ADS)

Hönig, Sebastian F.

Infrared (IR) interferometry has made significant progress over the last 10 years to a level that active galactic nuclei (AGN) are now routine targets for long-baseline interferometers. Almost 50 different objects have been studied today in the near-IR and mid-IR. This allowed for detailed characterisation of the dusty environment of the actively growing black holes. It was possible to show directly that the dust must be arranged in clumps, as had been indirectly inferred from theory and unresolved observations. The dust composition seems to undergo significant evolution from galactic scales to the AGN environment, with the hottest dust close to the sublimation front being dominated by large graphite grains. While the overall distribution of the dusty mass is quite diverse from object to object, indications have been found that the dust distribution may depend on AGN luminosity, with more powerful AGN potentially showing more compact dust structures. Arguably the most exciting discovery was the fact that the bulk of the mid-IR emission in Seyfert galaxies emerges from the polar region of the AGN, which is difficult to reconcile with classical torus models. An alternative model is currently being debated that consists of a dusty disc plus a dusty wind driven by radiation pressure from the central source. This finding has major implications for our understanding of AGN unification and will become a focus of the upcoming generation of instruments at the VLTI. More recently, an application of interferometry to cosmology was proposed to measure precise geometric distances to AGN in the Hubble flow. Further exploration of this method may open up interferometry to a new scientific community.

Towards A Complete Census of the Compton-thick AGN population and the NH Distribution of AGN in the Local Universe.

NASA Astrophysics Data System (ADS)

Annuar, A.

2015-09-01

We present updated results from an ongoing project to establish the most unbiased census of the Compton- thick active galactic nucleus (CTAGN) population and the intrinsic column density (NH) distribution of the overall AGN population in the local universe, using a sample of mid-infrared (mid-IR) selected AGN within 15 Mpc. We find that 20% of the AGN in the sample are bona-fide CTAGN based upon hard X-ray studies (E > 10 keV). More candidates are then selected using multiwavelength techniques, i.e. mid-IR:X-ray and optical [OIII]5007:X-ray flux ratios. Based on these analyses along with evidence from previous literature, we initially find a further 25% of potential candidates. We then observed two of these candidates, NGC 5643 and NGC 3486, using NuSTAR and is able to confirm the former as a CTAGN and rule out the latter as an obscured AGN. This constrains the total CTAGN population in the sample to 25-40%, though it could potentially be as high as 65% accounting for those that still lack data. Finally, we use these results to estimate the intrinsic NH distribution of the local AGN population. Two more of our CTAGN candidates are scheduled to be observed by NuSTAR, bringing the completeness of hard X-ray energy data of the sample to 65%. This work provides a well-defined local benchmark for AGN unification studies.

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

NASA Astrophysics Data System (ADS)

Ballantyne, David R.

2016-04-01

Deep X-ray surveys have provided a comprehensive and largely unbiased view of 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 demonstrated at z ≈0 and 0.9, and clear luminosity dependence in the AGN bias and mean halo mass is predicted at both z. The results support the idea that there are at least two different modes of AGN triggering: one, at high luminosity, that only occurs in high mass, highly biased haloes, and one that can occur over a wide range of halo masses and leads to luminosities that are correlated with halo mass. This latter mode dominates at z<0.9. The CLFs for Type 2 and Type 1 AGNs are also constrained at z ≈0, and we find evidence that unobscured quasars are more likely to be found in higher mass halos than obscured quasars. Thus, the AGN unification model seems to fail at quasar luminosities.

Supersymmetry, Supergravity, and Unification

NASA Astrophysics Data System (ADS)

Nath, Pran

2016-12-01

Dedication; Preface; 1. A brief history of unification; 2. Gravitation; 3. Non-abelian gauge theory; 4. Spontaneous breaking of global and local symmetries; 5. The Standard Model; 6. Anomalies; 7. Effective Lagrangians; 8. Supersymmetry; 9. Grand unification; 10. MSSM Lagrangian; 11. N = 1 supergravity; 12. Coupling of supergravity with matter and gauge fields; 13. Supergravity grand unification; 14. Phenomenology of supergravity grand unification; 15. CP violation in supergravity unified theories; 16. Proton stability in supergravity unified theories; 17. Cosmology, astroparticle physics and SUGRA unification; 18. Extended supergravities and supergravities from superstrings; 19. Specialized topics; 20. The future of unification; 21. Appendices; 22. Notations, conventions, and formulae; 23. Physical constants; 24. List of books and reviews for further reading; Index.

Model-based object classification using unification grammars and abstract representations

NASA Astrophysics Data System (ADS)

Liburdy, Kathleen A.; Schalkoff, Robert J.

1993-04-01

The design and implementation of a high level computer vision system which performs object classification is described. General object labelling and functional analysis require models of classes which display a wide range of geometric variations. A large representational gap exists between abstract criteria such as `graspable' and current geometric image descriptions. The vision system developed and described in this work addresses this problem and implements solutions based on a fusion of semantics, unification, and formal language theory. Object models are represented using unification grammars, which provide a framework for the integration of structure and semantics. A methodology for the derivation of symbolic image descriptions capable of interacting with the grammar-based models is described and implemented. A unification-based parser developed for this system achieves object classification by determining if the symbolic image description can be unified with the abstract criteria of an object model. Future research directions are indicated.

A MODEL FOR TYPE 2 CORONAL LINE FOREST (CLiF) AGNs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Glidden, Ana; Rose, Marvin; Elvis, Martin

2016-06-10

We present a model for the classification of Coronal Line Forest Active Galactic Nuclei (CLiF AGNs). CLiF AGNs are of special interest due to their remarkably large number of emission lines, especially forbidden high-ionization lines (FHILs). Rose et al. 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 AGNs laboratories to test AGN-torus models. Modeling an AGN as an accreting supermassive black hole surrounded by a cylinder of dust and gas, we show a relationship between the viewing angle and the revealedmore » 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 [Fe vii] λ 6087 emission for a number of intermediate angles (30°, 40°, and 50°) and compare the results with the luminosity of the observed emission line from six known CLiF AGNs. We find that there is good agreement between our model and the observational results. The model also enables us to determine the relationship between the type 2:type 1 AGN fraction vs the ratio of torus height to radius, h / r .« less

Modeling optical and UV polarization of AGNs. IV. Polarization timing

NASA Astrophysics Data System (ADS)

Rojas Lobos, P. A.; Goosmann, R. W.; Marin, F.; Savić, D.

2018-03-01

Context. Optical observations cannot resolve the structure of active galactic nuclei (AGN), and a unified model for AGN was inferred mostly from indirect methods, such as spectroscopy and variability studies. Optical reverberation mapping allowed us to constrain the spatial dimension of the broad emission line region and thereby to measure the mass of supermassive black holes. Recently, reverberation was also applied to the polarized signal emerging from different AGN components. In principle, this should allow us to measure the spatial dimensions of the sub-parsec reprocessing media. Aim. We conduct numerical modeling of polarization reverberation and provide theoretical predictions for the polarization time lag induced by different AGN components. The model parameters are adjusted to the observational appearance of the Seyfert 1 galaxy NGC 4151. Methods: We modeled scattering-induced polarization and tested different geometries for the circumnuclear dust component. Our tests included the effects of clumpiness and different dust prescriptions. To further extend the model, we also explored the effects of additional ionized winds stretched along the polar direction, and of an equatorial scattering ring that is responsible for the polarization angle observed in pole-on AGN. The simulations were run using a time-dependent version of the STOKES code. Results: Our modeling confirms the previously found polarization characteristics as a function of the observer`s viewing angle. When the dust adopts a flared-disk geometry, the lags reveal a clear difference between type 1 and type 2 AGN. This distinction is less clear for a torus geometry where the time lag is more sensitive to the geometry and optical depth of the inner surface layers of the funnel. The presence of a scattering equatorial ring and ionized outflows increased the recorded polarization time lags, and the polar outflows smooths out dependence on viewing angle, especially for the higher optical depth of the

A model for AGN variability on multiple time-scales

NASA Astrophysics Data System (ADS)

Sartori, Lia F.; Schawinski, Kevin; Trakhtenbrot, Benny; Caplar, Neven; Treister, Ezequiel; Koss, Michael J.; Urry, C. Megan; Zhang, C. E.

2018-05-01

We present a framework to link and describe active galactic nuclei (AGN) variability on a wide range of time-scales, from days to billions of years. In particular, we concentrate on the AGN variability features related to changes in black hole fuelling and accretion rate. In our framework, the variability features observed in different AGN at different time-scales may be explained as realisations of the same underlying statistical properties. In this context, we propose a model to simulate the evolution of AGN light curves with time based on the probability density function (PDF) and power spectral density (PSD) of the Eddington ratio (L/LEdd) distribution. Motivated by general galaxy population properties, we propose that the PDF may be inspired by the L/LEdd distribution function (ERDF), and that a single (or limited number of) ERDF+PSD set may explain all observed variability features. After outlining the framework and the model, we compile a set of variability measurements in terms of structure function (SF) and magnitude difference. We then combine the variability measurements on a SF plot ranging from days to Gyr. The proposed framework enables constraints on the underlying PSD and the ability to link AGN variability on different time-scales, therefore providing new insights into AGN variability and black hole growth phenomena.

Modeling IR SED of AGN with Spitzer and Herschel data

NASA Astrophysics Data System (ADS)

Feltre, A.

2012-12-01

One of the remaining open issues in the context of the analysis of Active Galactic Nuclei (AGN) is the evidence that nuclear gravitational accretion is often accompanied by a concurrent starburst (SB) activity. What is, in this picture, the role played by the obscur- ing dust around the nucleus and what do the state of the art AGN torus models have to say? Can the IR data provided by Spitzer and Herschel help us in extensively investigate both phenomena and, if so, how and with what limitations? In this paper we present our contribution to the efforts of answering these questions. We show some of the main results coming from a comparative study of various AGN SED modeling approaches, focusing mostly on the much-debated issue about the morphology of the dust distribution in the toroidal structure surrounding the AGN. We found that the properties of dust in AGN as measured by matching observations (be it broad band IR photometry or IR spectra) with models, strongly depend on the choice of the dust distribution. Then, we present the spec- tral energy distribution (SED) fitting procedure we developed, making make the best use of Spitzer and Herschel SPIRE mid- and far-IR observations, to dig into the role played by the possible presence of an AGN on the host galaxy's properties.

Beyond Hydrodynamic Modeling of AGN Heating in Galaxy Clusters

NASA Astrophysics Data System (ADS)

Yang, Hsiang-Yi Karen

Clusters of galaxies hold a unique position in hierarchical structure formation - they are both powerful cosmological probes and excellent astrophysical laboratories. Accurate modeling of the cluster properties is crucial for reducing systematic uncertainties in cluster cosmology. However, theoretical modeling of the intracluster medium (ICM) has long suffered from the "cooling-flow problem" - clusters with short central times or cool cores (CCs) are predicted to host massive inflows of gas that are not observed. Feedback from active galactic nuclei (AGN) is by far the most promising heating mechanism to counteract radiative cooling. Recent hydrodynamic simulations have made remarkable progress reproducing properties of the CCs. However, there remain two major questions that cannot be probed using purely hydrodynamic models: (1) what are the roles of cosmic rays (CRs)? (2) how is the existing picture altered when the ICM is modeled as weakly collisional plasma? We propose to move beyond limitations of pure hydrodynamics and progress toward a complete understanding of how AGN jet-inflated bubbles interact with their surroundings and provide heat to the ICM. Our objectives include: (1) understand how CR-dominated bubbles heat the ICM; (2) understand bubble evolution and sound-wave dissipation in the ICM with different assumptions of plasma properties, e.g., collisionality of the ICM, with or without anisotropic transport processes; (3) Develop a subgrid model of AGN heating that can be adopted in cosmological simulations based on state-of-the-art isolated simulations. We will use a combination of analytical calculations and idealized simulations to advance our understanding of each individual physical process. We will then perform the first three-dimensional (3D) magnetohydrodynamic (MHD) simulations of self-regulated AGN feedback with relevant CR and anisotropic transport processes in order to quantify the amount and distribution of heating from the AGN. Our

[Transfer of the AGnES concept to the regular German health-care system: legal evaluation, reimbursement, qualification].

PubMed

van den Berg, N; Kleinke, S; Heymann, R; Oppermann, R F; Jakobi, B; Hoffmann, W

2010-05-01

According to an amendment of German social security legislation, the AGnES concept of delegation of certain tasks of medical care, especially house calls, by general practitioners (GPs) to qualified practice employees (AGnES employees), will be transferred into the regular German health care system from January 2009 onward. The concept was developed to support GPs in regions with imminent gaps in primary care. Patient data, the specifically delegated and all other activities carried out by the AGnES employees in the AGnES projects were digitally documented. Additionally, the participating GPs, AGnES employees and patients underwent a set of standardised interviews. A curriculum to qualify the AGnES employees and to define the requirements needed was developed. A legal assessment of all delegated activities was carried out, and an economical model to calculate the necessary allowance was calculated. In seven model projects in four federal states in Germany, 11,228 house calls were carried out involving 1,424, mostly multimorbid, patients (mean age: 78.6 years). A modular structured curriculum, considering the basic education and acquired competences, was developed. It allows for an individual qualification of the AGnES employees. The result of the legal assessment was the central relevance of the qualification of the practice employees according to the AGnES curriculum as the essential condition for carrying out the entire range of activities of the AGnES concept. The economic model revealed euro 21.58 for a house call by an AGnES employee. The underlying model referred to underserved regions. A successful transfer of the AGnES concept with a high standard of quality into regular health-care depends on several factors. Of particular importance is the specific qualification of the practice employees, which is a central legal condition for the delegation of medical tasks from GPs to AGnEs employees. A second determining factor is also an adequate reimbursement within

String unification scale and the hyper-charge Kac-Moody level in the non-supersymmetric standard model

NASA Astrophysics Data System (ADS)

Cho, Gi-Chol; Hagiwara, Kaoru

1998-02-01

The string theory predicts the unification of the gauge couplings and gravity. The minimal supersymmetric Standard Model, however, gives the unification scale ~2x1016 GeV which is significantly smaller than the string scale ~5x1017 GeV of the weak coupling heterotic string theory. We study the unification scale of the non-supersymmetric minimal Standard Model quantitatively at the two-loop level. We find that the unification scale should be at most ~4x1016 GeV and the desired Kac-Moody level of the hyper-charge coupling should be 1.33<~kY<~1.35.

Probing AGN Accretion Physics through AGN Variability: Insights from Kepler

NASA Astrophysics Data System (ADS)

Kasliwal, Vishal Pramod

Active Galactic Nuclei (AGN) exhibit large luminosity variations over the entire electromagnetic spectrum on timescales ranging from hours to years. The variations in luminosity are devoid of any periodic character and appear stochastic. While complex correlations exist between the variability observed in different parts of the electromagnetic spectrum, no frequency band appears to be completely dominant, suggesting that the physical processes producing the variability are exceedingly rich and complex. In the absence of a clear theoretical explanation of the variability, phenomenological models are used to study AGN variability. The stochastic behavior of AGN variability makes formulating such models difficult and connecting them to the underlying physics exceedingly hard. We study AGN light curves serendipitously observed by the NASA Kepler planet-finding mission. Compared to previous ground-based observations, Kepler offers higher precision and a smaller sampling interval resulting in potentially higher quality light curves. Using structure functions, we demonstrate that (1) the simplest statistical model of AGN variability, the damped random walk (DRW), is insufficient to characterize the observed behavior of AGN light curves; and (2) variability begins to occur in AGN on time-scales as short as hours. Of the 20 light curves studied by us, only 3-8 may be consistent with the DRW. The structure functions of the AGN in our sample exhibit complex behavior with pronounced dips on time-scales of 10-100 d suggesting that AGN variability can be very complex and merits further analysis. We examine the accuracy of the Kepler pipeline-generated light curves and find that the publicly available light curves may require re-processing to reduce contamination from field sources. We show that while the re-processing changes the exact PSD power law slopes inferred by us, it is unlikely to change the conclusion of our structure function study-Kepler AGN light curves indicate

Discovery of 21 New Changing-look AGNs: Study on Evolution of AGNs and AGN Host Galaxies

NASA Astrophysics Data System (ADS)

Yang, Qian; Wu, Xuebing; Fan, Xiaohui; Jiang, Linhua; McGreer, Ian; Shangguan, Jinyi; Yao, Su; Wang, Bingquan; Joshi, Ravi; Green, Richard F.; Wang, Feige; Feng, Xiaotong; Fu, Yuming; Yang, Jinyi; Liu, Yuanqi

2018-01-01

The rare case of changing-look (CL) AGNs, with the appearance or disappearance of broad Balmer emission lines within a few years, challenges our understanding of the AGN unified model. We present a sample of 21 new CL AGNs at 0.08 < z < 0.58. The new sample doubles the number of such objects known to date. These new CL AGNs were discovered by several ways, from repeat spectra in the SDSS, repeat spectra in the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) and SDSS, and from photometric variability and new spectroscopic observations. The estimated upper limits of transition timescale of the CL AGNs in this sample span from 0.9 to 13 years in rest-frame. The continuum flux in the optical and mid-infrared becomes brighter when the CL AGNs turn on, or vice versa. Variations of more than 0.2 mag in the mid-infrared W1 band, from the Wide-field Infrared Survey Explorer (WISE), were detected in 15 CL AGNs during the transition. The optical and mid-infrared variability is not consistent with the scenario of variable obscuration in 10 CL AGNs at higher than 3σ confidence level. We confirm a bluer-when-brighter trend in the optical. However, the mid-infrared colors W1‑W2 become redder when the objects become brighter in the W1 band, possibly due to a stronger hot dust contribution in the W2 band when the AGN activity becomes stronger. The physical mechanism of type transition is important for understanding the evolution of AGNs. The rare CL AGNs provide exceptional cases for the black hole and host stellar velocity dispersion relation studies at higher redshift. The faint state spectrum can be used to obtain the host stellar velocity dispersion without contamination from AGN component, and the bright state spectrum can be used to calculate the black hole mass with broad Balmer emission lines. The images at the non-AGN phase of CL AGNs are useful for studies of AGN host galaxies avoiding contamination from the luminous central engines.

Unification of gauge and Yukawa couplings

NASA Astrophysics Data System (ADS)

Abdalgabar, Ammar; Khojali, Mohammed Omer; Cornell, Alan S.; Cacciapaglia, Giacomo; Deandrea, Aldo

2018-01-01

The unification of gauge and top Yukawa couplings is an attractive feature of gauge-Higgs unification models in extra-dimensions. This feature is usually considered difficult to obtain based on simple group theory analyses. We reconsider a minimal toy model including the renormalisation group running at one loop. Our results show that the gauge couplings unify asymptotically at high energies, and that this may result from the presence of an UV fixed point. The Yukawa coupling in our toy model is enhanced at low energies, showing that a genuine unification of gauge and Yukawa couplings may be achieved.

X-Ray Absorbed, Broad-Lined, Red AGN and the Cosmic X-Ray Background

NASA Technical Reports Server (NTRS)

Mushotzky, Richard (Technical Monitor); Wilkes, Belinda

2005-01-01

detectable in the typically low S/N data of X-ray surveys. Even if absorption is present in only half of the population, the large number of 'red' AGN suggests a development of unification models, where the continuum source is surrounded, over a substantial solid angle, by the wind or atmosphere of an accretion disk/torus. X-ray observations of such AGN not only provide a check on the presence of absorption, but also a unique probe of the absorbing material. Improved information on their space density, in particular as a function of redshift, will soon be provided by Spitzer-Chandra wide area surveys, allowing better estimates of both the importance of red AGN to the full AGN population and their contribution to the CXRB.

Obscured and powerful AGN and starburst activities at z ~ 3.5

NASA Astrophysics Data System (ADS)

Polletta, M.; Omont, A.; Berta, S.; Bergeron, J.; Stalin, C. S.; Petitjean, P.; Giorgetti, M.; Trinchieri, G.; Srianand, R.; McCracken, H. J.; Pei, Y.; Dannerbauer, H.

2008-12-01

Aims: Short phases of coeval powerful starburst and AGN activity during the lifetimes of the most massive galaxies are predicted by various models of galaxy formation and evolution. In spite of their recurrence and high luminosity, such events are rarely observed. Finding such systems, understanding their nature, and constraining their number density can provide key constraints to galaxy evolutionary models and insights into the interplay between starburst and AGN activities. Methods: We report the discovery of two sources at z=3.867 and z=3.427 that exhibit both powerful starburst and AGN activities. They benefit from multi-wavelength data from radio to X rays from the CFHTLS-D1/SWIRE/XMDS surveys. Follow-up optical and near-infrared spectroscopy, and millimeter IRAM/MAMBO observations are also available. We performed a multi-wavelength analysis of their spectral energy distributions with the aim of understanding the origin of their emission and constraining their luminosities. A comparison with other composite systems at similar redshifts from the literature is also presented. Results: The AGN and starburst bolometric luminosities are 1013 L⊙. The AGN emission dominates at X ray, optical, mid-infrared wavelengths, and probably also in the radio. The starburst emission dominates in the far-infrared. The estimated star formation rates range from 500 to 3000 M⊙/yr. The AGN near-infrared and X ray emissions are heavily obscured in both sources with an estimated dust extinction {A_V} ≥ 4, and Compton-thick gas column densities. The two sources are the most obscured and most luminous AGNs detected at millimeter wavelengths currently known. Conclusions: The sources presented in this work are heavily obscured QSOs, but their properties are not fully explained by the standard AGN unification model. In one source, the ultraviolet and optical spectra suggest the presence of outflowing gas and shocks, and both sources show emission from hot dust, most likely in the

Accretion disk modeling of AGN continuum using non-LTE stellar atmospheres. [active galactic nuclei (AGN)

NASA Technical Reports Server (NTRS)

Sun, Wei-Hsin; Malkan, Matthew A.

1988-01-01

Active galactic nuclei (AGN) accretion disk spectra were calculated using non-LTE stellar atmosphere models for Kerr and Schwarzschild geometries. It is found that the Lyman limit absorption edge, probably the most conclusive observational evidence for the accretion disk, would be drastically distorted and displaced by the relativistic effects from the large gravitational field of the central black hole and strong Doppler motion of emitting material on the disk surface. These effects are especially pronounced in the Kerr geometry. The strength of the Lyman limit absorption is very sensitive to the surface gravity in the stellar atmosphere models used. For models at the same temperature but different surface gravities, the strength of the Lyman edge exhibits an almost exponential decrease as the surface gravity approach the Eddington limit, which should approximate the thin disk atmosphere. The relativistic effects as well as the vanishing of the Lyman edge at the Eddington gravity may be the reasons that not many Lyman edges in the rest frames of AGNs and quasars are found.

Steps Toward Unveiling the True Population of AGN: Photometric Selection of Broad-Line AGN

NASA Astrophysics Data System (ADS)

Schneider, Evan; Impey, C.

2012-01-01

We present an AGN selection technique that enables identification of broad-line AGN using only photometric data. An extension of infrared selection techniques, our method involves fitting a given spectral energy distribution with a model consisting of three physically motivated components: infrared power law emission, optical accretion disk emission, and host galaxy emission. Each component can be varied in intensity, and a reduced chi-square minimization routine is used to determine the optimum parameters for each object. Using this model, both broad- and narrow-line AGN are seen to fall within discrete ranges of parameter space that have plausible bounds, allowing physical trends with luminosity and redshift to be determined. Based on a fiducial sample of AGN from the catalog of Trump et al. (2009), we find the region occupied by broad-line AGN to be distinct from that of quiescent or star-bursting galaxies. Because this technique relies only on photometry, it will allow us to find AGN at fainter magnitudes than are accessible in spectroscopic surveys, and thus probe a population of less luminous and/or higher redshift objects. With the vast availability of photometric data in large surveys, this technique should have broad applicability and result in large samples that will complement X-ray AGN catalogs.

Corpus-Based Optimization of Language Models Derived from Unification Grammars

NASA Technical Reports Server (NTRS)

Rayner, Manny; Hockey, Beth Ann; James, Frankie; Bratt, Harry; Bratt, Elizabeth O.; Gawron, Mark; Goldwater, Sharon; Dowding, John; Bhagat, Amrita

2000-01-01

We describe a technique which makes it feasible to improve the performance of a language model derived from a manually constructed unification grammar, using low-quality untranscribed speech data and a minimum of human annotation. The method is on a medium-vocabulary spoken language command and control task.

Extragalactic gamma-ray background from AGN winds and star-forming galaxies in cosmological galaxy-formation models

NASA Astrophysics Data System (ADS)

Lamastra, A.; Menci, N.; Fiore, F.; Antonelli, L. A.; Colafrancesco, S.; Guetta, D.; Stamerra, A.

2017-10-01

We derive the contribution to the extragalactic gamma-ray background (EGB) from active galactic nuclei (AGN) winds and star-forming galaxies by including a physical model for the γ-ray emission produced by relativistic protons accelerated by AGN-driven and supernova-driven shocks into a state-of-the-art semi-analytic model of galaxy formation. This is based on galaxy interactions as triggers of AGN accretion and starburst activity and on expanding blast waves as the mechanism to communicate outwards the energy injected into the interstellar medium by the active nucleus. We compare the model predictions with the latest measurement of the EGB spectrum performed by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi) in the range between 100 MeV and 820 GeV. We find that AGN winds can provide 35 ± 15% of the observed EGB in the energy interval Eγ = 0.1-1 GeV, for 73 ± 15% at Eγ = 1-10 GeV, and for 60 ± 20% at Eγ ≳10 GeV. The AGN wind contribution to the EGB is predicted to be larger by a factor of 3-5 than that provided by star-forming galaxies (quiescent plus starburst) in the hierarchical clustering scenario. The cumulative γ-ray emission from AGN winds and blazars can account for the amplitude and spectral shape of the EGB, assuming the standard acceleration theory, and AGN wind parameters that agree with observations. We also compare the model prediction for the cumulative neutrino background from AGN winds with the most recent IceCube data. We find that for AGN winds with accelerated proton spectral index p = 2.2-2.3, and taking into account internal absorption of γ-rays, the Fermi-LAT and IceCube data could be reproduced simultaneously.

Subgrid Modeling of AGN-driven Turbulence in Galaxy Clusters

NASA Astrophysics Data System (ADS)

Scannapieco, Evan; Brüggen, Marcus

2008-10-01

Hot, underdense bubbles powered by active galactic nuclei (AGNs) 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 is 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 outward in the hydrostatic intracluster medium (ICM), much as large airbursts lead to a distinctive "mushroom cloud" structure as they rise in the hydrostatic atmosphere of Earth. Properly capturing the evolution of such clouds has important implications for many ICM properties. In particular, it significantly changes the impact of AGNs on the distribution of entropy and metals in cool-core clusters such as Perseus.

Is there a relationship between AGN and star formation in IR-bright AGNs?

NASA Astrophysics Data System (ADS)

Dai, Y. Sophia; Wilkes, Belinda J.; Bergeron, Jacqueline; Kuraszkiewicz, Joanna; Omont, Alain; Atanas, Adam; Teplitz, Harry I.

2018-05-01

We report the relationship between the luminosities of active galactic nuclei (AGNs) and the rates of star formation (SF) for a sample of 323 far-infrared (FIR)-detected AGNs. This sample has a redshift range of 0.2 AGN hosts, the total IR luminosity (8-1000 μm) has a significant AGN contribution (average˜20%), and we suggest using the FIR luminosity (30-1000 μm) as a more reliable star formation rate (SFR) estimator. We also conclude that monochromatic luminosities at 60 and 100 μ m are also good SFR indicators with negligible AGN contributions, and are less sensitive than integrated infrared luminosities to the shape of the AGN SED, which is uncertain at λ >100 μm. Significant bivariate LX-LIR correlations are found, which remain significant in the combined sample when using residual partial correlation analysis to account for the inherent redshift dependence. No redshift or mass dependence is found for the ratio between SFR and black hole accretion rate (BHAR), which has a mean and scatter of log (SFR/BHAR) =3.1 ± 0.5, agreeing with the local mass ratio between supermassive black hole and host galaxies. The large scatter in this ratio and the strong AGN-SF correlation found in these IR-bright AGNs are consistent with the scenario of an AGN-SF dependence on a common gas supply, regardless of the evolutionary model.

The Disk-Jet Connection in Radio-Loud AGN: The X-Ray Perspective

NASA Technical Reports Server (NTRS)

Sambruna, Rita

2008-01-01

Unification schemes assume that radio-loud active galactic nuclei (AGN) contain an accretion disk and a relativistic jet perpendicular to the disk, and an obscuring molecular torus. The jet dominance decreases with larger viewing angles from blazars to Broad-Line and Narrow-Line Radio Galaxies. A fundamental question is how accretion and ejecta are related. The X-rays provide a convenient window to study these issues, as they originate in the innermost nuclear regions and penetrate large obscuring columns. I review the data, using observations by Chandra but also from other currently operating high-energy experiments. Synergy with the upcoming GLAST mission will also be highlighted.

The SIX survey: evolution and properties of AGN in the local universe

NASA Astrophysics Data System (ADS)

Bottacini, Eugenio

2014-07-01

evolution of AGN in the local universe discussing the X-ray luminosity function. The properties of the AGN circum-nuclear environment will be discussed checking the consistency with the AGN unification scheme. Also I will compare the results from the SIX survey to the results predicted for the NuSTAR survey. Finally preliminary results of the all-sky SIX survey are presented.

VizieR Online Data Catalog: Radio-loud AGN with relativistic jets (Olguin-Iglesias+, 2016)

NASA Astrophysics Data System (ADS)

Olguin-Iglesias, A.; Leon-Tavares, J.; Kotilainen, J. K.; Chavushyan, V.; Tornikoski, M.; Valtaoja, E.; Anorve, C.; Valdes, J.; Carrasco, L.

2017-11-01

The sample of sources analysed in this work is a sub-sample of variable radio-loud AGN monitored at 7mm (S7mm>1Jy) with the Aalto University Metsahovi Radio Observatory, in Finland (http://metsahovi.aalto.fi/en/) since the last 30 years (Terasranta et al., 1992A&AS...94..121T; Teraesranta et al., 1998, Cat. J/A+AS/132/305; Leon-Tavares et al., 2011A&A...532A.146L; Nieppola et al., 2011, Cat. J/A+A/535/A69). According to the AGN unification scheme (Antonucci, 1993ARA&A..31..473A; Urry & Padovani, 1995PASP..107..803U), FSRQ and BL Lacs are those AGN whose relativistic jets point towards the Earth. Observations were made with the Nordic Optical Telescope (NOT) at La Roque de los Muchachos, La Palma, Canarias, Spain. They were conducted between 2011 May 09 and September 15 using the near-infrared Camera (NOTCam)3 on the NOT. NOTcam field of view is 4'x4' with a pixel scale of 0.234-arcsec/pixel designed to be used in the range from 0.8 to 2.5um in the bands J, H and K. (1 data file).

Starburst or AGN dominance in submm-luminous candidate AGN

NASA Astrophysics Data System (ADS)

Coppin, Kristen; Alexander, Dave; Aretxaga, Itziar; Blain, Andrew; Chapman, Scott; Clements, Dave; Dunlop, James; Dunne, Loretta; Dye, Simon; Farrah, Duncan; Hughes, David; Ivison, Rob; Kim, Sungeun; Menendez-Delmestre, Karin; Oliver, Sebastian; Page, Mat; Pope, Alexandra; Rowan-Robinson, Michael; Scott, Douglas; Smail, Ian; Swinbank, Mark; Vaccari, Mattia; van Kampen, Eelco

2008-03-01

It is widely believed that starbursts/ULIRGs and AGN activity are triggered by galaxy interactions and merging; and sub-mm selected galaxies (SMGs) seem to be simply high redshift ULIRGs, observed near the peak of activity. In this evolutionary picture every SMG would host an AGN, which would eventually grow a black hole strong enough to blow off all of the gas and dust leaving an optically luminous QSO. In order to probe this evolutionary sequence, a crucial sub-sample to focus on would be the 'missing link' sources, which demonstrate both strong starburst and AGN signatures and to determine if the starburst is the main power source even in SMGs when we have evidence that an AGN is present. The best way to determine if a dominant AGN is present is to look in the mid-IR for their signatures, since often even deep X-ray observations miss identifying the presence of AGN in heavily dust-obscured SMGs. We have selected a sample of SMGs which are good candidates for harboring powerful AGN on the basis of their IRAC colours (S8um/S4.5um>2). Once we confirm these SMGs are AGN-dominated, we can then perform an audit of the energy balance between star-formation and AGN within this special sub-population of SMGs where the BH has grown appreciably to begin heating the dust emission. The proposed observations with IRS will probe the physics of how SMGs evolve from a cold-dust starburst-dominated ULIRG to an AGN/QSO by measuring the level of the mid-IR continuum, PAH luminosity, and Si absorption in these intermediate `transitory' AGN/SMGs.

PUP: An Architecture to Exploit Parallel Unification in Prolog

DTIC Science & Technology

1988-03-01

environment stacking mo del similar to the Warren Abstract Machine [23] since it has been shown to be super ior to other known models (see [21]). The storage...execute in groups of independent operations. Unifications belonging to different group s may not overlap. Also unification operations belonging to the...since all parallel operations on the unification units must complete before any of the units can star t executing the next group of parallel

AGN Obscuration Through Dusty Infrared Dominated Flows. II. Multidimensional, Radiation-Hydrodynamics Modeling

NASA Technical Reports Server (NTRS)

Dorodnitsyn, Anton; Kallman, Tim; Bisno\\vatyiI-Kogan, Gennadyi

2011-01-01

We explore a detailed model in which the active galactic nucleus (AGN) obscuration results from the extinction of AGN radiation in a global ow driven by the pressure of infrared radiation on dust grains. We assume that external illumination by UV and soft X-rays of the dusty gas located at approximately 1pc away from the supermassive black hole is followed by a conversion of such radiation into IR. Using 2.5D, time-dependent radiation hydrodynamics simulations in a ux-limited di usion approximation we nd that the external illumination can support a geometrically thick obscuration via out ows driven by infrared radiation pressure in AGN with luminosities greater than 0:05 L(sub edd) and Compton optical depth, Tau(sub T) approx > & 1.

AGN coronal emission models - I. The predicted radio emission

NASA Astrophysics Data System (ADS)

Raginski, I.; Laor, Ari

2016-06-01

Accretion discs in active galactic nucleus (AGN) may be associated with coronal gas, as suggested by their X-ray emission. Stellar coronal emission includes radio emission, and AGN corona may also be a significant source for radio emission in radio quiet (RQ) AGN. We calculate the coronal properties required to produce the observed radio emission in RQ AGN, either from synchrotron emission of power-law (PL) electrons, or from cyclosynchrotron emission of hot mildly relativistic thermal electrons. We find that a flat spectrum, as observed in about half of RQ AGN, can be produced by corona with a disc or a spherical configuration, which extends from the innermost regions out to a pc scale. A spectral break to an optically thin power-law emission is expected around 300-1000 GHz, as the innermost corona becomes optically thin. In the case of thermal electrons, a sharp spectral cut-off is expected above the break. The position of the break can be measured with very long baseline interferometry observations, which exclude the cold dust emission, and it can be used to probe the properties of the innermost corona. Assuming equipartition of the coronal thermal energy density, the PL electrons energy density, and the magnetic field, we find that the energy density in a disc corona should scale as ˜R-1.3, to get a flat spectrum. In the spherical case the energy density scales as ˜R-2, and is ˜4 × 10-4 of the AGN radiation energy density. In Paper II we derive additional constraints on the coronal parameters from the Gudel-Benz relation, Lradio/LX-ray ˜ 10- 5, which RQ AGN follow.

Unveiling Obscured AGN with X-ray Spectral Analysis

NASA Astrophysics Data System (ADS)

LaMassa, Stephanie M.; Yaqoob, Tahir; Ptak, Andrew; Jia, Jianjun; Heckman, Timothy M.; Gandhi, Poshak; Urry, C. Megan

2014-06-01

With the recent advent of physically motivated, self-consistent X-ray models, the circumnuclear medium enshrouding AGN can now be investigated in unprecedented detail. We applied these models to 19 SDSS [OIII] 5007 Angstrom selected Type 2 AGN, where 9 are local Seyfert 2 galaxies and 10 are more luminous and distant Type 2 quasars. For the first time in a sample of AGN, we constrained both the line-of-sight and global column densities, finding that over half (11/19) are heavily obscured or Compton-thick (NH > 10^23 cm^-2). Four objects have different global from line-of-sight column densities. When correcting the observed X-ray luminosities for obscuration, the L_x/L_[OIII] ratio for these Type 2 AGN is essentially identical to the Seyfert 1 (i.e., unabsorbed AGN) value, which is consistent with both parameters cleanly probing AGN emission.

AGN feedback in action? - outflows and star formation in type 2 AGNs

NASA Astrophysics Data System (ADS)

Woo, Jong-Hak

2017-01-01

We present the statistical constraints on the ionized gas outflows and their connection to star formation, using a large sample of ~110,000 AGNs and star-forming galaxies at z < 0.3. First, we find a dramatic difference of the outflow signatures between AGNs and star-forming galaxies based on the [OIII] emission line kinematics. While the [OIII] velocity and velocity dispersion of star forming galaxies can be entirely accounted by the gravitational potential of host galaxies, AGNs clearly show non-gravitational kinematics, which is comparable to or stronger than the virial motion caused by the gravitational potential. Second, the distribution in the [OIII] velocity - velocity dispersion diagram dramatically expands toward large values with increasing AGN luminosity, implying that the outflows are AGN-driven. Third, the fraction of AGNs with a signature of outflow kinematics, steeply increases with AGN luminosity and Eddington ratio. In particular, the majority of luminous AGNs presents strong non-gravitational kinematics in the [OIII] profile. Interestingly, we find that the specific star formation of non-outflow AGNs is much lower than that of strong outflow AGNs, while the star formation rate of strong outflow AGNs is comparable to that of star forming galaxies. We interpret this trend as a delayed AGN feedback as it takes dynamical time for the outflows to suppress star formation in galactic scales.

Starburst or AGN Dominance in Submillimetre-Luminous Candidate AGN?

NASA Astrophysics Data System (ADS)

Coppin, Kristen; Pope, Alexandra; Menéndez-Delmestre, Karín; Alexander, David M.; Dunlop, James

2010-06-01

It is widely believed that ultraluminous infrared (IR) galaxies and active galactic nuclei (AGN) activity are triggered by galaxy interactions and merging, with the peak of activity occurring at z~2, where submillimetre galaxies are thousands of times more numerous than local ULIRGs. In this evolutionary picture, submillimetre galaxies (SMGs) would host an AGN, which would eventually grow a black hole (BH) strong enough to blow off all of the gas and dust leaving an optically luminous QSO. To probe this evolutionary sequence we have focussed on the `missing link' sources, which demonstrate both strong starburst (SB) and AGN signatures, in order to determine if the SB is the main power source even in SMGs when we have evidence that an AGN is present from their IRAC colours. The best way to determine if a dominant AGN is present is to look for their signatures in the mid-infrared with the Spitzer IRS, since often even deep X-ray observations miss identifying the presence of AGN in heavily dust-obscured SMGs. We present the results of our audit of the energy balance between star-formation and AGN within this special sub-population of SMGs-where the BH has grown appreciably to begin heating the dust emission.

AGN outflows and feedback twenty years on

NASA Astrophysics Data System (ADS)

Harrison, C. M.; Costa, T.; Tadhunter, C. N.; Flütsch, A.; Kakkad, D.; Perna, M.; Vietri, G.

2018-03-01

It is twenty years since the seminal works by Magorrian and co-authors and by Silk and Rees, which, along with other related work, ignited an explosion of publications connecting active galactic nucleus (AGN)-driven outflows to galaxy evolution. With a surge in observations of AGN outflows, studies are attempting to test AGN feedback models directly using the outflow properties. With a focus on outflows traced by optical and CO emission lines, we discuss significant challenges that greatly complicate this task, from both an observational and theoretical perspective. We highlight the observational uncertainties involved and the assumptions required when deriving kinetic coupling efficiencies (that is, outflow kinetic power as a fraction of AGN luminosity) from typical observations. Based on recent models we demonstrate that extreme caution should be taken when comparing observationally derived kinetic coupling efficiencies to coupling efficiencies from fiducial feedback models.

The Pearson-Readhead AGN Survey

NASA Astrophysics Data System (ADS)

Lister, M. L.

2009-08-01

The Pearson-Readhead survey of active galactic nuclei (AGN) was the first complete sample to be studied by VLBI, and was the subject of a detailed investigation by the VSOP program. We discuss the scientific findings from this unique survey, and how it has provided robust confirmation of the relativistic beaming model for AGN jets.

AGN Variability in the GOODS Fields

NASA Astrophysics Data System (ADS)

Sarajedini, Vicki

2007-07-01

Variability is a proven method to identify intrinsically faint active nuclei in galaxies found in deep HST surveys. We propose to extend our short-term variability study of the GOODS fields to include the more recent epochs obtained via supernovae searchers, increasing the overall time baseline from 6 months to 2.5 years. Based on typical AGN lightcurves, we expect to detect 70% more AGN by including these more recent epochs. Variable-detected AGN samples complement current X-ray and mid-IR surveys for AGN by providing unambigous evidence of nuclear activity. Additionallty, a significant number of variable nuclei are not associated with X-ray or mid-IR sources and would thus go undetected. With the increased time baseline, we will be able to construct the structure function {variability amplitude vs. time} for low-luminosity AGN to z 1. The inclusion of the longer time interval will allow for better descrimination among the various models describing the nature of AGN variability. The variability survey will be compared against spectroscopically selected AGN from the Team Keck Redshift Survey of the GOODS-N and the upcoming Flamingos-II NIR survey of the GOODS-S. The high-resolution ACS images will be used to separate the AGN from the host galaxy light and study the morphology, size and environment of the host galaxy. These studies will address questions concerning the nature of low-luminosity AGN evolution and variability at z 1.

Identifying Distant AGNs

NASA Astrophysics Data System (ADS)

Trouille, Laura; Barger, Amy; Tremonti, Christy

2014-07-01

The Baldwin, Phillips, and Terlevich emission-line ratio diagnostic ([OIII]/Hβ versus [NII]/Hα, hereafter BPT diagram) efficiently separates galaxies whose signal is dominated by star formation (BPT-SF) from those dominated by AGN activity (BPT-AGN). Yet the BPT diagram is limited to z<0.5, the redshift at which [NII]λ6584 leaves the optical spectral window. Using the Sloan Digital Sky Survey (SDSS), we construct a new diagnostic, or TBT diagram, that is based on rest-frame g-z color, [NeIII]λ3869, and [OII]λλ3726+3729 and can be used for galaxies out to z<1.4. The TBT diagram identifies 98.7% of the SDSS BPT-AGN as TBT-AGN and 97% of the SDSS BPT-SF as TBT-SF. Furthermore, it identifies 97% of the OPTX Chandra X-ray selected AGNs as TBT-AGN. This is in contrast to the BPT diagram, which misidentifies 20% of X-ray selected AGNs as BPT-SF.

SU(5) unification with TeV-scale leptoquarks

DOE PAGES

Cox, Peter; Kusenko, Alexander; Sumensari, Olcyr; ...

2017-03-07

It has previously been noted that SU(5) unification can be achieved via the simple addition of light scalar leptoquarks from two split 10 multiplets. We explore the parameter space of this model in detail and find that unification requires at least one leptoquark to have mass below ≈ 16 TeV. We point out that introducing splitting of the 24 allows the unification scale to be raised beyond 10 16 GeV, while a U(1) PQ symmetry can be imposed to forbid dangerous proton decay mediated by the light leptoquarks. The latest bounds from LHC searches are combined and we find thatmore » a leptoquark as light as 400 GeV is still permitted. Finally, we discuss the interesting possibility that the leptoquarks required for unification could also be responsible for the 2.6σ deviation observed in the ratio R K at LHCb.« less

AGN Variability: Probing Black Hole Accretion

NASA Astrophysics Data System (ADS)

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.

Galaxy and Mass Assembly (GAMA): active galactic nuclei in pairs of galaxies

NASA Astrophysics Data System (ADS)

Gordon, Yjan A.; Owers, Matt S.; Pimbblet, Kevin A.; Croom, Scott M.; Alpaslan, Mehmet; Baldry, Ivan K.; Brough, Sarah; Brown, Michael J. I.; Cluver, Michelle E.; Conselice, Christopher J.; Davies, Luke J. M.; Holwerda, Benne W.; Hopkins, Andrew M.; Gunawardhana, Madusha L. P.; Loveday, Jonathan; Taylor, Edward N.; Wang, Lingyu

2017-03-01

There exist conflicting observations on whether or not the environment of broad- and narrow-line active galatic nuclei (AGN) differ and this consequently questions the validity of the AGN unification model. The high spectroscopic completeness of the Galaxy and Mass Assembly (GAMA) survey makes it ideal for a comprehensive analysis of the close environment of galaxies. To exploit this, and conduct a comparative analysis of the environment of broad- and narrow-line AGN within GAMA, we use a double-Gaussian emission line fitting method to model the more complex line profiles associated with broad-line AGN. We select 209 type 1 (I.e. unobscured), 464 type 1.5-1.9 (partially obscured), and 281 type 2 (obscured) AGN within the GAMA II data base. Comparing the fractions of these with neighbouring galaxies out to a pair separation of 350 kpc h-1 and Δz < 0.012 shows no difference between AGN of different type, except at separations less than 20 kpc h-1 where our observations suggest an excess of type 2 AGN in close pairs. We analyse the properties of the galaxies neighbouring our AGN and find no significant differences in colour or the star formation activity of these galaxies. Further to this, we find that Σ5 is also consistent between broad- and narrow-line AGN. We conclude that the observations presented here are consistent with AGN unification.

SAT Encoding of Unification in EL

NASA Astrophysics Data System (ADS)

Baader, Franz; Morawska, Barbara

Unification in Description Logics has been proposed as a novel inference service that can, for example, be used to detect redundancies in ontologies. In a recent paper, we have shown that unification in EL is NP-complete, and thus of a complexity that is considerably lower than in other Description Logics of comparably restricted expressive power. In this paper, we introduce a new NP-algorithm for solving unification problems in EL, which is based on a reduction to satisfiability in propositional logic (SAT). The advantage of this new algorithm is, on the one hand, that it allows us to employ highly optimized state-of-the-art SAT solvers when implementing an EL-unification algorithm. On the other hand, this reduction provides us with a proof of the fact that EL-unification is in NP that is much simpler than the one given in our previous paper on EL-unification.

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

NASA Astrophysics Data System (ADS)

Peirani, Sébastien; Dubois, Yohan; Volonteri, Marta; Devriendt, Julien; Bundy, Kevin; Silk, Joe; Pichon, Christophe; Kaviraj, Sugata; Gavazzi, Raphaël; Habouzit, Mélanie

2017-12-01

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, HAGN, HnoAGN and HDM) significantly evolve with time. More specifically, at high redshift (z ∼ 5), the mean central density profiles of HAGN and HnoAGN dark matter haloes tend to be much steeper than their HDM counterparts owing to the rapidly growing baryonic component and ensuing adiabatic contraction. By z ∼ 1.5, these mean halo density profiles in HAGN have flattened, pummelled by powerful AGN activity ('quasar mode'): the integrated inner mass difference gaps with HnoAGN haloes have widened, and those with HDM haloes have narrowed. Fast forward 9.5 billion years, down to z = 0, and the trend reverses: HAGN halo mean density profiles drift back to a more cusped shape as AGN feedback efficiency dwindles ('radio mode'), and the gaps in integrated central mass difference with HnoAGN and HDM close and broaden, respectively. On the galaxy side, the story differs noticeably. Averaged stellar profile central densities and inner slopes are monotonically reduced by AGN activity as a function of cosmic time, resulting in better agreement with local observations.

Challenges in Finding AGNs in the Low Luminosity Regime

NASA Astrophysics Data System (ADS)

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 <10 keV are often powerful tools in uncovering optically unidentified AGNs at higher luminosities, this is not the case in the low luminosity regime. In this talk, I will review the effectiveness of uncovering AGNs in the low luminosity regime using multiwavength investigations, with a focus on infrared spectroscopic signatures.

THE PREVALENCE OF GAS OUTFLOWS IN TYPE 2 AGNs. II. 3D BICONICAL OUTFLOW MODELS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bae, Hyun-Jin; Woo, Jong-Hak, E-mail: hjbae@galaxy.yonsei.ac.kr, E-mail: woo@astro.snu.ac.kr

We present 3D models of biconical outflows combined with a thin dust plane for investigating the physical properties of the ionized gas outflows and their effect on the observed gas kinematics in type 2 active galactic nuclei (AGNs). Using a set of input parameters, we construct a number of models in 3D and calculate the spatially integrated velocity and velocity dispersion for each model. We find that three primary parameters, i.e., intrinsic velocity, bicone inclination, and the amount of dust extinction, mainly determine the simulated velocity and velocity dispersion. Velocity dispersion increases as the intrinsic velocity or the bicone inclinationmore » increases, while velocity (i.e., velocity shifts with respect to systemic velocity) increases as the amount of dust extinction increases. Simulated emission-line profiles well reproduce the observed [O iii] line profiles, e.g., narrow core and broad wing components. By comparing model grids and Monte Carlo simulations with the observed [O iii] velocity–velocity dispersion distribution of ∼39,000 type 2 AGNs, we constrain the intrinsic velocity of gas outflows ranging from ∼500 to ∼1000 km s{sup −1} for the majority of AGNs, and up to ∼1500–2000 km s{sup −1} for extreme cases. The Monte Carlo simulations show that the number ratio of AGNs with negative [O iii] velocity to AGNs with positive [O iii] velocity correlates with the outflow opening angle, suggesting that outflows with higher intrinsic velocity tend to have wider opening angles. These results demonstrate the potential of our 3D models for studying the physical properties of gas outflows, applicable to various observations, including spatially integrated and resolved gas kinematics.« less

The Swift/BAT AGN Spectroscopic Survey. IX. The Clustering Environments of an Unbiased Sample of Local AGNs

NASA Astrophysics Data System (ADS)

Powell, M. C.; Cappelluti, N.; Urry, C. M.; Koss, M.; Finoguenov, A.; Ricci, C.; Trakhtenbrot, B.; Allevato, V.; Ajello, M.; Oh, K.; Schawinski, K.; Secrest, N.

2018-05-01

We characterize the environments of local accreting supermassive black holes by measuring the clustering of AGNs in the Swift/BAT Spectroscopic Survey (BASS). With 548 AGN in the redshift range 0.01 < z < 0.1 over the full sky from the DR1 catalog, BASS provides the largest, least biased sample of local AGNs to date due to its hard X-ray selection (14–195 keV) and rich multiwavelength/ancillary data. By measuring the projected cross-correlation function between the AGN and 2MASS galaxies, and interpreting it via halo occupation distribution and subhalo-based models, we constrain the occupation statistics of the full sample, as well as in bins of absorbing column density and black hole mass. We find that AGNs tend to reside in galaxy group environments, in agreement with previous studies of AGNs throughout a large range of luminosity and redshift, and that on average they occupy their dark matter halos similar to inactive galaxies of comparable stellar mass. We also find evidence that obscured AGNs tend to reside in denser environments than unobscured AGNs, even when samples were matched in luminosity, redshift, stellar mass, and Eddington ratio. We show that this can be explained either by significantly different halo occupation distributions or statistically different host halo assembly histories. Lastly, we see that massive black holes are slightly more likely to reside in central galaxies than black holes of smaller mass.

The Lick AGN Monitoring Project 2016: Extending Reverberation Mapping to Higher Luminosity AGNs

NASA Astrophysics Data System (ADS)

U, Vivian; LAMP2016 Collaboration

2017-01-01

The technique of reverberation mapping has been used to estimate virial black hole masses and, more fundamentally, to probe the broad line region structure in Seyfert I galaxies. Efforts from the previous Lick AGN Monitoring Project (LAMP) campaigns and other studies to date have culminated in a large sample of reverberation mapped AGNs and measurements of their black hole masses, which in turn enabled major improvement to various AGN scaling relations. However, the high-luminosity end of such relations remains poorly constrained; this is because of observational challenges presented by the weaker continuum flux variations and longer time dilation in these sources. To this end, we have initiated a new LAMP2016 campaign to target AGNs with luminosities of 10^44 erg/s, with predicted H-beta lags of ~20 - 60 days or black hole masses of 10^7 - 10^8.5 Msun. Designed to monitor ~20 AGNs biweekly from Spring 2016 through Winter 2017 with the Kast spectrograph on the 3-m Shane Telescope at Lick Observatory, we aim to probe luminosity-dependent trends in broad line region structure and dynamics, improve calibrations for single-epoch estimates of high-redshift quasar black hole masses, and test photoionization models for the radially-stratified structure of the broad line region. In this talk, I will present the overview and scope of LAMP2016 and show preliminary results from our ongoing campaign.

Observational Signatures Of Agn Feedback Across Cosmic Time

NASA Astrophysics Data System (ADS)

Wylezalek, Dominika

2017-06-01

While many compelling models of AGN feedback exist, there is no clear data-driven picture of how winds are launched, how they propagate through the galaxy and what impact they have on the galactic gas. Recent work suggests that AGN luminosity plays an important role. The following described projects focus on understanding the power, reach and impact of feedback processes exerted by AGN of different power. I first describe recent efforts in our group of relating feedback signatures in powerful quasars 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. Feedback signatures seem to be best observable in gas-rich galaxies where the coupling of the AGN-driven wind to the gas is strongest, in agreement with recent simulations. But how and where does this quenching happen? Is it accomplished through the mechanical action of jets or through nuclear winds driven by radiation pressure? Finally, I show that AGN signatures and AGN-driven winds can be easily hidden and not be apparent in the integrated spectrum of a galaxy hosting a low/intermediate-luminosity AGN. Using data from the new SDSS-IV MaNGA survey, we have developed a new AGN selection algorithm tailored to IFU data and we are uncovering a much more nuanced picture of AGN activity allowing us to discover AGN signatures at large distances from the galaxy center. This implies that large IFU surveys, such as the SDSS-IV MaNGA survey, might uncover many previously unknown AGN and feedback signatures related to them. Outflows and feedback from low- and intermediate-luminosity AGN might have been underestimated in the past but can potentially significantly contribute to the AGN/host-galaxy self-regulation.

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

NASA Astrophysics Data System (ADS)

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.

Grand unification and low scale implications: D2 parity for unification and neutrino masses

NASA Astrophysics Data System (ADS)

Tavartkiladze, Zurab

2014-06-01

The Grand Unified SU(5)-SU(5)' model, augmented with D2 Parity, is considered. The latter play crucial role for phenomenology. The model has several novel properties and gives interesting phenomenological implications. The charged leptons together with right handed (or sterile) neutrinos emerge es composite states. Within considered scenario, we study the charged fermion and neutrino mass generation. Moreover, we show that the model gives successful gauge coupling unification.

Evidence for a mass-dependent AGN Eddington ratio distribution via the flat relationship between SFR and AGN luminosity

NASA Astrophysics Data System (ADS)

Bernhard, E.; Mullaney, J. R.; Aird, J.; Hickox, R. C.; Jones, M. L.; Stanley, F.; Grimmett, L. P.; Daddi, E.

2018-05-01

The lack of a strong correlation between AGN X-ray luminosity (LX; a proxy for AGN power) and the star formation rate (SFR) of their host galaxies has recently been attributed to stochastic AGN variability. Studies using population synthesis models have incorporated this by assuming a broad, universal (i.e. does not depend on the host galaxy properties) probability distribution for AGN specific X-ray luminosities (i.e. the ratio of LX to host stellar mass; a common proxy for Eddington ratio). However, recent studies have demonstrated that this universal Eddington ratio distribution fails to reproduce the observed X-ray luminosity functions beyond z ˜ 1.2. Furthermore, empirical studies have recently shown that the Eddington ratio distribution may instead depend upon host galaxy properties, such as SFR and/or stellar mass. To investigate this further, we develop a population synthesis model in which the Eddington ratio distribution is different for star-forming and quiescent host galaxies. We show that, although this model is able to reproduce the observed X-ray luminosity functions out to z ˜ 2, it fails to simultaneously reproduce the observed flat relationship between SFR and X-ray luminosity. We can solve this, however, by incorporating a mass dependency in the AGN Eddington ratio distribution for star-forming host galaxies. Overall, our models indicate that a relative suppression of low Eddington ratios (λEdd ≲ 0.1) in lower mass galaxies (M* ≲ 1010 - 11 M⊙) is required to reproduce both the observed X-ray luminosity functions and the observed flat SFR/X-ray relationship.

Star-forming Galaxies as AGN Imposters? A Theoretical Investigation of the Mid-infrared Colors of AGNs and Extreme Starbursts

NASA Astrophysics Data System (ADS)

Satyapal, Shobita; Abel, Nicholas P.; Secrest, Nathan J.

2018-05-01

We conduct for the first time a theoretical investigation of the mid-infrared spectral energy distribution (SED) produced by dust heated by an active galactic nucleus (AGN) and an extreme starburst. These models employ an integrated modeling approach using photoionization and stellar population synthesis models in which both the line and emergent continuum is predicted from gas exposed to the ionizing radiation from a young starburst and an AGN. In this work, we focus on the infrared colors from the Wide-field Infrared Survey Explorer, predicting the dependence of the colors on the input radiation field, the interstellar medium conditions, the obscuring column, and the metallicity. We find that an extreme starburst can mimic an AGN in two band mid-infrared color cuts employed in the literature. However, the three-band color cuts employed in the literature require starbursts with extremely high ionization parameters or gas densities. We show that the extreme mid-infrared colors seen in some blue compact dwarf galaxies are not due to metallicity but rather a combination of high ionization parameters and high column densities. Based on our theoretical calculations, we present a theoretical mid-infrared color cut that will exclude even the most extreme starburst that we have modeled in this work. The theoretical AGN demarcation region presented here can be used to identify elusive AGN candidates for future follow-up studies with the James Webb Space Telescope. The full suite of simulated SEDs are available online.

AGN Science with AGIS

NASA Astrophysics Data System (ADS)

Coppi, Paolo

2009-05-01

AGIS, a proposed future gamma-ray telescope consisting of a square km array of 50 atmospheric Cherenkov telescopes, will provide a powerful new view of the high energy universe. The combination of its increased sensitivity (a factor 10 over current observatories), increased survey capabilities, and a low energy threshold (<30 GeV) that allows observations at energies not subject to absorption on extragalactic background light will result in a dramatic increase in the number of AGN accessible at high energies. The overall number of ``TeV blazar" AGN, those detected by current ground-based observatories, should increase by a factor 30 or more with a corresponding increase in the number of these that can be monitored at high statistical significance to test emission models rigorously. More excitingly, AGIS may also begin to pick up entirely new classes of AGN such as radio galaxies with X-ray emitting hotspots at large distances from the central engine, providing further insight into the outflows from AGN. The low AGIS threshold energy will also allow significant source overlap with objects detected by the recently launched Fermi gamma-ray space observatory at lower, GeV energies. AGIS will significantly improve on the localization and variability monitoring of the Fermi sources it sees.

Compton Thick AGN in the COSMOS field

NASA Astrophysics Data System (ADS)

Lanzuisi, Giorgio; Cosmos Collaboration

2015-09-01

I will present the results we published in a couple of recent papers (Lanzuisi et al. 2015, A&A 573A 137, Lanzuisi et al. 2015, arXiv 1505.01153) on the properties of X-ray selected Compton Thick (CT, NH>10^24 cm^-2) AGN, in the COSMOS survey. We exploited the rich multi-wavelength dataset available in this field, to show that CT AGN tend to harbor smaller, rapidly growing SMBH with respect to unobscured AGN, and have a higher chance of being hosted by star-forming, merging and post-merger systems.We also demonstrated the detectability of even more heavily obscured AGN (NH>10^25 cm^-2), thanks to a truly multi-wavelength approach in the same field. The extreme source detected in this way shows strong evidences of ongoing powerful AGN feedback, detected as blue-shifted wings of high ionization optical emission lines such as [NeV] and [FeVII], as well as of the [OIII] emission line.The results obtained from these works point toward a scenario in which highly obscured AGN occupy a peculiar place in the galaxy-AGN co-evolution process, in which both the host and the SMBH rapidly evolve toward the local relations.We will also present estimates on the detectability of such extreme sources up to redshift ~6-7 with Athena. Combining the most up to date models for the Luminosity Function of CT AGN at high z, aggressive data analysis techniques on faint sources, and the current Athena survey design, we demonstrate that we will detect, and recognize as such, a small (few to ten) but incredibly valuable sample of CT AGN at such high redshift.

Signatures of AGN feedback

NASA Astrophysics Data System (ADS)

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)!

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ajello, M.; /KIPAC, Menlo Park; Alexander, D.M.

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-thickmore » 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.« less

Dusty Donuts: Modeling the Reverberation Response of the Circumnuclear Dusty Torus Emission in AGN

NASA Astrophysics Data System (ADS)

Almeyda, Triana R.

The obscuring circumnuclear torus of dusty molecular gas is one of the major components of AGN (active galactic nuclei), yet its size, composition, and structure are not well understood. These properties can be studied by analyzing the temporal variations of the infrared (IR) dust emission from the torus in response to variations in the AGN continuum luminosity; a technique known as reverberation mapping. In a recent international campaign 12 AGN were monitored using the Spitzer Space Telescope and several ground-based telescopes, providing a unique set of well-sampled mid-IR and optical light curves which are required in order to determine the approximate sizes of the tori in these AGN. To help extract structural information contained in the data a computer model, TORMAC, has been developed that simulates the reverberation response of the clumpy torus emission. Given an input optical light curve, the code computes the emission of a 3D ensemble of dust clouds as a function of time at selected IR wavelengths, taking into account light travel delays. A large library of torus reverberation response simulations has been constructed, to investigate the effects of various geometrical and structural properties such as inclination, cloud distribution, disk half-opening angle, and radial depth. The effects of dust cloud orientation, cloud optical depth, anisotropy of the illuminating AGN radiation field, dust cloud shadowing, and cloud occultation are also explored in detail. TORMAC was also used to generate synthetic IR light curves for the Seyfert 1 galaxy, NGC 6418, using the observed optical light curve as the input, to investigate how the torus and dust cloud properties incorporated in the code affect the results obtained from reverberation mapping. This dissertation presents the most comprehensive investigation to date showing that radiative transfer effects within the torus and anisotropic illumination of the torus can strongly influence the torus IR response at

The fraction of AGNs in major merger galaxies and its luminosity dependence

NASA Astrophysics Data System (ADS)

Weigel, Anna K.; Schawinski, Kevin; Treister, Ezequiel; Trakhtenbrot, Benny; Sanders, David B.

2018-05-01

We use a phenomenological model which connects the galaxy and active galactic nucleus (AGN) populations to investigate the process of AGNs triggering through major galaxy mergers at z ˜ 0. The model uses stellar mass functions as input and allows the prediction of AGN luminosity functions based on assumed Eddington ratio distribution functions (ERDFs). We show that the number of AGNs hosted by merger galaxies relative to the total number of AGNs increases as a function of AGN luminosity. This is due to more massive galaxies being more likely to undergo a merger and does not require the assumption that mergers lead to higher Eddington ratios than secular processes. Our qualitative analysis also shows that to match the observations, the probability of a merger galaxy hosting an AGN and accreting at a given Eddington value has to be increased by a factor ˜10 relative to the general AGN population. An additional significant increase of the fraction of high Eddington ratio AGNs among merger host galaxies leads to inconsistency with the observed X-ray luminosity function. Physically our results imply that, compared to the general galaxy population, the AGN fraction among merger galaxies is ˜10 times higher. On average, merger triggering does however not lead to significantly higher Eddington ratios.

Symmetry Breaking, Unification, and Theories Beyond the Standard Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nomura, Yasunori

2009-07-31

A model was constructed in which the supersymmetric fine-tuning problem is solved without extending the Higgs sector at the weak scale. We have demonstrated that the model can avoid all the phenomenological constraints, while avoiding excessive fine-tuning. We have also studied implications of the model on dark matter physics and collider physics. I have proposed in an extremely simple construction for models of gauge mediation. We found that the {mu} problem can be simply and elegantly solved in a class of models where the Higgs fields couple directly to the supersymmetry breaking sector. We proposed a new way of addressingmore » the flavor problem of supersymmetric theories. We have proposed a new framework of constructing theories of grand unification. We constructed a simple and elegant model of dark matter which explains excess flux of electrons/positrons. We constructed a model of dark energy in which evolving quintessence-type dark energy is naturally obtained. We studied if we can find evidence of the multiverse.« less

Disentangling AGN and Star Formation in Soft X-Rays

NASA Technical Reports Server (NTRS)

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.

Assessment of the suitability of GOCE-based geoid models for the unification of the North American vertical datums

NASA Astrophysics Data System (ADS)

Amjadiparvar, Babak; Sideris, Michael

2015-04-01

Precise gravimetric geoid heights are required when the unification of vertical datums is performed using the Geodetic Boundary Value Problem (GBVP) approach. Five generations of Global Geopotential Models (GGMs) derived from Gravity field and steady-state Ocean Circulation Explorer (GOCE) observations have been computed and released so far (available via IAG's International Centre for Global Earth Models, ICGEM, http://icgem.gfz-potsdam.de/ICGEM/). The performance of many of these models with respect to geoid determination has been studied in order to select the best performing model to be used in height datum unification in North America. More specifically, Release-3, 4 and 5 of the GOCE-based global geopotential models have been evaluated using GNSS-levelling data as independent control values. Comparisons against EGM2008 show that each successive release improves upon the previous one, with Release-5 models showing an improvement over EGM2008 in Canada and CONUS between spherical harmonic degrees 100 and 210. In Alaska and Mexico, a considerable improvement over EGM2008 was brought by the Release-5 models when used up to spherical harmonic degrees of 250 and 280, respectively. The positive impact of the Release-5 models was also felt when a gravimetric geoid was computed using the GOCE-based GGMs together with gravity and topography data in Canada. This geoid model, with appropriately modified Stokes kernel between spherical harmonic degrees 190 and 260, performed better than the official Canadian gravimetric geoid model CGG2013, thus illustrating the advantages of using the latest release GOCE-based models for vertical datum unification in North America.

BAT AGN Spectroscopic Survey. VIII. Type 1 AGN with Massive Absorbing Columns

NASA Astrophysics Data System (ADS)

Shimizu, T. Taro; Davies, Richard I.; Koss, Michael; Ricci, Claudio; Lamperti, Isabella; Oh, Kyuseok; Schawinski, Kevin; Trakhtenbrot, Benny; Burtscher, Leonard; Genzel, Reinhard; Lin, Ming-yi; Lutz, Dieter; Rosario, David; Sturm, Eckhard; Tacconi, Linda

2018-04-01

We explore the relationship between X-ray absorption and optical obscuration within the BAT AGN Spectroscopic Survey (BASS), which has been collecting and analyzing the optical and X-ray spectra for 641 hard X-ray selected (E > 14 keV) active galactic nuclei (AGNs). We use the deviation from a linear broad Hα-to-X-ray relationship as an estimate of the maximum optical obscuration toward the broad line region (BLR) and compare the A V to the hydrogen column densities ({N}{{H}}) found through systematic modeling of their X-ray spectra. We find that the inferred columns implied by A V toward the BLR are often orders of magnitude less than the columns measured toward the X-ray emitting region, indicating a small-scale origin for the X-ray absorbing gas. After removing 30% of Sy 1.9s that potentially have been misclassified due to outflows, we find that 86% (164/190) of the Type 1 population (Sy 1–1.9) are X-ray unabsorbed as expected based on a single obscuring structure. However, 14% (26/190), of which 70% (18/26) are classified as Sy 1.9, are X-ray absorbed, suggesting that the BLR itself is providing extra obscuration toward the X-ray corona. The fraction of X-ray absorbed Type 1 AGNs remains relatively constant with AGN luminosity and Eddington ratio, indicating a stable BLR covering fraction.

Gauge coupling unification and nonequilibrium thermal dark matter.

PubMed

Mambrini, Yann; Olive, Keith A; Quevillon, Jérémie; Zaldívar, Bryan

2013-06-14

We study a new mechanism for the production of dark matter in the Universe which does not rely on thermal equilibrium. Dark matter is populated from the thermal bath subsequent to inflationary reheating via a massive mediator whose mass is above the reheating scale T(RH). To this end, we consider models with an extra U(1) gauge symmetry broken at some intermediate scale (M(int) ≃ 10(10)-10(12) GeV). We show that not only does the model allow for gauge coupling unification (at a higher scale associated with grand unification) but it can provide a dark matter candidate which is a standard model singlet but charged under the extra U(1). The intermediate scale gauge boson(s) which are predicted in several E6/SO(10) constructions can be a natural mediator between dark matter and the thermal bath. We show that the dark matter abundance, while never having achieved thermal equilibrium, is fixed shortly after the reheating epoch by the relation T(RH)(3)/M(int)(4). As a consequence, we show that the unification of gauge couplings which determines M(int) also fixes the reheating temperature, which can be as high as T(RH) ≃ 10(11) GeV.

Massive Molecular Outflows and Evidence for AGN Feedback from CO Observations

DTIC Science & Technology

2013-11-13

J. Thomson Avenue, Cambridge CB3 0HE, UK e-mail: c.cicone@mrao.cam.ac.uk 2 Kavli Institute for Cosmology , University of Cambridge, Madingley Road...molecular outflow as a function of AGN luminosity. Theoretical models of AGN feed- back and cosmological simulations predict a coupling efficiency between AGN

BAT AGN Spectroscopic Survey. I. Spectral Measurements, Derived Quantities, and AGN Demographics

NASA Astrophysics Data System (ADS)

Koss, Michael; Trakhtenbrot, Benny; Ricci, Claudio; Lamperti, Isabella; Oh, Kyuseok; Berney, Simon; Schawinski, Kevin; Baloković, Mislav; Baronchelli, Linda; Crenshaw, D. Michael; Fischer, Travis; Gehrels, Neil; Harrison, Fiona; Hashimoto, Yasuhiro; Hogg, Drew; Ichikawa, Kohei; Masetti, Nicola; Mushotzky, Richard; Sartori, Lia; Stern, Daniel; Treister, Ezequiel; Ueda, Yoshihiro; Veilleux, Sylvain; Winter, Lisa

2017-11-01

We present the first catalog and data release of the Swift-BAT AGN Spectroscopic Survey. We analyze optical spectra of the majority of the detected AGNs (77%, 642/836)based on their 14-195 keV emission in the 70-month Swift-BAT all-sky catalog. This includes redshift determination, absorption and emission-line measurements, and black hole mass and accretion rate estimates for the majority of obscured and unobscured AGNs (74%, 473/642), with 340 measured for the first time. With ˜90% of sources at z< 0.2, the survey represents a significant advance in the census of hard X-ray-selected AGNs in the local universe. In this first catalog paper, we describe the spectroscopic observations and data sets, and our initial spectral analysis. The FWHMs of the emission lines show broad agreement with the X-ray obscuration (˜94%), such that Sy 1-1.8 have {N}{{H}}< {10}21.9 cm-2, and Seyfert 2 have {N}{{H}}> {10}21.9 cm-2. Seyfert 1.9, however, show a range of column densities. Compared to narrow-line AGNs in the SDSS, the X-ray-selected AGNs have a larger fraction of dusty host galaxies ({{H}}α /{{H}}β > 5), suggesting that these types of AGN are missed in optical surveys. Using the [O III] λ5007/Hβ and [N II] λ6583/Hα emission-line diagnostic, about half of the sources are classified as Seyferts; ˜15% reside in dusty galaxies that lack an Hβ detection, but for which the upper limits on line emission imply either a Seyfert or LINER, ˜ 15 % are in galaxies with weak or no emission lines despite high-quality spectra, and a few percent each are LINERS, composite galaxies, H II regions, or in known beamed AGNs.

Star Formation of Merging Disk Galaxies with AGN Feedback Effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Jongwon; Smith, Rory; Yi, Sukyoung K., E-mail: jw.park@yonsei.ac.kr

2017-08-20

Using a numerical hydrodynamics code, we perform various idealized galaxy merger simulations to study the star formation (SF) of two merging disk galaxies. Our simulations include gas accretion onto supermassive black holes and active galactic nucleus (AGN) feedback. By comparing AGN simulations with those without AGNs, we attempt to understand when the AGN feedback effect is significant. Using ∼70 simulations, we investigate SF with the AGN effect in mergers with a variety of mass ratios, inclinations, orbits, galaxy structures, and morphologies. Using these merger simulations with AGN feedback, we measure merger-driven SF using the burst efficiency parameter introduced by Coxmore » et al. We confirm previous studies which demonstrated that, in galaxy mergers, AGN suppresses SF more efficiently than in isolated galaxies. However, we also find that the effect of AGNs on SF is larger in major than in minor mergers. In minor merger simulations with different primary bulge-to-total ratios, the effect of bulge fraction on the merger-driven SF decreases due to AGN feedback. We create models of Sa-, Sb-, and Sc-type galaxies and compare their SF properties while undergoing mergers. With the current AGN prescriptions, the difference in merger-driven SF is not as pronounced as in the recent observational study of Kaviraj. We discuss the implications of this discrepancy.« less

Unification Model of Seyfert Galaxies: Are all Seyfert 2 Galaxies Created Equal?

NASA Astrophysics Data System (ADS)

Tran, H. D.

The AGN unified model proposes that Seyfert 2 (S2) galaxies are basically the same class of object as Seyfert 1 (S1) galaxies but viewed from a different direction. Direct evidence supporting this picture came from spectropolarimetric observations that showed broad, polarized permitted lines in many S2s, indicating that the broad-line region (BLR) characteristic of S1 is obscured from direct view, visible only in reflected light. Many other S2s, however, failed to show any signs of broad emission lines in their polarized flux spectra, suggesting that either the BLR could not exist, or other extranuclear factors (obscuration, starburst, geometry...) had rendered the polarization signals too weak to be detectable. Based on the analysis of a large spectropolarimetric survey of S2s from the CfA and 12 micron samples conducted at Lick, Palomar and Keck Observatories, we present evidence supporting the contention that S2s with hidden BLR (HBLRs) are intrinsically more powerful than non-HBLR S2s. The positive detection of BLR in HBLR S2s appears to be due largely to the intrinsic strength of the hidden AGN nucleus rather than the lower level of nuclear obscuration or reduced dominance of circumnuclear starburst. When the intrinsic difference between HBLR and non-HBLR S2s is taken into account, it is shown that the former share many similar large-scale characteristics with Seyfert 1 galaxies, as would be expected if the unified model is correct, while the latter do not. The incidence of HBLR is also found to have a tendency to increase with AGN strength, suggesting a temporal development of the obscuring torus opening angle. Thus, not all Seyfert 2 galaxies are intrinsically similar in nature, and we speculate that evolutionary processes may be at work.

Massive outflow properties suggest AGN fade slowly

NASA Astrophysics Data System (ADS)

Zubovas, Kastytis

2018-01-01

Massive large-scale active galactic nucleus (AGN) outflows are an important element of galaxy evolution, being a way through which the AGN can affect most of the host galaxy. However, outflows evolve on time-scales much longer than typical AGN episode durations, therefore most AGN outflows are not observed simultaneously with the AGN episode that inflated them. It is therefore remarkable that rather tight correlations between outflow properties and AGN luminosity exist. In this paper, I show that such correlations can be preserved during the fading phase of the AGN episode, provided that the AGN luminosity evolves as a power law with exponent αd ∼ 1 at late times. I also show that subsequent AGN episodes that illuminate an ongoing outflow are unlikely to produce outflow momentum or energy rates rising above the observed correlations. However, there may be many difficult-to-detect outflows with momentum and energy rates lower than expected from the current AGN luminosity. Detailed observations of AGN outflow properties might help constrain the activity histories of typical and/or individual AGN.

AGN Clustering in the BAT Sample

NASA Astrophysics Data System (ADS)

Powell, Meredith; Cappelluti, Nico; Urry, Meg; Koss, Michael; BASS Team

2018-01-01

We characterize the environments of local growing supermassive black holes by measuring the clustering of AGN in the Swift-BAT Spectroscopic Survey (BASS). With 548 AGN in the redshift range 0.01AGN to date due to its hard X-ray selection (14-195 keV). By measuring the projected cross-correlation function between the AGN and 2MASS galaxies, we constrain the halo occupation distribution (HOD) of the full sample with unprecedented sensitivity, as well as in bins of obscuration with matched luminosity distributions. In doing so, we find that AGN tend to reside in galaxy groups, agreeing with previous studies of AGN throughout a large range of luminosity and redshift. We also find evidence that obscured AGN tend to reside in denser environments than unobscured AGN.

The XMM-Newton Wide Angle Survey (XWAS): the X-ray spectrum of type-1 AGN

NASA Astrophysics Data System (ADS)

Mateos, S.; Carrera, F. J.; Page, M. J.; Watson, M. G.; Corral, A.; Tedds, J. A.; Ebrero, J.; Krumpe, M.; Schwope, A.; Ceballos, M. T.

2010-02-01

Aims: We discuss the broad band X-ray properties of one of the largest samples of X-ray selected type-1 AGN to date (487 objects in total), drawn from the XMM-Newton Wide Angle Survey (XWAS). The objects presented in this work cover 2-10 keV (rest-frame) luminosities from 1042-1045 erg s-1 and are detected up to redshift 4. We constrain the overall properties of the broad band continuum, soft excess and X-ray absorption, along with their dependence on the X-ray luminosity and redshift. We discuss the implications for models of AGN emission. Methods: We fitted the observed 0.2-12 keV broad band spectra with various models to search for X-ray absorption and soft excess. The F-test was used with a significance threshold of 99% to statistically accept the detection of additional spectral components. Results: We constrained the mean spectral index of the broad band X-ray continuum to <Γ> = 1.96 ± 0.02 with intrinsic dispersion {σ< Γ >} = 0.27-0.02+0.01. The continuum becomes harder at faint fluxes and at higher redshifts and hard (2-10 keV) luminosities. The dependence of Γ with flux is likely due to undetected absorption rather than to spectral variation. We found a strong dependence of the detection efficiency of objects on the spectral shape. We expect this effect to have an impact on the measured mean continuum shapes of sources at different redshifts and luminosities. We detected excess absorption in ⪆3% of our objects, with rest-frame column densities a few ×1022 cm-2. The apparent mismatch between the optical classification and X-ray properties of these objects is a challenge for the standard orientation-based AGN unification model. We found that the fraction of objects with detected soft excess is 36%. Using a thermal model, we constrained the soft excess mean rest-frame temperature and intrinsic dispersion to kT 100 eV and σkT 34 eV. The origin of the soft excess as thermal emission from the accretion disk or Compton scattered disk emission is ruled

Constraining AGN triggering mechanisms through the clustering analysis of active black holes

NASA Astrophysics Data System (ADS)

Gatti, M.; Shankar, F.; Bouillot, V.; Menci, N.; Lamastra, A.; Hirschmann, M.; Fiore, F.

2016-02-01

The triggering mechanisms for active galactic nuclei (AGN) are still debated. Some of the most popular ones include galaxy interactions (IT) and disc instabilities (DIs). Using an advanced semi-analytic model (SAM) of galaxy formation, coupled to accurate halo occupation distribution modelling, we investigate the imprint left by each separate triggering process on the clustering strength of AGN at small and large scales. Our main results are as follows: (I) DIs, irrespective of their exact implementation in the SAM, tend to fall short in triggering AGN activity in galaxies at the centre of haloes with Mh > 1013.5 h-1 M⊙. On the contrary, the IT scenario predicts abundance of active central galaxies that generally agrees well with observations at every halo mass. (II) The relative number of satellite AGN in DIs at intermediate-to-low luminosities is always significantly higher than in IT models, especially in groups and clusters. The low AGN satellite fraction predicted for the IT scenario might suggest that different feeding modes could simultaneously contribute to the triggering of satellite AGN. (III) Both scenarios are quite degenerate in matching large-scale clustering measurements, suggesting that the sole average bias might not be an effective observational constraint. (IV) Our analysis suggests the presence of both a mild luminosity and a more consistent redshift dependence in the AGN clustering, with AGN inhabiting progressively less massive dark matter haloes as the redshift increases. We also discuss the impact of different observational selection cuts in measuring AGN clustering, including possible discrepancies between optical and X-ray surveys.

Cosmic evolution of stellar quenching by AGN feedback: clues from the Horizon-AGN simulation

NASA Astrophysics Data System (ADS)

Beckmann, R. S.; Devriendt, J.; Slyz, A.; Peirani, S.; Richardson, M. L. A.; Dubois, Y.; Pichon, C.; Chisari, N. E.; Kaviraj, S.; Laigle, C.; Volonteri, M.

2017-11-01

The observed massive end of the galaxy stellar mass function is steeper than its predicted dark matter halo counterpart in the standard Λ cold dark matter paradigm. In this paper, we investigate the impact of active galactic nuclei (AGN) feedback on star formation in massive galaxies. We isolate the impact of AGN by comparing two simulations from the HORIZON suite, which are identical except that one also includes supermassive black holes (SMBHs) and related feedback models. This allows us to cross-identify individual galaxies between simulations and quantify the effect of AGN feedback on their properties, including stellar mass and gas outflows. We find that massive galaxies (M* ≥ 1011 M⊙) are quenched by AGN feedback to the extent that their stellar masses decrease by up to 80 per cent at z = 0. SMBHs affect their host halo through a combination of outflows that reduce their baryonic mass, particularly for galaxies in the mass range 109 M⊙ ≤ M* ≤ 1011 M⊙, and a disruption of central gas inflows, which limits in situ star formation. As a result, net gas inflows on to massive galaxies, M* ≥ 1011 M⊙, drop by up to 70 per cent. We measure a redshift evolution in the stellar mass ratio of twin galaxies with and without AGN feedback, with galaxies of a given stellar mass showing stronger signs of quenching earlier on. This evolution is driven by a progressive flattening of the MSMBH-M* relation with redshift, particularly for galaxies with M* ≤ 1010 M⊙. MSMBH/M* ratios decrease over time, as falling average gas densities in galaxies curb SMBH growth.

Neutrinos from AGN

NASA Technical Reports Server (NTRS)

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.

The WISE AGN Catalog

NASA Astrophysics Data System (ADS)

Assef, R. J.; Stern, D.; Noirot, G.; Jun, H. D.; Cutri, R. M.; Eisenhardt, P. R. M.

2018-02-01

We present two large catalogs of active galactic nucleus (AGN) candidates identified across 30,093 deg2 of extragalactic sky from the Wide-field Infrared Survey Explorer’s AllWISE Data Release. Both catalogs are selected purely using the Wide-field Infrared Survey Explorer (WISE) W1 and W2 bands. The R90 catalog consists of 4,543,530 AGN candidates with 90% reliability, while the C75 catalog consists of 20,907,127 AGN candidates with 75% completeness. These reliability and completeness figures were determined from a detailed analysis of UV- to near-IR spectral energy distributions of ∼ {10}5 sources in the 9 deg2 Boötes field. The AGN selection criteria are based on those of Assef et al. (2013) recalibrated to the AllWISE data release. We provide a detailed discussion of potential artifacts and excise portions of the sky close to the Galactic Center, Galactic Plane, nearby galaxies, and other expected contaminating sources. These catalogs are expected to enable a broad range of science, and we present a few illustrative cases. From the R90 sample, we identify 45 highly variable AGNs lacking radio counterparts in the FIRST survey. One of these sources, WISEA J142846.71+172353.1, is a changing-look quasar at z = 0.104, which has changed from having broad Hα to being a narrow-lined AGN. We characterize our catalogs by comparing them to large, wide-area AGN catalogs in the literature. We identify four ROSAT X-ray sources that are each matched to three WISE-selected AGNs in the R90 sample within 30″. Spectroscopy reveals that one of these systems, 2RXS J150158.6+691029, consists of a triplet of quasars at z = 1.133 ± 0.004, suggestive of a rich group or forming galaxy cluster.

First X-ray Statistical Tests for Clumpy-Torus Models: Constraints from RXTEmonitoring of Seyfert AGN

NASA Astrophysics Data System (ADS)

Markowitz, Alex; Krumpe, Mirko; Nikutta, R.

2016-06-01

In two papers (Markowitz, Krumpe, & Nikutta 2014, and Nikutta et al., in prep.), we derive the first X-ray statistical constraints for clumpy-torus models in Seyfert AGN by quantifying multi-timescale variability in line of-sight X-ray absorbing gas as a function of optical classification.We systematically search for discrete absorption events in the vast archive of RXTE monitoring of 55 nearby type Is and Compton-thin type IIs. We are sensitive to discrete absorption events due to clouds of full-covering, neutral/mildly ionized gas transiting the line of sight. Our results apply to both dusty and non-dusty clumpy media, and probe model parameter space complementary to that for eclipses observed with XMM-Newton, Suzaku, and Chandra.We detect twelve eclipse events in eight Seyferts, roughly tripling the number previously published from this archive. Event durations span hours to years. Most of our detected clouds are Compton-thin, and most clouds' distances from the black hole are inferred to be commensurate with the outer portions of the BLR or the inner regions of infrared-emitting dusty tori.We present the density profiles of the highest-quality eclipse events; the column density profile for an eclipsing cloud in NGC 3783 is doubly spiked, possibly indicating a cloud that is being tidallysheared. We discuss implications for cloud distributions in the context of clumpy-torus models. We calculate eclipse probabilities for orientation-dependent Type I/II unification schemes.We present constraints on cloud sizes, stability, and radial distribution. We infer that clouds' small angular sizes as seen from the SMBH imply 107 clouds required across the BLR + torus. Cloud size is roughly proportional to distance from the black hole, hinting at the formation processes (e.g., disk fragmentation). All observed clouds are sub-critical with respect to tidal disruption; self-gravity alone cannot contain them. External forces, such as magnetic fields or ambient pressure, are

The energetics of AGN radiation pressure-driven outflows

NASA Astrophysics Data System (ADS)

Ishibashi, W.; Fabian, A. C.; Maiolino, R.

2018-05-01

The increasing observational evidence of galactic outflows is considered as a sign of active galactic nucleus (AGN) feedback in action. However, the physical mechanism responsible for driving the observed outflows remains unclear, and whether it is due to momentum, energy, or radiation is still a matter of debate. The observed outflow energetics, in particular the large measured values of the momentum ratio (\\dot{p}/(L/c) ˜ 10) and energy ratio (\\dot{E}_k/L ˜ 0.05), seems to favour the energy-driving mechanism; and most observational works have focused their comparison with wind energy-driven models. Here, we show that AGN radiation pressure on dust can adequately reproduce the observed outflow energetics (mass outflow rate, momentum flux, and kinetic power), as well as the scalings with luminosity, provided that the effects of radiation trapping are properly taken into account. In particular, we predict a sublinear scaling for the mass outflow rate (\\dot{M} ∝ L^{1/2}) and a superlinear scaling for the kinetic power (\\dot{E}_k ∝ L^{3/2}), in agreement with the observational scaling relations reported in the most recent compilation of AGN outflow data. We conclude that AGN radiative feedback can account for the global outflow energetics, at least equally well as the wind energy-driving mechanism, and therefore both physical models should be considered in the interpretation of future AGN outflow observations.

Inverse Compton X-ray signature of AGN feedback

NASA Astrophysics Data System (ADS)

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.

Extracting information from AGN variability

NASA Astrophysics Data System (ADS)

Kasliwal, Vishal P.; Vogeley, Michael S.; Richards, Gordon T.

2017-09-01

Active galactic nuclei (AGNs) exhibit rapid, high-amplitude stochastic flux variations across the entire electromagnetic spectrum on time-scales ranging from hours to years. The cause of this variability is poorly understood. We present a Green's function-based 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. We analyse the light curve of the Kepler AGN Zw 229-15 and find that the observed variability behaviour can be modelled as a damped harmonic oscillator perturbed by a coloured noise process. The model power spectrum turns over on time-scale 385 d. On shorter time-scales, the log-power-spectrum slope varies between 2 and 4, explaining the behaviour noted by previous studies. We recover and identify both the 5.6 and 67 d time-scales reported by previous work using the Green's function of the Continuous-time AutoRegressive Moving Average equation rather than by directly fitting the power spectrum of the light curve. These are the time-scales on which flux perturbations grow, and on which flux perturbations decay back to the steady-state flux level, respectively. We make the software package kālī used to study light curves using our method available to the community.

Dark matter in E 6 Grand unification

NASA Astrophysics Data System (ADS)

Schwichtenberg, Jakob

2018-02-01

We discuss fermionic dark matter in non-supersymmetric E 6 Grand Unification. The fundamental representation of E 6 contains, in addition to the standard model fermions, exotic fermions and we argue that one of them is a viable, interesting dark matter candidate. Its stability is guaranteed by a discrete remnant symmetry, which is an unbroken subgroup of the E 6 gauge symmetry. We compute the symmetry breaking scales and the effect of possible threshold corrections by solving the renormalization group equations numerically after imposing gauge coupling unification. Since the Yukawa couplings of the exotic and the standard model fermions have a common origin, the mass of the dark matter particles is constrained. We find a mass range of 3 · 109 GeV ≲ m DM ≲ 1 · 1013 GeV for our E 6 dark matter candidate, which is within the reach of next-generation direct detection experiments.

A comparative study of AGN feedback algorithms

NASA Astrophysics Data System (ADS)

Wurster, J.; Thacker, R. J.

2013-05-01

Modelling active galactic nuclei (AGN) feedback in numerical simulations is both technically and theoretically challenging, with numerous approaches having been published in the literature. We present a study of five distinct approaches to modelling AGN feedback within gravitohydrodynamic simulations of major mergers of Milky Way-sized galaxies. To constrain differences to only be between AGN feedback models, all simulations start from the same initial conditions and use the same star formation algorithm. Most AGN feedback algorithms have five key aspects: the black hole accretion rate, energy feedback rate and method, particle accretion algorithm, black hole advection algorithm and black hole merger algorithm. All models follow different accretion histories, and in some cases, accretion rates differ by up to three orders of magnitude at any given time. We consider models with either thermal or kinetic feedback, with the associated energy deposited locally around the black hole. Each feedback algorithm modifies the region around the black hole to different extents, yielding gas densities and temperatures within r ˜ 200 pc that differ by up to six orders of magnitude at any given time. The particle accretion algorithms usually maintain good agreement between the total mass accreted by dot{M} dt and the total mass of gas particles removed from the simulation, although not all algorithms guarantee this to be true. The black hole advection algorithms dampen inappropriate dragging of the black holes by two-body interactions. Advecting the black hole a limited distance based upon local mass distributions has many desirably properties, such as avoiding large artificial jumps and allowing the possibility of the black hole remaining in a gas void. Lastly, two black holes instantly merge when given criteria are met, and we find a range of merger times for different criteria. This is important since the AGN feedback rate changes across the merger in a way that is dependent

Does the obscured AGN fraction really depend on luminosity?

NASA Astrophysics Data System (ADS)

Sazonov, S.; Churazov, E.; Krivonos, R.

2015-12-01

We use a sample of 151 local non-blazar active galactic nuclei (AGN) selected from the INTEGRAL all-sky hard X-ray survey to investigate if the observed declining trend of the fraction of obscured (i.e. showing X-ray absorption) AGN with increasing luminosity is mostly an intrinsic or selection effect. Using a torus-obscuration model, we demonstrate that in addition to negative bias, due to absorption in the torus, in finding obscured AGN in hard X-ray flux-limited surveys, there is also positive bias in finding unobscured AGN, due to Compton reflection in the torus. These biases can be even stronger taking into account plausible intrinsic collimation of hard X-ray emission along the axis of the obscuring torus. Given the AGN luminosity function, which steepens at high luminosities, these observational biases lead to a decreasing observed fraction of obscured AGN with increasing luminosity even if this fraction has no intrinsic luminosity dependence. We find that if the central hard X-ray source in AGN is isotropic, the intrinsic (i.e. corrected for biases) obscured AGN fraction still shows a declining trend with luminosity, although the intrinsic obscured fraction is significantly larger than the observed one: the actual fraction is larger than ˜85 per cent at L ≲ 1042.5 erg s-1 (17-60 keV), and decreases to ≲60 per cent at L ≳ 1044 erg s-1. In terms of the half-opening angle θ of an obscuring torus, this implies that θ ≲ 30° in lower luminosity AGN, and θ ≳ 45° in higher luminosity ones. If, however, the emission from the central supermassive black hole is collimated as dL/dΩ ∝ cos α, the intrinsic dependence of the obscured AGN fraction is consistent with a luminosity-independent torus half-opening angle θ ˜ 30°.

Compton Reflection in AGN with Simbol-X

NASA Astrophysics Data System (ADS)

Beckmann, V.; Courvoisier, T. J.-L.; Gehrels, N.; Lubiński, P.; Malzac, J.; Petrucci, P. O.; Shrader, C. R.; Soldi, S.

2009-05-01

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 >20 keV.

String Scale Gauge Coupling Unification with Vector-Like Exotics and Noncanonical U(1)Y Normalization

NASA Astrophysics Data System (ADS)

Barger, V.; Jiang, Jing; Langacker, Paul; Li, Tianjun

We use a new approach to study string scale gauge coupling unification systematically, allowing both the possibility of noncanonical U(1)Y normalization and the existence of vector-like particles whose quantum numbers are the same as those of the Standard Model (SM) fermions and their Hermitian conjugates and the SM adjoint particles. We first give all the independent sets (Yi) of particles that can be employed to achieve SU(3)C and SU(2)L string scale gauge coupling unification and calculate their masses. Second, for a noncanonical U(1)Y normalization, we obtain string scale SU(3)C ×SU(2)L ×U(1)Y gauge coupling unification by choosing suitable U(1)Y normalizations for each of the Yi sets. Alternatively, for the canonical U(1)Y normalization, we achieve string scale gauge coupling unification by considering suitable combinations of the Yi sets or by introducing additional independent sets (Zi), that do not affect the SU(3)C ×SU(2)L unification at tree level, and then choosing suitable combinations, one from the Yi sets and one from the Zi sets. We also briefly discuss string scale gauge coupling unification in models with higher Kac-Moody levels for SU(2)L or SU(3)C.

Longterm AGN variability in the BASS sample

NASA Astrophysics Data System (ADS)

Sartori, Lia; Schawinski, Kevin; Koss, Michael; Treister, Ezequiel

2018-01-01

The study of AGN variability on different timescales can provide important information about black hole accretion physics, as well as the black hole – host galaxy interaction and coevolution. Galaxies with extended AGN photoionised clouds, e.g. IC 2497 and “Hanny’s Voorwerp”, are a great laboratory to study AGN variability over 100 kyr timescales, especially in the case where the AGN is currently dropping in luminosity. Based on a large sample of optically elusive AGN in the BASS sample we suggest that AGN may ‘flicker’ on and off 100-1000 times on ~10^5 yr timescales, and that optically elusive AGN may provide information about the switching on phase. In this talk I will show how longslit and IFU observations of BASS sources, combined with high quality hard X-ray observations and black hole demographic information, can help constraining the AGN lifecycle, and ultimately what is the physics driving AGN variability.

Vector-like quarks and leptons, SU(5) ⊗ SU(5) grand unification, and proton decay

NASA Astrophysics Data System (ADS)

Lee, Chang-Hun; Mohapatra, Rabindra N.

2017-02-01

SU(5) ⊗ SU(5) provides a minimal grand unification scheme for fermions and gauge forces if there are vector-like quarks and leptons in nature. We explore the gauge coupling unification in a non-supersymmetric model of this type, and study its implications for proton decay. The properties of vector-like quarks and intermediate scales that emerge from coupling unification play a central role in suppressing proton decay. We find that in this model, the familiar decay mode p → e +π0 may have a partial lifetime within the reach of currently planned experiments.

Self-consistent two-phase AGN torus models⋆. SED library for observers

NASA Astrophysics Data System (ADS)

Siebenmorgen, Ralf; Heymann, Frank; Efstathiou, Andreas

2015-11-01

We assume that dust near active galactic nuclei (AGNs) is distributed in a torus-like geometry, which can be described as a clumpy medium or a homogeneous disk, or as a combination of the two (i.e. a two-phase medium). The dust particles considered are fluffy and have higher submillimeter emissivities than grains in the diffuse interstellar medium. The dust-photon interaction is treated in a fully self-consistent three-dimensional radiative transfer code. We provide an AGN library of spectral energy distributions (SEDs). Its purpose is to quickly obtain estimates of the basic parameters of the AGNs, such as the intrinsic luminosity of the central source, the viewing angle, the inner radius, the volume filling factor and optical depth of the clouds, and the optical depth of the disk midplane, and to predict the flux at yet unobserved wavelengths. The procedure is simple and consists of finding an element in the library that matches the observations. We discuss the general properties of the models and in particular the 10 μm silicate band. The AGN library accounts well for the observed scatter of the feature strengths and wavelengths of the peak emission. AGN extinction curves are discussed and we find that there is no direct one-to-one link between the observed extinction and the wavelength dependence of the dust cross sections. We show that objects in the library cover the observed range of mid-infrared colors of known AGNs. The validity of the approach is demonstrated by matching the SEDs of a number of representative objects: Four Seyferts and two quasars for which we present new Herschel photometry, two radio galaxies, and one hyperluminous infrared galaxy. Strikingly, for the five luminous objects we find that pure AGN models fit the SED without needing to postulate starburst activity. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.The SED

The BAT AGN Spectroscopic Survey (BASS)

NASA Astrophysics Data System (ADS)

Koss, Michael

2017-08-01

We present the Swift BAT AGN Spectroscopic Survey (BASS) and discus the first four papers. The catalog represents an unprecedented census of hard-X-ray selected AGN in the local universe, with ~90% of sources at z<0.2. Starting from an all-sky catalog of AGN detected based on their 14-195 keV flux from the 70-month Swift/BAT catalog, we analyze a total of 1279 optical spectra, taken from twelve different telescopes, for a total of 642 spectra of unique AGN. We present the absorption and emission line measurements as well as black hole masses and accretion rates for the majority of obscured and un-obscured AGN (473), representing more than a factor of 10 increase from past studies. Consistent with previous surveys, we find an increase in the fraction of un-obscured (type 1) AGN, as measured from broad Hbeta and Halpha, with increasing 14-195 keV and 2-10 keV luminosity. We find the FWHM of the emission lines to show broad agreement with the X-ray obscuration measurements. Compared to narrow line AGN in the SDSS, the X-ray selected AGN in our sample with emission lines have a larger fraction of dustier galaxies suggesting these types of galaxies are missed in optical AGN surveys using emission line diagnostics.

Heavily Obscured AGN with SIMBOL-X

NASA Astrophysics Data System (ADS)

Della Ceca, R.; Caccianiga, A.; Severgnini, P.

2009-05-01

By comparing an optically selected sample of narrow lines AGN with an X-ray selected sample of AGN we have recently derived an estimate of the intrinsic (i.e. before absorption) 2-10 keV luminosity function (XLF) of Compton Thick AGNs. We will use this XLF to derive the number of Compton Thick AGN that will be found in the SIMBOL-X survey(s).

Compton thick AGN: the hunt continues

NASA Astrophysics Data System (ADS)

Marchesi, Stefano

2017-09-01

The X-ray spectral analysis of Compton thick (CT-) active galactic nuclei (AGN) represents a fundamental step to understand the physics of the obscuring material surrounding the accreting supermassive black hole. However, at the present day CT-AGN remain extremely hard to detect. After a first, successful pilot program, we propose to target with a 10 ks Chandra observation 4 low redshift candidate CT-AGN from the Swift-BAT 100-month catalog. This analysis will refine our knowledge of the selection function of CT-AGN, therefore helping us in determine the true intrinsic fraction of CT-AGN and their contribution to the CXB.

Fast Ionized X-ray Absorbers in AGNs

NASA Astrophysics Data System (ADS)

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

2015-07-01

We present a study of X-ray ionization of MHD accretion-disk wind models in an effort to explain the highly-ionized ultra-fast outflows (UFOs) identified as X-ray absorbers recently detected in various sub-classes of Seyfert AGNs. Our primary focus is to show that magnetically-driven outflows are physically plausible candidates to account for the AGN X-ray spectroscopic observations. We calculate its X-ray ionization and the ensuing X-ray absorption line spectra in comparison with an XXM-Newton/EPIC spectrum of the narrow-line Seyfert AGN, PG 1211+143. We find, through identifying the detected features with Fe Kα transitions, that the absorber has a characteristic ionization parameter of log(xi[erg cm/s]) = 5-6 and a hydrogen-equivalent column density on the order of 1e23 cm-2, outflowing at a sub-relativistic velocity of v/c = 0.1-0.2. The best-fit model favors its radial location at R = 200 Rs (Rs is the Schwarzschild radius), with a disk inner truncation radius at Rt = 30Rs. The overall K-shell feature in data is suggested to be dominated by Fe XXV with very little contribution from Fe XXVI and weakly-ionized iron, which is in a good agreement with a series of earlier analysis of the UFOs in various AGNs including PG 1211+143.

Results from the ESA-funded project 'Height System Unification with GOCE'

NASA Astrophysics Data System (ADS)

Sideris, M. G.; Rangelova, E. V.; Gruber, T.; Rummel, R. F.; Woodworth, P. L.; Hughes, C. W.; Ihde, J.; Liebsch, G.; Schäfer, U.; Rülke, A.; Gerlach, C.; Haagmans, R.

2013-12-01

The paper summarizes the main results of a project, supported by the European Space Agency, whose main goal is to identify the impact of GOCE gravity field models on height system unification. In particular, the Technical University Munich, the University of Calgary and the National Oceanography Centre in Liverpool, together with the Bavarian Academy of Sciences, the Federal German Agency for Cartography and Geodesy, and the Geodetic Surveys of Canada, USA and Mexico, have investigated the role of GOCE-derived gravity and geoid models for regional and global height datum connection. GOCE provides three important components of height unification: highly accurate potential differences (geopotential numbers), a global geoid- or quasi-geoid-based reference surface for elevations that is independent of inaccuracies and inconsistencies of local and regional data, and a consistent way to refer to the same datum all the relevant gravimetric, topographic and oceanographic data. We introduce briefly the methodology that has been applied in order to unify height system in North America, North Atlantic Ocean and Europe, and present results obtained using the available GOCE-derived satellite-only geopotential models, and their combination with terrestrial data and ocean models. The effects of various factors, such as data noise, omission errors, indirect bias terms, ocean models and temporal variations, on height datum unification are also presented, highlighting their magnitude and importance in the estimation of offsets between vertical datums. Based on the experiences gained in this project, a general roadmap has been developed for height datum unification in regions with good, as well as poor, coverage in gravity and geodetic height and tide gauge control stations.

The BAT AGN Spectroscopic Survey (BASS)

NASA Astrophysics Data System (ADS)

Koss, Michael; Trakhtenbrot, Benny; Ricci, Claudio; Lamperti, Isabella; Oh, Kyuseok; Berney, Simon; Schawinski, Kevin; Balokovic, Mislav; Baronchelli, Linda; Gehrels, Neil; Stern, Daniel; Mushotzky, Richard; Veilleux, Sylvain; Ueda, Yoshihiro; Crenshaw, D. Michael; Harrison, Fiona; Fischer, Travis C.; Treister, Ezequiel; BASS Team; Swift BAT Team

2017-01-01

We present the Swift BAT AGN Spectroscopic Survey (BASS) and discus the first four papers. The catalog represents an unprecedented census of hard-X-ray selected AGN in the local universe, with ~90% of sources at z<0.2. Starting from an all-sky catalog of AGN detected based on their 14-195 keV flux from the 70-month Swift/BAT catalog, we analyze a total of 1279 optical spectra, taken from twelve dierent telescopes, for a total of 642 spectra of unique AGN. We present the absorption and emission line measurements as well as black hole masses and accretion rates for the majority of obscured and un-obscured AGN (473), representing more than a factor of 10 increase from past studies. Consistent with previous surveys, we find an increase in the fraction of un-obscured (type 1) AGN, as measured from broad Hbeta and Halpha, with increasing 14-195 keV and 2-10 keV luminosity. We find the FWHM of the emission lines to show broad agreement with the X-ray obscuration measurements. Compared to narrow line AGN in the SDSS, the X-ray selected AGN in our sample with emission lines have a larger fraction of dustier galaxies suggesting these types of galaxies are missed in optical AGN surveys using emission line diagnostics. Additionally, we discuss follow-on efforts to study the variation of [OIII] to Xray measurements, a new method to measure accretion rates from using line ratios, a sample of 100 AGN observed with NIR spectroscopy, and an effort to measure the accretion rates and obscuration with merger stage in a subsample of mergers.

The joint fit of the BHMF and ERDF for the BAT AGN Sample

NASA Astrophysics Data System (ADS)

Weigel, Anna K.; Koss, Michael; Ricci, Claudio; Trakhtenbrot, Benny; Oh, Kyuseok; Schawinski, Kevin; Lamperti, Isabella

2018-01-01

A natural product of an AGN survey is the AGN luminosity function. This statistical measure describes the distribution of directly measurable AGN luminosities. Intrinsically, the shape of the luminosity function depends on the distribution of black hole masses and Eddington ratios. To constrain these fundamental AGN properties, the luminosity function thus has to be disentangled into the black hole mass and Eddington ratio distribution function. The BASS survey is unique as it allows such a joint fit for a large number of local AGN, is unbiased in terms of obscuration in the X-rays and provides black hole masses for type-1 and type-2 AGN. The black hole mass function at z ~ 0 represents an essential baseline for simulations and black hole growth models. The normalization of the Eddington ratio distribution function directly constrains the AGN fraction. Together, the BASS AGN luminosity, black hole mass and Eddington ratio distribution functions thus provide a complete picture of the local black hole population.

Compton thick AGN in Chandra sureys

NASA Astrophysics Data System (ADS)

Brightman, Murray; Nandra, Kirpal

2014-07-01

We present the results from the X-ray spectral analysis of active galactic nuclei (AGN) in the Chandra Deep Field-South, AEGIS-XD and Chandra-COSMOS surveys, focussing on the identification and characterisation of the most heavily obscured, Compton thick (CT, N H > 104 cm-2) sources. Our sample is comprised of 3088 X-ray selected sources, which has a high rate of redshift completeness (97%). The aim is to produce the largest and cleanest uniform sample of these sources from the data as possible. We identify these sources through X-ray spectral fitting, utilising torus spectral models designed for heavily obscured AGN which self consistently include the spectral signatures of heavy absorption, being Compton scattering, photoelectric absorption and iron Kα fluorescence. We identify a total of 163 CT AGN covering an intrinsic 2-10 keV X-ray luminosity range of 102 -3 × 105 erg s-1 and from z = 0.1-7.

Precision cosmology from X-ray AGN clustering

NASA Astrophysics Data System (ADS)

Basilakos, Spyros; Plionis, Manolis

2009-11-01

We place tight constraints on the main cosmological parameters of spatially flat cosmological models by using the recent angular clustering results of XMM-Newton soft (0.5-2keV) X-ray sources, which have a redshift distribution with a median of z ~ 1. Performing a standard likelihood procedure, assuming a constant in comoving coordinates active galactic nuclei (AGN) clustering evolution, the AGN bias evolution model of Basilakos, Plionis & Ragone-Figueroa and the Wilkinson Microwave Anisotropy Probe5 value of σ8, we find stringent simultaneous constraints in the (Ωm, w) plane, with Ωm = 0.26 +/- 0.05, w = -0.93+0.11-0.19.

The BAT AGN Spectroscopic Survey (BASS) DR1-Spectral Measurements, Derived Quantities, and AGN Demographics

NASA Astrophysics Data System (ADS)

Koss, Michael; BASS Team

2018-01-01

We present the first catalog and data release of the Swift-BAT AGN Spectroscopic Survey (BASS). We analyze optical spectra of the majority of AGN (77%, 641/836) detected based on their 14-195 keV emission in the 70-month Swift BAT all-sky catalog. This includes redshift determination, absorption and emission line measurements, and black hole mass and accretion rate estimates for the majority of obscured and un-obscured AGN (74%, 473/641) with 340 measured for the first time. With ~90% of sources at z<0.2, the survey represents a significant census of hard-X-ray selected AGN in the local universe. In this first catalog paper, we describe the spectroscopic observations and datasets, and our initial spectral analysis. The FWHM of the emission lines show broad agreement with the X-ray obscuration (~94%), such that Sy 1-1.8 have NH<10^21.9 cm^-2, and Seyfert 2, have NH>10^21.9 cm^-2. Seyfert 1.9 show a range of column densities. Compared to narrow line AGN in the SDSS, the X-ray selected AGN have a larger fraction of dusty host galaxies suggesting these types of AGN are missed in optical surveys. Using the most sensitive [OIII]/Hbeta and [NII]/Halpha emission line diagnostic, about half of the sources are classified as Seyferts, ~15% reside in dusty galaxies that lack an Hbeta detection, but for which the line upper limits imply either a Seyfert or LINER, ~15% are in galaxies with weak or no emission lines despite high quality spectra, and a few percent each are LINERS, composite galaxies, HII regions, or in known beamed AGN.

Flickering AGN can explain the strong circumgalactic O VI observed by COS-Halos

NASA Astrophysics Data System (ADS)

Oppenheimer, Benjamin D.; Segers, Marijke; Schaye, Joop; Richings, Alexander J.; Crain, Robert A.

2018-03-01

Proximity zone fossils (PZFs) are ionization signatures around recently active galactic nuclei (AGNs) where metal species in the circumgalactic medium remain overionized after the AGNs have shut off due to their long recombination time scales. We explore cosmological zoom hydrodynamic simulations, using the EAGLE (Evolution and Assembly of GaLaxies and their Environments) model paired with a non-equilibrium ionization and cooling module including time-variable AGN radiation to model PZFs around star-forming disc galaxies in the z ˜ 0.2 Universe. Previous simulations typically underestimated the O VI content of galactic haloes, but we show that plausible PZF models increase O VI column densities by 2 - 3 × to achieve the levels observed around COS-Halos star-forming galaxies out to 150 kpc. Models with AGN bolometric luminosities ≳ 1043.6erg s- 1, duty cycle fractions ≲ 10 per cent, and AGN lifetimes ≲ 106 yr are the most promising, because their supermassive black holes grow at the cosmologically expected rate and they mostly appear as inactive AGN, consistent with COS-Halos. The central requirement is that the typical star-forming galaxy hosted an active AGN within a time-scale comparable to the recombination time of a high metal ion, which for circumgalactic O VI is ≈107 yr. H I, by contrast, returns to equilibrium much more rapidly due to its low neutral fraction and does not show a significant PZF effect. O VI absorption features originating from PZFs appear narrow, indicating photoionization, and are often well aligned with lower metal ion species. PZFs are highly likely to affect the physical interpretation of circumgalactic high ionization metal lines if, as expected, normal galaxies host flickering AGN.

Intermediate mass black holes in AGN discs - I. Production and growth

NASA Astrophysics Data System (ADS)

McKernan, B.; Ford, K. E. S.; Lyra, W.; Perets, H. B.

2012-09-01

Here we propose a mechanism for efficiently growing intermediate mass black holes (IMBH) in discs around supermassive black holes. Stellar mass objects can efficiently agglomerate when facilitated by the gas disc. Stars, compact objects and binaries can migrate, accrete and merge within discs around supermassive black holes. While dynamical heating by cusp stars excites the velocity dispersion of nuclear cluster objects (NCOs) in the disc, gas in the disc damps NCO orbits. If gas damping dominates, NCOs remain in the disc with circularized orbits and large collision cross-sections. IMBH seeds can grow extremely rapidly by collisions with disc NCOs at low relative velocities, allowing for super-Eddington growth rates. Once an IMBH seed has cleared out its feeding zone of disc NCOs, growth of IMBH seeds can become dominated by gas accretion from the active galactic nucleus (AGN) disc. However, the IMBH can migrate in the disc and expand its feeding zone, permitting a super-Eddington accretion rate to continue. Growth of IMBH seeds via NCO collisions is enhanced by a pile-up of migrators. We highlight the remarkable parallel between the growth of IMBH in AGN discs with models of giant planet growth in protoplanetary discs. If an IMBH becomes massive enough it can open a gap in the AGN disc. IMBH migration in AGN discs may stall, allowing them to survive the end of the AGN phase and remain in galactic nuclei. Our proposed mechanisms should be more efficient at growing IMBH in AGN discs than the standard model of IMBH growth in stellar clusters. Dynamical heating of disc NCOs by cusp stars is transferred to the gas in an AGN disc helping to maintain the outer disc against gravitational instability. Model predictions, observational constraints and implications are discussed in a companion paper (Paper II).

The 5-10 keV AGN luminosity function at 0.01 < z < 4.0

NASA Astrophysics Data System (ADS)

Fotopoulou, S.; Buchner, J.; Georgantopoulos, I.; Hasinger, G.; Salvato, M.; Georgakakis, A.; Cappelluti, N.; Ranalli, P.; Hsu, L. T.; Brusa, M.; Comastri, A.; Miyaji, T.; Nandra, K.; Aird, J.; Paltani, S.

2016-03-01

The active galactic nuclei (AGN) X-ray luminosity function traces actively accreting supermassive black holes and is essential for the study of the properties of the AGN population, black hole evolution, and galaxy-black hole coevolution. Up to now, the AGN luminosity function has been estimated several times in soft (0.5-2 keV) and hard X-rays (2-10 keV). AGN selection in these energy ranges often suffers from identification and redshift incompleteness and, at the same time, photoelectric absorption can obscure a significant amount of the X-ray radiation. We estimate the evolution of the luminosity function in the 5-10 keV band, where we effectively avoid the absorbed part of the spectrum, rendering absorption corrections unnecessary up to NH ~ 1023 cm-2. Our dataset is a compilation of six wide, and deep fields: MAXI, HBSS, XMM-COSMOS, Lockman Hole, XMM-CDFS, AEGIS-XD, Chandra-COSMOS, and Chandra-CDFS. This extensive sample of ~1110 AGN (0.01 < z < 4.0, 41 < log Lx < 46) is 98% redshift complete with 68% spectroscopic redshifts. For sources lacking a spectroscopic redshift estimation we use the probability distribution function of photometric redshift estimation specifically tuned for AGN, and a flat probability distribution function for sources with no redshift information. We use Bayesian analysis to select the best parametric model from simple pure luminosity and pure density evolution to more complicated luminosity and density evolution and luminosity-dependent density evolution (LDDE). We estimate the model parameters that describe best our dataset separately for each survey and for the combined sample. We show that, according to Bayesian model selection, the preferred model for our dataset is the LDDE. Our estimation of the AGN luminosity function does not require any assumption on the AGN absorption and is in good agreement with previous works in the 2-10 keV energy band based on X-ray hardness ratios to model the absorption in AGN up to redshift three

Remnant radio-loud AGN in the Herschel-ATLAS field

NASA Astrophysics Data System (ADS)

Mahatma, V. H.; Hardcastle, M. J.; Williams, W. L.; Brienza, M.; Brüggen, M.; Croston, J. H.; Gurkan, G.; Harwood, J. J.; Kunert-Bajraszewska, M.; Morganti, R.; Röttgering, H. J. A.; Shimwell, T. W.; Tasse, C.

2018-04-01

Only a small fraction of observed active galactic nuclei (AGN) display large-scale radio emission associated with jets, yet these radio-loud AGN have become increasingly important in models of galaxy evolution. In determining the dynamics and energetics of the radio sources over cosmic time, a key question concerns what happens when their jets switch off. The resulting `remnant' radio-loud AGN have been surprisingly evasive in past radio surveys, and therefore statistical information on the population of radio-loud AGN in their dying phase is limited. In this paper, with the recent developments of Low-Frequency Array (LOFAR) and the Very Large Array, we are able to provide a systematically selected sample of remnant radio-loud AGN in the Herschel-ATLAS field. Using a simple core-detection method, we constrain the upper limit on the fraction of remnants in our radio-loud AGN sample to 9 per cent, implying that the extended lobe emission fades rapidly once the core/jets turn off. We also find that our remnant sample has a wide range of spectral indices (-1.5≤slant α ^{1400}_{150}≤slant -0.5), confirming that the lobes of some remnants may possess flat spectra at low frequencies just as active sources do. We suggest that, even with the unprecedented sensitivity of LOFAR, our sample may still only contain the youngest of the remnant population.

Unification and mechanistic detail as drivers of model construction: models of networks in economics and sociology.

PubMed

Kuorikoski, Jaakko; Marchionni, Caterina

2014-12-01

We examine the diversity of strategies of modelling networks in (micro) economics and (analytical) sociology. Field-specific conceptions of what explaining (with) networks amounts to or systematic preference for certain kinds of explanatory factors are not sufficient to account for differences in modelling methodologies. We argue that network models in both sociology and economics are abstract models of network mechanisms and that differences in their modelling strategies derive to a large extent from field-specific conceptions of the way in which a good model should be a general one. Whereas the economics models aim at unification, the sociological models aim at a set of mechanism schemas that are extrapolatable to the extent that the underlying psychological mechanisms are general. These conceptions of generality induce specific biases in mechanistic explanation and are related to different views of when knowledge from different fields should be seen as relevant.

Hard X-ray spectral properties of distant AGN in the NuSTAR surveys

NASA Astrophysics Data System (ADS)

Del Moro, Agnese

2016-08-01

I will present a study on the average broad X-ray band (~0.5-30 keV) spectral properties of the NuSTAR sources detected in the ECDF-S, EGS and COSMOS fields. Constructing the rest-frame composite spectra of AGN in different hydrogen column density (NH) and 10-40 keV luminosity bins, using Chandra and NuSTAR data, we investigate the typical spectral parameters of the AGN population, such as the photon index, NH, strength of the iron emission line (~6.4 keV) and of the Compton reflection at ~20-30 keV. Placing constraints on the reflection fraction (R) is of particular importance for the synthesis models of the cosmic X-ray background (CXB), as this parameter is strongly linked with the fraction of Compton-thick AGN needed to fit the CXB spectrum. Thanks to its sensitivity at ~20-30 keV, NuSTAR allows for the first time, to directly place such constraints for non-local AGN. We find typical reflection fractions of R~1-1.5, consistent the AGN in the local Universe, with a tentative evidence for the most obscured AGN to have, on average, stronger Compton reflection compared to unobscured AGN. Moreover, contrary to previous works, we do not find significant evidence for a decrease of the reflection strength with luminosity for typical Γ=1.8-1.9. Our results support CXB models that require a relatively small fraction of CT AGN, of the order of ~10-15%.

BAT AGN Spectroscopic Survey. V. X-Ray Properties of the Swift/BAT 70-month AGN Catalog

NASA Astrophysics Data System (ADS)

Ricci, C.; Trakhtenbrot, B.; Koss, M. J.; Ueda, Y.; Del Vecchio, I.; Treister, E.; Schawinski, K.; Paltani, S.; Oh, K.; Lamperti, I.; Berney, S.; Gandhi, P.; Ichikawa, K.; Bauer, F. E.; Ho, L. C.; Asmus, D.; Beckmann, V.; Soldi, S.; Baloković, M.; Gehrels, N.; Markwardt, C. B.

2017-12-01

Hard X-ray (≥10 keV) observations of active galactic nuclei (AGNs) can shed light on some of the most obscured episodes of accretion onto supermassive black holes. The 70-month Swift/BAT all-sky survey, which probes the 14-195 keV energy range, has currently detected 838 AGNs. We report here on the broadband X-ray (0.3-150 keV) characteristics of these AGNs, obtained by combining XMM-Newton, Swift/XRT, ASCA, Chandra, and Suzaku observations in the soft X-ray band (≤slant 10 keV) with 70-month averaged Swift/BAT data. The nonblazar AGNs of our sample are almost equally divided into unobscured ({N}{{H}}< {10}22 {{cm}}-2) and obscured ({N}{{H}}≥slant {10}22 {{cm}}-2) AGNs, and their Swift/BAT continuum is systematically steeper than the 0.3-10 keV emission, which suggests that the presence of a high-energy cutoff is almost ubiquitous. We discuss the main X-ray spectral parameters obtained, such as the photon index, the reflection parameter, the energy of the cutoff, neutral and ionized absorbers, and the soft excess for both obscured and unobscured AGNs.

The many routes to AGN feedback

NASA Astrophysics Data System (ADS)

Morganti, Raffaella

2017-11-01

The energy released by Active Galactic Nuclei (AGN) in the form of radiation, winds or radio plasma jets, is known to impact on the surrounding interstellar medium. The result of these processes, known as AGN (negative) feedback, is suggested to prevent gas, in and around galaxies, from cooling, and to remove, or at least redistribute, gas by driving massive and fast outflows, hence playing a key role in galaxy evolution. Given its importance, a large effort is devoted by the astronomical community to trace the effects of AGN on the surrounding gaseous medium and to quantify their impact for different types of AGN. This review briefly summarizes some of the recent observational results obtained in different wavebands, tracing different phases of the gas. I also summarise new insights they have brought, and the constraints they provide to numerical simulations of galaxy formation and evolution. The recent addition of deep observations of cold gas and, in particular, of cold molecular gas, has brought some interesting surprises and has expanded our understanding of AGN and AGN feedback.

Studying AGN Activation in Galaxy Mergers

NASA Astrophysics Data System (ADS)

Negus, James; Blecha, Laura

2018-06-01

Simulations predict that galaxy mergers drive central gas inflows that result in a peak AGN fraction when the two galaxy bulges reach separations near 1 kpc. Moreover, observations have shown that the AGN fraction increases as the separation between two merging galaxies decreases from 100 kpc to 10 kpc; however, the trend has not yet been measured in the pivotal sub 10 kpc regime, where activity may drastically increase as the simulations suggest. We present a uniform sample of dual and offset AGN, which features AGN parameters (e.g., redshift, angular separation) and normalized cosmology-dependent parameters (e.g., physical separation, bolometric luminosity), using multi-wavelength observations (IR to X-ray) in this critical sub 10 kpc range. In addition, using galaxy merger simulations with GADGET-3, a smoothed particle hydrodynamics N-body code, we report how much time galaxy pairs spend at different separations during a merger. Using these results, we will discuss how galaxy bulge separation correlates to increases in the AGN fraction over varying timescales, and where AGN are primarily fueled during mergers with galaxy bulge separations < 10 kpc.

Toward a New Paradigm for the Unification of Radio Loud AGN and its Connection to Accretion

NASA Technical Reports Server (NTRS)

Georganpoulos, Markos; Meyer, Eileen T.; Fossati, Giovanni; Lister, Matthew L.

2012-01-01

We recently argued [21J that the collective properties. of radio loud active galactic nuclei point to the existence of two families of sources, one of powerful sources with single velocity jets and one of weaker jets with significant velocity gradients in the radiating plasma. These families also correspond to different accretion modes and therefore different thermal and emission line intrinsic properties: powerful sources have radiatively efficient accretion disks, while in weak sources accretion must be radiatively inefficient. Here, after we briefly review of our recent work, we present the following findings that support our unification scheme: (i) along the broken sequence of aligned objects, the jet kinetic power increases. (ii) in the powerful branch of the sequence of aligned objects the fraction of BLLs decreases with increasing jet power. (iii) for powerful sources, the fraction of BLLs increases for more un-aligned objects, as measured by the core to extended radio emission. Our results are also compatible with the possibility that a given accretion power produces jets of comparable kinetic power.

Compton-thick AGN at high and low redshift

NASA Astrophysics Data System (ADS)

Akylas, A.; Georgantopoulos, I.; Corral, A.; Ranalli, P.; Lanzuisi, G.

2017-10-01

The most obscured sources detected in X-ray surveys, the Compton-thick AGN present great interest both because they represent the hidden side of accretion but also because they may signal the AGN birth. We analyse the NUSTAR observations from the serendipitous observations in order to study the Compton-thick AGN at the deepest possible ultra-hard band (>10 keV). We compare our results with our SWIFT/BAT findings in the local Universe, as well as with our results in the CDFS and COSMOS fields. We discuss the comparison with X-ray background synthesis models finding that a low fraction of Compton-thick sources (about 15 per cent of the obscured population) is compatible with both the 2-10keV band results and those at harder energies.

The environmental properties of radio-emitting AGN

NASA Astrophysics Data System (ADS)

Magliocchetti, M.; Popesso, P.; Brusa, M.; Salvato, M.

2018-05-01

We study the environmental properties of z≲ 1.2 radio-selected AGN belonging to the ˜2 deg2 of the COSMOS field, finding that about 20% of them appear within overdense structures. AGN with P_{1.4 GHz}>10^{23.5} W Hz^{-1} sr^{-1} are twice more likely to be found in clusters with respect to fainter sources (˜38% vs ˜15%), just as radio-selected AGN with stellar masses M* > 1011M⊙ are twice more likely to be found in overdense environments with respect to objects of lower mass (˜24% vs ˜11%). Comparisons with galaxy samples further suggest that radio-selected AGN of large stellar mass tend to avoid underdense environments more than normal galaxies with the same stellar content. Stellar masses also seem to determine the location of radio-active AGN within clusters: ˜100% of the sources found as satellite galaxies have M* < 1011.3M⊙, while ˜100% of the AGN coinciding with a cluster central galaxy have M* > 1011M⊙. No different location within the cluster is instead observed for AGN of various radio luminosities. Radio AGN which also emit in the MIR show a marked preference to be found as isolated galaxies (˜70%) at variance with those also active in the X-ray which all seem to reside within overdensities. What emerges from our work is a scenario whereby physical processes on sub-pc and kpc scales (e.g. emission respectively related to the AGN and to star formation) are strongly interconnected with the large-scale environment of the AGN itself.

Deep ALMA photometry of distant X-ray AGN: improvements in star formation rate constraints, and AGN identification

NASA Astrophysics Data System (ADS)

Stanley, F.; Harrison, C. M.; Alexander, D. M.; Simpson, J.; Knudsen, K. K.; Mullaney, J. R.; Rosario, D. J.; Scholtz, J.

2018-05-01

We present the star formation rates (SFRs) of a sample of 109 galaxies with X-ray selected active galactic nuclei (AGN) with moderate to high X-ray luminosities (\\mathrel {L_2-8{keV}}= 10^{42} - 10^{45} \\mathrel {erg {} s^{-1}}), at redshifts 1 < z < 4.7, that were selected to be faint or undetected in the Herschel bands. We combine our deep ALMA continuum observations with deblended 8-500\\mathrel {μ m} photometry from Spitzer and Herschel, and use infrared (IR) SED fitting and AGN - star formation decomposition methods. The addition of the ALMA photometry results in an order of magnitude more X-ray AGN in our sample with a measured SFR (now 37 per cent). The remaining 63 per cent of the sources have SFR upper limits that are typically a factor of 2-10 times lower than the pre-ALMA constraints. With the improved constraints on the IR SEDs, we can now identify a mid-IR (MIR) AGN component in 50 per cent of our sample, compared to only ˜1 per cent previously. We further explore the F_{870\\mathrel {μ m}}/F_{24\\mathrel {μ m}}-redshift plane as a tool for the identification of MIR emitting AGN, for three different samples representing AGN dominated, star formation dominated, and composite sources. We demonstrate that the F_{870\\mathrel {μ m}}/F_{24\\mathrel {μ m}}-redshift plane can successfully split between AGN and star formation dominated sources, and can be used as an AGN identification method.

The AGN Luminosity Fraction in Galaxy Mergers

NASA Astrophysics Data System (ADS)

Dietrich, Jeremy; Weiner, Aaron; Ashby, Matthew; Martinez-Galarza, Juan Rafael; Smith, Howard Alan

2017-01-01

Galaxy mergers are key events in galaxy evolution, generally triggering massive starbursts and AGNs. However, in these chaotic systems, it is not yet known what fraction each of these two mechanisms contributes to the total luminosity. Here we measure and model spectral energy distributions (SEDs) using the Code for Investigating Galaxy Emission (CIGALE) in up to 33 broad bands from the UV to the far-IR for 23 IR-luminous galaxies to estimate the fraction of the bolometric IR luminosity that can be attributed to the AGN. The galaxies are split nearly evenly into two subsamples: late-stage mergers, found in the IRAS Revised Bright Galaxy Sample or Faint Source Catalog, and early-stage mergers found in the Spitzer Interacting Galaxy Sample. We find that the AGN contribution to the total IR luminosity varies greatly from system to system, from 0% up to ~90%, but is substantially greater in the later-stage and brighter mergers. This is consistent with what is known about galaxy evolution and the triggering of AGNs.The SAO REU program is funded in part by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant no. 1262851, and by the Smithsonian Institution.

Identifying the subtle signatures of feedback from distant AGN using ALMA observations and the EAGLE hydrodynamical simulations

NASA Astrophysics Data System (ADS)

Scholtz, J.; Alexander, D. M.; Harrison, C. M.; Rosario, D. J.; McAlpine, S.; Mullaney, J. R.; Stanley, F.; Simpson, J.; Theuns, T.; Bower, R. G.; Hickox, R. C.; Santini, P.; Swinbank, A. M.

2018-03-01

We present sensitive 870 μm continuum measurements from our ALMA programmes of 114 X-ray selected active galactic nuclei (AGN) in the Chandra Deep Field-South and Cosmic Evolution Survey fields. We use these observations in combination with data from Spitzer and Herschel to construct a sample of 86 X-ray selected AGN, 63 with ALMA constraints at z = 1.5-3.2 with stellar mass >2 × 1010 M⊙. We constructed broad-band spectral energy distributions in the infrared band (8-1000 μm) and constrain star-formation rates (SFRs) uncontaminated by the AGN. Using a hierarchical Bayesian method that takes into account the information from upper limits, we fit SFR and specific SFR (sSFR) distributions. We explore these distributions as a function of both X-ray luminosity and stellar mass. We compare our measurements to two versions of the Evolution and Assembly of GaLaxies and their Environments (EAGLE) hydrodynamical simulations: the reference model with AGN feedback and the model without AGN. We find good agreement between the observations and that predicted by the EAGLE reference model for the modes and widths of the sSFR distributions as a function of both X-ray luminosity and stellar mass; however, we found that the EAGLE model without AGN feedback predicts a significantly narrower width when compared to the data. Overall, from the combination of the observations with the model predictions, we conclude that (1) even with AGN feedback, we expect no strong relationship between the sSFR distribution parameters and instantaneous AGN luminosity and (2) a signature of AGN feedback is a broad distribution of sSFRs for all galaxies (not just those hosting an AGN) with stellar masses above ≈1010 M⊙.

OSSE Observations of Seyfert AGN

NASA Astrophysics Data System (ADS)

Johnson, W. N.; Grove, J. E.; Kinzer, R. L.; Kroeger, R. A.; Kurfess, J. D.; Strickman, M. S.; McNaron-Brown, K.; Grabelsky, D. A.; Purcell, W. R.; Ulmer, M. P.; Jung, G. V.; Cameron, R. A.

1993-12-01

In the first two years of the Compton Gamma Ray Observatory mission, the Oriented Scintillation Spectrometer Experiment (OSSE) has observed about two dozen Seyfert active galactic nuclei (AGN) selected from the HEAO-1 list (Rothschild et al. 1983) and intense X-ray sources detected by EXOSAT and Ginga. The OSSE observations in the 50 keV - 10 MeV range indicate spectra which, on average, are significantly softer than the power law photon index of Gamma =1.7 which is generally reported in the Xray band. The average spectrum is well described by exponential or thermal Comptonization models indicating a break in the spectrum near 100 keV. We summarize the OSSE observations of AGN and present the average Seyfert spectrum above 50 keV. Rothschild, R.E., et al. 1983, Ap. J., 269, 423.

The Keck OSIRIS Nearby AGN (KONA) Survey: AGN Fueling and Feedback

NASA Astrophysics Data System (ADS)

Hicks, Erin K. S.; Müller-Sánchez, Francisco; Malkan, Matthew A.; Yu, Po-Chieh

In an effort to better constrain the relevant physical processes dictating the co-evolution of supermassive black holes and the galaxies in which they reside we turn to local Seyfert AGN. It is only with these local AGN that we can reach the spatial resolution needed to adequately characterize the inflow and outflow mechanisms thought to be the driving forces in establishing the relationship between black holes and their host galaxies at higher redshift. We present the first results from the KONA (Keck OSIRIS Nearby AGN) survey, which takes advantage of the integral field unit OSIRIS plus laser and natural guide star adaptive optics to probe down to scales of 5-30 parsecs in a sample of 40 local Seyfert galaxies. With these K-band data we measure the two-dimensional distribution and kinematics of the nuclear stars, molecular gas, and ionized gas within the central few hundred parsecs.

XMM-Newton observations of the Lockman Hole IV: spectra of the brightest AGN

NASA Astrophysics Data System (ADS)

Mateos, S.; Barcons, X.; Carrera, F. J.; Ceballos, M. T.; Hasinger, G.; Lehmann, I.; Fabian, A. C.; Streblyanska, A.

2005-12-01

This paper presents the results of a detailed X-ray spectral analysis of a sample of 123 X-ray sources detected with XMM-Newton in the Lockman Hole field. This is the deepest observation carried out with XMM-Newton with more that 600 ks of good EPIC-pn data. We have spectra with good signal to noise (>500 source counts) for all objects down to 0.2-12 keV fluxes of 5×10-15 erg cm-2 s-1 (flux limit of 6×10-16 erg cm-2 s-1 in the 0.5-2 and 2-10 keV bands). At the time of the analysis, we had optical spectroscopic identifications for 60% of the sources, 46 being optical type-1 AGN and 28 optical type-2 AGN. Using a single power law model our sources' average spectral slope hardens at faint 0.5-2 keV fluxes but not at faint 2-10 keV fluxes. We have been able to explain this effect in terms of an increase in X-ray absorption at faint fluxes. We did not find in our data any evidence for the existence of a population of faint intrinsically harder sources. The average spectral slope of our sources is 1.9, with an intrinsic dispersion of 0.28. We detected X-ray absorption (F-test significance ≥95%) in 37% of the sources, 10% in type-1 AGN (rest-frame {NH ˜ 1.6 × 1021{-}1.2 × 1022 cm-2}) and 77% (rest-frame {NH ˜ 1.5 ×1021{-}4× 1023 cm-2}) in type-2 AGN. Using X-ray fluxes corrected for absorption, the fraction of absorbed objects and the absorbing column density distribution did not vary with X-ray flux. Our type-1 and type-2 AGN do not appear to have different continuum shapes, but the distribution of intrinsic (rest-frame) absorbing column densities is different among both classes. A significant fraction of our type-2 AGN (5 out of 28) were found to display no substantial absorption ({NH<1021 cm-2}). We discuss possible interpretations to this in terms of Compton-thick AGN and intrinsic Broad Line Region properties. An emission line compatible with Fe Kα was detected in 8 sources (1 type-1 AGN, 5 type-2 AGN and 2 unidentified) with rest frame equivalent widths

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

NASA Technical Reports Server (NTRS)

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 (z<0.05), moderate luminosity AGN 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.

A simple way to improve AGN feedback prescription in SPH simulations

NASA Astrophysics Data System (ADS)

Zubovas, Kastytis; Bourne, Martin A.; Nayakshin, Sergei

2016-03-01

Active galactic nuclei (AGN) feedback is an important ingredient in galaxy evolution, however its treatment in numerical simulations is necessarily approximate, requiring subgrid prescriptions due to the dynamical range involved in the calculations. We present a suite of smoothed particle hydrodynamics simulations designed to showcase the importance of the choice of a particular subgrid prescription for AGN feedback. We concentrate on two approaches to treating wide-angle AGN outflows: thermal feedback, where thermal and kinetic energy is injected into the gas surrounding the supermassive black hole (SMBH) particle, and virtual particle feedback, where energy is carried by tracer particles radially away from the AGN. We show that the latter model produces a far more complex structure around the SMBH, which we argue is a more physically correct outcome. We suggest a simple improvement to the thermal feedback model - injecting the energy into a cone, rather than spherically symmetrically - and show that this markedly improves the agreement between the two prescriptions, without requiring any noticeable increase in the computational cost of the simulation.

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

NASA Astrophysics Data System (ADS)

Dai, Xinyu; Griffin, Rhiannon D.; Kochanek, Christopher S.; Nugent, Jenna M.; Bregman, Joel N.

2015-05-01

The Swift active galactic nucleus (AGN) and Cluster Survey (SACS) uses 125 deg2 of Swift X-ray Telescope serendipitous fields with variable depths surrounding γ-ray bursts to provide a medium depth (4× {{10}-15} erg cm-2 s-1) 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 Wide-field Infrared Survey Explorer mid-infrared (MIR) colors to classify the sources. For AGNs we can roughly separate the point sources into MIR-red and MIR-blue AGNs, 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 previous surveys but span a much larger continuous flux range. Deep optical or IR follow-up observations of this cluster sample will significantly increase the number of higher-redshift (z\\gt 0.5) X-ray-selected clusters.

Optical Time-Domain and Radio Imaging Analyses of the Dynamic Hearts of AGN

NASA Astrophysics Data System (ADS)

Smith, Krista Lynne

Active galactic nuclei (AGN) are among the most extreme objects in the universe: galaxies with a central supermassive black hole feeding on gas from a hot accretion disk. Despite their potential as powerful tools to study topics ranging from relativity to cosmology, they remain quite mysterious. In the first portion of this thesis, we explore how an AGN may influence the formation of stars in its host galaxy. Using high-resolution 22 GHz radio imaging of an X-ray selected sample of radio-quiet AGN, we find that the far-infrared radio correlation for normal star forming galaxies remains valid within a few hundred parsecs of the central engine. Because the core flux is often spatially isolated from star formation, we can also determine that the radio emission in radio-quiet AGN is consistent with both coronal and disk-jet coupling models. Finally, we find that AGN with jet-like radio morphologies have suppressed star formation, possibly indicating ongoing feedback. The second portion of this thesis uses optical AGN light curves to study the physics of accretion. The Kepler spacecraft produces groundbreaking light curves, but its fixed field of view only contained a handful of known AGN. We conduct an X-ray survey of this field, yielding 93 unique X-ray sources identified by optical follow-up spectroscopy as a mixture of AGN and stars. For the AGN, we spectroscopically measure black hole masses and accretion rates. We then analyze a sample of 22 Kepler AGN light curves. We develop a customized pipeline for AGN science with Kepler, a necessary step since the initial data was optimized for the unique goal of exoplanet detection. The light curves display an astonishing variety of behaviors in a new regime of optical variability inaccessible with previous facilities. We find power spectral slopes inconsistent with the damped random walk model, characteristic variability timescales, correlations of variability properties with physical parameters, and bimodal flux

Large 21-cm signals from AGN-dominated reionization

NASA Astrophysics Data System (ADS)

Kulkarni, Girish; Choudhury, Tirthankar Roy; Puchwein, Ewald; Haehnelt, Martin G.

2017-08-01

We present predictions for the spatial distribution of 21-cm brightness temperature fluctuations from high-dynamic-range simulations for active galactic nucleus (AGN)-dominated reionization histories that have been tested against available Lyα and cosmic microwave background (CMB) data. We model AGNs by extrapolating the observed Mbh - σ relation to high redshifts and assign them ionizing emissivities consistent with recent UV luminosity function measurements. We assess the observability of the predicted spatial 21-cm fluctuations in the late stages of reionization in the limit in which the hydrogen 21-cm spin temperature is significantly larger than the CMB temperature. Our AGN-dominated reionization histories increase the variance of the 21-cm emission by a factor of up to 10 compared to similar reionization histories dominated by faint galaxies, to values close to 100 mK2 at scales accessible to experiments (k ≲ 1 cMpc-1 h). This is lower than the sensitivity reached by ongoing experiments only by a factor of about 2 or less. When reionization is dominated by AGNs, the 21-cm power spectrum is enhanced on all scales due to the enhanced bias of the clustering of the more massive haloes and the peak in the large scale 21-cm power is strongly enhanced and moved to larger scales due to bigger characteristic bubble sizes. AGN-dominated reionization should be easily detectable by Low Frequency Array (and later Hydrogen Epoch of Reionization Array and Phase 1 of the Square Kilometre Array) at their design sensitivity, assuming successful foreground subtraction and instrument calibration. Conversely, these could become the first non-trivial reionization scenarios to be ruled out by 21-cm experiments, thereby constraining the contribution of AGNs to reionization.

Enhancement of AGN Activity in Distant Galaxy Clusters

NASA Astrophysics Data System (ADS)

Krishnan, Charutha; Hatch, Nina; Almaini, Omar

2017-07-01

I present our recent study of the prevalence of X-ray AGN in the high-redshift protocluster Cl 0218.3-0510 at z=1.62, and review the implications for our understanding of galaxy evolution. There has long been a consensus that X-ray AGN avoid clusters in the local universe, particularly their cores. The high-redshift universe appears to not follow these trends, as there is a reversal in the local anti-correlation between galaxy density and AGN activity. In this z=1.62 protocluster, we find a large overdensity of AGN by a factor of 23, and an enhancement in the AGN fraction among massive galaxies relative to the field by a factor of 2. I will discuss the comparison of the properties of AGN in the protocluster to the field, and explain how our results point towards similar triggering mechanisms in the two environments. I will also describe how our study of the morphologies of these galaxies provide tentative evidence towards galaxy mergers and interactions being responsible for triggering AGN, and explain the reversal of the local anti-correlation between galaxy density and AGN activity.

The AGN-Star Formation Connection: Future Prospects with JWST

NASA Astrophysics Data System (ADS)

Kirkpatrick, Allison; Alberts, Stacey; Pope, Alexandra; Barro, Guillermo; Bonato, Matteo; Kocevski, Dale D.; Pérez-González, Pablo; Rieke, George H.; Rodríguez-Muñoz, Lucia; Sajina, Anna; Grogin, Norman A.; Mantha, Kameswara Bharadwaj; Pandya, Viraj; Pforr, Janine; Salvato, Mara; Santini, Paola

2017-11-01

The bulk of the stellar growth over cosmic time is dominated by IR-luminous galaxies at cosmic noon (z=1{--}2), many of which harbor a hidden active galactic nucleus (AGN). We use state-of-the-art infrared color diagnostics, combining Spitzer and Herschel observations, to separate dust-obscured AGNs from dusty star-forming galaxies (SFGs) in the CANDELS and COSMOS surveys. We calculate 24 μm counts of SFGs, AGN/star-forming “Composites,” and AGNs. AGNs and Composites dominate the counts above 0.8 mJy at 24 μm, and Composites form at least 25% of an IR sample even to faint detection limits. We develop methods to use the Mid-Infrared Instrument (MIRI) on JWST to identify dust-obscured AGNs and Composite galaxies from z˜ 1{--}2. With the sensitivity and spacing of MIRI filters, we will detect >4 times as many AGN hosts as with Spitzer/IRAC criteria. Any star formation rates based on the 7.7 μm PAH feature (likely to be applied to MIRI photometry) must be corrected for the contribution of the AGN, or the star formation rate will be overestimated by ˜35% for cases where the AGN provides half the IR luminosity and ˜50% when the AGN accounts for 90% of the luminosity. Finally, we demonstrate that our MIRI color technique can select AGNs with an Eddington ratio of {λ }{Edd}˜ 0.01 and will identify AGN hosts with a higher specific star formation rate than X-ray techniques alone. JWST/MIRI will enable critical steps forward in identifying and understanding dust-obscured AGNs and the link to their host galaxies.

THE XMM-NEWTON WIDE FIELD SURVEY IN THE COSMOS FIELD: REDSHIFT EVOLUTION OF AGN BIAS AND SUBDOMINANT ROLE OF MERGERS IN TRIGGERING MODERATE-LUMINOSITY AGNs AT REDSHIFTS UP TO 2.2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allevato, V.; Hasinger, G.; Salvato, M.

2011-08-01

We present a study of the redshift evolution of the projected correlation function of 593 X-ray selected active galactic nuclei (AGNs) with I{sub AB} < 23 and spectroscopic redshifts z < 4, extracted from the 0.5-2 keV X-ray mosaic of the 2.13 deg{sup 2} XMM- Cosmic Evolution Survey (COSMOS). We introduce a method to estimate the average bias of the AGN sample and the mass of AGN hosting halos, solving the sample variance using the halo model and taking into account the growth of the structure over time. We find evidence of a redshift evolution of the bias factor formore » the total population of XMM-COSMOS AGNs from b-bar (z-bar =0.92)=2.30{+-}0.11 to b-bar (z-bar =1.94)=4.37{+-}0.27 with an average mass of the hosting dark matter (DM) halos log M{sub 0}(h{sup -1} M{sub sun}) {approx} 13.12 {+-} 0.12 that remains constant at all z < 2. Splitting our sample into broad optical line AGNs (BL), AGNs without broad optical lines (NL), and X-ray unobscured and obscured AGNs, we observe an increase of the bias with redshift in the range z-bar = 0.7-2.25 and z-bar = 0.6-1.5 which corresponds to a constant halo mass of log M{sub 0}(h{sup -1} M{sub sun}) {approx} 13.28 {+-} 0.07 and log M{sub 0}(h{sup -1} M{sub sun}) {approx} 13.00 {+-} 0.06 for BL/X-ray unobscured AGNs and NL/X-ray obscured AGNs, respectively. The theoretical models, which assume a quasar phase triggered by major mergers, cannot reproduce the high bias factors and DM halo masses found for X-ray selected BL AGNs with L{sub BOL} {approx} 2 x 10{sup 45} erg s{sup -1}. Our work extends up to z {approx} 2.2 the z {approx}< 1 statement that, for moderate-luminosity X-ray selected BL AGNs, the contribution from major mergers is outnumbered by other processes, possibly secular ones such as tidal disruptions or disk instabilities.« less

High-energy neutrino fluxes from AGN populations inferred from X-ray surveys

NASA Astrophysics Data System (ADS)

Jacobsen, Idunn B.; Wu, Kinwah; On, Alvina Y. L.; Saxton, Curtis J.

2015-08-01

High-energy neutrinos and photons are complementary messengers, probing violent astrophysical processes and structural evolution of the Universe. X-ray and neutrino observations jointly constrain conditions in active galactic nuclei (AGN) jets: their baryonic and leptonic contents, and particle production efficiency. Testing two standard neutrino production models for local source Cen A (Koers & Tinyakov and Becker & Biermann), we calculate the high-energy neutrino spectra of single AGN sources and derive the flux of high-energy neutrinos expected for the current epoch. Assuming that accretion determines both X-rays and particle creation, our parametric scaling relations predict neutrino yield in various AGN classes. We derive redshift-dependent number densities of each class, from Chandra and Swift/BAT X-ray luminosity functions (Silverman et al. and Ajello et al.). We integrate the neutrino spectrum expected from the cumulative history of AGN (correcting for cosmological and source effects, e.g. jet orientation and beaming). Both emission scenarios yield neutrino fluxes well above limits set by IceCube (by ˜4-106 × at 1 PeV, depending on the assumed jet models for neutrino production). This implies that: (i) Cen A might not be a typical neutrino source as commonly assumed; (ii) both neutrino production models overestimate the efficiency; (iii) neutrino luminosity scales with accretion power differently among AGN classes and hence does not follow X-ray luminosity universally; (iv) some AGN are neutrino-quiet (e.g. below a power threshold for neutrino production); (v) neutrino and X-ray emission have different duty cycles (e.g. jets alternate between baryonic and leptonic flows); or (vi) some combination of the above.

Examining an AGN Luminosity – SFR relation

NASA Astrophysics Data System (ADS)

Stemo, Aaron; Comerford, Julia M.; Barrows, Robert Scott

2018-06-01

The relation between the star formation rate (SFR) of a galaxy and the accretion rate of its supermassive black hole is not well understood. Some observations show that active galactic nuclei (AGN) activity and SFR are correlated while other observations show no relation between the two. In this work we present a large, uniformly-selected catalog of HST galaxies that host AGN. Using available multiwavelength photometric data, we are able to determine AGN bolometric luminosity, host galaxy SFR, host galaxy stellar mass, and redshift for our sample. Using this catalog, we are able to compare AGN bolometric luminosity and SFR, while controlling for redshift and stellar mass. These comparisons will be used to make a statistically significant statement on the correlation between AGN activity and a host galaxy’s SFR.

Multi-phase outflows as probes of AGN accretion history

NASA Astrophysics Data System (ADS)

Nardini, Emanuele; Zubovas, Kastytis

2018-05-01

Powerful outflows with a broad range of properties (such as velocity, ionization, radial scale and mass loss rate) represent a key feature of active galactic nuclei (AGN), even more so since they have been simultaneously revealed also in individual objects. Here we revisit in a simple analytical framework the recent remarkable cases of two ultraluminous infrared quasars, IRAS F11119+3257 and Mrk 231, which allow us to investigate the physical connection between multi-phase AGN outflows across the ladder of distance from the central supermassive black hole (SMBH). We argue that any major deviations from the standard outflow propagation models might encode unique information on the past SMBH accretion history, and briefly discuss how this could help address some controversial aspects of the current picture of AGN feedback.

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

NASA Technical Reports Server (NTRS)

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.

The Incidence of Buried Dual AGN in Advanced Mergers: New results from Chandra

NASA Astrophysics Data System (ADS)

Pfeifle, Ryan William; Satyapal, Shobita; Secrest, Nathan; Gliozzi, Mario; Ricci, Claudio; Ellison, Sara L.; Blecha, Laura; Rothberg, Barry; Constantin, Anca

2018-01-01

Since the vast majority of galaxies contain supermassive black holes (SMBHs) and galaxy interactions trigger nuclear gas accretion, a direct consequence of the hierarchical model of galaxy formation would be the existence of dual active galactic nuclei (AGN). The existence, frequency, and characteristics of such dual AGN have important astrophysical implications on the SMBH mass function, the interplay between SMBHs and the host galaxy, and the M-sigma relation. Despite decades of searching, and strong theoretical reasons for their existence, observationally confirmed cases of dual AGN are extremely rare, and most have been discovered serendipitously. Using the all-sky WISE survey, we identified a population of over one hundred strongly interacting galaxies that display extreme red mid-infrared colors thus far exclusively associated with extragalactic sources possessing powerful AGN. In a recent Chandra, XMM-Newton, and NuSTAR investigation of advanced mergers selected by WISE, we find dual AGN candidates in 8 out of 15 mergers, all of which show no evidence for AGN based on optical spectroscopy. Our results demonstrate that 1) optical studies miss a significant fraction of single and dual AGN in advanced mergers, and 2) mid-infrared pre-selection is extremely effective in identifying dual AGN candidates in late-stage mergers. Our multi-wavelength observations suggest that the buried AGN in these mergers are highly absorbed, with intrinsic column densities in excess of NH > 1024 cm-2, consistent with hydrodynamic simulations.

AGN outflows as neutrino sources: an observational test

NASA Astrophysics Data System (ADS)

Padovani, P.; Turcati, A.; Resconi, E.

2018-04-01

We test the recently proposed idea that outflows associated with Active Galactic Nuclei (AGN) could be neutrino emitters in two complementary ways. First, we cross-correlate a list of 94 "bona fide" AGN outflows with the most complete and updated repository of IceCube neutrinos currently publicly available, assembled by us for this purpose. It turns out that AGN with outflows matched to an IceCube neutrino have outflow and kinetic energy rates, and bolometric powers larger than those of AGN with outflows not matched to neutrinos. Second, we carry out a statistical analysis on a catalogue of [O III] λ5007 line profiles using a sample of 23,264 AGN at z < 0.4, a sub-sample of which includes mostly possible outflows sources. We find no significant evidence of an association between the AGN and the IceCube events, although we get the smallest p-values (˜6 and 18 per cent respectively, pre-trial) for relatively high velocities and luminosities. Our results are consistent with a scenario where AGN outflows are neutrino emitters but at present do not provide a significant signal. This can be tested with better statistics and source stacking. A predominant role of AGN outflows in explaining the IceCube data appears in any case to be ruled out.

AGN outflows as neutrino sources: an observational test

NASA Astrophysics Data System (ADS)

Padovani, P.; Turcati, A.; Resconi, E.

2018-07-01

We test the recently proposed idea that outflows associated with Active Galactic Nuclei (AGN) could be neutrino emitters in two complementary ways. First, we cross-correlate a list of 94 'bona fide' AGN outflows with the most complete and updated repository of IceCube neutrinos currently publicly available, assembled by us for this purpose. It turns out that AGN with outflows matched to an IceCube neutrino have outflow and kinetic energy rates, and bolometric powers larger than those of AGN with outflows not matched to neutrinos. Secondly, we carry out a statistical analysis on a catalogue of [O III] λ5007 line profiles using a sample of 23 264 AGN at z < 0.4, a subsample of which includes mostly possible outflow sources. We find no significant evidence of an association between the AGN and the IceCube events, although we get the smallest p-values (˜6 and 18 per cent, respectively, pre-trial) for relatively high velocities and luminosities. Our results are consistent with a scenario where AGN outflows are neutrino emitters but at present do not provide a significant signal. This can be tested with better statistics and source stacking. A predominant role of AGN outflows in explaining the IceCube data appears in any case to be ruled out.

Modeling Soft Excess with GRMHD Accretion for XMM-Newton Spectra of Bright AGNs

NASA Astrophysics Data System (ADS)

Fukumura, K.; Haba, Y.; Takahashi, M.; Tombesi, F.

2017-10-01

Despite a number of well-studied X-ray observations of the so called soft excess (SE) from a certain class of AGNs in the past decades, its physical identification has remained to be elusive to date. With the absence of a single leading model, a few competing scenarios have been proposed. In this presentation, we show that the innermost plasma accretion under strong gravity can develop into an MHD shock front at r < 5 r_{g} where incoming thermal disk photons (of ˜ 10 eV) are efficiently Compton up-scattered by shock-accelerated electrons in its downstream region to produce the observed SE feature. Considering all the relativistic effects in our treatment, our GRMHD Comptonization model, consisting of (1) disk photon temperature (kT_{bb}), electron energy (Θ_{e}) and inclination (θ_{obs}) for a given black hole spin (a/m), can naturally provide the SE spectra for a fiducial parameter set by solving GRMHD flows. Our calculations indicate that the Comptonizing region is very compact just outside the black hole event horizon resembling a putative 'coronae' with a characteristic electron energy on the order of ˜ 100 keV determined by shock strength. We also show preliminary spectral analysis results for some stereotypical PG and NLS1 AGNs.

Suppression of AGN-Driven Turbulence by Magnetic Fields in a Magnetohydrodynamic Model of the Intracluster Medium

NASA Astrophysics Data System (ADS)

Bambic, Christopher J.; Morsony, Brian; Reynolds, Christopher S.

2018-01-01

We investigate the role of AGN feedback in turbulent heating of galaxy clusters. Specifically, we analyze the production of turbulence by g-modes generated by the supersonic expansion and buoyant rise of AGN-driven bubbles. Previous work which neglects magnetic fields has shown that this process is inefficient, with less than 1% of the injected energy ending up in turbulence. This inefficiency is primarily due to the fact that the bubbles are shredded apart by hydrodynamic instabilities before they can excite sufficiently strong g-modes. Using a plane-parallel model of the ICM and 3D ideal MHD simulations, we examine the role of a large-scale magnetic field which is able to drape around these rising bubbles, preserving them from hydrodynamic instabilities. We find that, while magnetic draping appears better able to preserve AGN-driven bubbles, the driving of g-modes and the resulting production of turbulence is still inefficient. The magnetic tension force prevents g-modes from transitioning into the nonlinear regime, suppressing turbulence in our model ICM below levels measured in hydrodynamic simulations. Our work highlights the ways in which ideal MHD is an insufficient description for the cluster feedback process, and we discuss future work such as the inclusion of anisotropic viscosity as a means of simulating high β plasma kinetic effects. These results suggest the hypothesis that other mechanisms of heating the ICM plasma such as sound waves or cosmic rays may be responsible for observed feedback in galaxy clusters.

Suppression of AGN-driven Turbulence by Magnetic Fields in a Magnetohydrodynamic Model of the Intracluster Medium

NASA Astrophysics Data System (ADS)

Bambic, Christopher J.; Morsony, Brian J.; Reynolds, Christopher S.

2018-04-01

We investigate the role of active galactic nucleus (AGN) feedback in turbulent heating of galaxy clusters. Specifically, we analyze the production of turbulence by g-modes generated by the supersonic expansion and buoyant rise of AGN-driven bubbles. Previous work that neglects magnetic fields has shown that this process is inefficient, with less than 1% of the injected energy ending up in turbulence. This inefficiency primarily arises because the bubbles are shredded apart by hydrodynamic instabilities before they can excite sufficiently strong g-modes. Using a plane-parallel model of the intracluster medium (ICM) and 3D ideal magnetohydrodynamics (MHD) simulations, we examine the role of a large-scale magnetic field that is able to drape around these rising bubbles, preserving them from hydrodynamic instabilities. We find that while magnetic draping appears better able to preserve AGN-driven bubbles, the driving of g-modes and the resulting production of turbulence is still inefficient. The magnetic tension force prevents g-modes from transitioning into the nonlinear regime, suppressing turbulence in our model ICM. Our work highlights the ways in which ideal MHD is an insufficient description for the cluster feedback process, and we discuss future work such as the inclusion of anisotropic viscosity as a means of simulating high β plasma kinetic effects. These results suggest the hypothesis that other mechanisms of heating the ICM plasma such as sound waves or cosmic rays may be responsible for the observed feedback in galaxy clusters.

The cosmic evolution of massive black holes in the Horizon-AGN simulation

NASA Astrophysics Data System (ADS)

Volonteri, M.; Dubois, Y.; Pichon, C.; Devriendt, J.

2016-08-01

We analyse the demographics of black holes (BHs) in the large-volume cosmological hydrodynamical simulation Horizon-AGN. This simulation statistically models how much gas is accreted on to BHs, traces the energy deposited into their environment and, consequently, the back-reaction of the ambient medium on BH growth. The synthetic BHs reproduce a variety of observational constraints such as the redshift evolution of the BH mass density and the mass function. Strong self-regulation via AGN feedback, weak supernova feedback, and unresolved internal processes result in a tight BH-galaxy mass correlation. Starting at z ˜ 2, tidal stripping creates a small population of BHs over-massive with respect to the halo. The fraction of galaxies hosting a central BH or an AGN increases with stellar mass. The AGN fraction agrees better with multi-wavelength studies, than single-wavelength ones, unless obscuration is taken into account. The most massive haloes present BH multiplicity, with additional BHs gained by ongoing or past mergers. In some cases, both a central and an off-centre AGN shine concurrently, producing a dual AGN. This dual AGN population dwindles with decreasing redshift, as found in observations. Specific accretion rate and Eddington ratio distributions are in good agreement with observational estimates. The BH population is dominated in turn by fast, slow, and very slow accretors, with transitions occurring at z = 3 and z = 2, respectively.

Probing the Properties of AGN Clustering in the Local Universe with Swift-BAT

NASA Astrophysics Data System (ADS)

Powell, M.; Cappelluti, N.; Urry, M.; Koss, M.; Allevato, V.; Ajello, M.

2017-10-01

I present the benchmark measurement of AGN clustering in the local universe with the all-sky Swift-BAT survey. The hard X-ray selection (14-195 keV) allows for the detection of some of the most obscured AGN, providing the largest, most unbiased sample of local AGN to date. We derive for the first time the halo occupation distribution (HOD) of the sample in various bins of black hole mass, accretion rate, and obscuration. In doing so, we characterize the cosmic environment of growing supermassive black holes with unprecedented precision, and determine which black hole parameters depend on environment. We then compare our results to the current evolutionary models of AGN.

Silicate Dust in Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Xie, Yanxia; Li, Aigen; Hao, Lei

2017-01-01

The unification theory of active galactic nuclei (AGNs) hypothesizes that all AGNs are surrounded by an anisotropic dust torus and are essentially the same objects but viewed from different angles. However, little is known about the dust that plays a central role in the unification theory. There are suggestions that the AGN dust extinction law appreciably differs from that of the Galaxy. Also, the silicate emission features observed in type 1 AGNs appear anomalous (I.e., their peak wavelengths and widths differ considerably from that of the Galaxy). In this work, we explore the dust properties of 147 AGNs of various types at redshifts z≲ 0.5, with special attention paid to 93 AGNs that exhibit the 9.7 and 18 μm silicate emission features. We model their silicate emission spectra obtained with the Infrared Spectrograph aboard the Spitzer Space Telescope. We find that 60/93 of the observed spectra can be well explained with “astronomical silicate,” while the remaining sources favor amorphous olivine or pyroxene. Most notably, all sources require the dust to be micron-sized (with a typical size of ˜1.5 ± 0.1 μm), much larger than submicron-sized Galactic interstellar grains, implying a flat or “gray” extinction law for AGNs. We also find that, while the 9.7 μm emission feature arises predominantly from warm silicate dust of temperature T ˜ 270 K, the ˜5-8 μm continuum emission is mostly from carbon dust of T ˜ 640 K. Finally, the correlations between the dust properties (e.g., mass, temperature) and the AGN properties (e.g., luminosity, black hole mass) have also been investigated.

Warm Absorber Diagnostics of AGN Dynamics

NASA Astrophysics Data System (ADS)

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

Unification of Gauge Couplings in the E{sub 6}SSM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Athron, P.; King, S. F.; Luo, R.

2010-02-10

We argue that in the two--loop approximation gauge coupling unification in the exceptional supersymmetric standard model (E{sub 6}SSM) can be achieved for any phenomenologically reasonable value of alpha{sub 3}(M{sub Z}) consistent with the experimentally measured central value.

Non-blackbody Disks Can Help Explain Inferred AGN Accretion Disk Sizes

NASA Astrophysics Data System (ADS)

Hall, Patrick B.; Sarrouh, Ghassan T.; Horne, Keith

2018-02-01

If the atmospheric density {ρ }atm} in the accretion disk of an active galactic nucleus (AGN) is sufficiently low, scattering in the atmosphere can produce a non-blackbody emergent spectrum. For a given bolometric luminosity, at ultraviolet and optical wavelengths such disks have lower fluxes and apparently larger sizes as compared to disks that emit as blackbodies. We show that models in which {ρ }atm} is a sufficiently low fixed fraction of the interior density ρ can match the AGN STORM observations of NGC 5548 but produce disk spectral energy distributions that peak at shorter wavelengths than observed in luminous AGN in general. Thus, scattering atmospheres can contribute to the explanation for large inferred AGN accretion disk sizes but are unlikely to be the only contributor. In the appendix section, we present unified equations for the interior ρ and T in gas pressure-dominated regions of a thin accretion disk.

Accretion Disk and Dust Emission in Low-Luminosity AGN

NASA Astrophysics Data System (ADS)

Biddle, Lauren I.; Mason, Rachel; Alonso-Herrero, Almudena; Colina, Luis; Diaz, Ruben; Flohic, Helene; Gonzalez-Martin, Omaira; Ho, Luis C.; Lira, Paulina; Martins, Lucimara; McDermid, Richard; Perlman, Eric S.; Ramos Almeida, Christina; Riffel, Rogerio; Ardila, Alberto; Ruschel Dutra, Daniel; Schiavon, Ricardo; Thanjavur, Karun; Winge, Claudia

2015-01-01

Observations obtained in the near-infrared (near-IR; 0.8 - 2.5 μm) can assist our understanding of the physical and evolutionary processes of galaxies. Using a set of near-IR spectra of nearby galaxies obtained with the cross-dispersed mode of GNIRS on the Gemini North telescope, we investigate how the accretion disk and hot dust emission depend on the luminosity of the active nucleus. We recover faint AGN emission from the starlight-dominated nuclear regions of the galaxies, and measure properties such as the spectral shape and luminosity of the accretion disk and dust. The aim of this work is to establish whether the standard thin accretion disk may be truncated in low-accretion-rate AGN, as well as evaluate whether the torus of the AGN unified model still exists at low luminosities.

Chandra Survey of Nearby Galaxies: Testing the Accretion Model for Low-luminosity AGNs

NASA Astrophysics Data System (ADS)

She, Rui; Ho, Luis C.; Feng, Hua; Cui, Can

2018-06-01

From a Chandra sample of active galactic nuclei (AGNs) in nearby galaxies, we find that for low-luminosity AGNs, either the intrinsic absorption column density, or the fraction of absorbed AGNs, positively scales with the Eddington ratio for L bol/L Edd ≲ 10‑2. Such a behavior, along with the softness of the X-ray spectrum at low luminosities, is in good agreement with the picture that they are powered by hot accretion flows surrounding supermassive black holes. Numerical simulations find that outflows are inevitable with hot accretion flows, and the outflow rate is correlated with the innermost accretion rate in the low-luminosity regime. This agrees well with our results, suggesting that the X-ray absorption originates from, or is associated with, the outflow material. Gas and dust on larger scales may also produce the observed correlation. Future correlation analyses may help differentiate the two scenarios.

Fast Ionized X-Ray Absorbers in AGNs

NASA Technical Reports Server (NTRS)

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

2016-01-01

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(sub H), line-of-sight (LoS) velocity v, ionization parameter xi, among others. Assuming that the wind density scales as n varies as r(exp. -1), we calculate theoretical absorption measure distribution (AMD) for various ions seen in AGNs as well as line spectra especially for the Fe K alpha 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.

Fast ionized X-ray absorbers in AGNs

NASA Astrophysics Data System (ADS)

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.

Ionized Absorbers in AGN

NASA Technical Reports Server (NTRS)

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".

A decade of Rossi X-ray Timing Explorer Seyfert observations: An RXTE Seyfert spectral database

NASA Astrophysics Data System (ADS)

Mattson, Barbara Jo

2008-10-01

With over forty years of X-ray observations, we should have a grasp on the X- ray nature of active galactic nuclei (AGN). The unification model of Antonucci and Miller (1985) offered a context for understanding observations by defining a "typical" AGN geometry, with observed spectral differences explained by line- of-sight effects. However, the emerging picture is that the central AGN is more complex than unification alone can describe. We explore the unified model with a systematic X-ray spectral study of bright Seyfert galaxies observed by the Rossi X-Ray Timing Explorer (RXTE) over its first 10 years. We develop a spectral-fit database of 821 time-resolved spectra from 39 Seyfert galaxies fitted to a model describing the effects of an X-ray power-law spectrum reprocessed and absorbed by material in the central AGN region. We observe a relationship between radio and X-ray properties for Seyfert 1s, with the spectral parameters differing between radio-loud and radio-quiet Seyfert 1s. We also find a complex relationship between the Fe K equivalent width ( EW ) and the power-law photon index (Gamma) for the Seyfert 1s, with a correlation for the radio-loud sources and an anti-correlation for the radio- quiet sources. These results can be explained if X-rays from the relativistic jet in radio-loud sources contribute significantly to the observed spectrum. We observe scatter in the EW-Gamma relationship for the Seyfert 2s, suggesting complex environments that unification alone cannot explain. We see a strong correlation between Gamma and the reflection fraction ( R ) in the Seyfert 1 and 2 samples, but modeling degeneracies are present, so this relationship cannot be trusted as instructive of the AGN physics. For the Seyfert 1 sample, we find an anticorrelation between EW and the 2 to 10 keV luminosity ( L x ), also known as the X-ray Baldwin effect. This may suggest that higher luminosity sources contain less material or may be due to a time-lag effect. We do not

Dark Matter after LHC Run I: Clues to Unification

NASA Astrophysics Data System (ADS)

Olive, Keith A.

2017-03-01

After the results of Run I, can we still `guarantee' the discovery of supersymmetry at the LHC? It is shown that viable dark matter models in CMSSM-like models tend to lie in strips (co-annihilation, funnel, focus point). The role of grand unification in constructing supersymmetric models is discussed and it is argued that non-supersymmetric GUTs such as SO(10) may provide solutions to many of the standard problems addressed by supersymmetry.

The different neighbours around Type-1 and Type-2 active galactic nuclei

NASA Astrophysics Data System (ADS)

Villarroel, Beatriz; Korn, Andreas J.

2014-06-01

One of the most intriguing open issues in galaxy evolution is the structure and evolution of active galactic nuclei (AGN) that emit intense light believed to come from an accretion disk near a super massive black hole. To understand the zoo of different AGN classes, it has been suggested that all AGN are the same type of object viewed from different angles. This model--called AGN unification--has been successful in predicting, for example, the existence of hidden broad optical lines in the spectrum of many narrow-line AGN. But this model is not unchallenged and it is debatable whether more than viewing angle separates the so-called Type-1 and Type-2 AGN. Here we report the first large-scale study that finds strong differences in the galaxy neighbours to Type-1 and Type-2 AGN with data from the Sloan Digital Sky Survey (SDSS; ref. ) Data Release 7 (DR7; ref. ) and Galaxy Zoo. We find strong differences in the colour and AGN activity of the neighbours to Type-1 and Type-2 AGN and in how the fraction of AGN residing in spiral hosts changes depending on the presence or not of a neighbour. These findings suggest that an evolutionary link between the two major AGN types might exist.

The Host Galaxies Of UV-selected AGNs At z 2-3

NASA Astrophysics Data System (ADS)

Hainline, Kevin; Shapley, A.; Greene, J.; Steidel, C.

2012-01-01

An important goal for studies of galaxy formation consists of tracing a direct evolutionary connection between the growth of supermassive black holes powering active galactic nuclei (AGNs) and the build-up of stellar mass in their host galaxies. In the local universe, AGNs are preferentially found in bulge-dominated galaxies, but the AGN demographics at earlier epochs are not as well understood. We present a rest-frame UV composite spectrum for a sample of 33 z 2-3 AGNs drawn from the UV-selected Lyman Break Galaxy (LBG) survey. This spectrum shows many emission and absorption features, such as HI Lyman-alpha, NV 1240, NIV] 1483, 1486, CIV 1548, 1550, HeII 1640, and CIII] 1907, 1909. Redshifted SiIV 1394 absorption provides evidence for outflowing high-ionization gas in these objects at speeds of 103 km/s. Finally, using optical, near-IR, and mid-IR photometry, which cover the rest-frame UV to near-IR portions of the galaxies' spectral energy distributions, we perform stellar population synthesis modeling of the sample. Based on these results, we explore the relationship in the host galaxy between AGN activity, maturity of the stellar population, and regulation of star formation.

The Compton-thick AGN fraction from the deepest X-ray spectroscopy in the CDF-S

NASA Astrophysics Data System (ADS)

Corral, A.; Georgantopoulos, I.; Akylas, A.; Ranalli, P.

2017-10-01

Highly obscured AGN, especially Compton-thick (CT) AGN, likely play a key role in the galaxy-AGN co-evolution scenario. They would comprise the early stages of AGN activity, preceding the AGN-feedback/star-formation quenching phase, during which most of both the SMBH and galaxy growth take place. However, the actual CT fraction among the AGN population is still largely unconstrained. The most reliable way of confirming the obscured nature of an AGN by X-ray spectroscopy, but very deep observations are needed to extend local analyses to larger distances. We will present the X-ray spectral analysis of the deepest X-ray data obtained to date, the almost 7Ms observation of the Chandra Deep Field South. The unprecedented depth of this survey allow us to carry out reliable spectral analyses down to a flux limit of 10^{-16} erg cm^{-2} s^{-1} in the hard 2-8 keV band. Besides the new deeper X-ray data, our approach also includes the implementation of Bayesian inference in the determination of the CT fraction. Our results favor X-ray background synthesis models which postulate a moderate fraction (25%) of CT objects among the obscured AGN population.

AGN jets as pion factories

NASA Astrophysics Data System (ADS)

Mannheim, Karl

There has been a dramatic revolution in gamma-ray astronomy throughout the last few years. Beginning with the discovery made by the spark chamber EGRET on board the Compton Gamma Ray Observatory that AGN with jets are the most powerful quasi-steady gamma-ray sources in the Universe, air-Cerenkov telescopes have soon after succeeded in detecting gamma-rays up to TeV energies. In the last year, it has become clear that these AGN emit photons even up to 10 TeV and more. This is a strong indication for proton acceleration going on in them, since protons owing to their large mass suffer weaker energy losses than electrons and can thus reach higher energies. Nucleons escaping from the AGN jets contribute to the local flux of cosmic rays at highest energies. If AGN produce the diffuse gamma-ray background, they would also be able to produce all the cosmic rays above the ankle in the local spectrum. The majority of AGN resides at large distances, indicated by their cosmological redshifts, and can therefore not be seen through the fog of electron-positron pairs which they produce interacting with diffuse infrared radiation from the era of galaxy formation. To observe the cosmic accelerators at large redshifts, neutrino observations are required. It is important to understand the astrophysical neutrino sources in order to be able to recognize signatures of new physics, e.g. due to decaying or annihilating particles from the early phases of the Universe.

Tracing Supermassive Black Hole Growth with Offset and Dual AGN

NASA Astrophysics Data System (ADS)

Comerford, Julia

The growth of supermassive black holes is tied to the evolution of their host galaxies, but we are still missing a fundamental understanding of how and when supermassive black holes build up their mass. Black hole mass growth can be traced when the black holes are powered as active galactic nuclei (AGN), and AGN activity can be triggered by the stochastic accretion of gas or by gas inflows driven by galaxy mergers. Galaxy merger simulations make a series of predictions about the AGN that are triggered by mergers: (1) major mergers preferentially trigger higher-luminosity AGN, (2) minor mergers more often trigger AGN activity in one supermassive black hole while major mergers more often trigger AGN activity in both black holes in a merger, and (3) black hole mass growth peaks when the black holes approach the center (<10 kpc separations) of the merger-remnant galaxy. Observational tests of these predictions from theory have been limited by the difficulty in defining a clean observational sample of AGN in galaxy mergers and the observational challenge of spatially resolving two AGN with small (<10kpc) separations. Here we present offset and dual AGN as a new observational tool that can be used to address how and when supermassive black hole mass growth occurs. A merger of two galaxies brings two supermassive black holes together, and the two black holes exist at kpc-scale separations for 100 Myr before ultimately merging. While the black holes are at kpc-scale separations, they are known as dual AGN when both of them are fueled as AGN and offset AGN when only one is fueled as an AGN. Since offset and dual AGN only occur in galaxy mergers, by their very definition, they provide a clean observational sample of black hole mass growth in galaxy mergers. The small, kpc-scale separations of offset and dual AGN also enable an observational test of black hole fueling near the centers of merger-remnant galaxies. The full potential of offset and dual AGN for such studies of

International Scientific Terminology and Neologisms in the Course of Unification.

ERIC Educational Resources Information Center

Stoberski, Zygmunt

1978-01-01

Provides a list of international medical and pharmaceutical terminology in three stages of development: (1) established international terms; (2) neologisms in the course of unification; and (3) recent neologisms in the course of unification. (AM)

They Call Me Agnes: A Crow Narrative Based on the Life of Agnes Yellowtail Deernose.

ERIC Educational Resources Information Center

Voget, Fred W.; Mee, Mary K.

This book is about life on the Crow Indian Reservation from around 1910 to the present and is based on the personal experiences of Donnie and Agnes Deernose. Following Donnie's death, Agnes became the principal narrator of the book. The Crow Indian Reservation is situated between Billings, Montana, and Sheridan, Wyoming. More so than any other…

LHC phenomenology of SO(10) models with Yukawa unification

NASA Astrophysics Data System (ADS)

Anandakrishnan, Archana; Bryant, B. Charles; Raby, Stuart; Wingerter, Akın

2013-10-01

In this paper we study an SO(10) SUSY GUT with Yukawa unification for the third generation. We perform a global χ2 analysis given to obtain the GUT boundary conditions consistent with 11 low-energy observables, including the top, bottom and tau masses. We assume a universal mass, m16, for squarks and sleptons and a universal gaugino mass, M1/2. We then analyze the phenomenological consequences for the LHC for 15 benchmark models with fixed m16=20TeV and with varying values of the gluino mass. The goal of the present work is to (i) evaluate the lower bound on the gluino mass in our model coming from the most recent published data of CMS and (ii) to compare this bound with similar bounds obtained by CMS using simplified models. The bottom line is that the bounds coming from the same-sign dilepton analysis are comparable for our model and the simplified model studied assuming B(g˜→tt¯χ˜10)=100%. However the bounds coming from the purely hadronic analyses for our model are 10%-20% lower than obtained for the simplified models. This is due to the fact that for our models the branching ratio for the decay g˜→gχ˜1,20 is significant. Thus there are significantly fewer b-jets. We find a lower bound on the gluino mass in our models with Mg˜≳1000GeV. Finally, there is a theoretical upper bound on the gluino mass which increases with the value of m16. For m16≤30TeV, the gluino mass satisfies Mg˜≤2.8TeV at 90% C.L. Thus, unless we further increase the amount of fine-tuning, we expect gluinos to be discovered at LHC 14.

Compton Thick AGN in the XMM-COSMOS field

NASA Astrophysics Data System (ADS)

Lanzuisi, G.; Perna, M.; Delvecchio, I.; Berta, S.; Brusa, M.; Gruppioni, C.; Comastri, A.

2016-06-01

I will present results we published in two recent papers (Lanzuisi et al. 2015, A&A 573A 137, Lanzuisi et al. 2015, A≈A 578A 120) on the properties of X-ray selected Compton Thick (CT, NH>10^{24} cm^{-2}) AGN, in the XMM-COSMOS survey. We exploited the rich multi-wavelength dataset available in this field, to show that CT AGN tend to harbor smaller, rapidly growing SMBH with respect to unobscured AGN, and have a higher chance of being hosted by star-forming, merging and post-merger systems. We also demonstrated the detectability of even more heavily obscured AGN (NH>10^{25} cm^{-2}), thanks to a truly multi-wavelength approach in the same field, and to the unrivaled XMM sensitivity. The extreme source detected in this way shows strong evidences of ongoing powerful AGN feedback, detected as blue-shifted wings of high ionization optical emission lines such as [NeV] and [FeVII], as well as of the [OIII] emission line. The results obtained from these works point toward a scenario in which highly obscured AGN occupy a peculiar place in the galaxy-AGN co-evolution process, in which both the host and the SMBH rapidly evolve toward the local relations.

The power of infrared AGN selection in mergers: a theoretical study

NASA Astrophysics Data System (ADS)

Blecha, Laura; Snyder, Gregory F.; Satyapal, Shobita; Ellison, Sara L.

2018-05-01

The role of galaxy mergers in fueling active galactic nuclei (AGN) is still debated, owing partly to selection effects inherent to studies of the merger/AGN connection. In particular, luminous AGN are often obscured in late-stage mergers. Mid-infrared (IR) color selection of dust-enshrouded AGN with, e.g., the Wide-field Infrared Survey Explorer (WISE) has uncovered large new populations of obscured AGN. However, this method is sensitive mainly to AGN that dominate emission from the host. To understand how selection biases affect mid-IR studies of the merger/AGN connection, we simulate the evolution of AGN throughout galaxy mergers. Although mid-IR colors closely trace luminous, obscured AGN, we show that nearly half of merger-triggered AGN are missed with common mid-IR selection criteria, even in late-stage, gas-rich major mergers. At z ⪉ 0.5, where merger signatures and dual nuclei can most easily be detected, we find that a more lenient W1 - W2 >0.5 cut greatly improves completeness without significantly decreasing reliability. Extreme nuclear starbursts are briefly able to mimic this AGN signature, but this is largely irrelevant in mergers, where such starbursts are accompanied by AGN. We propose a two-color cut that yields high completeness and reliability even in starbursting systems. Further, we show that mid-IR color selection very effectively identifies dual AGN hosts, with the highest fraction at the smallest separations (<3 kpc). Thus, many merger hosts of mid-IR AGN should contain unresolved dual AGN; these are ideal targets for high-resolution follow-up, particularly with the James Webb Space Telescope.

Low Mass AGN: Combining IRAC With Near-IR Grism Spectroscopy

NASA Astrophysics Data System (ADS)

Colbert, James; Teplitz, Harry; Malkan, Matt; Scarlata, Claudia; Bagley, Micaela; Baronchelli, Ivano; Hayden-Pawson, Connor; Rafelski, Marc

2017-10-01

Low mass AGN are critical to understanding the evolution of AGNs and stars in galaxies, marking the time periods of highest accretion efficiency and greatest likely deviations from the black hole mass - sigma correlation. Using the WFC3 Infrared Spectroscopic Parallels (WISP), we have just recently identified 68 candidate z > 1 AGN in 27 fields from their near-infrared emission line ratios. The WISP survey selects emission line galaxies without any pre-selection bias and is exquisitely sensitive to low mass (down to 10^7 solar masses), high-equivalent width galaxies that are missed by most other surveys. We propose to take IRAC 4.5 micron imaging of these AGN candidate fields in order to confirm 68 low mass AGN candidates, identify additional low mass IR-AGN missed by emission line selection, and produce the SED fits that can separate hot dust from star light, allowing comparison of stellar mass to AGN bolometric luminosity. The upcoming Euclid and WFIRST missions will generate hundreds of thousands of near-infrared spectra over a similar redshift range to WISP. For most of these objects, near-infrared emission line ratios will be the only viable AGN diagnostic. The Spitzer IRAC color AGN selection is one of the most robust AGN identifiers available. We wish to test these near-infrared emission line selection methods against the IRAC selection in order to evaluate the reliability of the AGN these future missions are likely to produce.

Unification of Fundamental Forces

NASA Astrophysics Data System (ADS)

Salam, Abdus; Taylor, Foreword by John C.

2005-10-01

Foreword John C. Taylor; 1. Unification of fundamental forces Abdus Salam; 2. History unfolding: an introduction to the two 1968 lectures by W. Heisenberg and P. A. M. Dirac Abdus Salam; 3. Theory, criticism, and a philosophy Werner Heisenberg; 4. Methods in theoretical physics Paul Adrian Maurice Dirac.

A WISE Selection of MIR AGN in Different Environments

NASA Astrophysics Data System (ADS)

Cheeseboro, Belinda D.; Norman, Dara J.

2015-01-01

This study was undertaken to understand the role of large scale environment in the evolution of MIR-selected AGN. In this study we examine AGN candidates in two types of environments: 7 clusters and 6 blank fields. Two types of clusters were studied in this project: 3 virialized and 4 non-virialized. The redshift of the clusters ranged 0.22≤z≤0.28. We used the mid-infrared WISE All-Sky database to identify AGN, applying various methods to refine our AGN candidate selection. To ascertain if there is an excess or deficit of MIR AGN in galaxy clusters vs. blank fields, we compared the AGN candidate distributions in virialized vs. non-virialized clusters to the blank fields. After close examination and comparison of the results to X-ray selected AGN from the Gilmour et al. (2009) study, we concluded that we do not detect an excess or deficit of MIR AGN in our clusters whether the cluster was virialized or non-virialized. This contrasted the conclusion of the Gilmour et al. (2009) study where there was an excess of X-Ray selected AGN in clusters.We also note an interesting feature in our WISE color-color plots that might be used for further investigation.Cheeseboro was supported by the NOAO/KPNO ResearchExperiences for Undergraduates (REU) Program which is funded by theNational Science Foundation Research Experiences for UndergraduatesProgram (AST-1262829).

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

NASA Astrophysics Data System (ADS)

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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Assef, R. J.; Diaz-Santos, T.; Walton, D. J.

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 DOGsmore » 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.« less

Complete Hard X-Ray Surveys, AGN Luminosity Functions and the X-Ray Background

NASA Technical Reports Server (NTRS)

Tueller, Jack

2011-01-01

AGN are believed to make up most of the Cosmic X-Ray Background (CXB) above a few keV, but this background cannot be fully resolved at energies less than 10 keV due to absorption. The Swift/BAT and INTEGRAL missions are performing the first complete hard x-ray surveys with minimal bias due to absorption. The most recent results for both missions will be presented. Although the fraction of the CXB resolved by these surveys is small, it is possible to derive unbiased number counts and luminosity functions for AGN in the local universe. The survey energy range from 15-150 keV contains the important reflection and cutoff spectral features dominate the shape of the AGN contribution to the CXB. Average spectral characteristics of survey detected AGN will be presented and compared with model distributions. The numbers of hard x-ray blazars detected in these surveys are finally sufficient to estimate this important component's contribution the cosmic background. Constraints on CXB models and their significance will be discussed.

Making Sense of Black Holes: Modeling the Galactic Center and Other Low-power AGN

NASA Astrophysics Data System (ADS)

Falcke, Heino; Moscibrodzka, Monika

2018-06-01

The Galactic center host a well-known flat-spectrum radio source, Sgr A*, that is akin to the radio nuclei of quasars and radio galaxies. It is the main target of the Event Horizon Telescope to image the shadow of the black hole. There is, however, still considerable discussion on where the near-horizon emission originates from. Does it come from an accretion flow or is it produced in a relativistic jet-like outflow? Using advanced three-dimensional general relativistic magnetohydrodynamics simulations coupled to general relativistic ray tracing simulations, we now model the dynamics and emission of the plasma around starving black holes in great detail out to several thousand Schwarzschild radii. Jets appear almost naturally in theses simulations. A crucial parameter is the heating of radiating electrons and we argue that electron-proton coupling is low in the accretion flow and high in the magnetized region of the jets, making the jet an important ingredient for the overall appearance of the source. This comprehensive model is able to predict the radio size and appearance, the spectral energy distribution from radio to X-rays, the variability, and the time lags of Sgr A* surprisingly well. Interestingly, the same model can be easily generalized to other low-power AGN like M87, suggesting that GRMHD models for AGN are finally becoming predictive. With upcoming submm-VLBI experiment on the ground and in space, we will be able to further test these models in great detail and see black holes in action.

Chandra and NuSTAR Follow-up Observations of Swift-BAT-selected AGNs

NASA Astrophysics Data System (ADS)

Marchesi, S.; Tremblay, L.; Ajello, M.; Marcotulli, L.; Paggi, A.; Cusumano, G.; La Parola, V.; Segreto, A.

2017-10-01

Based on current models of the cosmic X-ray background (CXB), heavily obscured active galactic nuclei (AGNs) are expected to make up ˜10% of the peak emission of the CXB and ˜20% of the total population of AGNs, yet few of these sources have been recorded and characterized in current surveys. Here we present the Chandra follow-up observation of 14 AGNs detected by Swift-BAT. For five sources in the sample, NuSTAR observations in the 3-80 keV band are also available. The X-ray spectral fitting over the 0.3-150 keV energy range allows us to determine the main X-ray spectral parameters, such as the photon index and the intrinsic absorption, of these objects and to make hypotheses on the physical structures responsible for the observed spectra. We find that 13 of the 14 objects are absorbed AGNs, and one is a candidate Compton-thick AGN, having intrinsic absorption {N}{{H}}> {10}24 cm-2. Finally, we verified that the use of NuSTAR observations is strategic to strongly constrain the properties of obscured AGNs, since the best-fit values we obtained for parameters such as the power-law photon index Γ and the intrinsic absorption {N}{{H}} changed sometimes significantly fitting the spectra with and without the use of NuSTAR data.

Mini-Survey on SDSS OIII AGN with Swift

NASA Technical Reports Server (NTRS)

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.

AGN feedback compared: jets versus radiation

NASA Astrophysics Data System (ADS)

Cielo, Salvatore; Bieri, Rebekka; Volonteri, Marta; Wagner, Alexander Y.; Dubois, Yohan

2018-06-01

Feedback by active galactic nuclei (AGNs) is often divided into quasar and radio mode, powered by radiation or radio jets, respectively. Both are fundamental in galaxy evolution, especially in late-type galaxies, as shown by cosmological simulations and observations of jet-ISM (interstellar medium) interactions in these systems. We compare AGN feedback by radiation and by collimated jets through a suite of simulations, in which a central AGN interacts with a clumpy, fractal galactic disc. We test AGNs of 1043 and 1046 erg s-1, considering jets perpendicular or parallel to the disc. Mechanical jets drive the more powerful outflows, exhibiting stronger mass and momentum coupling with the dense gas, while radiation heats and rarefies the gas more. Radiation and perpendicular jets evolve to be quite similar in outflow properties and effect on the cold ISM, while inclined jets interact more efficiently with all the disc gas, removing the densest 20 {per cent} in 20 Myr, and thereby reducing the amount of cold gas available for star formation. All simulations show small-scale inflows of 0.01-0.1 M⊙ yr-1, which can easily reach down to the Bondi radius of the central supermassive black hole (especially for radiation and perpendicular jets), implying that AGNs modulate their own duty cycle in a feedback/feeding cycle.

Identifying Luminous AGN in Deep Surveys: Revised IRAC Selection Criteria

NASA Astrophysics Data System (ADS)

Donley, Jennifer; Koekemoer, A. M.; Brusa, M.; Capak, P.; Cardamone, C. N.; Civano, F.; Ilbert, O.; Impey, C. D.; Kartaltepe, J.; 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. The AGN selection wedges currently in use, however, 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)>44, the new IRAC criteria recover 75% of the hard X-ray and IRAC-detected XMM-COSMOS sample, yet only 37% of the IRAC AGN candidates have X-ray counterparts, a fraction that rises to 51% in regions with Chandra exposures of 50-160 ks. X-ray stacking of the individually X-ray non-detected AGN candidates leads to a hard X-ray signal indicative of heavily obscured to mildly Compton-thick obscuration (log NH >= 23.7). While IRAC selection recovers a substantial fraction of luminous unobscured and obscured AGN, it is incomplete to low-luminosity and host-dominated AGN.

NuSTAR constraints on coronal cutoffs in Swift-BAT selected Seyfert 1 AGN

NASA Astrophysics Data System (ADS)

Kamraj, Nikita; Harrison, Fiona; Balokovic, Mislav; Brightman, Murray; Stern, Daniel

2017-08-01

The continuum X-ray emission from Active Galactic Nuclei (AGN) is believed to originate in a hot, compact corona above the accretion disk. Compton upscattering of UV photons from the inner accretion disk by coronal electrons produces a power law X-ray continuum with a cutoff at energies determined by the electron temperature. The NuSTAR observatory, with its high sensitivity in hard X-rays, has enabled detailed broadband modeling of the X-ray spectra of AGN, thereby allowing tight constraints to be placed on the high-energy cutoff of the X-ray continuum. Recent detections of low cutoff energies in Seyfert 1 AGN in the NuSTAR band have motivated us to pursue a systematic search for low cutoff candidates in Swift-BAT detected Seyfert 1 AGN that have been observed with NuSTAR. We use our constraints on the cutoff energy to map out the location of these sources on the compactness - temperature diagram for AGN coronae, and discuss the implications of low cutoff energies for the cooling and thermalization mechanisms in the corona.

Optical variability properties of the largest AGN sample observed with Kepler/K2

NASA Astrophysics Data System (ADS)

Aranzana, E.; Koerding, E.; Uttley, P.; Scaringi, S.; Steven, B.

2017-10-01

We present the first short time-scale ( hours to days) optical variability study of a large sample of Active Galactic Nuclei (AGN) observed with the Kepler/K2 mission. The sample contains 275 AGN observed over four campaigns with ˜30-minute cadence selected from the Million Quasar Catalogue with R magnitude < 19. We performed time series analysis to determine their variability properties by means of the power spectral densities (PSDs) and applied Monte Carlo techniques to find the best model parameters that fit the observed power spectra. A power-law model is sufficient to describe all the PSDs of the AGN in our sample. The average power-law slope is 2.5±0.5, steeper than the PSDs observed in X-rays, and the rest-frame amplitude variability in the frequency range of 6×10^{-6}-10^{-4} Hz varies from 1-10 % with an average of 2.6 %. We explore correlations between the variability amplitude and key parameters of the AGN, finding a significant correlation of rest-frame short-term variability amplitude with redshift, but no such correlation with luminosity. We attribute these effects to the known 'bluer when brighter variability of quasars combined with the fixed bandpass of Kepler. This study enables us to distinguish between Seyferts and Blazar and confirm AGN candidates.

AGN neutrino flux estimates for a realistic hybrid model

NASA Astrophysics Data System (ADS)

Richter, S.; Spanier, F.

2018-07-01

Recent reports of possible correlations between high energy neutrinos observed by IceCube and Active Galactic Nuclei (AGN) activity sparked a burst of publications that attempt to predict the neutrino flux of these sources. However, often rather crude estimates are used to derive the neutrino rate from the observed photon spectra. In this work neutrino fluxes were computed in a wide parameter space. The starting point of the model was a representation of the full spectral energy density (SED) of 3C 279. The time-dependent hybrid model that was used for this study takes into account the full pγ reaction chain as well as proton synchrotron, electron-positron-pair cascades and the full SSC scheme. We compare our results to estimates frequently used in the literature. This allows to identify regions in the parameter space for which such estimates are still valid and those in which they can produce significant errors. Furthermore, if estimates for the Doppler factor, magnetic field, proton and electron densities of a source exist, the expected IceCube detection rate is readily available.

Delayed or No Feedback? Gas Outflows in Type 2 AGNs. III

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woo, Jong-Hak; Son, Donghoon; Bae, Hyun-Jin, E-mail: woo@astro.snu.ac.kr, E-mail: hjbae@galaxy.yonsei.ac.kr

2017-04-20

We present gas kinematics based on the [O iii] λ 5007 line and their connection to galaxy gravitational potential, active galactic nucleus (AGN) energetics, and star formation, using a large sample of ∼110,000 AGNs and star-forming (SF) galaxies at z < 0.3. Gas and stellar velocity dispersions are comparable to each other in SF galaxies, indicating that the ionized gas kinematics can be accounted by the gravitational potential of host galaxies. In contrast, AGNs clearly show non-gravitational kinematics, which is comparable to or stronger than the virial motion caused by the gravitational potential. The [O iii] velocity–velocity dispersion (VVD) diagrammore » dramatically expands toward high values as a function of AGN luminosity, implying that the outflows are AGN-driven, while SF galaxies do not show such a trend. We find that the fraction of AGNs with a signature of outflow kinematics, steeply increases with AGN luminosity and Eddington ratio. In particular, the majority of luminous AGNs presents strong non-gravitational kinematics in the [O iii] profile. AGNs with strong outflow signatures show on average similar specific star formation rates (sSFRs) to those of star-forming galaxies. In contrast, AGNs with weak or no outflows have an order of magnitude lower sSFRs, suggesting that AGNs with current strong outflows do now show any negative AGN feedback and that it may take dynamical time to impact on star formation over galactic scales.« less

Poynting Robertson Battery and the Chiral Magnetic Fields of AGN Jets

NASA Technical Reports Server (NTRS)

Kazanas, Demosthenes

2010-01-01

We propose that the magnetic fields in the accretion disks of active galactic nuclei (AGNs) are generated by azimuthal electric currents due to the difference between the plasma electron and ion velocities that arises when the electrons are retarded by interactions with the AGN photons (the Poynting Robertson battery). This process provides a unique relation between the polarity of the poloidal B field to the angular velocity Omega of the accretion disk (B is parallel to Omega), a relation absent in the more popular dynamo B-field generation. This then leads to a unique direction for the toroidal B field induced by disk rotation. Observations of the toroidal fields of 29 AGN jets revealed by parsec-scale Faraday rotation measurements show a clear asymmetry that is consistent with this model, with the probability that this asymmetry comes about by chance being approx.0.06 %. This lends support to the hypothesis that the universe is seeded by B fields that are generated in AGNs via this mechanism and subsequently injected into intergalactic space by the jet outflows.

Revisiting the `forbidden' region: AGN radiative feedback with radiation trapping

NASA Astrophysics Data System (ADS)

Ishibashi, W.; Fabian, A. C.; Ricci, C.; Celotti, A.

2018-06-01

Active galactic nucleus (AGN) feedback, driven by radiation pressure on dust, is an important mechanism for efficiently coupling the accreting black hole to the surrounding environment. Recent observations confirm that X-ray selected AGN samples respect the effective Eddington limit for dusty gas in the plane defined by the observed column density versus the Eddington ratio, the so-called NH - λ plane. A `forbidden' region occurs in this plane, where obscuring clouds cannot be long-lived, due to the action of radiation pressure on dust. Here we compute the effective Eddington limit by explicitly taking into account the trapping of reprocessed radiation (which has been neglected in previous works), and investigate its impact on the NH - λ plane. We show that the inclusion of radiation trapping leads to an enhanced forbidden region, such that even Compton-thick material can potentially be disrupted by sub-Eddington luminosities. We compare our model results to the most complete sample of local AGNs with measured X-ray properties, and find good agreement. Considering the anisotropic emission from the accretion disc, we also expect the development of dusty outflows along the polar axis, which may naturally account for the polar dust emission recently detected in several AGNs from mid-infrared observations. Radiative feedback thus appears to be the key mechanism regulating the obscuration properties of AGNs, and we discuss its physical implications in the context of co-evolution scenarios.

Internal Kinematics of AGN Hosts

NASA Astrophysics Data System (ADS)

Masegosa, Josefa; Márquez, Isabel; Durret, Florence; DEGAS Consortium

In order to understand the fueling mechanism to power AGNs, a large effort has been done by the DEGAS (Dynamics and nuclear Engine of GAlaxies of Spiral type) consortium to collect the necessary observational material. We defined an AGN sample which is not contaminated by interacting galaxies and a control sample made of normal spirals with the same properties than the AGN sample, i.e. luminosity and redshift distribution, morphology and percentage of bars. In total we have analyzed a sample of 17 active galaxies and 16 normal spirals. All the galaxies are isolated with the following criteria: not having a companion within 0.4 Mpc and cz < 500 km/s. We want to stress this aspect of our sample, since claimed differences between active and normal galaxies (Knapen et al. 2000) disappear when the samples are decontaminated of interacting systems.

Pinpointing the base of the AGN jets through general relativistic X-ray reverberation studies

NASA Astrophysics Data System (ADS)

Emmanoulopoulos, D.

2015-03-01

Many theoretical models of Active Galactic Nuclei (AGN) predict that the X-ray corona, lying above the black hole, constitutes the base of the X-ray jet. Thus, by studying the exact geometry of the close black hole environment, we can pinpoint the launching site of the jet. Detection of negative X-ray reverberation time delays (i.e. soft band X-ray variations lagging behind the corresponding hard band X-ray variations) can yield significant information about the geometrical properties of the AGN, such as the location of the X-ray source, as well as the physical properties of the the black hole, such as its mass and spin. In the frame-work of the lamp-post geometry, I present the first systematic X-ray time-lag modelling results of an ensemble of 12 AGN, using a fully general relativistic (GR) ray tracing approach for the estimation of the systems' response functions. By combing these state-of-the art GR response models with statistically innovative fitting routines, I derive the geometrical layout of the close BH environment for each source, unveiling the position of the AGN jet-base.

Studying AGN Jets At Extreme Angular Resolution

NASA Astrophysics Data System (ADS)

Bruni, Gabriele

2016-10-01

RadioAstron is a 10m antenna orbiting on the Russian Speckt-R spacecraft, launched in 2011. Performing radio interferometry with a global array of ground telescopes, it is providing record angular resolution. The Key Science Project on AGN polarization is exploiting it to study in great detail the configuration of magnetic fields in AGN jets, and understand their formation and collimation. To date, the project has already achieved the highest angular resolution image ever obtained in Astronomy, and detected brightness temperatures exceeding the ones predicted by theory of AGN.

The host galaxies of ultra hard X-ray selected AGN

NASA Astrophysics Data System (ADS)

Koss, Michael J.

One of the great mysteries surrounding active galactic nuclei (AGN) is their triggering mechanism. Since the discovery that almost all massive galaxies host nuclear supermassive black holes, it has become clear that a trigger mechanism is required to 'turn on' and continue to fuel the central black hole. While it is established that accretion processes are responsible for the energy emitted, the source of the accreting material is still controversial. Furthermore, the energy input from phases of black hole growth is thought to be a key regulator in the formation of galaxies and the establishment of various scaling relations. Theorists often invoke galaxy mergers as the violent mechanism to drive gas into the central regions and ignite luminous quasars, but among more common moderate luminosity AGN, there has been great controversy whether secular processes or mergers dominate AGN fueling. A survey in the ultra hard X-ray band (14--195 keV) is an important new way to answer the fundamental question of AGN fueling. This method is independent of selection effects such as dust extinction and obscuration that plague surveys at other wavelengths because of the ability of the primary continuum to easily pass through large columns of obscuring gas and dust (<10 24 cm-2). In this PhD, we have assembled the largest sample of ultra hard X-ray selected AGN with host galaxy optical data to date, with 185 nearby (z<0.05), moderate luminosity AGN from the Swift BAT sample. We find that these AGN show much higher rates of both mergers and massive spirals suggesting both mergers and accretion of cold gas in late type systems are important in AGN fueling. We also find that the most common AGN survey technique, optical line diagnostics, is heavily biased against finding AGN in mergers or spirals. Finally, in agreement with the merger driven AGN link, we find that dual AGN systems may be more common than current observation suggest since some of them are only detected using high

Fermi-LAT observation of nonblazar AGNs

NASA Astrophysics Data System (ADS)

Sahakyan, N.; Baghmanyan, V.; Zargaryan, D.

2018-06-01

Context. Fermi Large Area Telescope (Fermi-LAT) has recently detected γ-ray emission from active galactic nuclei (AGN) that do not show clear evidence for optical blazar characteristics or have jets pointing away from the observer (nonblazar AGNs). These are interesting γ-ray emitters providing an alternative approach to studying high energy emission processes. Aims: This paper investigates the spectral and temporal properties of γ-ray emission from nonblazar AGNs using the recent Fermi-LAT observational data. Methods: The data collected by Fermi-LAT during 2008-2015, from the observations of 26 nonblazar AGNs, including 11 Fanaroff-Riley Type I (FRI) and ten FRII radio galaxies and steep spectrum radio quasars (SSRQs) and five narrow line seyfert 1s (NLSy1s) are analysed using the new PASS 8 event selection and instrument response function. Possible spectral changes above GeV energies are investigated with a detailed spectral analysis. Light curves generated with normal and adaptive time bins are used to study the γ-ray flux variability. Results: Non-blazar AGNs have a γ-ray photon index in the range of 1.84-2.86 and a flux varying from a few times 10-9 photon cm-2 s-1 to 10-7 photon cm-2 s-1. Over long time periods, the power law provides an adequate description of the γ-ray spectra of almost all sources. Significant curvature is observed in the γ-ray spectra of NGC 1275, NGC 6251, SBS 0846 + 513, and PMN J0948 + 0022 and their spectra are better described by log parabola or by the power law with exponential cut-off models. The γ-ray spectra of PKS 0625-25 and 3C 380 show a possible deviation from a simple power-law shape, indicating a spectral cut-off around the observed photon energy of Ecut = 131.2 ± 88.04 GeV and Ecut = 55.57 ± 50.74 GeV, respectively. Our analysis confirms the previous finding of an unusual spectral turnover in the γ-ray spectrum of Cen A: the photon index changes from Γ = 2.75 ± 0.02 to 2.31 ± 0.1 at 2.35 ± 0.08 GeV. In the �

Massive Molecular Outflows and Evidence for AGN Feedback from CO Observations

DTIC Science & Technology

2014-01-01

19 J. J. Thomson Avenue, Cambridge CB3 0HE, UK e-mail: c.cicone@mrao.cam.ac.uk 2 Kavli Institute for Cosmology , University of Cambridge, Madingley...about 25 arcsec from the galactic centre (corresponding to 1.6 kpc with the cosmology adopted in this paper). The CO(1–0) integrated flux in this com...power of the molecular outflow as a function of AGN luminosity. Theoretical models of AGN feedback and cosmological simulations predict a coupling effi

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

NASA Astrophysics Data System (ADS)

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.

Characterisation of a candidate dual AGN

NASA Astrophysics Data System (ADS)

Lena, D.; Panizo-Espinar, G.; Jonker, P. G.; Torres, M.; Heida, M.

2018-05-01

We present Chandra and optical observations of a candidate dual AGN discovered serendipitously while searching for recoiling black holes via a cross-correlation between the serendipitous XMM source catalog (2XMMi) and SDSS-DR7 galaxies with a separation no larger than ten times the sum of their Petrosian radii. The system has a stellar mass ratio M1/M2 ≈ 0.7. One of the galaxies (Source 1) shows clear evidence for AGN activity in the form of hard X-ray emission and optical emission-line diagnostics typical of AGN ionisation. The nucleus of the other galaxy (Source 2) has a soft X-ray spectrum, bluer colours, and optical emission line ratios dominated by stellar photoionisation with a "composite" signature, which might indicate the presence of a weak AGN. When plotted on a diagram with X-ray luminosity vs [OIII] luminosity both nuclei fall within the locus defined by local Seyfert galaxies. From the optical spectrum we estimate the electron densities finding n1 < 27 e- cm-3 and n2 ≈ 200 e- cm-3. From a 2D decomposition of the surface brightness distribution we infer that both galaxies host rotationally supported bulges (Sersic index <1). While the active nature of Source 1 can be established with confidence, whether the nucleus of Source 2 is active remains a matter of debate. Evidence that a faint AGN might reside in its nucleus is, however, tantalising.

Characterization of a candidate dual AGN

NASA Astrophysics Data System (ADS)

Lena, D.; Panizo-Espinar, G.; Jonker, P. G.; Torres, M. A. P.; Heida, M.

2018-07-01

We present Chandra and optical observations of a candidate dual active galactic nucleus (AGN) discovered serendipitously while searching for recoiling black holes via a cross-correlation between the serendipitous XMM source catalogue (2XMMi) and SDSS-DR7 galaxies with a separation no larger than 10 times the sum of their Petrosian radii. The system has a stellar mass ratio M1/M2 ≈ 0.7. One of the galaxies (Source 1) shows clear evidence for AGN activity in the form of hard X-ray emission and optical emission-line diagnostics typical of AGN ionization. The nucleus of the other galaxy (Source 2) has a soft X-ray spectrum, bluer colours, and optical emission-line ratios dominated by stellar photoionization with a `composite' signature, which might indicate the presence of a weak AGN. When plotted on a diagram with X-ray luminosity versus [OIII] luminosity, both nuclei fall within the locus defined by local Seyfert galaxies. From the optical spectrum, we estimate the electron densities finding n1 < 27 e- cm-3 and n2 ≈ 200 e- cm-3. From a 2D decomposition of the surface brightness distribution, we infer that both galaxies host rotationally supported bulges (Sérsic index <1). While the active nature of Source 1 can be established with confidence, whether the nucleus of Source 2 is active remains a matter of debate. Evidence that a faint AGN might reside in its nucleus is, however, tantalizing.

Impact of an AGN featureless continuum on estimation of stellar population properties

NASA Astrophysics Data System (ADS)

Cardoso, Leandro S. M.; Gomes, Jean Michel; Papaderos, Polychronis

2017-08-01

The effect of the featureless power-law (PL) continuum of an active galactic nucleus (AGN) on the estimation of physical properties of galaxies with optical population spectral synthesis (PSS) remains largely unknown. With the goal of a quantitative examination of this issue, we fit synthetic galaxy spectra representing a wide range of galaxy star formation histories (SFHs) and including distinct PL contributions of the form Fν ∝ ν- α with the PSS code Starlight to study to which extent various inferred quantities (e.g. stellar mass, mean age, and mean metallicity) match the input. The synthetic spectral energy distributions (SEDs) computed with our evolutionary spectral synthesis code include an AGN PL component with 0.5 ≤ α ≤ 2 and a fractional contribution 0.2 ≤ xAGN ≤ 0.8 to the monochromatic flux at 4020 Å. At the empirical AGN detection threshold xAGN ≃ 0.26 that we previously inferred in a pilot study on this subject, our results show that the neglect of a PL component in spectral fitting can lead to an overestimation by 2 dex in stellar mass and by up to 1 and 4 dex in the light- and mass-weighted mean stellar age, respectively, whereas the light- and mass-weighted mean stellar metallicity are underestimated by up to 0.3 and 0.6 dex, respectively. These biases, which become more severe with increasing xAGN, are essentially independent of the adopted SFH and show a complex behaviour with evolutionary time and α. Other fitting set-ups including either a single PL or multiple PLs in the base reveal, on average, much lower unsystematic uncertainties of the order of those typically found when fitting purely stellar SEDs with stellar templates, however, reaching locally up to 1, 3 and 0.4 dex in mass, age and metallicity, respectively. Our results underscore the importance of an accurate modelling of the AGN spectral contribution in PSS fits as a minimum requirement for the recovery of the physical and evolutionary properties of stellar

Lyman continuum leaking AGN in the SSA22 field

NASA Astrophysics Data System (ADS)

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

2017-02-01

Subaru/SuprimeCam narrow-band photometry of the SSA22 field reveals the presence of four Lyman continuum (LyC) candidates among a sample of 14 active galactic nuclei (AGNs). Two show offsets and likely have stellar LyCin 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 2 lower than values obtained assuming fesc = 1. Comparing to recent Ly α forest measurements, AGNs at redshift z ˜ 3 make up at most ˜12 per cent and as little as ˜5 per cent of the total ionizing budget. Our results suggest that AGNs are unlikely to dominate the ionization budget of the Universe at high redshifts.

The redshift evolution of major merger triggering of luminous AGNs: a slight enhancement at z ˜ 2

NASA Astrophysics Data System (ADS)

Hewlett, Timothy; Villforth, Carolin; Wild, Vivienne; Mendez-Abreu, Jairo; Pawlik, Milena; Rowlands, Kate

2017-09-01

Active galactic nuclei (AGNs), particularly the most luminous AGNs, are commonly assumed to be triggered through major mergers; however, observational evidence for this scenario is mixed. To investigate any influence of galaxy mergers on AGN triggering and luminosities through cosmic time, we present a sample of 106 luminous X-ray-selected type 1 AGNs from the COSMOS survey. These AGNs occupy a large redshift range (0.5 < z < 2.2) and two orders of magnitude in X-ray luminosity (˜1043-1045 erg s-1). AGN hosts are carefully mass and redshift matched to 486 control galaxies. A novel technique for identifying and quantifying merger features in galaxies is developed, subtracting galfit galaxy models and quantifying the residuals. Comparison to visual classification confirms this measure reliably picks out disturbance features in galaxies. No enhancement of merger features with increasing AGN luminosity is found with this metric, or by visual inspection. We analyse the redshift evolution of AGNs associated with galaxy mergers and find no merger enhancement in lower redshift bins. Contrarily, in the highest redshift bin (z ˜ 2) AGNs are ˜4 times more likely to be in galaxies exhibiting evidence of morphological disturbance compared to control galaxies, at 99 per cent confidence level (˜2.4σ) from visual inspection. Since only ˜15 per cent of these AGNs are found to be in morphologically disturbed galaxies, it is implied that major mergers at high redshift make a noticeable but subdominant contribution to AGN fuelling. At low redshifts, other processes dominate and mergers become a less significant triggering mechanism.

Is Black Hole Growth a Universal Process? Exploring Selection Effects in Measurements of AGN Accretion Rates and Host Galaxies.

NASA Astrophysics Data System (ADS)

Jones, Mackenzie

2018-01-01

At the center of essentially every massive galaxy is a monstrous black hole producing luminous radiation driven by the accretion of gas. By observing these active galactic nuclei (AGN) we may trace the growth of black holes across cosmic time. However, our knowledge of the full underlying AGN population is hindered by complex observational biases. My research aims to untangle these biases by using a novel approach to simulate the impact of selection effects on multiwavelength observations.The most statistically powerful studies of AGN to date come from optical spectroscopic surveys, with some reporting a complex relationship between AGN accretion rates and host galaxy characteristics. However, the optical waveband can be strongly influenced by selection effects and dilution from host galaxy star formation. I have shown that accounting for selection effects, the Eddington ratio distribution for optically-selected AGN is consistent with a broad power-law, as seen in the X-rays (Jones et al. 2016). This suggests that a universal Eddington ratio distribution may be enough to describe the full multiwavelength AGN population.Building on these results, I have expanded a semi-numerical galaxy formation simulation to include this straightforward prescription for AGN accretion and explicitly model selection effects. I have found that a simple model for AGN accretion can broadly reproduce the host galaxies and halos of X-ray AGN, and that different AGN selection techniques yield samples with very different host galaxy properties (Jones et al. 2017). Finally, I will discuss the capabilities of this simulation to build synthetic multiwavelength SEDs in order to explore what AGN populations would be detected with the next generation of observatories. This research is supported by a NASA Jenkins Graduate Fellowship under grant no. NNX15AU32H.

The invisible AGN catalogue: a mid-infrared-radio selection method for optically faint active galactic nuclei

NASA Astrophysics Data System (ADS)

Truebenbach, Alexandra E.; Darling, Jeremy

2017-06-01

A large fraction of active galactic nuclei (AGN) are 'invisible' in extant optical surveys due to either distance or dust-obscuration. The existence of this large population of dust-obscured, infrared (IR)-bright AGN is predicted by models of galaxy-supermassive black hole coevolution and is required to explain the observed X-ray and IR backgrounds. Recently, IR colour cuts with Wide-field Infrared Survey Explorer have identified a portion of this missing population. However, as the host galaxy brightness relative to that of the AGN increases, it becomes increasingly difficult to differentiate between IR emission originating from the AGN and from its host galaxy. As a solution, we have developed a new method to select obscured AGN using their 20-cm continuum emission to identify the objects as AGN. We created the resulting invisible AGN catalogue by selecting objects that are detected in AllWISE (mid-IR) and FIRST (20 cm), but are not detected in SDSS (optical) or 2MASS (near-IR), producing a final catalogue of 46 258 objects. 30 per cent of the objects are selected by existing selection methods, while the remaining 70 per cent represent a potential previously unidentified population of candidate AGN that are missed by mid-IR colour cuts. Additionally, by relying on a radio continuum detection, this technique is efficient at detecting radio-loud AGN at z ≥ 0.29, regardless of their level of dust obscuration or their host galaxy's relative brightness.

Reverberation Mapping of AGN Accretion Disks

NASA Astrophysics Data System (ADS)

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.

Dynamics and formation of obscuring tori in AGNs

NASA Astrophysics Data System (ADS)

Bannikova, Elena Yu.; Sergeyev, Alexey V.

2017-12-01

We considered the evolution of a self-gravitating clumpy torus in the gravitational field of the central mass of an active galactic nucleus (AGN) in the framework of the N-body problem. The initial conditions take into account winds with different opening angles. Results of our N-body simulations show that the clouds moving on orbits with a spread in inclinations and eccentricities form a toroidal region. This mechanism can solve the problem of the geometrical thickness of the torus. The velocity of the clouds at the inner edge of the torus is lower than in a disk model that can explain the observed rotation curves. We discuss the scenario of torus formation related with the beginning of the AGN stage.

FOUR DUAL AGN CANDIDATES OBSERVED WITH THE VLBA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gabányi, K. É.; Frey, S.; An, T.

According to hierarchical structure formation models, merging galaxies are expected to be seen in different stages of coalescence. However, there are currently no straightforward observational methods to either select or to confirm a large number of dual active galactic nucleus (AGN) candidates. Most attempts involve obtaining a better understanding of double-peaked narrow emission line sources, in order to distinguish the objects for which the emission lines originate from narrow-line kinematics or jet-driven outflows, from those which might harbor dual AGNs. We observed four such candidate sources with the Very Long Baseline Array (VLBA), at 1.5 GHz with a ∼10 masmore » angular resolution, for which the spectral profiles of AGN optical emission suggested the existence of dual AGNs. In SDSS J210449.13–000919.1 and SDSS J23044.82–093345.3 the radio structures are aligned with the optical emission features, thus the double-peaked emission lines might be the results of jet-driven outflows. In the third detected source SDSS J115523.74+150756.9, the radio structure is less extended and is oriented nearly perpendicular to the position angle derived from optical spectroscopy. The fourth source remained undetected with the VLBA, but it was imaged with the Very Large Array at arcsec resolution a few months before our observations, suggesting the existence of an extended radio structure. We did not detect two radio-emitting cores in any of the four sources, a convincing signature of duality.« less

Continuum Reverberation Mapping of AGN Accretion Disks

NASA Astrophysics Data System (ADS)

Fausnaugh, Michael M.; Peterson, Bradley M.; Starkey, David A.; Horne, Keith; AGN Storm Collaboration

2017-12-01

We show recent detections of inter-band continuum lags in three AGN (NGC 5548, NGC 2617, and MCG+08-11-011), which provide new constraints on the temperature profiles and absolute sizes of the accretion disks. We find lags larger than would be predicted for standard geometrically thin, optically thick accretion disks by factors of 2.3 to 3.3. For NGC 5548, the data span UV through optical/near-IR wavelengths, and we are able to discern a steeper temperature profile than the T˜ R^{-3/4} expected for a standard thin disk . Using a physical model, we are also able to estimate the inclinations of the disks for two objects. These results are similar to those found from gravitational microlensing of strongly lensed quasars, and provide a complementary approach for investigating the accretion disk structure in local, low luminsoity AGN.

Correlating The Star Formation Histories Of MaNGA Galaxies With Their Past AGN Activity

NASA Astrophysics Data System (ADS)

Gonzalez Ortiz, Andrea

2017-01-01

We investigate active galactic nuclei (AGN) as a primary mechanism affecting star formation in MaNGA galaxies. Using the Pipe3D code, we modeled the stellar population from MaNGA spectra and derived the star formation histories of 53 AGN host galaxies. We seek to compare the star formation histories of the host galaxies of AGN with the ages of their radio lobes to better understand the role of AGN feedback in the star formation histories of MaNGA galaxies. MaNGA (Mapping Nearby Galaxies at APO) is one of the three core programs in the fourth generation Sloan Digital Sky Survey(SDSS). MaNGA will investigate the internal kinematics of nearly 10,000 local galaxies through dithered observations using fiber integral field units (IFUs) that vary in diameter from 12" (19 fibers) to 32" (127 fibers). In this poster, we present initial results on the star formation histories of MaNGA AGN host galaxies. This work was supported by the SDSS Research Experience for Undergraduates program, which is funded by a grant from Sloan Foundation to the Astrophysical Research Consortium.

One leptoquark to unify them? Neutrino masses and unification in the light of (g - 2)μ, R D (⋆) and RK anomalies

NASA Astrophysics Data System (ADS)

Popov, Oleg; White, G. A.

2017-10-01

Leptoquarks have been proposed as a possible explanation of anomalies in B bar ↦D* τ ν bar decays, the apparent anomalies in (g - 2) μ experiments and a violation of lepton universality. Motivated by this, we examine other motivations of leptoquarks: radiatively induced neutrino masses in the presence of a discrete symmetry that prevents a tree level see-saw mechanism, gauge coupling unification, and vacuum stability at least up to the unification scale. We present a new model for radiatively generating a neutrino mass which can significantly improve gauge coupling unification at one loop. We discuss this, and other models in the light of recent work on flavour anomalies.

The remarkable AGN jets

NASA Astrophysics Data System (ADS)

Komissarov, Serguei

The jets from active galactic nuclei exhibit stability which seems to be far superior compared to that of terrestrial and laboratory jets. They manage to propagate over distances up to a billion of initial jet radii. Yet this may not be an indication of some exotic physics but mainly a reflection of the specific environment these jets propagate through. The key property of this environment is a rapid decline of density and pressure along the jet, which promotes its rapid expansion. Such an expansion can suppress global instabilities, which require communication across the jet, and hence ensure its survival over huge distances. At kpc scales, some AGN jets do show signs of strong instabilities and even turn into plumes. This could be a result of the flattening of the external pressure distribution in their host galaxies or inside the radio lobes. In this regard, we discuss the possible connection between the stability issue and the Fanaroff-Riley classification of extragalactic radio sources. The observations of AGN jets on sub-kpc scale do not seem to support their supposed lack of causal connectivity. When interpreted using simple kinematic models, they reveal a rather perplexing picture with more questions than answers on the jets dynamics.

Seeing Through the Clouds: AGN Geometry with the Swift BAT Sample

NASA Astrophysics Data System (ADS)

Glikman, Eilat; Urry, M.; Schawinski, K.; Koss, M. J.; Winter, L. M.; Elitzur, M.; Wilkin, W. H.

2011-01-01

We investigate the intrinsic structure of the clouds surrounding AGN which give rise to their X-ray and optical emission properties. Using a complete sample of Swift BAT AGN selected in hard X-rays (14-195 keV), which is unbiased with respect to obscuration and extinction, we compute the reddening in the broad line region along the line of sight to the nucleus of each source using Balmer decrement from the ratio of the broad components of H-alpha/H-beta. We compare reddening from dust in the broad line clouds to the hydrogen column density (NH) obtained from their X-ray spectra. The distribution of the gas-to-dust ratios over many lines of sight allow us to test models of AGN structure and probe the immediate environment of the accreting supermassive black holes.

The Search for AGN in Dusty Star Forming Hosts with JWST

NASA Astrophysics Data System (ADS)

Kirkpatrick, Allison; Alberts, Stacey; Pope, Alexandra; Rieke, George; Sajina, Anna

2018-01-01

The bulk of the stellar growth over cosmic time is dominated by IR luminous galaxies at cosmic noon (z=1-2), many of which harbor a hidden active galactic nucleus (AGN). I use state of the art infrared color diagnostics, combining Spitzer and Herschel observations, to separate dust-obscured AGN from dusty star forming galaxies (SFGs) in the CANDELS and COSMOS surveys. I calculate 24 micron counts of SFGs, AGN/star forming "Composites", and AGN. AGN and Composites dominate the counts above 0.8 mJy at 24 micron, and Composites form at least 25% of an IR sample even to faint detection limits. I develop methods to use the Mid-Infrared Instrument (MIRI) on JWST to identify dust-obscured AGN and Composite galaxies from z~1-2. I demonstrate that MIRI color techniques can select AGN with lower Eddington ratios and higher specific SFRs than X-ray techniques alone. JWST/MIRI will enable critical steps forward in identifying and understanding dust-obscured AGN and the link to their host galaxies.

Selecting AGN through Variability in SN Datasets

NASA Astrophysics Data System (ADS)

Boutsia, K.; Leibundgut, B.; Trevese, D.; Vagnetti, F.

2010-07-01

Variability is a main property of Active Galactic Nuclei (AGN) and it was adopted as a selection criterion using multi epoch surveys conducted for the detection of supernovae (SNe). We have used two SN datasets. First we selected the AXAF field of the STRESS project, centered in the Chandra Deep Field South where, besides the deep X-ray surveys also various optical catalogs exist. Our method yielded 132 variable AGN candidates. We then extended our method including the dataset of the ESSENCE project that has been active for 6 years, producing high quality light curves in the R and I bands. We obtained a sample of ˜4800 variable sources, down to R=22, in the whole 12 deg2 ESSENCE field. Among them, a subsample of ˜500 high priority AGN candidates was created using as secondary criterion the shape of the structure function. In a pilot spectroscopic run we have confirmed the AGN nature for nearly all of our candidates.

A Chandra-Swift View of Point Sources in Hickson Compact Groups: High AGN Fraction but a Dearth of Strong AGNs

NASA Astrophysics Data System (ADS)

Tzanavaris, P.; Gallagher, S. C.; Hornschemeier, A. E.; Fedotov, K.; Eracleous, M.; Brandt, W. N.; Desjardins, T. D.; Charlton, J. C.; Gronwall, C.

2014-05-01

We present Chandra X-ray point source catalogs for 9 Hickson Compact Groups (HCGs, 37 galaxies) at distances of 34-89 Mpc. We perform detailed X-ray point source detection and photometry and interpret the point source population by means of simulated hardness ratios. We thus estimate X-ray luminosities (LX ) for all sources, most of which are too weak for reliable spectral fitting. For all sources, we provide catalogs with counts, count rates, power-law indices (Γ), hardness ratios, and LX , in the full (0.5-8.0 keV), soft (0.5-2.0 keV), and hard (2.0-8.0 keV) bands. We use optical emission-line ratios from the literature to re-classify 24 galaxies as star-forming, accreting onto a supermassive black hole (AGNs), transition objects, or low-ionization nuclear emission regions. Two-thirds of our galaxies have nuclear X-ray sources with Swift/UVOT counterparts. Two nuclei have L X, 0.5-8.0 keV >1042 erg s-1, are strong multi-wavelength active galactic nuclei (AGNs), and follow the known αOX-νL ν (nearUV) correlation for strong AGNs. Otherwise, most nuclei are X-ray faint, consistent with either a low-luminosity AGN or a nuclear X-ray binary population, and fall in the "non-AGN locus" in αOX-νL ν (nearUV) space, which also hosts other normal galaxies. Our results suggest that HCG X-ray nuclei in high specific star formation rate spiral galaxies are likely dominated by star formation, while those with low specific star formation rates in earlier types likely harbor a weak AGN. The AGN fraction in HCG galaxies with MR <= -20 and L X, 0.5-8.0 keV >=1041 erg s-1 is 0.08^{+0.35}_{-0.01}, somewhat higher than the ~5% fraction in galaxy clusters.

The ΓX-L/LEdd relation in BAT AGN Spectroscopic Survey (BASS)

NASA Astrophysics Data System (ADS)

Trakhtenbrot, Benny; Ricci, Claudio; Koss, Michael; Schawinski, Kevin; Mushotzky, Richard; Ueda, Yoshihiro; Veilleux, Sylvain; Lamperti, Isabella; Oh, Kyuseok; Treister, Ezequiel; Stern, Daniel; Harrison, Fiona; Balokovic, Mislav

2018-01-01

We present a study of the relation between accretion rate (in terms of L/LEdd) and shape of the hard X-ray spectral energy distribution (namely the photon index Γx) for a large sample of over 200 hard X-ray-selected, low-redshift active galactic nuclei (AGNs), drawn from the Swift/BAT AGN Spectroscopic Survey (BASS). This includes 30 AGNs for which black hole mass (and therefore L/LEdd) is measured directly through masers, spatially resolved gas or stellar dynamics, or reverberation mapping. The high-quality and broad energy coverage of the data provided through BASS allow us to examine several alternative determinations of both Γx and L/LEdd. We find very weak correlation between Γx and L/LEdd for the BASS sample as a whole, with best-fitting relations that are considerably shallower than those reported in previous studies. Moreover, we find no corresponding correlations among the subsets of AGN with different MBH determination methodology, and in particular those AGN with direct or single-epoch MBH estimates. This latter finding is in contrast to several previous studies which focused on z > 0.5 broad-line AGN. We conclude that this tension can be partially accounted for if one adopts a simplified, power-law X-ray spectral model, combined with L/LEdd estimates that are based on the continuum emission and on single-epoch broad-line spectroscopy in the optical regime. Given these findings, we highlight the limitations of using Γx as a probe of supermassive black hole evolution in deep extragalactic X-ray surveys.

Luminous Obscured AGN Unveiled in the Stripe 82 X-ray Survey

NASA Astrophysics Data System (ADS)

LaMassa, Stephanie; Glikman, Eilat; Brusa, Marcella; Rigby, Jane; Tasnim Ananna, Tonima; Stern, Daniel; Lira, Paulina; Urry, Meg; Salvato, Mara; Alexandroff, Rachael; Allevato, Viola; Cardamone, Carolin; Civano, Francesca Maria; Coppi, Paolo; Farrah, Duncan; Komossa, S.; Lanzuisi, Giorgio; Marchesi, Stefano; Richards, Gordon; Trakhtenbrot, Benny; Treister, Ezequiel

2018-01-01

Stripe 82X is a wide-area (30 deg2) X-ray survey overlapping the legacy Sloan Digital Sky Survey (SDSS) Stripe 82 field, designed to uncover rare, high luminosity active galactic nuclei (AGN). We report on the results of an on-going near-infrared (NIR) spectroscopic campaign to follow-up reddened AGN candidates with Palomar TripleSpec, Keck NIRSPEC, and Gemini GNIRS. We identified 8 AGN in our bright NIR sample (K < 16, Vega), selected to have red R-K colors (> 4, Vega); four of these sources had existing optical spectra in SDSS. We targeted four out of 34 obscured AGN candidates in our faint NIR sample (K > 17, Vega), all of which are undetected in the single-epoch SDSS imaging, making them the best candidates for the most obscured and/or the most distant reddend AGN in Stripe 82X. All twelve sources are Type 1 AGN, with the FWHM of at least one permitted emission line exceeding 1300 km/s. We find that our nearly complete bright NIR sample (12/13 obscured AGN candidates have spectroscopic redshifts) is more distant (z > 0.5) than a matched sample of blue Type 1 AGN from Stripe 82X; these AGN tend to be more luminous than their blue, unobscured counterparts. Results from our pilot program of faint NIR-selected obscured AGN candidates demonstrate that our selection recovers reddened quasars missed by SDSS.

Radio Properties of the BAT AGNs: the FIR-radio Relation, the Fundamental Plane, and the Main Sequence of Star Formation

NASA Astrophysics Data System (ADS)

Smith, Krista Lynne; Mushotzky, Richard F.; Vogel, Stuart; Shimizu, Thomas T.; Miller, Neal

2016-12-01

We conducted 22 GHz 1″ JVLA imaging of 70 radio-quiet active galactic nuclei (AGNs) from the Swift-BAT survey. We find radio cores in all but three objects. The radio morphologies of the sample fall into three groups: compact and core-dominated, extended, and jet-like. We spatially decompose each image into core flux and extended flux, and compare the extended radio emission with that predicted from previous Herschel observations using the canonical FIR-radio relation. After removing the AGN contribution to the FIR and radio flux densities, we find that the relation holds remarkably well despite the potentially different star formation physics in the circumnuclear environment. We also compare our core radio flux densities with predictions of coronal models and scale-invariant jet models for the origin of radio emission in radio-quiet AGNs, and find general consistency with both models. However, we find that the L R/L X relation does not distinguish between star formation and non-relativistic AGN-driven outflows as the origin of radio emission in radio-quiet AGNs. Finally, we examine where objects with different radio morphologies fall in relation to the main sequence (MS) of star formation, and conclude that those AGNs that fall below the MS, as X-ray selected AGNs have been found to do, have core-dominated or jet-like 22 GHz morphologies.

VizieR Online Data Catalog: Type 2 AGN host galaxies in Chandra-COSMOS (Suh+, 2017)

NASA Astrophysics Data System (ADS)

Suh, H.; Civano, F.; Hasinger, G.; Lusso, E.; Lanzuisi, G.; Marchesi, S.; Trakhtenbrot, B.; Allevato, V.; Cappelluti, N.; Capak, P. L.; Elvis, M.; Griffiths, R. E.; Laigle, C.; Lira, P.; Riguccini, L.; Rosario, D. J.; Salvato, M.; Schawinski, K.; Vignali, C.

2018-01-01

We investigate the star formation properties of a large sample of ~2300 X-ray-selected Type 2 Active Galactic Nuclei (AGNs) host galaxies out to z~3 in the Chandra COSMOS Legacy Survey in order to understand the connection between the star formation and nuclear activity. Making use of the existing multi-wavelength photometric data available in the COSMOS field, we perform a multi-component modeling from far-infrared to near-ultraviolet using a nuclear dust torus model, a stellar population model and a starburst model of the spectral energy distributions (SEDs). Through detailed analyses of SEDs, we derive the stellar masses and the star formation rates (SFRs) of Type 2 AGN host galaxies. The stellar mass of our sample is in the range of 9AGN host galaxies have, on average, similar SFRs compared to the normal star-forming galaxies with similar Mstellar and redshift ranges, suggesting no significant evidence for enhancement or quenching of star formation. This could be interpreted in a scenario, where the relative massive galaxies have already experienced substantial growth at higher redshift (z>3), and grow slowly through secular fueling processes hosting moderate-luminosity AGNs. (1 data file).

AGN STORM: A Leap Forward In Reverberation Mapping

NASA Astrophysics Data System (ADS)

Dalla Bontà, Elena; AGN STORM Team

2016-10-01

Reverberation mapping is a tomographic technique that can be used to determine the structure and kinematics of the broad- line emitting region at the center of active galactic nuclei. By-products of these investigations are the masses of the central black holes and information about the structure of the accretion disk. I will show some of the most recent results from the AGN Space Telescope and Optical Reverberation Mapping (AGN STORM) project, which was built around 180 daily observations of the bright Seyfert 1 galaxy NGC 5548 with the Cosmic Origins Spectrograph on Hubble Space Telescope. AGN STORM included observations made with Swift, XMM, and several ground-based telescopes, including the 1.22-m telescope at Asiago Observatory. Elena Dalla Bonta` on behalf of the AGN STORM Team.

Effective field theory approach to trans-TeV supersymmetry: covariant matching, Yukawa unification and Higgs couplings

NASA Astrophysics Data System (ADS)

Wells, James D.; Zhang, Zhengkang

2018-05-01

Dismissing traditional naturalness concerns while embracing the Higgs boson mass measurement and unification motivates careful analysis of trans-TeV supersymmetric theories. We take an effective field theory (EFT) approach, matching the Minimal Supersymmetric Standard Model (MSSM) onto the Standard Model (SM) EFT by integrating out heavy superpartners, and evolving MSSM and SMEFT parameters according to renormalization group equations in each regime. Our matching calculation is facilitated by the recent covariant diagrams formulation of functional matching techniques, with the full one-loop SUSY threshold corrections encoded in just 30 diagrams. Requiring consistent matching onto the SMEFT with its parameters (those in the Higgs potential in particular) measured at low energies, and in addition requiring unification of bottom and tau Yukawa couplings at the scale of gauge coupling unification, we detail the solution space of superpartner masses from the TeV scale to well above. We also provide detailed views of parameter space where Higgs coupling measurements have probing capability at future colliders beyond the reach of direct superpartner searches at the LHC.

BAT AGN Spectroscopic Survey - III. An Observed Link Between AGN Eddington Ratio and Narrow-Emission-Line Ratios

NASA Technical Reports Server (NTRS)

Oh, Kyuseok; Schawinski, Kevin; Koss, Michael; Trakhtenbrot, Benny; Lamperti, Isabella; Ricci, Claudio; Mushotzky, Richard; Veilleux, Sylvain; Berney, Simon; Crenshaw, D. Michael;

Dust-deficient Palomar-Green Quasars and the Diversity of AGN Intrinsic IR Emission

NASA Astrophysics Data System (ADS)

Lyu, Jianwei; Rieke, G. H.; Shi, Yong

2017-02-01

To elucidate the intrinsic broadband infrared (IR) emission properties of active galactic nuclei (AGNs), we analyze the spectral energy distributions (SEDs) of 87 z ≲ 0.5 Palomar-Green (PG) quasars. While the Elvis AGN template with a moderate far-IR correction can reasonably match the SEDs of the AGN components in ˜60% of the sample (and is superior to alternatives such as that by Assef), it fails on two quasar populations: (1) hot-dust-deficient (HDD) quasars that show very weak emission thoroughly from the near-IR to the far-IR, and (2) warm-dust-deficient (WDD) quasars that have similar hot dust emission as normal quasars but are relatively faint in the mid- and far-IR. After building composite AGN templates for these dust-deficient quasars, we successfully fit the 0.3-500 μm SEDs of the PG sample with the appropriate AGN template, an infrared template of a star-forming galaxy, and a host galaxy stellar template. 20 HDD and 12 WDD quasars are identified from the SED decomposition, including seven ambiguous cases. Compared with normal quasars, the HDD quasars have AGNs with relatively low Eddington ratios and the fraction of WDD quasars increases with AGN luminosity. Moreover, both the HDD and WDD quasar populations show relatively stronger mid-IR silicate emission. Virtually identical SED properties are also found in some quasars from z = 0.5 to 6. We propose a conceptual model to demonstrate that the observed dust deficiency of quasars can result from a change of structures of the circumnuclear tori that can occur at any cosmic epoch.

The Effect of AGN Heating on the Low-redshift Lyα Forest

NASA Astrophysics Data System (ADS)

Gurvich, Alex; Burkhart, Blakesley; Bird, Simeon

2017-02-01

We investigate the effects of AGN heating and the ultraviolet background on the low-redshift Lyα forest column density distribution (CDD) using the Illustris simulation. We show that Illustris reproduces observations at z = 0.1 in the column density range {10}12.5{--}{10}13.5 cm-2, relevant for the “photon underproduction crisis.” We attribute this to the inclusion of AGN feedback, which changes the gas distribution so as to mimic the effect of extra photons, as well as the use of the Faucher-Giguère ultraviolet background, which is more ionizing at z = 0.1 than the Haardt & Madau background previously considered. We show that the difference between simulations run with smoothed particle hydrodynamics and simulations using a moving mesh is small in this column density range but can be more significant at larger column densities. We further consider the effect of supernova feedback, Voigt profile fitting, and finite resolution, all of which we show to have little influence on the CDD. Finally, we identify a discrepancy between our simulations and observations at column densities {10}14{--}{10}16 cm-2, where Illustris produces too few absorbers, which suggests the AGN feedback model should be further refined. Since the “photon underproduction crisis” primarily affects lower column density systems, we conclude that AGN feedback and standard ionizing background models can resolve the crisis.

Host Galaxy Properties of SWIFT Hard X-ray Selected AGN

NASA Astrophysics Data System (ADS)

Koss, Michael; Mushotzky, R.; Veilleux, S.; Winter, L.

2010-01-01

Surveys of AGN taken in the optical, UV, and soft X-rays miss an important population of obscured AGN only visible in the hard X-rays and mid-IR wavelengths. The SWIFT BAT survey in the hard X-ray range (14-195 keV) has provided a uniquely unbiased sample of 258 AGN unaffected by galactic or circumnuclear absorption. Optical imaging of this unbiased sample provides a new opportunity to understand how the environments of the host galaxies are linked to AGN. In 2008, we observed 110 of these targets at Kitt Peak with the 2.1m in the SDSS ugriz bands over 17 nights. Using these observations and SDSS data we review the relationships between color, morphology, merger activity, star formation, and AGN luminosity.

Liners and Low Luminosity AGN in the ROSAT Database

NASA Technical Reports Server (NTRS)

Elvis, Martin; West, Donald K. (Technical Monitor)

2003-01-01

This program has led to a series of papers being written and published in the Astrophysical Journal. Together these papers try to explain major parts of the LINER and low luminosity AGN puzzle. One paper ('Accretion Disk Instabilities, Cold Dark Matter Models, and Their Role in Quasar Evolution', Hatziminaoglou E., Siemiginowska A., & Elvis M., 2001, ApJ, 547, 90) describes an analytical model for the evolution of the quasar luminosity function. By combining the Press-Schechter formalism for the masses of initial structures with the luminosity distribution for a population of single mass black holes given by an unstable accretion disk an almost complete end-to-end physics-based model of quasar evolution is produced. In this model black holes spend 75% of their time in a low accretion state (at L(Edd)). This low state population of black holes is likely to be observed as the LINER and low luminosity AGNs in the local universe. Another paper ('Broad Emission Line Regions in AGN: the Link with the Accretion Power', Nicastro F., 2000, ApJ Letters, 530, L65) gives a physical basis for why low state black holes appear as LINERS. By linking the Lightman-Eardley instability in an accretion disk to the ori.gin of a wind that contains the broad emission line cloud material this model explains the large widths seen in these lines as being the Keplerian velocity of the disk at the instability radius. For LINERS the key is that below an accretion rate of 10(exp -3)M(sub Edd)the Lightman-Eardley instability falls within the innermost stable orbit of the disk, and so leaves the entire disk stable. No wind occurs, and so no broad emission lines are seen. Most LINERS are likely to be black holes in this low state. Tests of this model are being considered.

LHC phenomenology of natural MSSM with non-universal gaugino masses at the unification scale

NASA Astrophysics Data System (ADS)

Abe, Hiroyuki; Kawamura, Junichiro; Omura, Yuji

2015-08-01

In this letter, we study collider phenomenology in the supersymmetric Standard Model with a certain type of non-universal gaugino masses at the gauge coupling unification scale, motivated by the little hierarchy problem. In this scenario, especially the wino mass is relatively large compared to the gluino mass at the unification scale, and the heavy wino can relax the fine-tuning of the higgsino mass parameter, so-called μ-parameter. Besides, it will enhance the lightest Higgs boson mass due to the relatively large left-right mixing of top squarks through the renormalization group (RG) effect. Then 125 GeV Higgs boson could be accomplished, even if the top squarks are lighter than 1 TeV and the μ parameter is within a few hundreds GeV. The right-handed top squark tends to be lighter than the other sfermions due to the RG runnings, then we focus on the top squark search at the LHC. Since the top squark is almost right-handed and the higgsinos are nearly degenerate, 2 b + E T miss channel is the most sensitive to this scenario. We figure out current and expected experimental bounds on the lightest top squark mass and model parameters at the gauge coupling unification scale.

Mini-Survey of SDSS OIII AGN with Swift

NASA Technical Reports Server (NTRS)

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.

Compton-thick AGNs in the NuSTAR Era

NASA Astrophysics Data System (ADS)

Marchesi, S.; Ajello, M.; Marcotulli, L.; Comastri, A.; Lanzuisi, G.; Vignali, C.

2018-02-01

We present the 2–100 keV spectral analysis of 30 candidate Compton-thick-(CT-)active galactic nuclei (AGNs) selected in the Swift-Burst Alert Telescope (BAT) 100 month survey. The average redshift of these objects is < z> ∼ 0.03, and they all lie within ∼500 Mpc. We used the MyTorus model to perform X-ray spectral fittings both without and with the contribution of the Nuclear Spectroscopic Telescope Array (NuSTAR) data in the 3–50 keV energy range. When the NuSTAR data are added to the fit, 13 out of 30 of these objects (43% of the whole sample) have intrinsic absorption N H < 1024 cm‑2 at the >3σ confidence level, i.e., they are reclassified from Compton thick to Compton thin. Consequently, we infer an overall observed fraction of the CT-AGN, with respect to the whole AGN population, lower than the one reported in previous works, as low as ∼4%. We find evidence that this overestimation of N H is likely due to the low quality of a subsample of spectra, either in the 2–10 keV band or in the Swift-BAT one.

Imaging AGN Feedback in NGC 3393 with CHEERS

NASA Astrophysics Data System (ADS)

Maksym, W. Peter; Fabbiano, Giuseppina; Elvis, Martin; Karovska, Margarita; Paggi, Alessandro; Wang, Junfeng; Storchi-Bergmann, Thaisa

2016-01-01

The CHandra Extended Emission-line Region Survey (CHEERS) is the 'ultimate' resolution X-ray imaging survey of nearby far-IR selected AGN. By comparing deep Chandra observations with complementary HST and radio data, we investigate the morphology of the extended narrow-line region on scales of <100 pc. We present new results on the gas surrounding the compton-thick AGN NGC 3393. The luminous extended narrow-line X-ray emission from this gas allows us to study the role and extent of AGN feedback as sub-kpc jets interact with the surrounding ISM.

Imaging AGN Feedback in NGC 3393 with CHEERS

NASA Astrophysics Data System (ADS)

Paggi, Alessandro; Maksym, W. Peter; Fabbiano, Giuseppina; Elvis, Martin; Karovska, Margarita; Wang, Junfeng; Storchi-Bergmann, Thaisa

2016-04-01

The CHandra Extended Emission-line Region Survey (CHEERS) is the 'ultimate' resolution X-ray imaging survey of nearby far-IR selected AGN. By comparing deep Chandra observations with complementary HST and radio data, we investigate the morphology of the extended narrow-line region on scales of <100 pc. We present new results on the gas surrounding the compton-thick AGN NGC 3393. The luminous extended narrow-line X-ray emission from this gas allows us to study the role and extent of AGN feedback as sub-kpc jets interact with the surrounding ISM.

Spectral-luminosity evolution of active galactic nuclei (AGN)

NASA Technical Reports Server (NTRS)

Leiter, Darryl; Boldt, Elihu

1992-01-01

The origin of the cosmic X-ray and gamma-ray backgrounds is explained via the mechanism of AGN spectral-luminosity evolution. The spectral evolution of precursor active galaxies into AGN, and Newton-Raphson input and output parameters are discussed.

X-ray Properties of the Central kpc of AGN and Starbursts: The Latest News from Chandra

NASA Technical Reports Server (NTRS)

Weaver, Kimberly A.; White, Nicholas E. (Technical Monitor)

2001-01-01

The X-ray properties of 15 nearby (v less than 3,000 km/s) galaxies that possess AGN (active galactic nuclei) and/or starbursts are discussed. Two-thirds have nuclear extended emission on scales from approx. 0.5 to approx. 1.5 kpc that is either clearly associated with a nuclear outflow or morphologically resembles an outflow. Galaxies that are AGN-dominated tend to have linear structures while starburst-dominated galaxies tend to have plume-like structures. Significant X-ray absorption is present in the starburst regions, indicating that a circumnuclear starburst is sufficient to block an AGN at optical wavelengths. Galaxies with starburst activity possess more X-ray point sources within their central kpc than non-starbursts. Many of these sources are more luminous than typical X-ray binaries. The Chandra results are discussed in terms of the starburst-AGN connection, a revised unified model for AGN, and possible evolutionary scenarios.

The Cosmological Impact of AGN Outflows: Measuring Absolute Abundances and Kinetic Luminosities

NASA Astrophysics Data System (ADS)

Arav, Nahum

2009-07-01

AGN outflows are increasingly invoked as a major contributor to the formation and evolution of supermassive black holes, their host galaxies, the surrounding IGM, and cluster cooling flows. Our HST/COS proposal will determine reliable absolute chemical abundances in six AGN outflows, which influences several of the processes mentioned above. To date there is only one such determination, done by our team on Mrk 279 using 16 HST/STIS orbits and 100 ksec of FUSE time. The advent of COS and its high sensitivity allows us to choose among fainter objects at redshifts high enough to preclude the need for FUSE. This will allow us to determine the absolute abundances for six AGN {all fainter than Mrk 279} using only 40 HST COS orbits. This will put abundances studies in AGN on a firm footing, an elusive goal for the past four decades. In addition, prior FUSE observations of four of these targets indicate that it is probable that the COS observations will detect troughs from excited levels of C III. These will allow us to measure the distances of the outflows and thereby determine their kinetic luminosity, a major goal in AGN feedback research. We will use our state of the art column density extraction methods and velocity-dependent photoionization models to determine the abundances and kinetic luminosity. Previous AGN outflow projects suffered from the constraints of deciding what science we could do using ONE of the handful of bright targets that were observable. With COS we can choose the best sample for our experiment. As an added bonus, most of the spectral range of our targets has not been observed previously, greatly increasing the discovery phase space.

RADIO PROPERTIES OF THE BAT AGNs: THE FIR–RADIO RELATION, THE FUNDAMENTAL PLANE, AND THE MAIN SEQUENCE OF STAR FORMATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Krista Lynne; Mushotzky, Richard F.; Vogel, Stuart

We conducted 22 GHz 1″ JVLA imaging of 70 radio-quiet active galactic nuclei (AGNs) from the Swift -BAT survey. We find radio cores in all but three objects. The radio morphologies of the sample fall into three groups: compact and core-dominated, extended, and jet-like. We spatially decompose each image into core flux and extended flux, and compare the extended radio emission with that predicted from previous Herschel observations using the canonical FIR–radio relation. After removing the AGN contribution to the FIR and radio flux densities, we find that the relation holds remarkably well despite the potentially different star formation physics inmore » the circumnuclear environment. We also compare our core radio flux densities with predictions of coronal models and scale-invariant jet models for the origin of radio emission in radio-quiet AGNs, and find general consistency with both models. However, we find that the L {sub R}/ L {sub X} relation does not distinguish between star formation and non-relativistic AGN-driven outflows as the origin of radio emission in radio-quiet AGNs. Finally, we examine where objects with different radio morphologies fall in relation to the main sequence (MS) of star formation, and conclude that those AGNs that fall below the MS, as X-ray selected AGNs have been found to do, have core-dominated or jet-like 22 GHz morphologies.« less

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

NASA Technical Reports Server (NTRS)

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.

AGN-enhanced outflows of low-ionization gas in star-forming galaxies at 1.7 < z < 4.6*

NASA Astrophysics Data System (ADS)

Talia, M.; Brusa, M.; Cimatti, A.; Lemaux, B. C.; Amorin, R.; Bardelli, S.; Cassarà, L. P.; Cucciati, O.; Garilli, B.; Grazian, A.; Guaita, L.; Hathi, N. P.; Koekemoer, A.; Le Fèvre, O.; Maccagni, D.; Nakajima, K.; Pentericci, L.; Pforr, J.; Schaerer, D.; Vanzella, E.; Vergani, D.; Zamorani, G.; Zucca, E.

2017-11-01

Fast and energetic winds are invoked by galaxy formation models as essential processes in the evolution of galaxies. These outflows can be powered either by star formation (SF) and/or active galactic nucleus (AGN) activity, but the relative dominance of the two mechanisms is still under debate. We use spectroscopic stacking analysis to study the properties of the low-ionization phase of the outflow in a sample of 1330 star-forming galaxies (SFGs) and 79 X-ray-detected (1042 < LX < 1045 erg s-1) Type 2 AGN at 1.7 < z < 4.6 selected from a compilation of deep optical spectroscopic surveys, mostly zCOSMOS-Deep and VIMOS Ultra Deep Survey (VUDS). We measure mean velocity offsets of ˜- 150 km s-1 in the SFGs, while in the AGN sample the velocity is much higher (˜- 950 km s-1), suggesting that the AGN is boosting the outflow up to velocities that could not be reached only with the SF contribution. The sample of X-ray AGN has on average a lower SF rate than non-AGN SFGs of similar mass: this, combined with the enhanced outflow velocity in AGN hosts, is consistent with AGN feedback in action. We further divide our sample of AGN into two X-ray luminosity bins: we measure the same velocity offsets in both stacked spectra, at odds with results reported for the highly ionized phase in local AGN, suggesting that the two phases of the outflow may be mixed only up to relatively low velocities, while the highest velocities can be reached only by the highly ionized phase.

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

NASA Astrophysics Data System (ADS)

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.

A Chandra-Swift View of Point Sources in Hickson Compact Groups: High AGN Fraction but a Dearth of Strong AGNs

NASA Technical Reports Server (NTRS)

Tzanavaris, P.; Gallagher, S. C.; Hornschemeier, A. E.; Fedotov, K.; Eracleous, M.; Brandt, W. N.; Desjardins, T. D.; Charlton, J. C.; Gronwall, C.

2014-01-01

We present Chandra X-ray point source catalogs for 9 Hickson Compact Groups (HCGs, 37 galaxies) at distances of 34-89 Mpc. We perform detailed X-ray point source detection and photometry and interpret the point source population by means of simulated hardness ratios. We thus estimate X-ray luminosities (L(sub x)) for all sources, most of which are too weak for reliable spectral fitting. For all sources, we provide catalogs with counts, count rates, power-law indices (gamma), hardness ratios, and L(sub X), in the full (0.5-8.0 keV), soft (0.5-2.0 keV), and hard (2.0-8.0 keV) bands. We use optical emission-line ratios from the literature to re-classify 24 galaxies as star-forming, accreting onto a supermassive black hole (AGNs), transition objects, or low-ionization nuclear emission regions. Two-thirds of our galaxies have nuclear X-ray sources with Swift/UVOT counterparts. Two nuclei have L(sub X),0.5-8.0 keV > 10(exp 42) erg s-1, are strong multi-wavelength active galactic nuclei (AGNs), and follow the known alpha OX-?L? (nearUV) correlation for strong AGNs. Otherwise, most nuclei are X-ray faint, consistent with either a low-luminosity AGN or a nuclear X-ray binary population, and fall in the 'non-AGN locus' in alpha OX-?L? (nearUV) space, which also hosts other normal galaxies. Our results suggest that HCG X-ray nuclei in high specific star formation rate spiral galaxies are likely dominated by star formation, while those with low specific star formation rates in earlier types likely harbor a weak AGN. The AGN fraction in HCG galaxies with MR (is) less than -20 and L(sub X),0.5-8.0 keV (is) greater than 10(exp 41) erg s-1 is 0.08+0.35 -0.01, somewhat higher than the 5% fraction in galaxy clusters.

Modeling the Infrared Reverberation Response of the Circumnuclear Dusty Torus in AGNs: The Effects of Cloud Orientation and Anisotropic Illumination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Almeyda, Triana; Robinson, Andrew; Richmond, Michael

The obscuring circumnuclear torus of dusty molecular gas is one of the major components of active galactic nuclei (AGN). The torus can be studied by analyzing the time response of its infrared (IR) dust emission to variations in the AGN continuum luminosity, a technique known as reverberation mapping. The IR response is the convolution of the AGN ultraviolet/optical light curve with a transfer function that contains information about the size, geometry, and structure of the torus. Here, we describe a new computer model that simulates the reverberation response of a clumpy torus. Given an input optical light curve, the codemore » computes the emission of a 3D ensemble of dust clouds as a function of time at selected IR wavelengths, taking into account light travel delays. We present simulated dust emission responses at 3.6, 4.5, and 30 μ m that explore the effects of various geometrical and structural properties, dust cloud orientation, and anisotropy of the illuminating radiation field. We also briefly explore the effects of cloud shadowing (clouds are shielded from the AGN continuum source). Example synthetic light curves have also been generated, using the observed optical light curve of the Seyfert 1 galaxy NGC 6418 as input. The torus response is strongly wavelength-dependent, due to the gradient in cloud surface temperature within the torus, and because the cloud emission is strongly anisotropic at shorter wavelengths. Anisotropic illumination of the torus also significantly modifies the torus response, reducing the lag between the IR and optical variations.« less

Active galactic nuclei from He II: a more complete census of AGN in SDSS galaxies yields a new population of low-luminosity AGN in highly star-forming galaxies

NASA Astrophysics Data System (ADS)

Bär, Rudolf E.; Weigel, Anna K.; Sartori, Lia F.; Oh, Kyuseok; Koss, Michael; Schawinski, Kevin

2017-04-01

In order to perform a more complete census of active galactic nuclei (AGN) in the local Universe, we investigate the use of the He II λ4685 emission line diagnostic diagram by Shirazi & Brinchmann (2012) in addition to the standard methods based on other optical emission lines. The He II-based diagnostics is more sensitive to AGN ionization in the presence of strong star formation than conventional line diagnostics. We survey a magnitude-limited sample of 63 915 galaxies from the Sloan Digital Sky Survey Data Release 7 at 0.02 < z < 0.05 and use both the conventional BPT emission line diagnostic diagrams, as well as the He II diagram to identify AGN. In this sample, 1075 galaxies are selected as AGN using the BPT diagram, while additional 234 galaxies are identified as AGN using the He II diagnostic diagram, representing a 22 per cent increase of AGN in the parent galaxy sample. We explore the host galaxy properties of these new He II-selected AGN candidates and find that they are most common in star-forming galaxies on the blue cloud and on the main sequence where ionization from star formation is most likely to mask AGN emission in the BPT lines. We note in particular a high He II AGN fraction in galaxies above the high-mass end of the main sequence where quenching is expected to occur. We use archival Chandra observations to confirm the AGN nature of candidates selected through He II-based diagnostic. Finally, we discuss how this technique can help inform galaxy/black hole coevolution scenarios.

Monitoring AGNs with Hbeta Asymmetry with the Wyoming Infra-Red Observatory

NASA Astrophysics Data System (ADS)

Brotherton, Michael S.; Du, Pu; Wang, Jian-Min; Wang, Kai; Huang, Zhengpeng; Hu, Chen; Li, Yan-rong; Kasper, David H.; Chick, William T.; Nguyen, My L.; Maithil, Jaya; Hand, Derek; Bai, Jin-Ming; Ho, Luis

2018-06-01

We present preliminary results from two seasons of reverberation mapping of AGNs using the optical longslit spectrograph on the 2.3 meter WIRO telescope. The majority of the sample is part of our "Monitoring AGNs with Hbeta Asymmetry" project, also known as MAHA, which targets rarer AGNs with extremely asymmetric profiles that may provide new insights into the full diversity of size and structure of the broad-line region (BLR). Our hundreds of nights of telescope time provide dozens of epochs of spectra for approximately two dozen objects. Notably we find that many AGNs with broader asymmetric Hbeta emission lines possess time lags significantly shorter than expected for their luminosity in comparison to the majority of AGNs reverberation mapped.

A complete hard X-ray selected sample of local, luminous AGNs

NASA Astrophysics Data System (ADS)

Burtscher, Leonard; Davies, Ric; Lin, Ming-yi; Orban de Xivry, Gilles; Rosario, David

2016-08-01

Choosing a very well defined sample is essential for studying the AGN phenomenon. Only the most luminous AGNs can be expected to require a coherent feeding mechanism to sustain their activity and since host galaxy properties and AGN activity are essentially uncorrelated, nuclear scales must be resolved in order to shed light on the feeding mechanisms of AGNs. For these reasons we are compiling a sample of the most powerful, local AGNs. In this talk we present our on-going programme to observe a complete volume limited sample of nearby active galaxies selected by their 14-195 keV luminosity, and outline its rationale for studying the mechanisms regulating gas inflow and outflow.

BAT AGN Spectroscopic Survey (BASS) - VI. The ΓX-L/LEdd relation

NASA Astrophysics Data System (ADS)

Trakhtenbrot, Benny; Ricci, Claudio; Koss, Michael J.; Schawinski, Kevin; Mushotzky, Richard; Ueda, Yoshihiro; Veilleux, Sylvain; Lamperti, Isabella; Oh, Kyuseok; Treister, Ezequiel; Stern, Daniel; Harrison, Fiona; Baloković, Mislav; Gehrels, Neil

2017-09-01

We study the relation between accretion rate (in terms of L/LEdd) and shape of the hard X-ray spectral energy distribution (namely the photon index Γx) for a large sample of 228 hard X-ray-selected, low-redshift active galactic nuclei (AGNs), drawn from the Swift/BAT AGN Spectroscopic Survey (BASS). This includes 30 AGNs for which black hole mass (and therefore L/LEdd) is measured directly through masers, spatially resolved gas or stellar dynamics, or reverberation mapping. The high-quality and broad energy coverage of the data provided through BASS allow us to examine several alternative determinations of both Γx and L/LEdd. For the BASS sample as a whole, we find a statistically significant, albeit very weak correlation between Γx and L/LEdd. The best-fitting relations we find, Γx ≃ 0.15 log L/LEdd + const., are considerably shallower than those reported in previous studies. Moreover, we find no corresponding correlations among the subsets of AGN with different MBH determination methodology. In particular, we find no robust evidence for a correlation when considering only those AGN with direct or single-epoch MBH estimates. This latter finding is in contrast to several previous studies which focused on z > 0.5 broad-line AGN. We discuss this tension and conclude that it can be partially accounted for if one adopts a simplified, power-law X-ray spectral model, combined with L/LEdd estimates that are based on the continuum emission and on single-epoch broad-line spectroscopy in the optical regime. We finally highlight the limitations on using Γx as a probe of supermassive black hole evolution in deep extragalactic X-ray surveys.

Tracing the Far-Infrared Roles of AGN in Dusty Star-Forming Galaxies

NASA Astrophysics Data System (ADS)

Brown, Arianna; Nayyeri, Hooshang; Cooray, Asantha R.; Mitchell-Wynne, Ketron

2017-01-01

Active galactic nuclei (AGNs) are suggested to play an important role in quenching their host galaxy’s star formation rate (SFR) by heating up and/or consuming the cool gas necessary to create stars. This mechanism is theorized as a critical step in AGN evolutionary models. The efforts to study this effect suffer in part from low-number statistics at high x-ray luminosities (LXR > 1044 ergs/s) for AGNs at z≈1-3, and a lack of separately estimated SFRs for AGN in dusty, star-forming galaxies (DSFGs). In this work, we extend our analysis to build a more complete picture using the variety of available multi-wavelength data in the XBoötes region. The Chandra XBoötes Survey is a 5-ks X-ray survey of the 9.3 square degree Boötes Field of the NOAO Deep Wide-Field Survey, a survey imaged from the optical to the near-IR. We estimate AGN spectral energy distributions and SFRs for ~400 x-ray sources using available data in all four Spitzer IRAC bands, the Spitzer MIPS 24µm band, all five Herschel SPIRE and PACS bands, along with NEWFIRM optical bands. Preliminary results show an exponential correlation between x-ray luminosity and star formation. As a comparison, we will use a stacking technique for the ~500 x-ray sources that were not detected at submillimeter wavelengths, where sources are binned by x-ray luminosity. We will compare these two samples and expect to see a difference in slope. Using these techniques, we hope to place tighter constraints on the mean SFRs of high-luminosity AGNs inside DSFGs, and determine if x-ray luminosities are independent of average SFRs for our sample in the Boötes field.

Clustering, cosmology and a new era of black hole demographics- II. The conditional luminosity functions of Type 2 and Type 1 active galactic nuclei

NASA Astrophysics Data System (ADS)

Ballantyne, D. R.

2017-01-01

The orientation-based unification model of active galactic nuclei (AGNs) posits that the principle difference between obscured (Type 2) and unobscured (Type 1) AGNs is the line of sight into the central engine. If this model is correct then there should be no difference in many of the properties of AGN host galaxies (e.g. the mass of the surrounding dark matter haloes). However, recent clustering analyses of Type 1 and Type 2 AGNs have provided some evidence for a difference in the halo mass, in conflict with the orientation-based unified model. In this work, a method to compute the conditional luminosity function (CLF) of Type 2 and Type 1 AGNs is presented. The CLF allows many fundamental halo properties to be computed as a function of AGN luminosity, which we apply to the question of the host halo masses of Type 1 and 2 AGNs. By making use of the total AGN CLF, the Type 1 X-ray luminosity function, and the luminosity-dependent Type 2 AGN fraction, the CLFs of Type 1 and 2 AGNs are calculated at z ≈ 0 and 0.9. At both z, there is no statistically significant difference in the mean halo mass of Type 2 and 1 AGNs at any luminosity. There is marginal evidence that Type 1 AGNs may have larger halo masses than Type 2s, which would be consistent with an evolutionary picture where quasars are initially obscured and then subsequently reveal themselves as Type 1s. As the Type 1 lifetime is longer, the host halo will increase somewhat in mass during the Type 1 phase. The CLF technique will be a powerful way to study the properties of many AGNs subsets (e.g. radio-loud, Compton-thick) as future wide-area X-ray and optical surveys substantially increase our ability to place AGNs in their cosmological context.

The X-ray view of radio-loud active galactic nuclei: The central engine and its environment

NASA Astrophysics Data System (ADS)

Donato, Davide

The non-thermal emission from many Active Galactic Nuclei (AGN) is obscured by optically thick circumnuclear matter, particularly at optical and ultraviolet wavelengths. In radio-loud (RL) sources, the AGN activity is coupled with the presence of a bipolar jet that emit radio through g-ray light which is relativistically beamed along the jet axes. The combination of absorption and beaming produces highly anisotropic radiation. The understanding of the origin and magnitude of this radiation allows astronomers to unify different classes of AGN; that is, to identify each single, underlying AGN type that gives rise to different classes through different orientations with respect to the jet axis. This is the fundamental notion behind what are called "unification models" of AGN. Although this general idea is well accepted, many aspects remain matter of debate. In fact, the explanation of the wide and complex variety of AGN phenomena must be searched in a combination of apparent differences (like orientation) and real differences in a number of physical parameters (like gas/dust content and distribution, luminosity, etc.). The goal of this thesis is to address some of the RL unification open questions using X-ray data. The improved sensitivity and angular resolution of a new generation of satellites, combined with the fact that X-rays provide useful information on a variety of AGN phenomena, will allow me to: (1) Study the broadband X-ray continua of BL Lacertae objects (BL Lacs) and Flat Spectrum Radio Quasars (FSRQs); (2) Probe the emission from the very inner region of an AGN; (3) Determine the presence and characteristic of extended X-ray emission from the AGN environment. The results obtained from theses studies will provide me insights into (1) the X-ray average spectral properties of BL Lacs and FSRQs and the physical processes responsible of the emission; (2) the presence of the obscuring torus and the amount of absorption, (3) the nature of X-ray emission, and (4

Do some AGN lack X-ray emission?

NASA Astrophysics Data System (ADS)

Simmonds, C.; Bauer, F. E.; Thuan, T. X.; Izotov, Y. I.; Stern, D.; Harrison, F. A.

2016-12-01

Context. Intermediate-mass black holes (IMBHs) are thought to be the seeds of early supermassive black holes (SMBHs). While ≳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 luminosity relations and well-characterized IMBH/SMBH samples. Results: Despite having clear broad optical emission lines that are long-lived (≳10-13 yr), these candidate AGN appear to lack associated strong X-ray and hard UV emission, lying at least 1-2 dex off the known AGN correlations. If they are IMBHs/SMBHs, our constraints imply that they either are not actively accreting, their accretion disks are fully obscured along our line-of-sight, or their accretion disks are not producing characteristic high energy emission. Alternatively, if they are not AGN, then their luminous broad emission lines imply production by extreme stellar processes. The latter would have profound implications on the applicability of broad lines for mass estimates of massive black holes. The reduced spectra (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/596/A64

Physical Conditions in Ultra-fast Outflows in AGN

NASA Astrophysics Data System (ADS)

Kraemer, S. B.; Tombesi, F.; Bottorff, M. C.

2018-01-01

XMM-Newton and Suzaku spectra of Active Galactic Nuclei (AGN) have revealed highly ionized gas, in the form of absorption lines from H-like and He-like Fe. Some of these absorbers, ultra-fast outflows (UFOs), have radial velocities of up to 0.25c. We have undertaken a detailed photoionization study of high-ionization Fe absorbers, both UFOs and non-UFOs, in a sample of AGN observed by XMM-Newton. We find that the heating and cooling processes in UFOs are Compton-dominated, unlike the non-UFOs. Both types are characterized by force multipliers on the order of unity, which suggest that they cannot be radiatively accelerated in sub-Eddington AGN, unless they were much less ionized at their point of origin. However, such highly ionized gas can be accelerated via a magneto-hydrodynamic (MHD) wind. We explore this possibility by applying a cold MHD flow model to the UFO in the well-studied Seyfert galaxy, NGC 4151. We find that the UFO can be accelerated along magnetic streamlines anchored in the accretion disk. In the process, we have been able to constrain the magnetic field strength and the magnetic pressure in the UFO and have determined that the system is not in magnetic/gravitational equipartition. Open questions include the variability of the UFOs and the apparent lack of non-UFOs in UFO sources.

X-ray and Ultraviolet Properties of AGNs in Nearby Dwarf Galaxies

NASA Astrophysics Data System (ADS)

Baldassare, Vivienne F.; Reines, Amy E.; Gallo, Elena; Greene, Jenny E.

2017-02-01

We present new Chandra X-ray Observatory and Hubble Space Telescope observations of eight optically selected broad-line active galactic nucleus (AGN) candidates in nearby dwarf galaxies (z < 0.055). Including archival Chandra observations of three additional sources, our sample contains all 10 galaxies from Reines et al. (2013) with both broad Hα emission and narrow-line AGN ratios (six AGNs, four composites), as well as one low-metallicity dwarf galaxy with broad Hα and narrow-line ratios characteristic of star formation. All 11 galaxies are detected in X-rays. Nuclear X-ray luminosities range from L 0.5-7keV ≈ 5 × 1039 to 1 × 1042 ergs-1. In all cases except for the star-forming galaxy, the nuclear X-ray luminosities are significantly higher than would be expected from X-ray binaries, providing strong confirmation that AGNs and composite dwarf galaxies do indeed host actively accreting black holes (BHs). Using our estimated BH masses (which range from ˜7 × 104 to 1 × 106 M ⊙), we find inferred Eddington fractions ranging from ˜0.1% to 50%, I.e., comparable to massive broad-line quasars at higher redshift. We use the HST imaging to determine the ratio of UV to X-ray emission for these AGNs, finding that they appear to be less X-ray luminous with respect to their UV emission than more massive quasars (I.e., α OX values an average of 0.36 lower than expected based on the relation between α OX and 2500 Å luminosity). Finally, we discuss our results in the context of different accretion models onto nuclear BHs.

Can Radio Emission From Luminous Obscured AGN Blow Kpc-scale Ionized Outflows?

NASA Astrophysics Data System (ADS)

Goulding, Andy

2017-09-01

We propose joint VLA radio and Chandra X-ray to observe 4 AGN selected from the SDSS-BOSS and the Hyper Suprime-Cam surveys that present spectacular extended outflowing [O III] regions, reaching up to 50kpc in diameter. Our proposed observations allow us to study the mechanical and kinematical output of the AGN through radio and X-ray observations, measure the fraction of the AGN bolometric luminosity that is transferred to the outflow, and to determine the morphology and spectral index (by producing high-res continuum maps) of the radio emission that may be co-spatial with the extended ionized AGN outflow. In turn, our study will determine what role the AGN plays in producing extended outflows, and hence, provide an in-depth understanding of the physical drivers of AGN feedback.

AGN feedback and the origin of the α enhancement in early-type galaxies - insights from the GAEA model

NASA Astrophysics Data System (ADS)

De Lucia, Gabriella; Fontanot, Fabio; Hirschmann, Michaela

2017-03-01

We take advantage of our recently published model for GAlaxy Evolution and Assembly (GAEA) to study the origin of the observed correlation between [α/Fe] and galaxy stellar mass. In particular, we analyse the role of radio-mode active galactic nuclei (AGN) feedback, which recent work has identified as a crucial ingredient to reproduce observations. In GAEA, this process introduces the observed trend of star formation histories extending over shorter time-scales for more massive galaxies, but does not provide a sufficient condition to reproduce the observed α enhancements of massive galaxies. In the framework of our model, this is possible only by assuming that any residual star formation is truncated for galaxies more massive than 1010.5 M⊙. This results, however, in even shorter star formation time-scales for the most massive galaxies, which translate in total stellar metallicities significantly lower than observed. Our results demonstrate that (I) trends of [α/Fe] ratios cannot be simply converted into relative time-scale indicators; and (II) AGN feedback cannot explain alone the positive correlation between [α/Fe] and galaxy mass/velocity dispersion. Reproducing simultaneously the mass-metallicity relation and the α enhancements observed pose a challenge for hierarchical models, unless more exotic solutions are adopted such as metal-rich winds or a variable initial mass function.

Evidence for Ultra-Fast Outflows in Radio-Quiet AGNs. 2; Detailed Photoionization Modeling of Fe K-Shell Absorption Lines

NASA Technical Reports Server (NTRS)

Tombesi, Francesco; Clapp, M.; Reeves, J. N.; Palumbo, G. G. C.; Braito, V.; Dadina, M.

2011-01-01

X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet AGNs. In the previous paper of this series we defined UFOs as those absorbers with an outflow velocity higher than 10,000km/s and assessed the statistical significance of the associated blue shifted FeK absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. In the present paper we report a detailed curve of growth analysis and directly model the FeK absorbers with the Xstar photo-ionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35%. The outflow velocity distribution spans from \\sim10,000km/s (\\sim0.03c) up to \\siml00,000kmis (\\sim0.3c), with a peak and mean value of\\sim42,000km/s (\\sim0.14c). The ionization parameter is very high and in the range log\\xi 3-6 erg s/cm, with a mean value of log\\xi 4.2 erg s/cm. The associated column densities are also large, in the range N_H\\siml0(exp 22)-10(exp 24)/sq cm, with a mean value of N_H\\siml0(exp23)/sq cm. We discuss and estimate how selection effects, such as those related to the limited instrumental sensitivity at energies above 7keV, may hamper the detection of even higher velocities and higher ionization absorbers. We argue that, overall, these results point to the presence of extremely ionized and possibly almost Compton thick outflowing material in the innermost regions of AGNs. This also suggests that UFOs may potentially play a significant role in the expected cosmological feedback from AGNs and their study can provide important clues on the connection between accretion disks, winds and jets.

Mid-infrared Flux Variability in an Awakening AGN

NASA Astrophysics Data System (ADS)

Yeh, Sherry

We propose FORCAST spectroscopic observations between 8 um to 40 um near the nucleus of NGC 660. NGC 660 underwent an AGN outburst 6 years ago, which is an ideal case for studying AGN astrophysics in a rather quiecent system. However, this rare event has not yet been monitored. Our immidiate goal is to verify the MIR spectroscipic variabilitiy in NGC 660, and to study the AGN effects on dust destruction and ISM. We will compare the FORCAST spectra with the Spitzer IRS spectra (taken before the AGN outburst), including dust continuum, PAH emission, and high- and low-ionization emission lines. FORCAST's slit width is a close match to the IRS slit width, allowing a direct comparison of the spectra between FORCAST and IRS. Our single-slit Subaru COMICS spectrum taken after the outburst shows significantly weakened PAH emission and dust continuum, suggesting dust destruction. However, it is difficult to draw robust intepretations due to systematic uncertainties in the Subaru data. If dust destruction is confirmed in the post-outburst FORCAST observaitons, we will evaluate the energy budget using the MIR line ratio diagnostics, with archival X-ray and radio data. We will then propose cadence observations of MGC 660's nucleus to monitor the MIR flux variability, and employ the reverberation mapping technique to study NGC 660's AGN.

Uncovering extreme AGN variability in serendipitous X-ray source surveys

NASA Astrophysics Data System (ADS)

Moran, Edward C.; Garcia Soto, Aylin; LaMassa, Stephanie; Urry, Meg

2018-01-01

Constraints on the duty cycle and duration of accretion episodes in active galactic nuclei (AGNs) are vital for establishing how most AGNs are fueled, which is essential for a complete picture of black hole/galaxy co-evolution. Perhaps the best handle we have on these activity parameters is provided by AGNs that have displayed dramatic changes in their bolometric luminosities and, in some cases, spectroscopic classifications. Given that X-ray emission is directly linked to black-hole accretion, X-ray surveys should provide a straightforward means of identifying AGNs that have undergone dramatic changes in their accretion states. However, it appears that such events are very rare, so wide-area surveys separated in time by many years are needed to maximize discovery rates. We have cross-correlated the Einstein IPC Two-Sigma Catalog with the ROSAT All-Sky Survey Faint Source Catalog to identify a sample of soft X-ray sources that varied by factors ranging from 7 to more than 100 over a ten year timescale. When possible, we have constructed long-term X-ray light curves for the sources by combining the Einstein and RASS fluxes with those obtained from serendipitous pointed observations by ROSAT, Chandra,XMM, and Swift. Optical follow-up observations indicate that many of the extremely variable sources in our sample are indeed radio-quiet AGNs. Interestingly, the majority of objects that dimmed between ~1980 and ~1990 are still (or are again) broad-line AGNs rather than“changing-look” candidates that have more subtle AGN signatures in their spectra — despite the fact that none of the sources examined thus far has returned to its highest observed luminosity. Future X-ray observations will provide the opportunity to characterize the X-ray behavior of these anonymous, extreme AGNs over a four decade span.

Host Galaxy Properties Of The Swift Bat Hard X-ray Survey Of Agn

NASA Astrophysics Data System (ADS)

Koss, Michael; Mushotzky, R.; Veilleux, S.; Winter, L.

2010-03-01

Surveys of AGN taken in the optical, UV, and soft X-rays miss an important population of obscured AGN only visible in the hard X-rays and mid-IR wavelengths. The SWIFT BAT survey in the hard X-ray range (14-195 keV) has provided a uniquely unbiased sample of AGN unaffected by galactic or circumnuclear absorption. Optical imaging of this unbiased sample provides a new opportunity to understand how the environments of the host galaxies are linked to AGN. In 2008, we observed 90 of these targets at Kitt Peak with the 2.1m in the SDSS ugriz bands over 17 nights. Using these observations and SDSS data we review the relationships between color, morphology, merger activity, stellar mass, star formation, and AGN luminosity for a sample of 145 AGN Hard X-ray Selected AGN.

Active Galaxy Unification in the Era of X-Ray Polarimetry

NASA Technical Reports Server (NTRS)

Dorodnitsyn, A.; Kallman, T.

2010-01-01

Active galactic nuclei (AGNs), Seyfert galaxies, and quasars are powered by luminous accretion and often accompanied by winds that are powerful enough to affect the AGN mass budget, and whose observational appearance bears an imprint of processes that are happening within the central parsec around the black hole (BH). One example of such a wind is the partially ionized gas responsible for X-ray and UV absorption (warm absorbers). Here, we show that such gas will have a distinct signature when viewed in polarized X-rays. Observations of such polarization can test models for the geometry of the flow and the gas responsible for launching and collimating it. We present calculations that show that the polarization depends on the hydrodynamics of the flow, the quantum mechanics of resonance-line scattering, and the transfer of polarized X-ray light in the highly ionized moving gas. The results emphasize the three-dimensional nature of the wind for modeling spectra. We show that the polarization in the 0.1-10 keV energy range is dominated by the effects of resonance lines. We predict a 5%-25% X-ray polarization signature of type-2 objects in this energy range. These results are generalized to flows that originate from a cold torus-like structure, located approximately 1 pc from the BH, which wraps the BH and is ultimately responsible for the apparent dichotomy between type 1 and type 2 AGNs. Such signals will be detectable by future dedicated X-ray polarimetry space missions, such as the NASA Gravity and Extreme Magnetism Small Explorer SMEX, "GEMS" Swank et al. (2008).

Unveiling the AGN activity in multiple SMBH systems observed with XMM-Newton

NASA Astrophysics Data System (ADS)

De Rosa, A.

2017-10-01

In this talk we will present results from the MAGNA (Multiple AGN Activity) project focused on the detection and study of multiple supermassive black hole systems. We investigate the physical properties (accretion rate and local environment) of multiple AGN candidates in interacting systems with respect to isolated sources with the goal to understand the mechanisms that trigger AGN activity in different stages of galaxy mergers. We present the study performed with SDSS and XMM data sets of 4 AGN pairs at separations of 20-70 kpc. XMM data allowed us to detect and characterize the AGN in all systems, by measuring the accretion and absorption properties of the sources. In each system at least one object is highly obscured, possibly Compton-thick, in agreement with the hypothesis that galaxy encounters are effective in driving gas inflow. One system however manifests the opposite behaviour showing a pair composed from an unobscured type 1 AGN and a Compton Thick AGN. The talk will reflect on broader implications of these findings.

On the Star Formation-AGN Connection at zeta (is) approximately greater than 0.3

NASA Technical Reports Server (NTRS)

LaMassa, Stephanie M.; Heckman, T. M.; Ptak, Andrew; Urry, C. Megan

2013-01-01

Using the spectra of a sample of approximately 28,000 nearby obscured active galaxies from Data Release 7 of the Sloan Digital Sky Survey (SDSS), we probe the connection between active galactic nucleus (AGN) activity and star formation over a range of radial scales in the host galaxy. We use the extinction-corrected luminosity of the [O iii] 5007A line as a proxy of intrinsic AGN power and supermassive black hole (SMBH) accretion rate. The star formation rates (SFRs) are taken from the MPA-JHU value-added catalog and are measured through the 3 inch SDSS aperture. We construct matched samples of galaxies covering a range in redshifts. With increasing redshift, the projected aperture size encompasses increasing amounts of the host galaxy. This allows us to trace the radial distribution of star formation as a function of AGN luminosity. We find that the star formation becomes more centrally concentrated with increasing AGN luminosity and Eddington ratio. This implies that such circumnuclear star formation is associated with AGN activity, and that it increasingly dominates over omnipresent disk star formation at higher AGN luminosities, placing critical constraints on theoretical models that link host galaxy star formation and SMBH fueling. We parameterize this relationship and find that the star formation on radial scales (is) less than 1.7 kpc, when including a constant disk component, has a sub-linear dependence on SMBH accretion rate: SFR in proportion to solar mass(sup 0.36), suggesting that angular momentum transfer through the disk limits accretion efficiency rather than the supply from stellar mass loss.

Unification of the family of Garrison-Wright's phases.

PubMed

Cui, Xiao-Dong; Zheng, Yujun

2014-07-24

Inspired by Garrison and Wight's seminal work on complex-valued geometric phases, we generalize the concept of Pancharatnam's "in-phase" in interferometry and further develop a theoretical framework for unification of the abelian geometric phases for a biorthogonal quantum system modeled by a parameterized or time-dependent nonhermitian hamiltonian with a finite and nondegenerate instantaneous spectrum, that is, the family of Garrison-Wright's phases, which will no longer be confined in the adiabatic and nonadiabatic cyclic cases. Besides, we employ a typical example, Bethe-Lamb model, to illustrate how to apply our theory to obtain an explicit result for the Garrison-Wright's noncyclic geometric phase, and also to present its potential applications in quantum computation and information.

Compton thick AGN in the NuSTAR era

NASA Astrophysics Data System (ADS)

Marchesi, Stefano; Ajello, Marco; Marcotulli, Lea; Comastri, Andrea

2017-08-01

The recent launch of the Nuclear Spectroscopic Telescope Array (NuSTAR), the first telescope with focusing optics at >10 keV, represented a major breakthrough in the study of obscured active galactic nuclei (AGN). In this talk, I present the results of the 0.3-100 keV spectral analysis of the 30 Compton thick (CT-; i.e., those sources having column density NH>1E24 cm-2) AGN detected within z~0.1 in the BAT 100-month survey with available NuSTAR data. Particularly, I will focus on how adding NuSTAR data to the 0.3-10 keV information helps to characterize the CT-AGN population, significantly improving the measurements of important X-ray spectral parameters such as the photon index, the intrinsic absorption, the intensity of the Iron K alpha line at 6.4 keV and the obscuring torus opening angle. Finally, I will discuss the role of these objects in the context of obscured AGN accretion physics, and their contribution to the cosmic X-ray background.

Imprints of the large-scale structure on AGN formation and evolution

NASA Astrophysics Data System (ADS)

Porqueres, Natàlia; Jasche, Jens; Enßlin, Torsten A.; Lavaux, Guilhem

2018-04-01

Black hole masses are found to correlate with several global properties of their host galaxies, suggesting that black holes and galaxies have an intertwined evolution and that active galactic nuclei (AGN) have a significant impact on galaxy evolution. Since the large-scale environment can also affect AGN, this work studies how their formation and properties depend on the environment. We have used a reconstructed three-dimensional high-resolution density field obtained from a Bayesian large-scale structure reconstruction method applied to the 2M++ galaxy sample. A web-type classification relying on the shear tensor is used to identify different structures on the cosmic web, defining voids, sheets, filaments, and clusters. We confirm that the environmental density affects the AGN formation and their properties. We found that the AGN abundance is equivalent to the galaxy abundance, indicating that active and inactive galaxies reside in similar dark matter halos. However, occurrence rates are different for each spectral type and accretion rate. These differences are consistent with the AGN evolutionary sequence suggested by previous authors, Seyferts and Transition objects transforming into low-ionization nuclear emission line regions (LINERs), the weaker counterpart of Seyferts. We conclude that AGN properties depend on the environmental density more than on the web-type. More powerful starbursts and younger stellar populations are found in high densities, where interactions and mergers are more likely. AGN hosts show smaller masses in clusters for Seyferts and Transition objects, which might be due to gas stripping. In voids, the AGN population is dominated by the most massive galaxy hosts.

A total and polarized infrared flux view of the AGN clumpy torus

NASA Astrophysics Data System (ADS)

Lopez Rodriguez, Enrique

2013-12-01

Magnetohydrodynamical theories consider the torus of Active Galactic Nuclei (AGN) to be part of an outflow wind moving away from the central engine. In this framework, the torus is a particular region of the wind, where dusty and optically thick clouds are formed. The outflows are strongly related to the accretion rate and magnetic field strength, which play an important role in the creation, morphology and evolution of the torus. Through infrared (IR) imaging and polarimetry observations, this dissertation (1) searches for signatures of dusty tori in low-luminosity AGN (LLAGN); (2) explores the role and strength of magnetic field in the torus; and (3) investigates the nucleus of radio-loud AGN. Recent theoretical models predicted that LLAGN do not host a Seyfert-like torus, since low-luminosities (<1042 erg s-1 ) cannot sustain the required outflow rate. High-spatial resolution mid-IR (MIR) imaging and nuclear spectral energy distribution of 22 LLAGN reveals different IR characteristics by dividing the sample in terms of the Eddington ratio. These galaxies show a diversity of nuclear morphologies and have a high MIR/X-ray luminosity ratio compared to higher-luminosity AGN. Star formation, jets and/or truncated accretion disk can explain the MIR excess. Although several models have been made to account for the outflowing dusty winds from the central engine, the magnetic field strength at the position of the torus remains poorly characterized. Through a novel study using near-IR polarimetry, the magnetic field strength in the clumpy torus was estimated. Specifically, if paramagnetic alignment is assumed in the dusty clouds of the torus, the magnetic field strength of the torus of IC5063 is estimated to be in the range of 12--128 mG. Alternatively, Chandrasekhar-Fermi method suggests a lower-limit magnetic field strength of 13 mG. For the archetypical radio-loud AGN, Cygnus A, MIR polarimetry using CanariCam on the 10.4-m Gran Telescopio de Canarias revealed a high

Confinement and diffusion time-scales of CR hadrons in AGN-inflated bubbles

NASA Astrophysics Data System (ADS)

Prokhorov, D. A.; Churazov, E. M.

2017-09-01

While rich clusters are powerful sources of X-rays, γ-ray emission from these large cosmic structures has not been detected yet. X-ray radiative energy losses in the central regions of relaxed galaxy clusters are so strong that one needs to consider special sources of energy, likely active galactic nucleus (AGN) feedback, to suppress catastrophic cooling of the gas. We consider a model of AGN feedback that postulates that the AGN supplies the energy to the gas by inflating bubbles of relativistic plasma, whose energy content is dominated by cosmic-ray (CR) hadrons. If most of these hadrons can quickly escape the bubbles, then collisions of CRs with thermal protons in the intracluster medium (ICM) should lead to strong γ-ray emission, unless fast diffusion of CRs removes them from the cluster. Therefore, the lack of detections with modern γ-ray telescopes sets limits on the confinement time of CR hadrons in bubbles and CR diffusive propagation in the ICM.

Using WISE to Find Obscured AGN Activity in SDSS Mergers and Interactions

NASA Astrophysics Data System (ADS)

Weston, Madalyn; McIntosh, Daniel H.; Her, Xiachang; Rigby, Jane R.

2015-01-01

In simulations, major encounters between gas-rich galaxies are predicted to drive gas to the centers of interacting and merging systems triggering new star formation (SF) and fueling an active galactic nucleus (AGN). Depending on the rate of SF, large amounts of obscuring dust can make detection of merger-induced activity difficult and may be at the heart of the ongoing merger-AGN connection debate. To provide better constraints on the importance of obscured AGNs, we use data from the Wide-field Infrared Survey Explorer (WISE) for a comprehensive sample of over 1000 major galaxy interactions and ongoing mergers visually selected from the SDSS with Mstar>1e10 Msun and 0.01 < z < 0.08. We examine the [3.4]-[4.6] versus [4.6]-[12] micron color-color plane and find that most interactions and mergers have the same colors as normal (non-interacting and non-merging) galaxies, which define a narrow [3.4]-[4.6] micron locus and span a wide range in [4.6]-[12] micron colors from spectroscopically quiescent (blue, no dust) to galaxies with SF emission (dust-reddened). We find that 2-6% of mergers (and 2-3% of interactions) have unusually red [3.4]-[4.6] micron colors, which are associated with dust-obscured (Type-2) AGNs. We note that mergers (interactions) are 4-15 (3-8) times more likely to host a buried AGN than normal galaxies. We also find that optical emission-line AGNs (Seyferts) identified as mergers are 3-7 times more likely to be obscured than non-merging Seyferts. We investigate whether the obscured AGN subset of our sample have unique properties and find that their stellar masses, mass ratios, pair separations, and environments are not statistically different from those of the bulk of mergers and interactions with normal WISE colors. We note that among mergers and interactions with an AGN, the WISE-selected AGN favor higher [OIII] luminosities associated with higher AGN power than their unobscured counterparts. Our findings support an AGN-merger connection.

Morphologies of mid-IR variability-selected AGN host galaxies

NASA Astrophysics Data System (ADS)

Polimera, Mugdha; Sarajedini, Vicki; Ashby, Matthew L. N.; Willner, S. P.; Fazio, Giovanni G.

2018-05-01

We use multi-epoch 3.6 and 4.5 μm data from the Spitzer Extended Deep Survey (SEDS) to probe the AGN population among galaxies to redshifts ˜3 via their mid-IR variability. About 1 per cent of all galaxies in our survey contain varying nuclei, 80 per cent of which are likely to be AGN. Twenty-three per cent of mid-IR variables are also X-ray sources. The mid-IR variables have a slightly greater fraction of weakly disturbed morphologies compared to a control sample of normal galaxies. The increased fraction of weakly distorted hosts becomes more significant when we remove the X-ray emitting AGN, while the frequency of strongly disturbed hosts remains similar to the control galaxy sample. These results suggest that mid-IR variability identifies a unique population of obscured, Compton-thick AGN revealing elevated levels of weak distortion among their host galaxies.

2MASS J00423991+3017515: An AGN On The Run?

NASA Astrophysics Data System (ADS)

Hogg, James

2016-09-01

We have discovered a peculiar AGN, 2MASS J00423991+3017515, in a local (z=0.14), disturbed galaxy whose optical spectrum has multiple broad lines that are consistently offset from the narrow line emission and host galaxy absorption by 1530 km/s. The morphology of the host galaxy and spectral properties thus suggest this AGN may be a recoiling supermassive black hole (SMBH). We propose high-resolution X-ray imaging and spectral follow-ups with the ACIS camera on Chandra to determine if the source of the kinematically-offset broad line emission is also spatially offset from the nucleus of the host galaxy. If a single, spatially offset AGN is detected, this source will be strongest candidate for a recoiling AGN candidate discovered to date.

X-Ray and Ultraviolet Properties of AGNs in Nearby Dwarf Galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baldassare, Vivienne F.; Gallo, Elena; Reines, Amy E.

2017-02-10

We present new Chandra X-ray Observatory and Hubble Space Telescope observations of eight optically selected broad-line active galactic nucleus (AGN) candidates in nearby dwarf galaxies ( z < 0.055). Including archival Chandra observations of three additional sources, our sample contains all 10 galaxies from Reines et al. (2013) with both broad H α emission and narrow-line AGN ratios (six AGNs, four composites), as well as one low-metallicity dwarf galaxy with broad H α and narrow-line ratios characteristic of star formation. All 11 galaxies are detected in X-rays. Nuclear X-ray luminosities range from L {sub 0.5–7keV} ≈ 5 × 10{sup 39}more » to 1 × 10{sup 42} ergs{sup −1}. In all cases except for the star-forming galaxy, the nuclear X-ray luminosities are significantly higher than would be expected from X-ray binaries, providing strong confirmation that AGNs and composite dwarf galaxies do indeed host actively accreting black holes (BHs). Using our estimated BH masses (which range from ∼7 × 10{sup 4} to 1 × 10{sup 6} M {sub ⊙}), we find inferred Eddington fractions ranging from ∼0.1% to 50%, i.e., comparable to massive broad-line quasars at higher redshift. We use the HST imaging to determine the ratio of UV to X-ray emission for these AGNs, finding that they appear to be less X-ray luminous with respect to their UV emission than more massive quasars (i.e., α {sub OX} values an average of 0.36 lower than expected based on the relation between α {sub OX} and 2500 Å luminosity). Finally, we discuss our results in the context of different accretion models onto nuclear BHs.« less

Korean Unification: The Way Forward

DTIC Science & Technology

2009-03-01

THE WAY FORWARD by Brian A. Forster March 2009 Thesis Advisor: Robert Weiner Second Reader: Christopher P .Twomey THIS PAGE ...INTENTIONALLY LEFT BLANK i REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 Public reporting burden for this collection of information is...possibility of a unified Korean nation. 15. NUMBER OF PAGES 109 14. SUBJECT TERMS Korean Unification, The Republic of Korea, The Democratic People’s

Disentangling Dominance: Obscured AGN Activity versus Star Formation in BPT-Composites

NASA Astrophysics Data System (ADS)

Trouille, Laura

2011-11-01

Approximately 20% of SDSS emission-line galaxies (ELG) lie in the BPT-comp regime, between the Kauffmann et al. (2003) empirically determined SF-dominated regime and the Kewley et al. (2001) theoretically predicted AGN-dominated regime. BPT-AGN, on the other hand, make up only 11% of the ELG population. Whether to include the significant number of BPT-comp in samples of AGN or samples of star-forming galaxies is an open question and has important implications for galaxy evolution studies, metallicity studies, etc. Using a large pectroscopic sample of GOODS-N and LH galaxies with deep Chandra imaging, we perform an X-ray stacking analysis of BPT-comp. We find the stacked signal to be X-ray hard. This X-ray hardness can be indicative of obscured AGN activity or the presence of HMXBs associated with ongoing star formation. In order to distinguish between these scenarios, we perform an IR stacking analysis using Spitzer 24 micron data. The stacked BPT-comp lies well above the expected value for L_x/L_IR for pure star-forming galaxies; similarly for the X-ray detected BPT-comp. We also find that the BPT-comp lie in the AGN-dominated regime of our new TBT diagnostic, which uses [NeIII]/[OII] versus rest-frame g-z colour to identify AGN and star forming galaxies out to z=1.4. [NeIII], which has a higher ionisation potential than other commonly used forbidden emission lines, appears to foster a more reliable selection of AGN-dominated galaxies. These findings suggest that both the X-ray and optical signal in BPT-comp are dominated by obscured or low accretion rate AGN activity rather than star formation. This is in contrast to claims by previous optical emission-line studies that the signal in BPT-comp is dominated by star-formation activity. Therefore, we recommend that groups carefully consider the impact of excluding or including BPT-comp on the interpretation of their results. For example, for studies involving determining the bolometric contribution from AGN activity

The study of AGN variability using extended emission line regions

NASA Astrophysics Data System (ADS)

Sartori, Lia

2018-01-01

The study of AGN variability on different timescales can provide important information about black hole accretion physics, as well as the black hole – host galaxy interaction and coevolution. The discovery of an extended AGN photoionised cloud associated with the nearby galaxy IC 2497, the so-called “Hanny’s Voorwerp” (HV), provided us with a laboratory to study AGN variability over 100 kyr timescales. HV was illuminated by a strong quasar, but the quasar in IC 2497 dropped in luminosity in the last 200 kyrs. Because of its recent change we can now explore the host galaxy unimpeded by the presence of a quasar dominating the observations. On the other hand, the photoionised cloud preserves the echoes of its past activity. Citizen scientists taking part in the Galaxy Zoo project assembled a sample of low-redshift galaxies showing AGN photoionised clouds similar to HV. I will show how these objects can help us understand what happens when a quasar changes in luminosity and accretion state, and ultimately what is the physics driving AGN variability.

Uncovering Heavily Obscured AGN with WISE and NuSTAR

NASA Astrophysics Data System (ADS)

Hickox, Ryan C.; Carroll, Christopher M.; Yan, Wei; DiPompeo, Michael A.; Hainline, Kevin N.; NuSTAR Obscured AGN Team

2018-01-01

Supermassive black holes gain their mass through accretion as active galactic nuclei (AGN), but it is now clear that a large fraction of this growth is "hidden" behind large columns of gas and dust. Of particular interest are Compton-thick (CT) AGN, with columns NH > 1024 cm-2, that have been difficult to identify using optical or soft X-ray surveys. We will present two studies of heavily obscured AGN that aim to uncover more of the full population of "hidden" growing black holes: (1) Analysis of the spectral energy distributions of millions of galaxies with photometry from WISE (mid-IR), UKIDSS (near-IR), and SDSS (optical), that uncovers large populations of weak or heavily buried AGN, and (2) NuSTAR observations of a sample of candidate highly obscured AGN, selected from WISE and SDSS photometry,and confirmed using SALT and Keck spectroscopy. The NuSTAR data reveal the existence of powerful CT quasars with extremely large columns NH > 1025 cm-2, which may represent a significant fraction of previously hidden black hole growth. This work is supported by NASA grant numbers NNX16AN48G and NNX15AP24G, and the NSF through grant numbers 1515364 and 1554584.

The clustering amplitude of X-ray-selected AGN at z ˜ 0.8: evidence for a negative dependence on accretion luminosity

NASA Astrophysics Data System (ADS)

Mountrichas, G.; Georgakakis, A.; Menzel, M.-L.; Fanidakis, N.; Merloni, A.; Liu, Z.; Salvato, M.; Nandra, K.

2016-04-01

The northern tile of the wide-area and shallow XMM-XXL X-ray survey field is used to estimate the average dark matter halo mass of relatively luminous X-ray-selected active galactic nucleus (AGN) [log {L}_X (2-10 keV)= 43.6^{+0.4}_{-0.4} erg s^{-1}] in the redshift interval z = 0.5-1.2. Spectroscopic follow-up observations of X-ray sources in the XMM-XXL field by the Sloan telescope are combined with the VIMOS Public Extragalactic Redshift Survey spectroscopic galaxy survey to determine the cross-correlation signal between X-ray-selected AGN (total of 318) and galaxies (about 20 000). We model the large scales (2-25 Mpc) of the correlation function to infer a mean dark matter halo mass of log M / (M_{{⊙}} h^{-1}) = 12.50 ^{+0.22} _{-0.30} for the X-ray-selected AGN sample. This measurement is about 0.5 dex lower compared to estimates in the literature of the mean dark matter halo masses of moderate-luminosity X-ray AGN [LX(2-10 keV) ≈ 1042-1043 erg s- 1] at similar redshifts. Our analysis also links the mean clustering properties of moderate-luminosity AGN with those of powerful ultraviolet/optically selected QSOs, which are typically found in haloes with masses few times 1012 M⊙. There is therefore evidence for a negative luminosity dependence of the AGN clustering. This is consistent with suggestions that AGN have a broad dark matter halo mass distribution with a high mass tail that becomes subdominant at high accretion luminosities. We further show that our results are in qualitative agreement with semi-analytic models of galaxy and AGN evolution, which attribute the wide range of dark matter halo masses among the AGN population to different triggering mechanisms and/or black hole fuelling modes.

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

NASA Astrophysics Data System (ADS)

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

2016-06-01

We present an intrinsic AGN spectral energy distribution (SED) extending from the optical to the submm, derived with a sample of unobscured, optically luminous (νLν,5100 > 1043.5 erg s-1) QSOs at z < 0.18 from the Palomar Green survey. The intrinsic AGN SED was computed by removing the contribution from stars using the 11.3 μm polycyclic aromatic hydrocarbon (PAH) feature in the QSOs' mid-IR spectra; the 1σ uncertainty on the SED ranges between 12 and 45 per cent as a function of wavelength and is a combination of PAH flux measurement errors and the uncertainties related to the conversion between PAH luminosity and star-forming luminosity. Longwards of 20 μm, the shape of the intrinsic AGN SED is independent of the AGN power indicating that our template should be applicable to all systems hosting luminous AGN (νLν, 5100 or L_X(2-10 keV) ≳ 1043.5 erg s-1). 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' broad-band photometric observation (at λ < 1000 μm) 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 AA is at least a factor of 4 smaller than the total infrared luminosity (LIR, 8-1000 μm) of the galaxy. Finally, we examine the implication of our work in statistical studies of star formation in AGN host galaxies.

X-Rays and Infrared Selected AGN

NASA Astrophysics Data System (ADS)

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

Mid-infrared Variability of Changing-look AGNs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheng, Zhenfeng; Wang, Tinggui; Jiang, Ning

2017-09-01

It is known that some active galactic nuclei (AGNs) transit from Type 1 to Type 2 or vice versa. There are two explanations for the so-called changing-look AGNs: one is the dramatic change of the obscuration along the line of sight, and the other is the variation of accretion rate. In this Letter, we report the detection of large amplitude variations in the mid-infrared luminosity during the transitions in 10 changing-look AGNs using the Wide-field Infrared Survey Explorer ( WISE ) and newly released Near-Earth Object WISE Reactivation data. The mid-infrared light curves of 10 objects echo the variability inmore » the optical band with a time lag expected for dust reprocessing. The large variability amplitude is inconsistent with the scenario of varying obscuration, rather it supports the scheme of dramatic change in the accretion rate.« less

A POWERFUL AGN OUTBURST IN RBS 797

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cavagnolo, K. W.; McNamara, B. R.; Wise, M. W.

2011-05-10

Utilizing {approx}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) x 10{sup 60} erg and {approx}(3-6) x 10{supmore » 45} erg s{sup -1}, respectively, depending on the assumed geometrical configuration of the cavities. Thus, RBS 797 is apparently among the most powerful AGN outbursts known in a cluster. The average mass accretion rate needed to power the AGN by accretion alone is {approx}1 M{sub sun} yr{sup -1}. We show that accretion of cold gas onto the AGN at this level is plausible, but that Bondi accretion of the hot atmosphere is probably not. The brightest cluster galaxy (BCG) harbors an unresolved, non-thermal nuclear X-ray source with a bolometric luminosity of {approx}2 x 10{sup 44} erg s{sup -1}. The nuclear emission is probably associated with a rapidly accreting, radiatively inefficient accretion flow. We present tentative evidence that star formation in the BCG is being triggered by the radio jets and suggest that the cavities may be driving weak shocks (M {approx} 1.5) into the ICM, similar to the process in the galaxy cluster MS 0735.6+7421.« less

UNRAVELLING THE COMPLEX STRUCTURE OF AGN-DRIVEN OUTFLOWS. II. PHOTOIONIZATION AND ENERGETICS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karouzos, Marios; Woo, Jong-Hak; Bae, Hyun-Jin, E-mail: woo@astro.snu.ac.kr

2016-12-20

Outflows have been shown to be prevalent in galaxies hosting luminous active galactic nuclei (AGNs); they 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 integral field unit (IFU) data of six 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 connecting the extreme kinematics of the ionized gas to the AGN photoionization.more » 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 30 to 90% of the total mass and kinetic energy of the outflow is contained within the central kpc of the galaxy. The spatially integrated mass and kinetic energy of the gas entrained in the outflow correlate well with the AGN bolometric luminosity and results in energy conversion efficiencies between 0.01% and 1%. Intriguingly, we detect ubiquitous signs of ongoing circumnuclear star formation. Their small size, the centrally contained mass and energy, and the universally detected circumnuclear star formation cast doubts on the potency of these AGN-driven outflows as agents of galaxy-scale negative feedback.« less

Observational Corollaries of Proto-AGN: Understanding Formation of Supermassive Black Hole Seeds

NASA Astrophysics Data System (ADS)

Shlosman, Isaac

2016-10-01

Formation of supermassive black holes (SMBHs) is still an enigma. Recent detections of high-z quasars which harbor massive SMBHs provide a challenge to models of structure buildup in the universe. Main alternatives for the formation of SMBH seeds are (1) remnants of Population III stars, and (2) a direct baryonic collapse within dark matter (DM) halos of 10^8 Mo -- first halos whose virial temperature exceeds 10^4 K, and which can lead to the formation of proto-AGN -- luminous pre-SMBH objects. Potentially, this can involve both high-z objects as well as low-z dwarf galaxies in voids. We focus on the direct collapse in 10^8 Mo halos which circumvents the pitfalls of Pop III remnants. The collapse can proceed via a radiation pressure-supported quasistar -- with a modified blackbody continuum. Such a configuration requires a very efficient angular momentum transfer. Or, it can form a thick, differentially rotating, self-gravitating disk, which is associated with an X-ray-infrared continuum and Seyfert-level luminosity, anisotropic emission, massive bi-conical outflows, and will be a powerful source of the Ly-alpha emission. We propose to perform radiative transfer in the continuum and hydrogen lines (e.g., Lyman and Balmer), using our models of proto-AGN, and do it on-the-fly -- concurrently with the collapse. We shall test the path to quasistellar and disky proto-AGN, produce first synthetic spectra of proto-AGN, and address the issue of feasibility of their detection by the JWST. Finally, we shall develop the strategy of searching for these objects at high- and low-z, based on the specific features in the spectra and associated variability.

The [O III] Profiles of Infrared-selected Active Galactic Nuclei: More Powerful Outflows in the Obscured Population

NASA Astrophysics Data System (ADS)

DiPompeo, M. A.; Hickox, R. C.; Carroll, C. M.; Runnoe, J. C.; Mullaney, J. R.; Fischer, T. C.

2018-03-01

We explore the kinematics of ionized gas via the [O III] λ5007 emission lines in active galactic nuclei (AGNs) selected on the basis of their mid-infrared (IR) emission, and split into obscured and unobscured populations based on their optical‑IR colors. After correcting for differences in redshift distributions, we provide composite spectra of spectroscopically and photometrically defined obscured/Type 2 and unobscured/Type 1 AGNs from 3500 to 7000 Å. The IR-selected obscured sources contain a mixture of narrow-lined Type 2 AGNs and intermediate sources that have broad Hα emission and significantly narrower Hβ. Using both [O III] luminosities and AGN luminosities derived from optical‑IR spectral energy distribution fitting, we find evidence for enhanced large-scale obscuration in the obscured sources. In matched bins of luminosity we find that the obscured population typically has broader, more blueshifted [O III] emission than in the unobscured sample, suggestive of more powerful AGN-driven outflows. This trend is not seen in spectroscopically classified samples, and is unlikely to be entirely explained by orientation effects. In addition, outflow velocities increase from small to moderate AGN E(B ‑ V) values, before flattening out (as traced by FWHM) and even decreasing (as traced by blueshift). While difficult to fully interpret in a single physical model, due to both the averaging over populations and the spatially averaged spectra, these results agree with previous findings that simple geometric unification models are insufficient for the IR-selected AGN population, and may fit into an evolutionary model for obscured and unobscured AGNs.

Obscured AGNs in Bulgeless Hosts discovered by WISE: The Case Study of SDSS J1224+5555

NASA Astrophysics Data System (ADS)

Satyapal, S.; Secrest, N. J.; Rothberg, B.; O'Connor, J. A.; Ellison, S. L.; Hickox, R. C.; Constantin, A.; Gliozzi, M.; Rosenberg, J. L.

2016-08-01

There is mounting evidence that supermassive black holes (SMBHs) form and grow in bulgeless galaxies. However, a robust determination of the fraction of active galactic nuclei (AGNs) in bulgeless galaxies, an important constraint to models of SMBH seed formation and merger-free models of AGN fueling, is unknown, since optical studies have been shown to be incomplete for AGNs in low-mass galaxies. In a recent study using the Wide-field Infrared Survey Explorer, we discovered hundreds of bulgeless galaxies that display mid-infrared signatures of extremely hot dust suggestive of powerful accreting massive black holes, despite having no signatures of black hole activity at optical wavelengths. Here we report X-ray follow-up observations of J122434.66+555522.3, a nearby (z = 0.052) isolated bulgeless galaxy that contains an unresolved X-ray source detected at the 3σ level by XMM-Newton with an observed luminosity uncorrected for intrinsic absorption of {L}2-10{keV}=(1.1+/- 0.4)× {10}40 erg s-1. Ground-based near-infrared spectroscopy with the Large Binocular Telescope and multiwavelength observations from ultraviolet to millimeter wavelengths together suggest that J1224+5555 harbors a highly absorbed AGN with an intrinsic absorption of {N}{{H}}\\gt {10}24 cm-2. The hard X-ray luminosity of the putative AGN corrected for absorption is {L}2-10{keV}˜ 3× {10}42 erg s-1, which, depending on the bolometric correction factor, corresponds to a bolometric luminosity of the AGN of {L}{bol}.˜ 6× {10}43-3 × 1044 {erg} {{{s}}}-1 and a lower mass limit for the black hole of {M}{BH}≃ 2× {10}6 {M}⊙ , based on the Eddington limit. While enhanced X-ray emission and hot dust can be produced by star formation in extremely low metallicity environments typical in dwarf galaxies, J1224+5555 has a stellar mass of ˜ 2.0× {10}10 {M}⊙ and an above solar metallicity (12 + {logO}/{{H}} = 9.11), typical of our WISE-selected bulgeless galaxy sample. While collectively these

Active galactic nuclei: what's in a name?

NASA Astrophysics Data System (ADS)

Padovani, P.; Alexander, D. M.; Assef, R. J.; De Marco, B.; Giommi, P.; Hickox, R. C.; Richards, G. T.; Smolčić, V.; Hatziminaoglou, E.; Mainieri, V.; Salvato, M.

2017-08-01

Active galactic nuclei (AGN) are energetic astrophysical sources powered by accretion onto supermassive black holes in galaxies, and present unique observational signatures that cover the full electromagnetic spectrum over more than twenty orders of magnitude in frequency. The rich phenomenology of AGN has resulted in a large number of different "flavours" in the literature that now comprise a complex and confusing AGN "zoo". It is increasingly clear that these classifications are only partially related to intrinsic differences between AGN and primarily reflect variations in a relatively small number of astrophysical parameters as well the method by which each class of AGN is selected. Taken together, observations in different electromagnetic bands as well as variations over time provide complementary windows on the physics of different sub-structures in the AGN. In this review, we present an overview of AGN multi-wavelength properties with the aim of painting their "big picture" through observations in each electromagnetic band from radio to γ -rays as well as AGN variability. We address what we can learn from each observational method, the impact of selection effects, the physics behind the emission at each wavelength, and the potential for future studies. To conclude, we use these observations to piece together the basic architecture of AGN, discuss our current understanding of unification models, and highlight some open questions that present opportunities for future observational and theoretical progress.

Broad Band Properties of the BAT Selected AGN

NASA Technical Reports Server (NTRS)

Mushotzky, Richard; Winter, Lisa; Tueller, jack

2008-01-01

We will present the x-ray spectral properties of approximately 150 Burst Alert Telescope (BAT) selected active galactic nuclei (AGN) focusing on the issues of spectral complexity, x-ray absorption and its distribution and that contribution of sources to the x-ray background. If time permits we will also present the nature of the host galaxies of the AGN and their relationship to merger candidates.

Long-Term Variability of AGN at Hard X-Rays

NASA Technical Reports Server (NTRS)

Soldi, S.; Beckmann, V.; Baumgartner W. H.; Ponti, G.; Shrader, C. R.; Lubinski, P.; Krimm, H. A.; Mattana, F.; Tueller, J.

2013-01-01

Variability at all observed wavelengths is a distinctive property of active galactic nuclei (AGN). Hard X-rays provide us with a view of the innermost regions of AGN, mostly unbiased by absorption along the line of sight. Characterizing the intrinsic hard X-ray variability of a large AGN sample and comparing it to the results obtained at lower X-ray energies can significantly contribute to our understanding of the mechanisms underlying the high-energy radiation. Methods. Swift/BAT provides us with the unique opportunity to follow, on time scales of days to years and with a regular sampling, the 14-195 keV emission of the largest AGN sample available up to date for this kind of investigation. As a continuation of an early work on the first 9 months of BAT data, we study the amplitude of the variations, and their dependence on sub-class and on energy, for a sample of 110 radio quiet and radio loud AGN selected from the BAT 58-month survey. About 80 of the AGN in the sample are found to exhibit significant variability on months to years time scales, radio loud sources being the most variable. The amplitude of the variations and their energy dependence are incompatible with variability being driven at hard X-rays by changes of the absorption column density. In general, the variations in the 14-24 and 35-100 keV bands are well correlated, suggesting a common origin of the variability across the BAT energy band. However, radio quiet AGN display on average 10 larger variations at 14-24 keV than at 35-100 keV and a softer-when-brighter behavior for most of the Seyfert galaxies with detectable spectral variability on month time scale. In addition, sources with harder spectra are found to be more variable than softer ones. These properties are generally consistent with a variable power law continuum, in flux and shape, pivoting at energies 50 keV, to which a constant reflection component is superposed. When the same time scales are considered, the timing properties of AGN at

Image decomposition of barred galaxies and AGN hosts

NASA Astrophysics Data System (ADS)

Gadotti, Dimitri Alexei

2008-02-01

I present the results of multicomponent decomposition of V and R broad-band images of a sample of 17 nearby galaxies, most of them hosting bars and active galactic nuclei (AGN). I use BUDDA v2.1 to produce the fits, allowing the inclusion of bars and AGN in the models. A comparison with previous results from the literature shows a fairly good agreement. It is found that the axial ratio of bars, as measured from ellipse fits, can be severely underestimated if the galaxy axisymmetric component is relatively luminous. Thus, reliable bar axial ratios can only be determined by taking into account the contributions of bulge and disc to the light distribution in the galaxy image. Through a number of tests, I show that neglecting bars when modelling barred galaxies can result in an overestimation of the bulge-to-total luminosity ratio of a factor of 2. Similar effects result when bright, type 1 AGN are not considered in the models. By artificially redshifting the images, I show that the structural parameters of more distant galaxies can in general be reliably retrieved through image fitting, at least up to the point where the physical spatial resolution is ~1.5kpc. This corresponds, for instance, to images of galaxies at z = 0.05 with a seeing full width at half-maximum (FWHM) of 1.5arcsec, typical of the Sloan Digital Sky Survey (SDSS). In addition, such a resolution is also similar to what can be achieved with the Hubble Space Telescope (HST), and ground-based telescopes with adaptive optics, at z ~ 1-2. Thus, these results also concern deeper studies such as COSMOS and SINS. This exercise shows that disc parameters are particularly robust, but bulge parameters are prone to errors if its effective radius is small compared to the seeing radius, and might suffer from systematic effects. For instance, the bulge-to-total luminosity ratio is systematically overestimated, on average, by 0.05 (i.e. 5 per cent of the galaxy total luminosity). In this low-resolution regime, the

MOJAVE - XIV. Shapes and opening angles of AGN jets

NASA Astrophysics Data System (ADS)

Pushkarev, A. B.; Kovalev, Y. Y.; Lister, M. L.; Savolainen, T.

2017-07-01

We present 15 GHz stacked VLBA images of 373 jets associated with active galactic nuclei (AGNs) having at least five observing epochs within a 20 yr time interval 1994-2015 from the Monitoring Of Jets in Active galactic nuclei with VLBA Experiments (MOJAVE) programme and/or its precursor, the 2-cm VLBA Survey. These data are supplemented by 1.4 GHz single-epoch VLBA observations of 135 MOJAVE AGNs to probe larger scale jet structures. The typical jet geometry is found to be close to conical on scales from hundreds to thousands of parsecs, while a number of galaxies show quasi-parabolic streamlines on smaller scales. A true jet geometry in a considerable fraction of AGNs appears only after stacking epochs over several years. The jets with significant radial accelerated motion undergo more active collimation. We have analysed total intensity jet profiles transverse to the local jet ridgeline and derived both apparent and intrinsic opening angles of the flows, with medians of 21.5° and 1.3°, respectively. The Fermi LAT-detected gamma-ray AGNs in our sample have, on average, wider apparent and narrower intrinsic opening angle, and smaller viewing angle than non-LAT-detected AGNs. We have established a highly significant correlation between the apparent opening angle and gamma-ray luminosity, driven by Doppler beaming and projection effects.

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

NASA Astrophysics Data System (ADS)

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 < z < 0.06) unobscured AGN to study the link between AGN and their host galaxies. The primary CARS observations come from the MUSE integral field unit on the VLT, and complementary multi-wavelength observations have been approved from SOFIA, Chandra, VLA, HST, and others. We compare the stellar kinematics of active galaxies from CARS to similar inactive galaxies. We then use kinemetry to estimate the degree of dynamical disturbance, to determine whether active nuclei are preferentially hosted in dynamically disturbed or merging systems. Finally, we highlight the discovery of an AGN that has changed spectral 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

ISO Key Project: Exploring the Full Range of Quasar/AGN Properties

NASA Technical Reports Server (NTRS)

Wilkes, B.

2001-01-01

The origin of the infrared emission in Active Galactic Nuclei (AGN), whose strength is comparable to the optical/ultra-violet (OUV) emission, is generally thought to be a combination of thermal emission from dust and non-thermal, synchrotron emission. Although data are sparse, particularly in the far-infrared, the broad wavelength range of this emission suggests a wide range of temperatures and a combination of AGN and starburst heating mechanisms. The strength of the non-thermal emission is expected to be related to the radio emission. While this scenario is well-established, basic questions, such as the spatial and temperature distribution of the dust, the relative importance of AGN and starburst heating, and the significance of the non-thermal contribution, remain largely undetermined. The wide wavelength range of the Infrared Space Observatory (ISO) combined with its arcmin spatial resolution and increased sensitivity facilitated the observation of a larger subset of the AGN population than previously covered, allowing these questions to be investigated in more detail. This paper will review the spectral energy distributions (SED) of AGN with particular emphasis on the infrared emission and on ISO contributions to our knowledge. Preliminary results from ISO observations of X-ray selected and high-redshift AGN will be described.

Short time-scale optical variability properties of the largest AGN sample observed with Kepler/K2

NASA Astrophysics Data System (ADS)

Aranzana, E.; Körding, E.; Uttley, P.; Scaringi, S.; Bloemen, S.

2018-05-01

We present the first short time-scale (˜hours to days) optical variability study of a large sample of active galactic nuclei (AGNs) observed with the Kepler/K2 mission. The sample contains 252 AGN observed over four campaigns with ˜30 min cadence selected from the Million Quasar Catalogue with R magnitude <19. We performed time series analysis to determine their variability properties by means of the power spectral densities (PSDs) and applied Monte Carlo techniques to find the best model parameters that fit the observed power spectra. A power-law model is sufficient to describe all the PSDs of our sample. A variety of power-law slopes were found indicating that there is not a universal slope for all AGNs. We find that the rest-frame amplitude variability in the frequency range of 6 × 10-6-10-4 Hz varies from 1to10 per cent with an average of 1.7 per cent. We explore correlations between the variability amplitude and key parameters of the AGN, finding a significant correlation of rest-frame short-term variability amplitude with redshift. We attribute this effect to the known `bluer when brighter' variability of quasars combined with the fixed bandpass of Kepler data. This study also enables us to distinguish between Seyferts and blazars and confirm AGN candidates. For our study, we have compared results obtained from light curves extracted using different aperture sizes and with and without detrending. We find that limited detrending of the optimal photometric precision light curve is the best approach, although some systematic effects still remain present.

Anti-cancer and other bioactivities of Korean Angelica gigas Nakai (AGN) and its major pyranocoumarin compounds.

PubMed

Zhang, Jinhui; Li, Li; Jiang, Cheng; Xing, Chengguo; Kim, Sung-Hoon; Lü, Junxuan

2012-12-01

Korean Angelica gigas Nakai (AGN) is a major medicinal herb used in Asian countries such as Korea and China. Traditionally, its dried root has been used to treat anemia, pain, infection and articular rheumatism in Korea, most often through boiling in water to prepare the dosage forms. The pyranocoumarin compound decursin and its isomer decursinol angelate (DA) are the major chemical components in the alcoholic extracts of the root of AGN. The in vitro anti-tumor activities of decursin and/or DA against prostate cancer, lung cancer, breast cancer, colon cancer, bladder cancer, sarcoma, myeloma and leukemia have been increasingly reported in the past decade whereas the in vivo efficacy in mouse models was established only for a few organ sites. Preliminary pharmacokinetic studies by us and others in rodent models indicated that decursinol (DOH), which has much less in vitro direct anticancer activities by itself, is the major and rapid in vivo hydrolysis metabolite of both decursin and DA. Besides decursin, DA and DOH, other chemical components in AGN such as polysaccharides and polyacetylenes have been reported to exert anti-cancer and anti-inflammation activities as well. We systematically reviewed the published literature on the anti-cancer and other bio-activities effects of AGN extract and decursin, DA and DOH, as well as other chemicals identified from AGN. Although a number of areas are identified that merit further investigation, one critical need is first-in-human studies of the pharmacokinetics of decursin/DA to determine whether humans differ from rodents in absorption and metabolism of these compounds.

THE GLOBAL IMPLICATIONS OF THE HARD EXCESS. II. ANALYSIS OF THE LOCAL POPULATION OF RADIO-QUIET AGNs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tatum, M. M.; Turner, T. J.; Reeves, J. N.

2016-02-10

Active galactic nuclei (AGNs) show evidence for reprocessing gas, outflowing from the accreting black hole. The combined effects of absorption and scattering from the circumnuclear material likely explain the “hard excess” of X-ray emission above 20 keV, compared with the extrapolation of spectra from lower X-ray energies. In a recent Suzaku study, we established that the ubiquitous hard excess in hard, X-ray-selected, radio-quiet type 1 AGNs is consistent with a reprocessing of the X-ray continuum in an ensemble of clouds, located tens to hundreds of gravitational radii from the nuclear black hole. Here we add hard X-ray-selected, type 2 AGNsmore » to extend our original study and show that the gross X-ray spectral properties of the entire local population of radio-quiet AGNs may be described by a simple unified scheme. We find a broad, continuous distribution of spectral hardness ratio and Fe Kα equivalent width across all AGN types, which can be reproduced by varying the observer's sightline through a single, simple model cloud ensemble, provided that the radiative transfer through the model cloud distribution includes not only photoelectric absorption but also three-dimensional (3D) Compton scattering. Variation in other parameters of the cloud distribution, such as column density or ionization, should be expected between AGNs, but such variation is not required to explain the gross X-ray spectral properties.« less

How fast can an AGN shut down? XMM-Newton observation of IC 2497

NASA Astrophysics Data System (ADS)

Schawinski, Kevin

2008-10-01

We propose to observe IC 2497 with XMM-Newton to detect, or rule out, an obscured AGN that might account for the illumination of `Hanny's Voorwerp'. The Voorwerp is a highly ionised cloud of gas extended over 15-25 kpc next to the spiral galaxy IC 2497. There is no source of ionisation within the Voorwerp, implicating a luminous 1E44 erg/s AGN in IC 2497 as the source. Swift XRT observations do not yield a detection, allowing the presence of a highly obscured, sufficiently luminous AGN. With 34 ksec of XMM observations, we could detect an obscured AGN down to 1E42 erg/s. We can thus either locate an obscured AGN, or we can for the first time constrain the shutdown time scale for a powerful AGN, as it drops by a factor of 100 in luminosity in 1E5 years.

No evidence for a significant AGN contribution to cosmic hydrogen reionization

NASA Astrophysics Data System (ADS)

Parsa, Shaghayegh; Dunlop, James S.; McLure, Ross J.

2018-03-01

We reinvestigate a claimed sample of 22 X-ray detected active galactic nuclei (AGN) at redshifts z > 4, which has reignited the debate as to whether young galaxies or AGN reionized the Universe. These sources lie within the Great Observatories Origins Deep Survey-South (GOODS-S)/Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS) field, and we examine both the robustness of the claimed X-ray detections (within the Chandra 4Ms imaging) and perform an independent analysis of the photometric redshifts of the optical/infrared counterparts. We confirm the reality of only 15 of the 22 reported X-ray detections, and moreover find that only 12 of the 22 optical/infrared counterpart galaxies actually lie robustly at z > 4. Combining these results we find convincing evidence for only seven X-ray AGN at z > 4 in the GOODS-S field, of which only one lies at z > 5. We recalculate the evolving far-ultraviolet (1500 Å) luminosity density produced by AGN at high redshift, and find that it declines rapidly from z ≃ 4 to z ≃ 6, in agreement with several other recent studies of the evolving AGN luminosity function. The associated rapid decline in inferred hydrogen ionizing emissivity contributed by AGN falls an order-of-magnitude short of the level required to maintain hydrogen ionization at z ≃ 6. We conclude that all available evidence continues to favour a scenario in which young galaxies reionized the Universe, with AGN making, at most, a very minor contribution to cosmic hydrogen reionization.

Long term multiwavelength studies of the corona/disc connection in AGN

NASA Astrophysics Data System (ADS)

Buisson, D.; Lohfink, A.; Alston, W.; Fabian, A.; Gallo, L.; Kara, E.; Zoghbi, A.; Wilkins, D.; Miller, J.; Cackett, E.

2017-10-01

One way of increasing our understanding of AGN is determining the nature of the connection between the optical/UV emitting accretion disc and the X-ray emitting corona. Studies of variability in these two bands are a key tool for gaining insight into the processes involved. We will present results from a sample of long-term AGN monitoring campaigns in the optical, UV and X-ray with Swift. In particular, we will explore UV/optical-X-ray correlations and associated time lags. We will compare these measurements and the UV/optical RMS spectra with theoretical reprocessing models and confront recent claims of the observed lags being longer than those which are expected for a standard thin disc. Additionally, a new Swift monitoring campaign of the z=2 quasar PG 1247+267 allows us to probe the shorter wavelengths at the peak of the accretion disc spectrum, providing information on the region of the disc closest to the black hole. However, not all AGN show such correlations, including IRAS 13224-3809, the subject of a recent 1.5 Ms XMM observation. Using this and other examples, we will explore the possible reasons for the lack of observed correlation.

VizieR Online Data Catalog: Gamma-ray AGN type determination (Hassan+, 2013)

NASA Astrophysics Data System (ADS)

Hassan, T.; Mirabal, N.; Contreras, J. L.; Oya, I.

2013-11-01

In this paper, we employ Support Vector Machines (SVMs) and Random Forest (RF) that embody two of the most robust supervised learning algorithms available today. We are interested in building classifiers that can distinguish between two AGN classes: BL Lacs and FSRQs. In the 2FGL, there is a total set of 1074 identified/associated AGN objects with the following labels: 'bzb' (BL Lacs), 'bzq' (FSRQs), 'agn' (other non-blazar AGN) and 'agu' (active galaxies of uncertain type). From this global set, we group the identified/associated blazars ('bzb' and 'bzq' labels) as the training/testing set of our algorithms. (2 data files).

Shedding New Light on the Innermost Regions of AGN with XMM, Suzaku and NuSTAR

NASA Astrophysics Data System (ADS)

Brenneman, Laura

We request funding for two years ($257,041 in total) in support of accepted XMM- Newton and Suzaku observations of six bright, nearby active galactic nuclei (AGN): MCG-6-30-15, Ark 120, SWIFT J2127.4+5654, 3C120, NGC 4151 and IC 4329A. The first four of these AGN are to be observed simultaneously with XMM and NuSTAR during XMM's AO11 cycle, while the last two AGN will be studied simultaneously with Suzaku and NuSTAR during Suzaku's AO7 cycle. All six AGN observations were approved with priority A, and our observing campaign totals 1.14 Msec of exposure time. The XMM and Suzaku programs share four common goals: (1) to measure the angular momenta of the supermassive black holes (SMBHs) at the hearts of these active galaxies, (2) to accurately characterize the physical properties of the poorly understood inner accretion disk/corona region in these AGN, and (3) to identify the driver(s) of the spectral variability across multiple physical timescales in these systems, and (4) to examine correlations that exist between the various physical properties of these SMBHs and their surroundings. These three science goals address a critical component of NASA's Physics of the Cosmos mission: "the behavior of matter and energy in extreme environments." The high prioritization and long exposures of our awarded XMM and Suzaku observations underscore the scientific merit of these goals, as judged by the high-energy astronomy community. Our observing campaign will yield simultaneous broad-band X-ray spectra (0.2-80 keV) of these AGN with the best signal-to-noise and spectral resolution ever obtained across this energy range, guaranteeing new insights into the physics at work in the innermost regions around SMBHs. Using a combination of timing analysis and detailed spectral modeling, we will achieve the first truly accurate understanding of the nature of the X-ray continuum in AGN. The low-background, high-energy data from NuSTAR in tandem with the sensitivity at lower energies from

Explanatory Unification by Proofs in School Mathematics

ERIC Educational Resources Information Center

Komatsu, Kotaro; Fujita, Taro; Jones, Keith; Naoki, Sue

2018-01-01

Kitcher's idea of 'explanatory unification', while originally proposed in the philosophy of science, may also be relevant to mathematics education, as a way of enhancing student thinking and achieving classroom activity that is closer to authentic mathematical practice. There is, however, no mathematics education research treating explanatory…

Unveiling slim accretion disc in AGN through X-ray and Infrared observations

NASA Astrophysics Data System (ADS)

Castelló-Mor, Núria; Kaspi, Shai; Netzer, Hagai; Du, Pu; Hu, Chen; Ho, Luis C.; Bai, Jin-Ming; Bian, Wei-Hao; Yuan, Ye-Fei; Wang, Jian-Min

2017-05-01

In this work, which is a continuation of Castelló-Mor et al., we present new X-ray and infrared (IR) data for a sample of active galactic nuclei (AGN) covering a wide range in Eddington ratio over a small luminosity range. In particular, we rigorously explore the dependence of the optical-to-X-ray spectral index αOX and the IR-to-optical spectral index on the dimensionless accretion rate, \\dot{M} = \\dot{m}/η, where \\dot{m} = LAGN/LEdd and η is the mass-to-radiation conversion efficiency, in low- and high-accretion rate sources. We find that the spectral energy distribution (SED) of the faster accreting sources is surprisingly similar to those from the comparison sample of sources with lower accretion rate. In particular: (I) The optical-to-UV AGN SED of slow and fast accreting AGN can be fitted with thin accretion disc (AD) models. (II) The value of αOX is very similar in slow and fast accreting systems up to a dimensionless accretion rate \\dot{M}c ˜ 10. We only find a correlation between αOX and \\dot{M} for sources with \\dot{M} > \\dot{M}c. In such cases, the faster accreting sources appear to have systematically larger αOX values. (III) We also find that the torus in the faster accreting systems seems to be less efficient in reprocessing the primary AGN radiation having lower IR-to-optical spectral slopes. These findings, failing to recover the predicted differences between the SEDs of slim and thin ADs within the observed spectral window, suggest that additional physical processes or very special geometry act to reduce the extreme-UV radiation in fast accreting AGN. This may be related to photon trapping, strong winds and perhaps other yet unknown physical processes.

Clustering of moderate luminosity X-ray-selected type 1 and type 2 AGNs at z ∼ 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allevato, V.; Finoguenov, A.; Civano, F.

2014-11-20

We investigate, for the first time at z ∼ 3, the clustering properties of 189 Type 1 and 157 Type 2 X-ray active galactic nuclei (AGNs) of moderate luminosity ((L {sub bol}) = 10{sup 45.3} erg s{sup –1}), with photometric or spectroscopic redshifts in the range 2.2 < z < 6.8. These samples are based on Chandra and XMM-Newton data in COSMOS. We find that Type 1 and Type 2 COSMOS AGNs at z ∼ 3 inhabit DMHs with typical mass of log M{sub h} = 12.84{sub −0.11}{sup +0.10} and 11.73{sub −0.45}{sup +0.39} h {sup –1} M {sub ☉}, respectively.more » This result requires a drop in the halo masses of Type 1 and 2 COSMOS AGNs at z ∼ 3 compared to z ≲ 2 XMM-COSMOS AGNs with similar luminosities. Additionally, we infer that unobscured COSMOS AGNs at z ∼ 3 reside in 10 times more massive halos compared to obscured COSMOS AGNs, at the 2.6σ level. This result extends to z ∼ 3 the results found in COSMOS at z ≲ 2, and rules out the picture in which obscuration is purely an orientation effect. A model which assumes that the AGNs activity is triggered by major mergers is quite successful in predicting both the low halo mass of COSMOS AGNs and the typical mass of luminous SDSS quasars at z ∼ 3, with the latter inhabiting more massive halos respect to moderate luminosity AGNs. Alternatively we can argue, at least for Type 1 COSMOS AGNs, that they are possibly representative of an early phase of fast (i.e., Eddington limited) BH growth induced by cosmic cold flows or disk instabilities. Given the moderate luminosity, these new fast growing BHs have masses of ∼10{sup 7-8} M {sub ☉} at z ∼ 3 which might evolve into ∼10{sup 8.5-9} M {sub ☉} mass BHs at z = 0. Following our clustering measurements, we argue that this fast BH growth at z ∼ 3 in AGNs with moderate luminosity occurs in DMHs with typical mass of ∼ 6× 10{sup 12} h {sup –1} M {sub ☉}.« less

AGN Science with STROBE-X

NASA Astrophysics Data System (ADS)

Ballantyne, David; Balokovic, Mislav; Garcia, Javier; Koss, Michael; STROBE-X

2018-01-01

The probe concept STROBE-X, with its combination of large collecting area, wide-field monitor, broad bandpass, and rapid timing capability, is a powerful tool for studying many aspects of AGN astrophysics. This unique combination of features opens up the possibility for studying AGNs in ways current and other future missions are unable to accomplish. Here, we show a few of the novel new investigations made possible by STROBE-X: probing the structure of the BLR and torus with reverberation of the narrow Fe Kα line and line-of-sight column density, tracking changes in coronal parameters, investigating the origin of the soft excess, Fe Kα emission line surveys, and efficient Compton-thick characterization. Additional ideas and suggestions are always welcome and can be communicated to any member of the STROBE-X team.

AGN Outflow Shocks on Bonnor–Ebert Spheres

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dugan, Zachary; Silk, Joseph; Rahman, Mubdi

Feedback from active galactic nuclei (AGNs) 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 spheres and examine gravitational collapse and ablation. We test AGN wind velocities ranging from 300 to 3000 km s{sup −1} and wind densities ranging from 0.5 to 10 m {sub p} cm{sup −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 0.01more » 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 they also cause star formation to occur on a much shorter timescale and with increased velocities of the newly formed stars. We find a threshold ram pressure of ∼2 × 10{sup −8} dyn cm{sup −2} above which stars are not formed because the resulting clumps have internal velocities large enough to prevent collapse. Our results indicate that simultaneous positive and negative feedback will be possible in a single galaxy, as AGN wind parameters will vary with location within a galaxy.« less

Unification with vector-like fermions and signals at LHC

NASA Astrophysics Data System (ADS)

Bhattacherjee, Biplob; Byakti, Pritibhajan; Kushwaha, Ashwani; Vempati, Sudhir K.

2018-05-01

We look for minimal extensions of Standard Model with vector like fermions leading to precision unification of gauge couplings. Constraints from proton decay, Higgs stability and perturbativity are considered. The simplest models contain several copies of vector fermions in two different (incomplete) representations. Some of these models encompass Type III seesaw mechanism for neutrino masses whereas some others have a dark matter candidate. In all the models, at least one of the candidates has non-trivial representation under SU(3)color. In the limit of vanishing Yukawa couplings, new QCD bound states are formed, which can be probed at LHC. The present limits based on results from 13 TeV already probe these particles for masses around a TeV. Similar models can be constructed with three or four vector representations, examples of which are presented.

The shape of the cosmic X-ray background: nuclear starburst discs and the redshift evolution of AGN obscuration

NASA Astrophysics Data System (ADS)

Gohil, R.; Ballantyne, D. R.

2018-04-01

A significant number of active galactic nuclei (AGNs) are observed to be hidden behind dust and gas. The distribution of material around AGNs plays an important role in modelling the cosmic X-ray background (CXB), especially the fraction of type 2 AGNs (f2). One of the possible explanations for obscuration in Seyfert galaxies at intermediate redshifts is dusty starburst discs. We compute the two-dimensional (2D) hydrostatic structure of 768 nuclear starburst discs (NSDs) under various physical conditions and also the distribution of column density along the line of sight (NH) associated with these discs. Then the NH distribution is evolved with redshift by using the redshift-dependent distribution function of input parameters. Parameter f2 shows a strong positive evolution up to z = 2, but only a weak level of enhancement at higher z. The Compton-thin and Compton-thick AGN fractions associated with these starburst regions increase ∝ (1 + z)δ, where δ is estimated to be 1.12 and 1.45, respectively. The reflection parameter Rf associated with column density NH ≥ 1023.5 cm-2 extends from 0.13 at z = 0 to 0.58 at z = 4. A CXB model employing this evolving NH distribution indicates that more compact (Rout < 120 pc) NSDs provide a better fit to the CXB. In addition to `Seyfert-like' AGNs obscured by nuclear starbursts, we predict that 40-60 per cent of quasars must be Compton-thick to produce a peak of the CXB spectrum within the observational uncertainty. The predicted total number counts of AGNs in 8-24 keV bands are in fair agreement with observations from the Nuclear Spectroscopic Telescope Array (NuSTAR).

Coeval Starburst and AGN Activity in the CDFS

NASA Astrophysics Data System (ADS)

Brusa, M.; Fiore, F.

2009-10-01

Here we present a study on the host galaxies properties of obscured Active Galactic Nuclei (AGN) detected in the CDFS 1Ms observation and for which deep K-band observations obtained with ISAAC@VLT are available. The aim of this study is to characterize the host galaxies properties of obscured AGN in terms of their stellar masses, star formation rates, and specific star formation rates. To this purpose we refined the X-ray/optical association of 179 1 Ms sources in the MUSIC area, using a three-bands (optical, K, and IRAC) catalog for the counterparts search and we derived the rest frame properties from SED fitting. We found that the host of obscured AGN at z>1 are associated with luminous, massive, red galaxies with significant star formation rates episodes still ongoing in about 50% of the sample.

X-Ray Bolometric Corrections for Compton-thick Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Brightman, M.; Baloković, M.; Ballantyne, D. R.; Bauer, F. E.; Boorman, P.; Buchner, J.; Brandt, W. N.; Comastri, A.; Del Moro, A.; Farrah, D.; Gandhi, P.; Harrison, F. A.; Koss, M.; Lanz, L.; Masini, A.; Ricci, C.; Stern, D.; Vasudevan, R.; Walton, D. J.

2017-07-01

We present X-ray bolometric correction factors, {κ }{Bol} (≡{L}{Bol}/{L}{{X}}), for Compton-thick (CT) active galactic nuclei (AGNs) with the aim of testing AGN torus models, probing orientation effects, and estimating the bolometric output of the most obscured AGNs. We adopt bolometric luminosities, {L}{Bol}, from literature infrared (IR) torus modeling and compile published intrinsic 2-10 keV X-ray luminosities, {L}{{X}}, from X-ray torus modeling of NuSTAR data. Our sample consists of 10 local CT AGNs, where both of these estimates are available. We test for systematic differences in {κ }{Bol} values produced when using two widely used IR torus models and two widely used X-ray torus models, finding consistency within the uncertainties. We find that the mean {κ }{Bol} of our sample in the range of {L}{Bol}≈ {10}42{--}{10}45 {erg} {{{s}}}-1 is log10 {κ }{Bol} = 1.44 ± 0.12 with an intrinsic scatter of ˜0.2 dex, and that our derived {κ }{Bol} values are consistent with previously established relationships between {κ }{Bol} and {L}{Bol} and {κ }{Bol} and Eddington ratio ({λ }{Edd}). We investigate if {κ }{Bol} is dependent on {N}{{H}} by comparing our results on CT AGNs to published results on less-obscured AGNs, finding no significant dependence. Since many of our sample are megamaser AGNs, known to be viewed edge-on, and furthermore under the assumptions of AGN unification whereby unobscured AGNs are viewed face-on, our result implies that the X-ray emitting corona is not strongly anisotropic. Finally, we present {κ }{Bol} values for CT AGNs identified in X-ray surveys as a function of their observed {L}{{X}}, where an estimate of their intrinsic {L}{{X}} is not available, and redshift, useful for estimating the bolometric output of the most obscured AGNs across cosmic time.

The NuSTAR Serendipitous Survey: Hunting for the Most Extreme Obscured AGN at >10 keV

NASA Astrophysics Data System (ADS)

Lansbury, G. B.; Alexander, D. M.; Aird, J.; Gandhi, P.; Stern, D.; Koss, M.; Lamperti, I.; Ajello, M.; Annuar, A.; Assef, R. J.; Ballantyne, D. R.; Baloković, M.; Bauer, F. E.; Brandt, W. N.; Brightman, M.; Chen, C.-T. J.; Civano, F.; Comastri, A.; Del Moro, A.; Fuentes, C.; Harrison, F. A.; Marchesi, S.; Masini, A.; Mullaney, J. R.; Ricci, C.; Saez, C.; Tomsick, J. A.; Treister, E.; Walton, D. J.; Zappacosta, L.

2017-09-01

We identify sources with extremely hard X-ray spectra (I.e., with photon indices of {{Γ }}≲ 0.6) in the 13 deg2 NuSTAR serendipitous survey, to search for the most highly obscured active galactic nuclei (AGNs) detected at > 10 {keV}. Eight extreme NuSTAR sources are identified, and we use the NuSTAR data in combination with lower-energy X-ray observations (from Chandra, Swift XRT, and XMM-Newton) to characterize the broadband (0.5-24 keV) X-ray spectra. We find that all of the extreme sources are highly obscured AGNs, including three robust Compton-thick (CT; {N}{{H}}> 1.5× {10}24 cm-2) AGNs at low redshift (z< 0.1) and a likely CT AGN at higher redshift (z = 0.16). Most of the extreme sources would not have been identified as highly obscured based on the low-energy (< 10 keV) X-ray coverage alone. The multiwavelength properties (e.g., optical spectra and X-ray-mid-IR luminosity ratios) provide further support for the eight sources being significantly obscured. Correcting for absorption, the intrinsic rest-frame 10-40 keV luminosities of the extreme sources cover a broad range, from ≈ 5× {10}42 to 1045 erg s-1. The estimated number counts of CT AGNs in the NuSTAR serendipitous survey are in broad agreement with model expectations based on previous X-ray surveys, except for the lowest redshifts (z< 0.07), where we measure a high CT fraction of {f}{CT}{obs}={30}-12+16 % . For the small sample of CT AGNs, we find a high fraction of galaxy major mergers (50% ± 33%) compared to control samples of “normal” AGNs.

AGN-2979, an inhibitor of tryptophan hydroxylase activation, does not affect serotonin synthesis in Flinders Sensitive Line rats, a rat model of depression, but produces a significant effect in Flinders Resistant Line rats

PubMed Central

Kanemaru, Kazuya; Nishi, Kyoko; Diksic, Mirko

2009-01-01

The neurotransmitter, serotonin, is involved in several brain functions, including both normal, physiological functions, and pathophysiological functions. Alterations in any of the normal parameters of serotonergic neurotransmission can produce several different psychiatric disorders, including major depression. In many instances, brain neurochemical variables are not able to be studied properly in humans, thus making the use of good animal models extremely valuable. One of these animal models is the Flinders Sensitive Line (FSL) of rats, which has face, predictive and constructive validities in relation to human depression. The objective of this study was to quantify the effect of the tryptophan hydroxylase (TPH) activation inhibitor, AGN-2979, on the FSL rats (rats with depression-like behaviour), and compare it to the effect on the Flinders Resistant Line (FRL) of rats used as the control rats. The effect was evaluated by measuring changes in regional serotonin synthesis in the vehicle treated rats (FSL-VEH and FRL-VEH) relative to those measured in the AGN-2979 treated rats (FSL-AGN and FRL-AGN). Regional serotonin synthesis was measured autoradiographically in more than thirty brain regions. The measurements were performed using α-[14C]methyl-L-tryptophan as the tracer. The results indicate that AGN-2979 did not produce a significant reduction of TPH activity in the AGN-2979 group relative to the vehicle group (a reduction would have been observed if there had been an activation of TPH by the experimental set up) in the FSL rats. On the other hand, there was a highly significant reduction of synthesis in the FRL rats treated by AGN-2979, relative to the vehicle group. Together, the results demonstrate that in the FSL rats, AGN-2979 does not affect serotonin synthesis. This suggests that there was no activation of TPH in the FSL rats during the experimental procedure, but such activation did occur in the FRL rats. Because of this finding, it could be

Twenty-two emission-line AGNs from the HEAO-1 X-ray survey

NASA Technical Reports Server (NTRS)

Remillard, R. A.; Bradt, H. V. D.; Brissenden, R. J. V.; Buckley, D. A. H.; Roberts, W.; Schwartz, D. A.; Stroozas, B. A.; Tuohy, I. R.

1993-01-01

We report 22 emission-line AGN as bright, hard X-ray sources. All of them appear to be new classifications with the exception of one peculiar IRAS source which is a known quasar and has no published spectrum. This sample exhibits a rich diversity in optical spectral properties and luminosities, ranging from a powerful broad-absorption-line quasar to a weak nucleus embedded in a nearby NGC galaxy. Two cases confer X-ray luminosities in excess of 10 exp 47 erg/s. However, there is a degree of uncertainty in the X-ray identification for the AGN fainter than V about 16.5. Optically, several AGN exhibit very strong Fe II emission. One Seyfert galaxy with substantial radio flux is an exception to the common association of strong Fe II emission and radio-quiet AGN. The previously recognized IRAS quasar shows extreme velocities in the profiles of the forbidden lines; the 0 III pair is broadened to the point that the lines are blended. Several of these AGN show evidence of intrinsic obscuration, illustrating the effectiveness of hard X-ray surveys in locating AGN through high column density.

Authenticity and Unification in Quechua Language Planning.

ERIC Educational Resources Information Center

Hornberger, Nancy H.; King, Kendall

1998-01-01

Examines the potentially problematic tension between the goals of authenticity and unification in Quechua-language planning. One case study examines the orthographic debate that arose in Peru, and the second case study concerns two indigenous communities in Saraguro in the Southern Ecuadorian highlands where Spanish predominates but two Quichua…

The AGN Impact on the Circumgalactic Medium of Cen A

NASA Astrophysics Data System (ADS)

Lehner, Nicolas

2017-08-01

There seems to be broad agreement that feedback from AGN plays a critical role in transforming massive star forming galaxies to quiescent ones and keeping them quenched thereafter. Through the emission of copious amounts of radiation emitted in the active QSO/AGN phase and the deposition of thermal and mechanical energy on scales of hundreds of kpc during the radio phase, AGN feedback shifts the temperatures and ionization states of the gas in the circumgalactic medium (CGM) of these galaxies to higher energies, suppressing cooling that might otherwise provide fuel for new star formation. We propose to observe absorption lines from the CGM of the nearby, very well-studied giant radio-lobe galaxy Cen A to search directly for the signal of AGN feedback impacting the CGM of a galaxy. We will target 4 background QSOs projected 270-340 kpc from the galaxy at a range of azimuthal angles relative to the 300 kpc-long jets and 1 control sight line well away from the jets. These spectra will provide probes of the ionization balance and kinematic structure of the cool/warm CGM. This will be the first attempt to dissect the cool/warm gas in a CGM undergoing interactions with an active AGN.

Environment Study of AGNs at z = 0.3 to 3.0 Using the Japanese Virtual Observatory

NASA Astrophysics Data System (ADS)

Shirasaki, Y.; Ohishi, M.; Mizumoto, Y.; Takata, T.; Tanaka, M.; Yasuda, N.

2010-12-01

We present a science use case of Virtual Observatory, which was achieved to examine an environment of AGN up to redshift of 3.0. We used the Japanese Virtual Observatory (JVO) to obtain Subaru Suprime-Cam images around known AGNs. According to the hierarchical galaxy formation model, AGNs are expected to be found in an environment of higher galaxy density than that of typical galaxies. The current observations, however, indicate that AGNs do not reside in a particularly high density environment. We investigated ˜1000 AGNs, which is about ten times larger samples than the other studies covering the redshifts larger than 0.6. We successfully found significant excess of galaxies around AGNs at redshifts of 0.3 to 1.8. If this work was done in a classical manner, that is, raw data were retrieved from the archive through a form-based web interface in an interactive way, and the data were reduced on a low performance computer, it might take several years to finish it. Since the Virtual Observatory system is accessible through a standard interface, it is easy to query and retrieve data in an automatic way. We constructed a pipeline for retrieving the data and calculating the galaxy number density around a given coordinate. This procedure was executed in parallel on ˜10 quad core PCs, and it took only one day for obtaining the final result. Our result implies that the Virtual Observatory can be a powerful tool to do an astronomical research based on large amount of data.

Towards A Complete Census of the Compton-thick AGN Population in our Cosmic Backyard

NASA Astrophysics Data System (ADS)

Annuar, Ady

2016-09-01

We propose for Chandra and NuSTAR observations of two local AGNs to characterise their obscuring properties. We are using Chandra and NuSTAR to form the first complete measurement of the column density (N_H) distribution of AGN at D<15 Mpc. Even at this distance the distribution was only 50% complete. We have recently improved this, and found a Compton-thick (CT) AGN fraction of >35%. We also found that Chandra resolution is key in resolving the AGN from off-nuclear X-ray sources. When combined with NuSTAR, this allow us to accurately characterise the broadband spectrum of the AGN, and identify it as CT. These new observations will provide Chandra data for all D<15Mpc AGNs and boost up the N_H distribution up to 85% complete. This will be fully completed with future NuSTAR observations.

A gas-rich AGN near the centre of a galaxy cluster at z ~ 1.4

NASA Astrophysics Data System (ADS)

Casasola, V.; Magrini, L.; Combes, F.; Mignano, A.; Sani, E.; Paladino, R.; Fontani, F.

2013-10-01

Context. The formation of the first virialized structures in overdensities dates back to ~9 Gyr ago, i.e. in the redshift range z ~ 1.4-1.6. Some models of structure formation predict that the star formation activity in clusters was high at that epoch, implying large reservoirs of cold molecular gas. Aims: Aiming at finding a trace of this expected high molecular gas content in primeval clusters, we searched for the 12CO(2-1) line emission in the most luminous active galactic nucleus (AGN) of the cluster around the radio galaxy 7C 1756+6520 at z ~ 1.4, one of the farthest spectroscopic confirmed clusters. This AGN, called AGN.1317, is located in the neighbourhood of the central radio galaxy at a projected distance of ~780 kpc. Methods: The IRAM Plateau de Bure Interferometer was used to investigate the molecular gas quantity in AGN.1317, observing the 12CO(2-1) emission line. Results: We detect CO emission in an AGN belonging to a galaxy cluster at z ~ 1.4. We measured a molecular gas mass of 1.1 × 1010M⊙, comparable to that found in submillimeter galaxies. In optical images, AGN.1317 does not seem to be part of a galaxy interaction or merger. We also derived the nearly instantaneous star formation rate (SFR) from Hα flux obtaining a SFR ~ 65 M⊙ yr-1. This suggests that AGN.1317 is actively forming stars and will exhaust its reservoir of cold gas in ~0.2-1.0 Gyr. Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).Reduced IRAM data 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/558/A60

The combined effect of AGN and supernovae feedback in launching massive molecular outflows in high-redshift galaxies

NASA Astrophysics Data System (ADS)

Biernacki, Pawel; Teyssier, Romain

2018-04-01

We have recently improved our model of active galactic nucleus (AGN) by attaching the supermassive black hole (SMBH) to a massive nuclear star cluster (NSC). Here, we study the effects of this new model in massive, gas-rich galaxies with several simulations of different feedback recipes with the hydrodynamics code RAMSES. These simulations are compared to a reference simulation without any feedback, in which the cooling halo gas is quickly consumed in a burst of star formation. In the presence of strong supernovae (SN) feedback, we observe the formation of a galactic fountain that regulates star formation over a longer period, but without halting it. If only AGN feedback is considered, as soon as the SMBH reaches a critical mass, strong outflows of hot gas are launched and prevent the cooling halo gas from reaching the disc, thus efficiently halting star formation, leading to the so-called `quenching'. If both feedback mechanisms act in tandem, we observe a non-linear coupling, in the sense that the dense gas in the supernovae-powered galactic fountain is propelled by the hot outflow powered by the AGN at much larger radii than without AGN. We argue that these particular outflows are able to unbind dense gas from the galactic halo, thanks to the combined effect of SN and AGN feedback. We speculate that this mechanism occurs at the end of the fast growing phase of SMBH, and is at the origin of the dense molecular outflows observed in many massive high-redshift galaxies.

Evidence for Merger-driven Growth in Luminous, High- z, Obscured AGNs in the CANDELS/COSMOS Field

DOE PAGES

Donley, J. L.; Kartaltepe, J.; Kocevski, D.; ...

2018-01-23

While major mergers have long been proposed as a driver of both active galactic nucleus (AGN) activity and themore » $${M}_{\\mathrm{BH}}\\mbox{--}{\\sigma }_{\\mathrm{bulge}}$$ relation, studies of moderate to high-redshift Seyfert-luminosity AGN hosts have found little evidence for enhanced rates of interactions. However, both theory and observation suggest that while these AGNs may be fueled by stochastic accretion and secular processes, high-luminosity, high-redshift, and heavily obscured AGNs are the AGNs most likely to be merger-driven. To better sample this population of AGNs, we turn to infrared selection in the CANDELS/COSMOS field. Compared to their lower-luminosity and less obscured X-ray-only counterparts, IR-only AGNs (luminous, heavily obscured AGNs) are more likely to be classified as either irregular ($${50}_{-12}^{+12} \\% $$ versus $${9}_{-2}^{+5} \\% $$) or asymmetric ($${69}_{-13}^{+9} \\% $$ versus $${17}_{-4}^{+6} \\% $$) and are less likely to have a spheroidal component ($${31}_{-9}^{+13} \\% $$ versus $${77}_{-6}^{+4} \\% $$). Furthermore, IR-only AGNs are also significantly more likely than X-ray-only AGNs ($${75}_{-13}^{+8} \\% $$ versus $${31}_{-6}^{+6} \\% $$) to be classified either as interacting or merging in a way that significantly disturbs the host galaxy or as disturbed, though not clearly interacting or merging, which potentially represents the late stages of a major merger. Finally, this suggests that while major mergers may not contribute significantly to the fueling of Seyfert-luminosity AGNs, interactions appear to play a more dominant role in the triggering and fueling of high-luminosity heavily obscured AGNs.« less

Disks and cones: interferometry of the dusty and molecular material of AGN on parsec sales

NASA Astrophysics Data System (ADS)

Tristam, Konrad R. W.

2016-08-01

The central engine of Active Galactic Nuclei (AGN) is surrounded by dense molecular and dusty material on parsec scales. Typically referred to as the ""dusty torus"", this material is a key ingredient of AGN because it (1) provides the angle dependent obscuration of the central engine and (2) most likely plays an important role for the accretion of the material onto the supermassive black hole. Observations using interferometry in the infrared have, in the last ten years, resolved and characterised the thermal emission from the dust heated by the AGN beyond simple fits of the spectral energy distribution, leading to a great leap forward in our view of the dusty material surrounding AGN. In general the torus is parsec-sized, with a large scatter in extension between individual objects. Our studies have led to the surprising discovery that the dust emission is clearly separated into two distinct components: an inner disk-like emission region which is surrounded by a polar elongated emitter. I will demonstrate these discoveries using the results obtained for the Circinus galaxy, and discuss how the results for this galaxy compare to other well studied sources. While putting strong constraints on torus models, our findings are in good qualitative agreement with recent hydrodynamic simulations of AGN tori. The next big step forward can be expected from sub-mm interferometry and I will give a short glimpse at the results from our recent ALMA observations of the outer torus in the Circinus galaxy.

AGN Heating in Simulated Cool-core Clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Yuan; Ruszkowski, Mateusz; Bryan, Greg L., E-mail: yuanlium@umich.edu

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, more spatially concentrated than radiative cooling loss.more » 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 gigayear timescales. The cluster core is under-heated at the end of each cycle, but over-heated at the peak of the AGN outburst. During the heating-dominant phase, turbulent dissipation alone is often able to balance radiative cooling at every radius but, when this is occurs, shock waves inevitably dissipate even more energy. Our simulation explains why some clusters, such as Abell 2029, are cooling dominated, while in some other clusters, such as Perseus, various heating mechanisms including shock heating, turbulent dissipation and bubble mixing can all individually balance cooling, and together, over-heat the core.« less

Prospects for AGN Science using the ART-XC on the SRG Mission

NASA Technical Reports Server (NTRS)

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.

Spatially offset AGN candidates in the CLASS survey

NASA Astrophysics Data System (ADS)

Skipper, Chris J.; Browne, Ian W. A.

2018-04-01

Prompted by a recent claim by Barrows et al. that X-ray active galactic nuclei (AGNs) are often found significantly offset from the centres of their host galaxies, we have looked for examples of compact radio sources that are offset from the optical centroids of nearby (z < 0.2) galaxies. We have selected a sample of 345 galaxies from the Sloan Digital Sky Survey (SDSS) galaxy catalogue, which have nearby compact radio sources listed in the Cosmic-Lens All Sky Survey (CLASS) catalogue. We find only three matches (˜0.87 per cent of the sample) with offsets greater than 600 milliarcsec (mas), which is considerably fewer than we would have expected from the Barrows et al. X-ray survey. We fit our histogram of offsets with a Rayleigh distribution with σ = 60.5 mas, but find that there is an excess of objects with separations greater than ˜150 mas. Assuming that this excess represents AGNs with real offsets, we place an upper limit of ˜17 per cent on the fraction of offset AGNs in our radio-selected sample. We select 38 objects with offsets greater than 150 mas, and find they have some diverse properties: Some are well known, such as Mrk 273 and Arp 220, some have dust lanes, which may have affected the optical astrometry, and a few are strong new candidates for offset AGNs.

Why do we see Broad Lines in X-ray Absorbed, Red AGN?

NASA Astrophysics Data System (ADS)

Wilkes, B. J.; Ghosh, Himel; Cutri, R.; Hines, D.; Nelson, B.; Schmidt, G. D.; Smith, P. S.

2003-05-01

The Two Micron All-Sky Survey (2MASS) red AGN catalog has revealed a previously unknown population whose number density rivals that of optically-selected AGN as found in the many, relatively shallow surveys (e.g. PG, Hamburg). The Chandra X-ray spectra of these red, mostly broad-line AGN are hard. This, combined with their unusually high optical polarization, suggests substantial obscuration (log NH = 21-23 cm-2) toward the nuclear energy source, despite a clear view of the broad emission line region. We have expanded our Chandra-observed sub-sample to include 20 more 2MASS AGN yielding a set of 46 which includes all available optical classes. This sample is thus pre-selected for complex absorption and sufficient to study the relative X-ray and optical obscuration for each AGN class. Those observed to date continue the lack of a relation between the X-ray hardness ratio and optical class noted in our earlier sample. Combining this with X-ray spectral fits where we have sufficient counts and with our multi-wavelength data, we compare the spectral energy distributions with those of normal and other red AGN and investigate possible scenarios for the absorbing material. We gratefully ackowledge the financial support of NASA grant: GO1-2112A

A Hubble Space Telescope Survey of Intrinsic Absorption in Nearby AGN

NASA Astrophysics Data System (ADS)

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 < 0.15 as a continuation of the Dunn et al. (2007, 2008) and Crenshaw et al. (1999) studies of smaller samples. We identify approximately 90 AGN fit our redshift specifications in the Mikulski Archive for Space Telescopes (MAST) database with Cosmic Origin Spectrograph (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.

Exploring possible relations between optical variability time scales and broad emission line shapes in AGN

NASA Astrophysics Data System (ADS)

Bon, Edi; Jovanović, Predrag; Marziani, Paola; Bon, Nataša; Otašević, Aleksandar

2018-06-01

Here we investigate the connection of broad emission line shapes and continuum light curve variability time scales of type-1 Active Galactic Nuclei (AGN). We developed a new model to describe optical broad emission lines as an accretion disk model of a line profile with additional ring emission. We connect ring radii with orbital time scales derived from optical light curves, and using Kepler's third law, we calculate mass of central supermassive black hole (SMBH). The obtained results for central black hole masses are in a good agreement with other methods. This indicates that the variability time scales of AGN may not be stochastic, but rather connected to the orbital time scales which depend on the central SMBH mass.

The Effect of Ag and Ag+N Ion Implantation on Cell Attachment Properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Urkac, Emel Sokullu; Oztarhan, Ahmet; Gurhan, Ismet Deliloglu

2009-03-10

Implanted biomedical prosthetic devices are intended to perform safely, reliably and effectively in the human body thus the materials used for orthopedic devices should have good biocompatibility. Ultra High Molecular Weight Poly Ethylene (UHMWPE) has been commonly used for total hip joint replacement because of its very good properties. In this work, UHMWPE samples were Ag and Ag+N ion implanted by using the Metal-Vapor Vacuum Arc (MEVVA) ion implantation technique. Samples were implanted with a fluency of 1017 ion/cm2 and extraction voltage of 30 kV. Rutherford Backscattering Spectrometry (RBS) was used for surface studies. RBS showed the presence of Agmore » and N on the surface. Cell attachment properties investigated with model cell lines (L929 mouse fibroblasts) to demonstrate that the effect of Ag and Ag+N ion implantation can favorably influence the surface of UHMWPE for biomedical applications. Scanning electron microscopy (SEM) was used to demonstrate the cell attachment on the surface. Study has shown that Ag+N ion implantation represents more effective cell attachment properties on the UHMWPE surfaces.« less

The first 62 AGN observed with SDSS-IV MaNGA - II: resolved stellar populations

NASA Astrophysics Data System (ADS)

Mallmann, Nícolas Dullius; Riffel, Rogério; Storchi-Bergmann, Thaisa; Barboza Rembold, Sandro; Riffel, Rogemar A.; Schimoia, Jaderson; da Costa, Luiz Nicolaci; Ávila-Reese, Vladimir; Sanchez, Sebastian F.; Machado, Alice D.; Cirolini, Rafael; Ilha, Gabriele S.; do Nascimento, Janaína C.

2018-05-01

We present spatially resolved stellar population age maps, average radial profiles and gradients for the first 62 Active Galactic Nuclei (AGN) observed with SDSS-IV MaNGA to study the effects of the active nuclei on the star formation history of the host galaxies. These results, derived using the STARLIGHT code, are compared with a control sample of non-active galaxies matching the properties of the AGN hosts. We find that the fraction of young stellar populations (SP) in high-luminosity AGN is higher in the inner (R≤0.5 Re) regions when compared with the control sample; low-luminosity AGN, on the other hand, present very similar fractions of young stars to the control sample hosts for the entire studied range (1 Re). The fraction of intermediate age SP of the AGN hosts increases outwards, with a clear enhancement when compared with the control sample. The inner region of the galaxies (AGN and control galaxies) presents a dominant old SP, whose fraction decreases outwards. We also compare our results (differences between AGN and control galaxies) for the early and late-type hosts and find no significant differences. In summary, our results suggest that the most luminous AGN seems to have been triggered by a recent supply of gas that has also triggered recent star formation (t ≤ 40 Myrs) in the central region.

Dynamically important magnetic fields near supermassive black holes in radio-loud AGN

NASA Astrophysics Data System (ADS)

Savolainen, Tuomas; Zamaninasab, Mohammad; Clausen-Brown, Eric; Tchekhovskoy, Alexander

The powerful radio jets ejected from the vicinity of accreting supermassive black holes in active galactic nuclei are thought to be formed by magnetic forces. However, there is little observational evidence of the actual strength of the magnetic fields in the jet-launching region, and in the accretion disks, of AGN. We have collected from the literature jet magnetic field estimates determined by very long baseline interferometry observations of the opacity-driven core-shift effect for 76 blazars and radio galaxies. We show that the jet magnetic flux of these radio-loud AGN tightly correlates with their accretion disk luminosity -- over seven orders of magnitude in accretion power. Moreover, the estimated magnetic flux threading the black hole quantitatively agrees with the saturation value expected in the magnetically arrested disk scenario. This implies that black holes in many, if not most, of the radio-loud AGN are surrounded by accretion disks that have dynamically important magnetic fields. Such disks behave very differently from the standard model disks with sub-equipartition magnetic fields, which may have important consequences for attempts to interpret disk spectral energy distributions or signatures of the possible black hole shadow in mm-VLBI images.

EDDINGTON RATIO DISTRIBUTION OF X-RAY-SELECTED BROAD-LINE AGNs AT 1.0 < z < 2.2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suh, Hyewon; Hasinger, Günther; Steinhardt, Charles

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 ofmore » 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.« less

A model for the repeating FRB 121102 in the AGN scenario

NASA Astrophysics Data System (ADS)

Vieyro, F. L.; Romero, G. E.; Bosch-Ramon, V.; Marcote, B.; del Valle, M. V.

2017-06-01

Context. Fast radio bursts (FRBs) are transient sources of unknown origin. Recent radio and optical observations have provided strong evidence for an extragalactic origin of the phenomenon and the precise localization of the repeating FRB 121102. Observations using the Karl G. Jansky Very Large Array (VLA) and very-long-baseline interferometry (VLBI) have revealed the existence of a continuum non-thermal radio source consistent with the location of the bursts in a dwarf galaxy. All these new data rule out several models that were previously proposed, and impose stringent constraints to new models. Aims: We aim to model FRB 121102 in light of the new observational results in the active galactic nucleus (AGN) scenario. Methods: We propose a model for repeating FRBs in which a non-steady relativistic e±-beam, accelerated by an impulsive magnetohydrodynamic driven mechanism, interacts with a cloud at the centre of a star-forming dwarf galaxy. The interaction generates regions of high electrostatic field called cavitons in the plasma cloud. Turbulence is also produced in the beam. These processes, plus particle isotropization, the interaction scale, and light retardation effects, provide the necessary ingredients for short-lived, bright coherent radiation bursts. Results: The mechanism studied in this work explains the general properties of FRB 121102, and may also be applied to other repetitive FRBs. Conclusions: Coherent emission from electrons and positrons accelerated in cavitons provides a plausible explanation of FRBs.

Comparison between geodetic and oceanographic approaches to estimate mean dynamic topography for vertical datum unification: evaluation at Australian tide gauges

NASA Astrophysics Data System (ADS)

Filmer, M. S.; Hughes, C. W.; Woodworth, P. L.; Featherstone, W. E.; Bingham, R. J.

2018-04-01

The direct method of vertical datum unification requires estimates of the ocean's mean dynamic topography (MDT) at tide gauges, which can be sourced from either geodetic or oceanographic approaches. To assess the suitability of different types of MDT for this purpose, we evaluate 13 physics-based numerical ocean models and six MDTs computed from observed geodetic and/or ocean data at 32 tide gauges around the Australian coast. We focus on the viability of numerical ocean models for vertical datum unification, classifying the 13 ocean models used as either independent (do not contain assimilated geodetic data) or non-independent (do contain assimilated geodetic data). We find that the independent and non-independent ocean models deliver similar results. Maximum differences among ocean models and geodetic MDTs reach >150 mm at several Australian tide gauges and are considered anomalous at the 99% confidence level. These differences appear to be of geodetic origin, but without additional independent information, or formal error estimates for each model, some of these errors remain inseparable. Our results imply that some ocean models have standard deviations of differences with other MDTs (using geodetic and/or ocean observations) at Australian tide gauges, and with levelling between some Australian tide gauges, of ˜ ± 50 mm . This indicates that they should be considered as an alternative to geodetic MDTs for the direct unification of vertical datums. They can also be used as diagnostics for errors in geodetic MDT in coastal zones, but the inseparability problem remains, where the error cannot be discriminated between the geoid model or altimeter-derived mean sea surface.

An Axisymmetric Hydrodynamical Model for the Torus Wind in AGN. 2; X-ray Excited Funnel Flow

NASA Technical Reports Server (NTRS)

Dorodnitsyn, A.; Kallman, T.; Proga, D.

2008-01-01

We have calculated a series of models of outflows from the obscuring torus in active galactic nuclei (AGN). Our modeling assumes that the inner face of a rotationally supported torus is illuminated and heated by the intense X-rays from the inner accretion disk and black hole. As a result of such heating a strong biconical outflow is observed in our simulations. We calculate 3-dimensional hydrodynamical models, assuming axial symmetry, and including the effects of X-ray heating, ionization, and radiation pressure. We discuss the behavior of a large family of these models, their velocity fields, mass fluxes and temperature, as functions of the torus properties and X-ray flux. Synthetic warm absorber spectra are calculated, assuming pure absorption, for sample models at various inclination angles and observing times. We show that these models have mass fluxes and flow speeds which are comparable to those which have been inferred from observations of Seyfert 1 warm absorbers, and that they can produce rich absorption line spectra.

The space density of Compton-thick AGN at z ≈ 0.8 in the zCOSMOS-Bright Survey

NASA Astrophysics Data System (ADS)

Vignali, C.; Mignoli, M.; Gilli, R.; Comastri, A.; Iwasawa, K.; Zamorani, G.; Mainieri, V.; Bongiorno, A.

2014-11-01

Context. The obscured accretion phase in black hole growth is a crucial ingredient in many models linking the active galactic nuclei (AGN) activity with the evolution of their host galaxy. At present, a complete census of obscured AGN is still missing, although several attempts in this direction have been carried out recently, mostly in the hard X-rays and at mid-infrared wavelengths. Aims: The purpose of this work is to assess whether the [Ne v] emission line at 3426 Å can reliably pick up obscured AGN up to z ≈ 1 by assuming that it is a reliable proxy of the intrinsic AGN luminosity and using moderately deep X-ray data to characterize the amount of obscuration. Methods: A sample of 69 narrow-line (Type 2) AGN at z ≈ 0.65-1.20 were selected from the 20k-zCOSMOS Bright galaxy sample on the basis of the presence of the [Ne v]3426 Å emission. The X-ray properties of these galaxies were then derived using the Chandra-COSMOS coverage of the field; the X-ray-to-[Ne v] flux ratio, coupled with X-ray spectral and stacking analyses, was then used to infer whether Compton-thin or Compton-thick absorption is present in these sources. Then the [Ne v] luminosity function was computed to estimate the space density of Compton-thick AGN at z ≈ 0.8. Results: Twenty-three sources were detected by Chandra, and their properties are consistent with moderate obscuration (on average, ≈a few × 1022 cm-2). The X-ray properties of the remaining 46 X-ray undetected Type 2 AGN (among which we expect to find the most heavily obscured objects) were derived using X-ray stacking analysis. Current data, supported by Monte Carlo simulations, indicate that a fraction as high as ≈40% of the present sample is likely to be Compton thick. The space density of Compton-thick AGN with logL2-10 keV> 43.5 at z = 0.83 is ΦThick = (9.1 ± 2.1) × 10-6 Mpc-3, in good agreement with both X-ray background model expectations and the previously measured space density for objects in a similar

AGN feedback through UFO and galaxy-wide winds in the early Universe

NASA Astrophysics Data System (ADS)

Feruglio, C.; Piconcelli, E.; Bischetti, M.; Zappacosta, L.; Fiore, F.

2017-10-01

AGN feedback through massive molecular winds is today routinely observed in local AGN host galaxies, but not as such in the early universe. I will present the first evidence for a massive, AGN-driven molecular wind in the z 4 QSO APM08279, which also hosts the most well studied and persistent nuclear semi-raltivistic wind (UFO). This observation directly probes the expansion mechanism of a nuclear wind into the ISM on galaxy wide scales, that so far was constrained by a couple of other objects only (Feruglio et al. 2015, Tombesi et al. 2015). This result also opens the path toward the exploration of molecular AGN-driven winds at early epochs, close after the end of the Epoch of Reionisation (EoR).

Quenching histories of galaxies and the role of AGN feedback

NASA Astrophysics Data System (ADS)

Smethurst, Rebecca Jane; Lintott, Chris; Simmons, Brooke; Galaxy Zoo Team

2016-01-01

Two open issues in modern astrophysics are: (i) how do galaxies fully quench their star formation and (ii) how is this affected - or not - by AGN feedback? I present the results of a new Bayesian-MCMC analysis of the star formation histories of over 126,000 galaxies across the colour magnitude diagram showing that diverse quenching mechanisms are instrumental in the formation of the present day red sequence. Using classifications from Galaxy Zoo we show that the rate at which quenching can occur is morphologically dependent in each of the blue cloud, green valley and red sequence. We discuss the nature of these possible quenching mechanisms, considering the influence of secular evolution, galaxy interactions and mergers, both with and without black hole activity. We focus particularly on the relationship between these quenched star formation histories and the presence of an AGN by using this new Bayesian method to show a population of type 2 AGN host galaxies have recently (within 2 Gyr) undergone a rapid (τ < 1 Gyr) drop in their star formation rate. With this result we therefore present the first statistically supported observational evidence that AGN feedback is an important mechanism for the cessation of star formation in this population of galaxies. The diversity of this new method also highlights that such rapid quenching histories cannot account fully for all the quenching across the current AGN host population. We demonstrate that slower (τ > 2 Gyr) quenching rates dominate for high stellar mass (log10[M*/M⊙] > 10.75) hosts of AGN with both early- and late-type morphology. We discuss how these results show that both merger-driven and non-merger processes are contributing to the co-evolution of galaxies and supermassive black holes across the entirety of the colour magnitude diagram.

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

NASA Astrophysics Data System (ADS)

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.

Testing warm Comptonization models for the origin of the soft X-ray excess in AGNs

NASA Astrophysics Data System (ADS)

Petrucci, P.-O.; Ursini, F.; De Rosa, A.; Bianchi, S.; Cappi, M.; Matt, G.; Dadina, M.; Malzac, J.

2018-03-01

The X-ray spectra of many active galactic nuclei (AGNs) show a soft X-ray excess below 1-2 keV on top of the extrapolated high-energy power law. The origin of this component is uncertain. It could be a signature of relativistically blurred, ionized reflection or the high-energy tail of thermal Comptonization in a warm (kT 1 keV), optically thick (τ ≃ 10-20) corona producing the optical/UV to soft X-ray emission. The purpose of the present paper is to test the warm corona model on a statistically significant sample of unabsorbed, radio-quiet AGNs with XMM-Newton archival data, providing simultaneous optical/UV and X-ray coverage. The sample has 22 objects and 100 observations. We use two thermal Comptonization components to fit the broadband spectra, one for the warm corona emission and one for the high-energy continuum. In the optical/UV, we also include the reddening, the small blue bump, and the Galactic extinction. In the X-rays, we include a warm absorber and a neutral reflection. The model gives a good fit (reduced χ2 < 1.5) to more than 90% of the sample. We find the temperature of the warm corona to be uniformly distributed in the 0.1-1 keV range, while the optical depth is in the range 10-40. These values are consistent with a warm corona covering a large fraction of a quasi-passive accretion disk, i.e., that mostly reprocesses the warm corona emission. The disk intrinsic emission represents no more than 20% of the disk total emission. According to this interpretation, most of the accretion power would be released in the upper layers of the accretion flow.

What Quasars Really Look Like: Unification of the Emission and Absorption Line Regions

NASA Technical Reports Server (NTRS)

Elvis, Martin

2000-01-01

We propose a simple unifying structure for the inner regions of quasars and AGN. This empirically derived model links together the broad absorption line (BALS), the narrow UV/X-ray ionized absorbers, the BELR, and the 5 Compton scattering/fluorescing regions into a single structure. The model also suggests an alternative origin for the large-scale bi-conical outflows. Some other potential implications of this structure are discussed.

Circumnuclear Star Formation and AGN Activity: Clues from Surface Brightness Radial Profile of PAHs and [{\\rm{S}}\\,{\\rm{IV}}

NASA Astrophysics Data System (ADS)

Esparza-Arredondo, Donaji; González-Martín, Omaira; Dultzin, Deborah; Alonso-Herrero, Almudena; Ramos Almeida, Cristina; Díaz-Santos, Tanio; García-Bernete, Ismael; Martinez-Paredes, Mariela; Rodríguez-Espinosa, Jose Miguel

2018-06-01

We studied the circumnuclear mid-IR emission in a sample of 19 local active galactic nuclei (AGNs) with high spatial resolution spectra using T-ReCS (Gemini) and CanariCam (GTC), together with Spitzer/IRS observations. We measured the flux and the equivalent width for the 11.3 μm PAH feature and the [S IV] line emission as a function of galactocentric distance. This allowed us to study the star formation (SF) at subkiloparsec scales from the nucleus for a large sample of nearby AGNs. The [S IV] line emission could be tracing the AGN radiation field within a few thousand times the sublimation radius (R sub), but it often peaks at distances greater than 1000 R sub. One possibility is that the SF is contributing to the [S IV] total flux. We found an 11.3 μm PAH emission deficit within the inner few tens of parsecs from the AGN. This deficit might be due to the destruction of the molecules responsible for this feature or the lack of SF at these distances. We found a sensible agreement in the expected shift of the relation of the AGN bolometric luminosity and the SF rate. This indicates that numerical models attributing the link between AGN activity and host galaxy growth to mergers are in agreement with our data, for most inner galaxy parts.

Principles of the Unification of Our Agency

ERIC Educational Resources Information Center

Roth, Klas

2011-01-01

Do we need principles of the unification of our agency, our mode of acting? Immanuel Kant and Christine Korsgaard argue that the reflective structure of our mind forces us to have some conception of ourselves, others and the world--including our agency--and that it is through will and reason, and in particular principles of our agency, that we…

A comprehensive classification of galaxies in the Sloan Digital Sky Survey: how to tell true from fake AGN?

NASA Astrophysics Data System (ADS)

Cid Fernandes, R.; Stasińska, G.; Mateus, A.; Vale Asari, N.

2011-05-01

We use the WHα versus [N II]/Hα (WHAN) diagram introduced by us in previous work to provide a comprehensive emission-line classification of Sloan Digital Sky Survey galaxies. This classification is able to cope with the large population of weak line galaxies that do not appear in traditional diagrams due to a lack of some of the diagnostic lines. A further advantage of the WHAN diagram is to allow the differentiation between two very distinct classes that overlap in the low-ionization nuclear emission-line region (LINER) region of traditional diagnostic diagrams. These are galaxies hosting a weakly active galactic nucleus (wAGN) and 'retired galaxies' (RGs), i.e. galaxies that have stopped forming stars and are ionized by their hot low-mass evolved stars. A useful criterion to distinguish true from fake AGN (i.e. the RGs) is the value of ξ, which measures the ratio of the extinction-corrected Hα luminosity with respect to the Hα luminosity expected from photoionization by stellar populations older than 108 yr. We find that ξ follows a markedly bimodal distribution, with a ξ≫ 1 population composed by systems undergoing star formation and/or nuclear activity, and a peak at ξ˜ 1 corresponding to the prediction of the RG model. We base our classification scheme not on ξ but on a more readily available and model-independent quantity which provides an excellent observational proxy for ξ: the equivalent width of Hα. Based on the bimodal distribution of WHα, we set the practical division between wAGN and RGs at WHα= 3 Å. Five classes of galaxies are identified within the WHAN diagram: (i) pure star-forming galaxies: ? and WHα > 3 Å; (ii) strong AGN (i.e. Seyferts): ? and WHα > 6 Å; (iii) weak AGN: ? and WHα between 3 and 6 Å; (iv) RGs (i.e. fake AGN): WHα < 3 Å; (v) passive galaxies (actually, lineless galaxies): WHα and W[N II] < 0.5 Å. A comparative analysis of star formation histories and of other physical and observational properties in these

Graph Unification and Tangram Hypothesis Explanation Representation (GATHER) and System and Component Modeling Framework (SCMF)

DTIC Science & Technology

2008-08-01

services, DIDS and DMS, are deployable on the TanGrid system and are accessible via two APIs, a Java client and a servlet based interface. Additionally...but required the user to instantiate an IGraph object with several Java Maps containing the nodes, node attributes, edge types, and the connections...restrictions imposed by the bulk ingest process. Finally, once the bulk ingest process was available in the GraphUnification Java Archives (JAR), DC was

Morphology of AGN in the Central Kiloparsec

NASA Astrophysics Data System (ADS)

Martini, Paul

Hubble Space Telescope observations of the central kiloparsec of AGN have revealed a wealth of structure, particularly nuclear bars and spirals, that are distinct from analogous features in the disks of spiral galaxies. WFPC2 and NICMOS images of a large sample of AGN observed at high spatial resolution make it possible to quantify the frequency and detailed properties of these structures. Nearly all AGN have nuclear spiral dust lanes in the central kiloparsec, while only a small minority contain nuclear bars. If these nuclear dust spirals trace shocks in the circumnuclear, gaseous disks, they may dissipate sufficient angular momentum to fuel the active nucleus. I would like to thank my collaborators in this project---Rick Pogge, John Mulchaey, and Mike Regan---for allowing me to present this work in advance of publication, as well as Johan Knapen for organizing such an interesting meeting. Support for this work was provided by NASA through grant numbers GO-7867 and GO-8597 from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

Understanding AGNs in the Local Universe through Optical Reverberation Mapping

NASA Astrophysics Data System (ADS)

Pei, Liuyi

2016-01-01

I present the results of observational projects aimed at measuring the mass of the black hole at the center of active galactic nuclei (AGNs) and understanding the structure and kinematics of the broad-line emitting gas within the black hole's sphere of influence.The first project aims to measure the black hole mass in the Kepler-field AGN KA1858. We obtained simultaneous spectroscopic data from the Lick Observatory 3-m telescope using the Kast Double Spectrograph and photometry data from five ground-based telescopes, and used reverberation mapping (RM) techniques to measure the emission-line light curves' lags relative to continuum variations. We obtained lags for H-beta, H-gamma, H-delta, and He II, and obtained the first black hole mass measurement for this object. Our results will serve as a reference point for future studies on relations between black hole mass and continuum variability characteristics using Kepler AGN light curves.The second project, in collaboration with the AGN STORM team, aims to understand the structure and dynamics of the broad line region (BLR) in NGC 5548 in both UV and optical wavelengths. To supplement 6 months of HST UV observations, we obtained simultaneous optical spectroscopic data from six ground-based observatories. We obtained emission-line lags for the optical H-beta and He II lines as well as velocity-resolved lag measurements for H-beta. We also compared the velocity-resolved lags for H-beta to the UV emission lines C IV and Ly-alpha and found similar lag profiles for all three lines.Finally, I will discuss my contributions to two other collaborations in AGN RM. A key component in RM is monitoring continuum variability, which is often done through ground-based photometry. I will present a pipeline that performs aperture photometry on any number of images of an AGN with WCS coordinates and immediately produces relative light curves. This pipeline enables quick looks of AGN variability in real time and has been used in the

THE HOST GALAXY PROPERTIES OF VARIABILITY SELECTED AGN IN THE PAN-STARRS1 MEDIUM DEEP SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heinis, S.; Gezari, S.; Kumar, S.

2016-07-20

We study the properties of 975 active galactic nuclei (AGNs) selected by variability in the Pan-STARRS1 Medium deep Survey. Using complementary multi-wavelength data from the ultraviolet to the far-infrared, we use spectral energy distribution fitting to determine the AGN and host properties at z < 1 and compare to a well-matched control sample. We confirm the trend previously observed: that the variability amplitude decreases with AGN luminosity, but we also observe that the slope of this relation steepens with wavelength, resulting in a “redder when brighter” trend at low luminosities. Our results show that AGNs are hosted by more massivemore » hosts than control sample galaxies, while the rest frame dust-corrected NUV r color distribution of AGN hosts is similar to control galaxies. We find a positive correlation between the AGN luminosity and star formation rate (SFR), independent of redshift. AGN hosts populate the entire range of SFRs within and outside of the Main Sequence of star-forming galaxies. Comparing the distribution of AGN hosts and control galaxies, we show that AGN hosts are less likely to be hosted by quiescent galaxies and more likely to be hosted by Main Sequence or starburst galaxies.« less

The Relation between Luminous AGNs and Star Formation in Their Host Galaxies

NASA Astrophysics Data System (ADS)

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.

The Effects of Accretion Disk Geometry on AGN Reflection Spectra

NASA Astrophysics Data System (ADS)

Taylor, Corbin James; Reynolds, Christopher S.

2017-08-01

Despite being the gravitational engines that power galactic-scale winds and mega parsec-scale jets in active galaxies, black holes are remarkably simple objects, typically being fully described by their angular momenta (spin) and masses. The modelling of AGN X-ray reflection spectra has proven fruitful in estimating the spin of AGN, as well as giving insight into their accretion histories and the properties of plasmas in the strong gravity regime. However, current models make simplifying assumptions about the geometry of the reflecting material in the accretion disk and the irradiating X-ray corona, approximating the disk as an optically thick, infinitely thin disk of material in the orbital plane. We present results from the new relativistic raytracing suite, Fenrir, that explore the effects that disk thickness may have on the reflection spectrum and the accompanying reverberation signatures. Approximating the accretion disk as an optically thick, geometrically thin, radiation pressure dominated disk (Shakura & Sunyaev 1973), one finds that the disk geometry is non-negligible in many cases, with significant changes in the broad Fe K line profile. Finally, we explore the systematic errors inherent in approximating the disk as being infinitely thin when modeling reflection spectrum, potentially biasing determinations of black hole and corona properties.

Unveiling the physics of AGN through X-ray variability

NASA Astrophysics Data System (ADS)

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.

Probing the gas fuelling and outflows in nearby AGN with ALMA

NASA Astrophysics Data System (ADS)

Audibert, Anelise; Combes, Françoise; García-Burillo, Santiago; Salomé, Philippe

2017-12-01

Feeding and feedback in AGN play a very important role to gain a proper understanding of galaxy formation and evolution. The interaction between activity mechanisms in the nucleus and its influence in the host galaxy are related to the physical processes involved in feedback and the gas fuelling of the black hole. The discovery of many massive molecular outflows in the last few years have been promoting the idea that winds may be major actors in sweeping the gas out of galaxies. Also, the widely observed winds from the central regions of AGN are promising candidates to explain the scaling relations (e.g. the black hole-bulge mass relation, BH accretion rate tracking the star formation history) under the AGN feedback scenario. Out goal is to probe these phenomena through the kinematic and morphology of the gas inside the central kpc in nearby AGN. This has recently been possible due to the unprecedented ALMA spatial resolution and sensitivity. We present results on NGC7213 and NGC1808, the latter is part of a new ALMA follow-up of the NuGa project, a previous high-resolution (0.5-1”) CO survey of low luminosity AGN performed with the IRAM PdBI.

Intermediate-line Emission in AGNs: The Effect of Prescription of the Gas Density

NASA Astrophysics Data System (ADS)

Adhikari, T. P.; Hryniewicz, K.; Różańska, A.; Czerny, B.; Ferland, G. J.

2018-03-01

The requirement of an intermediate-line component in the recently observed spectra of several active galactic nuclei (AGNs) points to the possible existence of a physically separate region between the broad-line region (BLR) and narrow-line region (NLR). In this paper we explore the emission from the intermediate-line region (ILR) by using photoionization simulations of the gas clouds distributed radially from the center of the AGN. The gas clouds span distances typical for the BLR, ILR, and NLR, and the appearance of dust at the sublimation radius is fully taken into account in our model. The structure of a single cloud is calculated under the assumption of constant pressure. We show that the slope of the power-law radial profile of the cloud density does not affect the existence of the ILR in major types of AGNs. We found that the low-ionization iron line, Fe II, appears to be highly sensitive to the presence of dust and therefore becomes a potential tracer of dust content in line-emitting regions. We show that the use of a disk-like cloud density profile computed for the upper part of the atmosphere of the accretion disk reproduces the observed properties of the line emissivities. In particular, the distance of the Hβ line inferred from our model agrees with that obtained from reverberation mapping studies in the Sy1 galaxy NGC 5548.

77 FR 3787 - Notice of Submission of Proposed Information Collection to OMB; Family Unification Program (FUP)

Federal Register 2010, 2011, 2012, 2013, 2014

2012-01-25

... Proposed Information Collection to OMB; Family Unification Program (FUP) AGENCY: Office of the Chief... Paperwork Reduction Act. The Department is soliciting public comments on the subject proposal. Application for the Family Unification Program: Makes Housing Choice Vouchers available to eligible families to...

76 FR 11505 - Notice of Submission of Proposed Information Collection to OMB Family Unification Program (FUP)

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-02

... Proposed Information Collection to OMB Family Unification Program (FUP) AGENCY: Office of the Chief... Paperwork Reduction Act. The Department is soliciting public comments on the subject proposal. Application for the Family Unification Program: Makes Housing Choice Vouchers available to eligible families to...

Unification of quantum information theory

NASA Astrophysics Data System (ADS)

Abeyesinghe, Anura

We present the unification of many previously disparate results in noisy quantum Shannon theory and the unification of all of noiseless quantum Shannon theory. More specifically we deal here with bipartite, unidirectional, and memoryless quantum Shannon theory. We find all the optimal protocols and quantify the relationship between the resources used, both for the one-shot and for the ensemble case, for what is arguably the most fundamental task in quantum information theory: sharing entangled states between a sender and a receiver. We find that all of these protocols are derived from our one-shot superdense coding protocol and relate nicely to each other. We then move on to noisy quantum information theory and give a simple, direct proof of the "mother" protocol, or rather her generalization to the Fully Quantum Slepian-Wolf protocol (FQSW). FQSW simultaneously accomplishes two goals: quantum communication-assisted entanglement distillation, and state transfer from the sender to the receiver. As a result, in addition to her other "children," the mother protocol generates the state merging primitive of Horodecki, Oppenheim, and Winter as well as a new class of distributed compression protocols for correlated quantum sources, which are optimal for sources described by separable density operators. Moreover, the mother protocol described here is easily transformed into the so-called "father" protocol, demonstrating that the division of single-sender/single-receiver protocols into two families was unnecessary: all protocols in the family are children of the mother.

Distinct signals of the gauge-Higgs unification in e+e- collider experiments

NASA Astrophysics Data System (ADS)

Funatsu, Shuichiro; Hatanaka, Hisaki; Hosotani, Yutaka; Orikasa, Yuta

2017-12-01

Effects of Kaluza-Klein excited neutral vector bosons (Z‧ bosons) in the gauge-Higgs unification on e+e- → q bar q ,ℓ+ℓ- cross sections are studied, particularly in future e+e- collider experiments with polarized beams. Significant deviations in the energy and polarization dependence in σ (μ+μ-), the lepton forward-backward asymmetry, Rb (μ) ≡ σ (b bar b) / σ (μ+μ-) and the left-right asymmetry from the standard model are predicted.

THE COMMON MARKET AND EUROPEAN UNIFICATION,

DTIC Science & Technology

A study of the Common Market ; its past problems, current difficulties, and future possibilities are presented. The study consists of seven sections...each of which may be read independently: (1) an introduction to the Common Market ; (2) the Common Market and internal trade; (3) external economic...European Economic Community agriculture; and (7) the Common Market and European political unification. Statistical tables showing import and export data of the Common Market countries are appended. (Author)

Deductive Synthesis of the Unification Algorithm,

DTIC Science & Technology

1981-06-01

DEDUCTIVE SYNTHESIS OF THE I - UNIFICATION ALGORITHM Zohar Manna Richard Waldinger I F? Computer Science Department Artificial Intelligence Center...theorem proving," Artificial Intelligence Journal, Vol. 9, No. 1, pp. 1-35. Boyer, R. S. and J S. Moore [Jan. 19751, "Proving theorems about LISP...d’Intelligence Artificielle , U.E.R. de Luminy, Universit6 d’ Aix-Marseille II. Green, C. C. [May 1969], "Application of theorem proving to problem

LHC-scale left-right symmetry and unification

NASA Astrophysics Data System (ADS)

Arbeláez, Carolina; Romão, Jorge C.; Hirsch, Martin; Malinský, Michal

2014-02-01

We construct a comprehensive list of nonsupersymmetric standard model extensions with a low-scale left-right (LR)-symmetric intermediate stage that may be obtained as simple low-energy effective theories within a class of renormalizable SO(10) grand unified theories. Unlike the traditional "minimal" LR models many of our example settings support a perfect gauge coupling unification even if the LR scale is in the LHC domain at a price of only (a few copies of) one or two types of extra fields pulled down to the TeV-scale ballpark. We discuss the main aspects of a potentially realistic model building conforming the basic constraints from the quark and lepton sector flavor structure, proton decay limits, etc. We pay special attention to the theoretical uncertainties related to the limited information about the underlying unified framework in the bottom-up approach, in particular, to their role in the possible extraction of the LR-breaking scale. We observe a general tendency for the models without new colored states in the TeV domain to be on the verge of incompatibility with the proton stability constraints.

How to model AGN feedback in cosmological simulations?

NASA Astrophysics Data System (ADS)

Sijacki, Debora

2015-08-01

Hydrodynamical cosmological simulations are one of the most powerful tools to study the formation and evolution of galaxies in the fully non-linear regime. Despite several recent successes in simulating Milky Way look-alikes, self-consistent, ab-initio models are still a long way off. In this talk I will review numerical and physical uncertainties plaguing current state-of-the-art cosmological simulations of galaxy formation. I will then discuss which feedback mechanisms are needed to reproduce realistic stellar masses and galaxy morphologies in the present day Universe and argue that the black hole feedback is necessary for the quenching of massive galaxies. I will then demonstrate how black hole - host galaxy scaling relations depend on galaxy morphology and colour, highlighting the implications for the co-evolutionary picture between galaxies and their central black holes. In the second part of the talk I will present a novel method that permits to resolve gas flows around black holes all the way from large cosmological scales to the Bondi radii of black holes themselves. I will demonstrate that with this new numerical technique it is possible to estimate much more accurately gas properties in the vicinity of black holes than has been feasible before in galaxy and cosmological simulations, allowing to track reliably gas angular momentum transport from Mpc to pc scales. Finally, I will also discuss if AGN-driven outflows are more likely to be energy- or momentum-driven and what implications this has for the redshift evolution of black hole - host galaxy scaling relations.

Merger-driven fueling of active galactic nuclei: Six dual and of AGNs discovered with Chandra and Hubble Space Telescope observations

DOE PAGES

Comerford, Julia M.; Pooley, David; Barrows, R. Scott; ...

2015-06-19

Dual active galactic nuclei (AGNs) and offset AGNs are kpc-scale separation supermassive black holes pairs created during galaxy mergers, where both or one of the black holes are AGNs, respectively. These dual and offset AGNs are valuable probes of the link between mergers and AGNs but are challenging to identify. Here we present Chandra/ACIS observations of 12 optically selected dual AGN candidates atmore » $$z\\lt 0.34$$, where we use the X-rays to identify AGNs. We also present Hubble Space Telescope/Wide Field Camera 3 observations of 10 of these candidates, which reveal any stellar bulges accompanying the AGNs. We discover a dual AGN system with separation $${\\rm \\Delta }x=2.2$$ kpc, where the two stellar bulges have coincident [O iii] λ5007 and X-ray sources. This system is an extremely minor merger (460:1) that may include a dwarf galaxy hosting an intermediate mass black hole. We also find six single AGNs, and five systems that are either dual or offset AGNs with separations $${\\rm \\Delta }x\\lt 10$$ kpc. Four of the six dual AGNs and dual/offset AGNs are in ongoing major mergers, and these AGNs are 10 times more luminous, on average, than the single AGNs in our sample. This hints that major mergers may preferentially trigger higher luminosity AGNs. Further, we find that confirmed dual AGNs have hard X-ray luminosities that are half of those of single AGNs at fixed [O III] λ5007 luminosity, on average. Lastly, this could be explained by high densities of gas funneled to galaxy centers during mergers, and emphasizes the need for deeper X-ray observations of dual AGN candidates.« less

VizieR Online Data Catalog: Intrinsic far-IR SED of luminous AGNs (Lyu+, 2017)

NASA Astrophysics Data System (ADS)

Lyu, J.; Rieke, G. H.

2018-01-01

The range of currently proposed active galactic nucleus (AGN) far-infrared templates results in uncertainties in retrieving host galaxy information from infrared observations and also undermines constraints on the outer part of the AGN torus. We discuss how to test and reconcile these templates. Physically, the fraction of the intrinsic AGN IR-processed luminosity compared with that from the central engine should be consistent with the dust-covering factor. In addition, besides reproducing the composite spectral energy distributions (SEDs) of quasars, a correct AGN IR template combined with an accurate library of star-forming galaxy templates should be able to reproduce the IR properties of the host galaxies, such as the luminosity-dependent SED shapes and aromatic feature strengths. We develop tests based on these expected behaviors and find that the shape of the AGN intrinsic far-IR emission drops off rapidly starting at ~20μm and can be matched by an Elvis+ (1994, J/ApJS/95/1)-like template with a minor modification. Despite the variations in the near- to mid-IR bands, AGNs in quasars and Seyfert galaxies have remarkably similar intrinsic far-IR SEDs at λ~20-100μm, suggesting a similar emission character of the outermost region of the circumnuclear torus. The variations of the intrinsic AGN IR SEDs among the type-1 quasar population can be explained by the changing relative strengths of four major dust components with similar characteristic temperatures, and there is evidence for compact AGN-heated dusty structures at sub-kiloparsec scales in the far-IR. (3 data files).

Height unification using GOCE

NASA Astrophysics Data System (ADS)

Rummel, R.

2012-12-01

With the gravity field and steady-state ocean circulation explorer (GOCE) (preferably combined with the gravity field and climate experiment (GRACE)) a new generation of geoid models will become available for use in height determination. These models will be globally consistent, accurate (<3 cm) and with a spatial resolution up to degree and order 200, when expressed in terms of a spherical harmonic expansion. GOCE is a mission of the European Space Agency (ESA). It is the first satellite equipped with a gravitational gradiometer, in the case of GOCE it measures the gradient components Vxx , Vyy, Vzzand Vxz. The GOCE gravitational sensor system comprises also a geodetic global positioning system (GPS)-receiver, three star sensors and ion-thrusters for drag compensation in flight direction. GOCE was launched in March 2009 and will fly till the end of 2013. Several gravity models have been derived from its data, their maximum degree is typically between 240 and 250. In summer 2012 a first re-processing of all level-1b data took place. One of the science objectives of GOCE is the unification of height systems. The existing height offsets among the datum zones can be determined by least-squares adjustment. This requires several precise geodetic reference points available in each height datum zone, physical heights from spirit levelling (plus gravimetry), the GOCE geoid and, in addition, short wavelength geoid refinement from terrestrial gravity anomalies. GOCE allows for important simplifications of the functional and stochastic part of the adjustment model. The future trend will be the direct determination of physical heights (orthometric as well as normal) from precise global navigation satellite system (GNSS)-positioning in combination with a next generation combined satellite-terrestrial high-resolution geoid model.

Unification of Forces: The Road to Jointness?

DTIC Science & Technology

1991-05-15

tend to resist large change--or innovation. Because organizations value "predictability, stability, and certainty," incremental change is the...preferred mode of behavior for organizations.29 Unification of the forces would be a large, rather than an incremental , change; thus, the services would...coordinating planning and bidgeting , providing unified direction, accounting and controlling weapons and equipment acquisition, eliminating duplication of

Mid-IR Properties of an Unbiased AGN Sample of the Local Universe. 1; Emission-Line Diagnostics

NASA Technical Reports Server (NTRS)

Weaver, K. A.; Melendez, M.; Muhotzky, R. F.; Kraemer, S.; Engle, K.; Malumuth. E.; Tueller, J.; Markwardt, C.; Berghea, C. T.; Dudik, R. P.;

AGN POPULATION IN HICKSON COMPACT GROUPS. I. DATA AND NUCLEAR ACTIVITY CLASSIFICATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

MartInez, M. A.; Del Olmo, A.; Perea, J.

2010-03-15

We have conducted a new spectroscopic survey to characterize the nature of nuclear activity in Hickson compact group (HCG) galaxies and establish its frequency. We have obtained new intermediate-resolution optical spectroscopy for 200 member galaxies and corrected for underlying stellar population contamination using galaxy templates. Spectra for 11 additional galaxies have been acquired from the ESO and 6dF public archives, and emission-line ratios have been taken from the literature for 59 more galaxies. Here we present the results of our classification of the nuclear activity for 270 member galaxies, which belong to a well-defined sample of 64 HCGs. We foundmore » a large fraction of galaxies, 63%, with emission lines. Using standard diagnostic diagrams, 45% of the emission-line galaxies were classified as pure active galactic nuclei (AGNs), 23% as Transition Objects (TOs), and 32% as star-forming nuclei (SFNs). In the HCGs, the AGN activity appears as the most frequent activity type. Adopting the interpretation that in TOs a low-luminosity AGN coexists with circumnuclear star formation, the fraction of galaxies with an AGN could rise to 42% of the whole sample. The low frequency (20%) of SFNs confirms that there is no star formation enhancement in HCGs. After extinction correction, we found a median AGN H{alpha} luminosity of 7.1 x 10{sup 39} erg s{sup -1}, which implies that AGNs in HCG have a characteristically low luminosity. This result added to the fact that there is an almost complete absence of broad-line AGNs in compact groups (CGs) as found by MartInez et al. and corroborated in this study for HCGs, is consistent with very few gas left in these galaxies. In general, therefore, what may characterize the level of activity in CGs is a severe deficiency of gas.« less

The Swift AGN and Cluster Survey

NASA Astrophysics Data System (ADS)

Danae Griffin, Rhiannon; Dai, Xinyu; Kochanek, Christopher S.; Bregman, Joel N.; Nugent, Jenna

2016-01-01

The Swift active galactic nucleus (AGN) and Cluster Survey (SACS) uses 125 deg^2 of Swift X-ray Telescope serendipitous fields with variable depths surrounding X-ray bursts to provide a medium depth (4 × 10^-15 erg cm^-2 s^-1) and area survey filling the gap between deep, narrow Chandra/XMM-Newton surveys and wide, shallow ROSAT surveys. Here, we present the first two papers in a series of publications for SACS. In the first paper, we introduce our method and catalog of 22,563 point sources and 442 extended sources. We 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. The depth and areal coverage of SACS is well suited for galaxy cluster surveys outside the local universe, reaching z ˜ 1 for massive clusters. In the second paper, we use Sloan Digital Sky Survey (SDSS) DR8 data to study the 203 extended SACS sources that are located within the SDSS footprint. We search for galaxy over-densities in 3-D space using SDSS galaxies and their photometric redshifts near the Swift galaxy cluster candidates. We find 103 Swift clusters with a > 3σ over-density. The remaining targets are potentially located at higher redshifts and require deeper optical follow-up observations for confirmations as galaxy clusters. We present a series of cluster properties including the redshift, BCG magnitude, BCG-to-X-ray center offset, optical richness, X-ray luminosity and red sequences. 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 80% complete for z ≤ 0.4, consistent with the survey depth of SDSS. We also match our SDSS confirmed Swift clusters to existing cluster catalogs, and find 42, 2 and 1 matches in optical, X-ray and SZ catalogs, respectively, so the majority of these

SWIFT BAT Survey of AGN

NASA Technical Reports Server (NTRS)

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.

2MASS J00423991+3017515: An AGN On The Run?

NASA Astrophysics Data System (ADS)

Hogg, James

2016-10-01

We have discovered a peculiar AGN, 2MASS J00423991+3017515, in a local (z=0.14), disturbed galaxy whose optical spectrum has multiple broad lines that are consistently offset from the narrow line emission and host galaxy absorption by 1530 km/s. The morphology of the host galaxy and spectral properties thus suggest this AGN may be a recoiling supermassive black hole (SMBH). Gravitational-wave recoil kicks result from the coalescence of two SMBHs and have implications for the early growth of high-redshift quasars and SMBH-galaxy co-evolution. We propose high-resolution imaging in the NIR, optical, and UV with the WFC3 camera on Hubble and high-resolution X-ray imaging and spectral follow-ups with the ACIS camera on Chandra to determine if the source of the kinematically-offset broad line emission is also spatially offset from the nucleus of the host galaxy. We request 3 orbits with Hubble and 8 ksec with Chandra to conduct these follow-up observations. If a single, spatially offset AGN is detected, this source will be strongest candidate for a recoiling AGN candidate discovered to date, providing a new, indirect constraint on SMBH spin evolution and merger rates.

Star Formation and AGN Activity in Ultraluminous Infrared Galaxies at z > 1.15

NASA Astrophysics Data System (ADS)

Baldassare, Vivienne; Kartaltepe, J.

2012-01-01

We studied active galactic nucleus (AGN) activity and star formation in a sample of 52 luminous and ultraluminous infrared galaxies ((U)LIRGs) with 1.17 < z < 1.602 and LIR > 1011.5 Lsolar. ULIRGs get their extreme infrared luminosities from the heating of dust by star formation and/or AGN. Studies done in the local universe have revealed that all local ULIRGs are mergers (Sanders & Mirabel 1996), and have proposed evolutionary schemes in which early merger stages are dominated by starbursts, intermediate merger stages are dominated by starburst-AGN composite objects, and late merger stages are dominated by AGN (Yuan et al. 2010). They have also shown that most ULIRGs with LIR > 1012.4-12.5 Lsolar appear AGN-like (Tran et al. 2001). We used near infrared spectroscopy in order to determine whether these trends extend to high redshift, utilizing the [NII]/H-alpha and [OIII]/H-beta line ratios to plot our objects on a BPT diagram which classifies them as star forming, AGN, or composite. We find that many of the objects in our sample show evidence of mergers or interactions, and that all objects in our sample with LIR >1012.5 Lsolar are AGN or composite objects. Vivienne Baldassare was supported by the NOAO/KPNO Research Experiences for Undergraduates (REU) Program which is funded by the National Science Foundation Research Experiences for Undergraduates Program and the Department of Defense ASSURE program through Scientific Program Order No. 13 (AST-0754223) of the Cooperative Agreement No. AST-0132798 between the Association of Universities for Research in Astronomy (AURA) and the NSF.

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

NASA Technical Reports Server (NTRS)

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.

Evidence for ultrafast outflows in radio-quiet AGNs - III. Location and energetics

NASA Astrophysics Data System (ADS)

Tombesi, F.; Cappi, M.; Reeves, J. N.; Braito, V.

2012-05-01

Using the results of a previous X-ray photoionization modelling of blueshifted Fe K absorption lines on a sample of 42 local radio-quiet AGNs observed with XMM-Newton, in this Letter we estimate the location and energetics of the associated ultrafast outflows (UFOs). Due to significant uncertainties, we are essentially able to place only lower/upper limits. On average, their location is in the interval ˜0.0003-0.03 pc (˜ 102-104rs) from the central black hole, consistent with what is expected for accretion disc winds/outflows. The mass outflow rates are constrained between ˜0.01 and 1 M⊙ yr-1, corresponding to >rsim5-10 per cent of the accretion rates. The average lower/upper limits on the mechanical power are log? 42.6-44.6 erg s-1. However, the minimum possible value of the ratio between the mechanical power and bolometric luminosity is constrained to be comparable or higher than the minimum required by simulations of feedback induced by winds/outflows. Therefore, this work demonstrates that UFOs are indeed capable to provide a significant contribution to the AGN cosmological feedback, in agreement with theoretical expectations and the recent observation of interactions between AGN outflows and the interstellar medium in several Seyfert galaxies.

Germany Since Unification. Workshop Leader's Manual. An Introduction to Social Studies Instructional Resource Materials for Teaching about Germany Since Unification.

ERIC Educational Resources Information Center

Blankenship, Glen

This manual is designed to offer support for the instructional resources guides on "Germany since Unification." It provides the basis for a full-day inservice training session on the use of those materials. The format can be modified to meet the needs of leaders, audiences, and time frames. Using the materials developed by teachers and…

Host Galaxies Of Luminous Z ˜ 0.6 Quasars: Major Mergers Are Not Prevalent At The Highest Agn Luminosities

NASA Astrophysics Data System (ADS)

Villforth, Carolin; Hamilton, T.; Pawlik, M. M.; Hewlett, T.; Rowlands, K.; Herbst, H.; Shankar, F.; Fontana, A.; Hamann, F.; Koekemoer, A.; Pforr, J.; Trump, J.; Wuyts, S.

2017-06-01

Galaxy interactions are thought to be one of the main triggers of active galactic nuclei (AGN), especially at high luminosities, where the accreted gas mass during the AGN lifetime is substantial. Evidence for a connection between mergers and AGN, however, remains mixed. Possible triggering mechanisms remain particularly poorly understood for luminous AGN, which are thought to require triggering by major mergers, rather than secular processes. We analyse the host galaxies of a sample of 20 optically and X-ray selected luminous AGN (log(Lbol [erg s-1]) > 45) at z ˜ 0.6 using Hubble Space Telescope Wide Field Camera 3 data in the F160W/H band. 15/20 sources have resolved host galaxies. We create a control sample of mock AGN by matching the AGN host galaxies to a control sample of non-AGN galaxies. Visual signs of disturbances are found in about 25 per cent of sources in both the AGN hosts and control galaxies. Using both visual classification and quantitative morphology measures, we show that the levels of disturbance are not enhanced when compared to a matched control sample. We find no signs that major mergers play a dominant role in triggering AGN at high luminosities, suggesting that minor mergers and secular processes dominate AGN triggering up to the highest AGN luminosities. The upper limit on the enhanced fraction of major mergers is ≤20 per cent. While major mergers might increase the incidence of luminous AGN, they are not the prevalent triggering mechanism in the population of unobscured AGN.

Host galaxies of luminous z ˜ 0.6 quasars: major mergers are not prevalent at the highest AGN luminosities

NASA Astrophysics Data System (ADS)

Villforth, C.; Hamilton, T.; Pawlik, M. M.; Hewlett, T.; Rowlands, K.; Herbst, H.; Shankar, F.; Fontana, A.; Hamann, F.; Koekemoer, A.; Pforr, J.; Trump, J.; Wuyts, S.

2017-04-01

Galaxy interactions are thought to be one of the main triggers of active galactic nuclei (AGN), especially at high luminosities, where the accreted gas mass during the AGN lifetime is substantial. Evidence for a connection between mergers and AGN, however, remains mixed. Possible triggering mechanisms remain particularly poorly understood for luminous AGN, which are thought to require triggering by major mergers, rather than secular processes. We analyse the host galaxies of a sample of 20 optically and X-ray selected luminous AGN (log(Lbol [erg s-1]) > 45) at z ˜ 0.6 using Hubble Space Telescope Wide Field Camera 3 data in the F160W/H band. 15/20 sources have resolved host galaxies. We create a control sample of mock AGN by matching the AGN host galaxies to a control sample of non-AGN galaxies. Visual signs of disturbances are found in about 25 per cent of sources in both the AGN hosts and control galaxies. Using both visual classification and quantitative morphology measures, we show that the levels of disturbance are not enhanced when compared to a matched control sample. We find no signs that major mergers play a dominant role in triggering AGN at high luminosities, suggesting that minor mergers and secular processes dominate AGN triggering up to the highest AGN luminosities. The upper limit on the enhanced fraction of major mergers is ≤20 per cent. While major mergers might increase the incidence of luminous AGN, they are not the prevalent triggering mechanism in the population of unobscured AGN.

Review of Space VLBI RadioAstron studies of AGN

NASA Astrophysics Data System (ADS)

Gurvits, Leonid; Kovalev, Yuri

2016-07-01

Space VLBI offers an unrivalled resolution in studies of the AGN phenomena. Since 2011, the Russia-led SVLBI mission RadioAstron conducts observations at 92, 18, 6 and 1.3 cm with baselines an order of magnitude longer than the Earth diameter, therefore offering an order of magnitude "sharper" view at the brightest radio sources than achieved with Earth-based VLBI systems. In our presentation we will review the current status of the RadioAstron's scientific programme. Over the first 4.5 years of the in-orbit operations, the mission achieved successful VLBI detections of extragalactic continuum radio sources at all four observing bands. To date, detections on SVLBI baselines have been obtained for more than 150 AGN's at projected baselines up to 350 000 km (about 28 Earth diameters, ED). The highest resolution achieved is 14 microarcscends from 1.3 cm observations. RadioAstron is an international project; it conducts observations with up to 30 Earth-based radio telescopes located on different continents. We will review results of total intensity and polarisation imaging with extreme angular resolution of blazars and nearby active galaxies. We will also discuss typical and maximum brightness temperatures of blazar cores from the AGN Survey obtained with RadioAstron. Physical implications for the AGN jets formation, magnetic field and emission mechanism will be discussed on the basis of the results obtained to date.

On the Importance of Very Light Internally Subsonic AGN Jets in Radio-mode AGN Feedback

NASA Astrophysics Data System (ADS)

Guo, Fulai

2016-07-01

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 kiloparsec-scale interaction of AGN jets with the intracluster medium. Large-scale jet simulations often initiate light internally supersonic jets with density contrast 0.01 < η < 1. Here we argue for the first time for the importance of very light (η < 0.01) internally subsonic jets. We investigated the shapes of young X-ray cavities produced in a suite of hydrodynamic simulations, and found that bottom-wide cavities are always produced by internally subsonic jets, while internally supersonic jets inflate cylindrical, center-wide, or top-wide cavities. We found examples of real cavities with shapes analogous to those inflated in our simulations 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 resulted from light jets spread along the jet direction, while those produced by very light jets are significantly elongated along the perpendicular direction. The northwestern ghost cavity in Perseus is pancake shaped, providing tentative evidence for the existence of very light jets. Our simulations show that very light internally subsonic jets decelerate faster and rise much slower in the intracluster medium than light internally supersonic jets, possibly depositing a larger fraction of jet energy to cluster cores and alleviating the problem of low coupling efficiencies found previously. The internal Mach number points to the jet’s energy content, and internally subsonic jets are energetically dominated by non-kinetic energy, such as thermal energy, cosmic rays, or magnetic fields.

Neutralino dark matter and other LHC predictions from quasi Yukawa unification

DOE PAGES

Shafi, Qaisar; Tanyıldızı, Şükrü Hanif; Ün, Cem Salih

2015-10-01

We explore the dark matter and LHC implications of t-b-τt-b-τ quasi Yukawa unification in the framework of supersymmetric models based on the gauge symmetry G=SU(4) c×SU(2) L×SU(2) R. The deviation from exact Yukawa unification is quantified by a dimensionless parameter C (|C|≲0.2|C|≲0.2), such that the Yukawa couplings at M GUT are related by y t:y b:y τ=|1+C|:|1-C|:|1+3C|. In contrast to earlier studies which focused on universal gaugino masses, we consider non-universal gaugino masses at M GUT that are compatible with the gauge symmetry G. Our results reveal a variety of neutralino dark matter scenarios consistent with the observations. These includemore » stau and chargino coannihilation scenarios, the A -resonance scenario, as well as Higgsino dark matter solutions which are more readily probed by direct detection searches. The gluino mass is found to be ≲4 TeV≲4 TeV, the stop mass is ≳2 TeV≳2 TeV, while the first two family squarks and sleptons are of order 4–5 TeV and 3 TeV respectively.« less

Effects on the optical properties and conductivity of Ag-N co-doped ZnO

NASA Astrophysics Data System (ADS)

Xu, Zhenchao; Hou, Qingyu; Qu, Lingfeng

2017-01-01

Nowadays, the studies of the effects on the optical bandgap, absorption spectrum, and electrical properties of Ag-N co-doped ZnO have been extensively investigated. However, Ag and N atoms in doped systems are randomly doped, and the asymmetric structure of ZnO is yet to be explored. In this paper, the geometric structure, stability, density of states, absorption spectra and conductivity of pure and Ag-N co-doped Zn1-xAgxO1-xNx(x=0.03125, 0.0417 and 0.0625) in different orientations are calculated by using plane-wave ultrasoft pseudopotential on the basis of density functional theory with GGA+U method. Results show that the volume, equivalent total energy and formation energy of the doped system increase as the concentration of Ag-N co-doped Zn1-xAgxO1-xNx increases at the same doping mode. The doped systems also become unstable, and difficulty in doping. At the same concentration of Ag-N co-doped Zn1-xAgxO1-xNx, the systems with Ag-N along the c-axis orientation is unstable, and doping is difficult. The optical bandgap of Ag-N co-doped systems is narrower than that of the pure ZnO. At the same doping mode, the optical bandgap of the systems with Ag-N perpendicular to the c-axis orientation becomes narrow as the concentration of Ag-N co-doped Zn1-xAgxO1-xNx increases. The absorption spectra of the doped systems exhibit a red shift, and this red shift becomes increasingly significant as the concentration of Ag-N co-doped Zn1-xAgxO1-xNx increases. Under the same condition, the relative hole concentrations of the doped systems increases, the hole effective mass in valence band maximum decreases, the hole mobility decreases, the ionization energy decreases, Bohr radius increases, the conductance increases and the conductivity become better. Our results may be used as a basis for the designing and preparation of new optical and electrical materials for Ag-N co-doped ZnO applied in low temperature end of temperature difference battery.

Star formation in AGNs at the hundred parsec scale using MIR high-resolution images

NASA Astrophysics Data System (ADS)

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.

Host Galaxy Morphologies Of Hard X-ray Selected AGN From The Swift BAT Survey

NASA Astrophysics Data System (ADS)

Koss, Michael; Mushotzky, R.; Veilleux, S.

2009-01-01

Surveys of AGN taken in the optical, UV, and soft X-rays miss an important population of obscured AGN only visible in the hard X-rays and mid-IR wavelengths. The SWIFT BAT survey in the hard X-ray range (14-195 keV) has provided a uniquely unbiased sample of 258 AGN unaffected by galactic or circumnuclear absorption. Optical imaging of this unbiased sample provides a new opportunity to understand how the environments of the host galaxies are linked to AGN. For these host galaxies, only a fraction, 29%, have high quality optical images, predominately from the SDSS. In addition, about 33% show peculiar morphologies and interaction. In 2008, we observed 110 of these targets at Kitt Peak with the 2.1m in the SDSS bands over 17 nights. Using these observations and SDSS data we review the relationships between color, morphology, merger activity, star formation, and AGN luminosity.

The effect of AGN feedback on the X-ray morphologies of clusters: Simulations vs. observations

NASA Astrophysics Data System (ADS)

Chon, Gayoung; Puchwein, Ewald; Böhringer, Hans

2016-07-01

Clusters of galaxies probe the large-scale distribution of matter and are a useful tool to test the cosmological models by constraining cosmic structure growth and the expansion of the Universe. It is the scaling relations between mass observables and the true mass of a cluster through which we obtain the cosmological constraints by comparing to theoretical cluster mass functions. These scaling relations are, however, heavily influenced by cluster morphology. The presence of the slight tension in recent cosmological constraints on Ωm and σ8 based on the CMB and clusters has boosted the interests in looking for possible sources for the discrepancy. Therefore we study here the effect of active galactic nucleus (AGN) feedback as one of the major mechanisms modifying the cluster morphology influencing scaling relations. It is known that AGN feedback injects energies up to 1062 erg into the intracluster medium, controls the heating and cooling of a cluster, and re-distributes cold gas from the centre to outer radii. We have also learned that cluster simulations with AGN feedback can reproduce observed cluster properties, for example, the X-ray luminosity, temperature, and cooling rate at the centre better than without the AGN feedback. In this paper using cosmological hydrodynamical simulations we investigate how the AGN feedback changes the X-ray morphology of the simulated systems, and compare this to the observed Representative XMM-Newton Cluster Structure Survey (REXCESS) clusters. We apply two substructure measures, centre shifts (w) and power ratios (e.g. P3/P0), to characterise the cluster morphology, and find that our simulated clusters are more substructured than the observed clusters based on the values of w and P3/P0. We also 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 LX-T relation, they are also more substructured

Exploring the Use of Enterprise Content Management Systems in Unification Types of Organizations

NASA Astrophysics Data System (ADS)

Izza Arshad, Noreen; Mehat, Mazlina; Ariff, Mohamed Imran Mohamed

2014-03-01

The aim of this paper is to better understand how highly standardized and integrated businesses known as unification types of organizations use Enterprise Content Management Systems (ECMS) to support their business processes. Multiple case study approach was used to study the ways two unification organizations use their ECMS in their daily work practices. Arising from these case studies are insights into the differing ways in which ECMS is used to support businesses. Based on the comparisons of the two cases, this study proposed that unification organizations may use ECMS in four ways, for: (1) collaboration, (2) information sharing that supports a standardized process structure, (3) building custom workflows that support integrated and standardized processes, and (4) providing links and access to information systems. These findings may guide organizations that are highly standardized and integrated in fashion, to achieve their intended ECMS-use, to understand reasons for ECMS failures and underutilization and to exploit technologies investments.

The nature and energetics of AGN-driven perturbations in the hot gas in the Perseus Cluster

DOE PAGES

Zhuravleva, I.; Churazov, E.; Arevalo, P.; ...

2016-03-07

In this paper, cores of relaxed galaxy clusters are often disturbed by AGN. Their Chandra observations revealed a wealth of structures induced by shocks, subsonic gas motions, bubbles of relativistic plasma, etc. In this paper, we determine the nature and energy content of gas fluctuations in the Perseus core by probing statistical properties of emissivity fluctuations imprinted in the soft- and hard-band X-ray images. About 80 per cent of the total variance of perturbations on ~8–70 kpc scales in the core have an isobaric nature, i.e. are consistent with subsonic displacements of the gas in pressure equilibrium with the ambientmore » medium. The observed variance translates to the ratio of energy in perturbations to thermal energy of ~13 per cent. In the region dominated by weak ‘ripples’, about half of the total variance is associated with isobaric perturbations on scales of a few tens of kpc. If these isobaric perturbations are induced by buoyantly rising bubbles, then these results suggest that most of the AGN-injected energy should first go into bubbles rather than into shocks. Using simulations of a shock propagating through the Perseus atmosphere, we found that models reproducing the observed features of a central shock have more than 50 per cent of the AGN-injected energy associated with the bubble enthalpy and only about 20 per cent is carried away with the shock. Such energy partition is consistent with the AGN-feedback model, mediated by bubbles of relativistic plasma, and supports the importance of turbulence in the cooling–heating balance.« less

The nature and energetics of AGN-driven perturbations in the hot gas in the Perseus Cluster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhuravleva, I.; Churazov, E.; Arevalo, P.

In this paper, cores of relaxed galaxy clusters are often disturbed by AGN. Their Chandra observations revealed a wealth of structures induced by shocks, subsonic gas motions, bubbles of relativistic plasma, etc. In this paper, we determine the nature and energy content of gas fluctuations in the Perseus core by probing statistical properties of emissivity fluctuations imprinted in the soft- and hard-band X-ray images. About 80 per cent of the total variance of perturbations on ~8–70 kpc scales in the core have an isobaric nature, i.e. are consistent with subsonic displacements of the gas in pressure equilibrium with the ambientmore » medium. The observed variance translates to the ratio of energy in perturbations to thermal energy of ~13 per cent. In the region dominated by weak ‘ripples’, about half of the total variance is associated with isobaric perturbations on scales of a few tens of kpc. If these isobaric perturbations are induced by buoyantly rising bubbles, then these results suggest that most of the AGN-injected energy should first go into bubbles rather than into shocks. Using simulations of a shock propagating through the Perseus atmosphere, we found that models reproducing the observed features of a central shock have more than 50 per cent of the AGN-injected energy associated with the bubble enthalpy and only about 20 per cent is carried away with the shock. Such energy partition is consistent with the AGN-feedback model, mediated by bubbles of relativistic plasma, and supports the importance of turbulence in the cooling–heating balance.« less

The small observed scale of AGN-driven outflows, and inside-out disc quenching

NASA Astrophysics Data System (ADS)

Zubovas, Kastytis; King, Andrew

2016-11-01

Observations of massive outflows with detectable central active galactic nuclei (AGN) typically find them within radii ≲10 kpc. We show that this apparent size restriction is a natural result of AGN driving if this process injects total energy only of the order of the gas binding energy to the outflow, and the AGN varies over time (`flickers') as suggested in recent work. After the end of all AGN activity, the outflow continues to expand to larger radii, powered by the thermal expansion of the remnant-shocked AGN wind. We suggest that on average, outflows should be detected further from the nucleus in more massive galaxies. In massive gas-rich galaxies, these could be several tens of kpc in radius. We also consider the effect that pressure of such outflows has on a galaxy disc. In moderately gas-rich discs, with gas-to-baryon fraction <0.2, the outflow may induce star formation significant enough to be distinguished from quiescent by an apparently different normalization of the Kennicutt-Schmidt law. The star formation enhancement is probably stronger in the outskirts of galaxy discs, so coasting outflows might be detected by their effects upon the disc even after the driving AGN has shut off. We compare our results to the recent inference of inside-out quenching of star formation in galaxy discs.

SDSS IV MaNGA - Properties of AGN Host Galaxies

NASA Astrophysics Data System (ADS)

Sánchez, S. F.; Avila-Reese, V.; Hernandez-Toledo, H.; Cortes-Suárez, E.; Rodríguez-Puebla, A.; Ibarra-Medel, H.; Cano-Díaz, M.; Barrera-Ballesteros, J. K.; Negrete, C. A.; Calette, A. R.; de Lorenzo-Cáceres, A.; Ortega-Minakata, R. A.; Aquino, E.; Valenzuela, O.; Clemente, J. C.; Storchi-Bergmann, T.; Riffel, R.; Schimoia, J.; Riffel, R. A.; Rembold, S. B.; Brownstein, J. R.; Pan, K.; Yates, R.; Mallmann, N.; Bitsakis, T.

2018-04-01

We present the characterization of the main properties of a sample of 98 AGN host galaxies, both type-II and type-I, in comparison with those of ≍2700 non-active galaxies observed by the MaNGA survey. We found that AGN hosts are morphologically early-type or early-spirals. AGN hosts are, on average, more massive, more compact, more centrally peaked and more pressure-supported systems. They are located in the intermediate/transition region between starforming and non-star-forming galaxies (i.e., the so-called green valley). We consider that they are in the process of halting/quenching the star formation. The analysis of the radial distributions of different properties shows that the quenching happens from inside-out involving both a decrease of the effciency of the star formation and a deficit of molecular gas. The data-products of the current analysis are distributed as a Value Added Catalog within the SDSS-DR14.

Merging and Clustering of the Swift BAT AGN Sample

NASA Astrophysics Data System (ADS)

Koss, Michael; Mushotzky, Richard; Veilleux, Sylvain; Winter, Lisa

2010-06-01

We discuss the merger rate, close galaxy environment, and clustering on scales up to an Mpc of the Swift BAT hard X-ray sample of nearby (z<0.05), moderate-luminosity active galactic nuclei (AGNs). 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 AGNs at scales up to 250 kpc. We hypothesize that these merging AGNs 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 [O III] flux ratio, as well as emission line diagnostics characteristic of composite or star-forming galaxies, and a larger IRAS 60 μm to stellar mass ratio.

Red Geyser: A New Class of Galaxy with Large-scale AGN-driven Winds

NASA Astrophysics Data System (ADS)

Roy, Namrata; Bundy, Kevin; Cheung, Edmond; MaNGA Team

2018-01-01

A new class of quiescent (non-star-forming) galaxies harboring possible AGN-driven winds have been discovered using the spatially resolved optical spectroscopy from the ongoing SDSS-IV MaNGA (Sloan Digital Sky Survey-IV Mapping Nearby Galaxies at Apache Point Observatory) survey. These galaxies named "red geysers" constitute 5%-10% of the local quiescent galaxy population and are characterized by narrow bisymmetric ionized gas emission patterns. These enhanced patterns are seen in equivalent width maps of Hα, [OIII] and other strong emission lines. They are co-aligned with the ionized gas velocity gradients but significantly misaligned with stellar velocity gradients. They also show very high gas velocity dispersions (~200 km/s). Considering these observations in light of models of the gravitational potential, Cheung et al. argued that red geysers host large-scale AGN-driven winds of ionized gas that may play a role in suppressing star formation at late times. In this work, we test the hypothesis that AGN activity is ultimately responsible for the red geyser phenomenon. We compare the nuclear radio activity of the red geysers to a matched control sample of galaxies of similar stellar mass, redshift, rest frame NUV–r color and axis ratio. and additionally, control for the presence of ionized gas. We have used 1.4 GHz radio continuum data from the VLA FIRST Survey to stack the radio flux from the red geyser sample and control sample. We find that the red geysers have a higher average radio flux than the control galaxies at > 3σ significance. Our sample is restricted to rest-frame NUV–r color > 5, thus ruling out possible radio emission due to star formation activity. We conclude that red geysers are associated with more active AGN, supporting a feedback picture in which episodic AGN activity drives large-scale but relatively weak ionized winds in many in many early-type galaxies.

Discovering highly obscured AGN with the Swift-BAT 100-month survey

NASA Astrophysics Data System (ADS)

Marchesi, Stefano; Ajello, Marco; Comastri, Andrea; Cusumano, Giancarlo; La Parola, Valentina; Segreto, Alberto

2017-01-01

In this talk, I present a new technique to find highly obscured AGN using the 100-month Swift-BAT survey. I will show the results of the combined Chandra and BAT spectral analysis in the 0.3-150 keV band of seven Seyfert 2 galaxies selected from the 100-month BAT catalog. We selected nearby (z<0.03) sources lacking of a ROSAT counterpart and never previously observed in the 0.3-10 keV energy range. All the objects are significantly obscured, having NH>1E23 cm-2 at a >99% confidence level, and one to three sources are candidate Compton thick Active Galactic Nuclei (CT-AGN), i.e., have NH>1E24 cm-2.Since the selection criteria we adopted have been extremely effective in detecting highly obscured AGN, further observations of these and other Seyfert 2 galaxies selected from the BAT 100-month catalog will allow us to create a statistically significant sample of highly obscured AGN, therefore better understanding the physics of the obscuration processes.

AGN radiative feedback in dusty quasar populations

NASA Astrophysics Data System (ADS)

Ishibashi, W.; Banerji, M.; Fabian, A. C.

2017-08-01

New populations of hyper-luminous, dust-obscured quasars have been recently discovered around the peak epoch of galaxy formation (z ˜ 2-3), in addition to similar sources found at lower redshifts. Such dusty quasars are often interpreted as sources 'in transition', from dust-enshrouded starbursts to unobscured luminous quasars, along the evolutionary sequence. Here we consider the role of the active galactic nucleus (AGN) radiative feedback, driven by radiation pressure on dust, in high-luminosity, dust-obscured sources. We analyse how the radiation pressure-driven dusty shell models, with different shell mass configurations, may be applied to the different populations of dusty quasars reported in recent observations. We find that expanding shells, sweeping up matter from the surrounding environment, may account for prolonged obscuration in dusty quasars, e.g. for a central luminosity of L ˜ 1047 erg s-1, a typical obscured phase (with extinction in the range AV ˜ 1-10 mag) may last a few ˜106 yr. On the other hand, fixed-mass shells, coupled with high dust-to-gas ratios, may explain the extreme outflows recently discovered in red quasars at high redshifts. We discuss how the interaction between AGN radiative feedback and the ambient medium at different temporal stages in the evolutionary sequence may contribute to shape the observational appearance of dusty quasar populations.

Reality and myths of AGN feedback

NASA Astrophysics Data System (ADS)

Husemann, Bernd; Harrison, Chris M.

2018-03-01

Feedback from active galactic nuclei (AGNs) remains controversial despite its wide acceptance as necessary to regulate massive galaxy growth. Consequently, we held a workshop in October 2017, at Leiden's Lorentz Center, to distinguish between the reality and myths of feedback.

Unification theory of optimal life histories and linear demographic models in internal stochasticity.

PubMed

Oizumi, Ryo

2014-01-01

Life history of organisms is exposed to uncertainty generated by internal and external stochasticities. Internal stochasticity is generated by the randomness in each individual life history, such as randomness in food intake, genetic character and size growth rate, whereas external stochasticity is due to the environment. For instance, it is known that the external stochasticity tends to affect population growth rate negatively. It has been shown in a recent theoretical study using path-integral formulation in structured linear demographic models that internal stochasticity can affect population growth rate positively or negatively. However, internal stochasticity has not been the main subject of researches. Taking account of effect of internal stochasticity on the population growth rate, the fittest organism has the optimal control of life history affected by the stochasticity in the habitat. The study of this control is known as the optimal life schedule problems. In order to analyze the optimal control under internal stochasticity, we need to make use of "Stochastic Control Theory" in the optimal life schedule problem. There is, however, no such kind of theory unifying optimal life history and internal stochasticity. This study focuses on an extension of optimal life schedule problems to unify control theory of internal stochasticity into linear demographic models. First, we show the relationship between the general age-states linear demographic models and the stochastic control theory via several mathematical formulations, such as path-integral, integral equation, and transition matrix. Secondly, we apply our theory to a two-resource utilization model for two different breeding systems: semelparity and iteroparity. Finally, we show that the diversity of resources is important for species in a case. Our study shows that this unification theory can address risk hedges of life history in general age-states linear demographic models.

Unification Theory of Optimal Life Histories and Linear Demographic Models in Internal Stochasticity

PubMed Central

Oizumi, Ryo

2014-01-01

Life history of organisms is exposed to uncertainty generated by internal and external stochasticities. Internal stochasticity is generated by the randomness in each individual life history, such as randomness in food intake, genetic character and size growth rate, whereas external stochasticity is due to the environment. For instance, it is known that the external stochasticity tends to affect population growth rate negatively. It has been shown in a recent theoretical study using path-integral formulation in structured linear demographic models that internal stochasticity can affect population growth rate positively or negatively. However, internal stochasticity has not been the main subject of researches. Taking account of effect of internal stochasticity on the population growth rate, the fittest organism has the optimal control of life history affected by the stochasticity in the habitat. The study of this control is known as the optimal life schedule problems. In order to analyze the optimal control under internal stochasticity, we need to make use of “Stochastic Control Theory” in the optimal life schedule problem. There is, however, no such kind of theory unifying optimal life history and internal stochasticity. This study focuses on an extension of optimal life schedule problems to unify control theory of internal stochasticity into linear demographic models. First, we show the relationship between the general age-states linear demographic models and the stochastic control theory via several mathematical formulations, such as path–integral, integral equation, and transition matrix. Secondly, we apply our theory to a two-resource utilization model for two different breeding systems: semelparity and iteroparity. Finally, we show that the diversity of resources is important for species in a case. Our study shows that this unification theory can address risk hedges of life history in general age-states linear demographic models. PMID:24945258

THE OBSCURED FRACTION OF ACTIVE GALACTIC NUCLEI IN THE XMM-COSMOS SURVEY: A SPECTRAL ENERGY DISTRIBUTION PERSPECTIVE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lusso, E.; Hennawi, J. F.; Richards, G. T.

2013-11-10

The fraction of active galactic nucleus (AGN) luminosity obscured by dust and re-emitted in the mid-IR is critical for understanding AGN evolution, unification, and parsec-scale AGN physics. For unobscured (Type 1) AGNs, where we have a direct view of the accretion disk, the dust covering factor can be measured by computing the ratio of re-processed mid-IR emission to intrinsic nuclear bolometric luminosity. We use this technique to estimate the obscured AGN fraction as a function of luminosity and redshift for 513 Type 1 AGNs from the XMM-COSMOS survey. The re-processed and intrinsic luminosities are computed by fitting the 18 bandmore » COSMOS photometry with a custom spectral energy distribution fitting code, which jointly models emission from hot dust in the AGN torus, from the accretion disk, and from the host galaxy. We find a relatively shallow decrease of the luminosity ratio as a function of L{sub bol}, which we interpret as a corresponding decrease in the obscured fraction. In the context of the receding torus model, where dust sublimation reduces the covering factor of more luminous AGNs, our measurements require a torus height that increases with luminosity as h ∝ L{sub bol}{sup 0.3-0.4}. Our obscured-fraction-luminosity relation agrees with determinations from Sloan Digital Sky Survey censuses of Type 1 and Type 2 quasars and favors a torus optically thin to mid-IR radiation. We find a much weaker dependence of the obscured fraction on 2-10 keV luminosity than previous determinations from X-ray surveys and argue that X-ray surveys miss a significant population of highly obscured Compton-thick AGNs. Our analysis shows no clear evidence for evolution of the obscured fraction with redshift.« less

Obscured AGN at z ~ 1 from the zCOSMOS-Bright Survey. I. Selection and optical properties of a [Ne v]-selected sample

NASA Astrophysics Data System (ADS)

Mignoli, M.; Vignali, C.; Gilli, R.; Comastri, A.; Zamorani, G.; Bolzonella, M.; Bongiorno, A.; Lamareille, F.; Nair, P.; Pozzetti, L.; Lilly, S. J.; Carollo, C. M.; Contini, T.; Kneib, J.-P.; Le Fèvre, O.; Mainieri, V.; Renzini, A.; Scodeggio, M.; Bardelli, S.; Caputi, K.; Cucciati, O.; de la Torre, S.; de Ravel, L.; Franzetti, P.; Garilli, B.; Iovino, A.; Kampczyk, P.; Knobel, C.; Kovač, K.; Le Borgne, J.-F.; Le Brun, V.; Maier, C.; Pellò, R.; Peng, Y.; Perez Montero, E.; Presotto, V.; Silverman, J. D.; Tanaka, M.; Tasca, L.; Tresse, L.; Vergani, D.; Zucca, E.; Bordoloi, R.; Cappi, A.; Cimatti, A.; Koekemoer, A. M.; McCracken, H. J.; Moresco, M.; Welikala, N.

2013-08-01

particular the most heavily obscured ones, but cannot provide a complete census of type 2 AGN by itself. Finally, the high fraction of [Ne v]-selected type 2 AGN not detected in medium-deep (≈100-200 ks) Chandra observations (67%) is suggestive of the inclusion of Compton-thick (i.e., with NH > 1024 cm-2) sources in our sample. The presence of a population of heavily obscured AGN is corroborated by the X-ray-to-[Ne v] ratio; we estimated, by means of an X-ray stacking technique and simulations, that the Compton-thick fraction in our sample of type 2 AGN is 43 ± 4% (statistical errors only), which agrees well with standard assumptions by XRB synthesis models.

750 GeV diphotons: implications for supersymmetric unification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hall, Lawrence J.; Harigaya, Keisuke; Nomura, Yasunori

2016-03-03

A recent signal of 750 GeV diphotons at the LHC can be explained within the framework of supersymmetric unification by the introduction of vector quarks and leptons with Yukawa couplings to a singlet S that describes the 750 GeV resonance. We study the most general set of theories that allow successful gauge coupling unification, and find that these Yukawa couplings are severely constrained by renormalization group behavior: they are independent of ultraviolet physics and flow to values at the TeV scale that we calculate precisely. As a consequence the vector quarks and leptons must be light; typically in the regionmore » of 375 GeV to 700 GeV, and in certain cases up to 1 TeV. The 750 GeV resonance may have a width less than the experimental resolution; alternatively, with the mass splitting between scalar and pseudoscalar components of S arising from one-loop diagrams involving vector fermions, we compute an apparent width of 10s of GeV.« less

Ultra-Fast Outflows in Radio-Loud AGN: New Constraints on Jet-Disk Connection

NASA Astrophysics Data System (ADS)

Sambruna, Rita

There is strong observational and theoretical evidence that outflows/jets are coupled to accretion disks in black hole accreting systems, from Galactic to extragalactic sizes. While in radio-quiet AGN there is ample evidence for the presence of Ultra-Fast Outflows (UFOs) from the presence of blue-shifted absorption features in their 4-10~keV spectra, sub-relativistic winds are expected on theoretical basis in radio-loud AGN but have not been observed until now. Our recent Suzaku observations of 5 bright Broad- Line Radio Galaxies (BLRGs, the radio-loud counterparts of Seyferts) has started to change this picture. We found strong evidence for UFOs in 3 out of 5 BLRGs, with ionization parameters, column densities, and velocities of the absorber similar to Seyferts. Moreover, the outflows in BLRGs are likely to be energetically very significant: from the Suzaku data of the three sources, outflow masses similar to the accretion masses and kinetic energies of the wind similar to the X-ray luminosity and radio power of the jet are inferred. Clearly, UFOs in radio-loud AGN represent a new key ingredient to understand their central engines and in particular, the jet-disk linkage. Our discovery of UFOs in a handful of BLRGs raises the questions of how common disk winds are in radio-loud AGN, what the absorber physical and dynamical characteristics are, and what is the outflow role in broader picture of galaxy-black hole connection for radio sources, i.e., for large-scale feedback models. To address these and other issues, we propose to use archival XMM-Newton and Suzaku spectra to search for Ultra-Fast Outflows in a large number of radio sources. Over a period of two years, we will conduct a systematic, uniform analysis of the archival X-ray data, building on our extensive experience with a similar previous project for Seyferts, and using robust analysis and statistical methodologies. As an important side product, we will also obtain accurate, self- consistent measurements

Measuring AGN & Starburst Wind Properties with ALMA

NASA Astrophysics Data System (ADS)

Lacy, Mark; Chatterjee, Suchetana; Nyland, Kristina; Kimball, Amy; Mason, Brian; Rocha, Graca

2018-01-01

The Sunyaev-Zeldovich (SZ) effect is one of the few ways to constrain the energetically-dominant hot component of winds from AGN and starbursts. Studies of stacked data from Planck and ground-based mm/submm single dish telescopes have found significant detections of SZ from quasars, but contamination from other phenomena are hard to rule out given the large beams of single dishes. Direct detection of these winds is just feasible with observations with current facilities (VLA and ALMA), but with ngVLA we should be able to go beyond detections, and start to map the SZ effect around these objects. In this poster I will present predictions for the detectability of SZ decrements from AGN and hyperluminous starbursts using ngVLA parameters.

Leptoquark mechanism of neutrino masses within the grand unification framework

NASA Astrophysics Data System (ADS)

Doršner, Ilja; Fajfer, Svjetlana; Košnik, Nejc

2017-06-01

We demonstrate the viability of the one-loop neutrino mass mechanism within the framework of grand unification when the loop particles comprise scalar leptoquarks (LQs) and quarks of the matching electric charge. This mechanism can be implemented in both supersymmetric and non-supersymmetric models and requires the presence of at least one LQ pair. The appropriate pairs for the neutrino mass generation via the up-type and down-type quark loops are S_3-R_2 and S_{1, 3}-\\tilde{R}_2, respectively. We consider two distinct regimes for the LQ masses in our analysis. The first regime calls for very heavy LQs in the loop. It can be naturally realized with the S_{1, 3}-\\tilde{R}_2 scenarios when the LQ masses are roughly between 10^{12} and 5 × 10^{13} GeV. These lower and upper bounds originate from experimental limits on partial proton decay lifetimes and perturbativity constraints, respectively. Second regime corresponds to the collider accessible LQs in the neutrino mass loop. That option is viable for the S_3-\\tilde{R}_2 scenario in the models of unification that we discuss. If one furthermore assumes the presence of the type II see-saw mechanism there is an additional contribution from the S_3-R_2 scenario that needs to be taken into account beside the type II see-saw contribution itself. We provide a complete list of renormalizable operators that yield necessary mixing of all aforementioned LQ pairs using the language of SU(5). We furthermore discuss several possible embeddings of this mechanism in SU(5) and SO(10) gauge groups.

Educational Systems and Rising Inequality: Eastern Germany after Unification

ERIC Educational Resources Information Center

von Below, Susanne; Powell, Justin J. W.; Roberts, Lance W.

2013-01-01

Educational systems considerably influence educational opportunities and the resulting social inequalities. Contrasting institutional regulations of both structures and contents, the authors present a typology of educational system types in Germany to analyze their effects on social inequality in eastern Germany after unification. After 1990, the…

Near-infrared Variability of Obscured and Unobscured X-Ray-selected AGNs in the COSMOS Field

NASA Astrophysics Data System (ADS)

Sánchez, P.; Lira, P.; Cartier, R.; Pérez, V.; Miranda, N.; Yovaniniz, C.; Arévalo, P.; Milvang-Jensen, B.; Fynbo, J.; Dunlop, J.; Coppi, P.; Marchesi, S.

2017-11-01

We present our statistical study of near-infrared (NIR) variability of X-ray-selected active galactic nuclei (AGNs) in the COSMOS field, using UltraVISTA data. This is the largest sample of AGN light curves in YJHKs bands, making it possible to have a global description of the nature of AGNs for a large range of redshifts and for different levels of obscuration. To characterize the variability properties of the sources, we computed the structure function. Our results show that there is an anticorrelation between the structure function A parameter (variability amplitude) and the wavelength of emission and a weak anticorrelation between A and the bolometric luminosity. We find that broad-line (BL) AGNs have a considerably larger fraction of variable sources than narrow-line (NL) AGNs and that they have different distributions of the A parameter. We find evidence that suggests that most of the low-luminosity variable NL sources correspond to BL AGNs, where the host galaxy could be damping the variability signal. For high-luminosity variable NL sources, we propose that they can be examples of “true type II” AGNs or BL AGNs with limited spectral coverage, which results in missing the BL emission. We also find that the fraction of variable sources classified as unobscured in the X-ray is smaller than the fraction of variable sources unobscured in the optical range. We present evidence that this is related to the differences in the origin of the obscuration in the optical and X-ray regimes.

VizieR Online Data Catalog: AGN torus models. SED library (Siebenmorgen+, 2015)

NASA Astrophysics Data System (ADS)

Siebenmorgen, R.; Heymann, F.; Efstathiou, A.

2015-08-01

There are 3600 ASCII tables files in two columns format. The first is the wavelength in microns, the second column is the flux in Jy. SEDs are computed for AGNs at a distance of 50Mpc and a luminosity of 1011L⊙. The file names include the five basic model parameters: a) th: The viewing angle corresponding to bins at 86, 80, 73, 67, 60, 52, 43, 33, and 19 degree measured from the pole (z-axis). thx= th1 ,.., th9 b) R : The inner radius of the dusty torus. R= 300, 514, 772, 1000, 1545 in units: (10^15 cm) c) Vc: The cloud volume filling factor. Vc= 1.5, 7.7, 38.5, 77.7 (%). d) Ac: The optical depth (in V) of the individual clouds. Ac= 0, 4.5, 13.5, 45. e) Ad: The optical depth (in V) of the disk midplane. Ad= 0, 30, 100, 300, 1000. Example: File notation. RxxxxVcxxxAcxxxx_Adxxxx.thx R1545Vc777Ac0135_Ad1000.th9 (2 data files).

Photoionization Modeling with TITAN Code, Distance to the Warm Absorber in AGN

NASA Astrophysics Data System (ADS)

Różańska, A.

2012-08-01

We present a method that allows us to estimate a distance from the source of continuum radiation located in the center of AGN to the highly ionized gas - warm absorber (WA). We computed a set of constant total pressure photoionization models compatible with the warm absorber conditions, where a metal-rich gas is irradiated by a continuum in the form of a double powerlaw. The first powerlaw is hard, up to 100 keV, and represents radiation from an X-ray source, while the second powerlaw extends up to several eV, and illustrates radiation from an accretion disk. When the ionized continuum is dominated by the soft component, the warm absorber is heated by free-free absorption, instead of Comptonization, and the transmitted spectra show different absorption-line characteristics for different values of the hydrogen number density at the cloud illuminated surface. This fact results in the possibility of deriving the number density on the cloud illuminated side from observations, and hence the distance to the warm absorber.

Investigating Possible Outliers in the Fermi Blazar AGN Sample

NASA Astrophysics Data System (ADS)

Shrader, Chris

2018-01-01

The Fermi Gamma-Ray Space Telescope (Fermi) has cataloged over 3000 gamma-ray (>100 MeV) point sources of which more than 1100 are likely AGN. These AGN are predominantly among the radio-loud “blazar” subclass. Recently however, a significant sample of bright (F_15GHz >1.5 Jy), radio selected AGN was found to overlap with Fermi at only the ~80% level (Lister et. al., 2015). This could be a result of some selection bias or it could be due to deficient Doppler boosting among that ~20%. Additionally, a recent survey of high-latitude gamma-ray sources by Schinzel et al. (2017) reveals a sample of ~100 objects which are not detected in the 4-10 GHz radio band to a limiting flux of about 2mJy. This apparent lack of radio flux is puzzling, and may indicate either an extreme Compton-dominated sample, or copious gamma-ray emission from a heretofore unknown population such as a subclass of radio-quiet AGN. Speculatively, these radio-loud/gamma-quiet and gamma-loud/radio quiet samples could be odd cases of the blazar phenomena which reside outside of the well-known blazar sequence. To explore this problem further we have undertaken a study to construct or constrain individual source SEDs as a first step towards their classification. In this contribution we present results from our search for emission in the Swift-BAT 15-100-keV hard X-ray band for each of these samples.

IC 3639 - A New Bona Fide Compton-Thick AGN Unveiled By NuSTAR

NASA Technical Reports Server (NTRS)

Boorman, Peter G.; Gandhi, P.; Alexander, D. M.; Annuar, A.; Ballantyne, D. R.; Bauer, F.; Boggs, S. E.; Brandt, W. N.; Brightman, M.; Christensen, F. E.;

ON THE IMPORTANCE OF VERY LIGHT INTERNALLY SUBSONIC AGN JETS IN RADIO-MODE AGN FEEDBACK

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Fulai, E-mail: fulai@shao.ac.cn

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 kiloparsec-scale interaction of AGN jets with the intracluster medium. Large-scale jet simulations often initiate light internally supersonic jets with density contrast 0.01 < η < 1. Here we argue for the first time for the importance of very light ( η < 0.01) internally subsonic jets. We investigated the shapes of young X-ray cavities produced in a suite of hydrodynamic simulations, and found that bottom-wide cavities are always produced by internally subsonic jets, while internally supersonicmore » jets inflate cylindrical, center-wide, or top-wide cavities. We found examples of real cavities with shapes analogous to those inflated in our simulations 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 resulted from light jets spread along the jet direction, while those produced by very light jets are significantly elongated along the perpendicular direction. The northwestern ghost cavity in Perseus is pancake shaped, providing tentative evidence for the existence of very light jets. Our simulations show that very light internally subsonic jets decelerate faster and rise much slower in the intracluster medium than light internally supersonic jets, possibly depositing a larger fraction of jet energy to cluster cores and alleviating the problem of low coupling efficiencies found previously. The internal Mach number points to the jet’s energy content, and internally subsonic jets are energetically dominated by non-kinetic energy, such as thermal energy, cosmic rays, or magnetic fields.« less

Searching for Dual AGNs in Galaxy Mergers: Understanding Double-Peaked [O III] and Ultra Hard X-rays as Selection Method

NASA Astrophysics Data System (ADS)

McGurk, Rosalie C.; Max, Claire E.; Medling, Anne; Shields, Gregory A.

2015-01-01

When galaxies merge, gas accretes onto both central supermassive black holes. Thus, one expects to see close pairs of active galactic nuclei (AGNs), or dual AGNs, in a fraction of galaxy mergers. However, finding them remains a challenge. The presence of double-peaked [O III] or of ultra hard X-rays have been proposed as techniques to select dual AGNs efficiently. We studied a sample of double-peaked narrow [O III] emitting AGNs from SDSS DR7. By obtaining new and archival high spatial resolution images taken with the Keck 2 Laser Guide Star Adaptive Optics system and the near-infrared (IR) camera NIRC2, we showed that 30% of double-peaked [O III] emission line SDSS AGNs have two spatial components within a 3' radius. However, spatially resolved spectroscopy or X-ray observations are needed to confirm these galaxy pairs as systems containing two AGNs. We followed up these spatially-double candidate dual AGNs with integral field spectroscopy from Keck OSIRIS and Gemini GMOS and with long-slit spectroscopy from Keck NIRSPEC and Shane Kast Double Spectrograph. We find double-peaked emitters are caused sometimes by dual AGN and sometimes by outflows or narrow line kinematics. We also performed Chandra X-ray ACIS-S observations on 12 double-peaked candidate dual AGNs. Using our observations and 8 archival observations, we compare the distribution of X-ray photons to our spatially double near-IR images, measure X-ray luminosities and hardness ratios, and estimate column densities. By assessing what fraction of double-peaked emission line SDSS AGNs are true dual AGNs, we can better determine whether double-peaked [O III] is an efficient dual AGN indicator and constrain the statistics of dual AGNs. A second technique to find dual AGN is the detection of ultra hard X-rays by the Swift Burst Alert Telescope. We use CARMA observations to measure and map the CO(1-0) present in nearby ultra-hard X-ray Active Galactic Nuclei (AGNs) merging with either a quiescent companion

IC 3639—a New Bona Fide Compton-Thick AGN Unveiled by NuSTAR

NASA Astrophysics Data System (ADS)

Boorman, Peter G.; Gandhi, P.; Alexander, D. M.; Annuar, A.; Ballantyne, D. R.; Bauer, F.; Boggs, S. E.; Brandt, W. N.; Brightman, M.; Christensen, F. E.; Craig, W. W.; Farrah, D.; Hailey, C. J.; Harrison, F. A.; Hönig, S. F.; Koss, M.; LaMassa, S. M.; Masini, A.; Ricci, C.; Risaliti, G.; Stern, D.; Zhang, W. W.

2016-12-01

We analyze high-quality NuSTAR observations of the local (z = 0.011) Seyfert 2 active galactic nucleus (AGN) IC 3639, in conjunction with archival Suzaku and Chandra data. This provides the first broadband X-ray spectral analysis of the source, spanning nearly two decades in energy (0.5-30 keV). Previous X-ray observations of the source below 10 keV indicated strong reflection/obscuration on the basis of a pronounced iron fluorescence line at 6.4 keV. The hard X-ray energy coverage of NuSTAR, together with self-consistent toroidal reprocessing models, enables direct broadband constraints on the obscuring column density of the source. We find the source to be heavily Compton-thick (CTK) with an obscuring column in excess of 3.6× {10}24 cm-2, unconstrained at the upper end. We further find an intrinsic 2-10 keV luminosity of {{log}}10({L}2{--10{keV}} [{erg} {{{s}}}-1])={43.4}-1.1+0.6 to 90% confidence, almost 400 times the observed flux, and consistent with various multiwavelength diagnostics. Such a high ratio of intrinsic to observed flux, in addition to an Fe-Kα fluorescence line equivalent width exceeding 2 keV, is extreme among known bona fide CTK AGNs, which we suggest are both due to the high level of obscuration present around IC 3639. Our study demonstrates that broadband spectroscopic modeling with NuSTAR enables large corrections for obscuration to be carried out robustly and emphasizes the need for improved modeling of AGN tori showing intense iron fluorescence.

Reversing cooling flows with AGN jets: shock waves, rarefaction waves and trailing outflows

NASA Astrophysics Data System (ADS)

Guo, Fulai; Duan, Xiaodong; Yuan, Ye-Fei

2018-01-01

The cooling flow problem is one of the central problems in galaxy clusters, and active galactic nucleus (AGN) feedback is considered to play a key role in offsetting cooling. However, how AGN jets heat and suppress cooling flows remains highly debated. Using an idealized simulation of a cool-core cluster, we study the development of central cooling catastrophe and how a subsequent powerful AGN jet event averts cooling flows, with a focus on complex gasdynamical processes involved. We find that the jet drives a bow shock, which reverses cooling inflows and overheats inner cool-core regions. The shocked gas moves outward in a rarefaction wave, which rarefies the dense core and adiabatically transports a significant fraction of heated energy to outer regions. As the rarefaction wave propagates away, inflows resume in the cluster core, but a trailing outflow is uplifted by the AGN bubble, preventing gas accumulation and catastrophic cooling in central regions. Inflows and trailing outflows constitute meridional circulations in the cluster core. At later times, trailing outflows fall back to the cluster centre, triggering central cooling catastrophe and potentially a new generation of AGN feedback. We thus envisage a picture of cool cluster cores going through cycles of cooling-induced contraction and AGN-induced expansion. This picture naturally predicts an anti-correlation between the gas fraction (or X-ray luminosity) of cool cores and the central gas entropy, which may be tested by X-ray observations.

2MASS J00423991+3017515: An Interacting Oddball or a Recoiling AGN?

NASA Astrophysics Data System (ADS)

Hogg, J. Drew; Blecha, Laura; Reynolds, Christopher S.

2017-06-01

We present deep, multiband Hubble imaging and two epochs of optical spectroscopic monitoring of a peculiar nearby (z=0.14) AGN, 2MASS J00423991+3017515. The host galaxy containing the AGN is morphologically disturbed and interacting with an unmerged companion galaxy, suggesting it has had a rich merger history. The AGN itself is spatially displaced from the apparent center of its host galaxy and the symmetric broad Hα and Hβ lines are consistently blueshifted from the narrow line emission and host galaxy absorption by Δv = 1530 km/s. The investigation is ongoing, but we put forward two hypotheses to explain the odd features of this system. First, the abnormalities could be due to separate, independent causes. Projection effects from the interaction of the two galaxies could give the appearance of a spatial offset, while complex wind dynamics from the AGN accretion disk could give rise to the kinematic shift in the broad line emission. Second, this could be a recoiling AGN. This system fits the template of an accreting supermassive black hole (SMBH) that has recently received a “kick” from the asymmetric emission of gravitational waves (GWs) following the merger of two progenitor SMBHs. SMBH mergers are a likely end-product of hierarchical structure formation and are the supermassive cousins of the stellar-mass BH mergers observed with LIGO in the GW150914 and GW151226 events. However, a SMBH merger has yet to be unambigously detected. If confirmed as a recoiling AGN, 2MASS J00423991+3017515 will provide the first evidence of this growth pathway acting in the SMBH regime.

Anomalous H-beta Variability in the 2014 NGC 5548 AGN-STORM Monitoring Campaign

NASA Astrophysics Data System (ADS)

Pei, Liuyi; AGN STORM Collaboration

2016-06-01

Reverberation mapping programs generally find that the continuum and H-beta flux variations in AGNs are well correlated. In the 2014 AGN STORM monitoring program for NGC 5548, we observed a distinct decorrelation of the emission-line light curves from the AGN continuum light curve during the second half of the six-month campaign. This effect was first detected for the C IV, Ly a, HeII 1640 and SiIV/OIV] 1400 lines in Hubble Space Telescope data, then observed for the H-beta line in ground-based data taken during the same monitoring period. We present measurements of the H-beta lags, equivalent width variations, and line responsivity changes during our campaign. We show that the AGN demonstrated unusual behavior in that the broad H-beta responsivity to flux variations decreased significantly during the second half of the campaign. The discovery of this decorrelation phenomenon was made possible by the high cadence and long duration of our monitoring campaign. More multi-wavelength observing campaigns with high sampling cadence, high signal-to-noise ratio, and long temporal baseline are needed for other AGNs in order to determine the prevalence of this phenomenon and to understand its physical origin.

Large-scale outflows in luminous QSOs revisited. The impact of beam smearing on AGN feedback efficiencies

NASA Astrophysics Data System (ADS)

Husemann, B.; Scharwächter, J.; Bennert, V. N.; Mainieri, V.; Woo, J.-H.; Kakkad, D.

2016-10-01

Context. Feedback from active galactic nuclei (AGN) is thought to play an important role in quenching star formation in galaxies. However, the efficiency with which AGN dissipate their radiative energy into the ambient medium remains strongly debated. Aims: Enormous observational efforts have been made to constrain the energetics of AGN feedback by mapping the kinematics of the ionized gas on kpc scale. We study how the observed kinematics and inferred energetics are affected by beam smearing of a bright unresolved narrow-line region (NLR) due to seeing. Methods: We re-analyse optical integral-field spectroscopy of a sample of twelve luminous unobscured quasi-stellar objects (QSOs) (0.4 model is reduced by two orders of magnitude for a conical outflow and one order of magnitude for the unresolved NLR after PSF deblending. This reduced kinetic power corresponds to only 0.01-0.1 per cent of the bolometric AGN luminosity. This is smaller than the 5-10% feedback efficiency required by some cosmological simulations to reproduce the massive galaxy population. The injected momentum fluxes are close or below the simple radiation-pressure limit Lbol/c for the conical outflow model for the NLR and ENLR

Highly variable AGN from the XMM-Newton slew survey

NASA Astrophysics Data System (ADS)

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

2016-07-01

Aims: We investigate the properties of a variability-selected complete sample of active galactic nuclei (AGN) in order to identify the mechanisms which cause large amplitude X-ray variability on timescales of years. Methods: 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-Newton slew survey. Follow-up observations were obtained with the Swift satellite. We analysed the spectra of these AGN at the Swift and XMM observation epochs, where six sources had continued to display extreme variability. Multiwavelength data are used to calculate black hole masses and the relative X-ray brightness αOX. Results: 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 (2σ) and X-ray luminosity (1.7σ). Apart from two radio-loud sources, the sample sources have normal optical-X-ray ratios (αOX) when at their peak but are X-ray weak during their lowest flux measurements. Conclusions: Drawing on our results and other studies, we are able to identify a variety of variability mechanisms at play: tidal disruption events, jet activity, changes in absorption, thermal emission from the inner accretion disc, and variable accretion disc reflection. Little evidence for strong absorption is seen in the majority of the sample and single-component absorption can be excluded as the mechanism for most sources.

The COS-AGN survey: Revealing the nature of circum-galactic gas around hosts of active galactic nuclei

NASA Astrophysics Data System (ADS)

Berg, Trystyn A. M.; Ellison, Sara L.; Tumlinson, Jason; Oppenheimer, Benjamin D.; Horton, Ryan; Bordoloi, Rongmon; Schaye, Joop

2018-04-01

Active galactic nuclei (AGN) are thought to play a critical role in shaping galaxies, but their effect on the circumgalactic medium (CGM) is not well studied. We present results from the COS-AGN survey: 19 quasar sightlines that probe the CGM of 20 optically-selected AGN host galaxies with impact parameters 80 <ρimp<300 kpc. Absorption lines from a variety of species are measured and compared to a stellar mass and impact parameter matched sample of sightlines through non-AGN galaxies. Amongst the observed species in the COS-AGN sample (Lyα, Cii , Siii , Siiii , Civ , Siiv , Nv ), only Lyα shows a high covering fraction (94^{+6}_{-23}% for rest-frame equivalent widths EW≥124 mÅ) whilst many of the metal ions are not detected in individual sightlines. A sightline-by-sightline comparison between COS-AGN and the control sample yields no significant difference in EW distribution. However, stacked spectra of the COS-AGN and control samples show significant (>3σ) enhancements in the EW of both Siiii And Lyα at impact parameters >164 kpc by a factor of +0.45 ± 0.05 dex and >+0.75 dex respectively. The lack of detections of both high-ionization species near the AGN and strong kinematic offsets between the absorption systemic galaxy redshifts indicates that neither the AGN's ionization nor its outflows are the origin of these differences. Instead, we suggest the observed differences could result from either AGN hosts residing in haloes with intrinsically distinct gas properties, or that their CGM has been affected by a previous event, such as a starburst, which may also have fuelled the nuclear activity.

Quantifying the AGN-driven outflows in ULIRGs (QUADROS) II: evidence for compact outflow regions from HST [OIII] imaging observations

NASA Astrophysics Data System (ADS)

Tadhunter, C.; Zaurín, J. Rodríguez; Rose, M.; Spence, R. A. W.; Batcheldor, D.; Berg, M. A.; Ramos Almeida, C.; Spoon, H. W. W.; Sparks, W.; Chiaberge, M.

2018-05-01

The true importance of the warm, AGN-driven outflows for the evolution of galaxies remains uncertain. Measurements of the radial extents of the outflows are key for quantifying their masses and kinetic powers, and also establishing whether the AGN outflows are galaxy-wide. Therefore, as part of a larger project to investigate the significance of warm, AGN-driven outflows in the most rapidly evolving galaxies in the local universe, here we present deep Hubble Space Telescope (HST) narrow-band [OIII]λ5007 observations of a complete sample of 8 nearby ULIRGs with optical AGN nuclei. Combined with the complementary information provided by our ground-based spectroscopy, the HST images show that the warm gas outflows are relatively compact for most of the objects in the sample: in three objects the outflow regions are barely resolved at the resolution of HST (0.065 < R[OIII] < 0.12 kpc); in a further four cases the outflows are spatially resolved but with flux weighted mean radii in the range 0.65 < R[OIII] < 1.2 kpc; and in only one object (Mrk273) is there clear evidence for a more extended outflow, with a maximum extent of R[OIII] ˜ 5 kpc. Overall, our observations show little evidence for the galaxy-wide outflows predicted by some models of AGN feedback.

The 60 Month All-Sky Burst Alert Telescope Survey of Active Galactic Nucleus and the Anisotropy of Nearby AGNs

NASA Technical Reports Server (NTRS)

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..