bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cosmological Evolution of X-ray Selected AGNs and Synthesis of the X-ray Background
Authors: Ueda Yoshihiro , Akiyama Masayuki , Hasinger Günther , Miyaji Takamitsu , Watson Michael G. 
Published: July 2014

AbstractX-ray surveys provide us with one of the least biased samples of Active Galactic Nuclei (AGNs) against obscuration. Here we present the most up-to-date AGN X-ray luminosity function (XLF) and absorption function over the redshift range from 0 to 5, using the largest, highly complete sample ever available obtained from surveys of various depth, depth, and energy bands. We utilize a maximum likelihood method to reproduce the count-rate versus redshift distribution for each survey, by taking into account the evolution of the absorbed fraction, contribution from Compton-thick AGNs, and AGN broad band X-ray spectra including reflection components from tori based on the luminosity and redshift dependent unified scheme. We find that the shape of the XLF at z ~ 1–3 is significantly different from that in the local universe, for which the luminosity dependent density evolution (LDDE) model gives the best description. These results establish the standard population synthesis model of the X-Ray Background (XRB), which well reproduces the source counts in both soft and hard bands, the observed fractions of Compton-thick AGNs, and the spectrum of the XRB.
Gamma-ray emitting narrow-line Seyfert 1 galaxies. New discoveries and open questions
Authors: D'Ammando F. , Orienti M. , Finke J. , Larsson J. , Giroletti M. 
Published: July 2014

AbstractThe discovery of γ-ray emission from 5 radio-loud narrow-line Seyfert 1 galaxies revealed the presence of a possible emerging third class of AGNs with relativistic jets, in addition to blazars and radio galaxies. The existence of relativistic jets also in this subclass of Seyfert galaxies opened an unexplored research space for our knowledge of the radio-loud AGNs. Here, we discuss the radio-to-γ-rays properties of the γ-ray emitting narrow-line Seyfert 1 galaxies, also in comparison with the blazar scenario.
Compton thick AGN in Chandra sureys
Authors: Brightman Murray , Nandra Kirpal 
Published: July 2014

AbstractWe 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, NH > 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.
Study of a homogeneous X-ray selected AGN sample
Authors: Paronyan Gurgen M. , Mickaelian Areg M. , Abrahamyan Hayk V. 
Published: July 2014

AbstractBased on optical identifications of ROSAT sources, we have created a large homogeneous catalog of X-ray selected AGN. The Hamburg-RASS Catalog (HRC) and Byurakan-Hamburg-RASS Catalog (BHRC) made up on the basis of optical identification of X-ray sources from ROSAT Bright Source (BSC) and Faint Source (FSC) catalogues, respectively, have been used. These identiifcations were based on low-dispersion spectra of Hamburg Quasar Survey (HQS). As a result, a new large sample of X-ray selected AGN has been compiled containing 4253 sources with photon count rate CR > 0.04 ct/s in the area with galactic latitudes |b|>20 and declinations δ>0. All these sources are classified as AGN or candidate AGN. We have carried out multiwavelength studies in several wavelength ranges (X-ray, optical, radio). Catalogues that more or less guarantee the completeness condition (all-sky or large area surveys) were used. A number of erroneous classifications were found (some AGN had been classified as stars or galaxies); 1024 and 59 from HRC and BHRC, respectively. Out of 4253 sources, 3352 are spectroscopically confirmed AGN (given in Veron-Cetty & Veron and Roma Blazar catalogs), and the rest 901 are candidate AGN. For 210 of them spectra are available in SDSS DR9, and the results of their classification are given in another paper. We calculated absolute magnitudes, fluxes, improved coordinates and redshifts. An attempt is made to find a connection between the radiation fluxes in different bands for different types of sources, and identify their typical characteristics, thus confirming candidate AGN and in some cases finding new ones.
Luminosity Correlations, Luminosity Evolutions, and Radio Loudness of AGNs from Multiwavelength Observations
Authors: Petrosian Vahe , Singal Jack , Stawarz Lukasz 
Published: July 2014

AbstractThe dichotomy of jet dominated versus accretion disk dominated AGNs or “radio-loud” vs “radio-quiet” quasars can be investigated by a simultaneous determination of the relative shape and evolution of the radio and optical luminosity functions, and the distribution of the radio loudness R defined as the ratio of radio to optical luminosities. This can be done from a multivariate data set containing observed fluxes, redshift, spectra, etc. We emphasize that when dealing with a multivariate data set it is imperative to first determine the true correlations, not those introduced by the observational selection effects, among the variables (e.g. Luminosity-luminosity, redshift-luminosity) before obtaining the individual distributions of the variables (e.g. Luminosity functions and density evolution). We use data from several sources including the SDSS (Data Release 7) and FIRST radio catalogs, with well defined optical and radio flux limits, and employ the non-parametric methods developed by Efron and Petrosian, designed to obtain unbiased correlations, distributions and evolution with redshift from data truncated due to observational biases. We determine the density and the luminosity evolutions in both wavebands, which shows significantly higher radio than optical luminosity evolution. From these we obtain true distribution of the radio loudness parameter which shows no sign of bi-modality and indicates that quasars were more radio loud at earlier epochs.
ALMA: HI and He+ Lines and Dust in Starbursts, AGN and High-z Galaxies
Authors: Scoville Nick 
Published: July 2014

AbstractWe describe preliminary results for two ALMA projects – 1) imaging the HCN(4-3) line and H26α lines in Arp 220 and 2) measurements of the dust continuum in a sample of 107 high redshift galaxies to probe the evolution of the ISM masses. The HCN observations in Arp 220 at 1/2″ resolution provide the first high resolution imaging of the dense star forming gas in this prototypical ULIRG. The HCN is seen in two clearly delineated, counter-rotating disks. The H26α line is a definitive probe of the star formation rate in Arp 220, avoiding obscuration by dust and contamination by AGN luminosity contributions. In the second project, the remarkable continuum sensitivity of ALMA in Band 7 is used to measure the long wavelength Rayleigh-Jeans tail of the dust emission from a sample of 120 galaxies in COSMOS at z = 0.3 to 2.2, providing estimates for the dust masses and hence their ISM masses. This technique will enable measurements for hundreds of galaxies at high-z with observations of typically ~10 min per galaxy. This is in contrast to CO line imaging which typically requires a few hours per galaxy even with the sensitivity of ALMA. The dust-based mass estimates also avoid the uncertainties associated with the CO-to-H2 conversion factor.
Effectiveness of WISE colour-based selection techniques to uncover obscured AGN
Authors: Mateos S. 
Published: July 2014

AbstractWe present a highly reliable and efficient mid-infrared colour-based selection technique for luminous active galactic nuclei (AGN) using the Wide-field Infrared Survey Explorer (WISE) survey. Our technique is designed to identify objects with red mid-infrared power-law spectral energy distributions. We studied the dependency of our mid-infrared selection on the AGN intrinsic luminosity and the effectiveness of our technique to uncover obscured AGN missed in X-ray surveys. To do so we used two samples of luminous AGN independently selected in hard X-ray and optical surveys. We used the largest catalogue of 887 [OIII] λ5007-selected type 2 quasars (QSO2s) at z≲0.83 in the literature from the Sloan Digital Sky Survey (SDSS), and the 258 hard (>4.5 keV) X-ray-selected AGN from the Bright Ultrahard XMM-Newton Survey (BUXS). The effectiveness of our mid-infrared selection technique increases with the AGN luminosity. At high luminosities and at least up to z~1 our technique is very effective at identifying both Compton-thin and Compton-thick AGN.
Identifying Distant AGNs
Authors: Trouille Laura , Barger Amy , Tremonti Christy 
Published: July 2014

AbstractThe 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.
Wide-field observations in the SDSS Stripe 82 with the European VLBI Network
Authors: Cao H.-M. , Gurvits L. I. , Yang J. , Hong X.-Y. , Frey S. , Paragi Z. , Deller A. T. , Ivezić Ž. 
Published: July 2014

AbstractWe observed an area of sky located within the SDSS Stripe 82 field at 1.6 GHz with the European VLBI Network (EVN). There are fifteen mJy/sub-mJy radio sources within the primary beam of a typical 30-m class EVN radio telescope. Our aim was to obtain information on compact radio structures of all VLBI-detectable sources within this primary beam area. The source of particular interest is the recently identified radio quasar J222843.54+011032.2 (J2228+0110) at z = 5.95. The data correlation was performed at the EVN software correlator at JIVE (SFXC). Three targets (J2228+0110, J222851.45+011203.4, J222941.76+011428.5) were detected, all three with position offsets not exceeding the 3σ accuracy of the original low-resolution radio surveys. The detection rate of 20% is consistent with other wide-field VLBI experiments carried out recently (e.g. Middelberg et al. 2013). The project presented here demonstrates the ability of EVN in multiple-phase-centre experiments and paves the way for future large-scale EVN surveys of compact structures in extragalactic radio sources using the multiple-phase-centre VLBI technique.
An Updated Multi-Wavelength Radio and Optical Catalog of Quasars and Radio Galaxies
Authors: Kimball Amy E. , Ivezić Željko 
Published: July 2014

AbstractWe present a catalog of millions of radio sources, created by consolidating large-area radio and optical surveys GB6 (6cm), FIRST (20cm), NVSS (20cm), WENSS (92cm), VLSS (4m), and SDSS DR9 (optical). The region where all surveys overlap covers 3269 deg2 in the North Galactic Cap, and contains >160,000 20-cm sources, with about 12,000 detected in all five radio surveys and over one-third detected optically. Combining parameters from the sky surveys allows easy and efficient classification by radio and optical morphology and radio spectral index. The catalog is available at http://www.atnf.csiro.au/people/Amy.Kimball/radiocat.shtml.
The Chandra 3C Snapshot Surveys
Authors: Harris Daniel E. , Massaro Francesco 
Published: July 2014

AbstractThe Chandra X-ray Observatory is the only X-ray facility with sub arcsec resolution, permitting detailed studies of radio galaxies and quasars. We review a short list of projects contributing to our goal of obtaining Chandra observations of all 3C extragalactic sources. Radio source samples, unlike most surveys at other wavelengths, should be completely unbiased with respect to viewing angle: the radio lobes are sign posts indicating the location of AGN (obscured or unobscured nuclei). The X-ray data allow us to estimate excess absorption towards nuclei, to find new examples of X-ray emission from jet knots and hotspots, and to isolate sources in clusters of galaxies together with signatures of feedback (e.g. cavities in the ICM). This work is supported by NASA grants GO1-12125A and GO2-13115X.
A wide search of obscured Active Galactic Nuclei using XMM-Newton and WISE
Authors: Rovilos E. , Georgantopoulos I. , Akylas A. , Aird J. , Alexander D. M. , Comastri A. , Del Moro A. , Gandhi P. , Georgakakis A. , Harrison C. M. , Mullaney J. R. 
Published: July 2014

AbstractWe use the WISE all sky survey observations to look for counterparts of hard X-ray selected sources from the XMM-Newton-SDSS survey. We then measure the 12 μm luminosity of the AGN by decomposing their optical to infrared SEDs with a host and an AGN component and compare it to the X-ray luminosity and their expected intrinsic relation. This way we select 20 X-ray under-luminous heavily obscured candidates and examine their X-ray and optical properties in more detail. We find evidence for a Compton-thick nucleus for six sources, a number lower than what expected from X-ray background synthesis models, which shows the limitations of our method.
Imminent understanding of the structure of nearby AGN from IFUs
Authors: Davies Richard 
Published: July 2014

AbstractIntegral field spectroscopy provides us with immensely rich datasets about spatially resolved distributions and kinematics of emission and absorption lines. In this contribution I will describe some of the key insights that have been made about AGN using optical, near infrared, and far infrared IFUs. These encompass gas inflow and outflow mechanisms, and the relations between star formation, the torus, and accretion onto the black hole. Progress so far has largely relied on archetypal and small sets of objects. In the future, a more statistically robust approach will be required. I will end by discussing a number of issues that can easily confuse an emerging picture, and need to be borne in mind for such surveys.
FLASHLIGHT: Fluorescent Lyman-Alpha Survey of cosmic Hydrogen iLlumInated by hIGH-redshifT quasars.
Authors: Battaia Fabrizio Arrigoni , Hennawi J. F. , Cantalupo S. , Prochaska J. X. 
Published: July 2014

AbstractThe current galaxy formation paradigm postulates that a significant amount of gas accretes onto galaxies from the IGM in a cold T ~ 104K phase, and many have argued that this gas should be detectable in diffuse Lyα emission. However, so far, there are no convincing direct detections.We are conducting a deep (down to 1σ ~ 5 − 10 × 10−19 erg s−1 cm−2 arcsec−2) and the first statistical survey matching the Lyα line around radio-quiet quasars at z ~ 2. By taking advantage of the boost in fluorescent Lyα emission due to the ionizing radiation emitted by a luminous QSO that, like a flashlight, can illuminate the hydrogen in its vicinity, we will be able to constrain some of the properties of the gas sorrounding z ~ 2 QSOs. In particular, with this unique dataset, we can conduct the first deep statistical census of the size, morphology, luminosity, frequency, and covering factor of Lyα emission around QSOs.
AGN with faint broad line regions: Some ‘True’-Seyfert 2s might be Narrow Line Seyfert 1s
Authors: Valencia-S. Mónica , Busch G. , Smajić S. , Fazeli N. , Behroozian S. , Zuther J. , Fischer S. , Eckart A. 
Published: July 2014

AbstractThe intriguing existence of ‘True’-Seyfert 2s has opened a debate on the validity of the unified model of active galactic nuclei (AGN). These objects, also called ‘Naked’-AGN, seem to lack a broad line region. In some cases, their X-ray emission is unabsorbed, typical of Seyfert 1 galaxies, indicating a clear view toward the nucleus, but no broad lines are seen in the optical. In ‘True’-Seyfert 2s with higher column densities, observations of polarized light have failed to reveal the hidden broad emission. We performed high-resolution near-infrared integral-field observations of two ‘True’-Seyfert 2 candidates: IRAS 01072+4954 and NGC 7496. We found that the AGN in these sources might power very faint and narrow broad emission lines (FWHMbroad < 1500km s−1). Here, we discuss the properties of the broad components estimated from published X-ray and/or optical measurements and present their near-infrared candidate identification. Both galaxies host intermediate-mass black holes, with masses ~ 105−106 M⊙. Our results favor the unified model in the cases of high accretion rates, and stress the necessity of a multiwavelength approach to unveil the nature of ‘Naked’-AGN.
The origin of the IR emission of low-luminosity AGN
Authors: Mason R. E. , Almeida C. Ramos , Levenson N. A. , Nemmen R. , Herrero A. Alonso 
Published: July 2014

AbstractTo test recent suggestions that the infrared emission of low-luminosity AGN arises in a truncated thin accretion disk, we compare recent, high-resolution IR data with published SED model fits that include emission from the truncated disk. We also fit the data with clumpy torus and optically thin dust shell models. These comparisons suggest that dust can better account for the IR emission of the objects in question than can the truncated disk. That optically thin models give a good fit to the data may support a scenario in which the torus of the AGN unified model does not persist in low accretion rate AGN.
Powerful Molecular Outflows in Nearby Active Galaxies
Authors: Veilleux Sylvain , Meléndez Marcio ,   the SHINING Team
Published: July 2014

AbstractWe report the results from a systematic search for molecular (OH 119 μm) outflows with Herschel-PACS† in a sample of 43 nearby (z < 0.3) galaxy mergers, mostly ultraluminous infrared galaxies (ULIRGs) and QSOs. We find that the character of the OH feature (strength of the absorption relative to the emission) correlates with that of the 9.7-μm silicate feature, a measure of obscuration in ULIRGs. Unambiguous evidence for molecular outflows, based on the detection of OH absorption profiles with median velocities more blueshifted than −50 km s−1, is seen in 26 (70%) of the 37 OH-detected targets, suggesting a wide-angle (~ 145°) outflow geometry. Conversely, unambiguous evidence for molecular inflows, based on the detection of OH absorption profiles with median velocities more redshifted than +50 km s−1, is seen in only 4 objects, suggesting a planar or filamentary geometry for the inflowing gas. Terminal outflow velocities of ~ −1000 km s−1 are measured in several objects, but median outflow velocities are typically ~ −200 km s−1. While the outflow velocities show no statistically significant dependence on the star formation rate, they are distinctly more blueshifted among systems with large AGN fractions and luminosities [log (LAGN/L⊙) ≥ 11.8 ± 0.3]. The quasars in these systems play a dominant role in driving the molecular outflows. In contrast, the most AGN dominated systems, where OH is seen purely in emission, show relatively modest OH line widths, despite their large AGN luminosities, perhaps indicating that molecular outflows subside once the quasar has cleared a path through the obscuring material.
A correlation between star formation rate and average black hole accretion rate in star forming galaxies
Authors: Chen Chien-Ting J. , Hickox Ryan C. 
Published: July 2014

AbstractWe present the results of recent studies on the co-evolution of galaxies and the supermassive black holes (SMBHs) using Herschel far-infrared and Chandra X-ray observations in the Boötes survey region. For a sample of star-forming (SF) galaxies, we find a strong correlation between galactic star formation rate and the average SMBH accretion rate in SF galaxies. Recent studies have shown that star formation and AGN accretion are only weakly correlated for individual AGN, but this may be due to the short variability timescale of AGN relative to star formation. Averaging over the full AGN population yields a strong linear correlation between accretion and star formation, consistent with a simple picture in which the growth of SMBHs and their host galaxies are closely linked over galaxy evolution time scales.
Modeling the Structure of the Windy Torus in Quasars
Authors: Gallagher Sarah C. , Abado Mathew M. , Everett John E. 
Published: July 2014

AbstractMass ejection in the form of winds or jets appears to be as fundamental to quasar activity as accretion. A convincing argument for radiation pressure driving this ionized outflow can be made within the dust sublimation radius. Beyond, radiation pressure is even more ubiquitous, as high energy photons from the central engine can now push on dust grains. This physics underlies the dusty-wind model for the putative obscuring torus. Specifically, the dusty wind in our model is first launched from the outer accretion disk as a magneto-centrifugal wind and then accelerated and shaped by radiation pressure from the central continuum. Such a wind can plausibly account for both the necessary obscuring medium to explain the observed ratio of broad-to-narrow-line quasars and the mid-infrared emission commonly seen in quasar spectral energy distributions.
Close pairs of galaxies with different activity levels
Authors: Nazaryan T. A. , Petrosian A. R. , Hakobyan A. A. , McLean B. J. , Kunth D. 
Published: July 2014

AbstractWe selected and studied 180 pairs with d V < 800 km s−1 and Dp < 60 kpc containing Markarian (MRK) galaxies to investigate the dependence of galaxies integral parameters, star-formation (SF) and active galactic nuclei (AGN) properties on kinematics of pairs, their structure and large-scale environments. Projected radial separation Dp and perturbation level P are better measures of interaction strength than dV. The latter correlates with the density of large-scale environment and with the morphologies of galaxies. Both galaxies in a pair are of the same nature, the only difference is that MRK galaxies are usually brighter than their neighbors. Specific star formation rates (SSFR) of galaxies in pairs with smaller Dp or d V is in average 0.5 dex higher than that of galaxies in pairs with larger Dp or d V. Closeness of a neighbor with the same and later morphological type increases the SSFR, while earlier-type neighbors do not increase SSFR. Major interactions/mergers trigger SF and AGN more effectively than minor ones. The fraction of AGNs is higher in more perturbed pairs and pairs with smaller Dp. AGNs typically are in stronger interacting systems than star-forming and passive galaxies. There are correlations of both SSFRs and spectral properties of nuclei between pair members.
Host galaxy properties of radio selected AGN
Authors: Bonzini M. , Mainieri V. , Padovani P. , Kellermann K. I. , Miller N. , Rosati P. , Tozzi P. , Vattakunnel S. 
Published: July 2014

AbstractWith the goal of investigating the link between black hole (BH) and star formation (SF) activity, we study a deep sample of radio selected star forming galaxies (SFGs) and active galactic nuclei (AGNs). Using a multi-wavelength approach we characterize their host galaxies properties (stellar masses, optical colors, and morphology). Moreover, comparing the star formation rate derived from the radio and far-infrared luminosity, we found evidences that the main contribution to the radio emission in the radio-quiet AGNs is star-formation activity in their host galaxy.