bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unveiling the high-frequency radio source population with the AT20G survey
Authors: Mahony Elizabeth K. 
Published: July 2014

AbstractUntil recently, the radio sky above 5 GHz was relatively unexplored. This has changed with the completion of the Australia Telescope 20 GHz survey (AT20G; Murphy et al., 2010); a blind survey of the southern sky down to a limiting flux density of 40 mJy. The AT20G survey provides by far the largest and most complete sample of high-frequency radio sources yet obtained, offering new insights into the nature of the high-frequency active galaxy population. Whilst the radio data provides a unique sample of objects, these data alone are insufficient to completely constrain models of radio source properties and the evolution of radio galaxies. Complementary multiwavelength data is vital in understanding the physical properties of the central black hole.In this talk I will provide a brief overview of the AT20G survey, followed by a discussion of the multiwavelength properties of the high-frequency source population. In particular, I will focus on the optical properties of AT20G sources, which are very different to those of a low-frequency selected sample, along with the gamma-ray properties where we find a correlation between high-frequency radio flux density and gamma-ray flux density. By studying the multiwavelength properties of a large sample of high-frequency radio sources we gain a unique perspective on the inner dynamics of some of the most active AGN.
The evolution of activity in galaxies fromz=0.45 to the present time
Authors: Stasińska Grażyna , Costa-Duarte M. V. , Vale Asari N. 
Published: July 2014

AbstractWe use spectra from the SDSS to study the signatures of nuclear activity over cosmic time, dividing the samples in redshift and mass bins, and using various diagnostic diagrams. A redshift evolution clearly emerges from the analysis of our diagrams.
The sharpest view of the local AGN population at mid-infrared wavelengths
Authors: Asmus Daniel , Hönig Sebastian F. , Gandhi Poshak , Smette Alain , Duschl Wolfgang J. 
Published: July 2014

AbstractWe present the largest mid-infrared (MIR) atlas of active galactic nuclei at sub-arcsec spatial scales containing 253 objects with a median redshift of 0.016. It comprises all available ground-based high-angular resolution MIR observations performed to date with 8-meter class telescopes and includes 895 photometric measurements. All types of AGN are present in the atlas, which also includes 80 per cent of the 9-month BAT AGN sample. Therefore, this atlas and its subsamples are very well-suited for AGN unification studies. A first application of the atlas is the extension of the MIR–X-ray luminosity correlation for AGN.
Fitting Spectral Energy Distributions of AGN A Markov Chain Monte Carlo Approach
Authors: Rivera Gabriela Calistro , Lusso Elisabeta , Hennawi Joseph F. , Hogg David W. 
Published: July 2014

AbstractWe present AGNfitter: a Markov Chain Monte Carlo algorithm developed to fit the spectral energy distributions (SEDs) of active galactic nuclei (AGN) with different physical models of AGN components. This code is well suited to determine in a robust way multiple parameters and their uncertainties, which quantify the physical processes responsible for the panchromatic nature of active galaxies and quasars. We describe the technicalities of the code and test its capabilities in the context of X-ray selected obscured AGN using multiwavelength data from the XMM-COSMOS survey.
Chandra Observation of the AKARI NEP Deep Field
Authors: Miyaji Takamitsu , Krumpe M. , Brunner H. ,   AKARI NEP Deep Survey Team
Published: July 2014

AbstractThe AKARI NEP Deep Field Survey is an international multiwavelength survey over 0.4 deg2 of the sky. This is the deepest survey made by the InfraRed Camera (IRC) of the infrared astronomical satellite AKARI with 9 filters continuously covering the 2-25 μm range. This has been supplemented by other ground-based and space multiwavelength data ranging from X-ray (Chandra), UV (GALEX), Optical-NIR (Subaru Sprime-cam, CFHT/WIRCAM, CFHT/Megacam, KPNO Flamningos among others for imagings as well as Keck Diemos, Subaru Focas, Subaru FMOS, WIYN Hydra, and GTC OSIRIS for spectra), far-infrared (Herschel) and radio (WSRT and e-Merlin). The uniqueness of the field lies in the availability of four filters between 9-18 μm, which fall into the Spitzer gap between the IRAC and MIPS instruments. This made this field one of the deepest at ~ 15 μm and the deepest among those with similar solid angles. This enabled us to make sensitive MIR detection of AGN candidates around z ~ 1. The MIR selection is based on hot dust emission in the AGN torus and is efficient in detecting highly obscured Compton-thick AGN population. A number of team members have worked (e.g. Hanami et al. 2012) or are working on a catalog of AGN candidates in this field. In this presentation, we report the results of the Chandra observations on this field. The field was covered by 15 overlapping Chandra ACIS-I observations (including our own and from archive) with a total exposure of 310 ks, detecting ~ 500 X-ray sources. We explain our improved source detection procedure for highly overlapped Chandra images and results. We utilize the stacking analysis (both in the observed and rest-frame) of the MIR AGN candidates that are not detected individually. The stacking analysis is expected to detect the summed X-ray flux from scattered components and Fe-lines. The results are discussed in terms of quantifying the Compton-thick populations at z ~ 1.
Further determination of interband lags between variations in B, V, R, and I bands in active galactic nuclei
Authors: Sergeev S. G. 
Published: July 2014

AbstractNew estimates of the interband lags between variations in the B band and variations in the V, R, and I bands for three active galactic nuclei (AGNs) are present. In contrast to the previous study by Sergeev et al. (2005), the effect of the contribution of the broad lines to the bands is taken into account.
Multiwavelength Observations of 6 FSRQ in 2008–2012
Authors: Troitskiy I. S. , Morozova D. A. , Jorstad S. G. , Larionov V. M. , Marscher A. P. , Agudo I. , Blinov D. A. , Smith P. S. 
Published: July 2014

AbstractWe present results of 4 years of VLBA monitoring along with γ-ray and optical R-band photometric observations of 6 blazars (0420-014, 1156+295, 1222+216, PKS 1510-089, 1633+382 and CTA 102). We have analyzed total intensity images obtained with the VLBA at 43 GHz and investigated kinematic evolution of the pc-scale jets of the sources. For all sources we compare flux variations in the VLBI core and bright superluminal knots with γ-ray and optical light curves. The majority of γ-ray flares are coincident with the appearance of a new superluminal knot and/or a flare in the millimeter-wave core and at optical wavelengths. These results support the conclusion that for many flares in blazars the region of the enhanced γ-ray and optical emission is located in the vicinity or downstream of the mm-wave VLBI core.
A New Look at Quasar Accretion Disks
Authors: Capellupo Daniel M. , Netzer Hagai , Lira Paulina , Trakhtenbrot Benny , Mejía Julián 
Published: July 2014

AbstractThe physics of active black holes (BHs) is governed by three key parameters: their mass, spin, and accretion rate. Understanding the cosmic evolution of these parameters is crucial for tracing back the growth of the BHs to the epoch of their formation. We have selected a unique AGN sample, in a narrow redshift range around z = 1.55, based on both BH mass and Eddingtion ratio, and we observed them with the X-Shooter instrument on the VLT, covering the rest wavelength range ~1200 to 9800 Å. This wide wavelength range allows us to study, simultaneously, more emission lines (i.e., CIV 1550 Å through H-alpha), and a larger portion of the global AGN SED, than any previous studies. We currently have a sample of 30 quasars already observed and spanning BH masses from ~108to 109Msolarand Eddington ratio from ~0.03 to 0.7. We focus here on our first science goal, comparing the observed AGN SED to thin accretion disk models in order to identify the origin of the SED. We also discuss the unique capability of this sample to identify any emission-line profile dependencies on BH mass and the Eddington ratio, and to compare mass determination methods based on four different emission-line profiles (Hα, Hβ, MgII 2800 Å, and CIV 1550 Å).
X-ray emission from hot accretion flows
Authors: Niedźwiecki Andrzej , Xie Fu-Guo , Stȩpnik Agnieszka 
Published: July 2014

AbstractRadiatively inefficient, hot accretion flows are widely considered as a relevant accretion mode in low-luminosity AGNs. We study spectral formation in such flows using a refined model with a fully general relativistic description of both the radiative (leptonic and hadronic) and hydrodynamic processes, as well as with an exact treatment of global Comptonization. We find that the X-ray spectral index–Eddington ratio anticorrelation as well as the cut-off energy measured in the best-studied objects favor accretion flows with rather strong magnetic field and with a weak direct heating of electrons. Furthermore, they require a much stronger source of seed photons than considered in previous studies. The nonthermal synchrotron radiation of relativistic electrons seems to be the most likely process capable of providing a sufficient flux of seed photons. Hadronic processes, which should occur due to basic properties of hot flows, provide an attractive explanation for the origin of such electrons.
High Signal-to-Noise Ratio Mid-Infrared Quasar Spectral Templates
Authors: Hill Allison R. , Gallagher S. C. , Deo R. P. , Peeters E. , Richards Gordon T. 
Published: July 2014

AbstractMid-infrared (MIR) quasar spectra exhibit a suite of emission features including high ionization coronal lines from the narrow line region (NLR) illuminated by the ionizing continuum, and hot dust features from grains, as well as polycyclic aromatic hydrocarbons (PAH) features from star formation in the host galaxy. Few features are detected in most spectra because of typically low signal-to-noise ratio (S/N) data. By generating spectral composites in three different luminosity bins from over 180 Spitzer Ifnfrared Spectrograph (IRS) observations, we boost the S/N and reveal important features in the complex spectra. We detect high-ionization, forbidden emission lines in all templates, PAH features in all but the most luminous objects, and broad silicate and graphite features in emission whose strength increases relative to the continuum with luminosity. We find that the intrinsic quasar spectrum for all luminosity templates is consistent, and the differences in the spectra can be explained by host galaxy contamination in the lower luminosity templates. We also posit that star formation may be active in most quasar host galaxies, but the spectral features of star formation are only detectable if the quasar is faint.
Through the kaleidoscope: star formation the host galaxies of radio-AGN
Authors: Karouzos Marios , Im Myungshin , Trichas Markos , Goto Tomo , Malkan Matt , Ruiz Angel , Jeon Yiseul ,   the AKARI NEP team
Published: July 2014

AbstractThere exist strong evidence supporting the co-evolution of central supermassive black holes and their host galaxies; however it is still under debate how such a relation comes about and whether it is relevant for all or only a subset of galaxies. A rich multi-wavelength dataset is available for the North Ecliptic Pole field, most notably surveyed by the AKARI infrared space telescope. We investigate the star-formation properties of the host galaxies of radio-AGN together with the radio feedback mechanism, potentially responsible for the eventual quenching of star formation. Using broadband SED modelling, the nuclear and host galaxy components of these sources are studied as a function of their radio luminosity. Here we present results concerning the AGN content of the radio sources in this field, while offering evidence supporting a “maintenance” type of feedback from powerful radio-jets.
Evidence of AGN-driven Outflows in Young Radio Quasars Selected from the Wide-field Infrared Survey Explorer
Authors: Kim Minjin , Ho Luis C. , Lonsdale Carol J. , Lacy Mark , Blain Andrew W. , Kimball Amy E. 
Published: July 2014

AbstractWe present near-infrared spectra of young radio quasars selected by cross-correlating the Wide-field Infrared Survey Explorer (WISE) all-sky survey catalog with the radio catalog [Faint Images of the Radio Sky at Twenty cm (FIRST) and NRAO VLA Sky Survey (NVSS)]. The objects have typical redshifts of z ≈ 2 and [O III] luminosities of 107 erg s−1 comparable to those of luminous quasars. The observed flux ratios of narrow emission lines indicate that these objects appear to be powered by active galactic nuclei. The [O III] line is broad, with full width at half maximum ~1300 to 2100 km s−1, significantly larger than that of ordinary quasars. These large line widths might be explained by jet-induced outflows.
Supernovae in paired galaxies
Authors: Nazaryan T. A. , Petrosian A. R. , Hakobyan A. A. , Adibekyan V. Zh. , Kunth D. , Mamon G. A. , Turatto M. , Aramyan L. S. 
Published: July 2014

AbstractWe investigate the influence of close neighbor galaxies on the properties of supernovae (SNe) and their host galaxies using 56 SNe located in pairs of galaxies with different levels of star formation (SF) and nuclear activity. The mean distance of type II SNe from nuclei of hosts is greater by about a factor of 2 than that of type Ibc SNe. The distributions and mean distances of SNe are consistent with previous results compiled with the larger sample. For the first time it is shown that SNe Ibc are located in pairs with significantly smaller difference of radial velocities between components than pairs containing SNe Ia and II. We consider this as a result of higher star formation rate (SFR) of these closer systems of galaxies.
AGN and Starbursts in Dusty Galaxy Mergers: Insights from the Great Observatories All-sky LIRG Survey
Authors: Mazzarella Joseph M. ,   the GOALS Team
Published: July 2014

AbstractThe Great Observatories All-sky LIRG Survey (GOALS) is combining imaging and spectroscopic data from the Herschel, Spitzer, Hubble, GALEX, Chandra, and XMM-Newton space telescopes augmented with extensive ground-based observations in a multiwavelength study of approximately 180 Luminous Infrared Galaxies (LIRGs) and 20 Ultraluminous Infrared Galaxies (ULIRGs) that comprise a statistically complete subset of the 60μm-selected IRAS Revised Bright Galaxy Sample. The objects span the full range of galaxy environments (giant isolated spirals, wide and close pairs, minor and major mergers, merger remnants) and nuclear activity types (Seyfert 1, Seyfert 2, LINER, starburst/HII), with proportions that depend strongly on the total infrared luminosity. I will review the science motivations and present highlights of recent results selected from over 25 peer-reviewed journal articles published recently by the GOALS Team. Statistical investigations include detection of high-ionization Fe K emission indicative of deeply embedded AGN, comparison of UV and far-IR properties, investigations of the fraction of extended emission as a function of wavelength derived from mid-IR spectroscopy, mid-IR spectral diagnostics and spectral energy distributions revealing the relative contributions of AGN and starbursts to powering the bolometric luminosity, and quantitative structure analyses that delineate the evolution of stellar bars and nuclear stellar cusps during the merger process. Multiwavelength dissections of individual systems have unveiled large populations of young star clusters and heavily obscured AGN in early-stage (II Zw 96), intermediate-stage (Mrk 266, Mrk 273), and late-stage (NGC 2623, IC 883) mergers. A recently published study that matches numerical simulations to the observed morphology and gas kinematics in mergers has placed four systems on a timeline spanning 175-260 million years after their first passages, and modeling of additional (U)LIRGs is underway. A very brief description of ongoing work with Herschel and ALMA will be given. The talk will conclude with a discussion of the demographics of dual AGN (kpc-scale orbits) in the GOALS sample, including the difficulty of their detection and confirmation, a proposed sequence representing a progression from dual AGN to binary AGNs (sub-pc scale orbits), and implications for the scarcity of confirmed binary QSOs in recent large surveys. Grant support from NASA is gratefully acknowledged.
Galaxies with Binary Nuclei
Authors: Terzian Yervant , Khachikian Edward 
Published: July 2014

AbstractIt is known that among active galaxies (AG) with strong emission lines (UV-galaxies, Sy1 and Sy2, Markarian and Kazarian galaxies, radio-galaxies, QSOs host galaxies and so on) there is a large percentage of objects with double and multiple (or complex) nuclei. The common sizes of these nuclei are of the order of a few hundred parsecs or kiloparsecs. We shall discuss the results of morphological and spectroscopic observations of a number of “active galaxies” carried out with the 5m Palomar telescope, 2.6m telescope of Ambartsumian Byurakan Astrophysical Observatory, 6m telescope of Special Astrophysical Observatory in Russia, and newer Hubble Space Telescope data.
Study of Starburst/Activity/Interaction Phenomena based on the Multiple Byurakan-IRAS Galaxies
Authors: Harutyunyan Gohar S. , Mickaelian Areg M. 
Published: July 2014

AbstractThe Byurakan-IRAS Galaxy (BIG) sample is the result of optical identifications of IRAS PSC sources at high-galactic latitudes using the First Byurakan Survey (FBS) low-dispersion spectra. Among the 1178 objects most are spiral galaxies and many have been proved to be AGN and starburst by spectroscopic observations, as well as there is a number of ULIRGs among these objects. BIG objects contain galaxy pairs, multiples, and small groups that are subject for study on the matter of the real IR-emitter in these systems. Given that these objects are powerful IR sources, they are considered as young systems indicating high rate of evolution and starburst activity exceeding 100 Mo/yr. Spectroscopic observations show that all these systems are physical ones and we were able to measure the mutual distances and sizes for all components. Cross-correlations with the recent more accurate IR catalogues, such as 2MASS and WISE, as well as radio ones (NVSS, FIRST), provided accurate coordinates of the IR source and possibility to find the individual galaxy responsible for the IR. However, in almost half of the cases, IR position indicates the intermediate region between the components, which means that it comes from the system as a whole. Some more MW data have been matched to IR and radio to have an overall understanding on these systems. Given that these systems are mostly interacting/merging ones often containing AGN and most of them may be considered as powerful starbursts, it is possible to study starburst/activity/interaction phenomena and their interrelationship.
Hour-timescale profile variations in the broad Balmer lines of the Seyfert galaxy Hour-timescale profile variations in the broad Balmer lines of the Seyfert galaxy Markarian 6
Authors: Asatrian Norayr S. 
Published: July 2014

AbstractPart of results of the multi-epoch intranight optical spectroscopic monitoring of the Markarian 6 nucleus carried out at the telescopes of 6-m of the Special Astrophysical Observatory (Russia), 2.6-m of the Byurakan Astrophysical Observatory (Armenia) and 2-m of the Tautenburg Observatory (Germany) is presented.Observations were made in 1979, 1986, 1988-1991 and 2007-2009 during a total of 33 nights with an average sampling rate of 4 spectra per night. TV-scanner and long-slit spectrographs equipped with Image Tube and CCD detector arrays were used. Altogether we analyzed 110 Hβ and 58 Hα region spectra to search for intranight variability in the broad hydrogen emission line profiles. The typical spectral resolutions were 4 Å for scanner spectra, 6 Å for photographic spectra, and 5 Å and 10 Å for CCD spectra. The S/N ratio at the continuum level near the Hβ and Hα lines was in the range 15–50.The purpose of the search was to look for the characteristic variability signatures of different kinematical models of the broad emission-line region. We considered the centering and guiding errors which can result in differences between spectra.We found variations in the broad Balmer line difference profiles on time scale of hour with the level of significance of 3.6 σ to 5.0 σ. Variations take the form of narrow, small bumps located at the blue and red sides or only at the blue side of the lines. In the intermediate level of broad line flux, the Hβ and Hα profiles show fine structure. Detected profile changes occurred at the same radial velocity shifts as the details in the fine structure.The variability is at least 2 orders of magnitude more rapid than any observed for broad Balmer line profiles in AGNs that we are aware of in the literature.Discovered extremely rapid line-profile variability may be associated with reverberation effects. Two-sided profile changes may indicate the response of circularly rotating hydrogen clouds in the BLR to a light pulse from a central source. One-sided profile variations may be attributed to a response of a non-disk component: the subarcsec scale region of the jet.
FeLoBAL Outflow Variability Constraints from Multi-Year Observations
Authors: McGraw Sean M. , Shields Joseph C. , Hamann Frederick W. , Capellupo Daniel M. , Gallagher Sarah C. , Brandt William N. 
Published: July 2014

AbstractThe physical properties and dynamical behavior of Broad Absorption Line (BAL) outflows are crucial themes in understanding the connections between galactic centers and their hosts. FeLoBALs (identified with the presence of low-ionization Fe II BALs) are a peculiar class of quasar outflows that constitute ~ 1% of the BAL population. With their large column densities and apparent outflow kinetic luminosities, FeLoBALs appear to be exceptionally powerful and are strong candidates for feedback in galaxy evolution. We conducted variability studies of 12 FeLoBAL quasars with emission redshifts 0.69 ≤ z ≤ 1.93, spanning both weekly and multi-year timescales in the quasar's rest frame. We detected absorption-line variability from low-ionization species (Fe II, Mg II) in four of our objects, with which we established a representative upper limit for the distance of the absorber from the supermassive black hole (SMBH) to be ~20 parsecs. Our goals are to understand the mechanisms producing the variability (e.g. ionization changes or gas traversing our line of sight) and place new constraints on the locations, structure, and kinetic energies of the outflows.