نتایج جستجو برای: agn
تعداد نتایج: 7335 فیلتر نتایج به سال:
We analyse the relation between AGN host properties and large scale environment for a representative red and blue AGN host galaxy sample selected from the DR4 SDSS. A comparison is made with two carefully constructed control samples of non-active galaxies, covering the same redshift range and color baseline. The cross-correlation functions show that the density distribution of neighbours is alm...
We separate the extragalactic radio source population above∼50μJy into active galactic nuclei (AGN) and star-forming sources. The primary method of our approach is to fit the infrared spectral energy distributions (SEDs), constructed using Spitzer/IRAC and MIPS and Herschel/SPIRE photometry, of 380 radio sources in the Extended Chandra Deep Field-South. From the fitted SEDs, we determine the re...
The role of star-formation driven outflows in the obscuration of the central source in the Active Galactic Nuclei (AGN) is discussed. The outflow from a sub-parsec scale accretion disc is numerically modelled for parameters appropriate to the Galactic Centre. The resulting obscuration pattern is very patchy, with some lines of sight becoming optically thick to Thomson scattering. A fixed observ...
We review the continuum emission of Active Galactic Nuclei (AGN) over the entire electromagnetic spectrum. After a brief historical introduction, we describe the main spectral properties of unobscured AGN, discussing the selection biases which prevent us from having a complete view of the AGN population in the universe, and trying to build an updated spectral energy distribution of optically se...
We present high spatial resolution ultraviolet and optical spectroscopy, obtained using the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope, of nuclear structures within four 'warm' Ultraluminous Infrared Galaxies (ULIRGs). We find an AGN in at least three, and probably all four of our sample, hosted in a compact, optically luminous 'knot'. In three cases these knots we...
Spectra have been obtained with the Infrared Spectrograph (IRS) on the Spitzer Space Telescope for 20 sources in the Lockman Hole field of the SWIRE survey. The sample is divided between sources with indicators of an obscured AGN, based primarily on X-ray detections of optically-faint sources, and sources with indicators of a starburst, based on optical and near-infrared spectral energy distrib...
The sensitivity of a search for sources of TeV neutrinos can be improved by grouping potential sources together into generic classes in a procedure that is known as source stacking. In this paper, we define catalogs of Active Galactic Nuclei (AGN) and use them to perform a source stacking analysis. The grouping of AGN into classes is done in two steps: first, AGN classes are defined, then, sour...
The role of stars and starbursts in AGN has been a recurring issue for nearly as long as AGN have been recognized as hosts of interesting phenomena. The heated “starburst versus monster” controversy of the 80’s and 90’s was gradually replaced by “starburst plus monster” studies, as observational work in the past decade has firmly established that accretion onto a super-massive black-hole and st...
The Two Micron All Sky Survey (2MASS) provides an unprecedented, uniform photometric data set for large samples of AGN discovered at other wavelengths, and also forms the basis to search for previously unknown, obscured AGN. We present the results of a highly efficient near infrared color-based AGN survey using 2MASS that has already discovered 485 new, red AGN and QSOs. The extrapolated surfac...
Departments of *Paediatrics and †Microbiology, University of Ilorin Teaching Hospital, P.M.B.1459, Ilorin, Nigeria. Correspondence: Dr.O.T.Adedoyin, P.O.Box 6292, Ilorin, E-mail; [email protected] Phone; 0803 549 1520 Abbreviations: AGN, Acute Glomerulonephritis; NS, Nephrotic Syndrome; UTI, Urinary Tract Infection. ABSTRACT BACKGROUND: The occurrence of urinary tract infection (UTI) in chil...
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