Quasars and Their Nature a Modern Analysis

Total Page:16

File Type:pdf, Size:1020Kb

Quasars and Their Nature a Modern Analysis Quasars and their Nature A Modern Analysis Thomas Madigan June 7, 2010 Page 1 Quasars and their Nature A Modern Analysis Table of Contents Preface.......................................................................................................................................................................................... 4 First Thoughts .......................................................................................................................................................................... 4 Mount Stromlo ......................................................................................................................................................................... 4 Introduction.................................................................................................................................................................................. 5 Redshift, Detection and the Origins of Distance Determination.................................................................................................. 5 Naming and Statistics............................................................................................................................................................... 5 Cepheid Variables.................................................................................................................................................................... 5 Red Shift .................................................................................................................................................................................. 6 The Hubble Constant................................................................................................................................................................ 6 Bell Labs, Karl Jansky and Penzias and Wilson ...................................................................................................................... 7 Cambridge................................................................................................................................................................................ 8 Jocelyn Bell, Anthony Hewish and the Cambridge Radio Astronomy Group ......................................................................... 8 Hubble, Slipher and Initial Ideas.............................................................................................................................................. 9 Spectra...................................................................................................................................................................................... 9 Progress Towards a Modern Understanding .............................................................................................................................. 10 ALMA.................................................................................................................................................................................... 10 Southern Hemisphere Observations....................................................................................................................................... 11 Electromagnetic Radiation and its Wave – Particle Duality .................................................................................................. 12 Quasar Redshifts and the Expansion of the Universe ............................................................................................................ 13 Quasar Luminosities............................................................................................................................................................... 15 Properties and Characteristics.................................................................................................................................................... 15 True Nature ............................................................................................................................................................................ 15 Designations and Descriptions............................................................................................................................................... 16 Physical Dynamics................................................................................................................................................................. 17 Synchrotron Radiation ........................................................................................................................................................... 18 Radio Lobes ........................................................................................................................................................................... 18 Summary of the Various Waveband Contributions................................................................................................................ 18 Summary of the Various Class Types .................................................................................................................................... 20 Concluding Remarks.............................................................................................................................................................. 21 Appendix.................................................................................................................................................................................... 23 A. The various Cambridge Catalogues................................................................................................................................. 23 B. Solution to the Relativistic Doppler Effect...................................................................................................................... 26 C. Fwd: From Graeme White ............................................................................................................................................... 28 D. Excerpt from Original Paper published by Hewish, Bell, et al, 1968 .............................................................................. 29 References.................................................................................................................................................................................. 30 1. Carroll & Ostlie; An Introduction to Modern Astrophysics, 2nd edition; 2007................................................................ 30 2. Unsold & Baschek; The New Cosmos, 5th edition, 2005................................................................................................. 30 3. Freedman & Kaufmann, Universe, Stars and Galaxies, 3rd edition, 2008........................................................................ 30 4. J. Craig Wheeler, Cosmic Catastrophes, 2nd edition, 2007 .............................................................................................. 30 5. Ryle, M.; Smith, F. G.; Elsmore, B, A preliminary survey of the radio stars in the Northern Hemisphere, MNRAS, Vol. 110, p.508, 1950..................................................................................................................................................................... 30 6. 3C RR Online Reference page: http://3crr.extragalactic.info, databased and compendium of sources: http://3crr.extragalactic.info/cgi/database .............................................................................................................................. 30 7. P. Veron, Ph.D, Paris Observatory; The Revised 3C (3CR) catalogue of Radio Sources, ESO Messenger #7, December 1976........................................................................................................................................................................................ 30 8. Long, R. J., Haseler, J. B., & Elsmore, B.; A Survey of Radio Sources At 408 Mc-s-1; Monthly Notices of the Royal Astronomical Society, Vol. 125, p.313 .................................................................................................................................. 30 9. M.S. Longair and Lilly, S.J.; Identifications and spectra of extragalactic radio sources, Journal of Astrophysics and Astronomy, Volume 5, Number 4; December, 1984.............................................................................................................. 30 10. McGilchrist, M. M.; Baldwin, J. E.; Riley, J. M.; Titterington, D. J.; Waldram, E. M.; Warner, P. J.; The 7c Survey of Radio Sources at 151-MHz - Two Regions Centred at Ra: 10H28M Dec: 41DEG and Ra: 06H28M Dec: 45DEG; R.A.S. MONTHLY NOTICES V.246, NO. 1/SEP1, P. 110, 1990 ................................................................................................... 30 11. Thorne, Kip S.; Black Holes & Time Warps: Einstein’s Outrageous Legacy; 1994 ....................................................... 30 12. Smith, Robert C.; Observational Astrophysics; 1995 ...................................................................................................... 30 13. http://isdc.unige.ch/3c273................................................................................................................................................ 30 T. Madigan Page 2 Quasars and their Nature A Modern Analysis 14. Harrison, E., ApJ, 403:28-31, 1993 January 20; The Redshift-Distance and Velocity-Distance Laws; (http://adsabs.harvard.edu/abs/1993ApJ...403...28H) ...........................................................................................................
Recommended publications
  • Black Hole Spin and Accretion Disk Magnetic Field Strength Estimates
    Draft version October 10, 2019 Typeset using LATEX default style in AASTeX62 Black Hole Spin and Accretion Disk Magnetic Field Strength Estimates for more than 750 AGN and Multiple GBH Ruth A. Daly1,2 — 1Penn State University, Berks Campus, Reading, PA 19608, USA 2Center for Computational Astrophysics, Flatiron Institute, 162 5th Avenue, New York, NY 10010, USA (Received October 10, 2019) Submitted to ApJ ABSTRACT Black hole systems, comprised of a black hole, accretion disk, and collimated outflow are studied here. Three AGN samples including 753 AGN, and 102 measurements of 4 GBH are studied. Applying the theoretical considerations described by Daly (2016), general expressions for the black hole spin function and accretion disk magnetic field strength are presented and applied to obtain the black hole spin function, spin, and accretion disk magnetic field strength in dimensionless and physical units for each source. Relatively high spin values are obtained; spin functions indicate typical spin values of about (0.6 - 1) for the sources. The distribution of accretion disk magnetic field strengths for the three AGN samples are quite broad and have mean values of about 104 G, while those for individual GBH have mean values of about 108 G. Good agreement is found between spin values obtained here and published values obtained with well-established methods; comparisons for 1 GBH and 6 AGN indicate that similar spin values are obtained with independent methods. Black hole spin and disk magnetic field strength demographics are obtained and indicate that black hole spin functions and spins are similar for all of the source types studied including GBH and different categories of AGN.
    [Show full text]
  • University of Southampton Research Repository Eprints Soton
    University of Southampton Research Repository ePrints Soton Copyright © and Moral Rights for this thesis are retained by the author and/or other copyright owners. A copy can be downloaded for personal non-commercial research or study, without prior permission or charge. This thesis cannot be reproduced or quoted extensively from without first obtaining permission in writing from the copyright holder/s. The content must not be changed in any way or sold commercially in any format or medium without the formal permission of the copyright holders. When referring to this work, full bibliographic details including the author, title, awarding institution and date of the thesis must be given e.g. AUTHOR (year of submission) "Full thesis title", University of Southampton, name of the University School or Department, PhD Thesis, pagination http://eprints.soton.ac.uk UNIVERSITY OF SOUTHAMPTON The epoch and environmental dependence of radio-loud active galaxy feedback by Judith Ineson Thesis for the degree of Doctor of Philosophy in the FACULTY OF PHYSICAL SCIENCES AND ENGINEERING Department of Physics and Astronomy June 2016 UNIVERSITY OF SOUTHAMPTON ABSTRACT FACULTY OF PHYSICAL SCIENCES AND ENGINEERING Department of Physics and Astronomy Doctor of Philosophy THE EPOCH AND ENVIRONMENTAL DEPENDENCE OF RADIO-LOUD ACTIVE GALAXY FEEDBACK by Judith Ineson This thesis contains the first systematic X-ray investigation of the relationships between the properties of different types of radio-loud AGN and their large-scale environments, using samples at two distinct redshifts to isolate the effects of evolution. I used X-ray ob- servations of the galaxy clusters hosting the radio galaxies to characterise the properties of the environments and compared them with the low-frequency radio properties of the AGN.
    [Show full text]
  • Structure in Radio Galaxies
    Atxention Microfiche User, The original document from which this microfiche was made was found to contain some imperfection or imperfections that reduce full comprehension of some of the text despite the good technical quality of the microfiche itself. The imperfections may "be: — missing or illegible pages/figures — wrong pagination — poor overall printing quality, etc. We normally refuse to microfiche such a document and request a replacement document (or pages) from the National INIS Centre concerned. However, our experience shows that many months pass before such documents are replaced. Sometimes the Centre is not able to supply a "better copy or, in some cases, the pages that were supposed to be missing correspond to a wrong pagination only. We feel that it is better to proceed with distributing the microfiche made of these documents than to withhold them till the imperfections are removed. If the removals are subsequestly made then replacement microfiche can be issued. In line with this approach then, our specific practice for microfiching documents with imperfections is as follows: i. A microfiche of an imperfect document will be marked with a special symbol (black circle) on the left of the title. This symbol will appear on all masters and copies of the document (1st fiche and trailer fiches) even if the imperfection is on one fiche of the report only. 2» If imperfection is not too general the reason will be specified on a sheet such as this, in the space below. 3» The microfiche will be considered as temporary, but sold at the normal price. Replacements, if they can be issued, will be available for purchase at the regular price.
    [Show full text]
  • Search for HI Emission from Superdisk Candidates Associated with Radio
    Search for H i emission from superdisk candidates associated with radio galaxies Abhijeet Anand1, Nirupam Roy2 and Gopal-Krishna3;4;? 1 Max-Planck-Institut fur¨ Astrophysik, Karl-Schwarzschild-Str. 1, D-85741 Garching, Germany; [email protected] 2 Department of Physics, Indian Institute of Science, Bangalore - 560012, India 3 Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital - 263129, India 4 Max-Planck-Institut fur¨ Radioastronomie, Auf dem Hugel¨ 69, 53121 Bonn, Germany Abstract Giant gaseous layers (termed ”superdisk”) have been hypothesized in the past to account for the strip-like radio emission gap (or straight-edged central brightness depres- sion) observed between the twin radio lobes, in over a dozen relatively nearby powerful Fanaroff-Riley Class II radio galaxies. They could also provide a plausible alternative ex- planation for a range of observations. Although a number of explanations have been pro- posed for the origin of the superdisks, little is known about their material content. Some X-ray observations of superdisk candidates indicate the presence of hot gas, but a cool dusty medium also seems to be common in them. If they are made of entirely or partly neutral gas, it may be directly detectable and we report here a first attempt to detect/image any neutral hydrogen gas present in the superdisks that are inferred to be present in four nearby radio galaxies. We have not found a positive H i signal in any of the four sources, resulting in tight upper limits on the H i number density in the postulated superdisks, es- timated directly from the central rms noise values of the final radio continuum subtracted image.
    [Show full text]
  • Low-Frequency Study of Two Giant Radio Galaxies: 3C 35 and 3C 223
    A&A 515, A50 (2010) Astronomy DOI: 10.1051/0004-6361/200913837 & c ESO 2010 Astrophysics Low-frequency study of two giant radio galaxies: 3C 35 and 3C 223 E. Orrù1,2, M. Murgia3,4, L. Feretti4,F.Govoni3, G. Giovannini4,5,W.Lane6, N. Kassim6, and R. Paladino1 1 Institute of Astro- and Particle Physics, University of Innsbruck, Technikerstrasse 25/8, 6020 Innsbruck, Austria e-mail: [email protected] 2 Radboud University Nijmegen, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands 3 INAF – Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Strada 54, 09012 Capoterra (CA), Italy 4 INAF – Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy 5 Dipartimento di Astronomia Università degli Studi di Bologna, via Ranzani 1, 40127 Bologna, Italy 6 Naval Research Laboratory, Code 7213, Washington DC 20375-5320, USA Received 9 December 2009 / Accepted 26 February 2010 ABSTRACT Aims. Radio galaxies with a projected linear size ∼>1 Mpc are classified as giant radio sources. According to the current interpretation these are old sources which have evolved in a low-density ambient medium. Because radiative losses are negligible at low frequency, extending spectral aging studies in this frequency range will allow us to determine the zero-age electron spectrum injected and then to improve the estimate of the synchrotron age of the source. Methods. We present Very Large Array images at 74 MHz and 327 MHz of two giant radio sources: 3C 35 and 3C 223. We performed a spectral study using 74, 327, 608 and 1400 GHz images. The spectral shape is estimated in different positions along the source.
    [Show full text]
  • Information Bulletin on Variable Stars
    COMMISSIONS AND OF THE I A U INFORMATION BULLETIN ON VARIABLE STARS Nos April November EDITORS L SZABADOS K OLAH TECHNICAL EDITOR A HOLL TYPESETTING MB POCS ADMINISTRATION Zs KOVARI EDITORIAL BOARD E Budding HW Duerb eck EF Guinan P Harmanec chair D Kurtz KC Leung C Maceroni NN Samus advisor C Sterken advisor H BUDAPEST XI I Box HUNGARY URL httpwwwkonkolyhuIBVSIBVShtml HU ISSN 2 IBVS 4701 { 4800 COPYRIGHT NOTICE IBVS is published on b ehalf of the th and nd Commissions of the IAU by the Konkoly Observatory Budap est Hungary Individual issues could b e downloaded for scientic and educational purp oses free of charge Bibliographic information of the recent issues could b e entered to indexing sys tems No IBVS issues may b e stored in a public retrieval system in any form or by any means electronic or otherwise without the prior written p ermission of the publishers Prior written p ermission of the publishers is required for entering IBVS issues to an electronic indexing or bibliographic system to o IBVS 4701 { 4800 3 CONTENTS WOLFGANG MOSCHNER ENRIQUE GARCIAMELENDO GSC A New Variable in the Field of V Cassiop eiae :::::::::: JM GOMEZFORRELLAD E GARCIAMELENDO J GUARROFLO J NOMENTORRES J VIDALSAINZ Observations of Selected HIPPARCOS Variables ::::::::::::::::::::::::::: JM GOMEZFORRELLAD HD a New Low Amplitude Variable Star :::::::::::::::::::::::::: ME VAN DEN ANCKER AW VOLP MR PEREZ D DE WINTER NearIR Photometry and Optical Sp ectroscopy of the Herbig Ae Star AB Au rigae :::::::::::::::::::::::::::::::::::::::::::::::::::
    [Show full text]
  • Cambridge:" 'Assac Setts 0213S
    , _;, 2 y'2 j,_'m.... ;PACE ASTR_I_H_SICS RESEARCH PROGRAM _:..:!_!; OF ................QUASAR CONTINUUM NASA Grant NAGW-2201 - Fina_eport N )2_2 Period 1 Ju!y)9_9_0_t__hrough 31 December 1997 PrelJai_ed-_0r: Aeronauhcs ce Administration WasI_n C 20546 Sm_thsoman _st_tutmn Astrophys_servatory Cambridge:"_'assac setts 0213S -2 :;: Th"n-eSmithsonia_AstrophysicaI Observatory is. a__mber pf the for Astrophysics :r for this grant is Darrell E. New, Code SZE, NASA Headquarters, 20546 _ .......:__.::_:_:z_z:................. qP _ .... _ _ , --LT_ The grant "The Evolution of the Quasar Continuum" resulted in over 53 published ref- ereed papers and conference proceedings. The more significant of these papers are listed below, and abstracts are attached. The papers address a wide range of issues involving the evolution of quasars, their elec- tromagnetic emissions, and their environment, from nearby low luminosity Seyfert galaxies to quasars at the highest redshifts. Primarily observational in content the work nonetheless included theoretical studies of quasar accretion disks that attempt to explain the observed time variability of quasars, and the overall 'demographics' of the quasar population. The work carried out under this grant has laid a strong foundation for ongoing and future research with AXAF, HST and other new facilities. X-ray Spectral Survey of WGACAT Quasars I: Spectral Evolution & Low Energy Cut-Offs (F. Fiore, M. Elvis, P. Giommi, and P. Padovani), Ap.J., 492, in press (Jan 1, 1998). X-ray Spectral Survey of WGACAT Quasars II: Optical and Radio Properties of Quasars with Low Energy X-ray Cut-Offs (M. Elvis, F. Fiore, P. Giommi, and P.
    [Show full text]
  • Arxiv:2004.06540V2 [Astro-Ph.SR] 30 Apr 2020 2
    The Astronomy and Astrophysics Review manuscript No. (will be inserted by the editor) Observations of galactic and extragalactic novae Massimo Della Valle and Luca Izzo Received: date / Accepted: date Abstract The recent GAIA DR2 measurements of distances to galactic novae have allowed to re-analyse some properties of nova populations in the Milky Way and in external galaxies on new and more solid empirical bases. In some cases we have been able to confirm results previously obtained, such as the concept of nova populations into two classes of objects, that is disk and bulge novae and their link with the Tololo spectroscopic classification in Fe II and He/N novae. The recent and robust estimates of nova rates in the Magellanic Clouds galaxies provided by the OGLE team have confirmed the dependence of the normalized nova rate (i.e., the nova rate per unit of luminosity of the host galaxy) with the colors and/or class of luminosity of the parent galaxies. The nova rates in the Milky Way and in external galaxies have been collected from literature and critically discussed. They are the necessary ingredient to asses the contribution of novae to the nucleosynthesis of the respective host galaxies, particularly to explain the origin of the overabundance of lithium observed in young stellar populations. A direct comparison between distances obtained via GAIA DR2 and Maximum Magnitude vs. Rate of Decline (MMRD) relation- ship points out that the MMRD can provide distances with an uncertainty better than 30%. Multiwavelength observations of novae along the whole elec- tromagnetic spectrum, from radio to gamma-rays, have revealed that novae undergo a complex evolution characterized by several emission phases and a non-spherical geometry for the nova ejecta.
    [Show full text]
  • Transition from Star Formation to Quiescence in Galaxies with SITELLE Observations of Andromeda
    Barthélémy Launet Transition from star formation to quiescence in galaxies with SITELLE observations of Andromeda. New analysis of the planetary nebulae population. Master Thesis Supervision Prof. Dr. Marcella Carollo Prof. Dr. Françoise Combes Dr. Anne-Laure Melchior March 2018 Contents Abstract iii 1 Introduction 1 1.1 Motivation . .1 1.2 Andromeda as a local testbed . .2 1.3 Planetary Nebulae . .2 1.4 Outline of the thesis . .3 2 Observations and Data reduction 5 2.1 SITELLE instrument . .5 2.1.1 Configuration . .5 2.1.2 Technical specificities . .5 2.1.3 Data Reduction Pipeline . .6 2.2 Observations of the central field of Andromeda . .7 2.3 Data Calibration . .8 2.3.1 Astrometric calibration . .8 2.3.2 Wavelength calibration . 10 2.3.3 Flux calibration . 13 3 Analysis 19 3.1 Source detection in the SN2 cube . 19 3.1.1 Creation of a detection map . 19 3.1.2 Detection algorithm . 25 3.1.3 Spectra extraction and fit of the emission lines . 27 3.2 Source matching in SN3 . 30 3.3 Aperture-Loss Correction . 32 3.4 Comparison with previous catalogs . 39 3.4.1 Comparison with Merrett et al. (2006) . 39 3.4.2 Comparison with Martin et al. (2018) . 40 3.5 Separating extended sources . 43 3.6 Limit of detection . 43 4 Results 45 4.1 Diagnostic Diagrams . 45 4.1.1 SMB diagram . 45 4.1.2 [OIII]-Hα emission-line space . 48 4.1.3 BPT Diagram . 48 4.2 Planetary Nebulae Luminosity Function . 54 i 4.2.1 Completeness limit .
    [Show full text]
  • 2007 Astronomy Magazine Index
    2007 Astronomy magazine index Subject Karin cluster, 10:32–37 observing, 4:62–65 new class of, 12:29 black holes spin affected by light, 9:24 artist's renderings of, 4:58–59 Numbers astrolabes, 8:27 dark energy, 8:66 2MASS1207-3932 (brown dwarf Astrolight AZ6 and AZ8 reflector effect on space, 11:63 star), 9:24 telescopes, 11:70–73 evaporation of, 9:74–75 3C 273 (quasar), 10:87 astronauts event horizon, 4:26–31 18 Scorpii (star), 8:27 Aldrin, Buzz, 2:25 falling into, 2:75 1987A (supernova), 10:26–31 Armstrong, Neil, 3:23 growth of, 11:26 2003 EL61 (Kuiper Belt object), charges of drunkenness, 11:21 measuring, 9:26 9:23 astronomers, educational newly discovered, 3:25, 7:26 2006gy (supernova), 9:24 requirements for, 3:68–69 outburst from, 5:25 2007 NS2 (Trojan asteroid), 11:21 Astronomical Society of the Pacific possibly seeding life, 8:27 2007ck (supernova), 10:21 (ASP), 8:68–70 rogue, 9:24 2007co (supernova), 10:21 astronomy rotation of, 11:28–33 amateurs' favorite observation super-massive, 4:19, 20 A spots, 12:96–97 blazars, 3:26–31 AAS (American Astronomical avoiding common frustrations, Blue Flash (NGC 6905) (planetary Society), 7:25 5:70–71 nebula), 11:87 accretion, 3:32–37 basic terminology, 4:66–67 Blue Moon, 5:69 active galactic nuclei (AGNs), online discussion groups, 3:70– bolides (fireballs), 7:12 3:26–31, 12:24 72 brown dwarf stars, 9:24 Adler Planetarium and Astronomy top ten stories of 2006, 1:34–43 Bullet Cluster (1E 0657-56), 1:24 Museum (Chicago), 7:74–77 visual perception, 6:14 Advanced Camera for Surveys, Astronomy.com,
    [Show full text]
  • The Chandra View of Nearby X-Shaped Radio Galaxies
    The Astrophysical Journal, 710:1205–1227, 2010 February 20 doi:10.1088/0004-637X/710/2/1205 C 2010. The American Astronomical Society. All rights reserved. Printed in the U.S.A. THE CHANDRA VIEW OF NEARBY X-SHAPED RADIO GALAXIES Edmund J. Hodges-Kluck1, Christopher S. Reynolds1, Chi C. Cheung2,3, and M. Coleman Miller1 1 Department of Astronomy, University of Maryland, College Park, MD 20742-2421, USA 2 NASA Goddard Space Flight Center, Code 661, Greenbelt, MD 20771, USA Received 2009 July 7; accepted 2009 December 16; published 2010 January 28 ABSTRACT We present new and archival Chandra X-ray Observatory observations of X-shaped radio galaxies (XRGs) within z ∼ 0.1 alongside a comparison sample of normal double-lobed FR I and II radio galaxies. By fitting elliptical distributions to the observed diffuse hot X-ray emitting atmospheres (either the interstellar or intragroup medium), we find that the ellipticity and the position angle of the hot gas follow that of the stellar light distribution for radio galaxy hosts in general. Moreover, compared to the control sample, we find a strong tendency for X-shaped morphology to be associated with wings directed along the minor axis of the hot gas distribution. Taken at face value, this result favors the hydrodynamic backflow models for the formation of XRGs which naturally explain the geometry; the merger-induced rapid reorientation models make no obvious prediction about orientation. Key words: galaxies: active – intergalactic medium Online-only material: color figures 1. INTRODUCTION Antenna; because fossil lobes will quickly decay due to adiabatic expansion, an XRG would be a sign of a recent merger.
    [Show full text]
  • Download This Article in PDF Format
    A&A 425, 825–836 (2004) Astronomy DOI: 10.1051/0004-6361:200400023 & c ESO 2004 Astrophysics Optical nuclei of radio-loud AGN and the Fanaroff-Riley divide P. Kharb and P. Shastri Indian Institute of Astrophysics, Koramangala, Bangalore – 560 034, India e-mail: [email protected] Received 17 June 2003 / Accepted 15 June 2004 Abstract. We investigate the nature of the point-like optical nuclei that have been found in the centres of the host galaxies of a majority of radio galaxies by the Hubble Space Telescope. We examine the evidence that these optical nuclei are relativistically beamed, and look for differences in the behaviour of the nuclei found in radio galaxies of the two Fanaroff-Riley types. We also attempt to relate this behaviour to the properties of the optical nuclei in their highly beamed counterparts (the BL Lac objects and radio-loud quasars) as hypothesized by the simple Unified Scheme. Simple model-fitting of the data suggests that the emission may be coming from a non-thermal relativistic jet. It is also suggestive that the contribution from an accretion disk is not significant for the FRI objects and for the narrow-line radio galaxies of FRII type, while it may be significant for the Broad-line objects, and consistent with the idea that the FRII optical nuclei seem to suffer from extinction due to an obscuring torus while the FRI optical nuclei do not. These results are broadly in agreement with the Unified Scheme for radio-loud AGNs. Key words. galaxies: active – BL Lacertae objects: general – galaxies: nuclei – quasars: general 1.
    [Show full text]