Fifty Years of Quasars From Early Observations and Ideas to Future R
The 50th anniversary of the discovery of quasars in 1963 presents an interesting opportunity to ask questions about the current state of quasar research. Formatted as a series of interviews with noted researchers in the field, each of them asked to addres
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Quasars Classes and Their Relationships Contributions by Mauro D’Onofrio, Paola Marziani, Jack W. Sulentic, Deborah Dultzin, Yuri Efimov, Martin Gaskell, Marianne Vestergaard, Damien Hutsem´ekers, Alberto Franceschini, Ari Laor, Dirk Grupe, ˜ Garc´ıa Lorenzo, Evencio Mediavilla, Todd Boroson, Sebastian Lipari, Begona Mike Eracleous, Isabel Marquez-Perez, Elmar K¨ording, and Heino Falcke
M. D’Onofrio Dipartimento di Astronomia, Universit`a degli Studi di Padova, Vicolo Osservatorio 3, I35122 Padova, Italy e-mail: [email protected] P. Marziani INAF, Osservatorio Astronomico di Padova, Vicolo Osservatorio 5, IT35122 Padova, Italy e-mail: [email protected] J.W. Sulentic () Instituto de Astrof´ısica de Andaluc´ıa (CSIC), Granada, Spain e-mail: [email protected] D. Dultzin Instituto de Astronomia, Universidad Nacional Autonoma de Mexico (UNAM), Apt.do postal 70-264, Mexico, D.F., Mexico e-mail: [email protected] Y. Efimov Crimean Astrophysical Observatory, 98409, Nauchny, Crimea, Ukraine e-mail: [email protected] M. Gaskell Departamento de F´ısica y Astronom´ıa, Facultad de Ciencias, Universidad de Valpara´ıso, Av. Gran Breta˜na 1111, Valpara´ıso, Chile e-mail: [email protected] M. Vestergaard The Dark Cosmology Centre, The Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen 0, Denmark Steward Observatory and Department of Astronomy, University of Arizona, 933 N. Cherry Avenue, Tucson 85721, Arizona, USA e-mail: [email protected] D. Hutsem´ekers F.R.S. - FNRS, Institute of Astrophysics and Geophysics, University of Li`ege, All´ee du six aoˆut 17, B5c, B-4000, Li`ege, Belgium email: [email protected] A. Franceschini Dipartimento di Astronomia, Universit`a degli Studi di Padova, Vicolo Osservatorio 3, I35122 Padova, Italy e-mail: [email protected] M. D’Onofrio, P. Marziani, J.W. Sulentic (eds.), Fifty Years of Quasars, Astrophysics and Space Science Library 386, DOI 10.1007/978-3-642-27564-7 4, © Springer-Verlag Berlin Heidelberg 2012
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Most of the questions in this chapter deal with sources that do not show the “classical” broad emission-line spectrum that characterizes the majority of known AGNs at high and low redshift. If that majority represents a “parent population” of AGNs, is the apparent absence of broad lines a result of obscuration, orientation, or different physical conditions? Can all of the subclasses be unified under the AGN umbrella? With the unification scheme set in place and assumed to be fundamentally correct, there are at least four overarching questions: do all type-2 AGNs possess an obscured broad-line region? Or how can we distinguishing type-2 AGNs without a broad-line region if they exist? Where is the low end of quasar activity? The
A. Laor Technion - Israel Institute of Technology, Physics Department, Technion City, Haifa 32000, Israel e-mail: [email protected] D. Grupe The Pennsylvania State University, 525 Davey Lab., University Park, PA 16082, U
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