Journal Article

Quasar radio-loudness and the elliptical core problem

Timothy S. Hamilton

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 407, issue 4, pages 2393-2398
Published in print October 2010 | ISSN: 0035-8711
Published online July 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.17067.x
Quasar radio-loudness and the elliptical core problem

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The dichotomy between radio-loud and radio-quiet quasi-stellar objects (QSOs) is not simply one of host morphology. While spiral galaxies almost exclusively host radio-quiet QSOs, ellipticals can host either radio-louds or radio-quiets. We find that a combination of accretion rate and host scale determines which type of QSO a given elliptical galaxy will host. QSOs with high X-ray luminosities (above 1044.5 erg s−1 at 0.5 keV) are mostly radio-loud. But those with low luminosities divide fairly neatly in size (measured by the half-light radius, re). Those larger than about 10 kpc are radio-loud, while smaller ones are radio-quiet. It has recently been found that core and coreless ellipticals are also divided near this limit. This implies that for low-luminosity QSOs, radio-louds are found in core ellipticals, while radio-quiets are in coreless ellipticals and spirals. This segregation also shows up strongly for low-redshift objects and, in general, there is a loss over time of coreless, radio-loud QSOs. Since the presence or absence of a core may be tied to the galactic merger history, we have an evolutionary explanation for the differences between radio-loud and radio-quiet QSOs.

Keywords: galaxies: active; galaxies: evolution; quasars: general; galaxies: structure

Journal Article.  4057 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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