Quasar radio-loudness and the elliptical core problem
Abstract
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 1044.5ergs-1 at 0.5keV) 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 10kpc 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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- October 2010
- DOI:
- 10.1111/j.1365-2966.2010.17067.x
- arXiv:
- arXiv:1006.0128
- Bibcode:
- 2010MNRAS.407.2393H
- Keywords:
-
- galaxies: active;
- galaxies: evolution;
- quasars: general;
- galaxies: structure;
- Astrophysics - Cosmology and Extragalactic Astrophysics
- E-Print:
- 8 pages, 4 figures. To be published in MNRAS