Evidence for a maximum jet efficiency for the most powerful radio galaxies

Author： Fernandes C. A. C. Jarvis M. J. Rawlings S. Martínez-Sansigre A. Hatziminaoglou E. Lacy M. Page M. J. Stevens J. A. Vardoulaki E.

Publisher： Oxford University Press

ISSN： 0035-8711

Source： Monthly Notices of the Royal Astronomical Society, Vol.411, Iss.3, 2011-03, pp. : 1909-1916

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Abstract

ABSTRACTWe use new mid-infrared (mid-IR) photometry from the Spitzer Space Telescope to study the relations between low-frequency radio luminosity density , mid-IR ( 12 μ m rest frame) luminosity and optical emission-line ([O ii]) luminosity L_{]O ii]} , for a complete sample of z∼ 1 radio galaxies from the 3CRR, 6CE, 6C*, 7CRS and TOOT00 surveys. The narrow redshift span of our sample ( 0.9 < z < 1.1 ) means that it is unbiased to evolutionary effects. We find evidence that these three quantities are positively correlated. The scaling between and L_{[O ii]} is similar to that seen in other active galactic nuclei samples, consistent with both and L_{[O ii]} tracing accretion rate. We show that the positive correlation between and implies that there is a genuine lack of objects with low values of at high values of . Given that traces accretion rate, while traces jet power, this can be understood in terms of a minimum accretion rate being necessary to produce a given jet power. This implies that there is a maximum efficiency with which accreted energy can be chanelled into jet power and this efficiency is of the order of unity.