Radio galaxies in the 2SLAQ Luminous Red Galaxy Survey: I. The evolution of low-power radio galaxies to z~0.7

Monthly Notices of the Royal Astronomical Society (Impact Factor: 5.52). 12/2006; DOI: 10.1111/j.1365-2966.2007.12231.x
Source: arXiv

ABSTRACT We have combined optical data from the 2dF-SDSS Luminous Red Galaxy and QSO (2SLAQ) redshift survey with radio measurements from the 1.4 GHz VLA FIRST and NVSS surveys to identify a volume-limited sample of 391 radio galaxies at redshift 0.4<z<0.7. By determining an accurate radio luminosity function for early-type galaxies in this redshift range, we can investigate the cosmic evolution of the radio-galaxy population over a wide range in radio luminosity. The low-power radio galaxies in our LRG sample (those with 1.4 GHz radio luminosities in the range 10^{24} to 10^{25} W/Hz, corresponding to FR I radio galaxies in the local universe) undergo significant cosmic evolution over the redshift range 0<z<0.7, consistent with pure luminosity evolution of the form (1+z)^k where k=2.0+/-0.3. Our results appear to rule out (at the 6-7 sigma level) models in which low-power radio galaxies undergo no cosmic evolution. The most powerful radio galaxies in our sample (with radio luminosities above 10^{26} W/Hz) may undergo more rapid evolution over the same redshift range. The evolution seen in the low-power radio-galaxy population implies that the total energy input into massive early-type galaxies from AGN heating increases with redshift, and was roughly 50% higher at z~0.55 (the median redshift of the 2SLAQ LRG sample) than in the local universe. Comment: 18 pages, 15 figures, one 10-page data table in landscape format. Replaced with final version accepted for publication in MNRAS

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Massive black holes (BHs) are at once exotic and yet ubiquitous, residing at the centers of massive galaxies in the local Universe. Recent years have seen remarkable advances in our understanding of how these BHs form and grow over cosmic time, during which they are revealed as Active Galactic Nuclei (AGN). However, despite decades of research, we still lack a coherent picture of the physical drivers of BH growth, the connection between the growth of BHs and their host galaxies, the role of large-scale environment on the fueling of BHs, and the impact of BH-driven outflows on the growth of galaxies. In this paper we review our progress in addressing these key issues, motivated by the science presented at the “What drives the growth of black holes?” workshop held at Durham on 26–29th July 2010, and discuss how these questions may be tackled with current and future facilities.
    New Astronomy Reviews 06/2012; 56(4):93–121. · 1.82 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We examine the hypothesis that mergers and close encounters between galaxies can fuel active galactic nuclei (AGNs) by increasing the rate at which gas accretes toward the central black hole. We compare the clustering of galaxies around radio-loud AGNs with the clustering around a population of radio-quiet galaxies with similar masses, colors, and luminosities. Our catalog contains 2178 elliptical radio galaxies with flux densities greater than 2.8 mJy at 1.4 GHz from the Six Degree Field Galaxy Survey. We find tentative evidence that radio AGNs with more than 200 times the median radio power have, on average, more close (r < 160 kpc) companions than their radio-quiet counterparts, suggesting that mergers play a role in forming the most powerful radio galaxies. For ellipticals of fixed stellar mass, the radio power is neither a function of large-scale environment nor halo mass, consistent with the radio powers of ellipticals varying by orders of magnitude over billions of years.
    The Astrophysical Journal 07/2013; 772(1):64. · 6.73 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The 140 deg^2 2SLAQ survey carried out at the Anglo-Australian Telescope in 2003-5 obtained redshifts and spectra for more than 11,000 luminous red galaxies (LRGs) in the redshift range z=0.4 to 0.7. By combining the 2SLAQ data with wide-field radio continuum surveys of the same area, we have measured the first accurate radio luminosity function for massive galaxies at z˜0.55. Our results imply that the total energy input into massive early-type galaxies from `radio-mode' AGN heating increases with redshift, and was at least 50% higher at z˜0.55 than in the local universe. With the exception of the most powerful radio sources (L_{1.4}>10^{26} W/Hz), we find no significant difference in the stellar populations of 2SLAQ LRGs with and without a radio-loud AGN. This is consistent with a picture in which radio-loud AGN occur episodically in all massive early-type galaxies.


Available from