Cosmic evolution of radio selected active galactic nuclei in the COSMOS field

📝 Abstract

We explore the cosmic evolution of radio AGN with low radio powers (L_1.4GHz < 5\times10^25 W/Hz) out to z=1.3 using to-date the largest sample of 600 low luminosity radio AGN at intermediate redshift drawn from the VLA-COSMOS survey. We derive the radio luminosity function for these AGN, and its evolution with cosmic time assuming two extreme cases: i) pure luminosity and ii) pure density evolution. The former and latter yield L_\propto(1+z)^(0.8+/-0.1), and Phi\propto (1+z)^(1.1+/-0.1), respectively, both implying a fairly modest change in properties of low radio-power AGN since z=1.3. We show that this is in stark contrast with the evolution of powerful (L_1.4GHz > 5\times10^25 W/Hz) radio AGN over the same cosmic time interval, constrained using the 3CRR, 6CE, and 7CRS radio surveys by Willott et al. (2001). We demonstrate that this can be explained through differences in black hole fueling and triggering mechanisms, and a dichotomy in host galaxy properties of weak and powerful AGN. Our findings suggest that high and low radio-power AGN activity is triggered in different stages during the formation of massive red galaxies. We show that weak radio AGN occur in the most massive galaxies already at z1, and they may significantly contribute to the heating of their surrounding medium and thus inhibit gas accretion onto their host galaxies, as recently suggested for the `radio mode’ in cosmological models.

💡 Analysis

We explore the cosmic evolution of radio AGN with low radio powers (L_1.4GHz < 5\times10^25 W/Hz) out to z=1.3 using to-date the largest sample of 600 low luminosity radio AGN at intermediate redshift drawn from the VLA-COSMOS survey. We derive the radio luminosity function for these AGN, and its evolution with cosmic time assuming two extreme cases: i) pure luminosity and ii) pure density evolution. The former and latter yield L_\propto(1+z)^(0.8+/-0.1), and Phi\propto (1+z)^(1.1+/-0.1), respectively, both implying a fairly modest change in properties of low radio-power AGN since z=1.3. We show that this is in stark contrast with the evolution of powerful (L_1.4GHz > 5\times10^25 W/Hz) radio AGN over the same cosmic time interval, constrained using the 3CRR, 6CE, and 7CRS radio surveys by Willott et al. (2001). We demonstrate that this can be explained through differences in black hole fueling and triggering mechanisms, and a dichotomy in host galaxy properties of weak and powerful AGN. Our findings suggest that high and low radio-power AGN activity is triggered in different stages during the formation of massive red galaxies. We show that weak radio AGN occur in the most massive galaxies already at z1, and they may significantly contribute to the heating of their surrounding medium and thus inhibit gas accretion onto their host galaxies, as recently suggested for the `radio mode’ in cosmological models.

📄 Content

arXiv:0901.3372v1 [astro-ph.CO] 21 Jan 2009 Preprint typeset using LATEX style emulateapj v. 08/22/09 COSMIC EVOLUTION OF RADIO SELECTED ACTIVE GALACTIC NUCLEI IN THE COSMOS FIELD0 V. Smolˇci´c1, G. Zamorani2, E. Schinnerer3, S. Bardelli2, M. Bondi4, L. Bˆirzan5,6, C. L. Carilli7, P. Ciliegi2, O. Ilbert8, A. M. Koekemoer9, A. Merloni10,11 T. Paglione12,13, M. Salvato1, M. Scodeggio14, N. Scoville1 ABSTRACT We explore the cosmic evolution of radio AGN with low radio powers (L1.4GHz ≲5 × 1025 W Hz−1) out to z = 1.3 using to-date the largest sample of ∼600 low luminosity radio AGN at intermediate redshift drawn from the VLA-COSMOS survey. We derive the radio luminosity function for these AGN, and its evolution with cosmic time assuming two extreme cases: i) pure luminosity and ii) pure density evolution. The former and latter yield L∗∝(1+z)0.8±0.1, and Φ∗∝(1+z)1.1±0.1, respectively, both implying a fairly modest change in properties of low radio-power AGN since z = 1.3. We show that this is in stark contrast with the evolution of powerful (L1.4GHz > 5 × 1025 W Hz−1) radio AGN over the same cosmic time interval, constrained using the 3CRR, 6CE, and 7CRS radio surveys by Willott et al. (2001). We demonstrate that this can be explained through differences in black hole fueling and triggering mechanisms, and a dichotomy in host galaxy properties of weak and powerful AGN. Our findings suggest that high and low radio-power AGN activity is triggered in different stages during the formation of massive red galaxies. We show that weak radio AGN occur in the most massive galaxies already at z ∼1, and they may significantly contribute to the heating of their surrounding medium and thus inhibit gas accretion onto their host galaxies, as recently suggested for the ‘radio mode’ in cosmological models. Subject headings: galaxies: fundamental parameters – galaxies: active, evolution – cosmology: obser- vations – radio continuum: galaxies

1. INTRODUCTION 1.1. AGN feedback: The impact of radio sources on galaxy formation Radio activity from active galactic nuclei (AGN) has recently been invoked in cosmological models as a signifi- cant ingredient in the process of galaxy formation (‘AGN feedback’). Given that, in the past, cosmological models led to a systematic over-prediction of the high-mass end of the galaxy stellar mass function (e.g. White & Rees 0 Based on observations with the National Radio Astronomy Ob- servatory which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. 1 California Institute of Technology, MC 105-24, 1200 East Cal- ifornia Boulevard, Pasadena, CA 91125 2 INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, 40127, Bologna, Italy 3 Max Planck Institut f¨ur Astronomie, K¨onigstuhl 17, Heidel- berg, D-69117, Germany 4 INAF - Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy 5 Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 6 Department of Physics and Astronomy, Ohio University, Clip- pinger Laboratories, Athens, OH 45701 7 National Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801-0387 8 Institute for Astronomy, 2680 Woodlawn Dr., University of Hawaii, Honolulu, Hawaii, 96822 9 Space Telescope Science Institute, 3700 San Martin Drive, Bal- timore, MD 21218 10 Excellence Cluster Universe, Technische Universitt Mnchen, Boltzmannstr. 2, D-85748, Garching, Germany 11 Max-Planck-Institut f¨ur Extraterrestrische Physik, Giessen- bachstr., D-85741 Garching, Germany 12 York College, City University of New York, 94-20 Guy R. Brewer Boulevard, Jamaica, NY 11451 13 American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024 14 IASF Milano-INAF, Via Bassini 15, I-20133, Milan, Italy 1978; White & Frenk 1991), the implementation of gas heating through energetic radio outflows – the ‘radio’ mode16 – managed to reproduce well many observed galaxy properties (e.g. the galaxies’ stellar mass func- tion, color bimodality; Croton et al. 2006, Bower et al. 2006). The particular choice of a ‘radio mode’ as the rel- evant heating mechanism has been motivated by many observational results verifying the interplay between the emission of radio galaxies in galaxy clusters, and the clus- ter’s hot X-ray emitting gas on large-scales (e.g. Fabian et al. 2003, Forman et al. 2005). In the centers of galaxy clusters the radiative cooling time of the intra-cluster medium (ICM) is shorter than the age of the cluster. Thus, the central ICM is expected to be significantly colder compared to outskirt-regions (such clusters are referred to as ‘cooling flow clusters’). However, generally the expected cool X-ray phases are not observed, and this is known as the ‘cooling flow prob- lem’. The most likely solution to this problem is thought to be radio galaxies as it is usually observed that the syn- chrotron plasma ejected by their radio jets inflates bub- bles in the hot X-ray

This content is AI-processed based on ArXiv data.