The luminosity-dependent evolution of the radio luminosity function Emma Rigby University of Nottingham Collaborators: P. Best, M. Brookes, J. Dunlop, J. Peacock, L. Ker, H. Rottgering, J. Wall Emma Rigby University of Nottingham Collaborators: P. Best, M. Brookes, J. Dunlop, J. Peacock, L. Ker, H. Rottgering, J. Wall

Why study radio galaxy evolution? Important for galaxy evolution models via feedback Important for galaxy evolution models via feedback Radio-loud AGN powered by most massive black holes so provide information on upper end of black hole mass function Radio-loud AGN powered by most massive black holes so provide information on upper end of black hole mass function Important for galaxy evolution models via feedback Important for galaxy evolution models via feedback Radio-loud AGN powered by most massive black holes so provide information on upper end of black hole mass function Radio-loud AGN powered by most massive black holes so provide information on upper end of black hole mass function Model of a radio-loud AGN (Urry & Padovani)

The evolving radio luminosity function (RLF) Comoving space density of radio galaxies increases to z ~2 (Dunlop & Peacock 1990), with indications of a decline at higher redshift Comoving space density of radio galaxies increases to z ~2 (Dunlop & Peacock 1990), with indications of a decline at higher redshift Previous work lacked depth & volume necessary to probe high-z behavior Previous work lacked depth & volume necessary to probe high-z behavior Motivated development of CENSORS - a faint radio source sample (S 1.4GHz > 7.2 mJy) Motivated development of CENSORS - a faint radio source sample (S 1.4GHz > 7.2 mJy) 73% spectroscopically complete (Brookes et al. 2008) 73% spectroscopically complete (Brookes et al. 2008) Investigate using a grid-based modelling technique with no assumptions made about the RLF behavior Investigate using a grid-based modelling technique with no assumptions made about the RLF behavior Comoving space density of radio galaxies increases to z ~2 (Dunlop & Peacock 1990), with indications of a decline at higher redshift Comoving space density of radio galaxies increases to z ~2 (Dunlop & Peacock 1990), with indications of a decline at higher redshift Previous work lacked depth & volume necessary to probe high-z behavior Previous work lacked depth & volume necessary to probe high-z behavior Motivated development of CENSORS - a faint radio source sample (S 1.4GHz > 7.2 mJy) Motivated development of CENSORS - a faint radio source sample (S 1.4GHz > 7.2 mJy) 73% spectroscopically complete (Brookes et al. 2008) 73% spectroscopically complete (Brookes et al. 2008) Investigate using a grid-based modelling technique with no assumptions made about the RLF behavior Investigate using a grid-based modelling technique with no assumptions made about the RLF behavior

RLF Modelling: input data 5 input radio source samples 5 input radio source samples Wall & Peacock 1985, Wall & Peacock 1985, Parkes selected regions, (Downes et al 1986), Parkes selected regions, (Downes et al 1986), CENSORS (Best et al. 2003) CENSORS (Best et al. 2003) Hercules, (Waddington et al. 2001) Hercules, (Waddington et al. 2001) VLA-COSMOS, (Smolcic et al. 2008) VLA-COSMOS, (Smolcic et al. 2008) Local radio luminosity functions covering ~20 < Log P 1.4GHz < 27 Local radio luminosity functions covering ~20 < Log P 1.4GHz < 27 (Best et al., 2010; Sadler et al., 2002; Mauch et al., 2007) Integrated source counts covering 0.05 mJy to 94 Jy (Bondi et al. 2008; Seymour et al. 2004; Windhorst et al. 1984; White et al. 1997; Kellermann & Wall 1987) Integrated source counts covering 0.05 mJy to 94 Jy (Bondi et al. 2008; Seymour et al. 2004; Windhorst et al. 1984; White et al. 1997; Kellermann & Wall 1987) 5 input radio source samples 5 input radio source samples Wall & Peacock 1985, Wall & Peacock 1985, Parkes selected regions, (Downes et al 1986), Parkes selected regions, (Downes et al 1986), CENSORS (Best et al. 2003) CENSORS (Best et al. 2003) Hercules, (Waddington et al. 2001) Hercules, (Waddington et al. 2001) VLA-COSMOS, (Smolcic et al. 2008) VLA-COSMOS, (Smolcic et al. 2008) Local radio luminosity functions covering ~20 < Log P 1.4GHz < 27 Local radio luminosity functions covering ~20 < Log P 1.4GHz < 27 (Best et al., 2010; Sadler et al., 2002; Mauch et al., 2007) Integrated source counts covering 0.05 mJy to 94 Jy (Bondi et al. 2008; Seymour et al. 2004; Windhorst et al. 1984; White et al. 1997; Kellermann & Wall 1987) Integrated source counts covering 0.05 mJy to 94 Jy (Bondi et al. 2008; Seymour et al. 2004; Windhorst et al. 1984; White et al. 1997; Kellermann & Wall 1987) The radio-power - redshift plane covered by the 5 samples

RLF Modelling: input data 5 input radio source samples 5 input radio source samples Wall & Peacock 1985, Wall & Peacock 1985, Parkes selected regions, (Downes et al 1986), Parkes selected regions, (Downes et al 1986), CENSORS (Best et al. 2003) CENSORS (Best et al. 2003) Hercules, (Waddington et al. 2001) Hercules, (Waddington et al. 2001) VLA-COSMOS, (Smolcic et al. 2008) VLA-COSMOS, (Smolcic et al. 2008) Local radio luminosity functions covering ~20 < Log P 1.4GHz < 27 Local radio luminosity functions covering ~20 < Log P 1.4GHz < 27 (Best et al., 2010; Sadler et al., 2002; Mauch et al., 2007) Integrated source counts covering 0.05 mJy to 94 Jy (Bondi et al. 2008; Seymour et al. 2004; Windhorst et al. 1984; White et al. 1997; Kellermann & Wall 1987) Integrated source counts covering 0.05 mJy to 94 Jy (Bondi et al. 2008; Seymour et al. 2004; Windhorst et al. 1984; White et al. 1997; Kellermann & Wall 1987) 5 input radio source samples 5 input radio source samples Wall & Peacock 1985, Wall & Peacock 1985, Parkes selected regions, (Downes et al 1986), Parkes selected regions, (Downes et al 1986), CENSORS (Best et al. 2003) CENSORS (Best et al. 2003) Hercules, (Waddington et al. 2001) Hercules, (Waddington et al. 2001) VLA-COSMOS, (Smolcic et al. 2008) VLA-COSMOS, (Smolcic et al. 2008) Local radio luminosity functions covering ~20 < Log P 1.4GHz < 27 Local radio luminosity functions covering ~20 < Log P 1.4GHz < 27 (Best et al., 2010; Sadler et al., 2002; Mauch et al., 2007) Integrated source counts covering 0.05 mJy to 94 Jy (Bondi et al. 2008; Seymour et al. 2004; Windhorst et al. 1984; White et al. 1997; Kellermann & Wall 1987) Integrated source counts covering 0.05 mJy to 94 Jy (Bondi et al. 2008; Seymour et al. 2004; Windhorst et al. 1984; White et al. 1997; Kellermann & Wall 1987) The CENSORS redshift distribution

Modelling Technique Redshift Radio Power Space densities RLF Cosmic evolution

Modelling Technique 3 input radio-luminosity - redshift (P,z) density grids: 21 points in log P (19.25 < Log P < 29.25) and 8 points in z (0.1 < z < 6) Steep spectrum grid Flat spectrum grid Starforming grid Created by evolving the local starforming galaxy luminosity function Taken as the median of the evolutionary models of Dunlop & Peacock 1990 Starting estimate created by evolving the local AGN RLF by (1+z) 3

Modelling Technique 3 input radio-luminosity - redshift (P,z) density grids Steep spectrum grid Flat spectrum grid Starforming grid Integrate to form 3 flux- density - redshift (S,z) grids containing source numbers Compare to input datasets Amoeba minimisation - varies steep grid only

Modelling Technique 3 input radio-luminosity - redshift (P,z) density grids Steep spectrum grid Flat spectrum grid Starforming grid Integrate to form 3 flux- density - redshift (S,z) grids containing source numbers Compare to input datasets Amoeba minimisation - varies steep grid only Assuming  = log(1+z) for steep;  = 0.8 for starforming &  = 0 for flat grids Marginalised errors calculated from a Hessian matrix

Results: dataset comparison Local radio luminosity function Radio source samples Integrated source counts Model good fit to input data

Results: model luminosity functions Dashed line: median of Dunlop & Peacock (1990) results

Results: model luminosity functions

Blue: lack of coverage in local RLF Green: Incomplete coverage of radio power - redshift plane

Robustness testing Randomly moving the redshift limits to higher values Varying the spectral index used to calculate the steep source number grid Redshift cutoffs still present

The high redshift cutoff High redshift cutoffs seen across the radio power range High redshift cutoffs seen across the radio power range Cutoffs still present when model parameters are varied Cutoffs still present when model parameters are varied Need ~5 extra sources in CENSORS sample to reduce the cutoff strength to <3 for 27 < log P < 28 Need ~5 extra sources in CENSORS sample to reduce the cutoff strength to <3 for 27 < log P < 28 Position of cutoff appears to be radio luminosity - dependent Position of cutoff appears to be radio luminosity - dependent High redshift cutoffs seen across the radio power range High redshift cutoffs seen across the radio power range Cutoffs still present when model parameters are varied Cutoffs still present when model parameters are varied Need ~5 extra sources in CENSORS sample to reduce the cutoff strength to <3 for 27 < log P < 28 Need ~5 extra sources in CENSORS sample to reduce the cutoff strength to <3 for 27 < log P < 28 Position of cutoff appears to be radio luminosity - dependent Position of cutoff appears to be radio luminosity - dependent

The future… samples Larger radio source samples will mean RLF evolution of different populations can be studied individually e.g. FRI vs FRII or Low vs High excitation sources samples Larger radio source samples will mean RLF evolution of different populations can be studied individually e.g. FRI vs FRII or Low vs High excitation sources Predictions for the LOFAR-deep survey [ dashed line - FRIs, solid line - starforming galaxies, dot-dashed line - radio quiet quasars, dotted line - FRIIs] FRIs FRIIs Starforming galaxies

The future… Luminosity dependence seen for cutoff needs to be incorporated into SKA population models Red dashed line computed from S 3 SKADS simulations (Wilman et al. 2008)

ConclusionsConclusions Using our new grid-based modelling have found clear high-redshift cutoff in the RLF Using our new grid-based modelling have found clear high-redshift cutoff in the RLF Cutoff appears to move to higher redshift at higher radio power Cutoff appears to move to higher redshift at higher radio power Results still limited by uncertain redshifts & small radio samples Results still limited by uncertain redshifts & small radio samples Using our new grid-based modelling have found clear high-redshift cutoff in the RLF Using our new grid-based modelling have found clear high-redshift cutoff in the RLF Cutoff appears to move to higher redshift at higher radio power Cutoff appears to move to higher redshift at higher radio power Results still limited by uncertain redshifts & small radio samples Results still limited by uncertain redshifts & small radio samples