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Radio Mode Feedback in Giant Elliptical Galaxies Paul Nulsen (CfA), Christine Jones (CfA), William Forman (CfA), Eugene Churazov (MPA), Laurence David.

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Presentation on theme: "Radio Mode Feedback in Giant Elliptical Galaxies Paul Nulsen (CfA), Christine Jones (CfA), William Forman (CfA), Eugene Churazov (MPA), Laurence David."— Presentation transcript:

1 Radio Mode Feedback in Giant Elliptical Galaxies Paul Nulsen (CfA), Christine Jones (CfA), William Forman (CfA), Eugene Churazov (MPA), Laurence David (CfA), Brian McNamara (Waterloo), Steven Murray (CfA)

2 AGN Outbursts in Giant Ellipticals In an AGN outburst, jets inflate radio lobes displace surrounding gas drive shocks In a hot atmosphere lobes make X-ray “cavities” shocks cause breaks in surface brightness Review McNamara & Nulsen (2007) M84 (Finoguenov & Jones 2001) NGC 4552 (Machacek et al. 2006) NGC 4636 (Jones et al. 2002) Outbursts are seen in the hot (X-ray emitting) atmospheres of galaxy clusters galaxy groups isolated ellipticals 7/9/08Radio Galaxies in the Chandra Era

3 Range of Scales NGC 5813, z = , 1 arcmin ≈ 9.3 kpc Dominant member of a subgroup of the NGC 5846 group (Mahdavi et al. 2005). Most energetic outburst known is MS (McNamara et al. 2005) Centre of 4.5 keV cluster (Gitti et al. 2007) z = 0.216, 1 arcmin ≈ 210 kpc 7/9/08Radio Galaxies in the Chandra Era

4 Impact of AGN Outbursts Outbursts occur in systems with short central cooling times (t cool < H 0 -1, often < 10 9 yr). Average outburst powers in clusters similar to radiative losses (Bîrzan et al. 2004; Dunn & Fabian 2006; Rafferty et al. 2006). -> AGN feedback (radio mode, eg Croton et al. 2006) can prevent cooling and star formation. But some systems with short cooling times show no signs of an outburst. Also shock formation requires intermittency. -> Outbursts are intermittent Require an unbiased, complete sample to measure mean power, intermittency, etc. 7/9/08Radio Galaxies in the Chandra Era Rafferty et al. (2006)

5 Nearby Elliptical Galaxy Sample Jones et al. (in prep.) have collected X-ray data for a sample of ≈ 160 nearby elliptical galaxies (expanded from Beuing et al. 1999; O’Sullivan et al. 2001). After removal of point sources and unresolved emission from X-ray binaries, 109 show X-ray emission from diffuse hot gas. Of these, 27 have signs of AGN outbursts (cavities and/or shocks) - underestimated. AGN jet powers determined using methods of Bîrzan et al. (2004), Rafferty et al. (2006): energy input per cavity taken as pV 3 age estimates: t sonic, t buoy, t refill 7/9/08Radio Galaxies in the Chandra Era

6 AGN Heating vs Cooling Cavity power vs cooling power for elliptical galaxies with outbursts. t sonic – blue, t buoy – red, t refill – green Cooling power is L X (r < r cool ), where t cool (r cool ) = 7.7 Gyr (look back time to z = 1). Dashed lines show P cav = L X (r cool ), for energy inputs of 1pV, 4pV and 16pV per cavity (top to bottom). …cavities detected in only 25% of galaxies with hot gas. 7/9/08Radio Galaxies in the Chandra Era

7 AGN Heating vs Cooling Cavity power vs cooling power for elliptical galaxies with outbursts. t sonic – blue, t buoy – red, t refill – green Cooling power is L X (r < r cool ), where t cool (r cool ) = 7.7 Gyr (look back time to z = 1). Dashed lines show P cav = L X (r cool ), for energy inputs of 1pV, 4pV and 16pV per cavity (top to bottom). …cavities detected in only 25% of galaxies with hot gas. Correct UGC 408 by setting distance from center to semimajor axis of cavity. 7/9/08Radio Galaxies in the Chandra Era

8 AGN Heating vs Cooling Cavity power vs cooling power for elliptical galaxies with outbursts. t sonic – blue, t buoy – red, t refill – green Cooling power is L X (r < r cool ), where t cool (r cool ) = 7.7 Gyr (look back time to z = 1). Dashed lines show P cav = L X (r cool ), for energy inputs of 1pV, 4pV and 16pV per cavity (top to bottom). …cavities detected in only 25% of galaxies with hot gas. AGN dominates Cooling dominates 7/9/08Radio Galaxies in the Chandra Era

9 Global Energetics Intermittent – compare powers for whole sample (109 galaxies with hot gas): Total cavity powers (1pV per cavity): P sonic = 2.6×10 43 erg s -1, P buoy = 2.9×10 43 erg s -1, P refill = 1.5×10 43 erg s -1. Total cooling power for 109 galaxies: L X,cool = 8.7×10 43 erg s -1. Ratio of totals, / = 3.3, 3.0, 5.6 (sonic, buoy, refill). Enthalpy of cavity dominated by relativistic gas is 4pV. Add extra energy in shocks, sound, particles, etc. Cavities are under-counted. -> Very plausibly: time averaged AGN power can balance cooling in these galaxies, so radio mode feedback can limit star formation in nearby gE sample 7/9/08Radio Galaxies in the Chandra Era

10 Energetics vs Size Order by cooling power, L X (r cool ). Ratio of cumulative cooling power (L X,cool ) to cumulative cavity power (P cav ) plotted vs L X,cool : For energy of 4pV per cavity, mean AGN power matches or exceeds cooling power over full range. Noisy (intermittent) but broadly consistent with a constant ratio, independent of cooling power (size). 4 7/9/08Radio Galaxies in the Chandra Era

11 Duty Cycle vs Size 7/9/08Radio Galaxies in the Chandra Era Cumulative fraction of gE’s with outbursts vs cooling power. For 107 galaxies, 27/107 ≈ Cumulative values consistent with fixed fraction of 0.25 for whole sample. Marked range is ±1σ for binomial samples with p = 0.25.

12 Conclusions AGN outbursts can occur in any elliptical galaxy at the center of a hot atmosphere Outbursts are intermittent, on ~1/4 of the time, with average power close to cooling power Radio mode AGN feedback can limit cooling and star formation in these galaxies, as well as in clusters 7/9/08Radio Galaxies in the Chandra Era


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