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Radiative Efficiency and Content of Extragalactic
Radio Sources
Laura Bîrzan
Collaborators: Brian McNamara (U. Waterloo), Paul Nulsen (CfA), Chris Carilli (NRAO), Mike Wise (U. Amsterdam)
Radiative Efficiency / Scaling Relations
An understanding of how scales with is important in order to estimate AGN feedback across a wide range of environments and masses (e.g., Magliocchetti & Bruggen 2007, Best et al. 2007).Our first attempt (Bîrzan et al. 2004):
but with large scatter.Using the 5 GHz core radio luminosity, Merloni & Heinz (2007) find a tighter scaling relation.How does the lobe radio luminosity scale with the mechanical power?€
Lradiototal ∝ Pcav
1/ 2,
€
Lradio
€
Pcav
Radio and X-ray: Complementary Data
X-ray data (Rafferty et al. 2006):
Measure p,V Ages: tcav (tbuoy,trefill,tcs )
€
E cav = pV +1
γ − 1pV , γ =
4
3
€
Pcav = E cav tcav
Radio data:
Synchrotron break frequency is indicative of the age
€
Lradio 10 MHz10000 MHz, ν break
lobes
R
ab
330 MHz Radio Image
MS 0735.6+7421
MS 0735.6+7421
X-ray Image
spectrum at t1
spectrum at 5t1
€
Iν (t) spectrum at t0
The Sample
24 systems from Chandra Data Archive which show X-ray cavities (Bîrzan et al. 2004, Rafferty et al. 2006).Redshift range: 0.0035 < z < 0.545
Radio sources associated with the central galaxy.VLA observations at 330 MHz, 1.4 GHz, 4.5 GHz and 8.5 GHz.
Particle Content and Aging
Is the wide range in k due to aging? Young sources tend
to have smaller k. But, range in age
can not fully account for the range in k.
Entrainment of heavy particles may play a role.
older younger
€
tsyn ∝ν break−1/ 2
radio-filled cavityghost cavity
€
pX−ray = ppart + pB
→ k (≡ Epart / Ee)
Radiative Efficiencies
(lower limit – shocks not
included)Most objects: a~100 (Nipoti & Binney 2005, Bicknell et al. 1997, De Young 1993).
Ghost cavities generally require higher a.
Scaling relations:Scatter = 0.65 dex Scatter = 0.31 dex for radio filled only
€
Pcav ≈ aLradio, where a =1−1000's
€
radio-filled cavityghost cavity
€
Pcav = 4 pV tcav
Lradio = Llobesbolometric (no core)
Aging and Radiative Efficiencies
No clear trend is present.However, there is a tendency for younger objects to be radiatively efficient.
Aging contributes to scatter in the radiative-efficiencies plot, but can not account for all of it.
The scatter may also be due to entrainment, which would increase k and reduce Lrad.
radio-filled cavityghost cavity
older younger
Scaling Relations: Pcav and Lradio
Including the dependence of the radiative efficiencies on C:
Scatter is reduced by ≈50% (to 0.33 dex)However, need radio data at several frequencies
radio-filled cavityghost cavity
€
logPcav = (0.53± 0.07)logLradio
−(0.74 ± 0.16)logν C
+(2.15 ± 0.09)
Conclusions
The radiative efficiency is around 1%, but can be much lower.
Scatter about scaling relation is large.Aging and entrainment may be important contributors.
By accounting for differences in age (break frequency), scatter is reduced by ≈ 50%.k (=Epart/Ee) ranges between a few and a few thousands (for equipartion assumptions).
Again, aging and entrainment may contribute to large range in k.
Radio Spectra
325 and 1400 MHz Scaling Relations
•P327: Scatter = 0.75 dex
• P1400: Scatter = 0.83 dex