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